JP3202350B2 - 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 As the shape of a combustion chamber of an engine, engines employing a pentle-type combustion chamber are increasing from the viewpoint of increasing the number of intake and exhaust valves. In this pentle-type combustion chamber, the inner surface of the cylinder head constituting the upper surface of the combustion chamber is
It has a pair of sloping surfaces, each of which is sloping at a ridge line extending substantially parallel to the cylinder diameter direction. One of the sloping surfaces has an intake port opened, and the other has an exhaust port opened. You.

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 has
A new combustion type engine with peripheral ignition has been developed.
This is because a plurality of ignition gaps (peripheral ignition gaps) are arranged on the outer peripheral edge of the combustion chamber at intervals in the peripheral direction of the combustion chamber, and the flame ignited in each peripheral ignition gap firstly extends in the peripheral direction of the combustion chamber. At the center of the combustion chamber. As a result, while reducing HC and CO which are likely to be generated around the combustion chamber, rapid combustion is suppressed and NOx is also reduced (Japanese Patent Laid-Open No. 3-28).
No. 6185).

In order to obtain the effect of the peripheral ignition system more sufficiently, a columnar projection is formed on the top surface of the piston.
This is more preferable in suppressing the flame from going to the center of the combustion chamber.

[0005]

In the case of an engine of a peripheral ignition system in which a cylindrical projection is formed on the upper surface of a piston and the combustion chamber is a pen-tooth type, the propagation of the flame in the circumferential direction of the combustion chamber is prevented. It has been found that this may not be successful in some cases.

[0006] To explain this point in detail, the flame ignited by the peripheral ignition gap is a side surface of a cylindrical projection formed on the upper surface of the piston (a surface extending in the cylinder axis direction and extending 360 degrees in the circumferential direction of the combustion chamber). And the inner surface of the cylinder head and the upper surface of the piston (the surface located at the height of the lower end of the projection and extending in the direction orthogonal to the cylinder axis). It will be transmitted as a flame transmission passage.

[0007] However, due to the shape of the pen-torff type combustion chamber, the space portion becomes narrow near the skirt of the inclined surface of the inner surface of the cylinder head. That is, the effective cross-sectional area of the space is large near the longitudinal end of the ridge line in the Penthol-type combustion chamber and small near the end in the direction perpendicular to the ridge line. In such a space portion where the effective area is small, the flame propagation is slowed down, and the effect of peripheral ignition is reduced.

On the other hand, when adjacent flames attempt to collide (coincide) in the circumferential direction of the combustion chamber, immediately before the collision, the pressure between the adjacent flames becomes extremely high, and the effect of preventing the collision of the flames is obtained. Will be performed. Then, even if the collision of the flame is performed early in a certain portion (for example, a portion where the air-fuel ratio is partially rich or the amount of residual exhaust gas is small), a situation occurs in which the flame does not yet collide in another portion, Such a delay in the collision of the flame in the circumferential direction of the combustion chamber reduces the effect of the peripheral ignition.

Accordingly, an object of the present invention is to make it possible to more quickly propagate a flame in the circumferential direction of a combustion chamber in a pentograph type combustion chamber and to further improve the effect of the peripheral ignition system. To provide a combustion chamber structure of an engine.

[0010]

In order to achieve the above-mentioned object, the present invention has the following constitution. That is, in an engine in which the shape of the combustion chamber is a pen-tower type engine having a pair of inclined surfaces each of which inclines with a ridgeline in which the inner surface of the cylinder head constituting the upper surface of the combustion chamber extends substantially parallel to the cylinder diameter direction as a boundary, On the periphery,
A plurality of peripheral ignition gaps are arranged at intervals in the circumferential direction of the combustion chamber, and a long cylindrical projection having a major axis in the direction in which the ridge extends is formed on the top surface of the piston. is there.

At the position where the flames ignited in the respective peripheral ignition gaps are about to collide with each other in the circumferential direction of the combustion chamber, a cutout is formed in the projection so as to increase the interval between the flame and the inner surface of the cylinder head. Can be.

The notch may be provided only at a position where the collision of the flame in the circumferential direction of the combustion chamber is easily delayed.

