JP2502498Y2 - Combustion chamber structure of internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to improvement of a combustion chamber structure of an internal combustion engine for an automobile, for example.

2. Description of the Related Art As a combustion chamber structure of a conventional internal combustion engine of this type, for example, a structure as shown in FIGS. 2A and 2B is known (see Japanese Patent Laid-Open No. 58-204902).

Briefly described, this conventional example is applied to a gasoline engine for an automobile having four intake / exhaust valves per cylinder, and a substantially conical combustion chamber 2 formed at a lower end portion of a cylinder head 1 is , A pair of intake valve holes 3, 3 and exhaust valve holes 4, 4 are formed at symmetrical positions with respect to the center line in the longitudinal direction of the engine, and an ignition plug hole 5 penetrating the cylinder head 1 is formed in the center. ing. Further, the central portion of the upper surface 2a of the combustion chamber 2 where the tip of the spark plug hole 5 faces is a heat point (a portion which causes abnormal combustion such as knocking).
A substantially circular flat portion 6 is formed in order to prevent the occurrence of processing burrs. Further, a small circular locating portion 7 is formed at a substantially outer position between the exhaust valve holes 4, 4. The locating portion 7 is formed so as to project from the upper surface 2a of the combustion chamber 2 with a certain corner portion 7b in order to secure a horizontal surface 7a. The locating portion 7 is used when cutting around the combustion chamber 2. The cutting surface is controlled by the distance from the horizontal surface 7a as the locating reference surface,
It has a function of reducing the variation in the volume of the combustion chamber 2. Therefore, it is desirable to set the area of the horizontal surface 7a as large as possible.

Problems to be Solved by the Invention The conventional combustion chamber structure described above has four intake / exhaust valve holes 3,3,4,4.
The arrangement space of is extremely limited. Therefore, the locating portion 7 is unavoidably formed near the outer periphery of the combustion chamber 2 or near the spark plug hole 5, but it is difficult to secure a large area of the horizontal surface 7a. As a result, the cutting of the combustion chamber 2 is disadvantageous and highly accurate cutting cannot be obtained.

Further, since the locating portion 7 is provided in the vicinity of the outer periphery of the combustion chamber 2, the unburned gas staying in the recessed portion at the time of ignition of the air-fuel mixture ignites after the flame spread of the entire combustion chamber 2 and causes abnormal combustion. . Further, since the protruding corner portion 7b is intensively heated to become a heat point, this may cause abnormal combustion.

Further, as another conventional example, as in the invention described in JP-A-57-501133, a central plane is formed on the outer periphery of the boss portion forming the ignition plug hole, and for example, this central plane is formed. It is also considered to be used as a reference plane when cutting the combustion chamber. However, in this conventional example, since four central planes are provided on the outer periphery of the boss portion, a large number of irregularities are formed in the combustion chamber, which may lead to abnormal combustion due to heat pumping as described above. There is.

Means for Solving the Problems The present invention has been devised in view of the above-mentioned conventional problems, and a flat surface for forming an ignition plug hole is formed substantially in the center of the upper surface of the combustion chamber formed at the lower end of the cylinder head. In a combustion chamber structure having a flat portion, one locating portion whose upper surface is flush with the upper surface of the flat portion is continuously formed on a side portion of the flat portion, and the locating portion and each upper surface of the flat portion are continuous. It is characterized in that the locating reference surface for forming the inner surface of the combustion chamber is formed by the flat surface.

Action According to the above configuration, during cutting of the combustion chamber, the upper surface of the flat portion for forming the ignition plug hole and the upper surface of the locating portion become a continuous flat surface before the opening of the ignition plug hole. The entire flat surface can be used as a locating reference surface, and the large-area locating reference surface enables easy and highly accurate cutting work.

In particular, the present invention uses the flat portion as the locating reference plane as described above, and thus the locating portion is
A sufficient surface area can be secured by providing only one, and the surface area of the upper surface of the locating portion can be made as small as possible. As a result, it is possible to sufficiently reduce the number of irregularities on the inner surface of the combustion chamber, and it is possible to prevent abnormal combustion due to heat points.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 (A), (B) and (C). It should be noted that this embodiment is applied to a gasoline engine having four valves per cylinder as in the conventional case.

