JP3153289B2 - Engine combustion chamber structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure of an engine.

[0002]

2. Description of the Related Art Some engines have a multi-point ignition system in which a plurality of ignition gaps are provided for one combustion chamber. JP-A-60-43128, JP-A-60-43
No. 178 discloses an arrangement in which a plurality of ignition gaps are arranged at intervals on a predetermined axis extending in the diameter direction of the combustion chamber through the center or substantially the center of the combustion chamber. The one disclosed in this publication is intended to cause rapid combustion by igniting an air-fuel mixture using a plurality of ignition gaps so as to approach as close as possible equal-capacity combustion which is ideal in an Otto-type engine. It is.

[0003]

[Problems to be solved by the invention] By the way, recently,
It has been considered that the combustion ratio is made as uniform as possible to reduce harmful components in the exhaust gas. That is, the combustion speed peak
The aim is to reduce NOx by minimizing the fuel pressure as much as possible, and to reduce HC by sufficiently oxidizing fuel vapor (air-fuel mixture) even at the outer peripheral edge of the combustion chamber.

Accordingly, it is an object of the present invention to provide a combustion chamber structure of an engine capable of satisfying a demand for making the combustion ratio uniform.

In order to achieve the above object, the present invention basically adopts the following configuration. That is, in an engine in which the air-fuel mixture supplied to the combustion chamber is ignited by the ignition gap, at the initial stage of combustion of the ignited air-fuel mixture, the burned zone includes the center of the combustion chamber and extends in the diameter direction of the combustion chamber. A plurality of ignition gaps are provided to form a substantially columnar flame surface so as to extend elongated over the entire length, and the plurality of ignition gaps include a center ignition gap disposed substantially at the center of the combustion chamber, A peripheral ignition gap disposed at the periphery of the combustion chamber with the center ignition gap interposed therebetween in the diameter direction of the combustion chamber passing through the ignition gap, and when the mixture is ignited simultaneously by the ignition gaps, So that the flame surfaces spreading from the ignition gaps collide at substantially the same time,
In the diameter direction, the interval between the two ignition gaps on the high-temperature portion side with respect to the substantially central portion of the combustion chamber is set larger than the interval between the two ignition gaps on the low-temperature portion side with respect to the substantially central portion of the combustion chamber. It has such a configuration.

In the combustion chamber structure of the present invention, in order to obtain the above-described combustion, the ignition gaps are arranged at intervals in the direction in which the burned zone extends in a slender manner, that is, at intervals in the diameter direction of the combustion chamber. It is arranged to open a plurality. In this case, all the ignition gaps can be arranged in the extension region of the cylinder, that is, in such a manner that the ignition gap is located in the cylinder bore when viewed from the cylinder axis direction.

The burned zone formed at the beginning of combustion is preferably formed as narrow as possible in order to suppress the combustion ratio. From such a viewpoint, it is possible to set the arrangement position and the number of each ignition gap in consideration of the direction in which the flame surface advances and the temperature of the combustion chamber wall surface which affects the flame propagation speed.

[0009]

According to the present invention, NOx and HC can be greatly reduced by making the combustion ratio as uniform as possible.
That is, NOx is reduced by reducing the peak value of the combustion ratio. Further, the fuel vapor (air-fuel mixture) is sufficiently oxidized at the outer peripheral portion of the combustion chamber, so that HC which is easily generated at the outer peripheral portion of the combustion chamber can be reduced.

[0010] In particular, when a burned zone extending over the entire length in the diameter direction of the combustion chamber is formed at the initial stage of combustion, an outer peripheral edge portion of the combustion chamber located at each longitudinal end of the burned zone. In particular, since sufficient combustion is performed and the outer peripheral portion of the combustion chamber at the end of combustion is only a part of the entire circumferential direction of the combustion chamber, HC is reduced as a whole.

The burned zone for obtaining a substantially columnar flame surface at the beginning of combustion is preferably as narrow as possible from the viewpoint of making the combustion ratio uniform. Therefore, by setting the arrangement of the ignition gap in consideration of various factors that affect the formation of the substantially columnar flame surface, that is, the traveling direction of the flame surface and the flame propagation speed, the combustion ratio is made uniform. Is performed more sufficiently to reduce NOx and HC more effectively.

