JP2006009660A - Two-point ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-point ignition internal combustion engine realizing improvement in fuel consumption and suppression of knocking. <P>SOLUTION: Two ignition plugs (30, 32) and two intake port parts (10, 12) are provided to the upper wall of a combustion chamber (1). EGR gas is introduced to only one intake port part (10) between two intake port parts, and independent tumble flows (50, 52) are produced at the time of suction. Thereby, two regions are retained in the combustion chamber, one region containing EGR gas is ignited firstly, and the other region with an air-fuel mixture only is ignited lastly. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a two-point ignition internal combustion engine that performs ignition at two locations in a combustion chamber.

In recent years, multi-point ignition internal combustion engines have been developed in which two or more spark plugs are provided in one cylinder and ignition is performed at several points in the combustion chamber.
A multi-point ignition internal combustion engine can improve fuel efficiency by igniting with a plurality of spark plugs, shortening the flame propagation time in the combustion chamber, completing combustion rapidly, and extracting high output with less fuel. It is effective. Further, rapid combustion is effective in suppressing knocking, and there is an advantage that the compression ratio can be set higher. Also, so-called phase difference ignition for controlling the ignition timing of a plurality of spark plugs can be performed, and the above effect can be obtained efficiently by performing ignition control or the like according to the state of the engine.

However, since there are a plurality of spark plugs, there is a problem that the intake valve and exhaust valve layout provided on the upper wall of the combustion chamber is more limited than the conventional one-point ignition internal combustion engine, and the amount of intake air is reduced. It was.
For example, as such a multi-point ignition internal combustion engine, one exhaust valve, two intake valves, and two spark plugs are provided, fuels having different octane numbers are supplied to the two intake ports, and they are resistant to high-load operation. In order to improve knocking and to suppress NOx emission during low load operation, a technique for controlling the ignition timing of each spark plug so as to promote automatic ignition of fuel has been developed (see Patent Document 1).
JP 2000-154771 A

However, in the technique disclosed in Patent Document 1, fuels having different octane numbers must be supplied in order to adjust the automatic ignition of the fuel. In order to supply two types of fuel in this way, two types of fuel tanks or volatilization chambers must be provided, resulting in a complicated structure and extra costs.
The present invention has been made to solve such problems, and an object of the present invention is to provide a two-point ignition internal combustion engine that has a simple configuration and can improve fuel consumption.

  In order to achieve the above object, in the two-point ignition internal combustion engine according to claim 1, a combustion chamber surrounded by a cylinder, a lower surface of the cylinder head and an upper surface of the piston, and a cylinder among the lower surface of the cylinder head. Two intake openings formed side by side on a plane including an axis, and a central portion between the two intake openings on the other side of the plane including the cylinder axis on the lower surface of the cylinder head An ignition opening provided on each side of a plane including one exhaust opening formed so as to be positioned and the center and the cylinder axis of the cylinder head so that the ignition section faces the combustion chamber. A pair of intake ports formed in the cylinder head so that intake air from the two intake openings into the combustion chamber generates independent tumble flows in the combustion chamber; A fuel injection valve that injects fuel into a pair of intake ports; and the exhaust gas that is connected to the pair of intake ports so that the amounts of exhaust gas introduced into the combustion chamber from the two intake openings are different from each other. It is characterized by comprising an EGR passage for reflux.

3. The two-point ignition internal combustion engine according to claim 2, wherein an ignition plug on the intake port side having a larger exhaust gas introduction amount from the EGR passage among the ignition plugs is on an intake port side having a smaller exhaust gas introduction amount. It is characterized by igniting before the stopper.
The two-point ignition internal combustion engine according to claim 3 is characterized in that the air-fuel ratio of the air-fuel mixture sucked into the combustion chamber is made leaner than the stoichiometric air-fuel ratio.

  According to the two-point ignition internal combustion engine of the present invention using the above means, two spark plugs (ignition plugs) are connected to the combustion chamber while securing a sufficient intake amount by using two intake valves and one exhaust valve. It can be laid out at a suitable position on the upper wall. Also, the amount of recirculation of exhaust gas (EGR gas) to the two intake ports is made different to generate independent tumble flows for each intake from the two intake openings, so that a large amount of EGR gas is contained in the combustion chamber. A region and a region with little or no EGR gas can be formed, thereby achieving optimal combustion in a two-point ignition internal combustion engine.

According to the two-point ignition internal combustion engine of claim 2, the low combustion rate region containing a large amount of EGR gas is ignited first, and the high combustion rate region containing little or no EGR gas is ignited later. By this, since the slow combustion that occurred first is accelerated by the fast combustion that occurred later, an increase in flame propagation time due to the mixing of EGR gas can be suppressed.
By recirculating the EGR gas, the oxygen concentration in the air-fuel mixture can be reduced, the NOx emission amount can be reduced, and the pumping loss of intake air can also be reduced.

