JPS6231616Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to the combustion chamber structure of an engine.

In order to improve combustion efficiency by promoting vaporization/atomization of fuel and combustion speed, it is said to be effective to swirl the intake air-fuel mixture in a vortical shape to form a swirl. To this end, by guiding the intake air-fuel mixture in the circumferential direction of the combustion chamber and swirling it, the vortex state of the air-fuel mixture supplied to the combustion chamber is strengthened, promoting fuel vaporization/atomization and combustion speed. Japanese Utility Model Publication No. 1983-48101 proposes an engine that is capable of burning fuel leaner than the air-fuel ratio (lean mixture), thereby improving fuel efficiency.

This type of engine forms a hemispherical combustion chamber in the cylinder head, which includes intake and exhaust valves having central axes inclined with respect to the mating surface with the cylinder block, and a spherical inner wall surface. A guide wall that protrudes into the combustion chamber along a part of the outer periphery of the intake valve seat is formed between the opened intake port and the exhaust port, and this guide wall directs the intake air-fuel mixture in the circumferential direction of the combustion chamber. It is configured to rotate.

On the other hand, a recess is provided in either the intake port or the exhaust port that opens on the inner wall surface of the cylinder head of the engine, and in the area that surrounds the spark plug, so that the inside of the cylinder head when the piston is at top dead center is provided with a recess. An engine in which a compact combustion chamber formed by the above-mentioned recess is formed between the wall surface and the upper surface of the piston has been proposed in JP-A-50-107309 and JP-A-54-65207.

By forming a compact combustion chamber like in this type of engine, the flame propagation distance is shortened, so knocking does not occur even when the compression ratio is increased, and combustion efficiency can be increased. By increasing the ratio, effective combustion of a lean air-fuel mixture can be expected, which can improve fuel efficiency. Also,
By forming a compact combustion chamber on the intake port side, the walls of the combustion chamber can be used to form a swirl in the intake air-fuel mixture, which promotes fuel vaporization/atomization and combustion speed, increasing combustion efficiency. .

Further, an engine is well known in which a squish zone having a minute gap is formed between the inner wall surface of the cylinder head and the upper surface of the piston at the end of the compression stroke adjacent to the recess. Such an engine pushes the squish flow generated in the squish zone into the combustion chamber and sprays it against the air-fuel mixture in the combustion chamber to actively flow the air-fuel mixture, thereby vaporizing and atomizing the fuel. The combustion rate is accelerated and the combustion efficiency is increased.

In other words, the most effective means to increase fuel vaporization, atomization, and combustion speed to increase combustion efficiency and improve fuel efficiency is to guide the intake air-fuel mixture into the cylinder while swirling it, and to convert this swirling flow into a compact cylinder. The method is to introduce the fuel into the combustion chamber and actively flow it in a swirling manner within the combustion chamber.

However, in the engine configured to form the above-mentioned compact combustion chamber, the intake port or exhaust port is opened in a small recess provided to form the compact combustion chamber, so the inner surface of the recess is placed around each port. There is a problem in that the intake and exhaust air collides with the inner surface of the recess, increasing the intake and exhaust resistance and reducing the intake and exhaust efficiency.

This idea was devised in view of the above-mentioned conventional problems, and it guides the intake air-fuel mixture into the cylinder in a swirling manner, and actively flows the swirled air-fuel mixture into a compact combustion chamber in a swirling manner. To provide a combustion chamber structure for an engine capable of increasing combustion efficiency by promoting vaporization/atomization and combustion speed of fuel, improving fuel efficiency, and improving intake/exhaust efficiency by reducing intake/exhaust resistance. With the goal.

