JPH0522046B2 - - Google Patents

Description

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

FIG. 1 is an explanatory diagram showing an air supply system of a conventional internal combustion engine, and FIG. 2 is a view taken in the direction of arrow A in FIG. In FIG. 1, 01 is an air supply valve, 02 is an air intake valve seat insert, 03 is an air intake port, 04 is a cylinder, and the arrows indicate the flow of air supply. Figure 2 is a view from the cylinder side in Figure 1, that is, a view from arrow A, where 05 is the exhaust valve, and 0
7 indicates the fuel valve (in the case of diesel) or the spark plug (in the case of gasoline), and 06 indicates the flow velocity distribution of the supply air from around the intake valve.

In the above configuration, when air or mixture enters the cylinder 04 from the air supply port 03, the third
As shown in the figure, the upper part of the air intake valve seat insert 02 is guided by the wall surface and has a turning component around the center of the air intake valve 01 until it reaches the air intake valve along the shape of the inner wall surface of the port. It flows from above the air supply valve 01 along the inner surface.

The flow inside the air supply port is greatly affected by the port's inner wall surface, and if the surface is rough, the flow will be disrupted near the wall, affecting the flow velocity distribution inside the port, and the flow of air from around the air supply valve will be reduced. It also affects.

The air supplied into the cylinder forms a swirling flow around the cylinder axis, helping to form a mixture within the cylinder and improving combustion efficiency.

However, the above method has the following drawbacks.

The roughness of the inner wall surface of the conventional air supply port 03 is uniform, and even when the engine speed increases and the air flow velocity increases, the wall surfaces of each part act uniformly.

Therefore, the swirl ratio (the ratio of the swirling speed N _S of the supply air to the rotational speed N _E of the engine), which indicates the degree of swirl strength with respect to the engine speed, is as shown in Fig. 4.
This is almost constant, which goes against the requirement that it is better for the swirl ratio to vary with the engine speed in order to assist the engine's mixture formation and combustion reaction. For example, in a four-stroke direct injection diesel engine, the overall performance is better if the swirl ratio is larger at low speeds and smaller at high speeds.

An object of the present invention is to provide an air intake port for a four-stroke internal combustion engine that can improve the overall performance of the engine by changing the swirl ratio with respect to the engine speed. This is achieved by making the surface roughness of the bottom surface of the inner surface of the port formed on the cylinder head rougher or providing a group of small protrusions in the air intake port of a four-cycle internal combustion engine.

In this case, by partially changing the flow condition near the inner surface of the intake air port and taking advantage of the fact that the flow velocity inside the intake air port increases as the engine speed increases, the flow velocity distribution inside the port can be adjusted. This changes the swirl ratio to the engine speed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 is a perspective view showing an air supply port according to an embodiment of the present invention, and FIG. 6 is a view taken in the direction of arrow A in FIG.

In Fig. 5, 01 is an air intake valve, 02 is an air intake valve seat insert, 03 is an air intake port, and 031 is a rough surface portion or a group of small protrusions provided on the bottom of the air intake port, and is a cylinder head. The air supply port 03 formed at 09 is provided with a rough surface portion or a group of small protrusions 031. 061 is the air supply flow flowing from around the intake valve through the intake valve into the cylinder, and 08 is the turbulence in the flow caused by a rough surface or a group of small protrusions.

Fig. 6 is a view in the direction of arrow A in Fig. 5, that is, a view seen from the cylinder side in Fig. 5, and the flow velocity distribution around the intake valve has changed compared to the conventional one (Fig. 2). , shows the case where the maximum flow velocity is at the center of the cylinder. In the figure, 05 is an exhaust valve, 07 is a fuel valve (in the case of diesel) or a spark plug (in the case of gasoline), and 061 is the air supply flow flowing from around the intake valve through the intake valve into the cylinder.

The functions and effects of the above configuration will be described.

FIG. 5 shows an air supply port according to the present invention, in which a rough surface or a group of small protrusions 031 provided on the bottom of the air supply port 03 causes turbulence in the flow near the wall inside the port. In particular, as the flow speed increases, the degree of turbulence increases, and the difference from the smooth portion increases, the flow speed distribution changes with the engine speed, and the flow speed distribution flowing from around the intake valve into the cylinder changes.

In the case of this embodiment, when the engine speed is high due to a rough surface or a group of small protrusions on the bottom surface, the flow flowing along the bottom surface of the port is affected, and the flow velocity decreases, resulting in the flow shown in Fig. 6. The flow velocity distribution from around the air supply valve is as shown. That is, the maximum flow velocity point changes depending on the center of the cylinder.

As a result, as shown in FIG. 7, the engine speed increases and the swirl ratio (N _S /N _E ) decreases.

Therefore, by providing such characteristics, a direct injection diesel engine can obtain good performance over the entire operating range of engine speed.

That is, in the present invention, the flow velocity distribution around the air supply valve is improved by increasing the fluid resistance at the bottom of the air supply port and reducing the air flow velocity by using a large number of small protrusions provided on the bottom of the air supply port. It is possible to control the change in the swirl ratio with respect to the engine speed depending on the position of the small protrusion group on the rough surface or the port surface.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the air supply system of a conventional internal combustion engine, FIG. 2 is a view taken in the direction of arrow A in FIG. 1, and FIG. 3 is an explanatory diagram showing the state of air flowing into the cylinder from the intake port. Figure 4 is a diagram showing changes in swirl ratio, Figure 5
The figure is a perspective view showing an air supply port according to an embodiment of the present invention, FIG. 6 is a view taken along arrow A in FIG. 5, and FIG. 7 is a diagram showing changes in the swirl ratio. 03...Air supply port, 031...Rough surface roughness or small protrusion group.

Claims (1)

[Claims] 1 At the intake port of a 4-stroke internal combustion engine,
An air intake port for an internal combustion engine, characterized in that the bottom surface of the inner surface of the air intake port formed on the cylinder head has a rough surface or is provided with a group of small protrusions.