JPS589255B2 - 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, if such a port shape is used, 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, but during low-speed, low-load operation, sufficient turbulence will not occur within the combustion chamber. First, there is a problem that the combustion rate cannot be sufficiently increased.

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

On the other hand, U.S. Patent No. 3,505,983 discloses that a throttle valve is provided in the intake pipe of each cylinder, and the intake pipes downstream of each throttle valve are communicated with each other through a common communication path. An internal combustion engine is disclosed.

In this internal combustion engine, the air-fuel mixture in each intake passage moves 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.

An object of the present invention is to provide an intake system for an internal combustion engine that can ensure high charging efficiency during high-speed, high-load operation even if the intake port is formed in a helical shape, and can also generate strong turbulence in the combustion chamber when necessary. be.

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

Referring to Figure 1, 1 is the engine body, 2a, 2b, 2c
, 2d are the 1st cylinder, 2nd cylinder, 3rd cylinder, and 4th cylinder, respectively; 3a, 3b, 3c, and 3d are intake valves; 4a, 4b, 4c
, 4d are exhaust valves, 5a, 5b, 5c, and 5d are intake ports, and sa, sb, 6ct, and 6d are exhaust ports, respectively.

As shown in FIGS. 1 and 2, each intake port 5a
, 5b, 5c, and 5d are formed in a helical shape.

FIG. 2 shows a side sectional view of FIG.
1 shows a cylinder block, 8 a piston reciprocating within the cylinder block 7, 9 a cylinder head fixed on the cylinder block 7, and 10 a combustion chamber.

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

Referring to FIGS. 1 and 2, an intake manifold 11 is fixed to the engine body 1, and a carburetor 13 having a carburetor throttle valve 12 at the inlet of the intake manifold 11.
is installed.

On the other hand, each manifold branch pipe 1 4 of the intake manifold 11
, 15, 16.17 are the corresponding intake ports 5a, 5b,
Connected to 5c and 5d.

In these manifold branch pipes 14, 15, 16, 17, second throttle valves 21, 22, 23, 24 are provided near the air-fuel mixture inlet of each intake port 5a, 5b, 5c, 5d, respectively. Second throttle valve 21, 22, 23
, 24 are fixed on a common throttle shaft 25.

As shown in FIG. 2, an arm 26a fixed to the throttle shaft 26 of the carburetor throttle valve 12 and an arm 25a fixed to the throttle shaft 25 are connected to each other by a link 27, whereby the second throttle valve 21,
22, 23, and 24 open as the carburetor throttle valve 12 opens.

A common communication passage 29 extending in the longitudinal direction of the engine body 1 is provided below each of the second throttle valves 21, 22, 23, 24, and the common communication passage 29 is connected to each helical intake port 5a.
, 5b, 5c, 5d, four communication branches 30a,
30b, 30c, and 30d are formed within the cylinder head 9.

These communication branches 30a, 30b, 30c, 30d are connected to helical intake ports 5a, 5b near the back of the corresponding intake valve.
, 5c, sd are opened tangentially toward the peripheral direction of the helical intake port cross section on the inner wall surface, and each communication branch path 30a
, 30b, 30c, and 30d are directed toward the gap formed between the intake valve and its valve seat when each intake valve is opened and closed.

On the other hand, as shown in FIGS. 1 and 2, the central part of the common communication passage 29 is connected to the intake manifold gathering part 11a via a sub-intake passage 35, and an on-off control valve 36 is provided in the sub-intake passage 35. is inserted.

An arm 38 is fixed to a valve shaft 37 of the opening/closing control valve 36, and the tip of the arm 38 is connected to a diaphragm 41 of a negative pressure diaphragm device 40 via a control rod 39.

This negative pressure diaphragm device 40 includes a negative pressure chamber 42 separated from the atmosphere by a diaphragm 41.
A compression spring 43 for pressing the diaphragm is inserted into the spring 2 .

This negative pressure chamber 42 is connected through a negative pressure conduit 44 into the intake manifold gathering portion 11a.

When the engine is operating at a low load, that is, when the negative pressure inside the intake manifold gathering part 11a is large, the diaphragm 41 is pressed against the compression spring 4.
3, the opening/closing control valve 36 closes the auxiliary intake passage 35 as shown in FIG.

On the other hand, when the engine is operating under high load, that is, the intake manifold gathering section 1
When the negative pressure inside 1a is small, the diaphragm 41 rises due to the spring force of the compression spring 43, so the opening/closing control valve 3
6 fully opens the sub-intake passage 35.