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

FIG. 1 shows a perspective view of an engine to which the combustion chamber structure according to the invention is applied, and FIG. 2 shows a bottom view of the cylinder head. In these figures, 1 is a cylinder block, 2 is a cylinder head, and 3 is a piston.As is clear from FIG. 3, the cylinder head 2 is formed with a hemispherical recess 4.
An intake port 6 and an exhaust port 7 are opened on the inner surface of the cylinder head 2, that is, on the inner wall surface 5 of the cylinder head 2. The intake port 6 is connected to an intake passage 8, and the exhaust port 7 is connected to an exhaust passage 9.
are connected to each other. An intake valve seat 10 is attached to the intake port 6, and an intake valve 12 (see FIG. 1) having a central axis _C1 inclined with respect to the mating surface 11 with the cylinder block 1 is provided so as to be openable and closable. An exhaust valve seat 13 is attached to the exhaust port 7, and the central axis C ₂ is inclined with respect to the mating surface 11.
An exhaust valve 14 (see FIG. 1) is provided so as to be openable and closable.

Reference numeral 15 designates a recessed portion for a spark plug, and this recessed portion 15 is provided around the recessed portion 4 between the intake port 6 and the exhaust port 7, and the electrode portion of the spark plug 16 faces the recessed portion 15. The intake passage 8 is curved and communicates with the intake port 6 so that intake air flows toward the spark plug recess.

17 indicates a protrusion. This protrusion 17 is for swirling and guiding the intake air into the cylinder, and is located between the intake port 6 and the exhaust port 7 of the hemispherical recess 4 of the cylinder head 2, and is located in the recess for the spark plug. It is formed on the opposite side of the position where 15 is provided. A guide wall 18 is formed along the outer periphery of the intake port 6 to guide the intake air into the cylinder, and the guide wall 18 is formed perpendicularly to the mating surface 11, as shown in FIG. has been done. In addition, the exhaust port 7 of the protrusion 17
The side wall of the side, that is, the protruding portion side surface 19 is formed into a curved surface having approximately the same curvature as the inner wall surface 5 so as to smoothly continue with the inner wall surface 5 of the hemispherical recess 4, and the protruding portion side surface 19 The lower surface 20 is formed at a height that is almost flush with the mating surface 11, and the ridge line 21 where the guide wall 18 and the protrusion side surface 19 intersect
is formed into a smoothly continuous curve with respect to the inner wall surface 5.

The upper surface of the piston 3 facing the intake port 6 has a raised portion 2 raised toward the cylinder head 2.
2 is formed. As is clear from FIGS. 1 and 5, the protruding portion 22
an arcuate wall 23 formed with opposing curvatures along the guide wall 18; and a curvature that extends from one end 23a of the arcuate wall 23 to the vicinity of the spark plug recess 15 in parallel with the outer circumferential curvature of the piston 3. wall 24;
It is formed by a side surface 25 formed by a curved line extending from the other end 23b of the arcuate wall 23 to the tip 24a of the curvature wall 24, and when the piston 3 is at the top dead center as shown in FIG. The height is set such that a minute gap 26 is formed between the upper surface 22a of the cylinder head 2 and the inner wall surface 5 of the cylinder head 2.

In the above configuration, the intake air flowing into the cylinder from the intake port 6 via the intake passage 8 is
The directionality is guided by the guide wall 18 of the first
As shown by arrow A in the figure and FIG. 2, a swirling flow swirls in the circumferential direction. In this case, since only the guide wall 18 of the protrusion 17 exists around the intake port 6 (because the piston 3 moves downward during the intake stroke), intake resistance is small and intake efficiency is improved. .

The above-mentioned swirl flow is formed all around the inside of the cylinder and is maintained without attenuation even when the compression stroke begins. As the piston 3 approaches the compression top dead center, the opposing gap between the inner wall surface 5 of the cylinder head 2 on the side of the intake port 6 and the upper surface 22a of the raised portion 22 of the piston 3, and the gap between the flat surface 3a of the piston 3 and the protruding portion 17. Since the opposing gap between the cylinder and the lower surface 20 gradually becomes smaller, the swirl that had been formed around the entire circumference of the cylinder shifts toward the exhaust port 7 side. In this case, since the side surface 19 of the protruding portion 18 is formed into a curved surface that is smoothly continuous with the inner wall surface 5, the exhaust port 7 can be closed without attenuating the swirl.
It can be moved smoothly to the side.

