JPH06147015A - Variable venturi type carburetor for gasoline engine - Google Patents

Abstract

PURPOSE:To provide more uniform air-fuel mixing by promoting the atomization and fineness of fuel while ensuring appropriate fuel discharge quantity corresponding to benturi opening D. CONSTITUTION:The upstream pressure operating chamber 21a and the upstream side suction path 1a are communicated via the upstream pressure communication path 22, and the downstream pressure operating chamber 21b and the downstream side suction path 1b are communicated via a boost pressure communication path 23. The downstream pressure operating chamber 21b and the float chamber 8 in a float chamber 7 are communicated via a float chamber communication path 12. A communication valve 30 is provided on the float chamber communication path 12, and is composed so as to increase valve opening as well as to reduce benturi opening D while interlocking a pressure operating valve 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable venturi type 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]

The basic structure of the variable venturi type vaporizer which is the premise of the present invention is as shown in FIG.
The main nozzle 5 in the venturi section 4 of the venturi tube 1
The fuel passage 6 of the float chamber 7 is communicated with the main nozzle 5 and the variable venturi body 15 is arranged facing the main nozzle 5, and the pressure working chamber 21 is attached to the venturi pipe 1. In addition, a pressure actuating valve body 17 that works together with the variable venturi body 15 is provided in the pressure actuating chamber 21 so that the venturi opening D can be automatically set.

The pressure-operated chamber 21 has the pressure-operated valve 17 described above.
Is divided into two parts, and an upstream pressure working chamber 21a communicating with the upstream intake passage 1a of the venturi portion 4 and a downstream pressure working chamber 21 communicating with the downstream intake passage 1b of the venturi portion 4.
b, and the upstream side 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 counteracting the downstream side intake pressure Vb and the urging force of the urging spring 18 from the main nozzle 5 in correspondence with the venturi opening D. Is configured to set the fuel discharge amount.

[0004]

2. Description of the Related Art In the above carburetor, as shown in FIG. 4, conventionally, in order to prevent the fuel discharge amount from becoming excessive due to the clogging of the air cleaner, the upstream intake passage 1a of the float chamber 8 and the venturi portion 4 is eliminated. And directly to the float chamber communication path 1
The fuel 10 in the float chamber 7 is communicated by two and is sucked out by the differential pressure δP between the atmospheric pressure P _{v in the} venturi portion 4 and the atmospheric pressure P _f in the float chamber 8.

Further, in this conventional example, as shown in FIG.
The variable venturi body 15 is provided with a tapered needle 35 projecting from the end face of the venturi, and the needle 35 is inserted from the tip of the main nozzle 5 to form the variable venturi body 15.
The fuel discharge amount from the main nozzle 5 is automatically adjusted in association with the venturi opening D of the above. 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, and as the venturi opening D becomes smaller, the needle 35 becomes smaller.
Are inserted deeper into the main nozzle 5 to reduce the effective area of the main nozzle 5 and suppress excessively discharged fuel.

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 indicated by g, the differential pressure δP becomes relatively excessive as the Venturi opening D becomes smaller, so that excessive fuel discharge accompanying this is suppressed and an appropriate fuel discharge amount is secured. . Reference numeral 36 in FIG. 4 is an oil damper. The oil damper 36 is for preventing the pressure operated valve 17 from excessively following the negative intake pressure Vb acting on the pressure operated valve 17 because the downstream side intake negative pressure Vb fluctuates excessively due to intake pulsation or the like. Is.

[0007]

In the above-mentioned prior art, the differential pressure δP becomes excessive as the venturi opening D of the variable venturi body 15 becomes smaller, so that the needle 3
Although it is corrected by 5 to secure an appropriate fuel discharge amount, there are the following inconveniences. That is, since the needle 35 that is interlocked with the variable venturi body 15 is located at the center of the venturi portion 4, the flow of the air A flowing through the venturi portion 4 is obstructed. Therefore, it hinders atomization and atomization of the fuel discharged from the main nozzle 5, which is an obstacle in obtaining a uniform air-fuel mixture. The present invention has been made in consideration of such a situation, and corrects the excess of the differential pressure δP as the venturi opening D becomes smaller to ensure an appropriate fuel discharge amount, and at the same time, atomizes the fuel. The technical problem is to obtain a more uniform air-fuel mixture by promoting miniaturization and miniaturization.

