JPS63212770A - Spark ignition engine - Google Patents

Abstract

PURPOSE:To improve the knocking resistance by forming a dense air fuel mixture layer at the outer periphery of a cylinder in a combustion chamber and providing an ignition means at the outer periphery of the cylinder forming the side face of the combustion chamber at the compression top dead point to reduce the uncombustible component at the time of combustion. CONSTITUTION:A control device 9 is fed with the engine rotating speed signal R, the rotation angle signal OMEGA of a crank shaft, and the inflow intake quantity signal Q and controls the injection timing, injection quantity, and ignition timing of an injector 7. An igniter 5 is provided with multiple spark gaps at a uniform distance near the inner periphery of an adiabatic wall 4. Multiple injection holes are radially provided on the injector 7, fuel is injected to the outer periphery of a cylinder in a combustion chamber 8 to stratify a dense air fuel mixture layer at this portion, and the injection timing is set to the ignition timing or earlier in the front half of the compression stroke at the latest to ensure the stratification. Accordingly, the dense air fuel mixture is stratified near the ignition point, thus the air fuel ratio is made lean as a whole, the uncombustible component is reduced, and the ignitability can be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention stratifies a rich air-fuel mixture near the ignition point.
This invention relates to a spark ignition piston internal combustion engine.

(Prior art) In a spark-ignition internal combustion engine, the fuel mixture near the spark plug is stratified richer than in other parts to improve ignition characteristics, and the engine is operated with a lean mixture as a whole, especially at low loads, to improve efficiency. Traditionally, methods have been used to increase the

An example of this conventional stratification method is to inject fuel into the intake boat at the end of the piston's intake stroke to complete the fuel supply just before the intake valve closes, and to transfer the fuel mixture to be charged into the cylinder into the cylinder. It is known that the charge is guided into the cylinder in a spiral around the axis, so that a rich fuel mixture is stratified near the spark plug located at a point in the approximate center of the cylinder head. There is. (Japanese Unexamined Patent Publication No. 58-85319) In this conventional method, in a low load range where a rich mixture is stratified near the spark plug, the amount of mixture in the combustion chamber is small, the compression temperature is low, and the ignition is particularly In the area around the cylinder far from the plug, the air-fuel ratio is thinner due to stratification.
Because it is easily cooled from the cylinder wall, combustibility is poor and unburned components, such as hydrocarbons (HC), tend to remain.

Moreover, as mentioned above, the combustibility is poor, and since the ignition is performed at one point, the probability of ignition is low, resulting in unstable combustion, resulting in a low lean limit for the fuel mixture.

In addition, in high load ranges where the overall air-fuel ratio in the combustion chamber is enriched to improve output, the amount of air-fuel mixture in the combustion chamber is large.
There was a problem in that knocking was more likely to occur due to the higher compression temperature and richer air-fuel ratio.

(Object of the invention) This invention solves the various conventional problems mentioned above, and
In internal combustion engines, where the overall air-fuel ratio is made leaner by stratifying a rich air-fuel mixture, it is possible to reduce non-combustible components (HC) during combustion, bring it closer to complete combustion, improve knocking resistance, and further reduce the leanness of the fuel mixture. The purpose is to expand the limits and provide a spark ignition engine with overall high combustion efficiency.

(Structure of the Invention) To achieve the above object, this invention forms a rich air-fuel mixture layer on the outer periphery of a cylinder in a combustion chamber in a piston-type internal combustion engine that stratifies a rich air-fuel mixture near the ignition point at least when the load is low. It is a spark ignition engine that is equipped with a stratification means such as an in-cylinder stratification injector, and a substantially circumferential ignition means on the outer periphery of the cylinder that forms the side surface of the combustion chamber at the top dead center of the compression stroke. .

