JPH02204624A - Combustion chamber for internal combustion engine - Google Patents

Abstract

PURPOSE:To make most of intake air so as to receive a stirring action of powerful swirls so efficiently by setting capacity in a combustion chamber space at the side of an exhaust valve, where a main flow of longitudinal swirls is generated, larger than that in another combustion chamber space at the side of an intake valve. CONSTITUTION:A shallow dished recess 20 is formed on top of a piston 12 as situated in the lower part of each exhaust valve 14. This recess 20 is formed into almost cocoon type in response to both these exhaust valves 14, and thereby capacity in a combustion chamber space in a lower part of the exhaust valve 14 is set so as to make it larger than that in another combustion chamber space in the lower part of an intake valve 13. Since a volume ratio occupied by the combustion chamber space, where powerful longitudinal swirls are generated, is taken larger than that of the side of the intake valve 13 like this, most of intake air receives a stirring action of the powerful swirl so efficiently. As a result, combustion at a partial load range or the like is accelerated, thus fuel consumption and exhaust composition are improved.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an improvement in the structure of a combustion chamber of a combustion engine.

(Prior art) In order to increase the efficiency of intake air flowing into the combustion chamber of an internal combustion engine,
There is a proposal to form a combustion chamber wall surface by a part of the spherical surface in contact with the seat surface (contact surface) of the intake valve seat, thereby smoothing the flow of intake air flowing into the combustion chamber from the gap between the intake valve and the intake valve seat. (Utility Model Publication No. 51-21203).

By the way, in an engine that has two intake valves in each combustion chamber, when generating intake swirl in the cylinder mainly with the aim of improving combustion in the partial load range, each intake valve is usually placed on the same side with respect to the center of the cylinder. Because of its location, the intake air from each intake valve collides head-on, making it difficult to maintain a swirl (horizontal swirl) along the inner circumference of the cylinder.
For this reason, the swirl is mainly a so-called vertical swirl in the direction of movement of the piston.

This vertical swirl is caused by the intake air flowing diagonally downward into the combustion chamber from the intake port as the piston descends, passes through the bottom surface of the opposing exhaust valve, hits the cylinder inner wall surface and the top surface of the piston, and forms a vertical vortex. The trend is to increase.

(Problem to be solved by the invention) However, the air flows in from between the intake valve and the wR of the intake valve seat,
The mainstream of intake air flowing along the combustion chamber wall and passing through the bottom of the exhaust valve was easily blocked by irregularities on the wall on the exhaust valve side, and vertical swirls tended to attenuate in a short period of time. .

For this reason, it is difficult to sustain the vertical swirl sufficiently from the intake stroke to the compression stroke, and the mixing of fuel and air is not promoted, resulting in insufficient combustion improvement in the partial load range.

The present invention aims to solve such problems.

(Means for Solving the Problems) Therefore, the present invention provides an arrangement in which an intake valve and an exhaust valve provided in a combustion chamber, and an intake port and an exhaust port connected thereto, are arranged to face each other so as to generate a vertical swirl in the combustion chamber. In the internal combustion engine, the volume of the combustion chamber space on the exhaust valve side where the main stream of the vertical swirl is generated is set to be larger than the volume of the combustion chamber space on the intake valve side.

(Function) Intake air flowing into the combustion chamber from the intake valve is guided from the annular gap with the intake valve seat along the wall surface of the combustion chamber that is connected to the annular gap. By the way, since the intake port faces the exhaust port, the main flow of the intake air flowing into the combustion chamber flows directly to the bottom of the opposing exhaust valve, and therefore forms a vertical swirl that wraps around downward from the front of the intake valve. In comparison, the vertical swirl that passes through the bottom surface of the exhaust valve and then wraps around downward becomes much more powerful. Since the volume ratio occupied by the combustion chamber space where this strong vertical swirl occurs is larger than that of the intake valve side, most of the intake air is efficiently subjected to the stirring action of the strong swirl. As a result, combustion is promoted in the partial load range, etc., and fuel efficiency and exhaust composition are improved.

(Example) Embodiments of the present invention will be described below based on the drawings.

The first embodiment is shown in FIGS. 1 to 4. First, in FIG. 1, 4 is a cylinder head, 11 is a cylinder block, and 12 is a piston. A combustion chamber 18 is defined therebetween.

An ignition plug 17 is attached to the cylinder head 4 at the center of the ceiling wall surface of the combustion chamber 18, and two intake valves 13 and two exhaust valves 14 are arranged around the ignition plug 17.

As shown in FIG. 2, each intake valve 13 and exhaust valve 14 are
Each pair of intake valves 13 and exhaust valves 14 are located on opposite sides of the cylinder row center line and are arranged to face each other.

Each intake valve 13 has an intake port 5 formed in parallel on the same side of the cylinder head 4 with the cylinder row center line as the border.
Similarly, the exhaust valve 14 also communicates with the parallel exhaust port 7.

