JPH0598967A - Squish structure for spark-ignition engine - Google Patents

Abstract

PURPOSE:To provide a squish structure for a spark-ignition engine which can advance a combustion starting timing inside a squish area, and eliminate a throttle loss. CONSTITUTION:A squish area (a) is formed in a combustion recession 3a making a combustion chamber 6, in which area (a) air-fuel mixture is flowed in an inward direction of the combustion chamber by sandwiching the air-fuel mixture by means of a flat surface 18 of a cylinder head 3 provided with an ignition plug 16 and a circumferencial edge 4a of an upper surface of a piston 4 ascending toward a top dead center. A sub-chamber 19 which is opened toward the upper surface circumferential edge 4a of the piston 4 is formed on the flat surface 18 of the cylinder head 3. The sub-chamber 19 is communicated with the combustion chamber 6 by means of an introduction escape part 19a formed on the flat surface 18 of the cylinder head 3, and a flame introduction passage A is formed for introducing flame from the combustion chamber 6 into the sub-chamber 1. A flame jet passage for jetting the flame inside the sub-chamber 19 into the squish area (a) is formed by a jet escape part provided on the flat surface 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for generating squish in a spark ignition type engine having a spark plug in a combustion chamber, and more specifically, by advancing the timing of starting combustion in the squish region as a whole. The present invention relates to an improvement in the structure of the squish region part that can shorten the combustion time of the.

[0002]

2. Description of the Related Art In a spark ignition type engine, a flat surface is formed on a peripheral edge of a combustion recess formed on a surface of a cylinder head which faces a cylinder block, and the air-fuel mixture is formed between the flat surface and a peripheral edge of an upper surface of a piston. The squish structure that causes the mixture to flow toward the center of the combustion chamber in the vicinity of the compression top dead center, so-called squish, which causes turbulence in the mixture to improve combustibility Often adopted.

However, when the above-mentioned squish structure is adopted, although it is effective in that the air-fuel mixture is disturbed to improve the combustibility, the overall combustion time becomes long and the knock resistance is deteriorated. There is a problem. That is, since the squish region has a very narrow gap near the compression top dead center, it is difficult for the flame to enter the region, and the region is cooled to form a so-called quench zone. It will start only after descending to some extent. Therefore, the combustion time as a whole becomes long, which is disadvantageous in terms of knock resistance.

Therefore, as a squish structure which can be expected to solve the above problems, a cavity (sub-chamber) is provided in the cylinder head, and the sub-chamber is formed as described in, for example, Japanese Patent Laid-Open No. 60-60606. There is a structure that communicates with the combustion chamber through a small hole formed in the cylinder head. In this conventional structure, it is expected that the combustion start timing in the squish region is advanced by the jet flow of the flame due to the combustion of the air-fuel mixture introduced into the sub chamber in the compression stroke of the piston.

[0005]

However, in the above-mentioned conventional structure, since the sub chamber communicates with the combustion chamber through the small holes, the small holes are directed to the combustion chamber, and therefore the air-fuel mixture in the sub chamber is directed. The flame produced by combustion goes to the combustion chamber rather than to the squish region, and as a result, the effect of advancing the combustion start timing in the squish region is not so great. Further, in the case of this conventional structure, in order to strengthen the jet flow, it is necessary to reduce the cross-sectional area of the small holes. However, this increases resistance loss when introducing the air-fuel mixture into the auxiliary chamber and reduces There is also the problem that the heat loss due to

The present invention has been made in view of the above-mentioned conventional circumstances, and is capable of advancing the combustion start timing in the squish region and improving the resistance loss and throttle loss as well. It is intended to provide a structure.

[0007]

According to a first aspect of the invention of the present application, a combustion recess forming a combustion chamber is formed in a portion of a cylinder head which faces a cylinder block, and an ignition plug is mounted in the combustion recess. In a spark ignition type engine, a flat surface is formed on the periphery of the combustion recess of the cylinder head,
A squish structure for generating a flow of an air-fuel mixture toward a combustion chamber by sandwiching the air-fuel mixture between the flat surface and a peripheral portion of an upper surface of a piston that rises toward a top dead center, the cylinder head A sub-chamber opening toward the peripheral edge of the upper surface of the piston is provided in the flat surface of the cylinder, and the auxiliary escapement portion is formed on at least one of the flat surface of the cylinder head and the peripheral edge of the upper surface of the piston. It is characterized in that the chamber is communicated with the main combustion chamber to form a flame introduction passage for introducing the flame from the combustion chamber into the sub chamber. According to the invention of claim 2, when the piston is located at the top dead center, the flame ejection passage for ejecting the flame in the sub chamber is formed in the squish region composed of the flat surface and the peripheral edge of the upper surface. It is characterized in that it is formed by a jet escape portion formed on at least one of the peripheral portions of the upper surface.

