JPS589253B2 - 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.

Normally, in a gasoline engine, 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 within the combustion chamber, so the combustion speed will be sufficiently increased, but during low-speed, low-load operation, sufficient turbulence will 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. 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 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 rate of air flowing through the venturi section of the carburetor is slow, and therefore the relative velocity between the injected fuel and the air flow is slow, making it impossible to atomize the fuel sufficiently, and as a result, a large amount of fuel is is supplied into the combustion chamber in a liquid state, which is one of the causes of worsening combustion and 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 a sub-intake passage is branched from the intake passage between the carburetor throttle valve and the second throttle valve. JP-A-54-69619 discloses an internal combustion engine in which the intake passage is reconnected to the intake passage downstream 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 a high speed, vaporization of the fuel is promoted.

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

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 3 that reciprocates within the cylinder block 1, and a cylinder head is fixed on the cylinder block 1, and 4 is a combustion chamber formed between the piston 2 and the cylinder head 3. 5 is an intake port formed in the cylinder head 3; 6 is an intake valve;
1 is an exhaust port, 8 is an exhaust valve, 9 is a spark plug, 10 is an intake manifold, 11 is a carburetor, and 12 is a carburetor throttle valve, and this carburetor throttle valve 12 is an accelerator located in the vehicle cab. Operated by pedal.

As shown in FIG. 1, the intake manifold 10 is fixed to the cylinder head 3 via a spacer 13, and a second throttle valve 14 is inserted into the spacer 13.

On the other hand, as shown in FIGS. 1 and 2, the volume of the intake port 5 around the intake valve stem 6a is expanded, and as a result, an annular space surrounding the intake valve stem 6a, that is, a vortex boosting chamber 18 is formed.

The arm 2 is attached to the throttle shaft 19 of the second throttle valve 14.
0 is fixed, and a control rod 22 of a negative pressure diaphragm device 21 is pivotally attached to the tip of this arm 20.

The negative pressure diaphragm device 21 has an atmospheric pressure chamber 24 and a negative pressure chamber 25 separated by a diaphragm 23, and a compression spring 26 for pressing the diaphragm is inserted into the negative pressure chamber 25.

The vacuum chamber 25 is connected via a vacuum pipe 21 into the intake manifold 10 downstream of the carburetor throttle valve 12, while a control rod 22 is fixed to the diaphragm 23.

Referring to FIGS. 1 to 3, the second throttle valve 14
A pair of grooves 28 and 29 extending from the intake manifold 10 into the intake port 5 via the spacer 13 are formed on the upper and bottom walls of the surrounding intake passage.

These grooves 28 and 29 extend forward with respect to the axis of the intake passage, that is, in a spiral manner.

During low-load operation with a small opening of the carburetor throttle valve 12, the negative pressure inside the intake manifold 10 is large, and as a result, the diaphragm 23 moves downward against the spring force of the compression spring 26, so that the second throttle valve 14 is opened as shown in FIG. in the closed position as shown.

Therefore, at this time, the fuel supplied from the carburetor 11 is supplied into the intake port 5 via the pair of grooves 28 and 29.

As shown in FIGS. 1 to 3, the cross-sectional area of the kerfs 28 and 29 is extremely small, so that the air-fuel mixture flows between the kerfs 28 and 2.
Since the fuel flows in the grooves 9 at a high speed, vaporization of the fuel in the grooves 28 and 29 is promoted.

On the other hand, since the kerfs 2B and 29 are arranged in a spiral shape obliquely with respect to the axis of the intake passage, a swirling flow is given to the air mixture flowing out from the kerfs 28 and 29.

This mixture flow flows into the combustion chamber 4 while swirling around the intake valve stem 6a as shown by arrow D, and thus flows into the combustion chamber 4.
Generates a strong swirling flow inside.

On the other hand, during high-load engine operation, the negative pressure within the intake manifold 10 becomes small, so the diaphragm 23 is raised by the spring force of the compression spring 26, and as a result, the second throttle valve 14 is fully opened.

Therefore, at this time, the flow resistance becomes small and a high filling efficiency can be obtained.

It is preferable to provide the second throttle valve 14 as close to the intake valve 6 as possible. By doing so, when the second throttle valve 14 is fully closed during vehicle deceleration, the surface area of the intake port downstream of the second throttle valve 14 is small. Therefore, even if the fuel adhering to the inner wall surface 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 grooves 28 and 29, which not only alleviates intake interference but also increases the flow rate of the air-fuel mixture flowing in the grooves 28 and 29 to an extremely high speed. As a result, the vaporization of the fuel can be greatly promoted, and furthermore, by generating a strong swirling flow within the intake port, a strong swirling flow can be generated within the combustion chamber.

As described above, according to the present invention, by providing grooves that are easy to process and have a simple structure, it is possible to increase the combustion rate over the entire operating range, thereby not only achieving stable combustion but also reducing exhaust emissions. is improved, and the fuel consumption rate can be further improved.

[BRIEF DESCRIPTION OF THE 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 line 1-v in FIG. It is a sectional view taken along the -Vl line. 5... Intake port, 6... Intake valve, 8
...Exhaust valve, 12...Carburizer throttle valve, 13...Spacer, 14...Second throttle valve, 21...Negative Pressure diaphragm device, 28, 29...cut groove.

Claims (1)

[Claims] 1. A second throttle valve is provided in the intake passage downstream of the carburetor throttle valve, and the upstream and downstream sides of the second throttle valve are connected, and the valve is tilted with respect to the flow direction of the air-fuel mixture along the inner wall surface of the intake passage. A throttle valve drive mechanism is provided, in which a spiral cut groove is formed on the inner wall surface of the intake passage, and further fully closes the second throttle valve during low engine load operation and fully opens the second throttle valve during high engine load operation. An intake system for an internal combustion engine comprising: