JPS632577Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a combustion chamber structure of an engine.

Recently, in gasoline engines, in order to improve fuel efficiency without causing knocking, the cylinder head, which forms part of the combustion chamber, has been fitted with a
% or more and a combustion recess are provided,
The valve hole of one of the intake and exhaust valves is formed in the above-mentioned flat part, and the valve hole of the other valve is formed in the above-mentioned combustion recess, the ignition plug is made to face the combustion recess, and the top surface of the piston is formed in the above-mentioned flat part. A combustion chamber structure with a plane parallel to the plane part has been developed. This structure makes the combustion chamber more compact, highly compresses the air-fuel mixture in the combustion recess, and increases the combustion rate by the squish flow introduced into the combustion recess from the gap between the top surface of the piston and the flat surface at the end of the compression stroke. By increasing the speed, it is possible to achieve high compression while preventing abnormal combustion such as knocking.

Conventional engines with this type of structure were developed in Japanese Patent Application Laid-Open No. 1973-
As seen in Publication No. 91608, the combustion recess (partial combustion chamber in the publication) is formed with a circular cross section whose center line is parallel to the cylinder center line and whose bottom surface is parallel to the top surface of the piston. The valve hole for the intake valve was provided on the bottom, but this shape had the following drawbacks. That is, if the combustion recess is shaped like a circular hole with a constant cross section throughout,
When the valve installed in the valve hole in the bottom wall opens, the gap between the valve and the inner circumferential surface of the combustion recess becomes very narrow, and the intake air is restricted, resulting in a restriction loss that impairs output and fuel efficiency. Therefore, in the structure shown in the above publication, the middle part of the combustion recess is bulged out to avoid throttling loss, but this complicates the processing of the combustion recess and increases the cost. This prevents compaction. Further, in such a structure, since the wall thickness between the intake and exhaust ports becomes thin, it becomes difficult to provide cooling water passages around each port, and the cooling effect for each port is impaired. Furthermore, since the combustion recess is formed at right angles to the flat surface of the cylinder head, it is difficult for the squish flow to be smoothly introduced into the combustion recess.
When the squish flow enters the combustion recess, turbulence occurs, reducing combustion efficiency.

In addition, in order to further improve the combustibility in this type of combustion chamber structure, it is desirable to generate an intake swirl within the combustion chamber, but in the structure shown in the above publication, the intake air is opened at the bottom wall of the combustion recess. Since intake air flows in the cylinder axis direction (perpendicular to the cylinder head surface) through the valve hole, there remains the problem that it is difficult to generate an intake swirl.

In view of these circumstances, the present invention is intended to eliminate the drawbacks of the conventional structure in this type of engine.It facilitates the machining of the combustion recess while reducing the throttling loss of the valve installed in the valve hole of the combustion recess. In addition, it is possible to secure the necessary space between the intake and exhaust ports to install a cooling water passage close to the valve hole, thereby increasing the cooling effect, and also smoothing the squish flow into the combustion recess during the compression stroke. can be introduced into
Furthermore, the present invention provides a combustion chamber structure for an engine that enables generation of sufficient intake swirl, which has been difficult in the past, in this type of compact combustion chamber structure, and greatly increases combustion efficiency.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

In the figure, 1 is a cylinder block, 2 is a piston fitted into a cylinder hole 1a of the cylinder block 1, and 3 is a cylinder head. A combustion chamber is formed by the cylinder head portion facing the cylinder hole 1a. A cylinder head part forming a part of this combustion chamber is provided with a flat part 4 that occupies more than 50% of the area of the head part and a combustion recess part 5. A valve hole 7 of the exhaust valve 6 is formed in the flat part 4, and a valve hole 9 of the intake valve 8 is formed in the combustion recess 5, and each valve hole 7, 9 is connected to an exhaust port 7' and an intake port. 9', respectively.

The bottom wall 5a of the combustion recess 5 approaches the top surface of the piston 2 as it goes outward in the radial direction of the cylinder, and its extension intersects the cylinder head surface near the outer peripheral edge of the cylinder hole 1a. Meanwhile, the side wall 5b of the combustion recess 5 surrounding the bottom wall 5a is inclined with respect to the cylinder head surface so as to intersect the bottom wall 5a at an angle of 90° or more. That is, the combustion recess 5 is recessed upward most deeply at a predetermined position in the inner part of the cylinder with respect to the cylinder head surface along the flat part 4 at the lower end of the cylinder head, and extends from this position to the upper peripheral part of the cylinder hole 1a. The bottom wall 5a is formed by slanting so that the combustion recess 5 gradually becomes shallower up to a predetermined point, and the side wall 5b is raised from the flat part 4 at an obtuse angle and intersects with the bottom wall 5a at an angle of 90 degrees or more. Form it like this. In this way, the combustion recess 5 is formed in a substantially triangular shape when viewed in cross section as shown in FIG.

The formation range of the bottom wall 5a and side wall 5b of the combustion recess 5 and the angle of inclination thereof are determined so as to obtain a volume of the combustion recess 5 corresponding to the required compression ratio. In addition, in response to the fact that the bottom wall 5a of the combustion recess 5 is inclined as described above, the bottom wall 5a is
The angle of the downstream portion of the intake port 9' connected to the valve hole 9 opened to the cylinder head surface becomes smaller. In order to effectively utilize this point to generate a swirl inside the combustion chamber during intake, as shown in FIG. is offset from the center of the cylinder, and the bottom wall 5a is formed over a predetermined range in correspondence with this direction, and the valve hole 9 is provided in the bottom wall 5a at a position near the cylinder periphery.

