JPS633130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine, and more particularly to a combustion chamber structure of an overhead valve type spark ignition internal combustion engine.

In spark-ignition internal combustion engines, the structure of the combustion chamber has a large effect on the combustion of the air-fuel mixture, and by modifying the structure of the combustion chamber, good combustion of the air-fuel mixture is achieved, resulting in improved output, fuel efficiency, It has been well known that engine performance such as quiet operation can be improved.
The important thing in modifying the combustion chamber shape is to shorten the flame propagation distance and to increase the flame propagation speed by generating strong air-fuel mixture turbulence in the combustion chamber in the latter half of the compression stroke. etc.

BACKGROUND OF THE INVENTION Conventionally, compressed vortices, or squishes, have been utilized in many internal combustion engines to increase the flame propagation velocity within the combustion chamber. Squeeze is a relatively narrow gap between the top of the piston and the lower surface of the cylinder head, which is mainly caused by the mixture existing in the squish area being pushed out into the main space of the combustion chamber near the end of the compression stroke. It is a vortex of gas in the radial direction of the cylinder bore, and its size and location are determined by the combustion chamber structure.

In an overhead valve type spark ignition internal combustion engine, there is a wedge-shaped combustion chamber recess on the lower surface of the cylinder head, that is, on the mounting surface to the cylinder block, as one of the combustion chambers that generates a squish of moderate strength. The so-called wedge-shaped combustion chamber is well known. In an internal combustion engine with a wedge-shaped combustion chamber, the combustion chamber recess in the cylinder head is It must be formed relatively deep. However, in the case of deeply formed combustion chamber recesses, the steep slopes of the combustion chamber recess become a shroud wall that surrounds the intake ports that open into the gentle slopes of the combustion chamber recess, resulting in poor intake efficiency due to the masking effect. A problem occurs.

In addition, in order to get the full effect of Skitsyu,
It is necessary for the main flow of the squish flow to reach the spark plug directly, and in order to reduce fluctuations in combustion from cycle to cycle and ensure stable engine operation, the direction and size of this squish flow must be controlled. It is necessary to stabilize it.

However, in an internal combustion engine having a wedge-type combustion chamber as described above, the top surface of the piston is generally flat, and the squish generation surface and other parts are on the same plane, so the squish flow is caused by the squishing flow at the top of the piston. In this case, the main flow of the squishing flow does not directly reach the spark plug, which is generally installed in the combustion chamber recess of the cylinder head, and the effect of squishing cannot be obtained sufficiently. There are many things.

Furthermore, among internal combustion engines having wedge-type combustion chambers, there are known ones having a piston recess on the top surface of the piston, and this is, for example,
This is shown in Publication No. 141504. In this type of internal combustion engine, it is possible to make the combustion chamber recess in the cylinder head shallower by the amount of the piston recess provided.
However, the squishy flow diffuses toward the piston recess, making it even more difficult for the squishy flow to reach the spark plug, increasing the instability factor.

The present invention can fully obtain the effects of the squish flow, increasing the flame propagation speed, reducing flame propagation fluctuations between cycles, and advancing the combustion timing of the air-fuel mixture in contact with the high-temperature wall near the exhaust valve. The object of the present invention is to provide an improved internal combustion engine that reduces torque fluctuations, dilutes the air-fuel mixture, reduces fuel consumption, improves knock margin, and increases compression ratio.

Such an object, according to the present invention, includes a cylinder block having a cylinder bore, a cylinder head attached to one end of the cylinder block to close one end of the cylinder bore, and a piston disposed in the cylinder bore, A wedge-shaped combustion chamber depression including a relatively gentle slope and a relatively steep slope is formed at a position corresponding to the cylinder bore on the mounting surface of the head to the cylinder block, and a wedge-shaped combustion chamber recess is formed on the top surface of the piston at a position corresponding to the cylinder bore. A recess is formed, and each of the cylinder head and the piston has a squish generating surface that extends in a direction perpendicular to the center line of the cylinder bore constituting the squish area on the side of the gentle slope of the combustion chamber recess and that is parallel to each other. has,
In an internal combustion engine in which a spark plug hole is opened in the steep slope of the recess of the combustion chamber, the entire gentle slope is configured as a stepless continuous surface, and the squish generation surface has an obtuse edge. an internal combustion engine, wherein the side circumferential wall of the piston recess is configured as a wall surface extending in a direction substantially perpendicular to the squish generation surface and extends along the obtuse edge. achieved by.

