JPH0719053A - Combustion chamber structure for engine - Google Patents

Abstract

PURPOSE:To level off the propagation of flame, and reduce NOx effectively by offsetting the center of a projecting part to the center of a combustion chamber so that respective distances between the projecting part formed on a top surface of a piston and plural peripheral ignition gaps arranged in an outer peripheral end part of the combustion chamber become equal to each other. CONSTITUTION:An inside surface of a cylinder head 1 has a ridgeline (alpha) extending in parallel with the diameter direction of a cylinder by passing through the center O1 of a combustion chamber 2, and has a pair of inclined surfaces 1a and 1b with the ridgeline (alpha) as its boundary. By the way, the first to the third respective peripheral ignition gaps 11 to 13 are arranged at intervals in the circumferential direction of the combustion chamber 2 on an outer peripheral end part of the combustion chamber 2 in the cylinder head l. On the other hand, a projecting part 23 is formed integrally on a top surface of a piston 22. The center O2 of the projecting part 23 is offset by a prescribed distance R to the second peripheral ignition gas 12 side on the ridgeline (alpha) to the center line O1 of the combustion chamber 2. Thereby, respective distances between the respective peripheral ignition gaps 11 to 13 and the projecting part 23 are set equal to each other.

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 As a combustion chamber of an engine, an increasing number of engines have adopted a Pentorf type combustion chamber from the viewpoints of multiple intake / exhaust valves. In this pentorf type combustion chamber, the inner surface of the cylinder head that constitutes the upper surface of the combustion chamber is
It has a pair of inclined surfaces that are respectively inclined at a ridge line extending substantially parallel to the cylinder diameter direction. One of the inclined surfaces has an intake port opened and the other inclined surface has an exhaust port opened. It

By the way, in recent engines, reduction of HC, CO and NOx is strongly demanded from the viewpoint of exhaust gas purification. From this point of view, the applicant
We have developed a new combustion-type engine with peripheral ignition.
This is because a plurality of ignition gaps (peripheral ignition gaps) are arranged in the outer peripheral edge portion of the combustion chamber at intervals in the combustion chamber circumferential direction, and the flame ignited in each peripheral ignition gap is first in the combustion chamber circumferential direction. It is intended to collide at the center of the combustion chamber and then at the center of the combustion chamber. As a result, HC and CO that are likely to be generated around the combustion chamber are reduced, rapid combustion is suppressed, and NOx is also reduced (Japanese Patent Laid-Open No. 3-28).
6185).

In order to obtain a sufficient effect of the above-mentioned peripheral ignition system, it is more preferable to form a substantially cylindrical projection on the top surface of the piston in order to suppress the combustion flame from going to the center of the combustion chamber. Becomes The center of the substantially cylindrical protrusion is set to coincide with the center of the combustion chamber, that is, the center of the piston.

[0005]

In the above-mentioned peripheral ignition type engine, a plurality of ignition gaps are required for one combustion chamber. However, due to various restrictions, the peripheral ignition gap and the center of the combustion chamber are separated from each other. There are cases in which the distances in the radial direction of the combustion chamber have to be considerably different. That is, the ignition gap, that is, the spark plug is attached to, for example, the intake / exhaust port.
Of the engine, cooling water passages, etc., and in a multi-cylinder engine that has multiple cylinders in series in the crankshaft direction, avoid interference with the spark plugs for adjacent cylinders, and also install and remove the spark plugs as easily as possible. Due to such restrictions as described above, there may be a case where the distances between the peripheral ignition gaps and the center of the combustion chamber in the radial direction of the combustion chamber have to be greatly different as described above.

As described above, when the distance between the peripheral ignition gap and the center of the combustion chamber in the radial direction of the combustion chamber is greatly different, the distance between the peripheral ignition gap and the outer peripheral surface of the substantially cylindrical projection is greatly different in the radial direction of the combustion chamber. Will be done. This means that the mode of flame spread when the flame generated in each peripheral ignition gap is directed to the center of the combustion chamber is different, and the effect of the peripheral ignition system is reduced, especially the effect of reducing NOx is reduced. Will end up.

Accordingly, it is an object of the present invention that the radial distance between the plurality of peripheral ignition gaps and the center of the combustion chamber is
An object of the present invention is to provide a combustion chamber structure of an engine capable of sufficiently exerting the effect of reducing NOx even when at least a part of the peripheral ignition gap is different.

[0008]

In order to achieve the above object, the present invention has the following configuration. That is, in the outer peripheral edge of the combustion chamber, a plurality of peripheral ignition gaps are arranged at intervals in the combustion chamber circumferential direction, and on the piston top surface,
A substantially columnar protrusion is formed to suppress the transfer of combustion flame to the center of the combustion chamber, and the distance between the plurality of peripheral ignition gaps and the center of the combustion chamber in the combustion chamber radial direction is at least part of the peripheral ignition gap. Differently, the center of the protrusion is offset from the center of the combustion chamber so that the distance between the outer peripheral surface of the protrusion and each of the peripheral ignition gaps is substantially equal to each other. It is as a configuration.

