JPS5828411B2 - Intake system for multi-cylinder internal combustion engine - Google Patents

Description

[Detailed description of the invention] The present invention relates to an intake system for a multi-cylinder internal combustion engine.

Usually, particularly in gasoline engines, the intake port is formed in a port shape with small fluid resistance in order to increase charging efficiency during high-speed, high-load operation and thereby obtain sufficient output.

However, with such a port shape, during high-speed, high-load operation, a naturally occurring and quite strong turbulence will occur in the combustion chamber, so the combustion speed will be sufficiently increased; Therefore, there is a problem that the combustion rate cannot be sufficiently increased.

There are methods to generate strong turbulence during low-speed, low-load operation by making the intake port helical or by using a shroud valve to forcefully generate a swirling flow in the combustion chamber. There is a problem in that filling efficiency during high-speed, high-load operation decreases due to increased resistance to airflow.

On the other hand, US Pat. No. 3,505,983 discloses an internal combustion engine in which throttle valves are provided in the intake pipes of each cylinder, and the intake pipes downstream of each throttle valve are communicated with each other via a common communication path.

In this internal combustion engine, the air-fuel mixture in each intake passage flows back and forth through a common communication passage, so that the air-fuel ratio of the air-fuel mixture supplied to each cylinder can be made uniform.

However, in this internal combustion engine, the purpose of the common communication passage is simply to equalize the air-fuel ratio of the air-fuel mixture in each intake pipe, and the air-fuel mixture does not flow out at high speed into each intake pipe from the common communication passage. Therefore, it is difficult to generate strong turbulence during low-speed, low-load operation.

SUMMARY OF THE INVENTION An object of the present invention is to provide an intake system for an internal combustion engine that has a simple structure but can ensure high charging efficiency during high-speed, high-load operation, and can also generate strong turbulence in the combustion chamber when necessary.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, 1 is the main body of the engine, and 2a. 2b, 2c
, 2d are the 1st cylinder, 2nd cylinder, 3rd cylinder, 4th cylinder, 3a, 3b, 3c, 3d are intake valves, 4a, 4b,
4c, 4d are exhaust valves, 5a s5b, 5c, 5d are intake ports, 5a, 6b.

6c and 6ct indicate exhaust ports, respectively.

As shown in Figures 1 and 2, each intake port) 5a
.

5b, 5c, and 5d are formed in a helical shape.

FIG. 2 shows a sectional view of the second cylinder 2b taken along the line ■-■ in FIG. 1, and in FIG. 2, 7 is a cylinder block;
8 is a piston that reciprocates within the cylinder block T, 9 is a cylinder head fixed on the cylinder block 7, 1
0 indicates the combustion chamber of the second cylinder.

Although not shown in the figure, an ignition plug is disposed within the combustion chamber 10.

Referring to FIGS. 1 and 2, a pair of carburetor housings 11.12 are attached to engine body 1, and each carburetor housing 11.12 is provided with a variable venturi type carburetor body 13.14.

Each mixture passage 15.1 in the carburetor housing 11.12
6 is branched into a pair of mixture branch passages 17.18:19.20, respectively, and these mixture branch passages 17.1B, 19.2
0 are connected to helical intake ports 5a, 5b, 5c, and 5d, respectively.

Further, carburetor throttle valves 21, 22, 23° 24 are arranged in each of these mixture branch passages 17, 18, 19, 20, respectively.
4 are connected to each other by a link mechanism and are controlled to open the valves at the same time, but this is simplified in FIG. 1 and shown as being fixed to a common throttle shaft 25.

As shown in FIG. 2, the variable venturi carburetor body 13 has a movable suction piston 26, a movable needle 27 and a metering jet 28, and as is well known, the movable suction piston 26 is located upstream of the throttle valve 22. In addition, the suction piston 26 moves up and down so that the negative pressure in the air-fuel mixture passage 15 downstream of the suction piston 26 is always maintained at a constant pressure.

A common communication passage 29 extending in the longitudinal direction of the engine body 1 is provided below each throttle valve 21, 22, 23, 24,
From this common communication path 29 to each helical intake port 5a, 5
Four communication branches 30a, 30 leading into b, 5c, 5d
b, 30c.

