JPH077544Y2 - Engine combustion chamber structure - Google Patents

Description

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

(Prior Art) Conventionally, in an engine, there is a technique for improving combustibility by generating swirl in intake air (only air or a mixture of air and fuel) introduced into a combustion chamber to improve ignition performance. Widely known.

By the way, in recent years, especially in automobile engines, there is a tendency to employ a so-called multi-valve engine in which two or more intake valves are provided per cylinder to improve intake engine charging efficiency to improve engine output. Even in such a multi-valve engine, it has been attempted to improve the combustibility by the swirl as described above (for example, see Japanese Utility Model Application Laid-Open No. 53-106505) filed by the present applicant.

This known example has a first intake port 51 that is effective in the full load region of the engine and a second intake port 52 that is effective only in the high speed / high load operating region as shown in FIG. In the meantime, the peripheral wall surface 54 extending from the combustion chamber peripheral edge portion 55 toward the exhaust port 56 side and on the first intake port 51 side.
Is formed as a guide surface 54 extending in the cylinder axis direction, and in the low speed / low load operating region of the engine, the guide surface 54 of the projection 53 causes the first intake port 52 to move.
The swirl is generated by giving directionality to the intake air introduced into the combustion chamber from.

However, in this known example, particularly in the low speed / low load region of the engine where the combustibility deteriorates, although the swirl is effectively generated by the protrusion and a high level of combustibility is secured, the protrusion 53 If the amount of extension from the periphery of the combustion chamber to the center side becomes too large, conversely, it is introduced from both the first intake port 51 and the second intake port 52 during high-speed / high-load operation of the engine. There is a concern that the protrusion 53, particularly the guide surface 54 close to the first intake port 51 with respect to the intake air serves as intake resistance, and in some cases the intake charging efficiency is limited.

(Purpose of the Invention) The present invention is intended to solve the problems pointed out in the above-mentioned prior art, and in a multi-valve engine having two intake valves per cylinder, an improvement in combustibility due to the swirl effect and The purpose of this is to improve the intake charging efficiency in the high speed / high load operation region.

(Means for Achieving the Object) As a means for achieving the above object, the present invention provides a first chamber on one side of a combustion chamber formed between a piston upper surface and a cylinder head inner wall facing the piston upper surface. The first intake port opened and closed by the first intake valve and the second intake port opened and closed by the second intake valve are separated from each other in the direction substantially orthogonal to the intake direction, and are opened. The second intake port is provided with a control valve that is closed at least during low speed / low load of the engine and is opened during high speed / high load, while the other side of the combustion chamber is provided with the first intake port. In an engine in which an ignition plug is disposed at a position facing the second intake port, and an exhaust port opened / closed by an exhaust valve is opened at a position facing the second intake port, the spark plug is installed along the periphery of the combustion chamber. The peripheral edge of the combustion chamber is provided only between the second intake port and the exhaust port within the range from the first intake port to the second intake port via the spark plug and the exhaust port. , Projecting into the combustion chamber so as not to exceed a range surrounded by straight lines commonly contacting the outer peripheral edge of the second intake valve and the outer peripheral edge of the exhaust valve on the peripheral edge side of the combustion chamber A protrusion that forms a minute gap with the upper surface of the piston at the dead point is provided, and a portion of the protrusion that faces the second intake valve extends substantially parallel to the cylinder axis direction. In addition, the portion facing the exhaust valve is a second peripheral wall surface extending substantially parallel to the cylinder axis direction, and the facing distance between the first peripheral wall surface and the outer peripheral edge of the second intake valve is the second peripheral wall surface. Peripheral wall and outer peripheral edge of the exhaust valve And a wall surface shape of the first peripheral wall surface and the second peripheral wall surface that is a concave curved surface that is smoothly concave and curved toward the intersection of the two. Is.

(Operation and Effect of the Invention) With this configuration, the present invention has the following operation and effect.

In the low-speed / low-load operation region of the engine, the control valve closes the second intake port, so intake air is introduced into the combustion chamber only from the first intake port. The introduced intake air flows to the exhaust valve side through the spark plug side located at a position facing the first intake port, and the second peripheral wall surface of the protruding portion provided facing the outer peripheral edge of the exhaust valve. Is deflected and guided in the cylinder circumferential direction to form a swirl flow toward the second intake port side, and a swirl is formed in the combustion chamber. In this case, since the second peripheral wall portion of the projecting portion is largely separated from the exhaust valve outer peripheral edge, the swirl formed by the second peripheral wall portion flows near the peripheral edge of the cylinder bore, and the swirl larger than the entire combustion chamber. Will be generated.