[0008]

The means adopted by the present invention for solving the above-mentioned problems is, in the variable venturi type carburetor having the basic structure, the upstream pressure working chamber 21.
a and the upstream intake passage 1a are communicated with each other through the upstream pressure communication passage 22, and the downstream pressure working chamber 21b and the downstream intake passage 1b are communicated with each other through the boost pressure communication passage 23.
The downstream pressure working chamber 21b is communicated 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 are communicated with each other through the float chamber communication passage 12. A communication valve 30 is provided in the float chamber communication passage 12, and the communication valve 30 is configured so as to interlock with the pressure-operated valve 17 to increase the valve opening as the venturi opening D decreases. It is a thing.

[0009]

In the present invention, as the venturi opening D of the variable venturi body 15 becomes smaller, the differential pressure .delta.P becomes smaller.
Is corrected in the following manner to ensure a proper fuel discharge amount. That is, when the engine is operating under a high load, the throttle valve 3b is substantially fully opened and the boost pressure Vb is minimized, so that 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 working chamber 21a and the air pressure in the downstream pressure working chamber 21b becomes small, and the pressure actuating valve 17 is pushed up by the urging force of the urging spring 18 to open the maximum venturi of the variable venturi body 15. Secure a degree D. At this time, the amount of air flowing through the venturi portion 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 atmospheric pressure in the upstream pressure working chamber 21a is upstream in the venturi pipe 1. It becomes substantially equal to the side intake pressure Va. At this time, the communication valve 30 works in conjunction with the pressure operated valve 17 to reduce the valve opening or close the valve. In this state, the atmospheric pressure P _f in the funnel chamber 8 is the atmospheric pressure in the upstream pressure working chamber 21a,
That is, it is substantially equal to the upstream intake pressure Va in the Venturi pipe 1. Therefore, the differential pressure δP between the atmospheric pressure P _v of the venturi portion 4 and the atmospheric pressure P _f in the float chamber 8 is maximized during high-load operation of the engine, and an appropriate fuel discharge amount is secured.

On the other hand, as the engine operates at low speed and under low load, the valve opening 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. The pressure difference between and also becomes large. Therefore, the differential pressure between the atmospheric pressure in the upstream pressure operating chamber 21a and the atmospheric pressure in the downstream pressure operating chamber 21b also becomes large, and the atmospheric pressure in the upstream pressure operating chamber 21a becomes equal to the boost pressure Vb of the downstream pressure operating chamber 21b and the urging spring 18. The pressure actuated valve 17 is pushed down by overcoming the urging force of the variable venturi body 15 to secure the required venturi opening D of the variable venturi body 15. At this time, the amount of air flowing through the venturi portion 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 atmospheric pressure in the upstream pressure working chamber 21a is in the venturi pipe 1. It becomes slightly lower than the upstream intake pressure Va. At this time, the communication valve 30 interlocks with the pressure operated valve 17 and the valve opening gradually increases. In this state, the atmospheric pressure of the upstream pressure working chamber 21a is lower than the upstream intake pressure Va of the Venturi pipe 1. In other words, as the engine operates at low speed and low load, the float chamber 8
The internal pressure P _f becomes lower than the upstream intake pressure Va, and the differential pressure δP between the atmospheric pressure P _v of the venturi section 4 and the atmospheric pressure P _f in the float chamber 8 is suppressed from becoming excessive.

[0013]

According to the present invention, the atmospheric pressure P _f in the float chamber 8 becomes lower than the upstream side intake pressure Va of the venturi pipe 1 as the engine operates at low speed and low load, so that the atmospheric pressure in the venturi portion 4 is reduced. Since the differential pressure δP between P _v and the atmospheric pressure P _f in the float chamber 8 is prevented from becoming excessive, an appropriate fuel from the main nozzle is linked with the venturi opening D of the variable venturi body. A discharge amount can be secured. Moreover, since the needle that obstructs the air flow flowing through the venturi portion can be omitted, atomization and atomization of the fuel can be promoted as compared with the prior art, and a more uniform air-fuel mixture 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 vaporizer according to a first embodiment of the present invention. As shown in FIG. 1, this variable venturi vaporizer has the same basic structure as that of the prior art. That is, the venturi portion 4 of the venturi pipe 1 faces the tip of the main nozzle 5, the fuel passage 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 so that the variable venturi body 15 is placed in the venturi. A pressure actuated valve body 17 is provided which is arranged so that the opening degree can be freely set and which is integrally interlocked via a support shaft 16 of the variable venturi body 15. This pressure-operated valve body 17 is composed of a diaphragm 17a, and has a biasing spring 18
Causes the diaphragm 17a to be pushed up.

