JPH02149723A - Combustion chamber of engine - Google Patents

Abstract

PURPOSE:To make it possible to effectively stratify a dense fuel-air mixture around a spark plug by so forming the shape of the area in vicinity of the spark plug installation point on the peripheral surface of a dome-shaped combustion chamber that the inclination of the downstream side wall face is made greater than the upstream side wall face. CONSTITUTION:Fuel-air mixture is introduced toward the peripheral surface of the portion of a dome-shaped combustion chamber 5 near a spark plug 15. The area near the spark plug 15 installation point is so shaped that the inclination theta2 of its downstream side wall face is made greater than the inclination theta1 of its upstream side wall face. This constitutes a shape resisting part which temporarily stops the flow of fuel-air mixture by bending the flow of introduced fuel-air mixture in a specific direction. That is, the downstream side wall face part of a wedge-shaped recess 35 becomes the shape resisting part. It becomes possible, therefore, to efficiently stratify dense fuel-air mixture around the spark plug 15 to improve ignitability in particular.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to the structure of a combustion chamber of an engine.

(Prior art) For example, forming a swirl (induction turbulence) or squish (combination turbulence) in the air-fuel mixture in the engine combustion chamber in order to improve the combustion performance of the engine, or forming both the swirl and the squish. Combinations and the like have been well known for a long time.

Conventionally, as a means for forming the swirl, for example, as shown in Japanese Unexamined Patent Publication No. 61-16224, in addition to the usual main port in the intake boat section into the engine combustion chamber, in the circumferential direction of the engine combustion chamber, For example, in a low engine load region where the intake flow velocity is low and combustion performance is poor, the swirl port forms a swirl and the air-fuel mixture is introduced into the engine combustion chamber. In addition to increasing the flow velocity, the mixing performance of fuel and air is improved by changing the intake swirl in the engine combustion chamber from the direction of the outer circumference of the cylinder to the direction of the spark plug, improving flame propagation speed and improving engine combustion. There is a combustion chamber structure for an engine that is designed to stratify the air-fuel mixture near the ignition plug in the room to particularly improve ignition performance and combustion performance.

(Problem to be Solved by the Invention) However, according to the configuration of the above-mentioned prior art, the misfire phenomenon itself, which is caused by the fuel carried in the swirl effectively by timed injection directly colliding with the spark plug, is eliminated. However, the rich air-fuel mixture that was properly carried near the spark plug by the swirl would be scattered due to the sharp collision with the wall in front of the spark plug, and the rich mixture would be scattered near the spark plug. It is difficult to stratify a rich mixture. Therefore, it is not possible to expect the desired effect of improving ignitability.

Furthermore, since the ignition area itself is surrounded by a wall, the scavenging effect is low, and residual gas tends to remain, so there is a concern that the combustion performance may deteriorate.

(Means for Solving the Problems) The present invention has been made with the aim of solving the above-mentioned problems, and includes forming a dome-shaped combustion chamber portion of a predetermined size on the lower surface of the cylinder head. In an engine having a spark plug facing from the upper part of the cylinder head at a predetermined position offset laterally in the chamber, the air-fuel mixture is introduced toward the circumferential surface of the dome-shaped combustion chamber adjacent to the spark plug. At the same time, the angle of inclination of the wall surface near the spark plug installation part on the peripheral surface of the dome-shaped combustion chamber is made larger on the downstream side than on the upstream side, thereby bending the flow of the introduced air-fuel mixture in a predetermined direction. It is characterized in that it is configured as a shaped resistance portion that temporarily retains the flow of the air-fuel mixture.

(Function) In the combustion chamber structure of the engine of the present invention, a dome-shaped combustion chamber portion of a predetermined size is formed on the lower surface of the cylinder head, and a dome-shaped combustion chamber portion of a predetermined size is formed in the upper portion of the cylinder head at a predetermined position offset laterally within the dome-shaped combustion chamber portion. In an engine combustion chamber structure in which a spark plug faces from the side, the air-fuel mixture is introduced toward the circumference of the dome-shaped combustion chamber adjacent to the spark plug, and the air-fuel mixture is introduced toward the circumference of the dome-shaped combustion chamber. The flow of the air-fuel mixture is changed by changing the shape of the vicinity of the spark plug installation part on the surface so that the inclination angle of the downstream wall surface is larger than that of the upstream wall surface, thereby bending the flow of the introduced air-fuel mixture in a predetermined direction. The shaped resistance part is configured to temporarily retain the water.

Therefore, the mixed air flow introduced from the intake boat portion flows in a substantially swirling state along the circumferential surface of the dome-shaped combustion chamber portion, and is efficiently carried to the vicinity of the spark plug. In the spark plug part, the circumferential surface of the dome-shaped combustion chamber serves as a shaped resistance part that bends the flow of the air mixture in a predetermined direction, thereby creating a gentle shape that temporarily causes it to stagnate. Therefore, due to this action, the air mixture flow in the substantially swirl state is temporarily retained near the spark plug without being disturbed, making the area particularly around the spark plug rich.

Moreover, at the same time, the fuel carried along with the air mixture collides with the wall surface serving as the shaped resistance part due to centrifugal force, and is appropriately scattered near the spark plug. As a result, the above retention effect is further improved.

Therefore, when timed-injection is combined with the above configuration, the air-fuel mixture can be stratified more effectively.

(Effects of the Invention) Therefore, according to the combustion chamber structure of the engine of the present invention,
It becomes possible to efficiently stratify a rich air-fuel mixture around the ignition plug, and in particular, it becomes possible to improve ignition performance.

(Example) FIGS. 1 to 4 show the combustion chamber structure of an engine according to an example of the present invention.

First, Figure 1 shows the longitudinal cross-sectional structure of the combustion chamber of the engine.
In the drawing, reference numeral 1a denotes a cylinder block, and lb denotes a cylinder head located at the upper part of the cylinder block 1a, which is integrally provided through a gasket 2 and constitutes a predetermined engine cylinder together with the cylinder block 1a. A cylinder bore 3 having a predetermined diameter and a predetermined length is formed inside the cylinder block Ia (in order to simplify the explanation, water jackets and the like are omitted in the figure).

Further, the surface of the lower surface of the norinda head lb that corresponds to the cylinder bore 3 is a first dome that mutually separates two areas, an intake side 4a and an exhaust side 4b, as shown in FIGS. 1 and 2, for example. A sub-spherical engine combustion chamber 5 is formed of a dome portion (circular concave portion) 5a and a second dome portion (circular concave portion) 5b. The first part forming the combustion chamber 5
As shown in FIG.
is formed with a predetermined larger diameter, and when viewed from above, the intake side 4
It is deformed into a daruma shape from a to the exhaust side 4b, and on the outer periphery of both dome areas, there is a skin area 7 that is wider on the intake side 4a and relatively narrower on the exhaust side 4b.
a, 7 b are formed. The squish area 7a,
7b functions to improve combustion performance by forming a so-called squish (compression vortex) particularly in this region during the engine compression stroke.

Further, numeral 8 is an intake boat, and 9 is an exhaust boat. The intake boat 8 is configured with two sets of boats: a main boat 8A and a swirl boat (secondary boat) 8B.In addition, on the main boat 1-8A side, there is a soter valve that opens and closes the main boat 8A. 0 is set. The Nyatter valve 10 closes, for example, in a low-speed, low-load region, and allows a high flow of flow only from the swirl boat 8B into the engine combustion chamber 5 through the protrusion 13 of the dome portion 5b of the large-diameter exhaust side pipe 2. By allowing the injected fuel to flow in the circumferential direction toward the inner circumferential surface portion 14 slightly inside (on the end side), the injected fuel can be atomized well, and the mixture in the combustion chamber can be effectively mixed while improving the mixing of the fuel and air. The aim is to create a layered structure. As a result, combustibility is improved as much as possible to compensate for the drop in engine torque in the low-speed, low-load region, and fuel efficiency is improved.

On the other hand, when the engine is operating at high speed and high load,
The shutter valve 10 is wide open and the intake boat 8
The overall diameter of the intake passage is enlarged to supply a sufficient amount of intake air with low intake resistance and to improve output in response to high engine speeds.

Further, reference numeral 11 denotes a fuel injector that is configured to have a timed injection function that injects fuel in synchronization with the intake stroke of the engine, for example. The fuel injector II is connected to the main intake boat 8.
A and the intake manifold 12 that is continuous with the intake boat 8A.
As shown in FIG. 2, the fuel flows in the same direction as the inflow direction of the swirl flow above the channel, and toward the outside (radial direction of the dome part) of the electrode part +5a position of the spark plug 15, which will be described later. The injection direction is set to inject synchronously. As a result, the fuel injected in synchronization with the engine intake stroke by the timed injection rides on the swirl flow formed by the swirl boat 8B and does not directly hit the electrode portion 15a of the spark plug 15. It comes to be gathered near the electrode part +5a.

As a result, the concentration of the air-fuel mixture especially near the electrode portion +5a of the spark plug 15 becomes rich, and the ignitability improves. This effect is combined with the relationship between the installation position and installation angle of the spark plug 15, which will be described below, to achieve a more effective effect.

That is, the spark plug 15 is located, for example, in the swirl inlet part in the dome part 5b of the exhaust pipe 2, and is located in the head mating surface (of the gasket 2) of the combustion chamber wall on the downstream side of the swirl, as shown in FIG. The installation angle θ with respect to the swirl surface) is set larger on the swirl downstream side O7 than on the swirl upstream side 01 (θ
, >θ), and is installed with a wedge-shaped concave portion 35 formed therein.

Therefore, the downstream wall surface portion of the wedge-shaped concave portion 35 becomes a shape resistance portion, and the relatively rich air-fuel mixture is effectively supplied riding on the swirl flow as described above by the timed injector. As shown by arrow (a), the current is gently raised (bent) upward near the electrode portion +5a of the spark plug 15, and the electrode portion 1 of the spark plug 15 is
It comes to stay near 5a in a stratified state for a predetermined time. Therefore, the above-mentioned effect of improving ignitability can be more effectively improved. Furthermore, in this case, fuel that is particularly poorly atomized collides with the wall surface due to its inertia and is reflected and scattered near the spark plug. Therefore, the degree of enrichment becomes higher.

Next, reference numeral 20 denotes a piston fitted into the cylinder bore 3 via a piston ring 20a so as to be vertically slidable. The piston 20 is vertically movably supported by a connecting rod 22 via a piston pin 21, and the piston head upper surface 23 has a concave groove in the opposite direction corresponding to the shape of the combustion chamber 5 on the cylinder head side. The first dome portion 21a and the second dome portion 21b are formed to intersect with each other. In this case, the first and second dome portions 21a on the piston head 23 side,
The protrusion 24 on the downstream side of the swirl between 21b is located downstream of the swirl far from the spark plug [5],
As mentioned above, the stratified mixture flow ignited via the spark plug 15 is further disturbed by the downstream protrusion 24 to form a turbulent flow due to tumble air motion, which further promotes combustion in the end side zone far from the spark plug. It also greatly improves performance.

In addition, in 1. FIG. 1 and FIG. 2, the reference numeral 31a is
The intake valve 31b is an exhaust valve, and in order to improve the swirl efficiency, the intake valve 31a is preferably offset by a predetermined position σ in the direction opposite to the outlet of the swirl boat 8B, as shown in FIG. 2, for example.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the structure of a combustion chamber of an engine according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. Figure 3 is an enlarged cross-sectional view of the spark plug mounting part of the same embodiment structure (Figure 2B-
B), FIG. 4 is a plan view showing the shape of the upper surface of the piston head in the same embodiment structure. 1a... Cylinder block lb ・ 2 ・ ・ 3 ・ ・ 4 a ・ 4b ・ 5 ・ ・ 5a ・ 5b ・ 7a ・ 7b ・ 8 ・ ・ 8 A ・ 8B ・ 9 ・ ・ IO ・ 20 ・ 1a 1b ・cylinder head, gasket, cylinder bore, intake side, exhaust side, combustion chamber, first dome section, second dome section, intake side squish area, exhaust side squish area, intake boat, main boat, swirl boat, exhaust boat , Nyatta valve inner piston, first dome part, second dome part

Claims (1)

[Claims] 1. In an engine in which a dome-shaped combustion chamber of a predetermined size is formed on the lower surface of the cylinder head, and an ignition plug is faced from the upper part of the cylinder head at a predetermined position offset to the side within the dome-shaped combustion chamber, the above-mentioned ignition The air-fuel mixture is introduced toward the circumferential surface of the dome-shaped combustion chamber adjacent to the plug, and the angle of inclination of the wall surface near the spark plug installation portion of the circumferential surface of the dome-shaped combustion chamber is made greater than that on the upstream side. 1. A combustion chamber for an engine, characterized in that the downstream side is enlarged, and the flow of the introduced air-fuel mixture is bent in a predetermined direction, thereby forming a shaped resistance section that temporarily stagnates the flow of the air-fuel mixture.