On the other hand, the lower surface of the protrusion forms a squish zone with the upper surface of the piston.
Since the facing distance between the peripheral wall of the second intake valve and the outer peripheral edge of the second intake valve facing the peripheral wall is set to be smaller than the facing distance between the second peripheral wall and the outer peripheral edge of the exhaust valve facing the second peripheral wall,
A larger squish zone is formed on the second intake valve side than on the exhaust valve side, and a stronger squish flow is generated toward the second intake valve side.

Therefore, since the direction of the strong squish flow generated on the side of the second intake port and the direction of the swirl are in the same direction, the squish flow increases the momentum of the swirl and is stronger and larger than the entire combustion chamber. Swirl is generated, and the combustibility in the low-speed / low-load operation region is significantly improved.

In the high-speed / high-load operation region of the engine, the control valve is open and the second intake port is open, so intake air is simultaneously introduced into the combustion chamber from both the first intake port and the second intake port. It In this case, since the projecting portion is located outside the straight line connecting the outer peripheral edge of the second intake valve and the outer peripheral edge of the exhaust valve with respect to the center of the combustion chamber,
In the second intake port formed in the vicinity of the first peripheral wall surface of the projecting portion, intake of intake air is hardly obstructed by the first peripheral wall surface, and good intake air introduction is possible. This is realized, and as a result, the intake charging efficiency in the high-speed / high-load operation region is improved, and higher output is promoted.

Further, in this case, the intake air introduced from the first intake port is made into a swirl flow from the spark plug toward the second intake port side via the exhaust valve, while being introduced from the second intake port. The intake air is guided to the first peripheral wall surface of the protruding portion to form a swirl swirling in the opposite direction to the intake air from the first intake port side, and the two swirls having different directions are mutually By interfering and being appropriately damped, it is possible to reliably prevent such excessive swirl, despite the high-speed / high-load operation region where excessive swirl tends to occur due to the large intake amount. The occurrence of a situation in which the combustion pressure rapidly rises due to excessive swirl and engine vibration occurs is prevented.

(Embodiment) A preferred embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

First Embodiment FIGS. 1 and 2 show a main part of an automobile engine having a combustion chamber structure according to a first embodiment of the present invention, and are denoted by reference numerals in FIGS. 1 and 2. Reference numeral 1 is a cylinder block, 2 is a cylinder head, 3 is a piston fitted in the cylinder 1a of the cylinder block 1, and the piston 3
The lower surface of the cylinder head 2 as opposed to the top surface 3a of the cylinder
Combustion chamber 4 is provided between a substantially dish-shaped recess 10 (corresponding to the inner wall of the cylinder head in the scope of claims for utility model registration) provided in 2a.
Is configured.

The combustion chamber 4 has two intake ports communicating with the intake passage 5, that is, a first intake port 11 and a second intake port 12
An exhaust port 14 communicating with the exhaust passage 6 and an ignition plug hole 18 are opened. The first intake port 11 and the second intake port 12 are arranged at positions appropriately deviated from the center of the combustion chamber 4 to the outer peripheral side and in a state of being close to each other in a direction substantially orthogonal to the intake direction. The first intake valve 15 and the second intake valve 16 are provided respectively.

On the other hand, the exhaust port 14 is formed at a position facing the second intake port 12 across the center of the combustion chamber 4, and an exhaust valve 17 is attached to the exhaust port 14. . Further, the spark plug hole 18 is provided at a position facing the first intake port 11 so that the first intake port 11, the second intake port 12 and the exhaust port 14 form a substantially rectangular shape. . A spark plug 23 is screwed into the spark plug hole 18.

The intake passage 5 is formed by assembling a first intake passage 7 communicating with the first intake port 11 and a second intake passage 8 communicating with the second intake port 12 on the intake upstream side. The second intake passage 8 is provided with a control valve 25 that opens only in the high-speed / high-load operation region of the engine.

Further, in the peripheral edge 10a of the concave portion 10 of the cylinder head 2 (that is, the peripheral edge 4a of the combustion chamber 4) and the substantially triangular side space 22 surrounded by the second intake valve 16 and the exhaust valve 17, ,
As shown in FIG. 1 (hatched portion), FIG. 3 and FIG. 4, a substantially triangular protrusion 19 which is the gist of the present invention is integrated from the peripheral edge 10a of the recess 10 toward the center of the recess 10. Has been formed. The protrusion 19 is for forming a squish zone in the combustion chamber 4, and the lower surface 19a thereof is flush with the lower surface of the cylinder head 2, and when the piston 3 is near the top dead center, The top surface 3a is closely opposed to the top surface 3a.