[0013]

According to the present invention, the effective cross-sectional area of the space which becomes the flame propagation path in the circumferential direction of the combustion chamber is set to be sufficiently large over the entire length in the circumferential direction of the combustion chamber, and the exhaust gas by the peripheral ignition system The effect of reducing harmful components can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a view of the cylinder head 1 as viewed from the inner surface side. The inner surface of the cylinder head 1 is set to have a shape that constitutes a pentle-shaped combustion chamber 2. That is, as is clear from FIGS. 2 and 3 as well,
The inner surface of the cylinder head 1 has a ridge line α extending substantially in the center of the combustion chamber 2 and extending parallel to the cylinder diameter direction, and has a pair of inclined surfaces 1a and 1b bordering the ridge line α. Of course, each of the inclined surfaces 1a, 1b is gradually inclined downward as the distance from the ridge line α increases (see FIG. 3).

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

The cylinder head 1 is provided with a total of three peripheral ignition gaps (ignition plugs) 7 to 9 at the outer peripheral edge of the combustion chamber 2 at intervals in the circumferential direction of the combustion chamber. The peripheral ignition gap 7 is located approximately halfway between the two intake ports 3 and 4. The peripheral ignition gap 8 is
It is located near the exhaust port 5 between the intake port 3 and the exhaust port 5. The peripheral ignition gap 9 is located between the intake port 4 and the exhaust port 6 and is connected to the exhaust port 6.
It is located near.

Further, the cylinder head 1 is provided with a central ignition gap 10 at a central position of the combustion chamber. Of the above ignition gaps 7 to 10, only the peripheral ignition gaps 7 to 9 are ignited and the central ignition gap 10 is stopped at a low load when harmful components in the exhaust gas pose a problem. When the load is high, at least the central ignition gap 10 is ignited, but the peripheral ignition gaps 7 to 9 may be either ignited or stopped.

2 and 3, reference numeral 11 denotes a cylinder block, and reference numeral 12 denotes a piston. On the top surface of the piston 12, a projection 13 is formed. This projection 13
As shown in FIG. 4, is formed to have a long columnar shape (elliptical column shape) with the ridge line α as a major axis. That is, when viewed on a plane orthogonal to the cylinder axis, the projection 13 is formed to be an ellipse (ellipse) in the present invention.

For comparison, the protrusion 1 in FIGS.
3 is indicated by a dashed-dotted line β, and FIG. 5 is indicated by a solid line in FIG. 5 when the projection 13 is formed into a columnar shape. The shape of β shown by becomes clearer.

By setting the shape of the projection 13 as described above, as is apparent from FIGS.
a, Flame transmission passage T in the circumferential direction of the combustion chamber near the bottom of 1b
1 (FIG. 3) is a flame transmission passage T2 near the end of the ridgeline α.
It is enlarged to a large one that has almost the same effective area as that of FIG. Incidentally, as is apparent from FIG. 3, when the protrusion 13 is formed in a columnar shape, the effective sectional area of a portion corresponding to the passage T1 is small.

As described above, since the effective sectional area of the portion corresponding to the passage T1 is ensured to be large, the flame ignited by the peripheral ignition gaps 7 to 9 at a low load is smoothed in the circumferential direction of the combustion chamber. This makes it possible to hasten the collision of adjacent flames in the circumferential direction of the combustion chamber.
When the load is low, for example, by closing one of the intake ports by a shutter valve or the like, a swirl of the intake air is generated in the combustion chamber 2 to further promote the flame propagation in the circumferential direction of the combustion chamber. Can also.

FIGS. 6 and 7 show a reference example. The same reference numerals are given to the same components as those in the above-described embodiment, and the description thereof will be omitted. In the present reference example, the projection 23 formed on the top surface of the piston 12 is formed in a columnar shape as a whole. And, on the upper edge of the projection 23, the inclined surface 1a,
A pair of inclined surfaces 23a and 23b extending substantially parallel to the inclined surfaces 1a and 1b are formed to prevent interference with the inclined surfaces 1a and 1b.

A notch 24 is formed at a predetermined position on the peripheral edge of the upper end of the projection 23 (in the drawing, a portion corresponding to the notch 24 is hatched in order to show the position and shape of the notch 24 as clearly as possible. Is attached). This notch 24
In the embodiment, there is a pair, and the formation positions are set as follows.

First, in FIG. 6, each of the peripheral ignition gaps 7 to
The flame ignited by 9 is propagated in the circumferential direction of the combustion chamber,
The state just before the flame grows over the entire length in the circumferential direction of the combustion chamber is shown. However, FIG. 6 shows a growth state of the flame when the notch 24 does not exist.

The swirl of the intake air is generated in the counterclockwise direction in the figure, and the flame extending in the swirl direction from the peripheral ignition gap 7 and the flame extending in the anti-swirl direction from the peripheral ignition gap 8 have already been formed. Collision. On the other hand, the flame has not yet collided between the peripheral ignition gaps 7 and 9 (the last burned portion of this portion is indicated by reference numeral M1). Similarly, the flame is still between the peripheral ignition gaps 8 and 9. Does not collide (the last burned portion of this portion is indicated by reference numeral M2).

The notch 24 is formed between the above-described end-burning parts M1 and M
2 is formed corresponding to the position. This gives M
The pressure from the flame which is about to collide in each of the portions 1 and M2 escapes upward through the notch 24, that is, in the direction toward the center of the combustion chamber, and the flame is also immediately collided in the portions M1 and M2. That is, the flames also collide in the M1 and M2 portions at substantially the same time as the flames collide between the peripheral ignition gaps 7 and 8.

Although the flame easily escapes toward the center of the combustion chamber through the notch 24, the flame has a large flame area toward the center of the combustion chamber through the notch 24 before the flames collide with each other in the circumferential direction of the combustion chamber. Never run away.

Here, the positions of M1 and M2 as positions where the cutouts 24 are provided are determined by various factors which affect the ease of flame propagation in the circumferential direction of the combustion chamber, for example, uneven distribution of fuel, residual exhaust gas. The position of the notch 24 is determined after the portions that become M1 and M2 are specified in advance by an experiment.

Although the embodiment has been described above, the number of peripheral ignition gaps can be appropriately selected from two or more. 6 and 7 in addition to the configuration shown in FIGS.
May be combined with each other. Of course, the number of intake ports and the number of exhaust ports are arbitrary. For example, three intake ports and two exhaust ports can be used. Further, the peripheral ignition gaps 7 to 9 can be appropriately selected as the attachment member such as being held by an ignition plug holding member interposed between the cylinder head 1 and the cylinder block 11. Furthermore, the ridge line α can be located at a position far away from the center of the combustion chamber (particularly when the area of the intake port is increased).

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, and is a view of a cylinder head viewed from an inner surface side thereof.

FIG. 2 is a sectional view taken along line X2-X2 in FIG.

FIG. 3 is a sectional view corresponding to line X3-X3 in FIG. 1;

FIG. 4 is a diagram showing a protrusion formed on the piston top surface together with a comparative example, as viewed from above the piston.

FIG. 5 is a view corresponding to FIG. 4, showing a comparative example in which a columnar projection is formed on the top surface of the piston.

FIG. 6 is a view illustrating a reference example and explaining a formation position of a notch portion when the piston is viewed from above;

FIG. 7 is a diagram when FIG. 6 is viewed from an arrow Y direction.

[Explanation of symbols]

 1: Cylinder head 2: Combustion chamber 1a, 1b: Inclined surface 7-9: Peripheral ignition gap 12: Piston 13: Projection α: Ridge T1, T2: Flame transmission passage

Continued on the front page (72) Inventor Noriyuki Ota 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside (72) Inventor Hiroyuki Yamamoto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Corporation (56) References JP-A-4-183925 (JP, A) JP-A-52-151407 (JP, A) JP-A-3-286185 (JP, A) Japanese Utility Model Publication No. 56-175519 (JP, U) 54-31712 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02B 23/08 F02P 15/02-15/08 F02F 3/28

Claims (1)

(57) [Claims] 1. An engine in which the shape of a combustion chamber is a pen-tower type engine having a pair of inclined surfaces each of which inclines at a ridge line where an inner surface of a cylinder head constituting an upper surface of the combustion chamber extends substantially parallel to a cylinder diameter direction. A plurality of peripheral ignition gaps are arranged on the outer peripheral edge of the combustion chamber at intervals in the circumferential direction of the combustion chamber, and an elongated columnar projection having a major axis extending in the direction in which the ridge extends is formed on the top surface of the piston. A combustion chamber structure for an engine.