Thus, with a simple configuration, stable combustion can be realized, and fuel consumption can be improved while suppressing NOx emission. Moreover, knocking can be suppressed and the compression ratio can be set higher.
According to the two-point ignition internal combustion engine of claim 3, since the intake air amount can be further increased by making the air-fuel ratio lean, the pumping loss can be reduced and the fuel efficiency can be further improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a perspective view showing a structure of a combustion chamber of a two-point ignition internal combustion engine according to the present invention. Referring to FIG. 2, an outline of a combustion chamber of a two-point ignition internal combustion engine according to the present invention. A plan view is shown. Hereinafter, a description will be given based on FIGS.
As shown in FIG. 1, the combustion chamber 1 is formed by being surrounded by a cylindrical cylinder 2, an upper surface of a piston 4 that is slidably inserted into the cylinder 2, and a lower surface of the cylinder head 6. Has been.

The upper surface of the piston 4 that is the floor surface of the combustion chamber 1 has a flat shape.
The lower surface of the cylinder head 6 that is the upper wall of the combustion chamber 1 has a pent roof shape, and on one side of the plane A including the cylinder axis X that is the central axis of the cylinder 2, that is, the inclined surface on the intake side of the pent roof shape, Two intake openings 10a and 12a are provided side by side and communicate with the intake port portions 10 and 12, respectively.

The intake ports 10 and 12 are formed in a shape in which the air-fuel mixture sucked into the combustion chamber 1 generates a tumble flow that is an independent vertical vortex as indicated by arrows 50 and 52.
The intake ports 10 and 12 are branched from one intake port 40 on the intake upstream side, and an injector (fuel injection valve) 42 is provided at the branched portion 40a.
Furthermore, one of the intake port portions 10 and 12 is connected to one end of an EGR pipe (EGR passage) 44, and the other end of the EGR pipe 44 is on the exhaust downstream side of the exhaust port 14. The exhaust manifold 46 is connected. An EGR valve 48 is provided in the middle of the EGR pipe 44, and the amount of EGR gas recirculated to the intake port unit 10 is adjusted by the EGR valve 48.

  On the other hand, on the other side of the plane A, that is, on the inclined surface on the exhaust side, the plane A is perpendicular to the plane A. One exhaust opening 14 a is provided in communication with the exhaust port 14. Further, the cylinder head 6 is provided with intake valves 20 and 22 for connecting and blocking the intake port portions 10 and 12 and the combustion chamber 1 and an exhaust valve 24 for connecting and blocking the exhaust port 14 and the combustion chamber 1. It is installed.

Spark plugs (ignition plugs) 30 and 32 are disposed at positions on the exhaust side of the lower surface of the cylinder head 6 and facing the intake valves 20 and 22 on both sides of the exhaust opening 14a. These spark plugs 30 and 32 are connected to an electronic control unit (not shown), and the ignition timing is controlled by the electronic control unit.
The operation of the two-point ignition internal combustion engine according to the present invention configured as described above will be described below.

First, in the intake stroke, the piston 4 is lowered and the intake valves 20 and 22 are opened, whereby intake is performed, and the air-fuel mixture enters the combustion chamber 1 from the intake openings 10a and 12a as indicated by arrows 50 and 52 in FIG. Inhaled while producing an independent tumble stream.
The air-fuel mixture here is obtained by injecting fuel from the injector 42 into the air that has branched into the intake port portions 10 and 12 through the intake port 40, and the EGR pipe 44 has introduced EGR from the EGR pipe 44. Gas is also mixed. Further, the air-fuel ratio of the air-fuel mixture at this time is set to be an air-fuel ratio that is relatively leaner than the stoichiometric air-fuel ratio.

In the compression stroke, the piston 4 rises and the intake valves 20 and 22 are also closed, so that the air-fuel mixture in the combustion chamber 1 is compressed. At this time, an air-fuel mixture region containing EGR gas on the intake port portion 10 side and an air-fuel mixture region not containing EGR gas on the intake port portion 12 side are generated by two independent tumble flows generated during intake. It is divided and compressed.
When the piston 4 reaches near the top dead center, first, ignition is performed by the spark plug 30 on the region side of the air-fuel mixture containing EGR gas, and combustion occurs in the expansion stroke. In the combustion, the EGR gas is contained in the air-fuel mixture, so the oxygen concentration is low and the combustion speed is relatively slow. And before the said combustion is completed, ignition by the spark plug 32 is performed to the area | region side of the air-fuel mixture which does not contain EGR gas, and comparatively quick combustion occurs. The slow combustion that is ignited earlier increases the combustion rate due to the effect of the fast combustion that was ignited later. The piston 4 is lowered by this combustion.

