JPH11200863A - Combustion chamber for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent diffusion of atomized fuel injected from an injector by changing a shape of a piston formed with partly a combustion chamber. SOLUTION: In a combustion chamber for an internal combustion engine formed by a cylinder head, cylinder block mounted in a lower surface of this cylinder head, and a top land 12 in a piston upper part slid in the cylinder block, in order to make a length to an intake side top land 12-1 of a piston 10 smaller than a length to an exhaust side top land 12-2, the top land 12 in the piston upper part is formed. In the combustion chamber of the internal combustion engine, a flat part is provided in an intake side of a piston upper surface, also in an exhaust side of the piston upper surface, and a rising part protruded in an upper direction at an angle of 70 deg. or more 90 deg. or less range relating to the flat part is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber of an internal combustion engine, and more particularly, to a combustion chamber of an internal combustion engine capable of preventing the diffusion of fuel spray injected from an injector by changing the shape of a piston forming a part of the combustion chamber. About the room.

[0002]

2. Description of the Related Art In an internal combustion engine, a combustion chamber is formed by a cylinder head, a cylinder block mounted on the lower surface of the cylinder head, and a top land on an upper part of a piston sliding in the cylinder block.

[0003] An ignition plug is disposed substantially at the upper center of the combustion chamber, and an injector pointing into the combustion chamber is provided.

The combustion chamber of the internal combustion engine is disclosed in
There is one disclosed in Japanese Patent Application Publication No. 100089. The combustion chamber of the internal combustion engine disclosed in this publication has a raised portion on the side of the top of the piston on the side of the intake passage so that a squish zone is formed between the piston and the lower surface of the cylinder head when the piston is at the top dead center position. And a combustion chamber of an internal combustion engine in which a space between a top surface of a side of the piston on the exhaust passage side and a bottom surface of the cylinder head is a combustion space, and a swirl generation passage is provided as an intake passage. At the same time, a notch is provided at least in the ridge of the top of the piston at the opening of the swirl-generating passage to realize a combustion chamber in which a strong swirl is generated, and good combustion is achieved by effectively utilizing the squish swirl. Is secured.

[0005] Another example is disclosed in Japanese Patent Application Laid-Open No. 5-240045. According to the first aspect of the present invention, a vortex generation type internal combustion engine disclosed in this publication includes a recess having a space between an intake port on the other side of a plane including a cylinder axis and a lower surface of a cylinder head; A protruding portion provided with a side wall portion which is provided adjacent to the lower surface of the cylinder head and is gently protruding from the recess at the side of the intake port of the cylinder, so that intake air from the intake port is parallel to a straight line perpendicular to the cylinder axis. It is generated as a vortex around it, improving the agitation of the air flow and improving the combustion stability, and responds to stricter fuel consumption regulations and exhaust gas regulations. According to the second aspect of the present invention, the concave portion having the downwardly convex curved surface is provided, and the downwardly convex curved surface enhances the vortex, thereby further improving the agitating property of the airflow.

[0006] Furthermore, there is one disclosed in JP-A-6-264747. The combustion chamber of the internal combustion engine disclosed in this publication has a pent roof type combustion chamber forming space having a pair of intake ports and a pair of exhaust ports formed in the cylinder head lower surface, and is formed between the intake ports on the lower surface of the cylinder head. A squish area for the upper surface of the piston is formed between the exhaust port and a region outside the space between the intake port and the exhaust port, and a mountain-shaped projection is provided on the piston upper surface to enter the combustion chamber forming space, and a central portion of the mountain-shaped projection is provided. To form a projection that enters the space between the pair of exhaust ports in the combustion chamber formation space continuously, without causing energy loss at ignition, and improving combustion without deteriorating starting characteristics resulting in misfiring during operation Is being planned.

[0007] Furthermore, there is a device disclosed in Japanese Utility Model Laid-Open No. 6-12724. The combustion chamber structure of the internal combustion engine disclosed in this publication provides a hollow cavity at the top of a piston and two ignition plugs in a cylinder head in an internal combustion engine that burns premixed air in a cylinder by spark ignition. While each tip is arranged so as to be radially separated from each other on one side of the cylinder and face the inside of the cavity, the plane shape of the cavity is shifted toward the center of the piston in the area radially away from the two spark plugs, and the diameter is reduced. It is formed in a fan shape that is narrow and widens toward the periphery of the piston in the opposite area,
The shape of the cavity promotes the burning speed in the region where the flame propagation distance is long.

