JP2001059422A - Structure of spark ignition type four-valve type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress knocking and an increase in unburned components by making a radial width dimension between valve recesses for both intake valves and valve recesses for both exhaust valves on a piston conical surface narrower than a radial width dimension between the valve recesses for both intake valves and between the valve recesses for both exhaust valves. SOLUTION: A radial width dimension W1 between valve recesses 11a, 11b for both intake valves and valve recesses 12a, 12b for both exhaust valves of a conical surface 9 in a piston 4 is made narrower than a width dimension W2 between the valve recesses 11a, 11b for both intake valves and between the valve recesses 12a, 12b for both exhaust valves. As a result, an entering dimension into an area of the conical surface 9 in each valve recess 11a, 11b, 12a, 12b becomes shallow. Flowing of squish flow generated in squish areas 10a, 10b, 10c, 10d into each valve recess 11a, 11b, 12a, 12b is avoided and staying of a thick mixture within each valve recess 11a, 11b, 12a, 12b is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a four-valve internal combustion engine having two intake valves and two exhaust valves among spark-ignition internal combustion engines.

[0002]

2. Description of the Related Art Japanese Utility Model Application Laid-Open No. 60-1024 as prior art.
No. 28 discloses a spark ignition type internal combustion engine in which the lower surface of a cylinder head fastened to the upper surface of a cylinder block is used to improve the combustion of the air-fuel mixture when both the intake valve and the exhaust valve are two. , A conical concave portion is formed, an ignition plug is disposed at the deepest portion at the center of the concave portion, two intake valves and two exhaust valves are disposed around the ignition plug, and the cylinder On the top surface of the piston reciprocating in the cylinder bore in the block, a combustion chamber is formed in a concave shape, and a conical surface having substantially the same conical angle as the conical concave portion of the cylinder head is formed so as to surround the periphery of the combustion chamber. And a squish area for generating a squish flow between the piston and a conical surface around the combustion chamber of the piston is formed in each of the portions between the four valves on the inner surface of the conical recess. It is proposed.

In this structure, at the top dead center of the piston, the conical surface surrounding the combustion chamber at the top surface is very close to the intake valve and the exhaust valve on the cylinder head side. Due to the timing shift that occurs when the cam shaft for the exhaust valve is driven and rotated by the timing belt,
Interference that the intake valve and the exhaust valve come into contact with the conical surface of the piston may occur.

Therefore, conventionally, the above-mentioned contact and interference are avoided by forming a valve recess in a portion corresponding to the intake valve and the exhaust valve in the conical surface of the piston.

[0005]

Conventionally, however, the width of the top surface of the piston in the radial direction on the conical surface surrounding the combustion chamber is determined by the squish flow for all the squish areas on the cylinder head side. As described above, since the width of the entire circumference is widened, the dimension of entry of each valve recess from the inner peripheral surface of the conical surface is increased. Air-fuel mixture is generated, which causes knocking and an increase in unburned components.

An object of the present invention is to provide a structure capable of solving this problem.

[0007]

SUMMARY OF THE INVENTION In order to achieve this technical object, the present invention relates to a method of forming a conical concave portion on a lower surface of a cylinder head fastened on an upper surface of a cylinder block, and a spark plug in the concave portion. And two intake valves and two exhaust valves are arranged around the ignition plug, while a combustion chamber is recessed on the top surface of a piston that reciprocates in a cylinder bore in the cylinder block. Forming a conical surface surrounding the periphery of the combustion chamber, and further forming a conical surface surrounding the periphery of the combustion chamber in the piston on each of the portions of the inner surface of the recess in the cylinder head between the four valves. A squish area for generating a squish flow is formed, and a valve recess is formed in a portion of the conical surface of the piston corresponding to the two intake valves and the two exhaust valves. In the internal combustion engine, the radial width of a portion of the conical surface of the piston between the valve recess for both intake valves and the valve recess for both exhaust valves is set to be between the valve recesses for both intake valves and The width between the two exhaust valve recesses should be smaller than the radial width dimension. "

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

In this figure, reference numeral 1 denotes a cylinder block having a cylinder bore 2, reference numeral 3 denotes a cylinder head fastened to the upper surface of the cylinder block 1, and a reciprocating cylinder is provided in the cylinder bore 2 of the cylinder block 1. A moving piston 4 is provided.

On the lower surface of the cylinder head 3, a conical concave portion 5 is formed. In the concave portion 5, an ignition plug 13 is provided at a deepest portion substantially at the center thereof, and a spark plug 13 is provided around the ignition plug 13. Two intake valves 6a, 6b and two exhaust valves 7a, 7b are provided.

On the other hand, on the top surface of the piston 4, a combustion chamber 8 is formed to be concave, and a conical surface 9 is formed so as to surround the entire circumference of the combustion chamber 8.

The inner surface of the recess 5 in the cylinder head 3 is located between the intake valves 6a, 6b and the exhaust valves 7a, 7b, and between the intake valves 6a, 6b and the exhaust valves 7a, 7b. Each of the sections between
A squish area 10 for generating a squish flow between the conical surface 9 surrounding the combustion chamber 8 and
a, 10b, 10c, and 10d are formed.

