JP2722159B2 - Variable venturi carburetor for gasoline engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable venturi carburetor for a gasoline engine, and more particularly to a technique for adjusting the amount of fuel discharged from a main nozzle in accordance with the venturi opening of a variable venturi body.

[0002]

[Base technology of the present invention] The basic structure of a variable venturi carburetor on which the present invention is based is, for example, as shown in FIG.
Main nozzle 5 in venturi section 4 of venturi tube 1
The main nozzle 5 communicates with the fuel passage 6 of the float chamber 7, a variable venturi body 15 is arranged opposite the main nozzle 5, and a pressure operating chamber 21 is provided in the venturi tube 1. A pressure-operated valve 17 is provided in the pressure-operated chamber 21 integrally with the variable venturi body 15 so that the venturi opening D can be automatically set.

The pressure operating chamber 21 is provided with the pressure operating valve 17.
And an upstream pressure working chamber 21a communicating with the upstream suction passage 1a of the venturi section 4 and a downstream pressure working chamber 21 communicating with the downstream suction passage 1b of the venturi section 4.
b and the upstream intake pressure Va in the upstream pressure working chamber 21a acting on the pressure working valve 17 and the downstream pressure working chamber 21b.
The Venturi opening D of the variable venturi body 15 is set by antagonizing the downstream intake pressure Vb in the inside and the urging force of the urging spring 18, and the main nozzle 5 is set in correspondence with the Venturi opening D. The fuel discharge amount is set.

[0004]

2. Description of the Related Art Conventionally, as shown in FIG. 4, in order to prevent an excessive amount of fuel from being discharged due to clogging of an air cleaner, an upstream intake passage 1a of a float chamber 8 and a venturi section 4 is used. Float chamber communication path 1
2 communicates with, has a mechanism in which the fuel 10 within the float chamber 7 is sucked out by the differential pressure δP between pressure P _f in pressure P _v and the float chamber 8 of the venturi portion 4.

In this conventional example, as shown in FIG.
A tapered needle 35 protrudes from the end surface of the Venturi body of the variable Venturi body 15, and this needle 35 is inserted from the tip end of the main nozzle 5.
The amount of fuel discharged from the main nozzle 5 is automatically adjusted in conjunction with the venturi opening D of the fuel cell. That is, when the venturi opening D of the variable venturi body 15 is large, the needle 35 comes out of the main nozzle 5 and discharges an appropriate amount of fuel to be discharged to the venturi portion 4.
Is inserted deeper into the main nozzle 5 to reduce the effective area of the main nozzle 5 and suppress excessively discharged fuel.

[0006] This is because the venturi opening D of the variable venturi body 15 and the differential pressure δP do not have an ideal proportional relationship as shown by a straight line G in FIG. As shown by g, since the differential pressure δP becomes relatively excessive as the venturi opening degree D becomes smaller, the excessive fuel discharge accompanying this is suppressed to secure an appropriate fuel discharge amount. . Reference numeral 36 in FIG. 4 denotes an oil damper. The oil damper 36 is provided to prevent the downstream-side intake negative pressure Vb acting on the pressure-operated valve 17 from delicately fluctuating due to intake pulsation or the like. It is.

[0007]

In the above prior art, as the venturi opening degree D of the variable venturi body 15 decreases, the differential pressure δP becomes excessive, so that the needle 3
The correction is made by the method 5 to secure an appropriate fuel discharge amount, but has the following disadvantages. That is, since the needle 35 integrally linked with the variable venturi body 15 is located at the center of the venturi section 4, the needle 35 obstructs the flow of the air A flowing through the venturi section 4. For this reason, atomization and miniaturization of the fuel discharged from the main nozzle 5 are hindered, and this is a bad effect in obtaining uniform air-fuel mixing. The present invention has been made in view of such circumstances, and corrects the excess of the differential pressure δP as the venturi opening degree D decreases, thereby ensuring an appropriate fuel discharge amount, while preventing the fuel mist. It is an object of the present invention to obtain a more uniform air-fuel mixture by promoting miniaturization and miniaturization.