[0008]

According to the squish structure of the present invention, since the flame introducing portion for connecting the sub chamber to the combustion chamber is formed, when ignition is initiated near the compression top dead center and combustion is started in the combustion chamber, Combustion flame is introduced into the sub-chamber through the flame introduction section, and the air-fuel mixture in the sub-chamber immediately burns. Further, in the inventions of claims 1 and 2, since the sub chamber is set to have a shape that opens toward the squish region, the flame generated in this sub chamber immediately enters the squish region, and as a result, even in the squish region. Combustion starts near the dead point, shortening the overall combustion time. Claim 2
In the invention of (1), since the flame injection passage for making the sub-type flame positively enter the squish region is provided, the combustion time is further shortened. Further, the flame introduction passage communicating with the sub chamber has a predetermined throttle shape only when the piston is positioned near the compression top dead center in the upward stroke of the piston, so the throttle loss can be reduced and the downward stroke of the piston can be reduced. Since the passage area of the piston immediately increases as the piston descends, the heat loss can be reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are views for explaining a squish structure of a spark ignition type four-cycle engine according to a first embodiment of the present invention, FIGS. 1 and 2 are sectional front views of the engine of the present embodiment, and FIG. FIG. 4 is a bottom view of the cylinder head, FIG. 4 is a diagram showing temporal changes in the flame introduction passage and the ejection passage, and FIG. 5 is a crank angle-combustion ratio characteristic diagram for explaining the effect of the present embodiment.

In the figure, reference numeral 1 denotes a device equipped with the device of this embodiment.
This is a cycle four-valve engine, which is a two-divided cylinder head 3 stacked on a crankcase-integrated cylinder block 2 and fastened with head bolts. Further, a head cover (not shown) is attached to the upper face of the cylinder head 3. It has a covered structure. A piston 4 slidably inserted into the cylinder bore 2a of the cylinder block 2 is connected to a crankshaft by a connecting rod 5. Here, the upper surface of the piston 4 has a shape in which the central portion is spherically recessed, and the peripheral edge portion 4a of the upper surface is a flat surface.

A combustion recess 3a forming a combustion chamber 6 is provided on the mating surface of the cylinder head 3 with the cylinder block 2. As shown in FIGS. 1 and 2, the combustion recess 3a has a substantially triangular shape in a cross section, and an ignition plug 16 is screwed into the center of the ridge of the combustion recess 3a. Two intake valve openings 3b are formed on one side of the ignition plug 16 of the combustion recess 3a, that is, one slope portion of the triangle, and two exhaust valve openings 3c are formed on the other slope portion. The openings 3b and 3c are led out to the outer wall of the cylinder through the intake and exhaust passages 7 and 8, respectively.

The intake valve opening 3b and the exhaust valve opening 3c are also provided.
The intake valve 9 and the exhaust valve 10 have valve heads 9 respectively.
a and 10a are arranged. The valve stems 9b and 10b of the valves 9 and 10 extend obliquely upward so as to form a predetermined included angle, and the valves 9 and 10 include the valve stem 9b.
A valve spring 11b interposed between a retainer 11a attached to the upper ends of b and 10b and a spring seat is biased in the closing direction. The intake camshaft 1 is attached to the lifters 12 and 13 attached to the upper ends of the valve stems 9b and 10b.
4. The cam nose of the exhaust camshaft 15 is rolling.

Further, the combustion recess 3 of the cylinder head 3
The portion of a that follows the slope of the triangle (the region shown by the diagonal lines in FIG. 3) is a flat surface that is continuous with the mating surface, and the portion that is located on the intake valve 9 side is the intake squish surface 17, the exhaust side. A portion located on the valve 10 side is an exhaust side squish surface 18. As the piston 4 rises to the top dead center, the squish surfaces 17 and 18 compress the air-fuel mixture at the peripheral edge of the combustion chamber so as to be sandwiched between the squish surface 17 and the peripheral edge portion 4a of the piston 4. The squish region a where the air-fuel mixture flows toward the inside of the combustion chamber, that is, the squish region a, is formed by 18 and the upper surface peripheral edge portion 4a. In the present embodiment, the exhaust side squish surface 18 is set larger than the intake side squish surface 17 by displacing the intake valve 9 and the exhaust valve 10 toward the intake passage 7 side.

