JPS5840655B2 - Multi-cylinder engine fuel distribution system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an improvement in a fuel distribution device for a multi-cylinder engine that distributes and supplies fuel from a common idle fuel passage to independent intake passages during low load operation including idling operation. Regarding.

In a multi-cylinder engine that uses mutually independent intake passages to supply air-fuel mixture from each carburetor to each cylinder or each cylinder group, a communication passage that connects the intake passages with each other is provided downstream of the throttle valve. A bypass air passage that bypasses the throttle valve is communicated with the communication passage, and an idle port (idle fuel passage) is opened in the bypass air passage or the communication portion between the bypass passage and the communication passage, and the throttle valve is used for idling operation, etc. Fuel (mixture) to each intake passage when fully closed
Fuel distribution systems for multi-cylinder engines that share the supply of fuel and simplify adjustment of idle fuel have been known for some time.

However, in the above-mentioned fuel distribution device, since the idle port opens directly into the communication passage or into the bypass air passage just upstream of the communication passage, the fuel is almost identical to the air flowing downstream from the bypass air passage. Because it tends to be led out to the communication path without being mixed,
If the idle adjustment screw is eccentric with respect to the idle port, the fuel distribution will be uneven and the distribution characteristics will vary depending on the position of the idle adjustment screw, resulting in extremely unstable distribution performance.

This invention was made to solve the conventional problems, and it improves the mixing of fuel and air and has stable distribution performance, so that it can be used during low load operation including idling operation. The basic object of the present invention is to provide a fuel distribution device for a multi-cylinder engine that can improve the combustibility and drivability of the engine.

Therefore, in the present invention, an enlarged chamber having a cross-sectional area sufficiently larger than the cross-sectional area of the bypass air passage is provided downstream of the bypass air passage, and air is drawn out from the idle port opened at the bottom of the bypass air passage. The fuel mixed with the air flowing down the bypass air passage is sufficiently mixed by turbulence in the expansion chamber to equalize the air-fuel ratio of the air-fuel mixture, and then the generated air-fuel mixture is passed through a small-diameter distribution path. It is characterized in that the air is distributed from the enlarged chamber to each intake passage.

Hereinafter, the present invention will be described in more detail with reference to the illustrated embodiments.

In FIG. 1, 1 and 2 are mutually independent intake passages that communicate with different cylinders (not shown), 3 is an air bypass passage that bypasses the throttle valve 16, and 4 is connected downstream of the air bypass passage 3. , an enlarged chamber with a circular cross section provided at a position forming the apex of an isosceles triangle with respect to the intake passages 1 and 2; 5 and 6 are distribution passages with a small diameter cross section that communicate the enlarged chamber 4 and each intake passage 1 and 2, respectively; , 7 is a communication passage that communicates the intake passages 1 and 2 with each other downstream of the distribution passages 5 and 6, and the communication passage 7 is a communication passage between the intake passages 1 and 2 due to poor sealing when the throttle valve is fully closed. This eliminates the negative pressure imbalance and stabilizes the suction of fuel from the distribution passages 5 and 6.

As shown in FIG. 2, an idle port 8 serving as an idle fuel passage is opened in the bypass air passage 3 slightly upstream of the part where the passage 3 communicates with the expansion chamber 4, and a slow system fuel passage 9 is connected to the idle port 8 as an idle fuel passage. A portion of the supplied fuel is supplied to the bypass air passage 3.

The amount of fuel flowing out of the idle port 8 is set by adjusting a well-known idle adjustment screw 10.

In addition, the setting of the amount of bypass air in the bypass air passage 3 is as follows.
Similarly, the bypass air adjustment screw 11 is used.

As shown in FIG. 1, the bypass air passage 3 consists of intersections A and B between the symmetry center line In order to direct the bypass air flow a flowing vertically downward through the bypass air passage 3 through the curved portion 3a formed at the lower end thereof, to flow in the diametrical direction of the enlarged chamber 4 without unnecessarily disturbing the flow. is deflected perpendicularly to the peripheral wall of the enlarged chamber 4 facing the above-mentioned communication section (section B).
By causing the two to collide with each other, a swirling flow C that is bilaterally symmetrical with respect to the center line of symmetry X is generated.

Furthermore, the opening positions of the small-diameter distribution passages 5 and 6 should be set on the left side with respect to the symmetry center line Y of the enlarged chamber 4, which is perpendicular to the symmetry center line X of the intake passages 1 and 2, and away from the collision position of the air-fuel mixture. This is more preferable in terms of ensuring a long residence time and improving mixing.