  In the exhaust stroke, the exhaust gas in the combustion chamber 1 generated by the combustion is discharged from the exhaust opening 14a to the exhaust port 14 as the piston 4 rises and the exhaust valve 24 opens. The exhaust gas is discharged from the exhaust port 14 to the outside through the exhaust manifold 46. Here, a part of the exhaust gas passing through the exhaust manifold 46 is recirculated to the intake port unit 10 through the EGR valve 44 as EGR gas in accordance with the adjustment amount of the EGR valve 48.

  Thus, in the two-point ignition internal combustion engine according to the present invention, the two ignition plugs 30 and 32 are laid out at suitable positions on the upper wall of the combustion chamber 1 while providing two intake openings and securing a sufficient intake amount. Since only one injector is required, the structure of the cylinder head can be simplified. Further, by using an EGR system with a lean air-fuel ratio, it is possible to reduce intake pumping loss while suppressing NOx emission. Furthermore, by generating two independent tumble flows, an area where the combustion speed is relatively slow due to inclusion of EGR gas and an area where the combustion speed is relatively fast because no EGR gas is contained are generated in the combustion chamber. By providing two spark plugs corresponding to these two regions, it is possible to ignite a region having a low combustion rate first and to ignite a region having a high combustion rate later. Thereby, even when the EGR system is used, the flame propagation time in the combustion chamber can be shortened and the combustion can be completed rapidly.

From these things, it is possible to achieve stable combustion with a simple configuration and improve fuel efficiency while suppressing NOx emission. Moreover, knocking can be suppressed and the compression ratio can be set higher.
Although the description of the embodiment of the two-point ignition internal combustion engine according to the present invention is finished above, the embodiment is not limited to the above embodiment.

For example, in the above embodiment, the air-fuel ratio is made lean, but the present invention is not limited to this, and it is preferable to switch to a high-output, high-torque air-fuel ratio during high-speed running or high load. Even if the air-fuel ratio is not lean, the fuel efficiency can be sufficiently improved by the early combustion by the two-point ignition, and the amount of NOx emission is reduced by the amount that the air-fuel ratio is not lean.
Moreover, in the said embodiment, although the shape of the upper surface of piston 4 was formed flat, it is not restricted to this, For example, in order to generate a tumble flow more smoothly, a protruding part etc. are formed on the upper surface of piston 4. By providing, independence of the two regions in the combustion chamber can be further ensured.

  Furthermore, in the above-described embodiment, the EGR pipe 44 is connected only to the intake port portion 10, but any configuration may be employed as long as the EGR gas introduction amount differs from that of the intake port portions 10, 12. The EGR pipe 44 may be connected to the intake port unit 12 or the intake port 40 if the amount of EGR gas introduced into the intake port unit 10 can be set large.

It is a perspective view which shows the structure of the combustion chamber of the two-point ignition internal combustion engine which concerns on this invention. 1 is a schematic plan view of a combustion chamber of a two-point ignition internal combustion engine according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Combustion chamber 10, 12 Intake port part 10a, 12a Intake opening part 14 Exhaust port 14a Exhaust opening part 20, 22 Intake valve 24 Exhaust valve 30, 32 Spark plug (ignition plug)
42 Injector (fuel injection valve)
44 EGR pipe (EGR passage)

Claims (3)

A combustion chamber formed by being surrounded by the lower surface of the cylinder and the cylinder head and the upper surface of the piston;
Of the lower surface of the cylinder head, two intake openings formed side by side on a plane including the cylinder axis,
One exhaust opening formed on the other side of the lower surface of the cylinder head on the other side of the plane including the cylinder axis so as to face the central part between the two intake openings,
A spark plug provided on the both sides of a plane including the center portion and the cylinder axis of the cylinder head so that an ignition portion faces the combustion chamber;
A pair of intake ports formed in the cylinder head such that intake air from the two intake openings into the combustion chamber generates independent tumble flows in the combustion chamber;
A fuel injection valve for injecting fuel into the pair of intake ports;
2. An EGR passage connected to the pair of intake ports and configured to recirculate the exhaust gas to the intake system so that the amounts of exhaust gas introduced into the combustion chamber from the two intake openings are different from each other. Point ignition internal combustion engine.   Among the spark plugs, the spark plug on the intake port side with the larger exhaust gas introduction amount from the EGR passage ignites before the spark plug on the intake port side with the smaller exhaust gas introduction amount. The two-point ignition internal combustion engine according to claim 1.   The two-point ignition internal combustion engine according to claim 1, wherein the air-fuel ratio of the air-fuel mixture sucked into the combustion chamber is made leaner than the stoichiometric air-fuel ratio.