Further, valve recesses 11a and 11b corresponding to the intake valves 6a and 6b of the conical surface 9 of the piston 4 correspond to both exhaust valves 7a and 7b of the conical surface 9. The portions are recessed with valve recesses 12a, 12b for each.

The conical surface 9 of the piston 4
Of the conical surface 9, the radial width W1 of the portion between the two intake valve valve recesses 11a, 11b and the two exhaust valve valve recesses 12a, 12b is defined by the distance between the two intake valve valve recesses 11a, 11b. In addition, the width between the two exhaust valve recesses 12a and 12b is smaller than the radial width W2.

In this configuration, when the piston 4 reaches the top dead center at the end of the compression stroke in which the piston 4 moves upward, the conical surface 9 of the piston 4 and the squish areas 10a, 10b, 10c, and 10d of the cylinder head 3 are connected. A squish action occurs between the squish flows, and the squish flow is ejected from each of the squish areas 10a, 10b, 10c, 10d toward the spark plug 13 as indicated by arrows in FIG.

In this case, of the conical surface 9 of the piston 4, both intake valve valve recesses 11a, 11a are formed.
As shown by a two-dot chain line A in FIG. 3, a portion between the exhaust valve valve recesses 12a and 12b and between the intake valve valve recesses 11a and 11b and the exhaust valve valve recesses 12a in the conical surface 9 is shown in FIG. , 12b, the width of the conical surface 9 in each of the valve recesses 11a, 11b, 12a, 12b becomes deeper, and the deeper penetration is larger. Of each valve recess 11a, 11b, 12
a, 12b, each squish area 10
a, 10b, 10c, and 10d, a part of the squish flow flows simultaneously from both the left and right sides, so that the valve recesses 11a, 11b, 12a, 1
In 2b, a phenomenon occurs in which a rich air-fuel mixture is accumulated.

On the other hand, as described above, the valve recesses 11 for both intake valves in the conical surface 9 of the piston 4 are formed.
a, 11b and the valve recesses 12a, 12b for the exhaust valves, the radial width W1 in the conical surface 9
When the width W2 in the radial direction in the portion between the valve recesses 11a and 11b for the intake valves and the portion between the valve recesses 12a and 12b for the exhaust valves is smaller than the width W2 in the valve recesses 11a, 11b, 12a, 12b. Each of the squish areas 10a, 10b, 1
It is possible to reduce or eliminate a part of the squish flow generated in the squish areas 10c and 10d from flowing into the valve recesses 11a, 11b, 12a and 12b. Each of the squish areas 10a, 10b, 10c,
Since the squish flow generated in each of the valve recesses 11a, 11b, 12a, and 12b can be prevented from simultaneously flowing into the valve recesses 11a, 11b, 12a, and 12b from both the left and right sides, the squish flow is concentrated in the valve recesses 11a, 11b, 12a, and 12b. The accumulation of the air-fuel mixture can be greatly reduced.

[0018]

As described above, according to the present invention, the radial width of the conical surface of the piston between the valve recesses for both intake valves and the valve recesses for both exhaust valves is determined by adjusting the width of the conical surface of the piston for both intake valves. By making the width smaller in the radial direction between the valve recesses and the portion between the exhaust valve recesses, it is possible to greatly reduce the accumulation of a rich mixture in each of the valve recesses. This has the effect of reliably avoiding the occurrence of knocking and the increase in unburned components.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing an embodiment of the present invention and is a sectional view taken along line II of FIG. 2;

FIG. 2 is a bottom view taken along the line II-II of FIG.

FIG. 3 is a plan view taken along the line III-III of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder bore 3 Cylinder head 4 Piston 5 Depression 6a, 6b Intake valve 7a, 7b Exhaust valve 8 Combustion chamber 9 Conical surface 10a, 10b, 10c, 10d Squish area 11a, 11b, 12a, 12b Valve recess 13 Spark plug

Claims (1)

[Claims] 1. A conical concave portion is formed on a lower surface of a cylinder head fastened to an upper surface of a cylinder block, a spark plug is disposed in the concave portion, and two intake valves and two exhaust valves are provided. While being disposed around the ignition plug, the top surface of the piston that reciprocates in the cylinder bore in the cylinder block has a recessed combustion chamber and a conical surface surrounding the combustion chamber. Forming a squish area for generating a squish flow between the piston and the conical surface surrounding the combustion chamber of the piston in each of the portions between the four valves in the inner surface of the recess in the cylinder head; In an internal combustion engine, a valve recess is formed in a portion corresponding to both the intake valve and the both exhaust valve in a conical surface of a piston. The radial width of the portion between the two intake valve valve recesses and the two exhaust valve valve recesses, the radial width between the two intake valve valve recesses and the portion between the two exhaust valve valve recesses A structure of a spark ignition type four-valve internal combustion engine, characterized in that the width is smaller than the width.