[0012] Ideally, the ignition gap can be shaped to be elongated over the entire diametric length of the combustion chamber. However, in this case, the power consumption becomes large, or it becomes difficult to ignite all the parts simultaneously over the entire length in the diameter direction of the combustion chamber. It is practical to configure the ignition gap. Preferred aspects of the invention and its advantages will be apparent from the description of the following examples.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a basic description of the present invention will be given based on FIG. In FIG. 1, reference numeral 1 denotes a combustion chamber as viewed from the cylinder axis direction. The combustion chamber 1 has four ignition gaps G spaced apart on a predetermined axis extending through the center of the combustion chamber 1 in the diameter direction of the combustion chamber.
1, G2, G3 and G4 are arranged. The distance between the adjacent ignition gaps is equal to each other, and the distance between the ignition gap G1 or G4 at the further end and the wall surface of the combustion chamber in the immediate vicinity is approximately half the distance between the adjacent ignition gaps. . FIG. 1 shows the arrangement of the ignition gap when the temperatures of the combustion chambers are all in an ideal state. However, in an actual engine, a temperature difference occurs in the combustion chamber. The arrangement of the ignition gap of the present invention in consideration of the above will be described later.

When the ignition gaps G1 to G4 are simultaneously ignited, the mixture supplied to the combustion chamber 1 is ignited for each of the ignition gaps G1 to G4. The progress of the flame surface generated by this ignition is shown for each of the times t1 to t9. That is, each of the ignition gaps G1 to G4
The flame surfaces extending in a circular shape from each other coincide with each other at time t4, and at this time t4, the burned zone including the center of the combustion chamber 1 and extending over the entire length in the diameter direction of the combustion chamber 1 is formed. The burned zone formed at this time is indicated by the symbol α with hatching. In this way, at time t4, a substantially columnar flame surface extending over the entire length in the diameter direction of the combustion chamber 2 is formed (formation of a substantially columnar flame surface at time t4), and the unburned fuel in the combustion chamber 1 is formed. − Β, γ
Is divided into two by the burned zone α.

After t4, the flame surface advances in a direction substantially orthogonal to the arrangement direction of the ignition gaps G1 to G4, such as t5 and t6, and the combustion ends after t9.

FIG. 15 shows a combustion state of the present invention together with a comparative example. In Comparative Example 1, the center of the combustion chamber 1 was
A case in which ignition is performed by arranging two ignition gaps is shown, and Comparative Example 2 is disclosed in the above-mentioned Japanese Utility Model Publication No. 60-43128.

As described above, according to the present invention, it is easily understood that the combustion ratio is made uniform. Here, in the present invention, as shown in FIG. 4, two shelf portions m and n having substantially the same heat generation ratio are formed as the combustion proceeds. The combustion according to the present invention including the shelves m and n will be described below in more detail. First, each ignition gap G1
Immediately after the ignition at G4, the flame surface expands in a circular shape around each of the ignition gaps G1 to G4, so that the combustion ratio increases with time. And each ignition gap G
The flame surfaces generated in 1 to G4 collide with each other to form the burned zone α in FIG. The air-fuel mixture burned so far is about 30 to 40% by volume and about 10 to 20% by mass.

At the time point t4 when the burned zone α is formed, the area of the flame surface decreases due to the collision between the flame surfaces, and the combustion ratio thereafter becomes substantially the same as indicated by the shelf m. As the combustion further proceeds, the combustion ratio slightly increases, but immediately becomes the state of the shelf n, and the combustion proceeds with the combustion ratio again at substantially the same value. This shelf n is formed by
It is considered that the combustion in the portion where the bend of the combustion chamber 1 becomes large suppresses the growth of the flame surface. The air-fuel mixture that burns just before the shelf n is about 60 to 70% by volume and about 30 to 40% by mass.

As described above, the increase in the combustion ratio is suppressed when the first shelf m is reached, and the combustion is suppressed again when the second shelf n is reached, so that the combustion ratio is made uniform as a whole. As a result, NOx and HC, especially NOX, are greatly reduced.

Next, a more specific example of the present invention will be described with reference to FIG. FIG.
Two intake ports 11, 12 and two exhaust ports 13, 1
4 shows an example in which openings are formed. In FIG. 3, reference symbol L denotes a line passing through the center of the combustion chamber 1 and perpendicular to the crankshaft, and the intake ports 11, 12 and the exhaust ports 13, 14 are mutually opposite regions with the line L as a boundary. It is open to. The two intake ports 11 and 12 are arranged in parallel with each other in the line L direction, and similarly, the two exhaust ports 13 and 14 are also arranged in the line L.
It is arranged in parallel in the direction.

