JPS6246810Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is an intake system for an engine of a type in which the intake port, which is opened and closed by an intake valve, is divided into upper and lower parts, with the upper part serving as a high-load intake port and the lower part serving as a low-load intake port. This is related to the improvement of

Conventionally, intake systems with dual intake ports as described above have been well known, and when the engine has a low intake air volume and is at low load, the air-fuel mixture with a high flow velocity is directed into the combustion chamber from the low-load intake port. This creates a swirl in the combustion chamber to improve combustion performance, while at the same time, when the engine is under high load with a large amount of intake air, the air-fuel mixture is also supplied from the high-load intake port to improve charging efficiency. It has the advantage of ensuring the necessary output by
Publication No. 115917).

However, considering the generation of the swirl, if the low-load intake port is curved so that the air-fuel mixture flowing in from the low-load intake port follows the circumferential surface of the cylinder bore, the air-fuel mixture that has been given good directivity will It is disturbed by colliding with the stem of the intake valve that opens and closes the intake port, and when flowing down a curved part, it is swung toward the center of the combustion chamber (center of the cylinder bore) by centrifugal force, causing deviation.
Since the intake port opens downward into the combustion chamber, it is actually difficult to generate an effective swirl due to various factors such as the air-fuel mixture flowing in with downward inertia. There is a problem that I have heard about.

The present invention was devised in view of such problems, and its basic purpose is to provide an engine intake system having a low-load intake port structure that can generate a strong swirl at low loads. It is said that

Therefore, in this invention, a single intake port is divided into upper and lower intake ports for high load and low load.
In an engine intake system in which the downstream part of the low-load intake port is curved so that its center line of curvature points toward the outside of the cylinder bore, the cross-sectional shape of the low-load intake port is such that the long axis of the cross-section is aligned with the lower end surface of the cylinder head. The parallel flat shape makes the mixture flow flat in the vertical direction, while the curved part of the low-load intake port is provided with a partition member that divides the flat flow of the mixture in the horizontal direction. The basic feature is that it corrects the drift caused by centrifugal force and provides directivity to prevent the mixed air flow from colliding with the intake valve shaft.

Hereinafter, the present invention will be explained in more detail based on the illustrated embodiments.

In FIG. 1, 1 is a cylinder body having a vertical cylinder bore 2 therein, 3 is a cylinder head fixed to the top surface of the cylinder body 1, and 4 is a gasket (not shown) on one side wall 3a of the cylinder head 3. The intake manifold 6 is connected to the intake passage 7 formed in the intake manifold 4 and extends downward from one side wall 3a to the concave wall 3b of the cylinder head 3 that defines the upper surface of the combustion chamber 8. 9 is an intake valve that opens and closes the intake port 6 at predetermined timing; 10 is an intake port that opens across the center of the combustion chamber 8 from the intake port opening 6a of the concave wall 3b; Exhaust port 11 reaching the other side wall 3c of the cylinder head 3
12 is an exhaust valve that opens and closes the exhaust port 10 at a predetermined timing, and 12 is a camshaft that operates rocker arms 13 and 14 that open and close the intake valve 9 and the exhaust valve 11, respectively, at different timings in synchronization with the rotation of the engine. be.

As shown in FIG. 1, at the mounting part of the intake manifold 4, there is a partition wall 15 that partitions the intake passage 7 into upper and lower parts.
As shown in FIG.
The intake port 6 is connected to an upper high-load intake port 17 which has a circular cross section and a large passage area, and a flat cross-sectional shape whose vertical height is smaller than its width, and whose long axis is the cylinder. Bottom surface 3 of head 3
d and a lower low-load intake port 18 with a smaller passage area. and,
For the high-load intake port 17, a switching valve 19 made of a butterfly valve is provided at the inflow portion of the high-load intake port 17 defined by the partition wall 15 on the intake manifold 4 side. is controlled by a control mechanism (not shown) to close the switching valve 19 when the engine load is low, below a set load, and to open the switching valve 19 in accordance with the load when the engine load is high, exceeding the set load. In addition, the first
In the figure, A is a carburetor installed above the intake manifold 4.

On the other hand, as specifically shown in FIG. 3, the low-load intake port 18, which has a flat cross-sectional shape, reaches the opening 6a of the intake port 6 on the combustion chamber 8 side from the inflow portion 18a on the intake manifold 4 side. Outflow part 1
8b, and this curved portion 18c gives directivity toward the circumferential surface of the cylinder bore 2 to the air-fuel mixture flowing down. At the same time, in the present invention, the curved portion 1 of the low-load intake port 18
A partition wall 20 having a curve substantially similar to the curved part 18c from 8c to the outflow part 18b is provided between the bottom wall surface 18d and the top wall surface 18e of the low-load intake port 18 to divide the mixed air flow into left and right sides in the horizontal direction.

This partition wall 20 is provided to prevent the air-fuel mixture flowing into the inlet portion 18a with a substantially uniform density from being swung outward in the radius of curvature of the curved portion 18c by centrifugal force in the curved portion 18c. Therefore, the distance W ₁ between the side wall 18f of the low-load intake port 18 with a small radius of curvature and the partition wall 20 is equal to the distance W 2 between the side wall 18g with a large radius of curvature and the partition wall _20.
The center lines C _A and C _B of the mixture flow passing through the intervals W ₁ and W ₂ are set at an appropriate distance from the valve shaft 9a of the intake valve 9, respectively. to guide you. Further, the wall surface 20a having a large radius of curvature on the downstream side of the partition wall 20 provides a kind of throttle 21 between it and the protrusion 18h provided on the downstream side of the side wall 18g having a large radius of curvature of the low-load intake port 18. and set the interval by this aperture 21.
The air mixture flow toward the W ₂ side is increased, and the amount of air mixture toward the circumferential surface of the cylinder bore 2 is increased.

In addition, as shown in FIG. 1, the intake port 6 as a whole is largely curved downward and opens into the combustion chamber 8, but the low-load intake port 18 has a high opening 6a of the intake port 6. The opening 6a of the intake port 6 can be set from the low-load intake port 18 to the opening 6a of the intake port 6.
The mixture flow that flows into the combustion chamber 8 through the space between The swirl strength of the airflow can be made sufficiently large.

As is clear from the above description, the present invention has a low-load intake port that forms a dual intake port together with a high-load intake port that has a flat cross-sectional shape,
Furthermore, the present invention provides an engine intake device characterized in that a partition member is provided at the curved portion of the low-load intake port to partition the air mixture flow into left and right sides and guide the air mixture to the left and right, respectively.

According to the present invention, the mixed air flow in the low-load intake port is made into a flat flow, and this flat flow is divided into left and right sides to prevent drift due to centrifugal force, and the valve shaft of the intake valve that opens and closes the intake port. The swirl in the combustion chamber is made stronger by the combined effect of avoiding collisions between the cylinders and the guidance of the partition member, which directs the mixture flow as a whole toward the circumferential surface of the cylinder bore. Therefore, it is possible to improve the combustibility at low loads and improve the fuel efficiency.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view of an engine intake system showing an embodiment of the present invention, Fig. 2 is a side view of the main part of the cylinder head in the - line direction of Fig. 1, and Fig. 3 is a - side view of the main part of the cylinder head in the - line direction of Fig. 2. It is a linear cross-sectional explanatory view. 1...Cylinder body, 2...Cylinder bore, 3
...Cylinder head, 4...Intake manifold,
6... Intake port, 8... Combustion chamber, 9... Intake valve, 17... Intake port for high load, 18... Intake port for low load, 20... Partition member.

Claims (1)

[Scope of Claim for Utility Model Registration] The intake port that is opened and closed by an intake valve is divided into upper and lower parts, the upper part is a high-load intake port, the lower part is a low-load intake port, and the lower part is a low-load intake port. In an engine intake system, the cross-sectional shape of the low-load intake port is a flat shape with its long axis parallel to the lower end surface of the cylinder head. An intake system for an engine, characterized in that a partition member is provided at a curved portion downstream of the low-load intake port to horizontally partition the low-load intake port.