JP2002089266A - Combustion chamber structure for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber structure for an internal combustion engine capable of improving suppression efficiency of knocking generation. SOLUTION: A whole periphery of a circular outer peripheral end surface 16 of a top surface of a piston is formed on a plane crossing with respect to a center axis of the piston at right angles, and a protuberant part protruding to the cylinder head direction is formed on the whole periphery of the end surface near the center. A pair of valve recesses 18 and 19 is formed respectively on the protuberant part. A plane inclined surface is formed on a top surface between the pair of the valve recesses. On the top surface near the respective valve recesses, a conical inclined surface connecting to the plane inclined surface and the circular outer peripheral end surface 16 is formed. A first squish area is formed with the plane inclined surface and the circular outer peripheral end surface 16. A second squish area is formed on the conical inclined surface. At least a part of a squish flow generated in the first squish area is introduced into the second squish area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a combustion chamber of a four-stroke cycle spark ignition type internal combustion engine.

[0002]

2. Description of the Related Art In a four-stroke cycle spark ignition type internal combustion engine having a pair of intake valves and a pair of exhaust valves, when a compression ratio is increased, a combustion chamber formed by a spark plug at the end of a compression stroke. Due to the high-pressure combustion gas that has started burning by the ignition of the air-fuel mixture, the air-fuel mixture at a location away from the spark plug is pressurized and heated to a high pressure and a high temperature, and knocking that easily ignites regardless of flame propagation is likely to occur.

In order to suppress the occurrence of knocking, the outer peripheral portion of the piston top surface constituting the lower surface of the combustion chamber forms an outer peripheral protruding portion gently inclined upward toward the center axis of the piston. The inner surface of the cylinder head that constitutes the upper surface is formed in a conical shape that is gently inclined upward from the outer periphery toward the center, and when the piston approaches the vicinity of top dead center, the upper and lower width is small at the outer periphery of the combustion chamber. Combustion chamber structure that generates a squish flow from the squish area to the center of the combustion chamber (Japanese Patent Publication No. Hei 8-30414)
was there.

However, the vicinity of the intake valve in the combustion chamber is cooled to a low temperature by the inflow of fresh air or air-fuel mixture, and the intake valve having a larger diameter than the exhaust valve makes it difficult to secure a sufficient squish area. In the air-fuel mixture near the intake valve at the end of the compression stroke, the flame propagation speed was lower at a lower temperature than the air-fuel mixture in other parts, and the knocking suppression effect was low.

[0005] In order to improve this, a notch which is a concave portion is formed near the intake valve on the outer peripheral portion of the piston top surface, and the squish flow generated in the squish area adjacent to the outer peripheral portion of the piston top surface is generated. A combustion chamber structure that flows into a notch and causes squish flows to collide with each other at the notch to generate turbulence, thereby promoting combustion near an intake valve (Japanese Patent Laid-Open No. 10-184366).
was there.

However, in an internal combustion engine provided with a pair of intake valves and a pair of exhaust valves, in order to maintain the filling efficiency at a high level, an outer peripheral edge of the combustion chamber and an outer peripheral portion of the intake valve farthest from the center of the combustion chamber. The width of the notch formed adjacent to the intake valve on the outer periphery of the piston top surface becomes extremely narrow in the cylinder radial direction, causing local overheating in the combustion chamber. However, the collision effect of the squish flow could be expected only by forming a partial notch in the combustion chamber.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an improvement in the structure of a combustion chamber of an internal combustion engine which overcomes such difficulties. The first aspect of the present invention relates to a cylinder head having a pair of intake valves. In the pent roof type combustion chamber structure provided with each exhaust valve, the entire circumference of the annular outer peripheral end face of the piston top surface is formed in a plane orthogonal to the piston center axis, and the entire end face near the center from the annular outer peripheral end face of the piston top surface is completely reduced. A bulge is formed around the circumference that protrudes toward the cylinder head,
A pair of valve recesses are formed in each of the protruding portions, and a flat inclined surface is formed on a top surface between the pair of valve recesses in each of the protruding portions, and a top surface near each valve recess in the protruding portion. Has a conical inclined surface that is smoothly connected to the planar inclined surface and is smoothly connected to the annular outer peripheral end surface of the piston top surface,
A first squish area is formed on the flat inclined surface and the annular outer peripheral end surface between the pair of valve recesses, and a second squish area is formed on the conical inclined surface,
At least a part of the squish flow generated in the first squish area is guided to the second squish area.

