JP2001041045A - Combustion chamber structure of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber structure of an engine of a spark ignition cylinder injection type to make fuel distribution and piston balance optimum. SOLUTION: A pent roof type ceiling surface in a cylinder is offset to the side of an exhaust valve, an injector 4 is arranged to inject from the side of an air intake valve in the cylinder, an ignition plug 5 is arranged roughly at a cylinder central position of a ceiling surface in the cylinder, a risen part 7 along a part of the pent roof type ceiling surface is formed on an upper surface of a piston 6, a bowl shape recessed part 11 is formed along an inclined upper surface 8 on the side of the air intake valve of the risen part 7 from the neighborhood of a cylinder central position on the risen part 7 and a diffused part 12 is continuously formed on the side of the air intake valve of the bowl shape recessed part 11. An injection distance of fuel increases, it easily becomes two layers of thick air-fuel mixture and thin mixture in a combustion chamber, and an igniting position becomes a cylinder center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION As a fuel injection structure for an automobile engine, there is an in-cylinder injection type in which an injector for injecting fuel is installed facing a combustion chamber, and a reverse tumble flow is generated in the combustion chamber. There is something. The present invention relates to a combustion chamber structure of such an engine.

[0002]

2. Description of the Related Art Among engines mounted on automobiles, there is an in-cylinder injection type having an injector for directly injecting fuel into a combustion chamber. For example, forming a recess on the top surface of the piston,
A structure in which fuel is injected toward the recess (Showa 5)
7-33231 and JP-A-4-94416) are known. Further, a structure in which a cylinder head ceiling surface is formed in a pent roof shape, an intake valve and an exhaust valve are disposed on each inclined surface to form a combustion chamber, and a spark plug is disposed near a top of the combustion chamber, and The pentroof-shaped protruding portion is formed on the piston upper surface, a concave portion is formed in the protruding portion over the intake valve-side slope formed in the protruding portion, and an injector is installed on the intake valve side, and the injected fuel is injected. A device configured to supply the liquid to the concave portion is known (Japanese Patent Application Laid-Open No. 10-1998).
61487, JP-A-9-79038).

The above-described in-cylinder injection type engine will be described with reference to FIG. The ceiling surface of the cylinder head 1 is formed such that the intake valve 2 side and the exhaust valve 3 side are inclined in a pent roof shape. The injector 4 is disposed on the intake valve 2 side. A spark plug 5 is provided at the top of the pent roof-shaped ceiling surface, and an intake valve 2 and an exhaust valve 3 are provided at each pent roof-shaped inclined surface position. The upper surface of the piston 6 is formed with a raised portion 7 that follows the pent roof shape of the cylinder head 1, has an intake valve side inclined upper surface 8 and an exhaust valve side inclined upper surface 9, and has an injector 4 The bowl-shaped recess 1 is formed on the intake valve-side inclined upper surface 8 so as to face the injection port 10.
1 is formed.

[0004] In the compression stroke shown in FIG.
The fuel is further injected toward the bowl-shaped recess 11 of the raised portion 7 of the piston 6, and the sprayed fuel is injected into the bowl-shaped recess 1 of the piston 6.
Captured at 1. The captured atomized fuel is collected near the ignition plug 5 with the rise of the piston 6, and becomes a rich mixture near the ignition plug 5 in the combustion chamber, and a leaner mixture is generated around the rich mixture to form a stratified mixture. A mixture is formed. The rich air-fuel mixture near the ignition plug 5 is burned by the spark discharge of the ignition plug 5, and the lean air-fuel mixture burns with the spread of the flame.

[0005]

However, in the operation of the above configuration, most of the sprayed fuel collects near the spark plug 5, the lean mixture in the peripheral portion becomes too thin, and the combustion of the rich mixture by the flame is performed. May become unstable and cause a fire. Further, in order to obtain a concentration at which the lean air-fuel mixture stably burns, it is necessary to increase the fuel injection amount. In this case, the air-fuel mixture near the ignition plug 5 becomes excessively rich, and soot may be generated. There is a risk of misfiring. As described above, during the compression stroke injection, the fuel is excessively concentrated in the vicinity of the ignition plug 5, and the ratio with the fuel distribution in the peripheral portion cannot be maintained properly. Further, since the bowl-shaped recess 11 is provided on the intake valve 2 side of the piston protrusion 7, the piston balance may be poor, causing slap noise or scuffing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a combustion chamber structure of a spark ignition cylinder injection engine in which the fuel distribution and piston balance in the combustion chamber are optimized.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a pentroof-shaped ceiling surface in a cylinder of a cylinder head having an injector is offset toward an exhaust valve. Formed on the upper surface of the piston, offset to the exhaust valve side, and formed a ridge along a part of the pent roof-shaped ceiling surface. A bowl-shaped recess is formed over the inclined upper surface.

