JP2021105355A - Internal combustion engine with auxiliary combustion chamber - Google Patents

Abstract

To improve reliability by preventing melting loss of an ignition plug, in an internal combustion engine in which a tip portion of the ignition plug is covered by an auxiliary combustion chamber.SOLUTION: An ignition plug 10 and an igniter 11 are disposed in a plug hole 9 in a manner of being partially fitted to each other. The ignition plug 10 has a screwed portion 12 screwed into a cylinder head 3, an upper overlap portion 13 entering the igniter 11, and a hexagonal portion 15 with which a wrench is engaged, and the part of the hexagonal portion 15 is an exposed portion. An outer cylindrical clearance 27 of the igniter 11 is divided into two ventilation passages by a longitudinal rib 29, and air is sent to one of the ventilation passages and exhausted from the other ventilation passage, so that heat received by the ignition plug 10 is radiated from the exposed portion 14. By radiating heat from the exposed portion 14 through the screwed portion 12, melting loss of the ignition plug 10 can be prevented even when a tip portion of the ignition plug 10 is exposed to a high temperature.SELECTED DRAWING: Figure 1

Description

The present invention relates to an internal combustion engine with an auxiliary combustion chamber.

In an internal combustion engine, it has been proposed to provide a sub-combustion chamber (sub-chamber) in the cylinder head. The sub-combustion chamber is provided in place of the spark plug, and the flame generated in the sub-combustion chamber is ejected into the main combustion chamber to ignite the main fuel (air-fuel mixture). Since the flame generated in the sub-combustion chamber is excellent in ignitability of the fuel, there is an advantage that the intake fuel can be reliably burned even if it is lean. Therefore, it is attracting attention as a promising technology for promoting exhaust gas screen.

Looking at the relationship between the sub-combustion chamber and the spark plug, for example, as disclosed in Patent Document 1, a structure in which an ignition plug is attached to a main body formed in the sub-combustion chamber and a structure disclosed in Patent Document 2 As shown above, there is a structure in which the electrodes of the spark plug are covered with an auxiliary combustion chamber.

Japanese Unexamined Patent Publication No. 2007-11536 Japanese Unexamined Patent Publication No. 2013-133717

In any case, since the tip of the spark plug provided with the electrode is exposed inside the sub-combustion chamber, the tip is exposed to a harsh thermal environment in the sub-combustion chamber, and therefore, the spark plug is melted. There was a danger of. Regarding this point, it is conceivable to manufacture the body of the spark plug with a special alloy having high heat resistance, but this has a problem that the cost increases significantly.

The present invention has been made to improve such a situation.

The internal combustion engine of the present invention is
"A sub-combustion chamber arranged in the cylinder head so as to be exposed to the main combustion chamber, an ignition plug arranged in a plug hole with the discharge electrode exposed inside the sub-combustion chamber, and a spark plug and a portion. It is equipped with an igniter and other ignition assisting devices that are arranged in the plug hole in a state of being fitted together.
The spark plug is exposed located between the screwed portion screwed into the cylinder head or the sub-combustion chamber, the upper polymerized portion that has entered the inside of the ignition assisting device, and the screwed portion and the upper polymerized portion. It has a part, and there is an annular space between the exposed part and the plug hole. "
It has a basic structure.

Then, in the basic configuration,
"A ventilation path communicating with the annular space is formed between the inner surface of the plug hole and the outer surface of the ignition assist device, and an air flow is imparted to the ventilation path and the annular space. An air supply means for cooling the exposed portion of the spark plug is connected. "
The configuration is added.

If there is a gap between the inner surface of the plug hole and the ignition assist device such as an igniter, this gap can be used as a ventilation path. If there is no gap, it is possible to form a vertically long ventilation groove in the plug hole. If there is enough space in the ignition assist device such as an igniter, it is possible to form a ventilation path (vent groove) on the outer peripheral surface of the ignition assist device. Of course, ventilation grooves may be formed at both the plug hole and the ignition assist device point.

In the present invention, by exposing the exposed portion of the spark plug to the air flow, the heat received from the sub-combustion chamber at the tip of the spark plug can be dissipated to the air flow. That is, the spark plug is an air-cooled type, which can prevent the tip of the spark plug from being excessively heated. Therefore, the body of the spark plug can be made of the same material as the conventional one, and the cost can be suppressed.

In other words, it is possible to realize a highly reliable internal combustion engine with an auxiliary combustion chamber that does not cause melting damage even if the spark plug is not manufactured of a heat-resistant special alloy, while keeping costs down. In addition, since it is not necessary to make major changes to the basic structure, for example, the conventional ignition assist device such as an igniter and the spark plug can be used as they are, and the number of changes can be reduced, resulting in flexibility. Are better.

When applied to a mode in which there is a gap between the inner surface of the plug hole and an ignition assisting device such as an igniter, and using this gap as a ventilation path, it is possible to reduce the labor of processing and the cost, and air. Since the flow rate of the air can be increased, it can also contribute to the improvement of cooling performance.

The present invention can also be applied to a type in which fuel is supplied to the sub-combustion chamber by a dedicated injector. In this case, since the injector can be cooled by the air flow, the injector that is sensitive to heat can be protected and the reliability can be improved.

It is a vertical cross-sectional view which looked at the 1st Embodiment from the direction of the crank axis. (A) is a sectional view taken along the line AA of FIG. 1, and FIGS. (B) to (E) are plan sectional views of another embodiment.

(1). First Embodiment Next, an embodiment of the present invention will be described with reference to the drawings. First, the first embodiment shown in FIGS. 1 and 2 (A) will be described. The internal combustion engine has a cylinder block 1 and a cylinder head 3 fixed to the upper surface thereof via a gasket 2 as basic elements, and the cylinder block 1 has a plurality of cylinder bores 4 arranged in the crank axis direction. It is formed.

On the other hand, the cylinder head 3 is formed with a conical recess 5 corresponding to the cylinder bore 4, and the main combustion chamber 6 is formed by the cylinder bore 4 of the cylinder block 1 and the recess 5 of the cylinder head 3. There is. Therefore, the cylinder head 3 is a pent roof type. As a matter of course, a piston (not shown) is slidably fitted in the cylinder bore 4.

Although not shown, the cylinder head 3 is formed with a pair of intake ports and a pair of exhaust ports on both sides of the crank axis line, corresponding to each recess 5. Needless to say, the intake port is opened and closed by the intake valve, and the exhaust port is opened and closed by the exhaust valve.

A sub-combustion chamber 7 exposed to the main combustion chamber 6 is arranged in a substantially central portion of the recess 5 of the cylinder head 3. The sub-combustion chamber 7 is formed in a hemispherical shape that opens upward, and a plurality of flame injection holes 8 are formed side by side in the circumferential direction. Further, the sub-combustion chamber 7 is inseparably fixed to the cylinder head 3 by means such as welding or press-fitting (it is also possible to form an upward cylinder portion and fix it to the cylinder head 3 by screwing. ).

A plug hole 9 concentric with the cylinder bore axis is formed in the cylinder head 3, and a spark plug 10 and an igniter 11 are arranged in the plug hole 9. The spark plug 10 has a screwing portion 12 having a male screw screwed into a female screw hole formed in the cylinder head 3, an upper polymerization portion 13 fitted to the igniter 11 from below, and an upper polymerization portion 13 and a screwing portion. It has an exposed portion 14 located between the exposed portion 14 and a hexagonal portion 15 into which a wrench is fitted is formed in the exposed portion 14. A center electrode 10a and a ground electrode 10b are provided at the tip of the screwed portion 12, and these electrodes 10a and 10b are covered with a sub-combustion chamber 7.

A head cover 17 is fixed to the upper surface of the cylinder head 3 with a large number of bolts, and a plug hole 9 is also formed in the head cover 17. The igniter 11 is an example of an ignition assist device, and incorporates an ignition coil, a control circuit, and the like. A tubular boss 18 for forming the plug hole 9 is formed in the head cover 17, and the lower end of the tubular boss 18 is sealed with the cylinder head 3 via a gasket 19.

Camshafts 20 and 21 for intake valves and exhaust valves are rotatably held in the cylinder head 3 via cam caps 23 fixed by bolts 22. Further, the cylinder head 3 is formed with two upper and lower cooling water jacket passages 24 and 25. The upper and lower cooling water jackets 24 and 25 are formed so as to surround the tubular portion in which the plug hole 9 is formed.

(2). Ventilation structure There is a tubular gap 27 between the plug hole 9 and the igniter 11, and there is also an annular space 28 between the plug hole 9 and the exposed portion 14 of the spark plug 10. There is. As is clearly shown in FIG. 2 (A), the igniter 11 (the casing constituting the igniter) is provided with a vertically long rib 29 that divides the tubular gap 27 into an intake side passage and an exhaust side passage over substantially the entire length. , The tubular gap 27 is divided into two ventilation passages.

The vertically long rib 29 is made of rubber, for example, and is attached to the outer peripheral surface of the igniter 11 by means such as adhesion, but it can also be integrally molded with the igniter 11. On the other hand, between the plug hole 9 and the igniter 11, there is a continuous annular space 28 over the entire circumference.

A head 30 having a diameter larger than that of the plug hole 9 is formed at the upper end of the igniter 11, but a ring shape is formed between the head 30 and the head cover 17 as a part of the air supply means described in claim. A joint plate 31 is interposed.

An air inflow port 32 and an air discharge port 33 are projected on the upper surface of the joint plate 31 so as to be located on both sides of the axis, and further, an air inflow port 32 is provided on the lower surface of the joint plate 31. An inflow relay passage 34 communicating with one part of the tubular gap 27 and an discharge relay passage 35 communicating with the air discharge port 33 and the other part of the tubular gap 27 are formed. In the embodiment, the air inflow port 32 is provided on the exhaust side and the air discharge port 33 is provided on the intake side, but these may be arranged in reverse.

Further, the tubular gap 27 may be divided into two spaces divided in the crank axis direction. In this case, the air inflow port 32 and the air discharge port 33 are aligned in the crank axis direction.

Air is supplied to the air inflow port 32 of the joint plate 31 from a blower (not shown) via a pipeline such as a tube. The air inflow port 32 may be connected to the suction port of the blower or may be left open to the atmosphere. Alternatively, the air inflow port 32 may be opened to the atmosphere and the air discharge port 33 may be connected to the suction port of the blower.

The blower also constitutes the air supply means described in the claims, but it is also possible to use the flow of intake air as the air supply means. That is, for example, an air take-out port and an air return port are provided between the air cleaner and the throttle valve in the intake passage so that the air take-out port is located on the downstream side, and the air take-out port is provided as air in the joint plate 31. The air return port can be connected to the air discharge port 33 of the joint plate 31 by connecting to the inflow port 32.

In the above configuration, as shown by an arrow in FIG. 1, air flows downward from the exhaust side portion of the tubular gap 27 on the outside of the igniter 11, passes through the annular space 28, and is outside the igniter 11. It flows to the intake side portion of the tubular gap 27 of the above, and is discharged from the air discharge port 33 of the joint plate 31. That is, an air flow is formed between the tubular gap 27 and the annular space 28.

On the other hand, since heat is trapped inside the sub-combustion chamber 7, the tip of the spark plug 10 continues to be exposed to high temperatures, but in the present embodiment, air always flows in the annular space 28, so that the spark plug 10 The heat received at the tip can be dissipated to the air flow at the location of the annular space 28 via the screwing portion 12. Therefore, even if the spark plug 10 is not manufactured of a heat-resistant special alloy, it is possible to prevent the tip of the spark plug 10 from being excessively heated and melted. As a result, the reliability of the internal combustion engine provided with the sub-combustion chamber 7 can be improved while suppressing the cost.

Although the joint plate 31 is used in the illustrated example, the head cover 17 has an inclined air inflow hole communicating with one side of the tubular gap 27 and an air discharge hole communicating with the other side of the tubular gap 27. It is also possible to form the above and connect a blower or the like to these.

(3). Other Embodiments Next, another embodiment shown in FIG. 2B and below will be described. In the second embodiment shown in FIG. 2B, in addition to the first embodiment, a portion of the tubular gap 27 that substantially overlaps the upper polymerization portion 13 of the spark plug 10 is provided in the igniter 11 with a vertically long ridge 11a. It is divided in the circumferential direction by. Therefore, in this embodiment, the portion of the tubular gap 27 that substantially overlaps the upper polymerization portion 13 of the spark plug 10 is divided into four areas divided in the circumferential direction.

In this second embodiment, since the vertically long ridges 11a also increase the heat dissipation from the igniter 11, the ratio of the heat of the upper polymerization portion 13 in the spark plug 10 to be dissipated through the igniter 11 can be increased. Therefore, the cooling performance of the spark plug 10 can be improved. Four or more vertically long ridges 11a may be formed.

In the third embodiment shown in FIG. 2C, a pair of vertically long inward ribs 36 are formed on the inner surface of the plug hole 9 as a means for dividing the tubular gap 27 into two flow paths. On the other hand, in the fourth embodiment shown in FIG. 2 (D), a pair of vertically long ventilation passages 37 are formed on the outer peripheral surface of the igniter 11 with an axial center in between, and air is supplied to one of the vertically long ventilation passages 37 and the other. It is configured to exhaust air from the vertically long air passage 37 of the above. As shown by the alternate long and short dash line, the vertically long air passage 37 may be formed on the inner surface of the plug hole 9 or may be formed on both the plug hole 9 and the igniter 11.

In the fifth embodiment shown in FIG. 2 (E), a pair of vertically long inward ribs 36 that divide the tubular gap 27 into two flow paths and air are provided at the upper cooling water jacket 24 of the plug hole 9. A large number of outward grooves 38 are formed to increase the contact area of the water. Further, at the portion of the vertically long inward rib 36, a vertical groove 39 opened toward the cooling water jacket 24 is formed on the outer surface of the meat portion where the plug hole 9 is formed.

In this embodiment, since heat exchange between the air passing through the tubular gap 27 and the cooling water flowing through the cooling water jacket 24 is vigorously performed, it can be said that the cooling performance of the spark plug 10 can be improved.

Although the illustrated embodiment has been described above, the invention of the present application can be embodied in various ways. For example, it is possible to improve the cooling performance of the igniter by forming a large number of vertically elongated ribs on the outer peripheral surface of the igniter. In addition, when an injector is provided, consideration should be given so that air flow is also generated in the space surrounding the injector. As an ignition assist device, a direct ignition or the like can also be used.

The present invention can be embodied in an internal combustion engine with an auxiliary combustion chamber. Therefore, it can be used industrially.

1 Cylinder block 3 Cylinder head 6 Main combustion chamber 7 Sub-combustion chamber 8 Flame injection hole 9 Plug hole 10 Spark plug 11 Igniter as an example of ignition assist device 12 Screwed part 13 Upper overlapping part 14 Exposed part 15 Hexagon part 17 Head cover 27 Cylinder gaps that make up the air passage 28 Circular space 37 Vertical air passage 30 Igniter head 31 Joint plate 32 Air inlet 33 Air outlet 34 Inflow relay passage 35 Discharge relay passage

Claims (1)

A sub-combustion chamber arranged in the cylinder head so as to be exposed to the main combustion chamber, an ignition plug arranged in a plug hole with the discharge electrode exposed inside the sub-combustion chamber, and a spark plug partially. It is equipped with an igniter and other ignition assisting devices that are placed in the plug hole in a state of being fitted to the plug hole.
The spark plug is exposed located between the screwed portion screwed into the cylinder head or the sub-combustion chamber, the upper polymerized portion that has entered the inside of the ignition assisting device, and the screwed portion and the upper polymerized portion. It has a portion, and the exposed portion and the plug hole have an annular space.
A ventilation path communicating with the annular space is formed between the inner surface of the plug hole and the outer surface of the ignition assist device, and an air flow is imparted to the ventilation path and the annular space. An air supply means for cooling the exposed portion of the spark plug is connected.
Internal combustion engine with auxiliary combustion chamber.

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