30d is formed within the cylinder head 9.

Each of these communication branches 30a, 30b, 30c, 30
d is a helical intake port 5a near the back of the corresponding intake valve
, 5b, 5c, and 5d are opened tangentially toward the periphery of the cross section of the helical intake port on the inner wall surface, and each communication branch path 30a, 30b, 30c.

30d is directed toward the gap formed between the intake valve and its valve seat when each intake valve is opened.

Figure 4 shows the intake ports of each cylinder during engine operation) 5a,
5b, 5c, and 5d are shown.

In FIG. 4, the horizontal axis θ indicates the crank angle, and the vertical axis indicates the pressure in the helical intake port near the back surface of the intake valve bulk (hereinafter referred to as intake port pressure), and each reference line A, B , C, and D indicate atmospheric pressure.

In addition, curves E, F, G, and H are for each helical intake port 5a.
, 5b, 5c, and 5d, and each arrow I, J shows the change in the pressure inside the intake port.

K and L are each intake valve 3a of the corresponding helical intake port,
3b, 3c, and 3d show the opening periods.

Focusing on cylinder No. 61 in Fig. 4, the pressure inside the intake port becomes positive pressure in the crank angle range M immediately after the intake valve opens, and then the pressure inside the intake port becomes positive pressure in the crank angle range N when the piston is descending. It can be seen that the pressure in the intake port becomes negative pressure, and then when the piston starts to rise, the pressure in the intake port becomes positive pressure again.

Therefore, if we pay attention to the crank angle range P of the No. 1 and No. 2 cylinders in Fig. 4, we can see that the pressure inside the intake port 5a of the No. 1 cylinder is negative, while the pressure inside the intake port 5b of the No. 2 cylinder is negative. It can be seen that the pressure is positive.

Furthermore, in the crank angle range Q of the 2nd and 4th cylinders, when the pressure inside the 2nd cylinder's intake port 5b is negative, the pressure inside the 4th cylinder's intake port 5d becomes positive, and the pressure inside the 3rd cylinder In the crank angle range R of the 4th cylinder, when the pressure inside the 4th cylinder's intake port 5b is negative pressure, the pressure inside the 3rd cylinder's intake port 5C is positive pressure, and the crank angle of the 1st and 3rd cylinders is In the range S, the intake port of the 3rd cylinder) 5c
It can also be seen that when the internal pressure is negative, the internal pressure of the intake port 5a of the No. 1 cylinder becomes positive.

Therefore, if we pay attention to the 1st and 2nd cylinders, the helical intake port of the 1st cylinder will occur in the first half of the intake stroke in the 1st cylinder.
Due to the pressure difference between the inside of the helical intake port 5a and the inside of the helical intake port 5b of the second cylinder, the air-fuel mixture is supplied from the intake port 5b to the helical intake port 5a via the communication branch 30b, the common communication passage 29, and the communication branch 30a. I understand that.

Similarly, during the intake stroke of the No. 2 cylinder, the air-fuel mixture is supplied from the helical intake port (Sb) of the No. 4 cylinder to the helical intake port (Sb) via the communication branch path 30d, the common communication path 29, and the communication branch path 30b. During the intake stroke of cylinder No. 3, the air-fuel mixture is supplied from the helical intake port of cylinder No. 3) 5c to the helical intake port of cylinder No. 4) 5d, and during the intake stroke of cylinder No. 3, the mixture is supplied from the helical intake port of cylinder No. 1) 5a. The air-fuel mixture is supplied into the helical intake port 5c of the third cylinder.

In this way, during the intake stroke of each cylinder, the air-fuel mixture is injected at high speed from the corresponding communication branches 30a, 30b, 30c, 30d into the respective henocal intake ports 5a, 5b, 5c, 5d due to the pressure difference within the intake ports. I will do it.

During engine operation, the mixture formed in each carburetor body 13.14 is supplied into each helical intake port 5a, 5b, 5C15d via a respective mixture passage 15.16.

Now, assuming that the No. 2 cylinder 2b is in the intake stroke, the air-fuel mixture that has flowed into the helical intake port 5b advances along the inner wall surface of the helical intake port, turning as shown by arrow Z in Fig. 3. It flows into the combustion chamber 10 and generates a swirling flow as shown by the arrow W in the combustion chamber 10.