According to the first aspect of the present invention, since the piston rises to near the top dead center at the end of the compression stroke, the flat surface between the annular outer peripheral end surface of the piston top surface and the pair of valve recesses is formed. A first squish area is formed with the inclined surface, a squish flows from the first squish area toward the center of the combustion chamber, and an air-fuel mixture in the combustion chamber is significantly disturbed, and at least a part of the first squish area Squish flow is injected into the outer periphery of the combustion chamber between the intake and exhaust valves via the second squish area along the conical slope,
The collision of the squish flow injected from both the intake valve and the exhaust valve causes turbulence in the air-fuel mixture in the combustion chamber.

Since the first squish area and the second squish area constitute such a wide squish area, the combustion chamber can be made compact, the propagation distance of the ignition flame by the spark plug is shortened, and Since the flame ignited by the plug can rapidly reach the air-fuel mixture near the outer circumference of the combustion chamber, the flame is ignited by the flame before self-ignition, and the occurrence of knocking is significantly suppressed.

In addition, squish flows are respectively injected from the first squish area to the outer peripheral portion of the combustion chamber between the intake and exhaust valves via the second squish area, so that the squish flows collide with each other to cause knocking. In particular, since the air-fuel mixture in the vicinity of the valve recess is sufficiently disturbed, knocking can be more reliably suppressed.

Further, by configuring the present invention as described above, the squish area on the exhaust valve side is wider than the squish area on the intake valve side, so that the first squish area from the exhaust valve side can be changed to the second squish area. The squish flow injected between the intake and exhaust valves via the intake valve is stronger than the squish flow injected from the first squish area on the intake valve side through the second squish area between the intake and exhaust valves, and the collision point between the two is reduced. As a result of being located on the intake valve side, the air-fuel mixture near the intake valve, which tends to knock at low temperatures, is strongly agitated, combustion is promoted, and the effect of preventing knocking is further improved.

Further, according to the present invention, the flame ignited by the ignition plug at the center of the combustion chamber passes over the raised portion between the intake and exhaust valves having a low height and sucks the air around the outer periphery of the combustion chamber. Combustion is promoted by easily reaching the space between the exhaust valves and igniting the flame of the squish between the intake and exhaust valves that collided with each other, whereby self-ignition at the outer periphery of the combustion chamber is prevented.

Hereinafter, an embodiment of the present invention shown in FIGS. 1 to 7 will be described. The combustion chamber 1 of the four-stroke cycle spark ignition type internal combustion engine includes a cylinder block 2
The inner peripheral surface 4 of the cylinder sleeve 3 and the inner surface 6 of the cylinder head 5 integrally connected above the cylinder block 2
And a top surface 8 of a piston 7 slidably fitted on the inner peripheral surface 4 of the cylinder sleeve 3. As shown in FIG. 1, the inner surface 6 of the cylinder head 5 is 3 is formed in a pent roof shape that is gently inclined left and right upward with respect to a ridge line 9 passing near the central axis,
As shown in FIG. 3, a pair of intake openings 10 is provided along the ridge line 9 on one inclined surface, and a pair of exhaust openings 11 are similarly provided on the other inclined surface. In the head 5, an intake port 12 and an exhaust port 13 are formed to communicate with the intake opening 10 and the exhaust opening 11, respectively.