According to this configuration, since the piston recess is formed in the piston, the wedge-shaped combustion chamber recess of the cylinder head can be made shallow by an amount corresponding to the space volume of the piston recess, and the cylinder head and the recess can be made shallow. Due to the Coanda effect, the flow of the air-fuel mixture pushed into the main part of the combustion chamber from the squishing surface with the piston, that is, the squishy flow, flows along the gentle slope of the wedge-shaped combustion chamber recess, and as a result, the squishy flow The main flow directly and reliably reaches the spark plug installed in the plug hole opened on the steep slope of the recess in the combustion chamber. Therefore, the effect of squeezing can be sufficiently obtained, and the flame propagation speed can be increased and flame propagation fluctuations between cycles can be effectively reduced.

Furthermore, since the exhaust valve is provided on the gentle slope of the recess of the combustion chamber, and the squish flow flows along the lower surface of the exhaust valve, the temperature rise of the air-fuel mixture existing below the exhaust valve is suppressed. The combustion timing of the air-fuel mixture existing around this area is advanced,
These things prevent the occurrence of knocking.

The angle of the obtuse edge formed by the gentle slope of the combustion chamber recess and the squish generation surface of the cylinder head is preferably about 160 to 165 degrees in order to obtain the Coanda effect.

Preferably, the squish generation surface is not substantially provided on the side where the spark plug is disposed. This is because if a relatively large squish generation surface is formed on the side where the spark plug is located, the squish flow from the squish generation surface formed on the side where the spark plug is not installed and the spark plug will be This is because the squish flow from the squish generating surface on the side where it is provided collides with the squish flow, resulting in unstable flow and large fluctuations between cycles.Furthermore, when a reverse squish occurs, the flame does not move in the direction of propagation. This is because flame propagation is suppressed by expanding in the opposite direction as well.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing the main parts of one embodiment of the internal combustion engine according to the present invention, especially the second embodiment.
Fig. 2 is a cross-sectional view taken along the line of Fig. 1.
FIG. 2 is a bottom view of the cylinder head of the internal combustion engine shown in the figure; In the figure, 1 indicates a cylinder block, and this cylinder block 1 has a cylinder bore 2.
have. A gasket 3 is disposed on the upper surface of the cylinder block 1, and a cylinder head 4 is attached thereon to close the upper end of the cylinder bore 2.

The cylinder head 4 has a wedge-shaped combustion chamber located on the mounting surface of the cylinder block 1 and at a position corresponding to the cylinder bore 2 and offset to one side, that is, to the right in the figure, from a virtual plane containing the central axis of the cylinder bore 2. It has a depression 5. The combustion chamber recess 5 has a relatively gentle slope 5a on the left side in the figure.
Also, there is a relatively steep slope 5b on the right side in the figure.
have. An intake port 6 and an exhaust port 7 are opened on the gentle slope 5a, and these ports are opened and closed by an intake valve 8 and an exhaust valve 9, respectively.

The cylinder head 4 has a gentle slope 5a in the combustion chamber recess 5.
It has a flat squish generating surface 10 extending in a direction perpendicular to the center line of the cylinder bore 2 on the side thereof. The area of the squish generating surface 10 may be the area of a cross section of the cylinder bore 2 perpendicular to its central axis. It is sufficient that the squish generation surface 10 is provided only on the gentle slope 5a side of the combustion chamber recess 5.

The entire gentle slope 5a is configured as one stepless continuous surface, and is smoothly connected to the squish generation surface 10 with an obtuse edge. The angle of this obtuse edge is preferably as close to 180 degrees as possible to obtain a good Coanda effect, and may be approximately 160 to 165 degrees.

The cylinder head 4 also has a plug hole 11 that opens in the steeply sloped portion 5b of the combustion chamber recess 5. An ignition plug 12 is screwed into this plug hole 11, and its ignition portion 12' is located inside the combustion chamber recess 5. It is located in

A piston 13 is provided within the cylinder bore 2, and two compression rings 14, 15 and an oil ring 16 are attached to the outer periphery of the piston 13. Piston 13
A bathtub-shaped piston recess 17 is formed on the top surface of the piston with a portion of the top surface remaining. The piston recess 17, like the combustion chamber recess 5, is provided at a position offset to the right in the figure from a virtual plane containing the central axis of the cylinder bore 2, with respect to the relatively steep side peripheral wall 17a and the piston top surface. It is bathtub-shaped with a parallel flat bottom surface 17b whose periphery is substantially aligned with the periphery of the combustion chamber recess 5 in all its dimensions. That is, the combustion chamber depression 5
and the piston recess 17 have substantially the same planar shape and face each other. still,
The space volume of the piston recess 17 may be about 1/5 of the total space volume of the space volume of the combustion chamber recess 5 and the space volume of the piston recess 17.

The top surface of the piston 13 remaining on the gentle slope 5a side of the piston recess 17 faces the squish generating surface 10 of the cylinder head 4 and acts as a squish generating surface 18. 18 is a spark plug area 1 on the side opposite to the side where the spark plug 12 is provided.
9 has been determined. Side peripheral wall 1 of piston recess 17
7a extends in a direction substantially perpendicular to the squish generating surface 18, is cut off from the squish generating surface 18, and extends in alignment with the obtuse edge.

