JPS6114347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides 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 idling operation or low-load operation near idling. It is about improvement.

In a multi-cylinder engine that has independent intake passages for each cylinder or cylinder group, a communication passage that communicates the intake passages with each other is provided downstream of the throttle valve, and an idle port is opened in the communication passage near the downstream. A fuel distribution device in which bypass air passages are communicated with each other and the air-fuel mixture in the bypass air passages is distributed to each intake passage through the communication passage as a distribution passage is well known (for example, as disclosed in Japanese Patent Application Laid-Open No. 51-17732).

However, although the above conventional method can simplify the adjustment of idle fuel,
Since the idle port opens into the bypass air passage immediately upstream of the communication passage, fuel tends to be led out to the communication passage without being mixed with the air flowing down from the bypass air passage. Therefore, for example, if the needle valve of the idle adjusting screw is eccentric to the idle port, the fuel distribution will be uneven, and the distribution characteristics will vary depending on the position of the idle adjusting screw. There was a problem with unstable distribution performance.

The present invention was made in order to eliminate such conventional problems, and it promotes mixing of fuel and air before distribution, and evenly distributes a mixture with a uniform air-fuel ratio to each intake passage. The basic object of the present invention is to provide a fuel distribution device for a multi-cylinder engine that can improve combustion performance and drivability during idling operation or low-load operation near idling.

Therefore, in the present invention, an independent intake passage is provided for each cylinder or each cylinder group, the idle fuel passage is opened in the bypass air passage that bypasses the throttle valve, and the bypass air passage is provided downstream of the bypass air passage. An expansion chamber having a sufficiently large cross-sectional area compared to the cross-sectional area is provided, and the opening direction of the bypass air passage is set to be almost perpendicular to the bottom wall of the expansion chamber, so that it opens at the bottom of the bypass air passage. The fuel led out from the idle port and the air flowing down the bypass air passage collide directly with the bottom wall of the expansion chamber, and the resulting vortex flow promotes mixing and forms a mixture with a uniform air-fuel ratio. In addition, the air-fuel mixture is distributed directly from the enlarged chamber to each intake passage through an independent small-diameter distribution 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 or cylinder groups (not shown), 3 is a bypass air passage that bypasses the throttle valve, and 4 is an air bypass passage 3.
An enlarged chamber with a circular cross section, which communicates with the downstream of the air passages 1 and 2, and whose center is located on the symmetry center line have Reference numerals 5 and 6 denote distribution passages with small diameter cross sections that communicate the enlarged chamber 4 and the intake passages 1 and 2, respectively; 7 denotes communication passages that communicate the intake passages 1 and 2 with each other downstream of the distribution passages 5 and 6; The communication passage 7 eliminates the unbalance of negative pressure between the intake passages 1 and 2 caused by poor sealing when the throttle valve is fully closed, and stabilizes the flow of fuel from the distributors 5 and 6.

In the bypass air passage 3, an idle port 8 serving as an idle fuel passage is opened slightly upstream of the part where the passage 3 communicates with the enlarged chamber 4, and a part of the fuel supplied from the slow system fuel passage 9 is opened. Bypass air passage 3 is supplied. The amount of fuel flowing out of the idle port 8 is adjusted by a well-known idle adjuster screw 10, and the amount of bypass air in the bypass air passage 3 is adjusted by a bypass air adjuster screw 11.

Moreover, the bypass air passage 3 is connected to the expansion chamber 4,
The bypass air passage opens near the outer periphery on the center line of symmetry
The fuel and air are set substantially perpendicular to the bottom surface 4a so that the fuel and air collide directly with the bottom surface 4a, and the resulting vortex flow promotes mixing of the fuel and air.

Further, the distribution passages 5 and 6 are connected to the bypass air passage 3.
In order to prevent the fuel and air led out into the expansion chamber 4 from being mixed and short-circuited into the intake passages 1 and 2 and to ensure their residence time, the area of the passage is kept in an idling state. It is preferable that the opening position for the expansion chamber 4 be as far away as possible from the communication portion between the bypass air passage 3 and the expansion chamber 4. Further, the opening positions of the distribution passages 5 and 6 are preferably symmetrical with respect to the center line of symmetry X of the intake passages 1 and 2, and the lengths of the passages are also preferably equal.

