JPS5934850B2 - 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.

It is known to form the intake port into a helical shape as a method of generating a strong swirling flow in the engine combustion chamber 16 to increase the combustion speed.

In order to use such a helical port to generate a strong swirling flow within the combustion chamber during low-speed, low-load operation, it is necessary to make the axis of the intake port significantly eccentric to the axis of the intake valve.

However, if the intake port axis is eccentrically eccentric to the intake valve axis by a wide margin, fluid resistance increases during high-speed, high-load operation, and as a result, the filling efficiency is significantly reduced.

In order to generate a strong turbulence in the combustion chamber (during low-load engine operation), a second throttle valve is provided in the intake passage downstream of the carburetor throttle valve, and a second throttle valve is installed between the carburetor throttle valve and the second throttle valve. A sub-intake passage with a small cross-sectional area is branched from the intake passage and opened again into the intake passage downstream of the second throttle valve.During low-load operation, the second throttle valve is opened and the air-fuel mixture flows into the sub-intake passage. to pass at high speed,
Therefore, an internal combustion engine has been proposed in which the vaporization of fuel is promoted in the sub-intake passage, and a strong turbulence is generated in the combustion chamber by the air-fuel mixture jetted out from the sub-intake passage.

However, in this type of internal combustion engine, the atomization and vaporization of the fuel are not sufficient, and therefore stable combustion cannot be obtained during low load operation, especially when idling.

The present invention connects the outlet opening of the sub-intake passage tangentially to the inner wall surface of the helical intake port, which has the intake port axis and the intake valve axis as subcenters to the extent that the filling efficiency does not decrease during high-speed, high-load operation. An object of the present invention is to provide an intake system for a multi-cylinder internal combustion engine, which generates and tightens a vortex in a helical intake port during low-load operation, thereby promoting atomization and vaporization of fuel.

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. 5 is an intake port formed in the cylinder head 3, 6 is an intake valve, 7 is an exhaust port 1-18 is an exhaust valve, 9 is a spark plug, 10
11 is an intake manifold, 11 is a carburetor, and 12 is a carburetor throttle valve, which is operated by an accelerator pedal located in the driver's cab of the vehicle.

8. FIG. 1 (As shown in this figure, a second throttle valve 14 is provided in the carburetor mixture passage 13 formed in the single carburetor 11.

Throttle shaft 15 supporting this second throttle valve 14
An arm 16 is fixed on top, and the tip of this arm 16 is connected to a control ring 18 of a negative pressure diaphragm device 17.

The negative pressure diaphragm device 17 has a negative pressure chamber 20 and an atmospheric pressure chamber 21 separated by a diaphragm 19, and a compression spring 22 for pressing the diaphragm is inserted into the negative pressure chamber 20.

Further, the negative royal house 20 is connected to the carburetor mixture passage 13 downstream of the carburetor throttle valve 12 via a negative pressure conduit 23,
- a control iron 18 is fixed to the force diaphragm 19;

As shown in FIG. 1, during low-load operation with a small opening degree of the carburetor throttle valve 12, the negative pressure in the carburetor mixture passage 13 downstream of the carburetor throttle valve 12 is large, and therefore, at this time, the diaphragm 19 moves to the right against the spring force of the compression spring 22, so that the second throttle valve 14 occupies the closed position as shown in FIG.

- When the carburetor throttle valve 12 is opened wide and high-load operation is performed, the negative pressure in the carburetor mixture passage 13 becomes small, and as a result, the diaphragm 19 moves to the left and the second throttle valve 14 is fully opened.

Referring to FIGS. 1 and 3, the intake manifold 10
An auxiliary intake air distribution passage 24 is formed below the cylinder head 3 and extends in the longitudinal direction of the cylinder head 3, and a central portion of the auxiliary intake air distribution passage 24 is located between the carburetor throttle valve 12 and the second throttle valve 14 via a passage 25. It is connected within the carburetor mixture pressure passage 13.

Furthermore, four sub-intake branch passages 26 are formed in the cylinder head 3 to connect each intake port 5 to the sub-intake distribution passage 24.

As can be seen from FIGS. 1 and 2, the intake port 5 is formed in a helical shape, but this helical intake port 5 is normally used in order to prevent a decrease in the filling effect during high-speed, high-load operation. The degree of eccentricity between the axis X of the intake valve and the axis Y of the intake bows 1 to 5 is set to be smaller than that of the helical intake port.

Therefore, with this helical intake port 5, although the charging efficiency does not decrease during high-speed, high-load operation as described above, a weaker swirling flow occurs in the combustion chamber 4 during high-speed, high-load operation than in the past. do not.