In addition, in order to prevent the fuel drawn out from the idle port 8 from accumulating in the liquid state 5 and at the bottom of the expansion chamber 4,
It is preferable that the small-diameter distribution channels 5 and 6 have a rectangular cross section and open at the bottom of the expansion chamber 4 so that their bottom surfaces match the bottom surface of the expansion chamber 4.

Note that the expansion chamber 4 includes a carburetor 12 and an intake manifold 13.
It is formed using the upper insulator 14 in the figure among the two-layer insulators 14 and 15 interposed between the
Furthermore, if the communicating path 7 is formed using the lower insulator 15, the processing can be made that much easier.

In FIG. 2, 16 is a throttle valve provided upstream of the distribution path 5 of the intake passage 1, and 17 is connected to the slow system fuel passage 9, and when the throttle valve 16 is fully closed, it opens across the upstream and downstream sides. It is a slow port.

As described above, when the enlarged chamber 4 communicating with the downstream side of the bypass air passage 3 is provided, and the small diameter distribution passages 5 and 6 communicating between the enlarged chamber 4 and each intake passage 1 and 2 are provided, the bypass air adjustment Air flow a metered by the screw 11 and flowing down the bypass air passage 3 flows into the expansion chamber 4 together with idle fuel metered by the idle adjustment screw 10.

At this time, the air flow a is smoothly converted into a radial flow that crosses the enlarged chamber 4 in the diametrical direction by the curved portion 3a, and the radial flow passes through the longest distance of the enlarged chamber 4 to the enlarged chamber 4 facing the communication portion. collides with the surrounding wall.

The colliding air flow becomes a swirling flow or a turbulent flow C, temporarily stagnates, and is finally sucked into each of the intake passages 1 and 2 by the intake negative pressure acting on the distribution passages 5 and 6.

Therefore, the fuel drawn out from the idle port 8 is
It is suspended by the air flows a, b, and c for a relatively long time, during which mixing with the air is promoted.

Therefore, since the air-fuel mixture with a uniform air-fuel ratio is retained in the enlarged chamber 4, the air-fuel mixture is uniformly distributed in each intake passage 1 and 2 via the distribution passages 5 and 6. A mixture with a suitable air-fuel ratio is supplied, and variations in combustion between cylinders can be prevented.

In this case, the communication passage 7 can maintain the intake negative pressure acting on both the distribution passages 5.6 at the same pressure at all times even if there are variations in the opening degree of the throttle valve 16.
The distribution from 6 is made more stable.

Although not specifically shown in the drawings, when blow-by gas or evaporated fuel is recirculated or supplied to the intake passage, it is first introduced into the enlarged chamber 4 and then passed along with the air-fuel mixture through the distribution passages 5 and 6. It may be supplied to each intake passage 1, 2,
Alternatively, an air passage may be opened separately to supply air.

In this case, in order to promote fuel mixing, blow-by gas, evaporated fuel, air, etc. should be introduced into the enlarged chamber peripheral wall (section B) facing the communication section so as to oppose the radial air flow. By doing so, better mixing performance can be obtained.

As described above, the present invention allows the distribution of idle fuel when the throttle valve is fully closed to the enlarged chamber provided downstream of the bypass air passage and the small diameter distribution passage that communicates with the enlarged chamber and an independent intake passage. According to the present invention, it is possible to sufficiently promote mixing of the bypass air and idle fuel in the expansion chamber, and the mixture with a uniform air-fuel ratio accumulated in the expansion chamber can be Negative intake pressure can be introduced uniformly into the intake passage, and fuel can be supplied to each cylinder without variation. As a result, the combustion performance of each cylinder can be improved, resulting in improved engine drivability.
It is possible to have the effect of improving performance/performance.

[Brief explanation of drawings]

FIG. 1 is a bottom view of a carburetor according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view taken along line A--A in FIG. 1.2... Intake passage, 3... Bypass air passage, 4... Expansion chamber, 5, 6...
Distribution path, 8... Idle port, 9...
・Slow system fuel passage, 10... Idle adjustment screw.

Claims (1)

[Scope of Claims] 1. An independent intake passage is provided for each cylinder or each cylinder group, and an idle fuel passage is opened in a bypass air passage through a throttle valve. In a multi-cylinder engine in which the air-fuel mixture in the bypass air passage is distributed to each intake passage downstream of each throttle valve, an enlarged chamber is formed downstream of the bypass air passage;
A fuel distribution device for a multi-cylinder engine, characterized in that the enlarged chamber and each of the intake passages are communicated through small diameter distribution passages.