Further, the shape of the protruding portion 19 is set as follows by applying the present invention. That is, as shown in FIG. 1, the shape of the wall surface is a first peripheral wall surface 20 formed of a concave curved surface (arc surface) along the outer periphery of the second intake valve 16 and the exhaust valve 17 as shown in FIG. And a second peripheral wall surface 21 formed of a concave curved surface (arc surface) that is relatively distant from the outer periphery of the first peripheral wall surface 20 as compared with the first peripheral wall surface 20. . Further, at this time, the protrusion 19 of the second intake valve 16 and the exhaust valve 17 are arranged so that the protrusion 19 does not cross a straight line which is in common on the protrusion 19 side. The size is set.

Further, the shapes of the first peripheral wall surface 20 and the second peripheral wall surface 21 of the protruding portion 19 in the cylinder axis direction are set as follows. That is, the first peripheral wall 20 is a fourth substantially parallel to the valve lift direction of the second intake valve 16 as shown in FIG. (Reference numeral L ₁₎ (code L ₂₎ vertical wall surface. In contrast, the second
As shown in FIG. 3, the peripheral wall surface 21 is a blunt wall surface (symbol L ₄ ) substantially parallel to the axial direction (symbol L ₃ ) of the cylinder 1a.

By configuring the protruding portion 19 as described above, a high level of combustibility and intake charge efficiency are realized as described below. That is, in the low-speed / low-load operating region of the engine, the control valve 25 is held closed, so the intake air is the first intake port.
Although it is introduced into the combustion chamber 4 only from the 11 side, in this case, the introduced intake air is planarly (in the plane orthogonal to the cylinder axis direction) surrounded by the second peripheral wall surface 21 of the projecting portion 19 to the cylinder peripheral surface. It is deflected and guided in the direction to form a swirling flow as shown by arrow S _A. Further, in this swirl, the squish flow generated by the lower surface 19a of the protruding portion 19 and the top surface 3a of the piston 3 and the flow thereof are in the same direction, and the swirl becomes stronger. Therefore, the ignitability of the air-fuel mixture is further improved, and a high level of combustibility is ensured even in the low speed / low load operation region where the combustibility is relatively deteriorated.

On the other hand, in the high-speed / high-load operation region of the engine, the control valve 25 is held open, and a large amount of intake air is introduced into the combustion chamber 4 from both the first intake port 11 and the second intake port 12. In that case, since the projecting portion 19 is located outside the straight line with respect to the center of the combustion chamber 4, the second portion formed close to the first peripheral wall surface 20 of the projecting portion 19 is formed.
Even in the intake port 12, the intake air intake is hardly obstructed by the first peripheral wall surface 20, and the intake resistance of the intake air of the engine as a whole is reduced as much as possible. Therefore, the intake charge efficiency is improved and the engine output is increased.

Further, in this case, the intake air introduced from the first intake port 11 is a swirl flow as shown by the arrow S _A , and the intake air introduced from the second intake port 12 is the first intake port of the protruding portion 19. Guided by the peripheral wall surface 20, as shown by the arrow S _B , a swirl flow is formed in the direction opposite to the intake air from the first intake port 11 side. Therefore, the two swirls having different directions interfere with each other and are appropriately damped, so that a relatively small swirl is formed in the combustion chamber 4. Therefore, although it is in a high-speed / high-load operation region where an excessive swirl is likely to occur, the excessive combustion of the swirl causes the combustion pressure to rise sharply and engine vibration to occur. Will be prevented.

Second Embodiment FIGS. 5 and 6 show an essential part of an engine having a combustion chamber structure according to a second embodiment of the present invention. This combustion chamber structure is different from the combustion chamber structure of the first embodiment only in the structure of the intake passage 5, and the other structure, that is, the structure on the engine side is the same as that of the first embodiment. Therefore, in this case, each member shown in FIG. 5 and FIG.
Duplicated description will be avoided by giving reference numerals to the respective members in the drawings and FIG. 2, and only the configuration of the intake passage 5 and the action and effect based thereon will be described.

The intake passage 5 in this embodiment is, as shown in FIGS. 5 and 6, a first intake passage 7 communicating with the first intake port 11 and a second intake passage communicating with the second intake port 12. 8
And a control valve 25 for simultaneously opening and closing the first intake passage 7 and the second intake passage 8 are provided on the upstream side of the first intake passage 7 side.
A third intake passage 9 is formed to connect the third intake port 13 opening near the first intake port 11 to the intake upstream side of the control valve 25. The control valve 25 is held closed only in the low speed / low load operating region of the engine and is held open in the other operating regions.

