JPS6328210B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark ignition internal combustion engine with an improved combustion chamber to improve fuel consumption.

[Conventional technology and its problems]

Increasing the compression ratio is effective in improving the thermal efficiency of internal combustion engines, but increasing the compression ratio causes knocking in the low rotation range, so there is a certain limit to improving the compression ratio, and it is not practical. It was not possible to improve fuel efficiency. And how to suppress the occurrence of knocking by improving the combustion chamber.

(1) Shorten the distance from the electrode of the spark plug looking into the combustion chamber to every corner of the combustion chamber, that is, the flame propagation distance (first means).

(2) To improve the flame propagation speed and shorten the combustion time by giving as much turbulence as possible to the intake air mixture in the combustion chamber (second means).

It is well known that there are other means.

In this case, in order to obtain the latter second means, specific examples include providing a swirl when the air-fuel mixture is taken into the combustion chamber, forming a squish area around the combustion chamber, and using these in combination. Therefore, forming a squish area around the combustion chamber makes the combustion chamber more compact and is extremely effective for the first method.

As prior art, Japanese Utility Model Application Publication No. 56-129525 and Japanese Utility Model Application Publication No. 56-45120 disclose that, in addition to forming a squeezing area around the combustion chamber, the electrode part of the spark plug is placed approximately in the center of the combustion chamber. It is proposed that it should be projected towards.

However, this prior art has a problem in that the electrode portion of the spark plug that protrudes toward the approximate center of the combustion chamber is susceptible to direct impact from the squish flow from the squish area formed around the combustion chamber. That is, the top surface of the piston in this prior art is completely flat with no depression in its center, and as the piston approaches top dead center, the squishing flow that occurs between it and the bottom surface of the cylinder head As the top surface is pushed up from the center, it tends to eject obliquely upward toward the center of the combustion chamber, which is formed in the depression on the bottom surface of the cylinder head. The squishing flow from the squishing area near the electrode portion of the plug directly hits the electrode portion of the spark plug protruding into the combustion chamber, thereby blowing out the spark at the electrode portion.

Therefore, in this prior art, it is not possible to increase the protrusion of the electrode part of the spark plug into the combustion chamber.
This is insufficient for the first means.

In addition to protruding the electrode part of the spark plug toward the center of the combustion chamber as described above, the present invention also forms a skid area around the combustion chamber.
In implementing the first and second means, it is an object of the present invention to reliably prevent the spark from the electrode portion of the ignition plug from being blown out due to the squish flow as described above.

[Means for solving problems]

In order to achieve this object, the present invention has an intake port and an exhaust port opened in a combustion chamber formed by recessing the lower surface of a cylinder head, and also directs an electrode of an ignition plug screwed onto the cylinder head into the combustion chamber. In the internal combustion engine, the circumferential contour of the combustion chamber with respect to the lower surface of the cylinder head is defined by the circumferential contour of the cylinder bore between the opening of the intake port and the opening of the exhaust port and in the vicinity of the electrode portion of the spark plug. The piston is inserted into the combustion chamber to form a tightness area for the top surface of the piston outside the circumferential contour of the combustion chamber. A recess having a peripheral contour surrounding the vicinity of the opening and the electrode portion of the spark plug is provided, and a portion of the peripheral contour of the recess on the top surface of the piston that surrounds the vicinity of the electrode portion of the spark plug is provided in the combustion chamber. It is configured to be located radially outside a portion of the circumferential contour that surrounds the vicinity of the electrode portion of the ignition plug, and of the squish area, a squish area near the electrode portion of the spark plug is configured. , larger in the area between the electrode part of the spark plug and the opening of the intake port, and in the area between the electrode part of the spark plug and the opening of the exhaust port, and smaller in the part outside the electrode part of the spark plug. It was configured as follows.

[Operations and Effects of the Invention] That is, as described above, the present invention provides that the top surface of the piston includes a portion near the opening of the intake port;
A recess having a circumferential contour surrounding the vicinity of the opening of the exhaust port and the electrode portion of the spark plug is provided, while a portion of the circumferential contour of the recess on the top surface of the piston that surrounds the vicinity of the electrode portion of the spark plug is provided. By configuring the combustion chamber to be located radially outside of a portion surrounding the vicinity of the electrode portion of the spark plug in the circumferential contour of the combustion chamber, the electrode portion of the spark plug is located within the squish area on the lower surface of the cylinder head. The skiing area near the area is
The piston protrudes into the recess, and the squish flow from the squish area near the electrode part of the spark plug is pushed down into the recess on the top surface of the piston by the pushing down action of the squish area in the protruding part. Since the flow is biased toward the bottom surface of the spark plug, it is possible to prevent the squish flow from directly hitting the electrode part of the spark plug.

