JPS5996464A - Carburetor - Google Patents

Abstract

PURPOSE:To correct to make the air/fuel ratio rich by communicating the negative pressure lead-in path opening to a suction path at the upper straem than a throttle valve with an air bleed path while releasing a portion of bleed air to the suction path under heavy load high speed running. CONSTITUTION:Under heavy load high speed running where a throttle valve 7 will be high opening, secondary throttle valve 10 will open to inject fuel through secondary fuel nozzle 28 into small Venturi 9 in secondary suction path 3. Here negative pressure in large Venturi 4 in main suction path 2 is relatively high to flow a portion of air from an air bleed path 19 through negative pressure lead-in path 40 into large Venturi tube 4 thus to reduce the amount of air to be injected through an air jet 20 into an air bleed tube 12 and to increase the fuel injection by that amount to make rich. When providing an atmosphere responsive valve at the down stream from the coupling position of negative pressure lead-in path 40 and air bleed path 19, air-fuel ratio is prevented from going excessively rich.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carburetor, and in particular, a venturi and a throttle valve are disposed in the middle of an intake passage in order from upstream, and a fuel nozzle opened in the venturi is connected to a fuel chamber through an air bleed pipe. The present invention relates to a carburetor in which the air bleed pipe is communicated with the inlet portion of the intake passage through an air bleed passage.

In such a conventional carburetor, the air-fuel ratio characteristics of the air-fuel mixture are determined by selecting the shape of the bleed pipe, the position of the bleed hole, and the hole diameter. However, with such conventional methods, it is easy to change the slope of the air-fuel ratio characteristic, but it is difficult to change the slope of the air-fuel ratio characteristic at high loads and high speeds of internal combustion engines in which the throttle valve is opened at a high opening. It is difficult to correct the air-fuel ratio to a small value, that is, to reduce the fuel concentration of the air-fuel mixture only during operation.

The first object of the present invention is to solve such conventional technical problems, and to provide a carburetor that can increase the fuel concentration of the air-fuel mixture by reducing the amount of air bleed only during high-load, high-speed operation of an internal combustion engine. It is to provide.

As mentioned above, if the amount of air bleed is reduced during high load and high speed operation of the internal combustion engine, in places with low atmospheric pressure such as high altitudes, the fuel concentration will be higher than necessary during high load and high speed operation. There is a risk that it will become large.

Therefore, the second object of the present invention is to
An object of the present invention is to provide a carburetor that can appropriately correct the air-fuel ratio during high-load, high-speed operation of an internal combustion engine.

Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
First, in FIG. 1, this carburetor is a composite type carburetor, and a main intake passage 2 and a secondary intake passage 3 are installed in a carburetor body 1 in parallel. A large bench lily 4 is formed in the middle of the main intake passage 2, and a small bench lily 5 is disposed upstream of the large bench lily 4. Further, in the carburetor body 1, a choke valve 6 is pivotally supported on the upstream side of the small bench lily 5, and a throttle valve 7 is pivotally supported on the downstream side of the large bench lily 4. On the other hand, a large bench lily 8 is formed in the middle of the secondary intake passage 3, and a small bench lily 9 is disposed upstream of the large bench lily 8. Downstream of large bench lily 8,
A secondary throttle valve 10 is driven to open by a conventionally well-known negative pressure actuator (not shown) during predetermined high-load, high-speed operation of the engine.
is pivoted.

The main fuel nozzle 1 is installed in the small bench lily 5 in the main intake passage 2.
1 is open, and this main fuel nozzle 11 communicates with an annular chamber 13 surrounding an air bleed pipe 12 . The annular chamber 13 communicates with a fuel passage 15 via a main fuel jet 14.
The two fuel passages 15 communicate with the surface of a float chamber 17, which serves as a fuel chamber in which a float 16 is housed, below the fuel oil level. In addition, main fuel nozzle 1
1 has a needle-shaped fuel adjustment member 18 inserted therein for adjusting the amount of fuel jetted.

An air bleed passage 19 communicates with the air bleed pipe 12.
is formed, and this air bleed passage 19 is connected to the main intake passage 20.
The inlet portion, in the illustrated example, opens into the main intake path 2 at a location close to the choke valve 6 and downstream of the choke valve 6 when the valve 6 is closed. Also, in the middle of the air bleed passage 19, the air bleed pipe 1
An air generator 20 for regulating the amount of bleed air jetted into the air bleed pipe 12 is disposed near the air bleed pipe 12 . Further, an air jet 21 is arranged near the opening position of the air bleed passage 19 to the main intake passage 2 to limit the maximum amount of air flowing into the air bleed passage 19.