[0008] Another example is disclosed in Japanese Utility Model Registration No. 2501603. The combustion chamber structure of a two-cycle diesel engine with a sub-chamber disclosed in this publication includes a supply valve and an exhaust valve on an inner wall surface of a cylinder head, and is formed between a peripheral portion of the supply valve located on the exhaust valve side and a valve seat. In the combustion chamber structure of a two-cycle diesel engine in which the opening to be formed is covered by a mask wall, a concave groove is formed on the inner wall surface of the cylinder head around the exhaust valve, and the exhaust valve is disposed in the concave groove. The depth of the groove is formed to be deeper than the maximum lift of the exhaust valve, a protruding part is formed on the piston top surface that can enter the groove, and the sub chamber injection hole is formed on the inner wall surface of the cylinder head excluding the groove. In addition to increasing the scavenging efficiency, a high compression ratio is secured.

[0009]

Recently, many internal combustion engines for directly injecting gasoline fuel into a combustion chamber have been proposed.

In many of the internal combustion engines as described above, fuel is injected into a concave portion provided on a top land, which is the top surface of a piston, during a compression stroke under a low load, and fuel is collected near a spark plug and mixed. By stratifying the gas, the engine as a whole is operated in a lean state, and the fuel efficiency is greatly improved.

However, it is difficult to collect fuel near the spark plug without diffusing it into the combustion chamber, and to prevent the vicinity of the spark plug from becoming unnecessarily rich. Therefore, improvement has been desired.

[0012]

SUMMARY OF THE INVENTION Accordingly, in order to eliminate the above-mentioned disadvantages, the present invention provides a cylinder head, a cylinder block mounted on the lower surface of the cylinder head, and a top of a piston sliding in the cylinder block. In the combustion chamber of the internal combustion engine formed by the land, the top land on the piston is formed so that the length of the piston to the top land on the intake side is smaller than the length to the top land on the exhaust side. And

[0013] In a combustion chamber of an internal combustion engine formed by a cylinder head, a cylinder block mounted on the lower surface of the cylinder head, and a top land on an upper part of the piston sliding in the cylinder block, an intake air on an upper surface of the piston is provided. And a flat portion is provided on the exhaust side of the upper surface of the piston.
It is characterized in that a protruding portion that protrudes upward at an angle in the range of 90 is provided.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION
The top land on the top of the piston is formed so that the length of the piston to the top land on the intake side is shorter than the length to the top land on the exhaust side, and a squish flow is generated. To prevent the diffusion of fuel spray.

In addition, a flat portion is provided on the intake side of the upper surface of the piston, and a raised portion is provided on the exhaust side of the upper surface of the piston so as to protrude upward at a predetermined angle to prevent the fuel spray from diffusing to the exhaust side. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

1 to 7 show an embodiment of the present invention. In FIG. 3, reference numeral 2 denotes an internal combustion engine, 4 denotes a cylinder block, and 6 denotes a cylinder head.

The cylinder block 4 of the internal combustion engine 2 includes:
Piston 10 slidably provided in cylinder bore 8
A combustion chamber 14 is formed by the upper part of the piston 10, that is, the top land 12 as the top, the lower surface 6 s of the cylinder head 6, and the inner surface of the cylinder bore 8 of the cylinder block 4.

In the cylinder head 6, a spark plug hole 16 is formed at an upper portion of the combustion chamber 14 and substantially at the center of the combustion chamber 12, and an ignition plug 18 is disposed in the spark plug hole 16. I do.

An injector 20 is provided on the cylinder head 6 for directly injecting fuel into the combustion chamber 14, and two first cylinders 6 for supplying intake air to the combustion chamber 14 as shown in FIG. , Second intake port 2
2-1 and 22-2, and two first and second exhaust ports 24-1 and 24-2 for discharging exhaust gas from the combustion chamber 14 are provided.

At this time, when the injector 20 is installed near the outer periphery on the intake valve side (not shown), the injector 20 has a predetermined angle θ1 with respect to a joint surface 6sf of a lower surface 6s of the cylinder head 6 described later, for example, 20 ≦ θ1 ≦ It is installed at an angle in the range of 40.

Further, the first and second intake ports 22-
1, 22-2 from the upper part of the cylinder head 6 to the combustion chamber 14
, The first and second intake ports 22-1,
22-2 generates a reverse tumble flow.

Reference numeral 26 denotes a hole for mounting the injector 20, 28 denotes a hole for a cylinder head bolt formed in the cylinder head 6, 30 denotes a communication hole for the water jacket, and 32 denotes a cylinder that forms the combustion chamber 14. The outer peripheral line on the head 6 side, 6sf is the lower surface 6 of the cylinder head 6.
The joint surface 8d with the cylinder block 4 located at the outer peripheral portion of s is the inner diameter of the cylinder bore 8 (substantially the same size as the outer diameter of the piston 10).

