JPH07310601A - Carburetor - Google Patents

Abstract

PURPOSE:To unite fuel systems into a single system constitution of which is simplified and to perform the stable feed of fuel in a proper air-fuel ratio by a method wherein throttle parts are respectively arranged in an air introduction passage and a fuel passage and the sectional area of the throttle part on the air introduction passage side is increased to a value higher than that of the throttle part in the fuel passage. CONSTITUTION:When a negative pressure in an intake pipe is not so high, an amount of air passing through an intake throttle valve 5 proportions a fuel feed amount metered by a fuel metering part 20 and an air-fuel ratio is kept at a constant value. Further, though, when a negative pressure in the intake pipe is high, a flow rate of intake air flowing through the intake throttle part 5 is reduced to a low value owing to the influence of compressibility, a total sum of the areas of the throttle parts 18, 18b, and 18c of an air introduction passage 16 is higher than the area of the throttle part 19 of a fuel passage 17, whereby a pressure difference exerted on the throttle part 19 of a fuel passage 17 is increased and an amount of air flowing through the throttle part 19 of the fuel passage 17 is decreased. In this case, a pressure difference is decreased by an amount equivalent to a decrease in a flow rate of air and a negative pressure in a control pressure chamber 12 is decreased, and a flow rate of fuel is also decreased to correct an air-fuel ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor for controlling the air-fuel ratio and the amount of air-fuel mixture supplied to an engine.

[0002]

2. Description of the Related Art Generally, in a carburetor, a change in intake pipe negative pressure during idling operation to high speed operation is large, so that it is difficult to integrate the fuel system into one system. Need to be provided. When the intake pipe negative pressure becomes large, the intake air flow rate becomes small due to the influence of the compressibility of the air, and the air-fuel ratio becomes rich. On the contrary, when the intake pipe negative pressure becomes small, the air-fuel ratio becomes thin and the fuel becomes Since there is a shortage, it is necessary to additionally provide a fuel control system such as a fuel increase system.

However, if the carburetor is made multi-system like this, the air-fuel ratio control becomes complicated, and the ride comfort such as the occurrence of breathing due to the poor connection of each fuel system at the time of vehicle start and sudden acceleration is caused. Defect occurs.

Further, a jet needle interlocking with a throttle valve is inserted into the needle jet, and the area of the annular gap formed between the jet portion of the needle jet and the needle is changed to supply the supplied fuel from idling operation to fully open operation. Although there is a carburetor controlled by, it is difficult to make the air-fuel ratio constant over the entire operating range.

It is an object of the present invention to provide a carburetor which can make a fuel system into a single system having a simple structure and can supply a stable fuel at an appropriate air-fuel ratio.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a vaporizer having a jet needle that moves in a needle jet in conjunction with a throttle valve to control a fuel supply amount, and seals an upper opening of the needle jet. Then
A control pressure chamber surrounded by the seal portion and the metering jet of the needle jet is provided, and an air introduction passage and a fuel passage communicating with the downstream of the throttle valve are connected to the control pressure chamber, and the air introduction passage and the fuel passage are further connected. Are each provided with a throttle portion, and the cross-sectional area of the throttle portion on the air introduction passage side is made larger than the cross-sectional area of the throttle portion of the fuel passage.

[0007]

According to the above structure, the negative pressure of the control pressure chamber is determined by the area ratio between the throttle portion of the air introduction passage and the throttle portion of the fuel passage. When the intake pipe negative pressure is not so large, the control pressure is reduced. The negative pressure in the chamber is proportional to the negative pressure in the intake pipe. Further, the shape of the jet needle is formed so that the ratio of the area of the intake throttle portion and the area of the fuel metering portion is constant. Therefore, when the intake pipe negative pressure is not so large, the amount of air passing through the intake throttle portion is proportional to the fuel supply amount measured by the fuel metering portion, and the air-fuel ratio becomes constant.