The fuel passage 15 also communicates via an auxiliary fuel jet 22 with an annular chamber 6-24 surrounding the air bleed pipe 23, which is connected to the large bench lily 4.
It communicates with a low-speed nozzle 25 that opens into the main intake path 2 near the throttle valve 7 on the downstream side. Inside the air bleed pipe 23, via an air jet 26 and an air bleed passage 27,
It communicates with the main intake path 2 on the upstream side of the small bench lily 5.

As for the secondary intake passage 3, similarly to the above-mentioned main intake passage 2, a secondary fuel nozzle 28 opens in the small bench lily 9, and this secondary fuel nozzle 28 communicates with an annular chamber 30 surrounding an air bleed pipe 29. It goes through. The annular chamber 30 also communicates with the bottom of the float chamber 11 via a fuel passage 31 and a secondary fuel jet 32. Further, the inside of the air bleed pipe 29 communicates with the upstream end of the secondary intake passage 3 via an air bleed passage 33 and a secondary air jet 34. Furthermore, a low-speed nozzle 3 is located near the throttle valve 10 downstream of the small bench lily 9 of the secondary intake path 3.
5 is open, and this low-velocity nozzle 35 communicates with the upstream end of the secondary intake passage 3 via a passage 36 and an air jet 31. An auxiliary fuel jet 38 is disposed facing the middle of this passage 36, and this auxiliary fuel jet 38 communicates with the surface of the fuel oil in the float chamber 1γ via a fuel passage 39.

In such a compound carburetor, according to the present invention, the main intake path 2 is opened at a portion of the main intake path 2 where negative pressure is generated during high-load and high-speed operation of the engine, that is, at a location upstream of the throttle valve 1. A pressure introduction path 4o is provided.

That is, in this embodiment, a negative pressure introduction path 40 is provided opening on the inner surface of the large bench lily 4, and this negative pressure introduction path 40 is connected to the air bleed passage 19 upstream of the air jet 20. Further, an air jet 41 that regulates the amount of negative pressure introduced from the main intake path 2 is arranged in the negative pressure introduction path 40 .

Next, the operation of this embodiment will be explained. During low load operation of the engine with a small opening degree of the throttle valve γ, the throttle valve 7 is opened, and air flows into the fuel in the annular chamber 13 from the bleed hole 42 of the air bleed pipe 12. be bred.

The emulsified fuel is then transferred to the main fuel nozzle 1.
1 into the small bench lily 5 to form an air-fuel mixture. In addition, when operating the engine at low load, the large bench lily 4
The negative pressure near the inner surface of is relatively small. Therefore, the negative pressure acting on the air bleed passage 19 from the negative pressure introduction passage 40 is extremely weak, and therefore the amount of air bleed through the air jet 20 is maintained at the same level as before, and a mixture of a predetermined air-fuel ratio is obtained. It will be done.

When the throttle valve T is opened to a high opening degree and the engine reaches a high-load, high-speed operating state, the secondary throttle valve 10 is opened, and accordingly, the secondary fuel nozzle 28 is opened to the small bench lily 9 of the secondary intake path 3. An air-fuel mixture is formed by ejecting the emulsified fuel inside. Therefore, the engine is supplied with air-fuel mixture from the main intake duct 2 and the 29-igneous air duct 3.

During such high-load, high-speed operation, the negative pressure near the inner surface of the large bench lily 4 in the main intake passage 2 becomes relatively large. Therefore, the negative pressure acts strongly on the air bleed passage 19 through the negative pressure introduction passage 40, and as a result, the air bleed passage 19
A part of the air flowing through the air 9 flows into the large bench lily 4 via the negative pressure introduction path 40, and the amount of bleed air injected into the air bleed pipe 12 through the air jet 20 is reduced. The amount of fuel ejected increases accordingly. Therefore, when the engine is operated under high load and at high speed, the fuel concentration of the air-fuel mixture is increased, that is, the air-fuel ratio is corrected to become lean.