At this time, the top land 12 of the piston 10 is formed so that the length up to the intake side top land 12-1 is smaller than the length up to the exhaust side top land 12-2.

More specifically, the length of the piston 10 up to the intake-side top land 12-1 is defined as the length of the exhaust-side top land 1-1.
When the length is smaller than the length up to 2-2, as shown in FIG. 1, when the height position on the lower end side of the piston 10 is the same, the height H1 on the intake side top land of the piston 10 is exhausted. It is formed smaller than the side top land height H2. At this time, the center of the top land of the piston 10 is set to the same height as the intake side top land 12-1, and the exhaust side top land 12-2 is turned around.

Further, a flat portion 34 is provided on the intake side of the upper surface of the piston 10, and on the exhaust side of the upper surface of the piston 10, a predetermined angle θ 2, for example, in the range of 70 ≦ θ 2 ≦ 90 with respect to the flat portion 34. A protruding portion 36 is provided which protrudes upward while forming an undercut portion at an angle.

The raised portion 36 of the piston 10
Are raised from the flat portion 34, that is, the wall surface 36 that rises.
a, and an inclined surface 36b directed from the exhaust side top land 12-2 to the intake side in an obliquely upward direction, and generates a squish flow from the exhaust side toward the center of the combustion chamber 14.

The flat part 3 on the intake side of the upper surface of the piston 10
Numeral 4 is formed in a shape obtained by projecting a shell facing the exhaust side onto a plane. The periphery of the warhead is continuous with the raised portion 36, and the position of the warhead is highest and gradually decreases toward both sides of the shell. The warhead position is not an acute angle but an arc having a certain curvature.

Further, on the exhaust side of the upper surface of the piston 10, that is, on the inclined surface 36b of the raised portion 36, two concave portions corresponding to the opening positions of the first and second exhaust ports 24-1 and 24-2 are provided. Places 38-1 and 38-2 are formed.

Next, the operation will be described.

The fuel spray injected from the injector 20 during the compression stroke of the internal combustion engine is, as shown in FIG.
The piston 10 collides with the flat portion 34 on the intake side of the piston 10 and is carried toward the spark plug 18 while being assisted by the reverse tumble flow by the first and second intake ports 22-1 and 22-2.

At this time, the wall surface 36a of the protruding portion 36 protruding from the flat portion 34 is set at a predetermined angle θ2 in the range of 70 ≦ θ2 ≦ 90, so that the wall surface 36a becomes an acute angle as shown in FIG. Alternatively, the fuel spray rises vertically to prevent the fuel spray from diffusing to the exhaust side.

When the height of the lower end of the piston 10 is the same, the height H1 of the top land on the intake side of the piston 10 is smaller than the height H2 of the top land on the exhaust side. The substantial height of the wall surface 36a of the portion 36 becomes large, and the run-up section of the fuel spray toward the spark plug 18 becomes long, preventing diffusion of the fuel spray and without increasing the compression ratio more than necessary. Then, the exhaust side of the piston 10 is raised so that the combustion chamber 14
A squish flow toward the center of the squish is generated to prevent diffusion of the fuel spray.

At the same time, a squish flow from the side to the central portion of the combustion chamber 14 is also generated to prevent the fuel spray from diffusing.

Thus, the squish flow is formed by forming the length of the top land 12 of the piston 10 up to the top land 12-1 on the intake side smaller than the length of the top land 12-2 on the exhaust side. The squish flow can be generated effectively, and the diffusion of the fuel spray injected from the injector 20 can be prevented.

The length of the piston 10 up to the intake side top land 12-1 is defined as the exhaust side top land 12-2.
When the height is smaller than the length of the piston 10, the height H1 on the intake side top land of the piston 10 is smaller than the height H2 on the exhaust side when the height position on the lower end side of the piston 10 is the same. In this manner, the reverse tumble flow can be promoted, and the diffusion of the fuel spray injected from the injector 20 can be prevented.

Further, a flat portion 34 is provided on the upper surface of the piston 10 on the intake side, and on the exhaust side of the upper surface of the piston 10, a predetermined angle θ 2, for example, in the range of 70 ≦ θ 2 ≦ 90 with respect to the flat portion 34. By providing the raised portion 36 that is raised upward at an angle, the wall surface 36a rises at an acute angle or vertically, and it is possible to reliably prevent the fuel spray from diffusing to the exhaust side.