When the negative pressure in the intake pipe is large, the flow rate of intake air flowing through the intake throttle portion is small due to the compressibility, but the cross-sectional area of the throttle portion of the air introduction passage is equal to the cross-sectional area of the throttle portion of the fuel passage. Therefore, the pressure difference applied to the throttle portion of the fuel passage becomes large, and the flow rate of the air flowing through the throttle portion of the fuel passage becomes small. At this time, the same air flow rate flows through the throttle portion of the air introduction passage, but the pressure difference applied to this throttle portion is not so large that the air flow rate is affected by the compressibility. As a result, the negative pressure in the control pressure chamber becomes smaller. Therefore, the flow rate of the fuel flowing from the fuel throttle portion into the control pressure chamber becomes small and is corrected so that the air-fuel ratio does not become rich.

Further, since the fuel passage is opened on the downstream side of the throttle valve, a stable negative pressure, which is small in fluctuation due to manufacturing variations of the throttle valve and fluctuation due to backlash, acts on the pressure chamber to cause fluctuation in fuel supply amount. It can be kept small.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an embodiment of a vaporizer of the present invention,
FIG. 2 is an explanatory view of the main part of the present invention.

A piston valve type carburetor 1 is provided with an intake passage 3 penetrating through a body 2 thereof, and a piston valve 4 is provided in the intake passage 3 so as to be movable back and forth, and an effective diameter of the intake passage 3 is provided. Is controlled and the piston valve 4
An intake throttle portion 5 is formed between the front end surface of the and the inner wall of the intake passage 3. A jet needle 6 is attached to the tip surface of the piston valve 4.

On the other hand, in the carburetor body 2, a needle jet 7 is arranged in the axial direction of the jet needle 6 so that the jet needle 6 can enter, and a measuring jet 8 is provided in the needle jet 7. . The upstream side of the metering jet 8 is connected to the float chamber 10 via a fuel pipe 9 extending downward, and the fuel in the float chamber 10 is sucked into the needle jet 7 via this fuel pipe 9. A seal portion 11 having an outer diameter substantially equal to the inner diameter of the needle jet 7 is provided on the upper portion of the jet needle 6, and the seal portion 11 is slidably inserted into the needle jet 7. The upper end opening of the needle jet 7 is constantly sealed by the seal portion 11. A control pressure chamber 12 is formed between the seal portion 11 and the measuring jet 8, and the control pressure chamber 12 is formed.
Is communicated with an annular bleed chamber 15 formed on the outer periphery of the needle jet 7 through a plurality of small holes 14 formed in the needle jet 7. The bleed chamber 15 is connected to an air introduction passage 16 which communicates the other with the atmosphere or an air cleaner (not shown) and a fuel passage 17 which communicates the other with an intake passage 3 downstream of the piston valve 4.
6 and the fuel passage 17 have throttle portions 18 and 19 respectively.
Is provided. On the other hand, the tip side of the jet needle 6 extends through the inside of the metering jet 8, and the fuel is a fuel metering section 20 formed between the jet needle 6 and the metering jet 8.
And then sent to the control pressure chamber 12.

A slow fuel passage 22 communicating with the float chamber 10 through a slow jet 21 is connected to the air introduction passage 16 at the other end thereof, and a slow air passage 23 for introducing low speed air into the slow fuel passage 22. Are connected. The slow air passage 23 is the air introduction passage 16
It is also possible to connect to.

Further, the carburetor body 2 is provided with a starting intake passage 24 having one end communicating with the intake passage 3 upstream of the piston valve 4 or the atmosphere and the other end communicating with the intake passage 3 downstream of the piston valve 4. A fuel passage 25 for starting, the other end of which communicates with the float chamber 10, is opened in the intake passage 24 for starting. The starting intake passage 24 and the starting fuel passage 25 are opened and closed by a starting valve 26.
When the valve is opened, the fuel flowing from the float chamber 10 is mixed with the air flowing in the starting intake passage 24, and the air-fuel mixture suitable for starting is supplied to the engine.