In addition, as mentioned above, the squish area in the vicinity of the electrode part of the spark plug is replaced by the squish area between the electrode part of the spark plug and the opening of the intake port, and the squish area near the electrode part of the spark plug. The part between the electrode part of the spark plug and the opening of the exhaust port is large, and the part outside the electrode part of the spark plug is small. Of the squishing streams ejected toward the spark plug, only the squishing streams directed toward the electrode portion of the spark plug can be weakened more than the other squishing streams. Therefore, according to the present invention, the synergistic effect of the above and the above can prevent the spark from blowing out due to the squishing flow without impairing the effect of the squishing flow. It also has the effect of reliably achieving stable ignition and combustion.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 indicates a cylinder block, reference numeral 2 indicates a cylinder head fastened to the upper surface of the cylinder block 1, and reference numeral 3 indicates an inner cylinder bore 4 of the cylinder block 1. 5 is a spherical or polyspherical combustion chamber formed by recessing the lower surface of the cylinder head 2, and 6 is a piston that reciprocates in the cylinder head 2 so that an electrode portion 7 protrudes into the combustion chamber 5. Each of the spark plugs screwed onto the head 2 is shown.

Reference numeral 8 denotes a longitudinal center line 9 passing through the center of the cylinder bore 4 in the same direction as the engine crankshaft (not shown) in a plan view of the cylinder head 2.
The reference numeral 11 indicates an intake port that communicates between the combustion chamber 5 and one side surface 10 parallel to the longitudinal center line 9, and an exhaust port that communicates the combustion chamber 5 with the other side surface 12 that is parallel to the longitudinal centerline 9.

The opening 8' of the intake port 8 to the combustion chamber 5 and the opening 11' of the exhaust port 11 to the combustion chamber 5 are as follows:
located on both sides of the longitudinal center line 9 and on both sides of a perpendicular center line 13 passing through the center point of the cylinder bore 4 and perpendicular to the longitudinal center line 9;
An intake valve 14 is provided at the opening 8' of the intake port 8, an exhaust valve 15 is provided at the opening 11' of the exhaust port 11, and the spark plug 6 is provided at the opening 8' of the intake port 8. On the other hand, they are provided at positions facing each other with the longitudinal centerline 9 interposed therebetween.

Further, in the middle part of the intake port 8, the main flow of the air-fuel mixture entering the combustion chamber 5 through the opening 8' is exhausted through the electrode part 7 of the spark plug 6 as shown by arrow A in FIG. The valve 15 is curved in a plan view so as to form a swirl flow directed toward substantially directly below the valve 15 .

In the combustion chamber 5 recessed in the lower surface of the cylinder head 2, a circumferential contour 16 surrounding the opening 8' of the intake port 8, the opening 11' of the exhaust port 11, and the electrode portion 7 of the spark plug 6 is defined by the spark plug 6. The circular shape of the cylinder bore 4 is such that it has intrusions 16a and 16b into the combustion chamber 5 near the electrode portion 7 and between the opening 8' of the intake port 8 and the opening 11' of the exhaust port 11, respectively. On the lower surface of the cylinder head 2, which is located inside the circumferential contour 17 and outside the circumferential contour 16 of the combustion chamber 5, there is a skid area 18 for the top surface 3' of the piston 3.
is formed to surround the electrode portion 7 of the spark plug 6, the opening 8' of the intake port 8, and the opening 11' of the exhaust port 11.

On the other hand, a recess 19 having an appropriate depth and a flat bottom surface is formed in the center of the top surface 3' of the piston 3. The circumferential contour 20 of this recess 19 with respect to the piston top surface 3' is located near the electrode portion 7 of the spark plug 6 and the opening 8' of the intake port 8, as well as the opening 1 of the exhaust port 11 in plan view.
1', and of the peripheral contour 20 of the recess 19, the opening 8' of the intake port 8
and the vicinity of the opening 11' of the exhaust port 11 are defined as the part 20b surrounding the vicinity of the opening 8' of the intake port 8 and the opening 11' of the exhaust port 11, of the peripheral contour 16 of the combustion chamber 5. The circumferential contour 20 of the recess 19 of the piston top surface 3' is generally aligned with the recess 16b surrounding the piston top surface 3', or is located on the inside in the radial direction of the cylinder bore 4. , the part 20a surrounding the electrode part 7 of the ignition plug 6 is connected to the combustion chamber 5.
It is configured to be located closer to the outside in the radial direction of the cylinder bore 4 than a portion 16a surrounding the vicinity of the electrode portion 7 of the spark plug 6 out of the circumferential contour 16 in the figure.

Furthermore, out of the squish area 18 on the lower surface of the cylinder head 2, the squish area near the electrode portion 7 of the spark plug 6 is divided between the electrode portion 7 of the spark plug 6 and the opening 8' of the intake port 8. The part between, and the electrode part 7 of the spark plug 6 and the exhaust port 1
The portion between the spark plug 6 and the opening 11' of the spark plug 6 is large, and the portion outside the electrode portion 7 of the spark plug 6 is small.

In this configuration, during the intake stroke associated with the downward movement of the piston 3, the intake air mixture from the intake port 8 flows into the combustion chamber 5 and the cylinder bore 4 at the electrode of the spark plug 6 as shown by arrow A in FIG. After passing over the part 7 and cooling it, the air is sucked in as a swirl flow in a direction substantially directly below the exhaust valve 15.