[0008]

In order to solve the above-mentioned problems, the present invention employs a variable venturi carburetor having the above-mentioned basic structure.
a and the upstream intake passage 1a are communicated via the upstream pressure communication passage 22, and the downstream pressure working chamber 21b and the downstream intake passage 1b are communicated via the boost pressure communication passage 23,
The downstream pressure working chamber 21b communicates with the upstream pressure working chamber 21a through the orifice 25, and the upstream pressure working chamber 21a and the float chamber 8 in the float chamber 7 communicate with each other through the float chamber communication passage 12. The gist is that a communication valve 30 is provided in the float chamber communication passage 12, and the communication valve 30 is configured to increase the valve opening as the venturi opening D decreases in conjunction with the pressure operated valve 17. Things.

[0009]

According to the present invention, as the venturi opening degree D of the variable venturi body 15 decreases, the differential pressure δP
Is corrected as follows to secure an appropriate fuel discharge amount. That is, during high load operation of the engine, since the throttle valve 3b is substantially fully opened and the boost pressure Vb is minimized, the differential pressure between the upstream intake pressure Va and the downstream intake pressure Vb in the venturi pipe 1 is reduced. Therefore, the pressure difference between the air pressure in the upstream pressure operation chamber 21a and the air pressure in the downstream pressure operation chamber 21b becomes small, and the pressure operation valve 17 is pushed up by the urging force of the urging spring 18 so that the maximum venturi of the variable venturi body 15 is opened. Secure degree D. At this time, the amount of air flowing through the venturi section 4 becomes maximum.

On the other hand, the upstream pressure working chamber 21a and the downstream pressure working chamber 21b communicate with each other through the orifice 25. However, since the pressure difference between the two chambers is small, the air pressure in the upstream pressure working chamber 21a is higher than the upstream pressure in the venturi tube 1. It becomes substantially equal to the side intake pressure Va. At this time, the communication valve 30 decreases the valve opening or closes in conjunction with the pressure actuated valve 17. In this state, the pressure P _f of the funnel chamber 8, air pressure of the upstream pressure operation chamber 21a,
That is, it is substantially equal to the upstream intake pressure Va in the venturi tube 1. Therefore, at the time of high load operation of the engine the pressure difference δP between the air pressure P _f in pressure P _v and the float chamber 8 of the venturi portion 4 is maximized, the proper fuel discharge amount is ensured.

On the other hand, as the engine operates at a low speed and a low load, the opening degree of the throttle valve 3b decreases and the boost pressure Vb gradually increases. Therefore, the upstream intake pressure Va and the boost pressure Vb in the venturi pipe 1 are increased. And the pressure difference between them also increases. Therefore, the pressure difference between the air pressure in the upstream pressure operation chamber 21a and the air pressure in the downstream pressure operation chamber 21b also increases, and the air pressure in the upstream pressure operation chamber 21a increases the boost pressure Vb of the downstream pressure operation chamber 21b and the urging spring 18. To depress the pressure-operated valve 17 to secure the required venturi opening D of the variable venturi body 15. At this time, the amount of air flowing through the venturi section 4 gradually decreases.

On the other hand, since the upstream pressure working chamber 21a and the downstream pressure working chamber 21b communicate with each other through the orifice 25, a part of the boost pressure Vb leaks and the pressure in the upstream pressure working chamber 21a becomes It becomes slightly lower than the upstream intake pressure Va. At this time, the opening of the communication valve 30 gradually increases in conjunction with the pressure-operated valve 17. In this state, the air pressure in the upstream pressure working chamber 21a is lower than the upstream intake pressure Va of the venturi pipe 1. That is, as the engine operates at low speed and low load, the float chamber 8
Becomes pressure P _f of the inner is lower than the upstream intake air pressure Va, the differential pressure δP between pressure P _f in pressure P _v and the float chamber 8 of the venturi portion 4 suppresses become excessive.