A preferred embodiment of the present invention is as set forth in claim 2 and the following claims.

[0010]

According to the present invention as set forth in claim 1, the substantially cylindrical projection formed on the top surface of the piston is offset with respect to the center of the combustion chamber, and each peripheral ignition gap and the projection are formed. Since the distance in the radial direction of the combustion chamber from the outer peripheral surface of the portion is made substantially equal, the mode of flame spread toward the center of the combustion chamber of the flame generated in each peripheral ignition gap is made substantially equal,
The effect of reducing NOx can be sufficiently exerted.

With the structure as set forth in claim 2, the ignition gap, that is, the ignition plug is attached to and held in the cylinder head to make maintenance and inspection thereof as easy as possible, and for the cylinder block and the like. This is preferable in that the design of other engine components is not significantly changed.

With the structure as described in claim 3, a multi-cylinder, two intake ports and two exhaust ports, which are commonly used in recent engines, especially automobile engines, are provided. In the engine, the above-mentioned effects can be obtained.

With the construction as described in claim 4, the above-mentioned effect can be obtained even in the case of using the Pentor-fu type combustion chamber which is generally used in recent automobile engines.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, the inner surface of the cylinder head 1 is set to have a shape that forms a Pentorf-type combustion chamber 2. That is, as is clear from also referring to FIG. 2 and FIG. 3, the inner surface of the cylinder head 1 has a ridge line α passing through the center O1 of the combustion chamber 2 and extending parallel to the cylinder diameter direction. A pair of inclined surfaces 1 with α as the boundary
a and 1b. Of course, each of the inclined surfaces 1a and 1b is inclined so as to gradually move downward as the distance from the ridge line α increases. Further, in the embodiment, the ridge line α extends parallel to the crankshaft and is located vertically above the crankshaft.

The cylinder head 1 has one inclined surface 1a.
In the portion, two intake ports 3 and 4 are opened at intervals in the crankshaft direction (ridge line α direction). Two exhaust ports 5 and 6 are opened in the other inclined surface 1b at intervals in the crankshaft direction. Each intake / exhaust port 3 to 6 is opened / closed at a known timing in synchronization with the rotation of the crankshaft by an intake valve or an exhaust valve (not shown).

In the cylinder head 1, a total of three peripheral ignition gaps (ignition plugs) 11 to 13 are provided at the outer peripheral edge of the combustion chamber 2 at intervals in the circumferential direction of the combustion chamber.
Is provided. The first peripheral ignition gap 11 is located approximately in the middle of the two intake ports 3 and 4. The second peripheral ignition gap 12 is located near the exhaust port 5 between the intake port 3 and the exhaust port 5. The third peripheral ignition gap 13 is located between the intake port 4 and the exhaust port 6 and near the exhaust port 6. Further, the cylinder head 1 is provided with a central ignition gap 10 at the center O1 position of the combustion chamber 2. It should be noted that the cylinder head 1 is formed with a recess for accommodating the peripheral ignition gaps 11 to 13 so as to open to the combustion chamber 2.

In FIGS. 2 and 3, reference numeral 21 is a cylinder block, 22 is a piston, and a projection 23 is integrally formed on the top surface of the piston 22. This protrusion 2
3 is formed so as to have a cylindrical shape, and its center is indicated by O2. The center O2 of the protrusion 23 is
For a reason described later, the center of the combustion chamber 2 (center of the piston 22) is offset by a predetermined distance R on the ridge line α toward the second peripheral ignition gap 12 side.

Next, the distance between the peripheral ignition gaps 11 to 13 and the combustion chamber center O1 in the combustion chamber radial direction will be described. First, the first and third peripheral ignition gaps 11 and 12 are located slightly outward of the outer peripheral edge of the combustion chamber, that is, the inner surface of the cylinder. On the other hand, the third peripheral ignition gap 13 is located slightly closer to the center of the combustion chamber than the outer peripheral edge of the combustion chamber. As a result, the distance between the first peripheral ignition gap 11 and the center O1 in the combustion chamber radial direction and the distance between the second peripheral ignition gap 12 and the center O1 in the combustion chamber radial direction are made substantially equal, but the third peripheral ignition gap. Thirteen
The distance between the center O1 and the center O1 in the radial direction of the combustion chamber is small.

Considering the difference in the radial direction of the combustion chamber between each of the peripheral ignition gaps 11 to 13 and the combustion chamber center O1, the center O2 of the protrusion 23 is the second on the ridge line α.
The peripheral ignition gap 12 side is offset by a predetermined amount R. By this offset, each peripheral ignition gap 1
1 to 13 and the distances r1 to r3 in the combustion chamber radial direction from the outer peripheral surface of the protrusion 23 to each other.