Then, when the intake stroke ends, the intake valve 14 closes, and a compression stroke occurs due to the upward movement of the piston 3.
When the top surface 3' of the piston 3 approaches the bottom surface of the cylinder head 2 at the end of the compression stroke, the piston 3
A compression area 1 surrounding the top surface 3' of the combustion chamber 5 and the combustion chamber 5
8, and the squishing flow is ejected into the combustion chamber 5, so the swirl in the combustion chamber 5 is accelerated and becomes violently turbulent, increasing the flame propagation speed. improved,
Moreover, the combustion time of the air-fuel mixture is shortened.

In this case, the compression area 1 surrounding the combustion chamber 5
8, the squishing flow from the squishing area located on the opposite side of the combustion chamber 5 from the ignition plug 6 becomes the strongest and reaches the squishing area as shown by arrow C in FIG. The squish flow in the direction of arrow C crosses the combustion chamber 5 and then reaches the electrode part 7 of the spark plug 6.
Therefore, the squishing flow in the direction of arrow C will not directly hit the electrode portion 7 of the spark plug 6 and blow out the spark in the electrode portion 7.

On the other hand, near the electrode portion 7 of the spark plug 6,
The electrode portion 7 of the spark plug 6 in the circumferential contour 16 of the combustion chamber 5
The part 16a surrounding the vicinity of the combustion chamber 5 is located inside the part 20a surrounding the vicinity of the electrode part 7 of the spark plug 6 in the peripheral contour 20 of the recess 19 of the piston top surface 3'. A portion 16a of the circumferential contour 16 that surrounds the vicinity of the electrode portion 7 of the spark plug 6 is placed inside a portion 20a of the circumferential contour 20 that surrounds the vicinity of the electrode portion 7 of the spark plug 6 in the recess of the piston top surface 3'. Since it is configured to protrude, the squish flow near the electrode portion 7 of the ignition plug is pushed down by the squish area 18 of the protruding portion, as shown by arrow B in FIG. It is ejected obliquely downward toward the bottom of the recess 19 in the surface 3'.

Moreover, among the squish area 18 on the lower surface of the cylinder head 2, the squish area near the electrode portion 7 of the spark plug 6 is
between the electrode part 7 of the spark plug 6 and the opening 8' of the intake port 8, and the part between the electrode part 7 of the spark plug 6 and the exhaust port 11.
The structure is such that the area between the spark plug 6 and the opening 11' is large and the area outside the electrode part 7 of the spark plug 6 is small. Among the squishing flows ejected toward the interior of the spark plug 5, the squishing flow in the direction toward the electrode portion 7 of the spark plug 6 is weakened compared to other squishing flows. Coupled with the fact that the squishing flow from the squishing area is directed in the diagonally downward direction of arrow B as described above, it is ensured that the squishing flow blows out the spark at the electrode part 7 of the spark plug 6. It can be resolved.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional front view of the main parts of the engine, FIG. 1 is a cross-sectional view from FIG. The figure is a - view plan view of Fig. 1, and Fig. 4 is a - view of Fig. 3.
FIG. 3 is an enlarged cross-sectional view. 1... Cylinder block, 2... Cylinder head, 3... Piston, 4... Cylinder bore, 5...
...Combustion chamber, 6...Spark plug, 7...Electrode part, 8...
Intake port, 11... Exhaust port, 16... Circumferential contour of combustion chamber, 18... Squeeze area, 3'...
...Piston top surface, 19...recess, 20...circumferential contour of the recess.

Claims (1)

[Claims] 1. In an internal combustion engine, an intake port and an exhaust port are opened in a combustion chamber formed by recessing the lower surface of a cylinder head, and an electrode of an ignition plug screwed onto the cylinder head projects toward the inside of the combustion chamber. The circumferential contour of the combustion chamber relative to the lower surface of the cylinder head is inserted into the combustion chamber from the circumferential contour of the cylinder bore between the opening of the intake port and the opening of the exhaust port and near the electrode portion of the spark plug. A squeezing area for the top surface of the piston is formed outside the circumferential contour of the combustion chamber, while the top surface of the piston has areas near the opening of the intake port, near the opening of the exhaust port, and around the spark plug. A recess having a circumferential contour surrounding the electrode portion is provided, and a portion of the circumferential contour of the recess on the top surface of the piston that surrounds the vicinity of the electrode portion of the spark plug is defined as a portion of the circumferential contour of the combustion chamber that surrounds the electrode portion of the spark plug. It is configured to be located radially outside of the area surrounding the area,
In addition, the squish area in the vicinity of the electrode portion of the spark plug is replaced with a portion between the electrode portion of the spark plug and the opening of the intake port, and a portion between the electrode portion of the spark plug and the exhaust port. An internal combustion engine characterized in that the portion between the spark plug and the opening is large and the portion outside the electrode portion of the spark plug is small.