A rib 2 for a pressure working chamber is projected from the venturi pipe 1, and a case 20 for a pressure working chamber forming a pressure working chamber 21 is fixedly mounted on the rib 2. This pressure working chamber 2
Reference numeral 1 is composed of a downstream pressure working chamber 21b and an upstream pressure working chamber 21a which are partitioned into two by the diaphragm 17a. The upstream pressure working chamber 21a communicates with the upstream side intake passage 1a of the venturi portion 4 through the upstream pressure communicating passage 22, and the downstream pressure working chamber 2
1 b communicates with the downstream intake passage 1 b of the Venturi portion 4 via the downstream pressure communication passage 23.

The characteristic structure of the apparatus of this embodiment will be described below. The pressure working chamber 21 is a variable Hentury body 1.
The downstream pressure working chamber 21b and the upstream pressure working chamber 21a in order from the 5 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.
To be fixed. The float chamber communication chamber 27 is configured as a part of the float chamber communication passage 12. The upstream pressure working chamber 21a and the upstream intake passage 1 of the venturi portion 4
An orifice 24 is interposed in the upstream pressure communication passage 22 communicating with a. Since the downstream side intake pressure Vb acting on the pressure operated valve 17 is excessively fluctuated by the intake pulsation by the piston, the orifice 24 suppresses the sensitive follow-up operation of the pressure operated valve 17 from the upstream pressure operating chamber 21a side. It is for.

The downstream pressure working chamber 21b has a downstream pressure communication passage 2
The downstream pressure communication passage 23 is formed as a boost pressure communication passage for inducing the boost pressure on the downstream side of the throttle valve 3b into the downstream pressure working chamber 21b. Further, the downstream pressure working chamber 21
b communicates with the upstream pressure working chamber 21a through the orifice 25. The orifice 25 is for allowing the boost pressure Vb to act mainly in the downstream pressure working chamber 21b while avoiding the boost pressure Vb from directly acting on the upstream pressure working chamber 21a.

Further, the orifice 25 leaks a part of the boost pressure Vb to the upstream pressure working chamber 21a, and the air pressure P _f in the float chamber 8 is ventilated through the float chamber communication chamber 27 and the float chamber communication passage 12. This is intended to be slightly lower than the upstream side intake negative pressure Va of 1. That is, by making the atmospheric pressure P _f in the float chamber 8 slightly lower than the upstream side intake negative pressure Va of the venturi portion 4, the differential pressure δP becomes relatively excessive as the venturi opening D becomes smaller (see FIG. 6). This is because the difference g) is suppressed and the differential pressure δP becomes an ideal straight line indicated by reference sign G in FIG.

A communication valve 30 is provided on a partition 28 between the upstream pressure working chamber 21a and the float chamber communication chamber 27. The communication valve 30 is composed of 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 penetratingly formed in the partition wall 28. The effective cross-sectional area of the communication hole 32 is changed in conjunction with the above, and the valve opening is increased as the boost pressure Vb is increased.

The operation of the apparatus of the above embodiment will be briefly described below. When the engine is operating under high load, the throttle valve 3b
Open greatly and 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 biasing force of the biasing spring 18, and the maximum venturi opening D of the variable venturi body 15 is increased.
Secure.

At this time, the communication valve 30 is the pressure operated valve 1.
The valve opening is made smaller in conjunction with 7 or closed. In this state, the air pressure P _f in the funnel chamber 8 is substantially equal to or slightly lower than the upstream intake pressure Va of the venturi portion 4 via the float chamber communication chamber 27. That is, the differential pressure δP between the atmospheric pressure P _v of the venturi portion 4 and the atmospheric pressure P _f in the float chamber 8 is maintained at the maximum during the high load operation of the engine, and the maximum fuel discharge amount is secured.

On the other hand, as the valve opening of the throttle valve 3b becomes smaller and the engine operates at low speed and low load,
Although the boost pressure Vb increases, the boost pressure Vb in the downstream pressure working chamber 21b is increased by interposing the orifice 25 of the boost pressure communication passage 23 communicating with the upstream pressure working chamber 21a.
Becomes sufficiently lower than the atmospheric pressure of the upstream pressure working chamber 21a, and this atmospheric pressure overcomes the urging force of the urging spring 18 to push down the diaphragm 17a, and the venturi opening D of the variable venturi body 15 is gradually reduced.

At this time, the communication valve 30 is interlocked 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 through the orifice 25, the boost pressure V
A part of b leaks and the air pressure in the upstream pressure working chamber 21a is lower than the upstream intake negative pressure Va of the Venturi pipe 1. 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 becomes low. The differential pressure δp between P _v and the atmospheric pressure P _f in the float chamber 8 is prevented from becoming excessive. As a result, excessive fuel discharge is suppressed and a proper fuel discharge amount is secured.