According to a second aspect of the present invention, in the first aspect of the present invention, the injector is disposed so as to be injected from the intake valve side in the cylinder toward the bowl-shaped recess, and is located substantially at the center of the cylinder on the ceiling surface in the cylinder. A spark plug is provided.

[0009] The invention of claim 3 is claim 1 or claim 2.
In the invention, the diffusion portion is continuously formed on the intake valve side of the bowl-shaped concave portion.

[0010] The invention of claim 4 is claim 1 to claim 3.
The invention according to any one of the first to third aspects, characterized in that the top of the protruding portion of the piston is formed flat.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIGS. 1 to 3, in the spark ignition in-cylinder injection engine, a raised portion 7 is formed on the upper surface of the piston 6 along the pent roof-shaped ceiling portion of the cylinder head 1 so as to be offset toward the exhaust valve 3. The top is flattened (top surface 7a) to form an intake valve side inclined upper surface 8 and an exhaust valve side inclined upper surface 9. Due to the top surface 7a, a space having a substantially semicircular cross section is formed in the upper part of the combustion chamber, the explosive force of the mist fuel M pushes down the top surface 7a, and the force to the piston 6 is efficiently transmitted. Further, a bowl-shaped recess 11 is provided substantially at the center of the top surface 7a of the raised portion 7 of the piston 6,
A curved diffusion portion 12 is provided on the intake valve 2 side of the bowl-shaped recess 11 so as to be overlapped and connected. The atomized fuel M strikes the diffusion section 12 and diffuses throughout the combustion chamber.

The upper and outer sides of the combustion chamber are constituted by the ceiling surface of the cylinder head 1, the cylinder wall surface, and the inner surfaces of the intake valve 2 and the exhaust valve 3 arranged on the cylinder head 1. Is inserted to form a combustion chamber. The ceiling surface of the cylinder head 1 is formed so as to be offset toward the exhaust valve 3 by inclining the intake valve 2 side and the exhaust valve 3 side in a pent roof shape. The space between the intake valve side upper surface 8 and the exhaust valve side upper surface 9 of the portion 7 is narrowed by the cylinder head 1 side, so that a squish flow is generated (FIG. 2).
(See arrow in FIG. 3). An ignition plug 5 is provided at a position substantially at the center of the cylinder on the ceiling surface of the cylinder head 1, and the injector 4 is provided such that the injection port 10 of the injector 4 is located on the intake valve 2 side of the cylinder head 1. ing.

As shown in FIG. 4, the ceiling surface of the cylinder head 1 in the combustion chamber is inclined like a pent roof, and an intake valve 2 and an exhaust valve 3 are provided on each inclined surface. The intake valve 2 and the exhaust valve 3 are linked with the intake cam 13 and the exhaust cam 14,
The piston 6 slides inside the cylinder by the operation of the connecting rod 15. Further, when the injector 4 injects fuel toward the bowl-shaped recess 11 and the diffusion section 12 of the top surface 7a of the piston 6, a reverse tumble flow is generated along the curved surface of the bowl-shaped recess 11 as shown by an arrow.

As shown in FIG. 5, when the fuel is injected toward the bowl-shaped recess 11 and the diffusion section 12 in the compression stroke, most of the atomized fuel M is captured by the bowl-shaped recess 11, A part of the atomized fuel M hit by the air bounces off as shown by the arrow and is diffused into the space above the combustion chamber. Bowl-shaped recess 1
The atomized fuel M trapped in 1 generates a reverse tumble flow with the rise of the piston 6, and becomes a flow toward the vicinity of the ignition plug 5 as shown in FIG. This allows the ignition plug 5
A rich air-fuel mixture is generated in the vicinity, and the periphery of the rich air-fuel mixture is
2 is filled with the lean air-fuel mixture to form a layered air-fuel mixture.