That is, the substantially conical combustion chamber 12 formed at the lower end portion of the cylinder head 11 has a pair of intake valve holes 13 and 13 and exhaust valve holes 14 and 14 at left and right symmetrical positions, and a cylinder head at the center. An ignition plug hole 15 is formed so as to penetrate through 11 in the vertical direction. Further, a circular flat portion 16 in which the spark plug hole 15 is opened is formed in the central portion of the upper surface 12a of the combustion chamber 12, and the exhaust valve holes 14 and 14 of the flat portion 16 are formed.
A small circle-shaped 1 having the same plane as the flat portion 16 on the side edge between
The two locating parts 17 are continuously and integrally formed.
That is, the upper surface of the flat portion 16 and the upper surface of the locating portion 17 are continuously and integrally formed to form the locating reference surface 20 which is a flat surface having a large surface area. Also, the flat part 16
On both sides of the connection between the locating part 17 and the locating part 17, side end parts 18, 19 flush with the both parts 16, 17 are provided to further ensure continuous integration.
Are integrally formed.

Therefore, according to this embodiment, when the combustion chamber 12 is cut, the flat portion 16, the locating portion 17, and the side end portions 18 and 19 are combined before the spark plug hole 15 is opened. The entire top surface is a gourd-shaped flat surface with a large surface area. Therefore, the entire flat surface can be used as the locating reference surface 20 during cutting. Therefore, even if the surface area of the upper surface of the locating portion 17 is small, the locating reference surface 20 of the above-mentioned large surface area using the upper surface of the flat portion 16 is secured, so that the cutting work of the combustion chamber 12 can be performed easily and with high accuracy. Can be done

Further, since the locating portion 17 can be formed as small as possible by obtaining the reference surface 20 having a large surface area, the shape change of the upper surface 12a of the combustion chamber 12 becomes small. That is, since no large concave portions or convex portions are formed around the locating portion as in the conventional case, abnormal combustion or the like at the time of fuel ignition is sufficiently prevented. Further, since the locating member 17 is arranged close to the flat portion 16, the flame propagation speed to the unburned gas accumulated in the small outer edge recess of the locating member 17 is increased, and abnormal combustion is prevented.

In this embodiment, the locating portion 17 is formed on the side of the exhaust valve holes 14 and 14, but it may be located at a position where continuous flatness with the flat portion 16 for the spark plug hole can be obtained. It is also possible to form between the exhaust valve hole 14 and the intake valve hole 13 on one side as shown by the one-dot chain line in (A) and (C), or between both intake valve holes 13 and 13. It is possible.

Effect of the Invention As is apparent from the above description, in the combustion chamber structure of the internal combustion engine according to the present invention, one locating portion that is flush with the flat portion is continuously formed on the side portion of the flat portion. During cutting of the combustion chamber, a flat surface having a large surface area including both the flat portion and the locating portion can be used as the locating reference plane. As a result, the cutting work of the combustion chamber is facilitated and highly accurate work can be obtained.

Moreover, by ensuring a large surface area of the locating reference surface, the locating part itself can be made as small as possible, and the unevenness of the combustion chamber surface is reduced, and the locating part is close to the flat part. Because of the arrangement, the flame spreadability is improved in combination with the decrease in the shape change of the combustion chamber. Therefore, abnormal combustion of the air-fuel mixture is sufficiently prevented.

[Brief description of drawings]

FIG. 1 (A) is a bottom view showing an embodiment of a combustion chamber structure of an internal combustion engine according to the present invention, and FIG. 1 (B) is II of FIG. 1 (A).
Line sectional view, the same figure (C) is the II-II line sectional view of the same figure (A),
FIG. 2 (A) is a bottom view showing a conventional combustion chamber structure, and FIG. 2 (B) is a sectional view taken along line III-III in FIG. 2 (A). 11 …… Cylinder head, 12 …… Combustion chamber, 12a …… Top surface, 1
5: Spark plug hole, 16: flat part, 17: locating part. 20 …… Locating reference plane

Claims (1)

(57) [Scope of utility model registration request] 1. In a combustion chamber structure having a flat portion for forming an ignition plug hole at a substantially central portion of an upper surface of a combustion chamber formed at a lower end portion of a cylinder head, the flat portion has a flat upper surface at a side portion of the flat portion. One locating portion that is flush with the upper surface is continuously formed, and a locating reference surface for machining the inner surface of the combustion chamber is formed by the locating portion and the continuous flat surfaces of the upper surfaces of the flat portions. Combustion chamber structure of internal combustion engine.