Next, the operation of the internal combustion engine having the above-described combustion chamber structure will be explained.

During the compression stroke of the internal combustion engine, when the piston 13 rises from the bottom dead center position toward the top dead center position, the air-fuel mixture in the combustion chamber is compressed accordingly. When the piston 13 rises to near the top dead center position, the gap in the squish area 19 between the squish generating surface 18 of the piston 13 and the squish generating surface 10 of the cylinder head 4 narrows, and the air-fuel mixture existing in this area It becomes more compressed than what is present in the part. As a result, the ski area 19
The air-fuel mixture therein is pushed out toward the main combustion chamber space formed by the combustion chamber recess 5 and piston recess 17. This movement of the mixture generates a flow of the mixture within the main combustion chamber space, that is, a squish flow. When this squish flow is ejected from the squish area 19, it is deflected to the side of the gentle slope 5 to flow along the gentle slope 5a due to the Coanda effect. The light reaches the firing section 12'.
This promotes ignition and combustion of the air-fuel mixture.

Furthermore, as described above, since the squish flow flows along the lower surface of the exhaust valve 9 when flowing along the gentle slope 5a of the combustion chamber recess 5, the air-fuel mixture existing below the exhaust valve 9 is sufficiently stirred. In addition, the temperature rise of this air-fuel mixture is suppressed, and the air-fuel mixture is heated to the spark plug 1.
The flame from 2 becomes easier to spread, and the occurrence of knotting is suppressed.

Since the squish area 19 is provided only on the side of the gentle slope 5a of the combustion chamber recess 5, the squish flow only occurs in one direction within the combustion chamber, so that the squish flows collide with each other within the combustion chamber. This stabilizes the flow behavior and reduces flame propagation fluctuations between cycles.

Although the present invention has been described above in detail with reference to specific embodiments, it is understood that the present invention is not limited to these and that various embodiments are possible within the scope of the present invention. This will be obvious to businesses.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of one embodiment of the internal combustion engine according to the present invention, especially the second embodiment.
Fig. 2 is a cross-sectional view taken along the line of Fig. 1.
FIG. 2 is a bottom view of the cylinder head of the internal combustion engine shown in the figure; 1...Cylinder block, 2...Cylinder bore, 3
... Gasket, 4... Cylinder head, 5... Combustion chamber recess, 5a... Gentle slope, 5b... Steep slope, 6... Intake port, 7... Exhaust port, 8... Intake valve, 9... Exhaust valve, 10... Squeeze generation surface, 11 ...Plug hole, 12...Spark plug, 12'...Ignition part, 13...
Piston, 14, 15... Compression ring, 16... Oil ring, 17... Piston recess,
18... Squeeze occurrence surface, 19... Squitch area.

Claims (1)

[Claims] 1. A cylinder block having a cylinder bore;
a cylinder head attached to one end of the cylinder block and closing one end of the cylinder bore;
a wedge-type combustion engine including a piston disposed in the cylinder bore, and a mounting surface of the cylinder head to the cylinder block including a relatively gentle slope and a relatively steep slope at a position corresponding to the cylinder bore. A chamber depression is formed,
A piston recess is formed in the top surface of the piston, and the cylinder head and the piston each extend in a direction perpendicular to a center line of a cylinder bore constituting a squish area on the side of the gentle slope of the combustion chamber recess. In an internal combustion engine which has squish generation surfaces that are parallel to each other, and in which a spark plug hole is opened on a steep slope of the recess of the combustion chamber,
The entire gentle slope is configured as a stepless continuous surface and is connected to the squish generation surface with an obtuse edge, and the side circumferential wall of the piston recess is substantially perpendicular to the squish generation surface. Internal combustion engine, characterized in that it is configured as a wall surface extending in the direction and extends along the obtuse edge. 2. In the internal combustion engine set forth in claim 1, it is provided that the angle of the obtuse edge formed by the gentle slope of the combustion chamber recess and the squish generation surface of the cylinder head is 160 to 165 degrees. Features an internal combustion engine. 3. In the internal combustion engine according to claim 1 or 2, the area of the squish generation surface is 1/5 to 1/3 of the area of the cross section of the cylinder bore perpendicular to its center line. An internal combustion engine characterized by: 4. In any of the internal combustion engines set forth in claims 1 to 3, the spatial volume of the piston recess is substantially equal to the spatial volume of the combustion chamber recess and the spatial volume of the piston recess. An internal combustion engine characterized in that the total space volume of the internal combustion engine is 1/5 or more of the total space volume of the engine.