The cylinder head 5 includes
An intake valve 14 and an exhaust valve 15 capable of opening and closing the pair of intake openings 10 and the pair of exhaust openings 11 are fitted therein, and are provided with a valve operating mechanism such as a camshaft and a rocker arm connected to a crankshaft (not shown). The intake valve 14 and the exhaust valve 15 are opened and closed in conjunction with the elevation of the piston 7.

Further, an annular outer peripheral end surface 16 of the top surface 8 of the piston 7 has a plane which is perpendicular to the central axis of the piston 7 over the entire circumference, that is, a plane parallel to the mating surface of the cylinder block 2 and the cylinder head 5. And from the annular outer peripheral end face 16 of the top face 8 toward the center of the piston 7,
A protruding portion 17 protruding with a gentle curved surface in the direction of the cylinder head 5 is formed, and the protruding portion 17 has an intake valve 14 and an exhaust valve 15.
A pair of intake valve valve recesses 18 and exhaust valve valve recesses 19 are formed, respectively, and a recess 20 is formed at the center of the top surface 8 of the piston 7 by a raised portion 17.

In the protruding portion 17 formed on the top surface 8 of the piston 7, the protruding portion _17E between the pair of exhaust valve valve recesses 19 is more prominent than the protruding portion between the pair of intake valve valve recesses 18. part 17 _I highly formed than the intake valves valve recesses 1
8 ridges 17 _M between the exhaust valve valve recesses 19, the raised portion
17 _E is formed lower than _the raised portion 17 _I.

Further, in the top surface 8 of the piston 7, planar inclined surface 21 _I over the top ridges 17 _IT ridges 17 _I between the intake valve valve recesses 18 a pair of annular outer peripheral end surface 16 is formed together, the planar inclined surface 21 _E over the top ridges 17 _ET ridges 17 _E between the exhaust valve valve recesses 19 a pair of annular outer peripheral end face 16 is formed.

Further, on the top surface 8 of the piston 7, an annular outer peripheral end surface 16, an intake valve valve recess 18, and a flat inclined surface 21 are formed.
With _I and partially conically inclined surface 22 _I enclosed in is formed, the conical inclined surfaces 22 _E in a portion surrounded by an annular outer peripheral end face 16 and the exhaust valve valve recesses 19 and flat inclined surface 21 _E is formed, the intake valve and the annular outer peripheral edge surface 16 valve recesses 18, the inclined surface 23 is also formed in the circumferential portion surrounded by the exhaust valve valve recesses 19 and top ridges 17 _MT of the ridges 17 _M.

Further, an electrode portion 25 of a spark plug 24 is provided in the combustion chamber 1 near the center of the inner surface 6 of the cylinder head 5 so as to be exposed, and a fuel injection valve (not shown) is provided in the intake port 12. During the intake stroke, fuel is injected from the fuel injection valve, and at the end of the compression stroke, the electrode 25 of the spark plug 24
Sparks are to be blown away.

Moreover, the conical inclined surface 22 gradually increases in distance from the inner surface 6 of the cylinder head 5 from the planar inclined surface 21 to the inclined surface 23, so that the conical inclined surface 22 has a conical shape with respect to the inner surface 6 of the cylinder head 5. The space on the inclined surface 22 is formed widely,
The squish flow generated by the planar inclined surface 21 has directivity.

The valve recesses 18 and 19 are formed so that the surfaces of the intake and exhaust valves 14 and 15 and the valve recesses 18 and 19 facing the intake and exhaust valves 14 and 15 are parallel to each other.

Since the embodiment shown in FIGS. 1 to 7 is configured as described above, at the end of the compression stroke,
When the piston 7 approaches the top dead center, the annular outer peripheral end face 16 around the combustion chamber 1, the planar inclined surface 21 _I , and the planar inclined surface 21
_The space sandwiched between _E and the inner surface 6 of the cylinder head 5 opposed thereto becomes narrower as shown in FIG. 4, and the hollow arrow of FIG. As shown in FIG. 7, a squish flow is generated from this space, as shown by a dotted arrow in FIG.