A valve hole 9 provided in the bottom wall 5a of the combustion recess 5 is equipped with an intake valve 8 such that the valve shaft 8 is perpendicular to the bottom wall 5a. is equipped with an exhaust valve 6 such that the valve shaft 6a is perpendicular to the flat surface 4. Reference numerals 10 and 11 indicate valve seats mounted in the respective valve holes 8 and 9. Reference numeral 12 denotes an ignition plug, which is provided facing the combustion recess 5, preferably facing the mass center of the combustion recess 5.

A cooling water passage 13 is provided around the intake and exhaust ports 9' and 7'. In this case, since the side wall 5b of the combustion recess 5 is inclined so as to gradually move away from the exhaust port 7' as it rises from the flat part 4, the bridge portion between the intake and exhaust ports 9' and 7' is also It becomes possible to easily form the cooling water passage 13 close to each valve hole 9, 7.

Next, the effect of this combustion chamber structure during engine operation will be explained.

First, in the intake stroke, the intake valve 8 is operated and the valve hole 9 provided in the bottom wall 5a of the combustion recess 5 is activated.
is opened, and air-fuel mixture is sucked into the cylinder hole 1a from the intake port 9'. At this time, the bottom wall 5a is inclined, and the intake valve 8 moves diagonally inward of the cylinder hole 1a along a direction perpendicular to the bottom wall 5a. gradually separates from the surrounding wall. Therefore, the throttling loss between the intake valve 8 and the peripheral wall of the cylinder hole is small, the air-fuel mixture can smoothly flow into the cylinder hole 1a, and deterioration of filling efficiency is prevented. Furthermore, when the valve hole 9 of the intake valve 8 is provided in the bottom wall 5a of the combustion recess 5 in a state offset from the center of the cylinder,
Since the angle of the intake port 9' with respect to the cylinder head surface can be reduced by the slope of the bottom wall 5a, the swirl within the cylinder hole 1a due to the intake air flow is strengthened, contributing to improvement in combustion efficiency.

Also, in the compression stroke, when the piston 2 reaches the top dead center, the piston 2
The top surface 2a of the combustion chamber 2a and the plane portion 4 face each other with a fine gap, and the squish flow flows into the combustion recess 5 from this gap, and the air-fuel mixture is highly compressed in the combustion recess 5. Then, the mixture is ignited by the spark plug 12 and combusted. At this time, the side wall 5b of the combustion recess 5
Since the bottom wall 5a is inclined as described above, the squish flow is smoothly introduced into the combustion recess 5, turbulence is reduced, heat loss due to turbulence is reduced, and combustion efficiency is improved. Furthermore, if the ignition plug 12 is placed facing the mass center of the combustion recess 5, the fire quickly spreads throughout the combustion recess 5, which is more effective in improving combustion efficiency and preventing knocking.

As explained above, according to the combustion chamber structure of the engine of the present invention, the bottom wall of the combustion recess partially provided in the cylinder head portion approaches the top surface of the piston as it goes radially outward, and , inclined so that its extension line intersects the cylinder head surface near the outer periphery of the cylinder, while the side wall surrounding the bottom wall intersects the bottom wall at an angle of 90° or more with respect to the cylinder head surface. Since it is inclined, the combustion recess can be easily processed and formed compactly, and is also functionally superior, compared to conventional structures with combustion recesses of this type. In particular, it is possible to reduce throttling loss when the intake valve provided on the bottom wall of the combustion recess is opened, and to increase combustion efficiency by smoothly introducing the squish flow into the combustion recess during the compression stroke. ，
It is easy to provide cooling water passages to both exhaust ports, and cooling efficiency can be improved. Furthermore, by providing the valve hole of the intake valve in the bottom wall of the combustion recess which is inclined as described above, the direction of intake air flowing into the combustion chamber is inclined so as to approach the direction of the cylinder head surface, and the valve hole of the intake valve is Since the opening direction of the hole is offset from the center of the cylinder, the combustion chamber can be made more compact while also effectively generating an intake swirl, thereby further improving combustion performance.
In this way, various excellent effects can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part showing an embodiment of the combustion chamber structure of the present invention, and FIG. 2 is a bottom view of the cylinder head section taken from the - line in FIG. 1. DESCRIPTION OF SYMBOLS 1... Cylinder block, 1a... Cylinder hole, 3... Cylinder head, 4... Flat part, 5...
... Combustion recess, 5a... Combustion recess bottom wall, 5b... Combustion recess side wall, 7, 9... Valve hole, 12... Spark plug.

Claims (1)

[Scope of utility model registration request] In the cylinder head that forms part of the combustion chamber,
It has a flat part occupying 50% or more of the area of the head part and a combustion recess, a valve hole for an exhaust valve is formed in the flat part, a valve hole for an intake valve is formed in the bottom wall of the combustion recess, and the combustion recess is provided. In an engine in which the spark plug faces the recess and the top surface of the piston is a flat plane parallel to the flat surface, the bottom wall of the combustion recess approaches the top surface of the piston as it goes radially outward, and , is inclined so that its extension line intersects the cylinder head surface near the outer peripheral edge of the cylinder, while the side wall surrounding the bottom wall is inclined with respect to the cylinder head surface so that it intersects the bottom wall at an angle of 90° or more. A combustion chamber structure for an engine, wherein the opening direction of the valve hole of the intake valve is offset from the center of the cylinder, and the direction of movement of the intake valve is diagonally inward with respect to the cylinder axis.