JPH0598966A - Squish structure for spark-ignition type 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 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, while a sub-ignition plug 27 is arranged inside the sub-chamber 19. 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 present invention, a combustion recess forming a combustion chamber is formed in a portion of a cylinder head which faces a cylinder block, and a main ignition plug is mounted in the combustion recess. In the spark ignition engine described above, a flat surface is formed on the peripheral edge of the combustion recess of the cylinder head, 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. Of the squish structure for generating a flow toward the combustion chamber of the cylinder head, the sub-chamber opening toward the peripheral edge of the upper surface of the piston is provided in the flat surface of the cylinder head, and the flat surface of the cylinder head is formed. Of the air-fuel mixture introduction passage for introducing the air-fuel mixture into the sub-chamber by communicating the sub-chamber with the main combustion chamber by means of the introduction escape portion formed on at least one of the surface and the peripheral portion of the upper surface of the piston. As well as, it is characterized in that arranged sub spark plug 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, the air-fuel mixture is introduced into the sub chamber through the air-fuel mixture introduction passage, and the introduced air-fuel mixture is ignited by the sub-ignition plug. 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. Further, in the invention of claim 2, 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 air-fuel mixture introducing passage communicating with the sub-chamber has a predetermined throttle shape only when the piston is located near the compression top dead center in the upward stroke of the piston, so that the throttle loss can be reduced, and the piston In the descending stroke, the passage area of the piston immediately increases as the piston descends, so that 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 view showing temporal changes in the mixture introduction passage and the mixture ejection passage, and FIG. 5 is a front view of the engine of this embodiment.

In the figure, reference numeral 1 denotes a device equipped with the device of this embodiment.
It is a cycle 4 valve engine, which has an oil pan 2 on the lower mating surface of the crankcase integrated cylinder block 2.
1 is attached, a two-part cylinder head 3 is stacked on the upper mating surface, fastened with head bolts, and a head cover 22 is covered on the upper mating surface of the cylinder head 3. 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 cross section, and a main ignition plug 16 is screwed into the center of the ridge of the combustion recess 3a. Further, the main spark plug 1 in the combustion recess 3a
Two intake valve openings 3b are formed on one side of the triangle 6, that is, one slope portion of the triangle, and two exhaust valve openings 3c are formed on the other slope portion.
c is led to the outer wall of the cylinder through intake and exhaust passages 7 and 8, respectively.

In this embodiment, the curvature of the exhaust passage 8 is made as small as possible in order to reduce the exhaust resistance, and the exhaust passage 8 is close to the exhaust lifter 13 described later. Therefore, there is a problem that the lubricating oil in that portion is overheated and deteriorates. To avoid this, a water cooling jacket 8a is provided between the exhaust passage 8 and the exhaust lifter 13 portion.
Is provided. Then, the water cooling jacket 8a and the water cooling jacket 8b on the upper side of the combustion chamber are provided as separate cooling water systems,
This prevents an abnormal rise in the temperature of the cooling water in the combustion chamber.

As shown in FIG. 5, an exhaust manifold 20 is connected to the connection opening of the exhaust passage 8 and an intake manifold 23 is connected to the connection opening of the intake passage 7. The intake manifold 23 has a straight pipe portion 23a whose axis is a straight line in the range of the region S1 and is bent so as to surround the head cover 22. A surge tank 25 is connected to the upstream end of the intake manifold 23 via an intake pipe 24. A mounting seat 23b is integrally formed on the straight pipe portion 23a of the intake manifold 23, and a resonance pipe 26 is connected to the mounting seat 23b. The mounting seat 23b joins the intake manifold 23 such that the axis S2 of the mounting seat 23b is tangential to the downstream side of the straight pipe portion 23a. Furthermore, the partition wall 23c at the upstream merging point of the mounting seat 23b and the intake manifold 23 is extended to the downstream side, thus suppressing the sudden expansion of the resonance tube 26 into the intake manifold 23, and rectifying the effect. Is getting The partition wall 23c is formed by integrally casting the region S3 and machining the connection hole.

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. 18 and the upper surface peripheral edge portion 4a form a squish region a in which the air-fuel mixture flows toward the combustion chamber, that is, squish is generated. 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 in the exhaust side squish surface 18 as a recess. 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. 1, 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 mixture introduction portion 19a serving as an introduction escape portion, and this mixture introduction portion 19a of the piston 4 located near the top dead center. An air-fuel mixture introduction passage A is configured with the upper surface. The air-fuel mixture introduction passage A is a passage for communicating the sub chamber 19 with the combustion chamber 6 and thereby introducing the air-fuel mixture into the sub chamber 19, and the main ignition plug 16 and the sub chamber 1
It is located on the line connecting 9 and 9 and in the immediate vicinity of the main spark plug 16.

