JPH018657Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a combustion chamber of an internal combustion engine.

The temperature inside the combustion chamber of an internal combustion engine is quite high,
In particular, heat spots occur near the exhaust port of the cylinder head that forms part of the combustion chamber.

This heat spot noticeably occurs in a portion located between the exhaust port and the intake port, and when extreme temperature distribution occurs, it causes a locally weakened portion.

This is due to the heat flow passing through the edge portion 3 of the cylinder head 2 on the exhaust port 1 side at high speed during the exhaust stroke, as shown in FIG.

This weakened portion grows due to the combination of thermal load and mechanical load (vibration, etc.), and there is a risk that a portion of the cylinder head may eventually crack.

As a countermeasure to this problem, casting different metals between the valves was considered, such as in Utility Model Application No. 56-154546, but this was not a sufficient measure in terms of cost.

Furthermore, in Japanese Patent Application Laid-Open No. 55-84809, a groove-shaped guide passage is provided on the lower surface of the cylinder head between the intake valve and the exhaust valve, and when the intake and exhaust valves overlap, the exhaust valve is cooled by the air that blows through the guide passage. According to this method, although it has the effect of cooling the exhaust valve, the guide passage is groove-shaped, and the corners of the guide passage are edge-shaped when viewed in cross section, which causes problems during the exhaust stroke from combustion. There is a problem in that the occurrence of heat spots is unavoidable, and the groove-like passages cause stress concentration, which actually worsens the durability of the cylinder head.

The present invention was devised to eliminate such problems, and aims to solve the above problems by forming the cylinder head edge on the exhaust port side, through which heat passes at high speed, into a smooth curved surface. .

In Fig. 1, 4 is an exhaust valve, 5 is an intake valve, 6 is an intake port, 7 is a water jacket,
8 is a valve insert.

In order to achieve the above object, the present invention assumes a combustion chamber structure of an internal combustion engine in which intake and exhaust ports are opened in the cylinder head and intake and exhaust valves are respectively installed in these openings. The cylinder head edge part, which is located between the valves and connects the outer peripheral lower end edge on the intake side of the exhaust valve insert, which has a high heat load on the exhaust port side, and the lower surface of the cylinder head, is formed into a smooth curved surface.

Based on this configuration, high-temperature gas flows smoothly along the curved surface of the cylinder head edge portion from the combustion stroke to the exhaust stroke without causing the phenomenon of colliding with the cylinder head edge portion. Therefore, heat spots are less likely to occur, and the durability of the cylinder head is improved accordingly.

Embodiments of the present invention will be described below, in which the same components as in FIG. 1 are denoted by the same reference numerals.

In FIGS. 2 and 3, an intake port 6 and an exhaust port 1 are opened in a cylinder head 2 forming a part of a combustion chamber, and intake and exhaust valves 4 and 5 are seated around these openings. Valve insert 8
Attach it in a ring.

Of the cylinder head 2 equipped with this valve insert 8, as shown by the diagonal line A in FIG. The head edge portion 3 is shaved off, and this portion (the portion indicated by diagonal lines A) is formed into a smooth curved surface 10.

In this way, the shape of the cylinder head is specified so as to eliminate the cylinder head edge portion 3, which has a high thermal load, so that heat spots due to heat flow are reduced.

Therefore, during the exhaust stroke, high temperature combustion gas (exhaust gas) passes smoothly over the curved surface 10 without colliding with the cylinder head edge portion 3.

As a result, the heat spots in the cylinder head 2 are reduced to the extent that the occurrence of weak parts in the cylinder head 2 is prevented even under severe engine operating conditions, and the durability of the cylinder head 2 can be improved.

As explained above, according to the present invention, the parts of the cylinder head where the heat load is particularly high are removed and the maximum temperature of that part is lowered, thereby reducing the heat spots that occur in the cylinder head and reducing the weak parts. This has the effect of improving the durability of the cylinder head.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a conventional example, FIG. 2 is a bottom view of a cylinder head of an embodiment of the present invention, and FIG. 3 is an enlarged sectional view of a main part of an embodiment of the present invention. 1...Exhaust port, 2...Cylinder head, 3
... Cylinder head edge part, 6 ... Intake port, 8 ... Valve insert, 10 ... Curved surface.

Claims (1)

[Scope of utility model registration request] In the combustion chamber of an internal combustion engine, in which intake and exhaust ports are opened in the cylinder head and intake and exhaust valves are installed in these openings, the heat load on the exhaust port side is located between the exhaust port and the intake port. 1. A combustion chamber for an internal combustion engine, characterized in that a cylinder head edge portion connecting a lower outer circumferential edge on an intake side of an exhaust valve insert with a high temperature and a lower surface of a cylinder head is formed into a smooth curved surface.