In this embodiment, the sub chamber 19 is provided as a recess in the squish surface 18 on the exhaust side. The sub-chamber 19 is a recess that opens toward the upper peripheral portion 4a of the piston 4, and its height H1 is set to be larger than the height H2 of the combustion chamber 6. Further, as shown in FIG. 3, the sub-chamber 19 has a substantially triangular shape when viewed from the cylinder block 2 side, and a portion corresponding to the hypotenuse of the triangle is chamfered into a substantially arc shape over the entire length. The chamfered portion is the relief portion of the present invention.

A portion of the chamfered portion corresponding to the apex of the triangle is a flame introduction portion 19a as an introduction escape portion, and the flame introduction portion 19a is an upper surface of the piston 4 located near the top dead center. Constitutes the flame introduction passage A.
The flame introducing passage A communicates the sub chamber 19 with the combustion chamber 6 so that the flame generated in the combustion chamber 6 is transferred to the sub chamber 1
It is a passage for introducing into the fuel cell 9, and is located on the line connecting the spark plug 16 and the sub chamber 19 and in the immediate vicinity of the spark plug 16.

A portion of the chamfered portion corresponding to the oblique side of the triangle is a flame jetting portion 19b as a jet escape portion, and the flame jetting portion 19b is a peripheral edge of the upper surface of the piston 4 located near the top dead center. The flame ejection passage B is configured with the portion 4a. The flame ejection passage B is a passage for ejecting the flame generated in the sub chamber 19 to the squish region a formed by the exhaust side squish surface 18 and the upper peripheral portion 4a of the piston 4.

Here, the flame introduction passage A and the flame ejection passage B have predetermined throttles only when the piston 4 rises to near the top dead center, and the passage areas increase as the piston 4 descends. Therefore, the passage resistance becomes almost zero.

Next, the function and effect of this embodiment will be described. In the compression stroke, the air-fuel mixture in the combustion chamber 6 and the sub-chamber 19 is compressed as the piston 4 rises. In this case, since the sub-chamber 19 is set higher than the combustion chamber 6, The pressure in the chamber 19 is slightly lower than in the combustion chamber 6. Immediately before the top dead center, the ignition plug 16 ignites the air-fuel mixture and starts combustion. In this case, part of the flame generated in the combustion chamber 6 is introduced into the sub chamber 19 through the flame introduction passage A at the time when the piston 4 is located near the top dead center due to the above pressure relationship. The air-fuel mixture in the sub chamber 19 also immediately starts burning. Further, since the flame introducing passage A is located on the line connecting the spark plug 16 and the sub chamber 19 and in the immediate vicinity of the spark plug 16, the flame is immediately introduced into the sub chamber 19 also from this point. Then, a part of the flame generated in the sub chamber 19 is immediately ejected to the squish area a through the flame ejection passage B, whereby the squish area a.
Also in the above, combustion is started from the time when the piston 4 is located near the top dead center, and as a result, the overall combustion time is shortened. Here, in the present embodiment, the exhaust side squish surface 18
The squish surface 1
Since No. 8 is exposed to high-temperature exhaust gas, the end gas becomes hot and knocking is likely to occur. In this embodiment, the subchamber 19 is provided on the squish surface 18 to shorten the combustion time as described above, so that the combustion can be completed before knocking occurs. Further, the flame introduction passage A is formed only when the piston 4 is located near the top dead center and is immediately released when the piston descends, so that the throttling loss and heat loss can be reduced.

FIG. 5 shows experimental results for confirming the combustion time shortening effect of this embodiment. In the figure, C1 is a case where a normal sub chamber is not provided, and C2 is a case where a sub chamber is provided outside the squish region. This is a cavity provided in the cylinder head as described in the above-mentioned publication, for example. Is connected to the combustion chamber through a small hole. Further, C3 shows the characteristic when the sub chamber is provided in the squish region of this embodiment. In addition,
FIGS. 5 (a) and 5 (b) show the characteristics with and without the EGR gas introduced. As is clear from the figure, when comparing at the time of combustion ratio of 90%, for example, in the present embodiment, the crank angle is 5 to 3 degrees, and the auxiliary chamber is formed in comparison with the case where the auxiliary chamber is provided outside the squish region. Compared with the case of not having it, it has reached 7 to 4 degrees earlier, and has reached the combustion rate of 100% even earlier.

