JPS5813084Y2 - Intake system for multi-cylinder internal combustion engine - Google Patents

Description

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

Usually, especially 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 into a hexagonal shape or by using a shroud valve to forcefully 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.

Therefore, in order to increase the combustion rate during low-speed, low-load operation while ensuring high charging efficiency during high-speed, high-load operation, the intake port should be formed with a port shape that has low fluid resistance, and the combustion chamber should be closed during low-speed, low-load operation. It is necessary to create a strong disturbance.

Furthermore, as a method of improving combustion during low-speed, low-load operation, in addition to generating strong turbulence within the combustion chamber, there is also a method of promoting vaporization of the fuel.

That is, during low-speed, low-load operation, the flow rate of air flowing through the venturi section of the carburetor is slow, and therefore the relative speed between the injected fuel and the air flow is slow, making it impossible to atomize the fuel sufficiently. A large amount of fuel is supplied into the combustion chamber in liquid form, which is one of the causes of worsening combustion and exhaust emissions.

In order to solve these problems, an auxiliary intake passage is branched from the mixture passage upstream of the carburetor throttle valve and connected to an intake port near the intake valve downstream of the carburetor throttle valve. Internal combustion engines equipped with a secondary throttle valve have been proposed.

In this internal combustion engine, when the engine is operated under low load, the air-fuel mixture is supplied into the combustion chamber through the auxiliary intake passage, which has a small cross-sectional area, so the air-fuel mixture jets out at high speed from the auxiliary intake passage, causing strong turbulence within the combustion chamber. Moreover, there is an advantage that vaporization of the fuel can be promoted while the air-fuel mixture flows at high speed in the sub-intake passage.

However, when there is at least a pair of carburetors for supplying heat to separate cylinders, if a sub-intake passage and a sub-throttle valve are provided for each carburetor, the distribution of fuel between the cylinders will be uneven. Moreover, there is a problem that the structure becomes complicated.

This invention is an intake system with a simple structure that can generate strong turbulence in the combustion chamber during low-load, low-speed operation while ensuring high charging efficiency during high-load, high-speed operation, and can evenly distribute fuel between cylinders. Our goal is to provide the following.

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

Referring to FIG. 1 and FIG. 2, 1 is a cylinder block, 2 is a piston that reciprocates within the cylinder block 1,
3 is a cylinder head fixed on the cylinder block 1, 4 is a combustion chamber formed between the piston 2 and the cylinder head 3, 5 is an intake port, 6 is an intake valve, 7 is an exhaust port,
8 is an exhaust valve, 9 is an exhaust manifold, and 10 is a spark plug.

In Fig. 1, A, B, C, and D are cylinders 1 and 2, respectively.
Shows cylinder No. 3, cylinder No. 3, and cylinder No. 4.

As shown in FIG. 1, a pair of carburetor housings 11 and 12 are fixed to the cylinder head 3, and a variable venturi carburetor 1 is attached to each of these carburetor housings 11 and 12, respectively.
3.14 is installed.

As shown in FIG. 2, these variable venturi carburetors 13 have a suction piston 15, a movable needle 16 fixed to the suction piston 15, and a fuel metering jet 17 cooperating with the movable needle 16. As is well known, the suction piston 15 moves up and down so that the pressure difference across the suction piston remains approximately constant.

The mixture passages 18.19 formed in each carburetor housing 11.12 each have a pair of mixture branch passages 20.21:
22.23, a pair of mixture branch passages 20.21
are connected to the intake ports 5 of the first aromatic cylinder A and the second cylinder B, and the pair of mixture branch passages 22 and 23 are connected to the intake ports 5 of the third aromatic cylinder C and the fourth cylinder.

On the other hand, throttle valves 24 are arranged in each of these mixture branch passages 20, 21, 22, 23, and these throttle valves 24 are fixed to, for example, a common throttle shaft 25 so as to open in synchronization with each other. Ru.

As shown in FIGS. 1 and 2, each carburetor housing 1
A communication pipe 26 and a distribution passage 27 extending in the longitudinal direction of the cylinder head 3 are provided below 1° 12, and a communication passage 28 is formed within the communication pipe 26.

This communication channel 28 is connected on the one hand into the mixture channel 18 via an opening 29 and on the other hand into the mixture channel 19 via an opening 130.

The mixture passages 18, 19 are therefore connected to each other by the communication passage 28.

On the other hand, inside the cylinder head 3, each cylinder has an intake port ~l-5.
Four branch passages 31 are formed to connect the distribution passage 27 and the distribution passage 27, and an opening 32 of each branch passage 31 to the intake port 1-5 is formed.
is directed toward the gap formed between the intake valve 6 and its valve seat when the intake valve is opened.

Further, the central portion of the communicating passage 28 and the central portion of the distribution passage 27 are connected to each other via a single connecting passage 33, and a sub-throttle valve 34 is provided within this connecting passage 33.