The ceiling wall surface on the cylinder head side of the combustion chamber 18 is
Centering around each intake valve seat 6 and each exhaust valve seat 8,
It is formed with parts of conical surfaces 9 and 10 having apexes on and on the valve axis of the valve and extending substantially tangentially from the seating surface.

However, the extended surface of the conical surface 9 is located below the lower surface of the exhaust valve seat 8 so that the main flow of intake air flowing along the conical surface 9 can smoothly pass below the exhaust valve seat 8.

Squish areas 15 and 16 are formed around the combustion chamber 18 and are flush with the lower surface of the cylinder head 4 . The squish area 15 is formed between one conical surface and the inner circumferential surface of the cylinder, and the other squish area 16 is formed between the conical surface 10 and the inner circumferential surface of the cylinder.

As shown in FIGS. 3 and 4, a shallow dish-shaped recess 20 is formed on the top surface of the piston 12, located below the exhaust valve 14. As shown in FIGS. The recess 20 is formed in a substantially symmetrical cocoon shape corresponding to both exhaust valves 14 , and this recess 20 allows the volume of the combustion chamber space below the exhaust valve 14 to be increased from the volume of the combustion chamber space below the intake valve 13 . It is set to be larger than .

It is purified as described above, and its action will be explained next.

When the intake valve 13 opens, the intake air from the intake port 5 flows into the combustion chamber 18 through the annular gap with the intake valve seat 6.
The main flow of the intake air is guided along the conical surface 9 connected to the intake valve seat 6.The flow of intake air along the conical surface 9 flows smoothly without generating vortices, and works to increase the intake air filling efficiency even in the high speed rotation range. do.

The main flow of the intake air flows along the conical surface 9 from the intake valve 13 toward the lower surface of the exhaust valve 14 facing the intake valve 13, depending on the inclination angle of the intake port 5.

The main flow of this intake air flows downward from the lower surface of the exhaust valve 14, and further hits the top surface of the piston 12 to form a vertical swirl Se below the exhaust valve 14. A part of the intake air flows downward from the front side of the intake valve 13 with respect to the main flow of the intake air, and a vertical swirl Si that swirls in the opposite direction to the vertical swirl Se is formed on the lower surface of the intake valve 13.

The vertical swirl Se on the lower surface of the exhaust valve 14 is compared to the vertical swirl Si on the lower surface of the intake valve 13 because the exhaust valve 14 is an extension of the intake port 5 and the main flow of intake air flows into the lower surface of the exhaust valve at high speed. It becomes much more powerful.

Incidentally, the volume of the combustion chamber space on the lower surface of the exhaust valve 14 is reduced by the recess 20 formed on the top surface of the piston 12.
Since the volume is larger than the volume of the combustion chamber space on the lower surface of 3, the volume ratio of the area where strong vertical swirl is generated is high, so much of the air-fuel mixture can be efficiently combusted due to the influence of this vertical swirl. It turns out.

Therefore, the overall combustion time is shortened, and fuel efficiency and exhaust composition can be improved mainly in the partial load range.

The second embodiment shown in FIGS. 5 to 7 has two intake valves 1
3a, 13b and one exhaust valve 14, a substantially elliptical recess 20a is formed on the top surface of the piston 12 from the lower surface of the intake valve 13M to the lower surface of the exhaust valve 14. It is formed. The four portions 20a are formed with an inclined bottom surface 21 that is gradually deeper toward the exhaust valve side than the intake valve side.

In this case as well, since the volume of the combustion chamber space on the bottom surface of the exhaust valve 14 is larger than the combustion chamber space on the bottom surface of the intake valve 13a, a large amount of the air-fuel mixture can be efficiently combusted by a strong vertical swirl. .

The third embodiment shown in FIGS. 8 to 10 is a two-valve engine having one intake valve 13 and one exhaust valve 14. The recess 20b on the lower surface of the valve 14 is made larger than the recess 20c on the lower surface of the intake valve 13 to expand the volume of the combustion chamber space. This shortens the combustion time on the exhaust valve side, where the main flow of intake air gathers, and improves the overall combustion characteristics.

In the fourth embodiment shown in FIG. 11, by setting the inclination β of the valve shaft of the exhaust valve 14 to be smaller than the inclination α of the valve shaft of the intake valve 13, the combustion chamber wall surface 22 on the exhaust valve side is This increases the volume of the combustion chamber space on the exhaust valve side.

Furthermore, in the fifth embodiment shown in FIG. 12, in addition to the inclination of the valve shaft, the valve diameter (throat diameter) Di of the intake valve 13 is
Either make the apex angle θi of the conical surface 9 on the intake valve side smaller than the valve diameter De of the exhaust valve 14, or change the apex angle θi of the conical surface 10 on the exhaust valve side.
By making it smaller than e, the volume of the combustion chamber space on the exhaust valve side is relatively expanded.