The expansion chamber 4 also includes a two-layer insulator 1 interposed between the carburetor 12 and the intake manifold 13.
Insulator 14 on the upper side of the figure among 4 and 15
If the communicating path 7 is formed by using the lower insulator 15, the processing can be made easier.

In addition, in FIG. 2, 16 is the distribution passage 5 of the intake passage 1.
The throttle valve 17 provided upstream of the throttle valve 16 is a slow port that communicates with the slow system fuel passage 9 and opens both upstream and downstream when the throttle valve 16 is fully closed.

As described above, the enlarged chamber 4 is provided downstream of the bypass air passage 3, and the small-diameter distribution passage 5 communicates between the enlarged chamber 4 and each intake passage 1, 2, respectively.
6, the bypass air passage 3 is adjusted by the bypass air adjusting screw 11.
The air flowing down is the idle adjustment screw 1
It flows into the expansion chamber 4 with idle fuel adjusted by 0. The air and fuel that flowed in at this time collide with the bottom wall 4a of the enlarged chamber 4 facing each other, and mixing is promoted by the resulting vortex flow.

Therefore, since the air-fuel mixture with a uniform air-fuel ratio is held in a stagnation state in the enlarged chamber 4, the air-fuel mixture with a uniform air-fuel ratio is supplied to each intake passage 1, 2 via the distribution passages 5, 6. is supplied, and it is possible to prevent variations in combustion due to variations in fuel between cylinders, that is, variations in air-fuel ratio. In this case, even if there are variations in the opening degree of the throttle valve, the intake negative pressure acting on both the distribution passages 5 and 6 is maintained at approximately the same pressure by the communication passage 7. The distribution characteristics are more stable.

As described above, the present invention provides an independent intake passage for each cylinder or each cylinder group, opens the idle fuel passage to the bypass air passage that bypasses the throttle valve, and forms an enlarged chamber downstream of the bypass air passage. On the other hand, the expansion chamber and each intake passage are directly communicated with each other through independent small-diameter distribution passages, and the opening direction of the bypass air passage is set to be perpendicular to the bottom wall of the expansion chamber. According to this invention, it is possible to sufficiently promote the mixing of bypass air and idle fuel in the expansion chamber, and as a result, the air-fuel mixture with a uniform air-fuel ratio accumulated in the expansion chamber can be evenly distributed to each intake passage. The combustibility of the cylinder can be improved, and the drivability, fuel efficiency, and emission performance of the engine can be improved.
In addition, according to the present invention, by directly communicating the enlarged chamber and each intake passage through independent small-diameter distribution passages, a branch point of the distribution passage is provided downstream of the enlarged chamber to allow mixing into each intake passage. Compared to systems that distribute air-fuel mixture, there is no need to consider the shape of the area near the branch point of the distribution path as a factor in determining the ratio of air-fuel mixture distribution, and it is easier to distribute the air-fuel mixture evenly. be.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the vicinity of an insulator of a carburetor according to an embodiment of the present invention, and FIG.
FIG. 1, 2... Intake passage, 3... Bypass air passage, 4... Expansion chamber, 5, 6... Distribution path, 8... Idle port, 4a... Bottom wall of expansion chamber.

Claims (1)

[Claims] 1. An independent intake passage is provided for each cylinder or each cylinder group, and an idle fuel passage is opened in the bypass air passage that bypasses the throttle valve, and the air-fuel mixture in the bypass air passage is distributed downstream of each throttle valve. In a multi-cylinder engine in which air is distributed to intake passages, an enlarged chamber is formed downstream of the idle fuel passage opening of the bypass air passage, while the enlarged chamber and each of the intake passages are separated from each other by independent small-diameter distribution passages. Communicate directly with
A fuel distribution device for a multi-cylinder engine, characterized in that the opening direction of the bypass air passage is set to be substantially perpendicular to the bottom wall of the enlarged chamber.