Further, the raised portion 36 of the piston 10
Are raised from the flat portion 34, that is, the wall surface 36 that rises.
a, and an inclined surface 36b that is directed obliquely upward from the exhaust side top land 12-2 to the intake side, and generates a squish flow from the exhaust side toward the center of the combustion chamber 14, thereby forming a wall surface of the raised portion 36. 36a secures a running section of fuel spray toward the spark plug 18 to prevent diffusion of fuel spray and improve the combustion state, which is practically advantageous.

Further, the flat portion 34 on the intake side on the upper surface of the piston 10 is formed into a shell shape directed to the exhaust side by the raised portion 36, so that the fuel spray injected from the injector 20 and the intake port 22-1, The reverse tumble flow from 22-2 is effectively concentrated and guided to the innermost part of the flat part 34, that is, the part below the spark plug 18, so that the diffusion of the fuel spray can be reliably prevented, and the combustion state in the combustion state can be prevented. It can contribute to improvement.

[0040]

As described above in detail, according to the present invention, the cylinder head is formed by the cylinder block mounted on the lower surface of the cylinder head, and the top land on the top of the piston sliding in the cylinder block. In the combustion chamber of the internal combustion engine, the top land on the piston was formed so that the length of the piston to the top land on the intake side was smaller than the length of the top land on the exhaust side.
The squish flow can be generated, the squish flow can be effectively utilized, and the diffusion of the fuel spray injected from the injector can be prevented.

In a combustion chamber of an internal combustion engine formed by a cylinder head, a cylinder block mounted on the lower surface of the cylinder head, and a top land on an upper part of the piston sliding in the cylinder block, an intake side of an upper surface of the piston is provided. In addition to the flat portion provided on the exhaust side of the piston upper surface, a raised portion that protrudes upward at an angle in the range of 70 ≦ predetermined angle ≦ 90 with respect to the flat portion is provided.
Since the wall surface rises at an acute angle or vertically, it is possible to reliably prevent the fuel spray from diffusing to the exhaust side.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a piston taken along line II-II of FIG. 2 showing an embodiment of the present invention.

FIG. 2 is an enlarged plan view of a piston.

FIG. 3 is a schematic sectional view of an internal combustion engine.

FIG. 4 is a schematic enlarged sectional view of a combustion chamber portion of the internal combustion engine.

FIG. 5 is an enlarged bottom view of the cylinder head.

FIG. 6 is an enlarged front view of a piston.

FIG. 7 is an enlarged cross-sectional view of the piston taken along the line V {-V} of FIG. 2;

[Explanation of symbols]

 Reference Signs List 2 Internal combustion engine 4 Cylinder block 6 Cylinder head 8 Cylinder bore 10 Piston 12 Top land 12-1 Intake side top land 12-2 Exhaust side top land 14 Combustion chamber 18 Ignition plug 20 Injector 22-1, 22-2 First, Second Intake ports 24-1 and 24-2 First and second exhaust ports H1 Intake side top land height H2 Exhaust side top land height 34 Flat portion 36 Raised portion 36a Wall surface 36b Inclined surface

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 3/26 F02F 3/26 A

Claims (5)

[Claims] In a combustion chamber of an internal combustion engine formed by a cylinder head, a cylinder block mounted on a lower surface of the cylinder head, and a top land on an upper portion of a piston sliding in the cylinder block, an intake side of the piston is provided. A combustion chamber for an internal combustion engine, wherein a top land above the piston is formed so that a length to a top land is smaller than a length to an exhaust side top land. 2. When the piston has a length to the intake side top land smaller than a length to the exhaust side top land, the height of the piston on the intake side top land is smaller than the height of the exhaust side top land. 2. The combustion chamber of an internal combustion engine according to claim 1, wherein the combustion chamber is formed small, the top land center is made the same height as the intake side top land, and the exhaust side top land is wrapped around. 3. A combustion chamber of an internal combustion engine formed by a cylinder head, a cylinder block mounted on a lower surface of the cylinder head, and a top land on an upper part of the piston that slides in the cylinder block. And a flat portion is provided on the exhaust side of the upper surface of the piston, and a protruding portion that protrudes upward at an angle in a range of 70 ≦ predetermined angle ≦ 90 with respect to the flat portion is provided. Engine combustion chamber. 4. A protruding portion of the piston has a wall surface protruding from a flat portion, and an inclined surface directed from a top land on an exhaust side to an intake side obliquely upward, and a squish from the exhaust side to the center of the combustion chamber. The combustion chamber of an internal combustion engine according to claim 3, which generates a flow. 5. A flat portion on the intake side of the upper surface of the piston,
The combustion chamber of an internal combustion engine according to claim 3, wherein the projecting portion is formed in a projectile shape directed toward the exhaust side by the protrusion.