1 and 2, the auxiliary intake branch passage 26 extends almost straight in a plane Z perpendicular to the axis X of the intake valve 6, and extends on the side away from the axis X of the intake valve 6. It can be seen that the opening is tangential to the inner wall surface of the helical intake port 5 located therein.

During low engine load operation, as mentioned above, the second throttle valve 1
4 is in a closed state.

Therefore, the air-fuel mixture formed in the vaporizer 11 is sent into the sub-intake distribution passage 24 via the passage 25.

When the second throttle valve 14 is closed, the negative pressure in the intake port 5 is greater than the negative pressure in the carburetor mixture passage 13 upstream of the second throttle valve 14, so the intake valve 6 is closed. Even if the valve is closed, the air-fuel mixture flows from the sub-intake distribution passage 24 to the sub-intake branch passage 26 into the helical intake port 5.
This jets out and generates a vortex flow in the helical intake port 5 as shown by the arrow A in FIG. 2F.

While the air-fuel mixture flows through the sub-intake distribution passage 24 with a small cross-sectional area, the retention of liquid fuel is promoted, and after being ejected from the sub-intake branch passage 26, it flows along the inner wall surface of the helical intake port 5. When turning, the atomization of the fuel (gasification) is further promoted.

Next, when the intake valve 6 opens, the air-fuel mixture is ejected from the auxiliary intake branch passage 26, but the intake port 5 is connected to the intake port 5 of another cylinder.
Since the two cylinders are connected via the intake manifold 10, the air-fuel mixture ejected from the auxiliary intake branch passage 26 into the intake ports 5 of other cylinders simultaneously flows through the open intake ports 5 of the intake valves 6. This is what happens when the air is sucked into the combustion chamber 4.

That is, when the intake valve 6 opens, part of the air-fuel mixture is supplied into the combustion chamber 4 from the auxiliary intake branch passage 26 of another cylinder via the intake manifold 10 and the intake port 5, and the remaining air-fuel mixture is flows into the combustion chamber 4 through the auxiliary intake branch passage 26 of the cylinder during the intake stroke.

As mentioned above, a vortex is generated in the helical intake port 5 before the intake valve 6 opens, and when the intake valve opens, the air-fuel mixture flowing through the intake port 5 flows through the sub-intake branch passage 26. A strong swirling flow is generated in the combustion chamber 4 due to the swirling force applied to the air-fuel mixture jetted out from the combustion chamber 4, and as a result, the combustion speed is increased by a wide range of 1 during low-load operation.

- During high-power, high-load operation, the second throttle valve 14 is fully opened as described above, so most of the air-fuel mixture flows into the combustion chamber 4 via the intake manifold 10.

In this case, as described above, the helical intake port 5 is formed in a shape that does not reduce the filling efficiency, so that high filling efficiency can be ensured.

In addition, as shown by the broken line in FIG. 2, the width of the intake branch passage 26
A diaphragm 2T can also be provided near the outlet.

By providing such a throttle 27, it is possible to generate a vortex flow of the same strength in the intake port 5 of each cylinder, thereby making it possible to avoid variations in combustion among the cylinders.

As described above, according to the present invention, a vortex is generated in the helical intake port regardless of whether the intake valve is open or not, so that the atomization and vaporization of the air-fuel mixture are promoted, and the inside of the combustion chamber It is possible to generate a strong swirling flow, thereby increasing the combustion speed especially during low-load operation, thereby making it possible to ensure stable idling operation.

[Brief explanation of the drawing]

1 is a side cross-sectional view of an internal combustion engine according to the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a plan view of FIG. 1. 5...Intake bow 1~. 6...Intake valve,
10... Intake manifold, 11... Carburetor, 12... Carburetor throttle valve, 13...
... Carburetor mixing passage, 14... Second throttle valve, 24... Sub-intake distribution passage, 25...
... Passage, 26... Sub-intake branch passage.

Claims (1)

[Claims] 1 In a multi-cylinder internal combustion engine in which the mixture formed by the carburetor is distributed into the intake ports of each cylinder via the intake manifold, the carburetor mixture passage downstream of the carburetor throttle valve is used. A second throttle valve is provided within the intake valve, and an auxiliary intake distribution passage is connected to the carburetor mixture passage between the carburetor throttle valve and the second throttle valve, and extends almost straight in a plane perpendicular to the intake valve axis. A plurality of sub-intake branch passages are branched from the sub-intake distribution passage, and each sub-intake branch passage is opened tangentially on the inner wall surface of each helical-shaped intake port. Negative pressure generated in the carburetor mixture passage of the engine (in response to this, a negative pressure diaphragm device is provided which closes the second throttle valve during low engine load operation and fully opens the second throttle valve during high load operation). An intake system for a multi-cylinder internal combustion engine.