On the other hand, during the intake stroke, as described above, the air-fuel mixture is ejected from the communication branch 30b into the helical intake port 5b at high speed.

Further, as described above, since the communication branch 30b is oriented toward the gap formed between the intake valve 3b and its valve seat, the air-fuel mixture ejected from the communication branch 30b passes through the gap and enters the combustion chamber 10.
The swirling flow W generated in the combustion chamber 10 is increased by this jetted air-fuel mixture.

As a result, a strong swirling flow is generated within the combustion chamber 10.

Since a pressure difference occurs between the helical intake ports 5a, 5b, 5c, and 5a regardless of the engine load, the communication branches 30a and 30b are connected regardless of the engine load.

The air-fuel mixture is ejected from 30C and 30d, and the swirling flow W in the combustion chamber 10 is increased by this ejected air-fuel mixture.

Furthermore, as is generally known, forming the intake port in a helical shape reduces the filling efficiency during high-speed, high-load operation, but in the present invention, a large amount of air-fuel mixture is communicated even during high-speed, high-load operation. Branch roads 30a, 30b, 30
c, each helical intake port via 30d) 5a*5b
j5C.

Since the fuel is supplied within 5d, a decrease in filling efficiency can be avoided.

Furthermore, as shown in FIGS. 1 and 2, by arranging the carburetor throttle valves 21, 22, 23, and 24 near the air-fuel mixture inlet of each helical intake port, the airflow from the combustion chamber into the helical intake port is reduced. Since the positive pressure caused by the return is maintained as it is without being reduced, the pressure difference in each communicating branch pipe is maintained at a large pressure difference for an even longer period of time, and thus a larger amount of mixing is achieved. Since air is supplied from the communication branches 30a, 30b, 30c, and 30d into the respective helical intake ports)sa, 5bjscj5d, the filling efficiency is rather improved.

As mentioned above, even if a helical intake port is used, a decrease in filling efficiency during high-speed, high-load operation can be avoided.
In addition, a swirling flow of the air-fuel mixture is actively formed at the helical intake port, and the swirling flow within the combustion chamber generated by this swirling flow is amplified by the air-fuel mixture jetting out from the communication branch, creating a strong swirling flow inside the combustion chamber. This makes it possible to significantly increase the combustion rate particularly during low speed, low load and low speed, high load operations while ensuring high charging efficiency during high speed, high load operation.

Furthermore, in the present invention, it is necessary to provide a throttle valve at the entrance of the intake port in order to prevent positive pressure from being blown back from the combustion chamber into the helical intake port, but these throttle valves are of the variable venturi type. It also acts as a throttle valve for the carburetor.

Therefore, there is an advantage that the structure is simplified because there is no need to provide a separate new throttle valve for each variable venturi type carburetor.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an internal combustion engine according to the present invention, and FIG.
FIG. 3 is a cross-sectional side view taken along line I--1 in FIG. 2, and FIG. 4 is a graph showing pressure changes in each intake port. 3a, 3b, 3c, 3d = intake valve, 4a, 4b. 4c, 4d-exhaust valve, 5a, 5b, 5c,
5d--Intake port, 11.12... Carburetor housing, 13.14... Carburetor body, 21, 22.2
3゜24...Carburizer throttle valve, 29...Common communication passage, 30a, 30b, 30c, 30d--Series communication branch passage.

Claims (1)

[Claims] 1. Each variable venturi type carburetor is provided with at least one pair of throttle valves, and the mixture passage of each variable venturi type carburetor is branched into at least one pair of mixture branch passages, and the mixture branch passage is connected to the cylinder head. The throttle valve is connected to a corresponding intake port formed in the air-fuel mixture branch passage, and the throttle valve is arranged in each mixture branch passage, and a communication branch passage is provided for each intake port separately from the intake port. One end of the passage is opened on the inner wall surface of the intake port near the back surface of the intake valve shank, and the other end of each communication branch is connected to a common communication passage, and the common communication passage is connected to the above-mentioned communication branch. An intake system for a multi-cylinder internal combustion engine that communicates only with the intake port through the intake port.