[0013]

In the present invention, as the engine slows, low load operation, by pressure P _f of the float chamber 8 is lower than the upstream intake air pressure Va of venturi tube 1, pressure venturi section 4 since the pressure difference δP between the P _v and pressure P _f of the float chamber 8 has to be prevented from becoming excessive, in conjunction with the venturi opening D of the variable base Nchuri body, proper fuel from the main nozzles A discharge amount can be secured. In addition, since a needle that obstructs the flow of air flowing through the venturi can be omitted, atomization and miniaturization of fuel can be promoted as compared with the related art, and more uniform air-fuel mixing can be obtained.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram schematically showing a variable venturi carburetor according to a first embodiment of the present invention. As shown in FIG. 1, the variable venturi vaporizer has a basic structure similar to that of the prior art. That is, the leading end of the main nozzle 5 faces the venturi portion 4 of the venturi tube 1, the fuel nozzle 6 of the float chamber 7 communicates with the main nozzle 5, and the variable venturi body 15 is opposed to the main nozzle 5 to ventilate the variable venturi body 15. A pressure-actuated valve body 17 is provided so that the opening degree can be set freely, and is integrally linked via a support shaft 16 of the variable venturi body 15. The pressure-operated valve body 17 is constituted by a diaphragm 17a,
Act in a direction to push up the diaphragm 17a.

A pressure working chamber rib 20 for forming a pressure working chamber 21 is fixed to the rib 2 by projecting a rib 2 for a pressure working chamber from the venturi tube 1. This pressure working chamber 2
Reference numeral 1 denotes a downstream pressure working chamber 21b and an upstream pressure working chamber 21a divided into two by the diaphragm 17a. The upstream pressure working chamber 21a communicates with the upstream intake passage 1a of the venturi section 4 through the upstream pressure communication passage 22, and the downstream pressure working chamber 2a.
1 b communicates with the downstream side intake passage 1 b of the venturi section 4 via the downstream pressure communication passage 23.

Hereinafter, the characteristic structure of the apparatus of this embodiment will be described. The pressure working chamber 21 is provided with the variable hentry body 1.
The downstream pressure working chamber 21b and the upstream pressure working chamber 21a are sequentially arranged from the fifth side.
And a communication chamber case 26 in which a float chamber communication chamber 27 adjacent to the upstream pressure working chamber 21a is formed.
Is fixed. The float chamber communication chamber 27 is configured as a part of the float chamber communication path 12. This upstream pressure working chamber 21a and the upstream intake passage 1 of the venturi section 4
An orifice 24 is interposed in the upstream pressure communication passage 22 that communicates with a. Since the downstream intake pressure Vb acting on the pressure operation valve 17 fluctuates excessively due to the intake pulsation of the piston, the orifice 24 suppresses the excessive following operation of the pressure operation valve 17 from the upstream pressure operation chamber 21a side. It is for.

The downstream pressure working chamber 21b is connected to the downstream pressure communication passage 2
The downstream pressure communication passage 23 is formed as a boost pressure communication passage for guiding a boost pressure downstream of the throttle valve 3b to the downstream pressure working chamber 21b through the downstream pressure passage 23b. Further, the downstream pressure working chamber 21
b communicates with the upstream pressure working chamber 21a via the orifice 25. The orifice 25 is for applying the boost pressure Vb mainly to the downstream pressure working chamber 21b while avoiding the boost pressure Vb directly acting on the upstream pressure working chamber 21a.

Furthermore, the orifice 25 is to leak a portion of the boost pressure Vb upstream pressure operation chamber 21a, venturi air pressure P _f of the float chamber 8 through a float chamber communicating chamber 27 and the float chamber communication path 12 1 is intended to be slightly lower than the upstream-side intake negative pressure Va. That is, by making the air pressure P _f in the float chamber 8 slightly lower than the upstream intake negative pressure Va of the venturi section 4, the differential pressure δP becomes relatively excessive as the venturi opening degree D becomes smaller (see FIG. 6). This is because the pressure difference δP is reduced to an ideal straight line indicated by the symbol G in FIG.