Therefore, in the low speed / low load operation range of the engine,
The intake air introduced through the third intake passage 9 is introduced into the combustion chamber 4 from the third intake port 13 through the first intake port 11 as shown by an arrow S _A , and the second portion of the protruding portion 19 is introduced. Peripheral wall 21
To be swirled by the third intake port 13 and introduced into the combustion chamber 4 through the second intake port 12 as shown by an arrow S _B , and the first circumference of the protruding portion 19 is changed. The wall 20 makes a swirl flow, but it is split into two. In this case, the amount of intake air introduced from the side of the second intake port 12 is smaller than the amount of intake air introduced from the side of the first intake port 11 and swirl occurs in the combustion chamber 4 in the direction of arrow S _A. (In this case, of course, the swirl has a stronger flow due to the squishing action of the protruding portion 19).

On the other hand, during high-speed / high-load operation of the engine, intake air (arrow S _A ) introduced into the combustion chamber 4 from the first intake port 11 and combustion from the second intake port 12 via the second intake passage 8 Two-way swirl is generated by the intake air (arrow S _C ) introduced into the chamber 4. Also in this case, the excessive swirl generation is prevented by the interfering action between the two swirls S _A and S _C having different flow directions, and a suitable combustibility is obtained.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part of an engine having a combustion chamber structure according to a first embodiment of the present invention, FIG. 2 is a vertical sectional view taken along line II-II of FIG. 1, and FIG. 3 is of FIG. III-III vertical sectional view, FIG. 4 is a vertical sectional view taken along the line IV-IV of FIG. 1, and FIG. 5 is a plan view of an essential part of an engine having a combustion chamber structure according to a second embodiment of the present invention. 6
5 is a vertical sectional view taken along the line VI-VI in FIG. 5, and FIG. 7 is a plan view showing a conventional combustion chamber structure. 1 ... Cylinder block 2 ... Cylinder head 3 ... Piston 4 ... Combustion chamber 5 ... Intake passage 6 ... Exhaust passage 7 ... First intake passage 8 ... Second intake passage 9 ... Third Intake passage 10 ...... Recessed portion (cylinder head inner wall) 11 ...... First intake port 12 ...... Second intake port 13 ...... Third intake port 14 ...... Exhaust port 15 ...... First intake valve 16 ...... Second intake valve 17 ...... Exhaust valve 18 ...... Ignition plug hole 19 ...... Projection 20 ...... First peripheral wall surface 21 ...... Second peripheral wall surface

Claims (1)

[Scope of utility model registration request] 1. A first intake port and a second intake port opened and closed by a first intake valve on one side of a combustion chamber formed between an upper surface of a piston and an inner wall of a cylinder head facing the upper surface of the piston. A second intake port that is opened and closed by a valve is spaced apart and opened in a direction substantially orthogonal to the intake direction, and the second intake port is closed at least when the engine is operating at low speed and low load. On the other hand, the control valve that opens at high speed and high load is arranged, while on the other side of the combustion chamber, the spark plug is arranged at a position facing the first intake port and the second intake air In an engine in which an exhaust port opened / closed by an exhaust valve is opened at a position facing the port, the first intake port is passed along the peripheral edge of the combustion chamber through the ignition plug and the exhaust port. The peripheral edge of the combustion chamber and the second intake port are provided only between the second intake port and the exhaust port within the range reaching the second intake port.
Of the intake valve and the outer peripheral edge of the exhaust valve are projected into the combustion chamber so as not to exceed a range surrounded by straight lines commonly contacting with the outer peripheral edge of the exhaust valve on the peripheral side of the combustion chamber, and the piston at the top dead center of the piston A protrusion that forms a minute gap with the upper surface is provided, and a portion of the protrusion that faces the second intake valve is a first peripheral wall surface that extends substantially parallel to the cylinder axis direction. The portion facing the exhaust valve is defined as a second peripheral wall surface extending substantially parallel to the cylinder axis direction, and the facing distance between the first peripheral wall surface and the outer peripheral edge of the second intake valve is defined as the second peripheral wall surface. It is set to be smaller than the facing distance to the outer peripheral edge of the exhaust valve, and the wall surface shapes of the first peripheral wall surface and the second peripheral wall surface are concave curved surfaces that are smoothly curved toward the intersections of the two. Engine combustion characterized by Room structure.