As described above, the raised portion 7 is provided on the upper surface of the piston 6, and the bowl-shaped concave portion 11 and the diffusion portion 12 are continuously formed in the raised portion 7, so that the atomized fuel M injected from the injector 4 can be bowl-shaped. The rich mixture can be efficiently collected near the spark plug 5 by being trapped by the recess 11. The air-fuel mixture that has hit the diffusion unit 12 is diffused into the combustion chamber and is made into a lean air-fuel mixture, which is maintained at an appropriate concentration without becoming excessively lean.
And it becomes an ideal stratified mixture.

Further, the protrusion 7 is offset from the upper surface of the piston 6 on the exhaust valve 3 side, and the bowl-shaped recess 11 is formed near the center of the piston 6, so that the fuel injection distance becomes longer (the injection angle becomes larger). Also, the density of the atomized fuel M can be easily separated by the diffusion portion 12 and the rich mixture of the atomized fuel M is ignited by the ignition plug at the center of the cylinder. Since transmission is performed evenly and piston balance is improved, generation of slap noise and scuffing can be reduced. The intake port may be a top entry type or a side entry type, the number of valves (intake / exhaust valves) may be four, three or two, and the valve mechanism is D.
OHC or SOHC, or a direct hit type or rocker arm type may be used.

[0017]

The present invention is as described above. According to the first aspect of the present invention, the upper surface of the piston offset to the exhaust valve side is inclined from the vicinity of the cylinder center to the intake valve side inclined upper surface. , The atomized fuel from the injector can be sufficiently captured, and the explosive power of the fuel can be transmitted to the piston in a substantially balanced manner.
Also, since the injector can be separated from the main combustion chamber, the influence of heat can be minimized. According to the second aspect of the present invention, the injector is disposed so as to be injected from the intake valve side in the cylinder toward the bowl-shaped recess, and the spark plug is disposed at the cylinder center position on the ceiling surface in the cylinder. Since the atomized fuel can be sufficiently captured, and the ignition position is substantially at the center of the cylinder, the explosive power of the fuel can be transmitted to the piston in a substantially balanced manner. Claim 3
In the invention described in (1), the diffusion portion is formed continuously on the intake valve side of the bowl-shaped recess, so that a rich air-fuel mixture is concentrated in the bowl-shaped recess, and the mist fuel diffuses around and burns as a lean air-fuel mixture. The balance between the rich mixture and the lean mixture is improved in the chamber, and the combustion efficiency is improved. According to the fourth aspect of the present invention, since the top of the raised portion of the piston is formed flat, a combustion chamber is partially formed at the top, and the explosive force acting on the flat top acts on the piston descending, and the output of the engine is reduced. improves.

[Brief description of the drawings]

FIG. 1 is a sectional view of a piston according to an embodiment of the present invention.

FIG. 2 is a top view of the piston of FIG. 1;

FIG. 3 is a side view of the piston of FIG. 1;

FIG. 4 is a cross-sectional view of an intake valve and an exhaust valve of an engine combustion chamber provided with the piston of FIG. 1;

FIG. 5 is a sectional view showing a compression stroke of an engine combustion chamber provided with the piston of FIG. 1;

6 is a sectional view at the top dead center of an engine combustion chamber provided with the piston of FIG. 1;

FIG. 7 is a cross-sectional view showing a compression stroke of an engine combustion chamber provided with a conventional piston.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Intake valve 3 Exhaust valve 4 Injector 5 Ignition plug 6 Piston 7 Raised part 7a Top surface 11 Bowl-shaped concave part 12 Diffusion part

Claims (4)

[Claims] 1. A pentroof-shaped ceiling surface in a cylinder of a cylinder head having an injector is formed at a position offset to an exhaust valve side, and is offset to an exhaust valve side on an upper surface of a piston. A combustion chamber structure for an engine, wherein a raised portion is formed along a part of a ceiling surface, and a bowl-shaped recess is formed in the raised portion from near the center of the cylinder to an inclined upper surface on the intake valve side of the raised portion. . 2. The fuel injection system according to claim 1, wherein the injector is disposed so as to be injected from the intake valve side in the cylinder toward the bowl-shaped recess, and a spark plug is disposed substantially at the center of the cylinder on the ceiling surface in the cylinder. The engine combustion chamber structure according to claim 1. 3. The combustion chamber structure of an engine according to claim 1, wherein a diffusion portion is formed continuously on the intake valve side of the bowl-shaped recess. 4. A combustion chamber structure for an engine according to claim 1, wherein a top of the raised portion of the piston is formed flat.