JPS5947128B2 - Internal combustion engine intake system - Google Patents

Description

[Detailed description of the invention] The present invention relates to an intake port for an internal combustion engine.

As a method of reducing harmful components in exhaust gas, it is known to use a lean mixture or a mixture containing a large amount of recirculated exhaust gas.

However, these mixtures have slow flame propagation speeds,
Therefore, there is a problem that stable combustion cannot be obtained because the combustion speed is slow.

Therefore, in order to obtain stable combustion using these mixtures, it is necessary to increase the combustion speed, and one method for this purpose is to generate a strong swirling flow within the combustion chamber during the intake stroke.

One possible way to generate such a strong swirling flow is to use a helical intake port like the one currently used in direct-injection diesel engines, but it is not possible to use such a helical intake port over a wide area as it is. When applied to a high-speed spark ignition gasoline engine that changes the amount of intake air by changing the amount of intake air.If the structure of the tortoise-helical intake port is set so that a strong swirling flow can be formed in the combustion chamber during low-load operation, a large amount of intake air can be obtained. There is a problem in that suction efficiency decreases during high-speed, high-load operation that requires

An object of the present invention is to provide an intake port that can constantly generate a strong swirling flow without reducing suction efficiency during high-speed, high-load operation.

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

1 and 2, 1 is a cylinder block of a multi-cylinder internal combustion engine, 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 a combustion engine. 5 is a spark plug, 6 is an intake valve, I is an exhaust valve, 8 is an intake port, 9 is an intake manifold, and 10 is a carburetor.

As clearly shown in FIGS. 1 and 2, the intake passage 8 is formed in a helical shape.

Therefore, when the intake valve 6 opens during the intake stroke, the lean mixture or the mixture containing a large amount of recirculated exhaust gas descends while swirling within the intake port 8 as shown by arrow A, and thus flows into the combustion chamber 4. Inside, a strong swirling flow is generated as shown by arrow B in FIG.

As a result, the combustion speed within the combustion chamber 4 is increased, resulting in stable combustion.

In order to generate a strong swirling flow as shown by arrow A in the intake port 8, it is preferable that the inner wall of the intake port 8 be formed with a curve as smooth as possible. Forming ports is not preferred.

In particular, the outer circumferential wall portion 11 of the intake port 8, which serves to generate and guide the swirling flow A, must be particularly smooth.

By doing this, a strong swirling flow is generated in the combustion chamber 4, but with such a helical intake port shape, the inflow resistance is greater than that of a normal almost straight intake port, and the intake air is During high-speed, high-load operation with a large amount of air, the amount of incoming air decreases, that is, the suction efficiency decreases, resulting in a problem that sufficient output cannot be obtained.

In order to solve this problem, a bypass passage 12 is provided in the present invention.

The bypass passage 12 opens on the inner wall of the helical intake port end portion 13 in the swirling direction of the swirling flow A, and on the other hand, the bypass passage 12 opens toward the swirling direction of the swirling flow A.
It is connected to the manifold branch pipe collection part of the intake manifold 9 via the intake manifold 5 .

A shut-off valve 16 is provided in the conduit 15 and is connected via a rod 17 to a diaphragm device 18 .

The diaphragm device 18 has a movable diaphragm 19 and a vacuum chamber 20 which is connected to the intake manifold 9 via a vacuum conduit 21 .

The on-off valve 16 is normally closed, but when the negative pressure in the negative pressure chamber 20 becomes lower than a predetermined negative pressure, the diaphragm 19 rises, thereby fully opening the on-off valve 16.

Therefore, the on-off valve 16 is closed during low load operation and fully opened during high load operation.

When the on-off valve 16 is fully opened, in addition to the combustible air-fuel mixture drawn into the combustion chamber 4 from the intake port 8, the combustible air-fuel mixture is drawn into the combustion chamber 4 from the bypass passage 12.

Therefore, during high-speed, high-load operation, the amount of combustible mixture sucked into the combustion chamber 4 is increased by the combustible mixture supplied from the bypass passage 12, thus ensuring good suction efficiency.

According to the present invention, as shown in FIG.
2 is formed on the inner wall surface of the helical intake port terminal portion 13 without protruding into the helical intake port 8. Therefore, the swirling flow is not weakened by the bypass passage 12, and the bypass passage 12 Since it is open toward the swirling direction of the swirling flow, the swirling flow does not flow into the bypass passage 12 and be decelerated, so that a strong swirling flow can be generated during low-load operation.

Furthermore, the on-off valve 16 is controlled by the negative pressure in the intake manifold 9, and is fully opened when the negative pressure in the intake manifold 9 becomes smaller than a predetermined negative pressure. High filling efficiency can be obtained during operation.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of an internal combustion engine according to the present invention, and FIG. 2 is a plan sectional view schematically showing FIG. 1. 4... Combustion chamber, 5... Spark plug, 6...
...Intake valve, 8...Intake port, 9...
...Intake manifold, 10-...Carburetor, 12
...Bypass passage, 16-...Opening/closing valve,
18...Diaphragm device.

Claims (1)

[Claims] 1. The intake port from the intake manifold to the intake valve is formed in a helical shape, and a bypass passage branched from the intake manifold is opened on the inner wall surface of the intake port at the terminal end of the helical intake port toward the swirling direction of the swirling flow, An on-off valve is arranged in the bypass passage, and the on-off valve is connected to a diaphragm device in the intake manifold that responds to negative and positive changes, so that when the negative pressure in the intake manifold becomes smaller than a predetermined negative pressure, An intake system for an internal combustion engine that allows the on-off valve to be fully opened.