JPH02146250A - Intake manifold - Google Patents

Abstract

PURPOSE:To improve the distribution property of fuel and the suction efficiency of the mixture gas by setting the junction of a main passage and branch passages with a round, and arranging the lower end of the junction at the position lower than the upper surface of the starting end of the branch passages. CONSTITUTION:In an intake manifold, a main passage 2 is provided at the inner surface of a collecting part 1 arranged in the up and down direction, and the main passage 2 is branched into branch passages 4 provided inside plural branch pipes 3. In this case, the junction 9 of the main passage 2 and the branch passage 4 is set with a round, forming a relatively gentle curved surface. And the lower end 9a of the junction 9 is arranged at the position lower than the upper surface 4b of the starting end 4a of the branch passages 4. And in the same way, the lower end 9a of the junction 9 and the upper sur face 4b at the starting end 4a of the branch passages 4 are continued in a gentle curved surface. As a result, the lower end 9a of the junction 9 can be functioned as an edge, and the distribution property of the fuel is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to an intake system that distributes air-fuel mixture to a plurality of cylinders.
It concerns manifolds.

[Prior Art] In intake manifolds in which a carburetor or the like is connected to the upper end of the collecting part, fuel often adheres to the wall surface of the main passage within the collecting part when the engine is cold or in a low speed rotation range.

Due to the swirling flow of intake air generated downstream of the throttle valve, the liquid fuel swirls on the wall of the main passage and is carried to the branch, where it flows along the wall of the branch and tends to be distributed to each branch passage. There is. As a result, there is an imbalance in the fuel distributed from the main passage to each branch passage, and the amount of fuel distributed to each cylinder becomes uneven, causing torque fluctuations, as well as in the low speed range of the engine. This increases engine vibration, which is a factor in deteriorating drivability.

In order to deal with such problems, as a prior art of the present invention, for example, as shown in Japanese Patent Laid-Open No. 59-215958, a constrictor is provided protruding from the branch part to collect the air-fuel mixture in the center. Some systems improve the fuel distribution performance by diffusing the air-fuel mixture.

By the way, depending on the form of the branch part between the main passage and the branch passage,
As shown schematically in FIG. 3, there is a tendency for the torque characteristics to change. For example, if the branch is made into an edge, the torque will gradually change (see line a), and if the branch is rounded and curved, the torque tends to increase in a certain engine rotation range (see line b). If the dimension from the inlet of the carburetor etc. to the lower end of the main passage is lengthened, as schematically shown in Figure 4, the region where the torque increases will shift to the lower engine speed (rntn valley line), and the above When the dimensions are shortened, the region where the torque is increased tends to shift to the higher engine speed (see the m2 line).

[Problems to be Solved by the Invention] However, in the case of improving the distribution of fuel, etc., the configuration shown in the prior art has a configuration in which the throttle protrudes from the wall surface of the passage.

Therefore, although it is possible to effectively prevent liquid fuel from directly flowing from the main passage along the wall surface into the branch passage, the cross-sectional shape of the passage changes suddenly, resulting in a decrease in suction efficiency.

On the other hand, if the branch part is rounded and curved, sudden changes in the cross-sectional shape of the passage can be avoided and suction efficiency can be improved. Since the fuel tends to adhere to the wall surface of the fuel and flow directly into the branch passage, it becomes difficult to avoid a decrease in fuel distribution.

Further, when the branch portion is curved as described above, in the conventional case, it is common that there is a monotonous corner from the lower end of the main passage to the starting end of the branch passage. Therefore, in order to shift the torque-up region that occurs in a specific engine speed range to the low-speed rotation side and improve drivability in the low-speed rotation range, it is necessary to increase the vertical dimensions of the gathering part, etc. This will cause the engine to rise.

An object of the present invention is to provide an intake manifold that can solve the above problems all at once.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configuration.

That is, the intake Φ manifold according to the present invention is an intake manifold in which a main passage provided in the vertical direction is branched into a plurality of branch passages, in which the branch part between the main passage and the branch passage is rounded and ,
It is characterized in that the lower end of the branch part is located at a lower position than the upper surface at the starting end of the branch passage.

[Operation] According to such a configuration, the main passage and the branch passage can be connected by a gently curved surface, so that sudden changes in the cross-sectional shape of the passage can be avoided. The lower end of the branch part is at a lower position than the upper surface at the starting end of the branch passage, and is connected to the upper surface by an ascending slope. Therefore, the vertical dimension of the main passage can be increased without increasing the vertical dimension of the collecting portion, etc., and it becomes difficult for the fuel that has flowed down the wall surface of the main passage to directly flow into the branch passage.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2.

The intake manifold shown in the drawing has a main passage 2 inside a gathering part 1 provided in the vertical direction, and the main passage 2 is branched into branch passages 4 provided in a plurality of branch pipes 3. It has come to be used in the intake systems of automobiles, etc.

A carburetor 7 is connected to a flange 5 provided at the upper end of the gathering portion 1 via an insulator 6, and an air cleaner 8 is attached to the upper end of the carburetor 7.

The main passage 2 is formed vertically, and its upper end 2
A is opened at the upper end surface 5a of the flange 5. The branch passage 4 is formed by branching the main passage 2 to both left and right sides, and communicates with each cylinder (not shown). The branch portion 9 between the main passage 2 and each branch passage 4 is rounded and has a relatively gentle curved surface, and its lower end 9a is lower than the upper surface 4b at the starting end 4a of each branch passage 4. It's in position. Similarly, the lower end 9a of this branch portion 9 and the upper surface 4b at the starting end 4a of each branch passage 4 are also connected by a gently curved surface.

According to such a configuration, the branching portion 9 between the main passage 2 and each branch passage 4 extends downward from the wall surface of the main passage 2, and then becomes an upward slope and connects each branch passage. It becomes a form that leads to 4. Therefore, the liquid fuel that has flowed from the wall surface of the main passage 2 to the wall surface of the branch part 9 becomes difficult to flow directly into each branch passage 4 from the lower end 9a of the branch part 9. In other words, the lower end 9a of the branch portion 9 functions as an edge, improving fuel distribution. Therefore,
It is possible to effectively suppress torque fluctuations, engine vibrations, etc. in the low speed rotation range of the engine, and improve drivability.

Moreover, the branch portion 9 has a gently curved surface and its cross-sectional shape gradually changes. Therefore, the intake resistance is suppressed, the air-fuel mixture intake efficiency is increased, and the torque etc. can be reliably increased. Since the lower end 9a of the branch part 9 is located at a lower position than the upper surface 4b of the starting end 4a of each branch passage 4, the dimension m from the inlet of the carburetor 7 to the lower end 9a is the same as that of the main passage and the branch passage. The length can be reliably increased compared to the case where the two are simply connected by a curved surface. Therefore, without increasing the vertical dimensions of the gathering part 1 or the carburetor 7, the region where the torque is increased can be shifted to the lower engine speed. ability can be increased.

In addition, in the above embodiment, the intake manifold 1 in which the main passage branches into two directions was described, but the present invention
It can also be suitably employed when the main passage is branched into three or more directions.

Further, the present invention can be effectively applied not only to the case where a carburetor is used but also to the case where a fuel injection valve is mounted on the upstream side of the gathering part.

[Effects of the Invention] According to the present invention configured as described above, it is possible to reliably improve the fuel distribution performance and the intake efficiency of the air-fuel mixture, and also to effectively shift the torque increase region to the low engine rotation speed region. Therefore, it is possible to effectively suppress torque fluctuations, engine vibrations, etc., and provide an intake manifold that is easy to use and can improve drivability in the low-speed rotation range of the engine.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, with FIG. 1 being a partially sectional schematic front view and FIG. 2 being a schematic plan view of an intake manifold. 3 and 4 show a conventional example, FIG. 3 is a diagram schematically showing a state of torque change, and FIG. 4 is a diagram schematically showing a state of change of torque. 2...Main passage 4...Branch passage 4a...Starting end 4b...Top surface 7...Carburizer 9...Branch part 9a...Lower end 1st port 2nd figure

Claims (1)

[Claims] In an intake manifold in which a main passage provided in the vertical direction is branched into a plurality of branch passages, the branch part between the main passage and the branch passage is rounded, and the lower end of the branch part is connected to the branch passage. An intake manifold characterized by being located lower than the top surface at the starting end.