FIGS. 6 and 7 are views showing a second embodiment of the present invention, which is an example in which a sub chamber is provided on the intake side. In the figure,
1 and 3 indicate the same or corresponding parts. In the present embodiment, the intake-side squish surface 17 is set larger than the exhaust-side squish surface 18 by displacing the intake-valve opening 3b and the exhaust-valve opening 3c toward the exhaust side. Is forming. Also in the second embodiment, the same operational effect as the first embodiment can be obtained.
In this case, the intake-side squish surface 17 has a large temperature drop due to heat transfer, the flame propagation speed becomes slow, and as a result, the end gas easily satisfies the knocking occurrence condition. In the second embodiment, by providing the sub chamber 19, as described above,
The combustion time is shortened and combustion is completed before knocking occurs.

In the above embodiment, the flame introducing portion 19a and the flame ejecting portion 19b as the escape portion are formed on the cylinder head side. However, this escape portion may be provided on the piston side, or the cylinder head and the piston may be provided. You may provide in both.

[0022]

As described above, according to the squish structure of the spark ignition type engine of the present invention, the sub chamber is formed on the flat surface forming the squish region of the cylinder head so as to open toward the upper surface of the piston. Since the flame introducing passage that communicates the sub chamber with the combustion chamber and introduces the flame is formed, the combustion start timing in the squish region can be advanced by the flame generated in the sub chamber, and the overall combustion time can be shortened. effective. Further, since the flame introduction passage is composed of the flat surface of the cylinder head and the upper surface of the piston, the passage is formed only in the vicinity of the top dead center in the upward stroke of the piston, so that throttling loss can be reduced and in the downward stroke of the piston. The area of the passage is immediately expanded by the lowering of the piston, and there is an effect that heat loss due to the portion can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional front view of a sub chamber portion of a spark ignition type engine according to a first embodiment of the present invention.

FIG. 2 is a sectional front view of the valve portion of the engine of the first embodiment.

FIG. 3 is a bottom view of the cylinder head of the engine of the first embodiment.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a crank angle-combustion ratio characteristic diagram for explaining the effect of the first embodiment.

FIG. 6 is a bottom view of a cylinder head showing a second embodiment of the present invention.

FIG. 7 is a sectional front view of the sub chamber portion of the second embodiment engine.

[Explanation of symbols]

 1 Engine 2 Cylinder Block 3 Cylinder Head 3a Combustion Recess 4 Piston 4a Top Edge of Piston 6 Combustion Chamber 16 Spark Plug 17,18 Intake Side, Exhaust Side Squish Surface (Flat Surface) 19 Subchamber 19a Flame Introducing Section ) 19b Flame ejection part (ejection escape part) A Flame introduction passage B Flame ejection passage a Squish area

Claims (2)

[Claims] 1. A spark ignition engine in which a combustion concave portion forming a combustion chamber is formed in a portion of a cylinder head which faces a cylinder block, and a spark plug is mounted in the combustion concave portion. A squish in which a flat surface is formed on the peripheral edge, and the air-fuel mixture is sandwiched between the flat surface and the peripheral edge of the upper surface of the piston that rises toward the top dead center to generate a flow of the air-fuel mixture into the combustion chamber. A sub-chamber is formed in the flat surface of the cylinder head so as to open toward the peripheral portion of the upper surface of the piston, and is formed on at least one of the flat surface of the cylinder head and the peripheral portion of the upper surface of the piston. A spark introduction system characterized in that a flame introduction passage for introducing the flame from the combustion chamber into the sub chamber is formed by communicating the sub chamber with the combustion chamber by the introduced introduction escape portion. Engine squish structure. 2. The flame jet passage according to claim 1, wherein a flame jet passage for jetting a flame in the sub chamber is formed in a squish region formed by the flat surface and the peripheral portion of the upper surface when the piston is located at the top dead center. A squish structure for a spark ignition type engine formed by an injection escape portion formed on at least one of a flat surface and a peripheral portion of the upper surface.