The sixth embodiment shown in FIGS. 13 and 14 has a conical surface 10 in a region sandwiched between two exhaust valves 14a and 14b.
The angles of the slopes a and 10b are made gentler than the other conical surfaces 10 to expand the volume of the combustion chamber space on the lower surface of the exhaust valve 14. In this case, the area of the squish area 16a on the exhaust valve side is also reduced, which contributes to an increase in volume.

Further, the seventh embodiment shown in FIG. 15 also has an exhaust valve 1.
The wall surface of the combustion chamber in the region sandwiched between 4a and 14b is configured not by the conical surface 10 but by a gently curved surface or flat surface 23 with a larger curvature than the conical surface 10, and the squish area 16
By reducing b, the volume of the combustion chamber space on the lower surface of the exhaust valve is increased.

Furthermore, in the eighth embodiment shown in FIG. 16, by removing the squish area 16b and leaving only a curved or flat surface 23, the volume of the combustion chamber space on the lower surface of the exhaust valve is further increased.

Next, in a ninth embodiment shown in FIG. 17, the valve diameter of the intake valve 13b is set larger than that of the intake valve 13a, and the exhaust valve 14a is set larger than the diameter of the exhaust valve 14b.

That is, by arranging the intake and exhaust valves so that the large intake valve 13b and the small exhaust valve 14b face each other, the intake air from the intake valve 13b through which the main flow of intake air flows is transferred to the exhaust valve 14b.
By deflecting the gas toward the lower surface of the exhaust valve 14a, which has a larger volume than that of the exhaust valve 14a, a strong vertical swirl can be generated past the lower surface of the ignition plug 17.

Furthermore, the tenth embodiment shown in FIG.
Of the intake valves a and 13b, one of the intake valves 13b has a larger valve diameter, and a single exhaust valve 14 is disposed opposite the intake valve 13a, which has a smaller valve diameter. In this case as well, the intake air from the intake valve 13b, through which the main flow of intake air flows, crosses toward the lower surface of the exhaust valve 14, forming a strong vertical swirl.

Therefore, in both the ninth and tenth embodiments, the main flow of the intake air flows to the lower surface of the exhaust valve having the larger volume of the combustion chamber space, and the strong vertical swirl generated at this time improves combustion.

(Effects of the Invention) As described above, according to the present invention, since the intake port faces the exhaust port, the main flow of the intake air flowing into the combustion chamber directly flows to the lower surface of the opposing exhaust valve. Therefore, compared to the vertical swirl that wraps around downward from the front of the intake valve, the vertical swirl that wraps around downward after passing through the bottom surface of the exhaust valve is much stronger, and this strong vertical swirl is generated. Since the volume ratio occupied by the combustion chamber space on the bottom surface of the exhaust valve is larger than that on the intake valve side, most of the intake air is efficiently subjected to the stirring action of the powerful swirl, and as a result, the overall combustion is promoted, improving fuel efficiency and exhaust composition.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view (A-A section in FIG. 2) showing the first embodiment of the present invention, FIG. 2 is a plan view, FIG. 3 is a plan view of the piston, and FIG. 4 is a plan view of the piston. 3 is a sectional view taken along line B-B, FIG. 5 is a plan view showing the second embodiment, FIG. 6 is a plan view of the piston, and FIG. 7 is a sectional view taken along line C-C in FIG.
FIG. 8 is a plan view showing the third embodiment, FIG. 9 is a plan view of the piston, and FIG. 10 is a sectional view taken along line D-D in FIG. 9.
FIG. 11 is a longitudinal sectional view showing the fourth embodiment, FIG. 12 is a longitudinal sectional view showing the fifth embodiment, FIG. 13 is a plan view showing the sixth embodiment, and FIG. 14 is a longitudinal sectional view showing the fifth embodiment. EE line sectional view, 1st
5 is a plan view showing the seventh embodiment, FIG. 16 is a plan view showing the eighth embodiment, FIG. 17 is a plan view showing the ninth embodiment, and FIG. 18 is a plan view showing the tenth embodiment. FIG. 4... Cylinder head, 5... Intake port, 6...
・Intake valve seat, 8... Exhaust valve seat, 9, 10...
- Conical surface, 11... Cylinder block, 12... Piston, 13... Intake valve, 14... Exhaust valve, 17.
...Spark plug, 18...Combustion chamber. Figure 6 Figure Figure Figure 9 Figure 10 Figure 11 Figure 1112 Figure 15 Figure 16 Figure 13 Figure 14 Figure 17 Figure $18

Claims (1)

[Claims] In an internal combustion engine in which an intake valve and an exhaust valve provided in a combustion chamber, and an intake port and an exhaust port connected thereto are arranged oppositely to generate a vertical swirl in the combustion chamber,
A combustion chamber for an internal combustion engine, characterized in that the volume of the combustion chamber space on the exhaust valve side, where the main stream of the vertical swirl is generated, is set larger than the combustion chamber space on the intake valve side.