The combustion chamber 1 has three ignition gaps G11.
G13 are provided, and the ignition gaps G11 and G13 are arranged at intervals on the line L. The ignition gaps G11 to G13 are located in the cylinder extension region. In the direction of the line L, the distance between the ignition gap G1 and the wall surface of the nearest combustion chamber is a, the distance between G11 and G12 is b, the distance between G12 and G13 is c, G
The distance between 13 and the nearest wall surface of the combustion chamber is d. In the figure, the hatched area, that is, the area on the exhaust port 13, 14 side with respect to the center of the combustion chamber, and the other area, that is, the intake port 11, 12 with respect to the center of the combustion chamber.
The temperature is higher than the side region. In other words, the flame propagation speed on the exhaust port 13, 14 side is
It is faster than the flame propagation speed on the 1 and 12 sides.

When the ignition is performed simultaneously in each of the ignition gaps G11, G12, and G13, the surrounding ignition gaps G11 and G11 are taken into account in consideration of the flame propagation speed difference caused by the above-mentioned temperature difference.
The timing at which the flame generated at the point of collision with the flame generated at the central ignition gap G12 is determined by the peripheral ignition gap G13
So that the time when the flame generated in the above and the time when the flame generated in the central ignition gap G12 collides is substantially the same time,
b <c. Further, a <d is set.

Although the embodiment has been described above, by adjusting the ignition timing between a plurality of ignition gaps, a burned zone α having substantially the same width can be formed over the entire length in the diameter direction of the combustion chamber. . More specifically, in consideration of the fact that there are regions having different flame propagation speeds in the combustion chamber, the ignition timing of the ignition gap arranged in the region where the flame propagation speed is higher is set to the region where the flame propagation is slower. May be set to be later than the ignition timing of the ignition gap arranged at.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a basic principle of the present invention.

FIG. 2 is a side sectional view showing a specific example of the present invention.

FIG. 3 is a view of the combustion chamber shown in FIG. 2 as viewed from a lower surface side of a cylinder head.

FIG. 15 is a diagram schematically showing a combustion mode of the present invention together with a comparative example.

[Description of Signs] 1: Combustion chamber 2: Cylinder head 3: Cylinder block 11, 12: Intake port 13, 14: Exhaust port G1 to G4: Ignition gap G11 to G13: Ignition gap α: Initial combustion Burned zone β, γ: unburned zone at the beginning of combustion

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidetoshi Kudo 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-5-18243 (JP, A) JP-A Sho-62 JP-A-182422 (JP, A) JP-A-53-17805 (JP, A) JP-A-54-28917 (JP, A) JP-A-54-22007 (JP, A) JP-A-52-109007 (JP, A) 60/43178 (JP, U) 60/43128 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 1/00-23/10 F02P 15 / 08

Claims (2)

(57) [Claims] In an engine in which an air-fuel mixture supplied to a combustion chamber is ignited by an ignition gap, a burned zone includes a center of the combustion chamber and the combustion chamber at an initial stage of combustion of the ignited air-fuel mixture. a plurality for forming a flame front substantially columnar as elongating across the diametrically full length
Ignition gaps are provided, and the plurality of ignition gaps are disposed substantially at the center of the combustion chamber.
Center ignition gap and combustion through the center ignition gap
Combustion across the central ignition gap in the diameter direction of the chamber
A peripheral ignition gap disposed at the periphery of the chamber, and the mixture is ignited simultaneously by the ignition gaps.
Sometimes it widens from each ignition gap in the diameter direction
So that the flame surfaces collide at approximately the same time.
Both points on the high temperature side with respect to the approximate center of the combustion chamber at
The gap of the fire gap is closer to the low temperature part than the center of the combustion chamber
The combustion chamber structure of the engine, wherein the interval is set larger than the interval between the two ignition gaps . 2. The diametrical direction according to claim 1, wherein said plurality of ignition gaps are arranged in an array direction.
From the opening of the intake port to the combustion chamber.
The center ignition gap and the opening of the exhaust port.
The distance between the central ignition gap and the peripheral ignition gap is
And the peripheral ignition gear on the opening side of the intake port.
The combustion chamber structure of the engine, wherein the interval is set to be larger than the gap between the engine and the engine .