At the end of the compression stroke, a compact cylinder is formed which is defined by the side surface 19 of the protruding portion 17, the side surface 25 of the raised portion 22, the inner wall surface 5 of the cylinder head 2 where the exhaust port 7 opens, and the flat surface 3a of the piston 3. Combustion chamber 2
7 (see FIG. 7) is formed, and the air-fuel mixture flows in a swirl within this combustion chamber 27.

On the other hand, at the end of the compression process, a protrusion 1 is formed between the inner wall surface 5 of the cylinder head 2 and the upper surface of the piston 3.
A squishing zone 26a of a minute gap 26 is formed between the lower surface 20 of the piston 7, the piston flat surface 3a, the inner wall surface 5 of the cylinder head 2 at the portion where the intake port 6 opens, and the raised portion 22, and the squishing zone 26a is formed in this squishing zone 26a. The resulting squish flow is blown onto the air-fuel mixture within the combustion chamber 27, causing the air-fuel mixture to actively flow. Therefore, the vaporization/atomization and combustion speed of the fuel are promoted, and the combustion efficiency is improved.

Although the above embodiment describes an example in which the compact combustion chamber 27 is formed on the exhaust port 7 side, this invention is not limited to the above embodiment. Even if it is formed on the intake port 6 side, the same effects as in the above embodiment can be obtained. However, by forming the combustion chamber 27 on the exhaust port 7 side as in the above embodiment, the air-fuel mixture in the combustion chamber 27 is heated to a high temperature by the high-temperature exhaust valve 14, so combustibility is improved. Combustion efficiency can be increased.

As explained above, according to this invention, the intake air-fuel mixture is guided into the cylinder while swirling, this swirling flow is introduced into the compact combustion chamber, and the air-fuel mixture in the combustion chamber is actively controlled by the squishing flow. Because it can flow in a vortex, fuel vaporization and
Atomization and combustion rate are promoted, improving combustion efficiency. Furthermore, the combustion chamber is formed by the side surface of the protrusion of the cylinder head, the side surface of the protrusion of the piston, the inner wall surface of the cylinder head where either the intake or exhaust port opens, and the flat surface of the piston. Except at top dead center and near top dead center, the area around the intake/exhaust ports is wide open, so intake/exhaust resistance is small and intake/exhaust efficiency is improved.

[Brief explanation of drawings]

Figure 1 is a schematic perspective view of an engine to which the combustion chamber structure of this invention is applied, Figure 2 is a bottom view of the cylinder head, Figure 3 is a sectional view taken along the - line in Figure 2, and Figure 4. is a sectional view taken along the - line in Fig. 3, Fig. 5 is a bottom view showing the relationship between the protruding part of the cylinder head and the protruding part of the piston, and Fig. 6 is a sectional view taken along the - line in Fig. 5. figure,
FIG. 7 is a sectional view taken along the same line. 1... Cylinder block, 2... Cylinder head, 3... Piston, 3a... Flat surface, 5... Inner wall surface, 6... Intake port, 7... Exhaust port, 1
7...Protrusion part, 18...Guide wall, 19...Protrusion part side surface, 20...Protrusion bottom surface, 22...Protuberance part, 2
5... Side surface of the raised portion, 26... Minute gap, 26a...
...Suitable zone, 27...Combustion chamber.

Claims (1)

[Scope of utility model registration request] A protrusion having a guide wall in a position close to an intake port on the inner wall of the cylinder head disposed on the upper part of the cylinder into which the piston is slidably fitted, guides the intake air flowing from the intake port to swirl into the cylinder. forming a raised portion, and forming a raised portion in which the upper surface portion of the piston facing one of the intake and exhaust ports is raised toward the cylinder head side;
Between the inner wall of the cylinder head and the upper surface of the piston when the piston is at top dead center, the lower surface of the protrusion, the flat surface of the piston, the inner wall surface of the cylinder head at the portion where the one port opens, and the raised portion are formed. The cylinder head is defined by a squeezing zone with a small gap formed by the piston, the side surface of the protrusion, the side surface of the protrusion, the inner wall surface of the cylinder head at the portion where the remaining ports of the intake and exhaust ports open, and the flat surface of the piston. A combustion chamber structure for an engine characterized by forming a combustion chamber.