Moreover, since the needle for obstructing the air flow through the venturi portion can be omitted, atomization and atomization of the 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 the communication valve 30 is provided in the 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 the essential parts showing the second embodiment of the present invention. In this embodiment, the variable venturi body 15 and the diaphragm 17a are replaced with a piston-like variable venturi body 15 similar to the conventional example and a pressure actuated valve 17 formed integrally therewith. The other points are the same as those of the first conventional example shown in FIG. Note that FIG.
The members having the same function as the above are designated by the same reference numerals and the description thereof will be omitted.

FIG. 3 is a sectional view of the essential parts showing a third embodiment of the present invention. In this embodiment, the upstream pressure working chamber 21
The present embodiment differs from the above-described embodiment in that the pressure-operated valve 17 is provided with an orifice 25 that communicates a with the downstream pressure-operated chamber 21b. Further, in the apparatus of this embodiment, the float valve communication chamber 27 of FIG. 2 is omitted and the communication valve 30 is provided in the float chamber communication passage 12 as a configuration in which the communication valve 30 is operated corresponding to the venturi opening D. This embodiment differs from the above embodiment in that the communication valve 30 is configured to be 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 for the pressure operated valve 17 provided on the outer peripheral portion of the pressure operating chamber case 20, and detection from the position sensor 33b. A control circuit 34 that receives a signal and controls the valve opening of the communication valve 30 corresponds to the venturi opening D and the fuel discharge amount from the main nozzle 5 is the same as in the embodiment of FIGS. 1 and 2. It is configured to correct.

[Brief description of 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 carburetor according to a third embodiment of the present invention.

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

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

[Explanation of symbols]

1 ... Venturi pipe, 1a ... Upstream intake passage, 1b ... Downstream intake passage, 3b
… Throttle valve, 4… Venturi part,
5 ... Main nozzle, 6 ... Float chamber fuel passage, 7 ... Float chamber, 8 ... Float chamber,
12 ... Float chamber communication passage, 15 ... Variable venturi body, 17 ... Pressure actuated valve, 1
8 ... Energizing 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 room, 28 ...
Float chamber Communication chamber partition wall, 30 ... Communication valve D ... Venturi opening, Va ... Upstream intake pressure, Vb ... Downstream intake pressure (boost pressure).

Claims (3)

[Claims] 1. A front end of a main nozzle 5 is made to face a venturi portion 4 of a venturi tube 1, and the main nozzle 5
The fuel passage 6 of the float chamber 7 is communicated with the variable venturi body 1 facing the main nozzle 5.
5 is arranged so that the opening degree of Venturi can be freely set, and a pressure actuating valve 17 that is integrally interlocked with the variable venturi body 15 is provided. It is divided into two parts by the valve 17 and comprises an upstream pressure working chamber 21a communicating with the upstream intake passage 1a of the venturi portion 4 and a downstream pressure working chamber 21b communicating with the downstream intake passage 1b of the venturi portion 4. , The upstream side intake pressure Va of the upstream pressure working chamber 21a acting on the pressure working valve 17 and the downstream side intake pressure V of the downstream pressure working chamber 21b.
b and the urging force of the urging spring 18 are antagonized to set the venturi opening D of the variable venturi body 15, and the fuel discharge amount from the main nozzle 5 is set corresponding to the venturi opening D. In the variable venturi type carburetor of the gasoline engine configured as above, the upstream pressure working chamber 21a and the upstream intake passage 1a are communicated with each other through the upstream pressure communication passage 22, and the downstream pressure working chamber 21b is connected.
And the downstream side intake passage 1b are communicated with each other through the boost pressure communication passage 23, and the downstream pressure working chamber 21b is communicated with the upstream pressure working chamber 21a through the orifice 25, so that the upstream pressure working chamber 21a and the float chamber 7 is communicated with the float chamber 8 via a float chamber communication passage 12, and a communication valve 30 is provided in the float chamber communication passage 12, and the communication valve 30 is interlocked with the pressure actuated valve 17 to open the venturi opening. A variable venturi carburetor for a gasoline engine, characterized in that the valve opening is increased as D is decreased. 2. A float chamber communication chamber 27 adjacent to the upstream pressure operation chamber 21a is provided as a part of the float chamber communication passage 12, and the communication is made to a partition wall 28 between the upstream pressure operation chamber 21a and the float chamber communication chamber 27. The variable venturi carburetor for a gasoline engine according to claim 1, wherein a valve 30 is provided, and the communication valve 30 is configured to be interlocked with the pressure operated valve 17. 3. The orifice 2 in the upstream pressure communication passage 22.
The variable venturi type carburetor for a gasoline engine according to claim 1 or 2, wherein the variable venturi type carburetor is provided.