A recirculation exhaust gas (hereinafter referred to as EGR) port 35 and an idle fuel supply port 36 are opened at the junction of the connection passage 33 and the distribution passage 27.

The EGR port 35 is connected to the EGR gas supply conduit 37 and the EGR port 35.
It is connected into the exhaust manifold 9 via an R gas flow control valve 38, while the idle fuel supply ports 1-36 are connected to the carburetor body 13 via an idle fuel supply conduit 39.

FIG. 3 shows changes in the opening degrees of the throttle valve 24 and the sub-slot valve 34.

In FIG. 3, the vertical axis θ indicates the throttle valve opening, and the horizontal axis indicates the amount of depression of the accelerator pedal.

In addition, in FIG. 3, the curve shows the sub-throttle valve 34, and the curve P shows the throttle valve 24.

It can be seen from FIG. 3 that the throttle valve 24 is kept fully closed when the accelerator pedal is depressed to a small extent, and the sub throttle valve 34 is kept fully open when the accelerator pedal is depressed beyond a certain level.

The throttle valve 24 and the sub-throttle valve 34 are connected to the accelerator pedal via a link mechanism (not shown) so as to satisfy the relationship shown in FIG.

During engine operation, when the amount of accelerator pedal depression is small, only the sub-throttle valve 34 opens as described above, so the air-fuel mixture formed in each carburetor main body 13 and 14 flows through the opening 2.
9.30 into the communication passage 28, and then ejected into the intake port 5 via the connection passage 33, the distribution passage 27 and each branch passage 31.

Note that there is EGR in the air-fuel mixture sent into the distribution passage 27.
EGR gas is supplied from port 35, and fuel is supplied from idle fuel supply port 36 during idling operation.

As shown in FIGS. 1 and 2, the cross-sectional areas of the distribution passage 27, the communication passage 28, and the branch passage 31 are small, and therefore the air-fuel mixture flows at high speed in these passages 27, 28, and 31. The vaporization of fuel is promoted.

Further, the EGR gas supplied from the EGR port 35 is mixed with the air-fuel mixture while flowing at high speed together with the air-fuel mixture in the distribution passage 27, and at the same time, the vaporization of the fuel supplied from the idle fuel supply port 36 is promoted. Become.

Next, the air-fuel mixture is injected into the intake port 5 from the branch passage 31 at high speed.As mentioned above, the opening 32 of the branch passage 31 is directed toward the gap formed between the intake valve 6 and its valve seat when the intake valve is opened. As a result, the air-fuel mixture ejected from the branch passage 31 flows into the combustion chamber 4 at high speed through the above-mentioned gap, and as a result, a strong gas flows into the combustion chamber 4 as shown by the arrow W in FIG. A swirling flow occurs.

As a result, the combustion rate is greatly increased, and thus stable combustion can be obtained.

As mentioned above, during low load operation, each carburetor main body 13.14
The air-fuel mixture formed in is collected in the common communication passage 28 and then distributed to each cylinder via the distribution passage 27, so even if the fuel supply amounts of these two carburetors are different, the fuel distribution is uniform. becomes.

Further, since the EGR gas is supplied to the downstream side of the sub-throttle valve 34 and the throttle valve 24, there is no risk of deposits of, for example, carbon contained in the EGR gas on these throttle valves 34, 24. Thus, smooth operation of these throttle valves 34, 24 can be ensured at all times.

When the accelerator pedal is depressed greatly, the throttle valve 24 opens as shown in FIG. 3, and most of the air-fuel mixture flows into the combustion chamber 4 through the intake port 5, which has low flow resistance. Thus, high filling efficiency can be ensured during high-load, high-speed operation.

Another embodiment is shown in FIGS. 4 and 5.

In this embodiment, a sub-distribution passage 40 is provided between the distribution passage 27 and the communication passage 28, and a sub-throttle valve is installed in a connection passage 41 that connects the central part of the sub-distribution passage 40 and the central part of the communication passage 28. 34 are provided.

Furthermore, as shown in FIG. 4, this sub-distribution passage 40 is connected via a communication port 42 to a distribution passage 27 located between the two branch passages 31 that communicate with the first aromatic cylinder A and the second cylinder B. 43, it is connected to the distribution passage 27 located between the two branch passages 31 that communicate with the third aromatic cylinder C and the fourth aromatic cylinder C.

Also, EGR port 35 and idle fuel supply port 3
6 opens into the connecting passage 41 downstream of the sub-throttle valve 34 .

In the embodiment shown in FIG.
GR gas and idle fuel distribution amount is EGR port 3
5 and the one furthest from the idle fuel supply port I/36
There is a danger that the amount will decrease in the aroma cylinders A and No. 4, and increase in the second cylinder B and the third aroma cylinder C, which are closer to them.