Figure 3 shows the intake ports of each cylinder during engine operation.
Pressure changes within a, 5b, 5c, 5d are shown.

In Fig. 3, the horizontal axis θ indicates the crank angle, and the vertical axis indicates the pressure inside the helical intake port near the back of the intake valve bulk (hereinafter referred to as intake port internal pressure), and each reference line A, B , O, and D indicate atmospheric pressure.

In addition, curves E, F, G, and H are for each helical intake port sa.
, 5b, 5c, and 5d, and each arrow I, J, K, and L indicates the opening period of each intake valve 3a, 3b, 3c, and 3d of the corresponding helical intake port.

Focusing on the No. 1 cylinder in Fig. 3, the pressure inside the intake port becomes positive in the crank angle range M immediately after the intake valve opens, and then in the crank angle range N where the piston is descending, the pressure inside the intake port becomes positive. It can be seen that when the pressure becomes negative and then the piston starts to rise, the pressure inside the intake port becomes positive pressure again.

Therefore, if we pay attention to the crank angle range P of the first and second cylinders in FIG. 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 intake port 5b of the 2nd cylinder is negative, the pressure inside the 4th cylinder's intake port 5d is positive; In the crank angle range R of the cylinders, when the pressure inside the intake port 5b of the No. 4 cylinder is negative pressure, the pressure inside the intake port 5c of the No. 3 cylinder becomes positive pressure, and in the crank angle range S of the No. 1 and No. 3 cylinders. is intake port 5c of cylinder 3
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, when the opening/closing control valve 36 closes the auxiliary intake passage 35, such as during low engine load operation, during the first half of the intake stroke of the first cylinder, the inside of the helical intake port 5a of the first cylinder and the second cylinder are closed. It can be seen that the air-fuel mixture is supplied from the intake port 5b into the helical intake port 5a via the communication branch 30b, the common communication passage 29, and the communication branch 30a due to the pressure difference between the helical intake port 5b and the helical intake port 5b.

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

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

During low-load engine operation, the air-fuel mixture formed in the carburetor 13 is supplied into each helical intake port 5a, sb, 5c, 5d via each intake manifold branch pipe 14, 15, 16, 17.

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, and then rotates along the helical inner wall surface of the intake port. 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.

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 flow from the combustion chamber to the helical intake port is reduced. Since the positive pressure caused by blowback is maintained as it is without being reduced, the pressure difference in each communicating branch pipe is maintained under a large pressure difference state for an even longer period of time, resulting in a large amount of mixing. Air can be supplied into each helical intake port 5a, 5b, 5c, 5d from the communication branches 30a, 30b, 30c, 30d.

On the other hand, during high-load engine operation, the on-off control valve 36 fully opens the auxiliary intake passage 35 as described above, so that in addition to the air-fuel mixture supplied into the combustion chamber 10 via the helical intake boat, the auxiliary intake passage 35 and the common communication Passage 29 and communication branch 30a,
The air-fuel mixture is further supplied into the combustion chamber 10 from 30b, 30c, and 30d.

Therefore, even if a helical intake port is used, high filling efficiency can be ensured.

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 during low-load operation while ensuring high charging efficiency during high-speed, high-load operation.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an internal combustion engine according to the present invention, and FIG.
The cross-sectional side view of the figure and FIG. 3 are graphs showing pressure changes within each intake port. 3a, 3b, 3c, 3d-=--
- Intake valve, 4a, 4b, 4c, 4d - Exhaust valve, 5 a
s 5 b 1 5 c) 5d... Intake port, 12... Carburetor throttle valve, 21, 2
2, 23, 24... Second throttle valve, 29.
...Common communication path, 30a, 30b, 30c, 30
a......Connecting branch road.

Claims (1)

[Claims] 1. Attach a carburetor equipped with a carburetor throttle valve to the inlet of the intake manifold, and connect the branch pipes of the intake manifold to corresponding intake ports formed in the cylinder head to control intake air near the inlet of the intake port. A second throttle valve is arranged in each of the manifold branch pipes, a communication branch is provided for each intake port separately from the intake port, and one end of each communication branch is connected to the intake port near the back of the intake valve bulk. The other end of each communication branch is opened on the wall surface and connected to a common communication passage, and the common communication passage is inserted into the intake manifold between the carburetor throttle valve and the second throttle valve via a sub-intake passage. A multi-cylinder connected to each other, an opening/closing control valve responsive to engine load is inserted in the sub-intake passage, and the opening/closing control valve is opened when the engine load becomes larger than a predetermined constant load. Intake system for internal combustion engines.