JPS6017224A - Combustion chamber structure in engine - Google Patents

Abstract

PURPOSE:To speed up the burning rate and enhance combustion efficiency by making the slope of a wall surface forming a concave in one tangential direction of a cylinder head smaller than that in the other tangential direction. CONSTITUTION:A concaved part 4 is provided on a section of an inside wall of a cylinder head 2 facing the upper surface of a piston 3. Both a combustion chamber consisting of the concaved part 4 and a squish zone forming a narrow gap are formed. An intake port 7 and an exhaust port 12 are provided in the combustion chamber and in the squish zone 5, respectively. The slope of a wall surface 4a in one tangential direction of the inside surfaces of the cylinder head 2 is made smaller than that of a wall surface 4b in the other tangential direction. With this contrivance, owing to combined effect of squishing and swirling, fuel burning rate can be increased while combustion efficiency can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in the structure of a combustion chamber of an engine.

(Prior art) Conventionally, as a cycle engine, for example, the
As shown in Publication No. 1,6,207, a recess is provided in the cylinder head in a portion corresponding to the area surrounding the intake boat or the exhaust port and the spark plug, so that the cylinder head can be recessed when the piston is at the top dead center. It is known that a combustion chamber formed by the recess is formed between the inner wall surface and the upper surface of the piston, and a squish zone with a minute gap is formed adjacent to the recess.

In such engines, the substantial combustion chamber that is formed when the piston reaches compression top dead center is formed by a recess formed in the inner wall of the cylinder head, so the combustion chamber structure is compact and nearly spherical. As a result,
The flame propagation area is wider, the combustion speed is faster than that of a flat-shaped combustion chamber, and the flame propagation distance is shortened because it is close to a spherical shape, so it is very advantageous against /tsuking. , and set the ignition timing to the optimum value (M, B
, T) can be set close to 1.

However, due to its good knock resistance, the compression ratio has been increased to a level higher than that of conventional models.
Combustion performance is improved by performing lean combustion with a suitable air-fuel mixture. In addition, by creating turbulence in the combustion chamber near compression top dead center due to the formation of a squish zone,
Furthermore, it has various advantages such as increasing the flame propagation area and increasing the combustion rate.

However, in the engine with the above structure, the stronger the squish flow, the faster the combustion speed, but in order to make the squish flow stronger, it is necessary to secure a large squish zone. In order to enlarge the squish zone, the compression ratio must be too large (which is not possible, so the combustion chamber must have a volume above a certain level, which requires the combustion chamber to have an irregular shape, which poses problems in terms of workability. Therefore, there are requests to make the squish zone too thick and to increase the combustion speed.

(Object of the Invention) The present invention has been made in view of the above points, and by obtaining the swirl effect in addition to the effect of the squish bush, the squish zone is not made too large (therefore, the combustion chamber is not distorted). The object of the present invention is to provide a combustion chamber structure for an engine that increases the combustion rate and improves the combustion efficiency without changing the shape.

(Structure of the Invention) The present invention provides a partial recess in the inner wall of the cylinder head facing the upper surface of the piston, and the recess is provided between the inner wall surface of the cylinder and the upper surface of the piston when the piston is at the top dead center. In addition to forming a combustion chamber and a squish zone with a small gap, the combustion chamber is provided with an intake port that is opened and closed by an intake valve, and the squish zone is provided with an exhaust port that is opened and closed by an exhaust valve. This invention relates to improvements in the structure of engine combustion chambers.

In order to achieve the above-mentioned object, the present invention provides the above-mentioned engine, in which a wall surface on one side in the cylinder circumferential direction of the cylinder head inner wall forming the recessed portion is sloped to be smaller than the wall surface on the other side. The present invention is characterized in that the synergistic effect of squish and swirl increases the combustion rate and improves combustion efficiency. (Examples) Examples of the present invention will be described in detail below with reference to the drawings.

In the in-line G-cylinder engine with a high compression ratio (70 or more) shown in Figures 1 to 3 (1st, 2nd, 3rd and Z
Among the cylinders A, B, C, and D, only the first cylinder A is shown), 1 is the cylinder block, 2 is the cylinder head, 6 is the piston, and 4 is partially attached to the inner wall of the cylinder head 2 facing the upper surface of the piston 6. A combustion chamber consisting of the four parts 4 and a squish zone with a minute gap adjacent to the four parts 4 are formed in the recess provided between the inner wall surface of the cylinder head 2 and the upper surface of the piston 6 when the piston 6 is at the top dead center. 5 is formed. In order to make the combustion chamber compact and approximately spherical, a recess 6b is formed in the lower surface of the umbrella portion 6a of the intake valve 6.

The recessed portion 4 serving as the combustion chamber is such that a part of the inner wall of the cylinder head 2 near the intake port 7 that is opened and closed by the intake valve 6 protrudes toward the center of the cylinder. The inclination of the wall surface 4a on the side opposite to the intake port 7 in the circumferential direction with respect to the plane perpendicular to the cylinder axis is determined by the slope of the wall surface 4b on the other side and the wall surface 4d inside the cylinder.
It is made smaller than the outer wall surface 4e. (See contour lines in Figure 2), whereby the intake air introduced from the intake port 7 through the intake manifold 8 is introduced along the inclined surface (wall surface 4a) and rotates around the central axis of the cylinder. Configured to generate swirl. In addition, other wall surfaces 4b and 4d.