At the same time, the outer peripheral end face 16 of the peripheral portion of the combustion chamber 1, the conical inclined surface 22 _I , the conical inclined surface 22 _E , and the inner surface 6 of the cylinder head 5 opposed thereto are sandwiched. The space also becomes narrow as shown in FIG. 3, and a squish flow like a one-dot chain line outlined arrow in FIG.
6, the circumferential inclined squish flow generated by being sandwiched between the planar inclined surface 21 _I , the planar inclined surface 21 _E and the inner surface 6 of the cylinder head 5 opposed thereto, merges with the annular outer peripheral end surface 16 and the intake valve valve recess 18. , flows into along the circumferential direction on the inclined surface 23 surrounded by the exhaust valve valve recesses 19 and top ridges 17 _MT of the ridges 17 _M. The circumferential squish flow flowing from the intake valve valve recess 18 along the inclined surface 23 and the circumferential squish flow flowing from the exhaust valve valve recess 19 along the inclined surface 23
Collision occurs at the center in the circumferential direction of The circumferential squish flow proceeds on the annular outer peripheral end face 16 without changing its direction to the center of the combustion chamber 1 due to the upwardly inclined surface 23, so that the turbulence due to the collision is severe.

Further, the conical inclined surface 22 is formed so that the space gradually increases from the planar inclined surface 21 to the inclined surface 23 with respect to the inner surface 6 of the cylinder head 5. In the squish flow generated in the above, the squish flow flowing in the circumferential direction has circumferential directivity, so that the collision is further strengthened.

As described above, in the illustrated embodiment, the squish flow is generated over the entire periphery of the combustion chamber 1 and the squish area is widened, so that the combustion area of the combustion chamber 1 is made compact, and ignition is performed. The propagation distance of the ignition flame by the plug 24 is shortened, and the flame ignited by the ignition plug 24 rapidly propagates to the air-fuel mixture at the peripheral portion of the combustion chamber 1, so that the flame is ignited by the flame before self-ignition. In addition, occurrence of knocking is suppressed. As a result, the compression ratio can be increased, and the improvement of fuel efficiency can be promoted.

By stopping one of the pair of intake valves 14, the swirl in the combustion chamber 1 during the intake stroke can be strengthened, and the synergistic effect of the reverse squish and the combination with the squish can be enhanced to improve the combustion. The mixture in the chamber 1 can be strongly disturbed. Similarly, the swirl may be generated by forming the intake port 12 in a spiral shape.

Further, since the top surface 8 of the piston 7 and the inner surface 6 of the cylinder head 5 are formed into smooth curved surfaces, the swirl flow in the combustion chamber obtained in the expansion stroke is not squished without being attenuated in the compression stroke. In combination, the air-fuel mixture in the combustion chamber 1 can be strongly disturbed, and the self-ignition due to local overheating in the combustion chamber 1 can also be suppressed.

Further, even in a region where there is no squish area between the inclined surface 23 on the top surface 8 of the piston 7 and a portion corresponding to this portion on the inner surface 6 of the cylinder head 5, FIG. A circumferential squish flow as shown by a dotted arrow in the outline is introduced, and in this region, the squish flows can collide with each other to generate a large turbulence, and the inner surface 6 of the cylinder head 5 and the top of the piston 7 can be generated. Since the annular outer peripheral end face 16 of the face 8 does not have an acute cross-sectional portion that causes self-ignition and attenuation of flame propagation, the effect of suppressing knocking can be significantly improved.

