JPS589247B2 - Internal combustion engine intake system - Google Patents

Description

[Detailed description of the invention] The present invention relates to an intake system for an 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. Therefore, 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 a helical shape or by using a shroud valve to forcefully generate a swirling flow in the combustion chamber. As the resistance increases, there is a problem in that charging efficiency during high-speed, high-load operation decreases.

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 at the same time, a powerful You have to try to cause some 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 velocity of the air flowing through the venturi section of the carburetor is slow, and the relative velocity between the ejected fuel and the airflow is slow, so the fuel cannot be atomized sufficiently, and as a result, a large amount of fuel is is supplied into the combustion chamber in a liquid state, which worsens combustion and is one of the causes of worsening exhaust emissions.

In order to solve these problems, a second throttle valve is provided in the intake passage downstream of the carburetor throttle valve, and an auxiliary intake passage is branched from the intake passage between the carburetor throttle valve and the second throttle valve. JP-A-53-127916 discloses an internal combustion engine in which the intake passage is reconnected to the slow-flow intake passage of the second throttle valve.

In this internal combustion engine, by closing the second throttle valve during low-load operation, the air-fuel mixture is supplied from the auxiliary intake passage with a small cross-sectional area, and the mixture ejected from the auxiliary intake passage causes turbulence in the combustion chamber. Since the air-fuel mixture flows in the intake passage at high speed, vaporization of the fuel is promoted.

However, in this internal combustion engine, the auxiliary intake passage is formed from a pipe or from a hole drilled in the intake manifold wall x, so if a pipe is used, not only will extra parts be required. There are problems in that a space is required for the pipes, and in the case of drilling holes in the wall surface of the intake manifold, complicated machining is required.

The present invention provides an internal combustion engine that has a simple structure and can generate strong turbulence in the combustion chamber during low-speed, low-load operation while ensuring high charging efficiency during high-speed, high-load operation, and can promote fuel vaporization. There is a particular thing.

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

Referring to FIG. 1, 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, and 4 is formed between the piston 2 and the cylinder head 3. A combustion chamber, 5 is an intake port formed in the cylinder head 3, 6 is an intake valve, 7 is an exhaust port, 8 is an exhaust valve, 9 is a spark plug, 10 is an intake manifold, 11 is a carburetor, 12 is a carburetor A throttle valve is shown, the carburetor throttle valve 12 being actuated by an accelerator pedal located in the vehicle cab.

As shown in FIG. 1, the intake manifold 10 is fixed to the cylinder head 3 via a spacer 13, and a groove 14 is formed on the bottom surface of the inner wall of the spacer 13.

As shown in FIG. 1, this kerf 14 extends to the intake port 5 adjacent to the spacer 13 and to the bottom of the inner wall of the intake manifold 10.
5 is inserted, but when the second throttle valve 15 is in the fully closed position as shown in FIG.

The arm 1 is attached to the throttle shaft 16 of the second throttle valve 15.
7 is fixed, and a control rod 19 of a negative pressure diaphragm device 18 is pivotally attached to the tip of this arm 17.

The negative pressure diaphragm device 18 has an atmospheric pressure chamber 21 and a negative pressure chamber 22 separated by a diaphragm 20, and a compression spring 23 for pressing the diaphragm is inserted into the negative pressure chamber 22.

The vacuum chamber 22 is connected via a vacuum conduit 24 into the intake manifold 10 downstream of the carburetor throttle valve 12, while a control rod 19 is fixed to the i-diaphragm 20.

During low load operation with a small opening degree of the carburetor throttle valve 12, the negative pressure inside the intake manifold 10 is large, and as a result, the diaphragm 20 moves downward against the spring force of the compression spring 23, so that the second throttle valve 15 is in the closed position as shown.

Therefore, at this time, the fuel supplied from the carburetor 11 is
4 and into the combustion chamber 4 through the intake port 5.

As shown in FIG. 2, the cross-sectional area of the kerf 14 is extremely small;
Therefore, the air-fuel mixture flows in the kerf 14 at high speed, so the kerf 1
4, vaporization of the liquid fuel is promoted.

The air-fuel mixture that has passed through the kerf 14 and is injected into the intake port 5 flows into the combustion chamber 4 through the intake valve 6 while being maintained at a relatively high velocity, generating strong turbulence within the combustion chamber 4. I will let you do it.

As a result, the combustion rate is greatly increased.

On the other hand, during high-load engine operation, the negative pressure within the intake manifold 10 becomes small, so the diaphragm 20 is raised by the spring force of the compression spring 23, and the second throttle valve 15 is fully opened.

If a throttle valve is provided in the intake passage, the throttle valve and throttle shaft will create a large fluid resistance when the throttle valve is fully opened, but in the present invention, the cross-sectional area of the intake passage increases by 14 kerfs, so the fluid resistance The resistance becomes extremely small and therefore high filling efficiency can be obtained.

FIGS. 3 and 4 show an alternative embodiment to that shown in FIG.

In this embodiment, a kerf 25 is formed on the side surface of the inner wall of the spacer around the throttle shaft 16.

It is preferable to provide the second throttle valve 15 as close to the intake valve 6 as possible. By doing so, when the second throttle valve 15 is fully closed when the vehicle is slowing down, the surface area of the intake port downstream of the second throttle valve 15 is increased. is small, so even if the fuel adhering to the inner wall of the intake port evaporates immediately, it will not become very concentrated.

In addition, during low-load operation, the intake port 5 is connected to the inside of the intake manifold 10 only through the groove 14:25, which not only alleviates intake interference but also increases the flow rate of the air-fuel mixture flowing inside the groove 14:25 to an extremely high speed. Not only can the vaporization of the fuel be greatly promoted, but also powerful turbulence can be generated within the combustion chamber.

In this way, according to the present invention, it is possible to increase the combustion rate over the entire operating range by simply providing a cut groove that is easy to process and has a simple structure.In this way, not only stable combustion can be obtained, but also exhaust gas Emissions are improved and fuel consumption can be further improved.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of an internal combustion engine according to the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, FIG. 3 is a side sectional view of another embodiment, and FIG. 4 3 is a sectional view taken along the line IT-IV in FIG. 3. FIG. 5... Intake port, 6... Intake valve, 8
...exhaust valve, 12...carburizer throttle valve, 13...spacer, 14,25...
...kerf, 15...second throttle valve, 24.
... Negative pressure diaphragm device.

Claims (1)

[Claims] 1. A second throttle valve is provided in the intake passage downstream of the carburetor throttle valve, and a groove is formed on the inner wall surface of the intake passage that communicates the upstream and downstream sides of the second throttle valve and extends in the intake air mixture flow direction. An intake system for an internal combustion engine, further comprising a throttle valve drive mechanism that fully closes the second throttle valve during low engine load operation and fully opens the second throttle valve during high engine load operation.