A communication valve 30 is provided on a partition wall 28 between the upstream pressure working chamber 21a and the float chamber communication chamber 27. The communication valve 30 includes a tapered valve body 31 provided at the other end of the support shaft 16 of the variable venturi body 15 and a communication hole 32 formed through the partition wall 28. The effective cross-sectional area of the communication hole 32 is changed in coordination with the above, and the valve opening is increased as the boost pressure Vb increases.

Hereinafter, the operation of the above embodiment will be briefly described. During high load operation of the engine, the throttle valve 3b
Greatly increases, the boost pressure Vb decreases, and the differential pressure between the upstream intake pressure Va of the upstream pressure working chamber 21a and the boost pressure Vb of the downstream pressure working chamber 21b decreases. As a result, the diaphragm 17a is pushed up by the urging force of the urging spring 18, and the maximum venturi opening D of the variable venturi body 15 is increased.
To secure.

At this time, the communication valve 30 is the pressure-operated valve 1
7, the valve opening is reduced or closed. Pressure P _f of the funnel chamber 8 in this state is approximately equal to or upstream intake air pressure Va of venturi portion 4 through a float chamber communicating chamber 27, or is slightly lower. In other words, at the time of high load operation of the engine the pressure difference δP between the air pressure P _f in pressure P _v and the float chamber 8 of the venturi portion 4 is maintained at the maximum, the maximum fuel discharge amount is ensured.

On the other hand, as the opening of the throttle valve 3b decreases and the engine operates at a low speed and a low load,
Although the boost pressure Vb increases, the orifice 25 of the boost pressure communication passage 23 communicating with the upstream pressure working chamber 21a causes the boost pressure Vb of the downstream pressure working chamber 21b to intervene.
Becomes sufficiently lower than the air pressure of the upstream pressure working chamber 21a, and this air pressure overcomes the urging force of the urging spring 18 and pushes down the diaphragm 17a, thereby gradually reducing the venturi opening D of the variable venturi body 15.

At this time, the communication valve 30 works together with the diaphragm 17a to increase the valve opening. In this state, since the downstream pressure working chamber 21b communicates with the upstream pressure working chamber 21a via the orifice 25, the boost pressure V
The pressure in the upstream pressure working chamber 21a is lower than the upstream suction negative pressure Va of the venturi tube 1 due to a part of b leaking. That is, as the engine operates at low speed and low load, the air pressure P _f in the float chamber 8 becomes lower than the upstream intake pressure Va of the venturi pipe 1 via the float chamber communication chamber 27, and the air pressure in the venturi section 4 is reduced. differential pressure δp between P _v and pressure P _f of the float chamber 8 suppresses become excessive. As a result, excessive fuel discharge is suppressed, and an appropriate fuel discharge amount is secured.

Further, since a needle for obstructing the flow of air flowing through the venturi section can be omitted, atomization and miniaturization of fuel can be promoted as compared with the prior art, and a more uniform air-fuel mixture can be obtained. . In addition, as in this embodiment,
When a communication valve 30 is provided in a partition wall 28 between the upstream pressure working chamber 21a and the float chamber communication chamber 27 and the communication valve 30 is integrally linked with the variable venturi body 15, there is an advantage that the configuration is simplified. .

FIG. 2 is a sectional view of a main part showing a second embodiment of the present invention. In this embodiment, instead of the variable venturi body 15 and the diaphragm 17a, a piston-shaped variable venturi body 15 similar to the conventional example and a pressure-operated valve 17 formed integrally therewith are used. Other points are the same as those of the first conventional example shown in FIG. FIG.
The members having the same functions as those described above are denoted by the same reference numerals and description thereof will be omitted.

FIG. 3 is a sectional view of a main part showing a third embodiment of the present invention. In this embodiment, the upstream pressure working chamber 21
The third embodiment differs from the above-described embodiment in that an orifice 25 for communicating a with the downstream pressure working chamber 21b is provided in the pressure working valve 17. Further, in this embodiment, as a configuration for operating the communication valve 30 in accordance with the venturi opening degree D, the float chamber communication chamber 27 in FIG. 2 is omitted, and the communication valve 30 is provided in the float chamber communication passage 12, This embodiment is different from the above embodiment in that the communication valve 30 is operated by another control circuit 30a.