Of the four ignition gaps 10 to 13, in the low load and low rotation range, the peripheral ignition gaps 11 to 11 are provided.
A peripheral ignition system is adopted in which only the center ignition gap 10 is ignited while the center ignition gap 10 is stopped. Further, in the high load or high rotation range, all the ignition gaps 10 to 14 are all ignited, or only the central ignition gap 10 is ignited.

In the above-mentioned structure, when only the peripheral ignition gaps 11 to 13 are ignited, the flames generated in the peripheral ignition gaps 11 to 13 coincide with each other in the circumferential direction of the combustion chamber at an early stage and the initial combustion is started. An annular flame is formed on the. As a result, the outer peripheral edge of the combustion chamber is satisfactorily burned, and HC and CO that are likely to be generated in this portion are reduced. The annular flame grows toward the center of the combustion chamber. The mode of heat generation due to such combustion is shown by the solid line in FIG. 4, and while the peak value of heat generation is reduced, heat generation is made uniform over the entire combustion period, and NOx is reduced. In particular, the peripheral ignition gaps 11 to 13 and the protrusion 23
Since the distances r1 to r3 from the outer peripheral surface in the radial direction of the combustion chamber are made equal, it is possible to substantially equalize the growth modes of the flame toward the center of the combustion chamber and sufficiently reduce NOx. The broken line in FIG. 4 shows a heat generation state when ignition is performed only by the central ignition gap 10.

FIG. 5 shows a case of a multi-cylinder engine in which a plurality of combustion chamber structures as shown in FIGS. 1 to 3 are arranged in series. That is, it has a structure having a plurality of combustion chambers in series in the crankshaft direction which is the direction of the ridge line α, and in the case of FIG. 5, the second cylinder C2 and the third cylinder C3 located in the middle of the in-line four-cylinder engine It shows the arrangement relationship with. As can be easily understood from FIG. 5, since the second peripheral ignition gap 12 and the third peripheral ignition gap 13 are adjacent to each other, combustion is performed with respect to the combustion chamber center O1 of the both 12 and 13. The chamber radial distances are different from each other.
In particular, the above-described difference in the radial distance of the combustion chamber is set because of the requirement that the peripheral ignition gaps 12 and 13 be attached and detached from above the cylinder head 1, respectively.

The arrangement relationship shown in FIG. 5 can be applied in the same manner when focusing on one side bank of the V-type engine.

Although the embodiment has been described above, the number of peripheral ignition gaps can be set to an appropriate number of 2 or 4 or more.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a simplified plan view of a combustion chamber portion.

FIG. 2 is a sectional view corresponding to line X2-X2 in FIG.

FIG. 3 is a sectional view corresponding to line X3-X3 in FIG.

FIG. 4 is a diagram showing a difference in heat generation mode between a peripheral ignition system and a central ignition system.

5 is a diagram showing an example of a case where the combustion chamber structure shown in FIG. 1 is arranged in series for multiple cylinders.

[Explanation of symbols]

1: Cylinder head 2: Combustion chamber 11-13: Peripheral ignition gap 22: Piston 23: Projection α: Ridge line r1 to r3: Distance between peripheral ignition gap and projection outer peripheral surface in the combustion chamber radial direction

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Riki Iname, 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Inventor, Yoshihiro Kiriki, 3-3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Corporation Within

Claims (4)

[Claims] 1. A plurality of peripheral ignition gaps are provided at the outer peripheral edge of the combustion chamber at intervals in the circumferential direction of the combustion chamber, and the piston top surface is configured to suppress the transfer of combustion flame to the center of the combustion chamber. A cylindrical protrusion is formed, and a distance in the combustion chamber radial direction between the plurality of peripheral ignition gaps and the center of the combustion chamber is set to be different for at least a part of the peripheral ignition gaps. A combustion chamber structure for an engine, wherein a center of the protrusion is offset from a center of the combustion chamber so that distances from the peripheral ignition gaps are substantially equal to each other. 2. The peripheral ignition gap according to claim 1, wherein each of the peripheral ignition gaps is attached to and held by a cylinder head. 3. The engine according to claim 2, wherein the engine is a multi-cylinder engine having a plurality of cylinders arranged in series in the crankshaft direction, and an imaginary line extending parallel to the crankshaft is provided for one combustion chamber. Two intake ports are formed in series in the crank axis direction on one side of the boundary, and two exhaust ports are formed in series in the crank axis direction on the other side of the virtual line as a boundary. A total of three ignition gaps, a first peripheral ignition gap and a second peripheral ignition gap, are provided for one combustion chamber, and the first peripheral ignition gap is located between two intake ports. The second ignition gap is located between one intake port and one exhaust port, and the third ignition gap is connected to the other intake port and the other exhaust port. Located between the second peripheral ignition The gap has a greater distance in the combustion chamber radial direction from the center of the combustion chamber than the third peripheral ignition gap, and the center of the protrusion is offset toward the second peripheral ignition gap side with respect to the center of the combustion chamber. thing. 4. The structure according to claim 3, wherein the shape of the combustion chamber is a Pentorf type having a ridgeline extending parallel to the crankshaft, and the ridgeline is the virtual line.