JP3037515B2 - Two-point ignition engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-point ignition engine.

[0002]

2. Description of the Related Art Generally, an engine is required to have good fuel economy in a low load region where a high output is not required. As a method for improving fuel efficiency, a method of leaning an air-fuel mixture, that is, a so-called lean burn method, has been frequently used. However, in general, in a gasoline engine, when the mixture is lean, there is a problem that the ignitability is extremely deteriorated and misfiring frequently occurs. Therefore, instead of distributing the fuel uniformly in the combustion chamber, the mixture is stratified by distributing a large amount of fuel around the spark plug, and the ignitability is improved despite the leanness of the entire combustion chamber. Engines have been proposed that are not reduced.

[0003] Specifically, one cylinder has first and second two
Two intake ports, and open the first intake port in the circumferential direction of the cylinder.
(Swirl generation port) to generate (circumferential eddy current)
An engine has been proposed in which a second intake port is used as a normal intake port and an opening / closing valve is provided in the ordinary intake port (for example, Japanese Patent Laid-Open No.
9-54532). In a conventional engine having such a swirl generation port, usually, a spark plug is disposed at a center portion of a cylinder bore, while a fuel injection valve is provided to face a first intake port or directly to a combustion chamber. The injection valve is arranged so that its injection center axis is directed toward the spark plug. In such an engine, in the low load region, the on-off valve is closed, and air is supplied only from the swirl generation port into the combustion chamber to generate strong swirl, while fuel is injected from the fuel injection valve toward the spark plug, The fuel is retained in a narrow area around the spark plug surrounded by the swirl walls.

[0004]

In this case, the fuel injected from the fuel injection valve first penetrates the wall of the swirl in front and reaches around the spark plug. However, in this case, if the swirl is too strong, the direction of the fuel injected from the fuel injection valve is changed by the swirl when penetrating the wall of the swirl, and the fuel does not collect around the spark plug. Conversely, if the swirl is too weak, the fuel injected from the fuel injection valve passes through the spark plug and reaches and adheres to the combustion chamber wall on the other side, so that emission may deteriorate or knocking may occur.

[0005] Therefore, in an engine in which stratification is achieved by swirl, it is very difficult to form a rich mixture layer around the spark plug. Therefore, in an engine with a swirl generation port,
There has been proposed a two-point ignition engine in which one cylinder is provided with two spark plugs to improve the ignitability (for example, see Japanese Patent Publication No. 56-10449). However, even if two spark plugs are provided in this way, it is difficult to arrange them well at a position where fuel easily collects.

Accordingly, a three-point ignition engine in which three ignition plugs are arranged in one cylinder has been proposed (for example, see Japanese Utility Model Laid-Open No. 60-43128). However, in such a three-point ignition engine, although the ignitability is improved, there is a problem that noise or vibration generated from the engine is increased, and a problem is that power consumption is increased. Furthermore, since the space around the engine is limited, there is a problem that the layout of the spark plug is difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and stratifies fuel by concentrating fuel around a spark plug in a low load region without deteriorating emission or knocking. It is an object of the present invention to provide a two-point ignition engine that can promote fuel economy and improve fuel efficiency.

[0008]

According to a first aspect of the present invention, two ignition plugs are provided for each cylinder, and one of the ignition plugs is disposed substantially at the center of a cylinder bore. And two independent intake ports are provided for each cylinder. One of the intake ports is a swirl generation port for generating swirl in the combustion chamber, and the other intake port is tumbled into the combustion chamber. In a two-point ignition engine that is a tumble generation port that generates a fuel injection valve, a fuel injection valve is provided facing the swirl generation port, and the fuel injection valve has an injection center axis disposed substantially in the center of the cylinder bore. The other ignition plug is disposed so as to be oriented in the electrode direction of the ignition plug, and the tumble generation port opening and the tumble generation port opening are provided. It is arranged between adjacent exhaust port openings, and when at least intake air is supplied to the combustion chamber from both intake ports, the air-fuel mixture in the combustion chamber is ignited by both ignition plugs. To provide a two-point ignition engine.

According to a second aspect, in the two-point ignition engine according to the first aspect, the swirl generation port and the tumble generation port are connected from the swirl generation port side when intake air is supplied to the combustion chamber from both ports. A two-point ignition engine is provided which is formed so as to generate an oblique swirl toward a tumble generation port side.

A third invention provides a two-point ignition engine according to the first or second invention, wherein a mask for generating a squish flow is provided only on the exhaust side. I do.

According to a fourth aspect of the present invention, in the two-point ignition engine according to the first or second aspect, the tumble generating port is provided with an opening / closing valve that opens more as the engine load increases. A two-point ignition engine is provided.

According to a fifth aspect of the invention, there is provided a two-point ignition engine according to the first or second aspect, wherein boss portions of plug holes of both ignition plugs are connected to each other. I do.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.
As shown in FIGS. 1 and 2, in the engine CE,
A cylinder head 2 is fastened to the upper end of the cylinder block 1. A cylinder 3 (cylinder bore) is formed in the cylinder block 1. Here, a combustion chamber 4 is defined by a lower surface of the cylinder head 2, an inner peripheral surface of the cylinder 3, and an upper end surface of a piston (not shown).

The intake-side half of the combustion chamber 4 (FIGS. 1 and 2)
The first and second intake ports 5 and 6 are open on the left side (in FIG. 1), and the first and second exhaust ports 7 and 8 are open on the exhaust side half (the right side in FIGS. 1 and 2). In addition, a first spark plug 9 is disposed substantially at the center of the combustion chamber 4 (cylinder 3). Further, an opening of the second intake port 6 to the combustion chamber 4 (hereinafter, referred to as an opening)
Between the opening of the second intake port 8) and the opening of the second exhaust port 8 to the combustion chamber 4 (hereinafter referred to as the second exhaust port opening), the combustion chamber 4 (cylinder 3) A second spark plug 10 is provided in the peripheral portion of.

The fuel injection valve 11 faces the first intake port 5.
The injection center axis L of the fuel injection valve 11 is directed to the first spark plug 9 arranged at the center of the combustion chamber. The second intake port 6 has an on-off valve 1 for opening and closing it.
2 are provided. Further, a mask 13 (squish mask) is provided on the ceiling surface on the exhaust side of the combustion chamber 4.

The specific structure of each part will be described below. The first intake port 5 is a swirl generation port, and extends substantially in the engine width direction (horizontal direction in FIGS. 1 and 2) in plan view, but has a cylinder near the opening to the combustion chamber 4. It curves toward the outer periphery (opposite to the second intake port 6), and opens into the combustion chamber 4 while pointing substantially in the tangential direction of the cylinder (tangential port). In addition, from an elevational point of view, the first intake port 5 has its central axis lined with the cylinder head 2.
And the mating surface (usually a horizontal plane) of the cylinder block 1 and the combustion chamber 4
It is open to. For this reason, the air flowing into the combustion chamber 4 from the first intake port 5 generates a swirl as shown by an arrow X, that is, a circumferential vortex that turns counterclockwise as viewed from above. The swirl may be generated using the first intake port 5 as a helical port.

The second intake port 6 is a tumble generation port.
In the vicinity of the opening to the combustion chamber 4, it slightly opens toward the cylinder center (toward the first intake port 5) and opens into the combustion chamber 4 near the opening to the combustion chamber 4. Further, from an elevational point of view, the angle of incidence (incident angle) between the center axis of the second intake port 6 and the mating surface of the cylinder head 2 and the cylinder block 1 is made relatively large, so that the combustion chamber 4 is open. Therefore, the air flowing into the combustion chamber 4 from the second intake port 6 generates a tumble, that is, a vortex (longitudinal vortex) in the cylinder axis direction in the combustion chamber 4. Since the second intake port 6 is opened toward the cylinder chamber with an inclination toward the center of the cylinder, the generation of reverse swirl that prevents the swirl generated by the first intake port 5 is prevented.

The fuel injection valve 11 is arranged such that the injection center axis L is directed to the vicinity of the center of the combustion chamber, that is, to the vicinity of the electrode (spark discharge portion) of the first spark plug 9. For this reason, when fuel is injected from the fuel injection valve 11, the fuel is basically largely distributed near the center of the combustion chamber, that is, around the front end of the central spark plug 9, and thus, basically, the fuel is basically distributed around the center of the combustion chamber. A mixture richer than the surroundings of the combustion chamber is formed on the side. Therefore, in the low load region where strong swirl is generated, the mixture is stratified,
Lean burn is being performed.

An on-off valve 12 for opening and closing the second intake port 6
Is set to be closed when the load is equal to or less than a predetermined load, that is, in a predetermined low load region, and to be increased with an increase in the engine load on a higher load side. Here, when the on-off valve 12 is closed, the combustion chamber 4
Since air is supplied only from the first intake port 5 which is a swirl generation port, a strong swirl is generated in the combustion chamber 4. On the other hand, when the on-off valve 12 is opened, the air flowing into the combustion chamber 4 from the first intake port 5 generates swirl in the combustion chamber 4, and the air flowing into the combustion chamber 4 from the second intake port 6 is: A tumble is generated in the combustion chamber 4. Therefore, the swirl and the tumble merge in the combustion chamber 4 to generate an oblique swirl from the first intake port opening to the second exhaust port opening. Here, as the opening of the on-off valve 12 increases, the diagonal swirl approaches the original tumble.

The mask 13 generates a squish flow when a piston (not shown) rises and approaches a top dead center. The squish flow causes the air-fuel mixture to flow through the first and second spark plugs 9 and 10. Extruded in the direction. As a result, an air-fuel mixture is collected around the first and second spark plugs 9 and 10,
At low load, stratification is promoted. In the exhaust stroke, the scavenging property of the exhaust gas is enhanced by the mask 13, and the exhaust gas is smoothly exhausted as shown by the arrow Y. The mask 13 is provided only on the exhaust side.

As shown in FIG. 3, a plug hole boss portion 16 for the first spark plug 9 is provided on the cylinder head 2.
A plug hole boss portion 17 for the second spark plug 10 is provided, and both plug hole bosses 16 and 17 are connected to each other by a connecting portion 18 to be integrated. The reason why the two plug hole bosses 16 and 17 are connected in this way is to increase the heat radiation area of the plug hole bosses 16 and 17 and promote cooling of the ignition plugs 9 and 10. Both the plug hole bosses 16 and 17 or the connecting portion 18 are cooled by the cooling water supplied from the cooling water passage 20, but since the connecting portion 18 is formed, the cooling water does not stagnate and the ignition plugs 9 and The cooling of 10 is further promoted.

In the two-point ignition engine CE having such a configuration, in a predetermined low load range, the on-off valve 12 is fully closed, and air is supplied to the combustion chamber 4 only from the first intake port 5. A strong swirl is generated as indicated by arrow X. At this time, fuel is injected from the fuel injection valve 11 in the direction of the first spark plug 9 disposed in the center of the combustion chamber.
Therefore, a rich air-fuel mixture layer is basically formed around the first spark plug 9, stratification is promoted, and the lean burn limit (lean burn limit) is improved. However, when the swirl is very strong, the fuel injected by the influence of the swirl changes its traveling direction in the counterclockwise direction, not around the first spark plug 9 but in the region A in FIG.
Many gather in. Here, the region A where the rich air-fuel mixture is collected exists on the side of the second exhaust port opening or the side of the second intake port opening rather than around the ignition plug 9. Therefore, the air-fuel mixture in the region A cannot be sufficiently ignited by the first spark plug 9 alone. However, in the present embodiment, the second spark plug 10 is disposed between the second intake port opening and the second exhaust port opening, and the second spark plug 10 is in the region A. The first
The spark plug 9 is also located in the area A although not at the center. For this reason, the mixture in the region A is ignited by the first and second ignition plugs 9 and 10. Therefore, even in the case where the region A where the air-fuel mixture is concentrated is deviated from the center of the combustion chamber, the ignitability and the flammability are ensured, so that the lean burn limit (lean combustion limit) is further improved, and the fuel efficiency is improved. Enhanced.

In a predetermined high load region, the on-off valve 12 is opened with an increase in the engine load, and the first and the second
Air is supplied from the second intake ports 5, 6, and the swirl and the tumble merge to generate an oblique swirl. In this case, basically, the filling efficiency and the combustibility are enhanced by the oblique swirl, and the engine output is enhanced. Further, in this case, the air-fuel mixture is widely distributed in the combustion chamber 4, and the rich air-fuel mixture is concentrated on the outer peripheral side of the combustion chamber. However, since the second spark plug 10 is arranged in the periphery of the combustion chamber 4, the rich air-fuel mixture is reliably ignited by the second spark plug 10 in this case, and the emission performance or the knocking resistance is enhanced. Can be

The swirl is weak in a light load region or the like, so that the fuel injected from the fuel injection valve 11 has a relatively high penetration force with respect to the swirl, and the fuel reaches the wall on the other side of the combustion chamber 4 and When the fuel adheres to the part, the fuel adhered to the wall is carried by the swirl counterclockwise along the peripheral wall of the combustion chamber 4. That is, the fuel is supplied to a portion of the periphery of the combustion chamber 2 from the second exhaust port opening to the second intake port opening, and further to an end between the first intake port opening and the second intake port opening. It is carried to the gas zone, where a rich mixture is formed.
Such a rich mixture. It is difficult to ignite with a spark plug located in the center of the combustion chamber. However, in the present embodiment, the second exhaust port opening and the second
Since the second spark plug 10 is provided between the intake port openings, the rich air-fuel mixture is supplied to the second spark plug 1
Since the ignition and the combustion are reliably performed by 0, the emission performance (HC) is enhanced and the occurrence of knocking is prevented.

In the engine CE, the first and second spark plugs 9 and 10 are, in principle, always igniting the air-fuel mixture irrespective of the operation state. However, the purpose is to reduce the electric load. Therefore, when it is necessary to perform one-point ignition in a medium / high load region, it is preferable that the first ignition plug 9 ignites. In this way, a decrease in the combustion speed of the air-fuel mixture is prevented, and the heat load on the combustion chamber 4 or the cylinder 2 is reduced.

The ignition timing of the first and second spark plugs 9 and 10 is the same as the ignition timing of the second spark plug 10.
It is preferable that the ignition timing of the ignition plug 9 is not delayed. In this way, the flame can be propagated to the end gas zone at an early stage, the emission performance can be improved, and the occurrence of knocking can be prevented.

When the on-off valve 12 is closed, the lift of an intake valve (not shown) for opening and closing the second intake port 6
(Valve opening) is preferably completed by the bottom dead center of the intake. By doing so, it is possible to reduce the inflow and outflow of the air-fuel mixture into and from the dead volume downstream of the on-off valve 12, and to reduce the accumulation of deposits.

As described above, according to the present embodiment, stratification is promoted in the low load region, and even when the rich mixture layer deviates from the center of the combustion chamber due to the swirl, the rich mixture remains in the second mixture. The ignition is reliably performed by the ignition plug 10, and the emission performance or the knocking resistance is enhanced. In addition, at high load, the filling efficiency or uniform combustion is enhanced by the oblique swirl, and the engine output is enhanced.

[0029]

According to the first aspect of the present invention, in the low load region, swirl is generated and fuel is injected from the fuel injection valve in the direction of the spark plug disposed in the center of the combustion chamber. Thus, stratification around the spark plug is promoted, and fuel efficiency is enhanced. In the high load region, the engine output is increased by tumble. Further, another spark plug is disposed in a region between the tumble generation port opening and the exhaust port opening adjacent thereto, where a rich air-fuel mixture is likely to be formed due to the influence of swirl. The ignitability and combustibility of the mixture are enhanced, and the emission performance and knocking resistance are enhanced.

According to the second aspect, basically the same operation and effect as those of the first aspect can be obtained. Further, in a high load region, the engine output is increased by the oblique swirl.
Further, another ignition plug is disposed between the tumble generation port opening and the exhaust port opening adjacent thereto, where a rich mixture is easily formed by the oblique swirl. The ignitability and combustibility are enhanced, and the emission performance and knocking resistance are enhanced.

According to the third aspect, basically, the same operation and effect as those of the first or second aspect can be obtained. further,
Since the air-fuel mixture is extruded in the direction of both spark plugs by the mask, stratification is promoted. Further, the scavenging property of the exhaust gas is improved.

According to the fourth aspect, basically the same functions and effects as those of the first or second aspect can be obtained. further,
Since the on-off valve is gradually opened according to the increase in the engine load, the lean limit at the time of medium load can be improved.

According to the fifth aspect, basically the same operations and effects as those of the first aspect are obtained. Further, since the plug hole boss portions of both spark plugs are connected, the heat dissipation area of the plug hole boss increases, and the cooling performance of the spark plug is enhanced.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view around a cylinder of a two-point ignition engine according to the present invention.

FIG. 2 is an elevational sectional explanatory view around an intake / exhaust port of the engine shown in FIG. 1;

FIG. 3 is a partially sectional plan view of the cylinder head of the engine shown in FIG. 1 around a plug hole boss;

[Explanation of symbols]

 CE engine 3 cylinder 4 combustion chamber 5, 6 first and second intake ports 9, 10 first and second spark plugs 11 fuel injection valve 12 on-off valve 13 mask 16 and 17 plug holes Boss 18 ... Connecting part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02D 41/04 310 F02D 41/04 310C F02M 69/00 360 F02M 69/00 360B 360C F02P 15/08 301 F02P 15/08 301E 302 JP-A-4-81577 (JP, A) JP-A-3-23314 (JP, A) JP-A-54-28917 (JP, A) JP-A-62-175248 (JP, A) JP-A-2-75718 (JP, A) JP-A-59-54732 (JP, A) JP-A-56-175519 (JP, U) JP-A-60-43128 (JP, U) (58) (Int.Cl. ⁷ , DB name) F02B 17/00 F02B 23/08 F02B 31/02 F02D 41/04 F02M 69/00 F02P 15/08

Claims (5)

(57) [Claims] 1. Two ignition plugs are provided for each cylinder, one ignition plug is disposed at a substantially central portion of a cylinder bore, and two independent intake ports are provided for each cylinder. In a two-point ignition engine, one of the intake ports is a swirl generation port for generating a swirl in the combustion chamber and the other intake port is a tumble generation port for generating a tumble in the combustion chamber. A fuel injection valve is provided facing the port, and the fuel injection valve is arranged so that an injection center axis thereof is directed to an electrode direction of the ignition plug disposed substantially at the center of the cylinder bore. Is disposed between the tumble generation port opening and the exhaust port opening adjacent to the tumble generation port opening, at least A two-point ignition engine characterized in that when intake air is supplied from both intake ports to the combustion chamber, the air-fuel mixture in the combustion chamber is ignited by both ignition plugs. 2. The two-point ignition engine according to claim 1, wherein the swirl generation port and the tumble generation port are connected to each other when the intake air is supplied to the combustion chamber from both ports. A two-point ignition engine characterized in that it is formed so as to generate an oblique swirl toward the side. 3. The method according to claim 1 or 2, wherein
A two-point ignition engine, wherein a mask for generating a squish flow is provided only on the exhaust side. 4. The method according to claim 1 or 2, wherein
2. A two-point ignition engine according to claim 1, wherein the tumble generating port is provided with an opening / closing valve that opens more as the engine load increases. 5. The method according to claim 1 or 2, wherein
A two-point ignition engine, wherein the bosses of the plug holes of both spark plugs are connected to each other.