The wall surface 4a, which is formed as a gentler slope than the wall surface 4e and extends in the extending direction of the intake port 7, has its lower end portion on the piston 6 side, that is, the tip portion 4f, bent in the cylinder circumferential direction. It is possible to form a strong swirl that allows intake air to be introduced even more smoothly.

The intake port 7 and the recess 4 are arranged along an axis I1.1 perpendicular to the cylinder row in the first and second cylinders A and B.
The third and third cylinders C
, D are also formed symmetrically with respect to the axis 22 perpendicular to the cylinder row.

The intake manifold 8 includes seventh branch passages 10, 10 which are symmetrically branched into two passages from a common main intake passage 9 for all cylinders A, B, C, and D, as shown in detail in FIG.
A second branch passage 11.11.11.11 is symmetrically branched into two passages from the first branch passage 10.10, and the downstream end of each second branch passage 11, 11, 11.11 is connected to each cylinder. A.

It is connected to B, C, and D intake boats 7.7 and 7.7.

In this way, taking symmetry into account, the intake ports 7 and the recesses 4 (combustion chambers) are arranged, and the intake manifold 8 is formed. Intake passage 9, seventh and second branch passage 1
Regardless of the flow in 0.11), it is introduced into each combustion chamber under substantially the same conditions, so swirl is generated under approximately the same conditions in each cylinder A, B, C, and D. As a result, each cylinder A.

The strength of the swirl at Bvc, D (m) < concavity 4) is approximately equal.

In addition, the wall surface 4b has a portion 4c located below the umbrella portion 6a of the intake valve B at maximum lift, which has a gentler slope than the portion located above it (see Fig. 1). ), this is to prevent performance from deteriorating by suppressing swirl and ensuring an optimal swirl level.

Reference numeral 12 denotes an exhaust boat opened and closed by an exhaust valve 13, which opens into the squish zone 5. Reference numeral 14 denotes a spark plug, which is attached to a mounting hole 15 formed in the wall surface 4a (slanted surface) of the recess 4. The electrode portion 14a of this spark plug 14 is
It is located within the mounting hole 15 so that it does not act as resistance to swirl, and a certain amount of space is secured around it to improve ignitability.

Reference numeral 16 denotes a carburetor, which is interposed in the middle of the main intake passage 9. Reference numeral 17 denotes a camshaft, which is rotatably supported above the intake and exhaust valves 6 and 16 arranged alternately in the - row, and is constantly biased in the valve closing direction by springs 18 and 18. This controls the opening and closing of the first filter.

Separate oil chambers 19 and 20 are arranged along both sides of the camshaft 17 in a space surrounded by the upper surface of the cylinder head 2 and the head cover 21, and each communicates with an intake passage (not shown). .

In addition, in the above explanation, the recovery of the combustion chamber (recess 4) was only explained for the first cylinder A, but for the third cylinder C.
The same is true for the second and third cylinders B and D.
are virtually identical except for symmetry.

With the above configuration, during low-load operation, the intake air-fuel mixture introduced into the combustion chamber (recess 4) through the intake port 7 is swirled in the cylinder circumferential direction along the wall surface 4a (slanted surface). As a result, directionality is ensured, so the swirl of the intake air-fuel mixture is maintained until the point of ignition, thereby accelerating the combustion rate and improving combustion efficiency. Combustion chamber (
High compression can be achieved by forming the recess 4),
Combustion efficiency is further improved. In this case, each cylinder A
, B, C, and D, the swirl is approximately uniform in strength, so that substantially the same combustion performance can be obtained in each cylinder A, B, C, and D.

In addition, at the end of the compression stroke, the squish flow generated in the squish zone 5, which is a minute gap formed between the inner wall surface of the cylinder radiator 2 and the upper surface of the piston 3, is pushed toward the combustion chamber (recess 4). As a result, a vortex is actively formed in the air-fuel mixture in the combustion chamber to improve combustion efficiency.

On the other hand, under high load, the portion 4c of the intake valve 6 located below the umbrella portion 6a at the time of maximum lift has a gentler slope than the portion located above it, so that at the end of the intake stroke In this case, swirl is suppressed, intake resistance is lowered, charging efficiency is increased, and high output is obtained.

Although the above embodiment is an example applied to a carburetor type engine, it can be similarly applied to a fuel injection type engine.

(Effects of the Invention) Since the present invention is configured as described above, the synergistic effect of the squish effect and the swirl effect makes it possible to increase the combustion efficiency without making the squish zone too large. can be achieved.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and FIG. 1 is an explanatory diagram showing a combustion chamber of an engine according to the present invention, FIG. 2 is a sectional view taken along line nn in FIG. 1, and FIG. is I[l
FIG. 7, a sectional view taken along the line -l1l, is an explanatory diagram of the intake system.

Claims (1)

[Claims] (/1 Cylinder head inner wall facing the top surface of the piston l
A concave portion is provided in this portion to form a combustion chamber consisting of the four parts and a squish zone with a minute gap between the inner wall surface of the cylinder head and the upper surface of the piston when the piston is at the top dead center. In an engine that has an intake port that is opened and closed by an intake valve in the squish zone, and an exhaust port that is opened and closed by an exhaust valve in the squish zone, one of the inner walls of the cylinder head that forms the recess in the circumferential direction of the cylinder A combustion chamber structure for an engine, characterized in that one side wall has a smaller slope than the other side wall.