JPH05118221A - Internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent occurrence of abnormal combustion such as detonation, etc., as much as possible, and enhance output by providing an expansion chamber that communicates with a combustion chamber at the peripheral part of the combustion chamber. CONSTITUTION:In a cylinder head 1, a combustion chamber 10 is comparted by a semispherical recessed part 3 between the upper surface 9a of a piston 9 that holds a position in the vicinity of an upper dead point, and an annular squish area 11 is comparted by a flat part 4. Further, an annular expansion chamber 12 that communicates with the combustion chamber 10 through the squish area 11 is comparted by a recessed groove 5. Rise of internal pressure due to ignition is reduced by the action of the expansion chamber 12 at the peripheral part of the combustion chamber 10, and temperature rise of end gas is suppressed, thereby occurrence of abnormal combustion such as detonation, etc., can be prevented as much as possible even if the compression ratio is increased so as to try improvement of output.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to internal combustion engines.

[0002]

2. Description of the Related Art In recent years, internal combustion engines, especially engines mounted on vehicles such as motorcycles and four-wheeled vehicles, tend to gradually increase their compression ratios as their output increases.

[0003]

However, when the compression ratio is increased in an ordinary internal combustion engine, the unburned air-fuel mixture in front of the propagation flame (hereinafter referred to as end gas) is used.
However, the pressure and temperature become higher.

For this reason, abnormal combustion such as detonation is likely to occur in the peripheral portion of the combustion chamber, and there is a risk of damaging parts such as the piston and the cylinder head.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an internal combustion engine capable of further improving the output while preventing abnormal combustion such as detonation as much as possible. Has a purpose.

[0006]

According to the present invention, an expansion chamber communicating with the combustion chamber is provided at the peripheral portion of the combustion chamber.

[0007]

According to the above construction, the rise in internal pressure due to ignition is mitigated in the expansion chamber, and the rise in temperature of the end gas is suppressed.

[0008]

The present invention will be described in detail below with reference to the drawings illustrating the embodiments. FIG. 3 conceptually shows an internal combustion engine according to the present invention, and exemplifies a two-cycle engine mounted on a motorcycle.

As shown in FIGS. 1 and 2, in this two-cycle engine, a hemispherical recess 3 is formed in the center of a portion of the cylinder head 1 facing the cylinder 2, and a flat portion is formed around the recess. 4 is formed, and a groove 5 is formed around the flat portion 4.

The recess 3 is formed with a sufficient depth from the cylinder block mounting surface 1a of the cylinder head 1 and has a plug mounting hole 1b at the center thereof.

The flat portion 4 has an annular shape surrounding the recess 3 and is arranged concentrically with the recess 3. Figure 1
As is clear from the above, the flat portion 4 is formed parallel to the mounting surface 1a at a position slightly retracted inward from the cylinder block mounting surface 1a.

As shown in FIGS. 1 and 2, the concave groove 5 has
The outer diameter thereof forms an annular shape having the same diameter as that of the cylinder 2, and is continuous with the flat portion 4 via the inclined portion 6, and the flat portion 4
It is arranged concentrically with. The groove 5 is formed slightly deeper than the flat portion 4 and is arranged over the entire circumference of the flat portion 4. As is clear from FIG. 1, the inclined portion 6 has an obtuse angle θ with the central axis C of the cylinder 2 and is in the bottom dead center direction (downward in the figure).
It is inclined in a direction in which the diameter decreases toward.

As shown in FIG. 3, a cylinder block 7 is mounted on the cylinder block mounting surface 1a of the cylinder head 1, and an ignition plug 8 is screwed into the plug mounting hole 1b.

In this state, the cylinder head 1
As shown in FIG. 1, a combustion chamber 10 is defined by the hemispherical concave portion 3 between the combustion chamber 10 and the upper surface 9a of the piston 9 which is located near the top dead center, and the flat portion 4 forms an annular shape. The squish area 11 is defined, and the combustion chamber 10 is further defined by the groove 5 through the squish area 11.
To define an annular expansion chamber 12 communicating with. In addition, the flat portion 4 and the upper surface 9 of the piston 9 occupying near the top dead center
The squish area 11 defined with a forms a minimum clearance with the upper surface 9a of the piston 9 which is occupied near the top dead center.

According to the two-cycle engine constructed as described above, due to the action of the expansion chamber 12, the increase in internal pressure due to ignition is mitigated in the peripheral portion of the combustion chamber 10, and the temperature rise of the end gas is suppressed. Therefore, even when the compression ratio is increased to improve the output, the occurrence of abnormal combustion such as detonation can be prevented as much as possible.

The above combustion chamber 10 and squish area 1
1 and the expansion chamber 12 are continuous on a smooth surface,
Since there is no part protruding at an acute angle, detonation does not occur due to the hot spot.

Moreover, since the expansion chamber 12 is partitioned from the combustion chamber 10 by the squish area 11, the shape of the combustion chamber 10 and the combustion chamber 10 and the squish area 11 are separated.
The effect on the volume ratio etc. is as small as possible, so even when applied to an existing engine, the output will decrease, etc.
The output characteristics do not change significantly.

In the above embodiment, the two-cycle engine mounted on the motorcycle is shown as an example, but the present invention is not limited to this, and an internal combustion engine mounted on a vehicle other than the motorcycle is also possible. Alternatively, it may be something other than a two-cycle engine.

Further, in the above embodiment, the cylinder head 1
Although the expansion chamber 12 is provided on the extension region of the cylinder 2 in FIG. 1, it may be provided on the outer peripheral region of the cylinder 2. Although the expansion chamber 12 is defined by forming the concave portion 3 in the cylinder head 1 in the embodiment, the expansion chamber may be defined by cutting the peripheral edge of the upper surface 9a of the piston 9. The expansion chamber may be formed so as to straddle the cylinder head 1 and the cylinder block 7.

Further, in the above embodiment, since the spark plug 8 is arranged at the center of the combustion chamber 10, the combustion chamber 10
Although the expansion chamber 12 is provided around the entire circumference of the above, it is not always necessary to provide the expansion chamber 12 in the present invention, and the expansion chamber may be provided partially.

[0021]

As described above, according to the internal combustion engine of the present invention, the rise in internal pressure due to ignition is mitigated in the expansion chamber, and the rise in end gas temperature is suppressed, so that abnormal combustion such as detonation is prevented. While suppressing the occurrence as much as possible, the compression ratio can be increased, and the output can be further improved.

[Brief description of drawings]

FIG. 1 is a sectional side view conceptually showing a main part of an internal combustion engine according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a cross-sectional side view showing the whole thereof.

[Explanation of symbols]

 10 Combustion chamber 12 Expansion chamber

Claims (1)

[Claims] 1. An internal combustion engine, characterized in that an expansion chamber communicating with the combustion chamber is provided at a peripheral portion of the combustion chamber.