Further, in the raised portion 17 formed on the top surface 8 of the piston 7, the raised portion _17E between the pair of exhaust valve valve recesses 19 is replaced by the raised portion 17 between the pair of intake valve valve recesses 18. _Since it is formed higher than _I, the planar inclined surface 21 _{E at} the raised portion 17 _E between the pair of exhaust valve valve recesses 19 is formed.
In the squish area in contact, widely than the squish area in contact with the planar inclined surface 21 _I of the ridges 17 _I between a pair of intake valves valve recesses 18, the squish area in contact with the planar inclined surface 21 _E Uplifting squish flow of 17
_I can strongly lead to _I.

The surfaces of the intake and exhaust valves 14 and 15 and the surfaces of the valve recesses 18 and 19 facing the intake and exhaust valves 14 and 15 are made parallel to each other, particularly around the intake valve 14 at the piston top dead center (periphery).
The volume around the intake valve 14 due to the suction stroke and the lowering of the piston can be set low.
It is assumed that the intake from the intake port is easy to enter. Therefore, the volumetric efficiency in the intake air can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view illustrating a shape of an inner surface of a cylinder head in a combustion chamber structure according to the present invention.

FIG. 2 is a schematic perspective view illustrating a shape of a piston top surface of the combustion chamber structure illustrated in FIG. 1;

FIG. 3 is a longitudinal sectional view cut along the line III-III in FIG. 2 with the ignition plug removed.

FIG. 4 is a vertical sectional view cut along the line IV-IV in FIG. 2;

FIG. 5 is a longitudinal sectional view cut along the line VV of FIG. 2;

FIG. 6 is a plan view of the inner surface of the cylinder head and the top surface of the piston.

FIG. 7 is a plan view of a piston top surface.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... combustion chamber, 2 ... cylinder block, 3 ... cylinder sleeve, 4 ... inner peripheral surface, 5 ... cylinder head, 6 ... inner surface, 7
... piston, 8 ... top surface, 9 ... ridgeline, 10 ... intake opening, 11 ...
Exhaust opening, 12 ... intake port, 13 ... exhaust port, 14 ... intake valve, 15 ... exhaust valve, 16 ... annular outer peripheral end face, 17 ... ridge, 18 ...
Intake valve valve recess, 19 ... exhaust valve, 20 ... recess, 21 ... planar inclined surface, 22 ... conical inclined surface, 23 ... inclined surface, 24 ... spark plug, 25 ... electrode part.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 1/24 F02F 1/24 D 1/42 1/42 K 3/26 3/26 BC (72) Inventor Fumi Sato 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3G023 AA02 AA06 AB03 AC02 AD01 AD04 AD06 AD07 AD08 AD29 3G024 AA02 AA04 AA09 AA11 DA01 DA03 DA06 FA00 FA13

Claims (3)

[Claims] In a pent roof type combustion chamber structure provided with a pair of intake and exhaust valves in a cylinder head, the entire circumference of an annular outer peripheral end surface of a piston top surface is formed on a plane orthogonal to a piston central axis. A protruding portion protruding in the direction of the cylinder head is formed all around the end face near the center from the annular outer peripheral end face of the piston top face, and a pair of valve recesses is formed in each of the protruding portions. A flat inclined surface is formed on the top surface between the valve recesses, and the top surface near each valve recess in the raised portion is smoothly connected to the flat inclined surface, and an annular outer periphery of the piston top surface is formed. A conical inclined surface that is smoothly connected to the end surface is formed, and a first squish area is formed by the planar inclined surface and the annular outer peripheral end surface between the pair of valve recesses. And a second squish area is formed on the conical inclined surface,
A combustion chamber structure for an internal combustion engine, wherein at least a part of a squish flow generated in the first squish area is guided to the second squish area. 2. A combustion chamber structure for an internal combustion engine according to claim 1, wherein said exhaust-side squish area is formed wider than said intake-side squish area. 3. The combustion chamber structure of an internal combustion engine according to claim 1, wherein a height of a ridge between respective valve recesses in the intake valve and the exhaust valve is higher than a height of a ridge between the intake valve and the exhaust valve. A combustion chamber structure of an internal combustion engine characterized by being formed high.