In the above configuration, since the ignition occurs approximately circumferentially around the outer circumference of the cylinder, the probability of ignition is higher than that of conventional ignition at one point, and the flame propagates from the outer circumference of the cylinder toward the center, increasing the combustion speed. Therefore, even under low load, when a rich air-fuel mixture is stratified near the ignition point and the air-fuel ratio as a whole is to be operated at a lean air-fuel ratio, the center of the combustion chamber, where the air-fuel ratio is thin, is exposed to fast-burning flames from the surrounding area. The outer periphery has good combustibility and is easily cooled by the cylinder wall.
The combustion of the central part, which burns later, is compressed and the temperature rises (Hopkinson effect), making it possible to oxidize the unburned components remaining after combustion, thereby reducing the amount of unburned components.

In addition, as mentioned above, the unburned components can be reduced, the combustion rate is high and the combustibility is good, and the ignition probability is high, so the combustibility is stable, so the lean limit of the fuel mixture can be further expanded. Can be done.

Furthermore, under high load conditions, as the combustion speed is high as described above, the time during which the unburnt air-fuel mixture is exposed to the high temperature of the flame is shortened, and the non-king limit can be increased.

(Embodiments) The present invention will be described below based on embodiments shown in the drawings.

In the figure, (1) is the cylinder, (2) is the cylinder head, and (3) is the piston.The cylinder head (2) closes the upper end of the cylinder (1), and the piston (3) moves up and down inside the cylinder (1). The engine rotates by continuously repeating suction, compression, explosion, and exhaust.

(4) is a heat insulating wall made of a material with heat insulating and insulating properties such as ceramic, and is sandwiched between the cylinder (1) and the cylinder head (2), and has an inner diameter approximately the same as that of the cylinder (1). , the cylinder (1) is configured in an extended state, and an igniter (5) is built in as shown in FIG.

This igniter (5) is formed in a substantially circumferential shape, and has a heat insulating wall (4).
) There are multiple (6 locations in the figure) spark gaps (
5a) are provided at approximately equal intervals and are connected to an ignition source (6).

(7) is an injector, which is attached to the cylinder head (2), and its tip is connected to the combustion chamber (8) at the top of the cylinder (1).
As shown in Fig. 3, a plurality of injection holes (7a) facing toward the circumference above the combustion chamber (8) are provided in a radial manner to inject fuel into the outer circumference of the cylinder within the combustion chamber (8). This injection hole (7a) is configured to be injected to stratify a rich mixture layer in this area, and this injection hole (7a) is connected to the needle (7b) from inside.
), and to ensure stratification,
The injection timing is delayed from the first half of the compression stroke (both before the ignition timing).

(9) is a control device that outputs an engine rotational speed signal (R);
By inputting the rotation angle signal (Ω) of the crankshaft and the inflow intake air amount signal (Q), the injection timing and amount of the injector (7), and the ignition timing by turning on the ignition source (6) are set appropriately. It is intended to be controlled.

1 and 4, (10) is an intake valve, (1
1) is an intake boat, and the exhaust valve and exhaust port are not shown to avoid complication.

In addition to the above configuration, a squish portion (13
), and Figure 4 shows a piston (3) with a circularly protruding squish part (13) at the center of the upper end, and a squish area between it and the lower surface of the flat cylinder head (2). (14) to cause the mixture to flow in the direction of the arrow near the top dead center of the compression process,
By collecting the mixture at the outer circumference of the combustion chamber (8), which is the ignition position, the probability of ignition is increased, and the flow of the air-fuel mixture promotes initial combustion.
) begins to descend, a reverse squish phenomenon occurs and the flame flows from the periphery toward the center, promoting the propagation of the flame in the middle and late stages of combustion, accelerating the combustion speed, and reducing combustion fluctuations. This is something that can be reduced.

5(A)(B) and FIG. 6(C)(D) show other examples of the squish structure.
6 (C) (D ) is 4
A substantially rectangular squish portion (13) is provided in the center portion of the lower surface of the cylinder head (2) of the second valve, surrounded by two intake boats (11) and two exhaust ports (12). The operation and effect in the cases of FIGS. 5 and 6 are substantially the same as in the case shown in FIG. 4.

In the above embodiment, the cylinder (
Since a rich air-fuel mixture is stratified around the cylinder (1) by the injector (7) and ignited at multiple points by the igniter (5) around the outside of the cylinder (1), the reliability of ignition is extremely increased.

In addition, since the flame propagates from the periphery to the center of the cylinder (1), the propagation area becomes significantly larger, the combustion speed becomes faster, and the flammability improves. In particular, even the lean core receives the fast-burning flame from the surrounding area and burns well.

In addition, the outer circumferential part of the combustion chamber (8) is compressed by the pressure of the central part which will be combusted later, resulting in a temperature rise and the cylinder (8).
The heat dissipation from the peripheral wall (1) is prevented by the heat insulating wall (4) to maintain the high temperature.
The unburned components that remain after combustion and are emitted with the exhaust gas can be oxidized and replaced with effective combustion.

In addition, due to the above-mentioned improvement in ignition establishment and high-speed combustion, the air-fuel ratio is thin and it is difficult to burn, and the pressure rises in the unburned part of the center, which increases the temperature and makes it easier to burn in the center. By reducing partial combustion and combustion fluctuations,
It becomes possible to expand the lean limit, lowering the air-fuel ratio of the air-fuel mixture and saving fuel.

Furthermore, since the combustion speed is high and the time that the unburned air-fuel mixture is exposed to high temperatures is shortened, the knocking limit can be increased.

In the above embodiment, a means for directly injecting fuel into the combustion chamber was used as a means to stratify a rich air-fuel mixture around the outer circumference of the cylinder, but a fuel supply device was provided in the intake passage to utilize swirl. It is also possible to form a stratification on the outer circumference of the cylinder, and the effects of the present invention can also be obtained by doing so.

(Effects of the Invention) According to the spark ignition period according to the present invention explained above, a rich mixture is stratified near the ignition point at low load, and the air-fuel ratio is made lean as a whole, and it remains during combustion and is emitted. By reducing the amount of non-combustible components (HC) produced and converting them into effective combustion, and improving ignitability, it is possible to expand the lean limit of the fuel mixture and save fuel, and even at high loads. This results in improved knocking resistance.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of main parts showing one embodiment of the present invention;
The figures are a sectional view taken along the line nn in Fig. 1, Fig. 3 is an enlarged sectional view of the tip of the injector, Fig. 4 is a vertical sectional view of the main part of an embodiment with a squish structure, and Fig. 5 is an alternative view of an embodiment with a squish structure. 6 is a diagram showing an embodiment, (A) is a vertical sectional view of the main part, (B) is a top plan view of the piston, FIG. 6 is a diagram showing still another embodiment of the squish structure, and (C) is a diagram showing the inside of the cylinder. (D) is a vertical cross-sectional view of the main part. (1)...Cylinder (2)...Cylinder head (
3) Piston (4) Insulating wall (5) Igniter (5a) Spark gap (6) Ignition source
(7)... Injector (8)... Combustion chamber RnQ g/E1 drawing engraving 1 Fig. 3 Fig. 2 Fig. 4 Fig. 6 Fig. 5 Procedure correction writing method) Patented on May 28, 1986 Agency Director Black 1) Akira Total number 1 1, Indication of the case 1988 Patent No. 46167 2 Name of the invention
Spark ignition engine 3, Relationship with the case of the person making the amendment Patent applicant 4, agent Postal code 730 The drawing numbers of Figures 2 and 8 are written on the drawings.

Claims (1)

[Claims] In a piston internal combustion engine that stratifies a rich mixture near the ignition point at least at low loads, a stratification means forms a rich mixture layer around the outer circumference of the cylinder in the combustion chamber, and a side surface of the combustion chamber at compression top dead center. 1. A spark ignition engine, characterized in that a substantially circumferential ignition means is provided on the outer periphery of a cylinder forming a cylinder.