A portion of the chamfered portion corresponding to the hypotenuse of the triangle is a flame jet portion 19b as a jet escape portion, and the flame jet 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 mixture introduction passage A and the flame ejection passage B have predetermined throttles only when the piston 4 rises to the vicinity of the top dead center, and the passage areas thereof decrease as the piston 4 descends. It becomes large and the passage resistance becomes almost zero.

A sub ignition plug 27 is provided in the sub chamber 19.
Are arranged. Electrode 27a of this auxiliary spark plug 27
Is inserted from the outer wall into the sub chamber 19 and is directed to the main spark plug 16 through the mixture introduction passage A.

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. Due to this pressure relationship, the air-fuel mixture is introduced into the sub chamber 19 through the air-fuel mixture introduction passage A even at the top dead center of the piston. Also, just before top dead center, the main spark plug 1
The air-fuel mixture in the combustion chamber 6 is ignited by 6 to start combustion. Then, a little later than this ignition, the auxiliary spark plug 27 ignites the air-fuel mixture in the auxiliary chamber 19. Then, a part of the flame generated in the sub chamber 19 is immediately ejected to the squish region a through the flame ejection passage B, whereby the piston 4 is located near the top dead center also in the squish region a. The combustion is started from, and as a result, the overall combustion time is shortened. Here, in the present embodiment, the exhaust side squish surface 18 is set large, but since the squish surface 18 is exposed to high temperature exhaust gas, the end gas becomes hot and knocking easily occurs. In this embodiment, a sub chamber 19 is provided on the squish surface 18, and
Since the auxiliary ignition plug 27 is provided to shorten the combustion time as described above, the combustion can be completed before knocking occurs. In addition, the flame introduction passage A has the piston 4
Is formed only in the vicinity of the top dead center, and is immediately released as the piston descends, so that the throttling loss and heat loss can be reduced.

FIGS. 6 and 7 are diagrams for explaining the second embodiment of the present invention, which is an example in which the sub chamber is provided on the intake side. In the figure, the same reference numerals as those in FIGS. 1 and 3 indicate the same or corresponding portions. In the present embodiment, the intake valve opening 3b and the exhaust valve opening 3c are offset to the exhaust side, the intake side squish surface 17 is set large, and the sub chamber 19 is provided in this portion. Further, in the sub chamber 19, the sub spark plug 2 is provided in the same manner as in the first embodiment.
7 are arranged. Also in the second embodiment, the same effect as that of 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 provided with the sub spark plug 27, the combustion time is shortened and combustion is completed before knocking occurs.

In the above embodiment, the air-fuel mixture introducing portion 19a and the flame ejecting portion 19b as the escape portion are formed on the cylinder head side, but the escape portion may be formed on the piston side, or the cylinder head, It may be formed on both of the pistons.

[0024]

As described above, according to the squish structure of the spark ignition engine according to the present invention, the sub chamber is formed so as to open toward the upper surface of the piston on the flat surface forming the squish region of the cylinder head, Since the air-fuel mixture introducing passage for communicating the air-fuel mixture is formed by communicating the sub-chamber with the combustion chamber, and the sub-ignition plug is arranged in the sub-chamber, the combustion start timing in the squish region due to the flame generated in the sub-chamber The effect is that the combustion time can be accelerated and the overall combustion time can be shortened. 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 the 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,
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 front view of the engine of the first embodiment.

FIG. 6 is a bottom view of the cylinder head of the engine according to the 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 Piston Top Edge 6 Combustion Chamber 16 Main Spark Plug 17,18 Intake Side, Exhaust Side Squish Surface (Flat Surface) 19 Subchamber 19a Mixture Introduction (Escape) Part) 19b Flame injection part (escape part) 27 Sub spark plug A Mixture 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 main ignition plug is mounted in the combustion concave portion, and the combustion of the cylinder head is performed. A flat surface is formed on the peripheral edge of the recess, 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, so that the flow of the air-fuel mixture into the combustion chamber is generated. In the squish structure, a sub-chamber opening toward the peripheral edge of the upper surface of the piston is provided in the flat surface of the cylinder head, and the sub-chamber is opened in at least one of the flat surface of the cylinder head and the peripheral edge of the upper surface of the piston. The introduction escape portion formed allows the sub chamber to communicate with the combustion chamber to form a mixture introduction passage for introducing the mixture into the sub chamber, and the sub ignition plug is arranged in the sub chamber. The squish structure of the spark ignition engine characterized by being installed. 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 engine, characterized in that it is formed by a jet escape portion formed on at least one of a flat surface and a peripheral portion of the upper surface.