The control circuit 30a includes a subject 33a provided on the pressure-operated valve 17, a position sensor 33b of the pressure-operated valve 17 provided on the outer periphery of the pressure-operated chamber case 20, and detection from the position sensor 33b. The control circuit 34 receives the signal and controls the opening of the communication valve 30. The control circuit 34 controls the amount of fuel discharged from the main nozzle 5 in accordance with the venturi opening D in the same manner as in the embodiment of FIGS. Is configured to be corrected.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a vaporizer according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a vaporizer according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a vaporizer according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically showing a vaporizer according to a conventional example.

FIG. 5 is a graph showing a relationship between a venturi opening degree D and a differential pressure δP between a float chamber pressure and a venturi portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Venturi pipe, 1a ... Upstream intake path, 1b ... Downstream intake path, 3b
... Throttle valve, 4 ... Venturi section,
5: Main nozzle, 6: Fuel passage of float chamber, 7: Float chamber, 8: Float chamber,
12: Float chamber communication path, 15: Variable venturi body, 17: Pressure operated valve, 1
8 ... biasing spring 21 ... pressure working chamber 21a ... upstream pressure working chamber 21b ...
Downstream pressure working chamber, 22 ... upstream pressure communication passage,
23 ... Boost pressure communication passage, 24/25 ... Orifice,
27 ... Float chamber communication chamber, 28 ...
30: communication valve D: venturi opening degree, Va: upstream intake pressure, Vb: downstream intake pressure (boost pressure).

Claims (3)

(57) [Claims] An end of a main nozzle is made to face a venturi portion of a venturi tube.
Communicates with the fuel passage 6 of the float chamber 7, and the variable venturi body 1 faces the main nozzle 5.
5 is disposed so that the venturi opening can be set freely, a pressure-operated valve 17 is provided integrally with the variable venturi body 15, and a pressure-operated chamber 21 is provided in the venturi tube 1. An upstream pressure working chamber 21a divided into two by the valve 17 and communicating with the upstream intake passage 1a of the venturi section 4, and a downstream pressure working chamber 21b communicating with the downstream intake path 1b of the venturi section 4. The upstream intake pressure Va of the upstream pressure working chamber 21a acting on the pressure operating valve 17 and the downstream intake pressure V of the downstream pressure working chamber 21b.
b and the urging force of the urging spring 18 to antagonize to set the venturi opening D of the variable venturi body 15, and to set the fuel discharge amount from the main nozzle 5 corresponding to the venturi opening D. In the variable venturi carburetor for a gasoline engine configured as described above, the upstream pressure working chamber 21a and the upstream intake passage 1a are communicated via an upstream pressure communication passage 22, and the downstream pressure working chamber 21b
And the downstream-side intake passage 1b are communicated via a boost pressure communication passage 23, and the downstream pressure operation chamber 21b is communicated with an upstream pressure operation chamber 21a via an orifice 25. The float chamber 8 in the chamber 7 is communicated via a float chamber communication path 12, and a communication valve 30 is provided in the float chamber communication path 12. A variable venturi carburetor for a gasoline engine, characterized in that the valve opening is increased with decreasing D. 2. A float chamber communication chamber 27 adjacent to the upstream pressure working chamber 21a is provided as a part of the float chamber communication path 12, and a partition wall 28 between the upstream pressure working chamber 21a and the float chamber communication chamber 27 communicates with the partition. The variable venturi carburetor of a gasoline engine according to claim 1, wherein a valve 30 is provided, and the communication valve 30 is configured to interlock with the pressure operated valve 17 integrally. 3. An orifice 2 is provided in the upstream pressure communication passage 22.
The variable venturi carburetor for a gasoline engine according to claim 1 or 2, wherein the variable venturi carburetor is provided.