However, as shown in FIG. 4, a sub-distribution passage 40 is provided between the two branch passages 31 of the first aromatic cylinder A and the second cylinder B.
Furthermore, by supplying EGR gas and idle fuel between the branch passages 31 of the third aromatic cylinder C and the fourth cylinder, the distribution of EGR gas and idle fuel to each cylinder can be made uniform.

Still another embodiment is shown in FIG. 6 and FIG. 7. In this embodiment, as shown in FIG.
4 are provided, but these passages 27, 28, 31 and the sub-throttle valve 34 are omitted in FIG.

Referring to FIGS. 6 and 7, the carburetor housing 1
A communication passage 44 extending in the longitudinal direction of the cylinder head 3 is formed above 1.12, and this communication passage 44 is connected to each branch passage 45.
are connected to the intake ports 1 to 5 of each cylinder, respectively.

Further, an EGR port 35 and an idle fuel supply port 36 are opened in the center between the communication passages.

In a 4-cylinder internal combustion engine as shown in Figure 6, if the ignition order is 1-3-4-2, then when the 12th cylinder is on the intake stroke, the ignition order is 1-3-4-2.
The number cylinder is on the exhaust stroke.

Generally speaking, at the end of the exhaust stroke, there is a valve overlap period when both the intake valve and the exhaust valve open, and at this time, the burnt gas in the combustion chamber is blown back into the intake port.

Therefore, for example, if the No. 3 cylinder is at the end of its exhaust stroke, the pressure in the intake port 5 of the No. 3 aromatic cylinder C will become high due to the blowback effect of burned gas, while the pressure in the No. 3 cylinder C, which is in the intake stroke at this time, will be high.
A large negative pressure is generated within the intake port of the incense cylinder A.

As a result, the mixture or burnt gas in the intake port 5 of the three scent cylinders C passes through the branch passage 45 and the communication passage 44 to the one scent cylinder A.
The mixture is ejected into the intake port 5 from the branch passage 45 that opens to the intake port 1-5, and strong turbulence is generated within the combustion chamber 4 by this ejected mixture flow or burnt gas flow.

This also applies to other cylinders.

Therefore, in the embodiments shown in FIGS. 6 and 7, strong turbulence occurs in the combustion chamber 4 due to both the mixture flow jetting out from the branch passage 31 and the mixture flow or burnt gas flow jetting out from the branch passage 45. will occur.

As described above, during engine operation, the air-fuel mixture or burnt gas flows through the communication passage 44 from one cylinder to another cylinder due to the blowback effect during the non-polymerization period.

Therefore, the EGR gas supplied from the EGR port 35 is mixed with the air-fuel mixture while flowing through the communication path 44 together with the air-fuel mixture, and the vaporization of the fuel supplied from the idle fuel supply port 36 is promoted. become.

As described above, according to the present invention, the air-fuel mixture formed in the pair of carburetors is mixed with each other and then distributed again, so that the fuel distribution between each cylinder is uniform, and moreover, only one auxiliary intake valve is required. The structure becomes simple.

Further, since the EGR gas or idle fuel is supplied to the air-fuel mixture mixed with each other as described above, it is possible to uniformly distribute the EGR gas and idle fuel to each cylinder.

[Brief explanation of drawings]

Fig. 1 is a plan view of an internal combustion engine according to the present invention, and Fig. 2 is a plan view of an internal combustion engine according to the present invention.
3 is a graph showing changes in the opening degrees of the throttle valve and sub-throttle valve, FIG. 4 is a plan view of another embodiment, FIG. 5 is a side sectional view of FIG. 4, and FIG. The figure is a plan view of yet another embodiment, and FIG. 7 is a side sectional view of FIG. 6. 5... Intake port, 6... Intake valve, 1
3.14... vaporizer, 18.19...
Mixture passage, 24... Throttle valve, 27...
...Distribution passage, 28,44...Communication passage, 3
1.45... Branch passage, 33.41...
Connection passage, 34... Sub-throttle valve.

Claims (1)

[Scope of utility model registration request] In an internal combustion engine having at least a pair of carburetors for supplying fuel to separate cylinders, the mixture passages upstream of the throttle valves of each carburetor are connected to each other by a communication passage, and the mixture passages upstream of the throttle valves of each carburetor are connected to each other by a communication passage, and The mixture passages are connected to each other by a distribution passage, and the communication passage and the distribution passage are connected to each other by a single connection passage, and an auxiliary throttle valve is provided in the connection passage, and the carburetor throttle valve is installed in the connection passage when the engine is operated at low load. An intake system for a multi-cylinder internal combustion engine, in which an auxiliary throttle valve is opened in response to an increase in load while a valve is held in a closed state, and a carburetor throttle valve is opened during high-load engine operation.