In this embodiment, an example in which an air regulating valve is provided in the air introducing passage 16 will be described. That is, in this embodiment, the air inlet of the air introduction passage 16 is branched into a plurality of branches, the power valve 35 and the correction valve 36 are provided at the respective inlets 31 and 32, and the idle inlet is provided at the inlet 30 of the slow air passage 23. A valve 34 is provided. The power valve 35 reduces the amount of air supplied from the inflow port 31 to the air introduction passage 16 at the time of acceleration and high load operation to increase the air-fuel ratio, and the correction valve 36 obtains an optimum air-fuel ratio in the entire operation range. The amount of air supplied from the inflow port 32 to the air introduction passage 16 is adjusted so as to control the negative pressure amount of the control pressure chamber 12. Further, the idle valve 34 adjusts the amount of air supplied to the slow fuel passage 22. The idle valve 34, the power valve 35, and the correction valve 36 restrict the throttles 18a, 18b, 18 at the inlets 30, 31, 32 of the air introducing passage.
c is formed, and the sum of these throttles 18a, 18b, 18c becomes the throttle area of the air introduction passage 16 and constitutes the throttle portion 18.

The idle valve 34 is a screw type adjustment valve that is manually adjusted, and the power valve 35 is a diaphragm valve that operates by negative pressure in the intake pipe, and the negative pressure chamber 35b on the rear surface of the diaphragm 35a is connected to the negative pressure passage. By communicating with the intake passage 3 downstream of the throttle valve by 35c, the diaphragm 35a is moved according to the magnitude of the negative pressure of the intake pipe to increase or decrease the amount of air flowing in from the inflow port 31. Correction valve 3
6 is an electronic control unit 4 for inputting signals from an engine speed sensor 37, an oxygen concentration sensor 38 installed in an exhaust pipe (not shown), and an engine temperature sensor 39.
It is controlled by a stepping motor 41 driven by receiving a drive control signal output from 0.

The adjusting valves of the idle valve 34, the power valve 35, and the correction valve 36 need not be provided if the air-fuel ratio can be properly maintained without using them. Further, even when it is used, it is not necessary to use all the adjusting valves, and it is possible to use any combination such as the idle valve 34 and the power valve 35 and the idle valve 34 and the correction valve 36.

The operation of the above embodiment will be described below. According to the above configuration, the negative pressure of the control pressure chamber 12 is determined by the area ratio between the throttle portion 18 of the air introduction passage and the throttle portion 19 of the fuel passage, and when the intake pipe negative pressure is not so large, the control pressure is reduced. The negative pressure in the chamber 12 is proportional to the negative pressure in the intake pipe. Also,
The shape of the jet needle 6 is formed so that the ratio of the area of the intake throttle portion 5 to the area of the fuel metering portion 20 is constant. Therefore, when the intake pipe negative pressure is not so large, the amount of air passing through the intake throttle 5 is proportional to the amount of fuel supplied by the fuel metering unit 20, and the air-fuel ratio becomes constant.

When the negative pressure of the intake pipe is large, the flow rate of the intake air flowing through the intake throttle portion 5 is small due to the compressibility, but the area of the throttle portion 18 of the air introducing passage 16 is smaller than that of the fuel passage 1.
Since it is larger than the area of the throttle portion 19 of No. 7, the pressure difference applied to the throttle portion 19 of the fuel passage becomes large, and the flow rate of the air flowing through the throttle portion 19 of the fuel passage becomes small. At this time, the same air flow rate flows through the throttle portion 18 of the air introduction passage, but since the pressure difference applied to this throttle portion 18 is not so large that the air flow rate is affected by the compressibility, the air flow rate is reduced by a small amount. The difference becomes smaller and the negative pressure in the control pressure chamber 12 becomes smaller. Therefore, the flow rate of the fuel flowing into the control pressure chamber 12 from the fuel metering unit 20 becomes small and is corrected so that the air-fuel ratio does not become rich.