Next, an embodiment of the second invention will be described. In FIG.
An atmospheric pressure responsive valve 44 is disposed downstream of the connection position 43 with the air jet 20 and upstream of the air jet 20. Note that the other configurations are the same as those of the embodiment shown in the first figure, and corresponding parts are given the same reference numerals.

The atmospheric pressure responsive valve 44 includes a casing 47 that forms a space 46 that communicates with the large package through a through hole 45, and an expandable bellows body 48 that is fixed to the inner surface of the casing 47 and is filled with a certain amount of gas in advance. and a valve stem 49 fixed to the bellows body 48 extending in the direction of expansion and contraction of the bellows body 48.
and a valve body 5 which is fixed to the valve stem 49 and determines the opening degree of the valve hole 50.
1. The space 46 and the air bleed passage 19 are sealed by a sealing member 52 that slides on the outer surface of the valve stem 49.

In such an atmospheric pressure responsive valve 44, when the atmospheric pressure decreases and the pressure in the space 46 decreases, the bellows body 48 operates until the internal pressure and the pressure in the space 46 are balanced.
The valve hole 50 expands, thereby increasing the opening degree of the valve hole 50. Therefore, the air jet 2 from the air jet passage 19
The amount of air bleed into the bleed pipe 12 through 0 becomes relatively large. Conversely, when the atmospheric pressure increases, the bellows body 48 contracts, the opening degree of the valve hole 50 becomes small, and the amount of air bleed from the air jet 20 into the bleed pipe 12 becomes relatively large.

Therefore, according to this embodiment, it is possible to prevent the air-fuel ratio from becoming unnecessarily small due to an excessive decrease in the amount of bleed air supplied when the internal combustion engine is operated at high load and high speed in places with low atmospheric pressure such as at high altitudes. Ru.

The present invention can be implemented not only in conjunction with a compound carburetor as in the embodiments described above, but also in connection with a carburetor having a single intake passage, and furthermore, in connection with a carburetor having a single venturi in the middle of the intake passage. It can also be implemented in relation to vessels.

As described above, according to the present invention, the air bleed passage is connected to the negative pressure introduction passage which opens to the intake passage on the upstream side of the throttle valve. is released into the intake passage through the negative pressure introduction path, and therefore, correction can be made to reduce the air-fuel ratio, that is, increase the fuel concentration, only during the high-load, high-speed operation.

Further, according to the second invention, an atmospheric pressure responsive valve is provided in the middle of the air bleed passage on the downstream side of the connection position with the negative pressure introduction passage, the opening degree of which increases as the atmospheric pressure decreases. Therefore, the fuel concentration of the air-fuel mixture is prevented from becoming richer than necessary when the internal combustion engine is operated under high load and at high speed when the atmospheric pressure decreases.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIG. 1 is a longitudinal sectional front view of one embodiment of the invention, and FIG. 2 is a longitudinal sectional front view of only essential parts of an embodiment of the second invention. 2...Main intake duct, 4...Large bench lily, 5...Small pen 13-churi, 7...Throttle valve, 11...Main fuel nozzle,
12... Air bleed pipe, 13... Annular chamber, 15...
...Fuel passage, 17...Float chamber, 19...Air bleed passage, 40...Negative pressure introduction path, 43...Connection position, 44...Atmospheric pressure responsive valve patent applicant Honda Motor Co., Ltd. Co., Ltd. 14-

Claims (1)

[Scope of Claims] (]) A venturi and a throttle valve are disposed in order from the second flow in the middle of the intake passage, and a fuel nozzle opened in the venturi is communicated with the fuel chamber via an air bleed pipe,
In a carburetor in which the air bleed pipe is communicated with an inlet of the intake passage through an air bleed passage, a negative pressure introduction passage opens into the intake passage upstream from the throttle valve and is connected to the air bleed passage. A vaporizer characterized by being provided with. (2) A venturi and a throttle valve are disposed in order from the upstream side in the middle of the intake passage, and the fuel nozzle opened in the venturi is communicated with the fuel chamber via an air bleed pipe,
In a carburetor in which the air bleed pipe is communicated with an inlet of the intake passage through an air bleed passage, a negative pressure introduction passage opens into the intake passage upstream from the throttle valve and is connected to the air bleed passage. The air bleed passage downstream of the connection position with the negative pressure introduction passage is provided with an atmospheric pressure responsive valve whose opening degree increases as the atmospheric pressure decreases. A vaporizer featuring: