JP7306924B2 - Internal combustion engine with auxiliary combustion chamber - Google Patents

Description

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

An internal combustion engine with an auxiliary combustion chamber is widely known, for example, from Patent Document 1 and the like. A sub-combustion chamber of an internal combustion engine is provided in place of a spark plug, and the flame generated in the sub-combustion chamber is ejected into the main combustion chamber to ignite the fuel. Since the flame generated in the sub-combustion chamber has excellent fuel ignitability, there is an advantage that even if the intake fuel is lean, it can be reliably burned. Therefore, it is attracting attention as a promising technology for cleaning exhaust gas.

Japanese Patent Publication No. 59-36089

As mentioned above, the internal combustion engine with the auxiliary combustion chamber has excellent ignitability to the fuel in the main combustion chamber, but the flame ejection hole formed in the torch is thin with an inner diameter of about 1.5 mm, for example, so scavenging is insufficient. There is a problem that the combustion in the sub-combustion chamber tends to be insufficient when the fuel is sufficient.

There are two methods of supplying fuel to the sub-combustion chamber: one is to install a dedicated fuel injector in the sub-combustion chamber, and the other is to take in the intake air (mixture) jetted from the intake port into the main combustion chamber into the sub-combustion chamber. However, in the latter case, if the scavenging is insufficient, the introduction of the intake air into the sub-combustion chamber is insufficient.

An object of the present invention is to improve such a situation.

The internal combustion engine of the present invention is
"The cylinder head and cylinder block form a main combustion chamber with open intake and exhaust ports , and the intake air jetted from the intake port generates a tumble flow in the main combustion chamber. ,
Further, the cylinder head is provided with an auxiliary combustion chamber having a torch exposed to the main combustion chamber, and the torch is formed with a flame ejection hole.”
It has a basic configuration.

And in the above basic configuration,
"The sub-combustion chamber is provided with a spark plug and is arranged at a position on the exhaust side or the intake side across the center of the main combustion chamber and at a position where the torch is exposed to the tumble flow. A first flame ejection hole that faces only the center of the main combustion chamber and faces the tumble flow, and a pair of second flame ejection holes that open in a direction crossing the tumble flow are formed. and the first flame ejection hole is formed to have a larger diameter than the second flame ejection hole."
configuration is added.

The tumble flow proceeds straight from the intake port, changes direction downward by the cylinder bore, and then rises toward the intake port guided by the top surface of the piston. A flow from the center to the side of the intake port can also be generated. Therefore, when the sub-combustion chamber is arranged so that the first flame ejection hole faces the tumble flow, it may be arranged near the exhaust port or near the intake port. , the strong intake air ejected from the intake port hits directly and for a long time, so it is suitable as an arrangement position.

In the present invention, the first flame ejection hole of the torch opens only toward the center of the main combustion chamber so as to face the tumble flow and has a large diameter. It is easy to enter the interior of the room. On the other hand, since the second flame ejection holes are open in a direction intersecting the flow of the tumble flow, the tumble flow tends to suck out the residual gas inside from the second flame ejection holes due to the ejector effect.

In this case, since the first flame ejection hole has a large diameter, the intake air is easily pushed into the first flame ejection hole. It can be strongly aspirated.

Therefore, due to the pushing action of the intake air that has flowed into the first flame ejection hole and the pulling action of the second flame ejection hole, the flow of the intake air entering the sub-combustion chamber through the first flame ejection hole and flowing from the second flame ejection hole is caused. It is possible to quickly scavenge the residual gas accumulated in the sub-combustion chamber from the second flame ejection hole and to quickly fill the sub-combustion chamber with intake air (air-fuel mixture). Therefore, the combustion in the auxiliary combustion chamber can be ensured, and the combustion in the main combustion chamber can also be stabilized.

In addition, since the first flame ejection hole is opened so as to face the flow direction of the tumble flow, the flame ejected from the main combustion chamber is ejected so as to pass through the axis of the main combustion chamber (cylinder bore). The first flame ejection hole has a large diameter and a strong flame is ejected so as to cross the center of the main combustion chamber, so the fuel (air mixture) filling the main combustion chamber can be ignited in a wide range at once. can. Therefore, rapid combustion can be realized and complete combustion can be promoted.

In addition, since the first flame ejection hole opens toward the center of the main combustion chamber, the flame ejected from the first flame ejection hole spreads over a longer distance, so that the flame does not reach the wall surface of the main combustion chamber (cylinder bore). inner peripheral surface). As a result, it is possible to prevent or remarkably suppress the occurrence of cooling loss due to the heat of the flame being absorbed by the cylinder block.

Flames are also emitted from the second flame ejection holes, but since the diameter of the second flame ejection holes is small and the flames are thin, even if the flames ejected from the second flame ejection holes hit the inner surface of the main combustion chamber, the amount of heat absorbed is not many. Therefore, it is possible to promote reliable scavenging and complete combustion while suppressing cooling loss.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows embodiment, (A) is a schematic plan view of a cylinder head, (B) is sectional drawing which looked at (A) from the IIA-IIA view direction, and drew the state where the subcombustion chamber does not exist. . FIG. 1(A) is a sectional view taken along line IIA-IIA, and (B) is a sectional view taken along line BB of (A). FIG. 2 is a sectional view taken along line IIA-IIA of FIG. 1(A) in an intake stroke;

(1) Description of Structure Next, embodiments of the present invention will be described with reference to the drawings. The internal combustion engine has, as basic elements, a cylinder block 1 and a cylinder head 3 fixed to the upper surface of the cylinder block 1 via a gasket 2. The cylinder block 1 has a plurality of cylinders arranged in the crank axial direction (front-to-rear direction). of cylinder bores 4 are formed.

A conical recess 5 is formed in the cylinder head 3 corresponding to the cylinder bore 4 , and the cylinder bore 4 and the recess 5 form a main combustion chamber 6 . Naturally, the piston 7 is slidably fitted in the cylinder bore 4 .

A pair of intake ports 8 and a pair of exhaust ports 9 are formed on both sides of the crank axis in correspondence with each recess 5 in the cylinder head 3 . The intake port 8 is opened and closed by an intake valve 10 and the exhaust port 9 is opened and closed by an exhaust valve 11 . Each intake port 8 opens to the intake side surface of the cylinder head 3 (in some cases, a pair of intake ports 8 are gathered together to open to the intake side surface).

On the other hand, each pair of exhaust ports 9 are gathered in a collective passage formed in the cylinder head 3, one exhaust outlet hole is formed in the collective passage, and the exhaust outlet hole opens to the exhaust side of the cylinder head 3. are doing.

A unit-type sub-combustion chamber 12 is arranged at a portion of the cylinder head 3 between the start ends of the pair of exhaust ports 9 . The sub-combustion chamber 12 has a hollow housing 14 with a spark plug 13 mounted thereon, and is fixed by screwing into a mounting hole formed in the cylinder head 3 .

The housing 14 is integrally formed with a small-diameter torch 15 having its tip protruding into the recess 5 , and a portion of the torch 15 protruding into the recess 5 is provided with an opening only toward the intake port 8 . A first flame ejection hole 16 and a pair of front and rear second flame ejection holes 17 opening in the crank axial direction are formed. Since the sub-combustion chamber 12 is positioned between the pair of front and rear exhaust ports 9, the first flame ejection hole 16 opens only toward the center O of the main combustion chamber 6 (cylinder bore 4).

The inner diameter of the first flame ejection holes 16 is set larger than the inner diameter of the second flame ejection holes 17 . Specifically, in terms of inner diameter comparison, the first flame ejection hole 16 can be set to be about 1.5 to 3 times the second flame ejection hole 17 . In actual dimensions, the first flame ejection hole 16 can be set to 2-3 mm, and the second flame ejection hole 17 can be set to 1-2 mm.

A recess 18 is formed in the top surface of the piston 7 . Therefore, the tip of the torch 15 is set to enter the recess 18 of the auxiliary combustion chamber 12 slightly when the piston 7 is at the top dead center. Thereby, the first flame ejection hole 16 and the second flame ejection hole 17 can be lowered as much as possible to improve contact with the tumble flow.

(2) Explanation of action As shown in FIG. 3, during the intake stroke and the compression stroke when the intake valve 10 is open, the intake air jetted from the intake port 8 flows so as to lick the recess 5 of the cylinder head 3 and flows into the cylinder bore. 4 and generates a tumble flow 19 that is directed downward by the guiding action of the inner surface of the cylinder bore 4 . The tumble flow 19, which is directed downward by the guide action of the inner surface of the cylinder bore 4, is changed in direction to the side of the intake port 8 by licking the top surface of the cylinder head 3, and then upward by the upward movement of the piston 7. .

When the intake ports 8 jet from the front and rear intake ports 8 into the main combustion chamber 6, the distance between the cylinder bores 4 in the crankshaft direction gradually decreases beyond the center O of the main combustion chamber 6. The intake air ejected from the port 8 tends to converge at a portion between the front and rear exhaust ports 9 in a plan view and changes direction downward.

Therefore, as shown by the solid line in FIG. 2(B), the intake air tends to flow into the first flame ejection hole 16 of the torch 15 from the front, while the second flame ejection hole 17 of the torch 15 faces forward and backward. Therefore, the tumble flow tends to flow across the opening surface of the second flame ejection hole 17 .

As a result, an ejector effect is produced, and the residual gas is sucked from the second flame ejection holes 17 by the negative pressure. Therefore, due to the pushing action of the intake air flowing from the first flame ejection hole 16 and the pulling action from the second flame ejection hole 17, the intake air flows inside the torch 15 from the first flame ejection hole 16 and the second flame ejection is ejected. A flow escaping from the hole 17 is generated, and along with this flow, residual gas remaining inside the sub-combustion chamber 12 is scavenged, and intake air (fresh air, air-fuel mixture) is introduced inside the sub-combustion chamber 12. fill up.

Therefore, combustion in the auxiliary combustion chamber 12 is ensured, and stable operation of the engine can be realized. As a result, stable operation can be maintained even if the air-fuel mixture is lean or the proportion of EGR gas is high.

The flame generated inside the sub-combustion chamber 12 by combustion spreads from the first flame ejection hole 16 and is ejected into the main combustion chamber 6, as indicated by the dotted line arrow in FIG. 2(B). Since the first flame ejection hole 16 opens toward the center O of the main combustion chamber 6, the air-fuel mixture filling the main combustion chamber 6 can be ignited at once.

In other words, when the torch 15 is arranged in the center of the main combustion chamber 6, the flames are ejected radially, so to speak, the flames propagate in a donut shape. Since the mixture scatters and diffuses across the central portion of the chamber 6, the combustion of the air-fuel mixture spreads rapidly from the center in the radial direction, thereby increasing the combustion speed and contributing to complete combustion. As a result, it is possible to contribute to the improvement of the output and to promote the cleaning of the exhaust gas.

Also, since the torch 15 is away from the center O of the main combustion chamber 6, the flame ejected from the first flame ejection hole 16 flies over a long distance. Therefore, the flame ejected from the first flame ejection hole 16 is extinguished before reaching the inner surface of the cylinder bore 4 and does not hit the inner surface of the cylinder bore 4 . Therefore, the heat of the flame is not taken away by the cylinder bore 4 to cause a cooling loss.

On the other hand, the second flame ejection hole 17 ejects flame in the direction of the crankshaft axis, but since the second flame ejection hole 17 has a small diameter and the length of the ejected flame is short, even if the flame contacts the inner surface of the cylinder bore 4, it will be lost. Heat is slight. Therefore, it can be said that there is almost no cooling loss.

Note that in the compression stroke, the tumble flow is deformed, and a flow directed from the axial center side of the main combustion chamber 6 toward the intake port 8 side is also generated. Therefore, it is possible to dispose the auxiliary combustion chamber 12 at a portion between the front and rear intake ports 8 . However, since the flow from the axial side of the main combustion chamber 6 to the side of the intake port 8 is generated for a short time, it is preferable to arrange it near the exhaust port 9 in terms of scavenging reliability.

Although the embodiments of the present invention have been described above, the present invention can be embodied in various other ways. For example, in the embodiment, the intake air supplied from the intake port is taken into the sub-combustion chamber and burned, but it is also possible to provide a dedicated fuel injection injector in the sub-combustion chamber.

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

1 Cylinder Block 3 Cylinder Head 4 Cylinder Bore Constituting Main Combustion Chamber 5 Recess Constituting Main Combustion Chamber 6 Main Combustion Chamber 7 Piston 8 Intake Port 9 Exhaust Port 10 Intake Valve 12 Sub-Combustion Chamber 13 Ignition Plug 14 Housing 15 Torch 16 First flame ejection hole 17 Second flame ejection hole

Claims (1)

The cylinder head and the cylinder block form a main combustion chamber with an intake port and an exhaust port that are open , and the intake air jetted from the intake port generates a tumble flow in the main combustion chamber,
Further, the cylinder head is provided with an auxiliary combustion chamber having a torch exposed to the main combustion chamber, and the torch is formed with a flame ejection hole,
The sub-combustion chamber is provided with a spark plug and is arranged at a position on the exhaust side or the intake side across the center of the main combustion chamber and at a position where the torch is exposed to the tumble flow . A first flame ejection hole that faces only the center of the main combustion chamber and faces the tumble flow, and a pair of second flame ejection holes that open in a direction crossing the tumble flow are formed. wherein the first flame ejection hole is formed to have a larger diameter than the second flame ejection hole,
Internal combustion engine with auxiliary combustion chamber.

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