Further, the fuel passage 17 is connected to the throttle valve 4
Since the pressure chamber 12 is opened on the downstream side, a stable negative pressure, which is less affected by manufacturing variations of the throttle valve 4 and backlash, acts on the pressure chamber 12, and variations in the fuel supply amount can be suppressed.

Further, when it is necessary to correct the air-fuel ratio between the idling operation, the full-open operation and the high load operation, the air introducing passage 16 is provided with the adjusting valves 34, 35 and 36. This can be dealt with by automatically adjusting the inflowing air according to the operating state of the engine.

FIG. 2 shows an example in which the present invention is applied to a carburetor having a butterfly valve 45 as a throttle valve. The butterfly valve 45 and the jet needle 6 are linked by a conventionally known link or cam 46.

The seal portion 11 of the needle jet 7 may be formed by interposing a seal ring 48 made of rubber or resin between the jet needle 6 and the needle jet 7 as shown in FIG. Further, when the V-shaped seal ring 49 is provided on the needle jet 7 as shown in FIG. 4, the jet needle 6 does not need to have a special shape, and an ordinary one can be used, which is more practical.

[0024]

As described above in detail, according to the present invention, in the carburetor having the jet needle which moves in the needle jet in conjunction with the throttle valve and controls the fuel supply amount, the upper opening of the needle jet is provided. And a control control pressure chamber surrounded by the seal part and the jet part of the needle jet, and an air introduction passage and a fuel passage communicating with the downstream of the throttle valve are connected to this control pressure chamber, and further air introduction is performed. By providing throttles in the passage and the fuel passage, respectively, the fuel flow flowing out from the control pressure chamber to the intake passage downstream of the throttle valve is corrected according to the magnitude of the intake pipe negative pressure, so that the air-fuel ratio is always constant. Since it can be maintained, the fuel system can be controlled by one system, cost can be reduced, and breathing can be prevented when the vehicle starts or suddenly accelerates. Excessive operation of the engine is improved.

Further, since the opening of the fuel passage can be selected at an optimum position on the downstream side of the throttle valve, good drivability of the engine can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a vaporizer of the present invention.

FIG. 2 is a vertical sectional view showing another embodiment of the present invention.

FIG. 3 is an explanatory view of main parts showing another embodiment of the present invention.

FIG. 4 is an explanatory view of a main part showing another embodiment of the present invention.

[Explanation of symbols]

 3 Intake passage 6 Jet needle 7 Needle jet 12 Control pressure chamber 16 Air introduction passage 17 Fuel passage 18 Throttling portion 19 Throttling portion 20 Fuel metering portion 22 Slow fuel passage 23 Slow air passage 34 Idle valve 35 Power valve 36 Correction valve

Claims (4)

[Claims] 1. A carburetor having a jet needle which moves in a needle jet in conjunction with a throttle valve to control a fuel supply amount, wherein an upper opening of the needle jet is sealed, and the sealing portion and the needle jet are metered. A control control pressure chamber surrounded by a jet is provided, and an air introduction passage and a fuel passage communicating with the downstream of the throttle valve are connected to this control pressure chamber, and further, a throttle portion is provided in each of the air introduction passage and the fuel passage. A carburetor characterized in that the cross-sectional area of the throttle portion on the air introduction passage side is made larger than the cross-sectional area of the throttle portion of the fuel passage. 2. The carburetor according to claim 1, wherein the seal portion is formed by providing a large-diameter portion on the upper portion of the jet needle, the large-diameter portion having substantially the same diameter as the upper inner diameter of the needle jet. . 3. The carburetor according to claim 1, wherein the seal portion is formed of a seal ring provided between a jet needle and a needle jet. 4. An air adjusting valve for adjusting an inflowing air amount is provided in the air introducing passage.
Vaporizer described in.