JPWO2020196206A1 - Sub-chamber internal combustion engine - Google Patents

Abstract

The sub-chamber internal combustion engine includes a main chamber, a sub-chamber, a communication passage, and a spark plug. The main chamber is defined by a cylinder, a cylinder head, and a piston. The sub chamber is separated from the main chamber, and the cross section seen from the axial direction of the cylinder is formed in a circular shape. The communication passage connects the main room and the sub-room. The communication passage is formed so as to be inclined diagonally with respect to the radial direction of the sub chamber when viewed from the axial direction of the cylinder. The spark plug has a first electrode. The first electrode ignites the air-fuel mixture introduced from the main chamber to the sub chamber via the communication passage. The center of the first electrode is arranged at a position different from the center of the sub chamber when viewed from the axial direction of the cylinder.

Description

The present disclosure relates to a subchamber internal combustion engine.

Conventionally, a sub-chamber type internal combustion engine having a main chamber and a sub-chamber connected to the main chamber via a continuous passage has been proposed (see, for example, Japanese Patent No. 4389777). In such a sub-chamber internal combustion engine, an air-fuel mixture is formed from the fuel injected into the main chamber. The formed air-fuel mixture is supplied to the sub-chamber via the communication passage, and is ignited by the spark plug in the sub-chamber. This forms a flame. The flame formed in the sub-chamber is jetted into the main chamber through the communication passage and ignites the air-fuel mixture in the main chamber. By injecting the flame formed in the sub chamber into the main chamber in this way, the combustion speed of the main chamber is increased. This enables operation with a leaner air-fuel ratio and improves fuel efficiency.

Japanese Patent No. 4389777 discloses a sub-chamber type internal combustion engine having one sub-chamber and a sub-chamber type internal combustion engine having two sub-chambers. In a sub-chamber type internal combustion engine having one sub-chamber, a sub-chamber is provided in the center of a cylinder, and a spark plug is provided in the center of the sub-chamber. Further, the four communication passages are formed so as to be inclined diagonally upward and in the circumferential direction. As a result, the air-fuel mixture becomes an ascending swirling flow in the sub-chamber.

However, in the sub-chamber type internal combustion engine having one sub-chamber disclosed in Japanese Patent No. 438977, the air-fuel mixture becomes a swirling flow that rises along the inner wall of the sub-chamber. Therefore, the flow velocity of the air-fuel mixture in the central part of the sub chamber becomes slow. Therefore, if the spark plug is placed in the center of the sub-chamber, initial combustion is unlikely to be promoted. As a result, the propagation velocity of the flame from the sub chamber to the main chamber becomes slow.

The embodiments of the present disclosure relate to a sub-chamber internal combustion engine that promotes initial combustion in the sub-chamber.

According to an embodiment of the present disclosure, the sub-chamber internal combustion engine includes a main chamber, a sub-chamber, a communication passage, and an ignition unit. The main chamber is defined by a cylinder, a cylinder head, and a piston. The sub chamber is separated from the main chamber, and the cross section seen from the axial direction of the cylinder is formed in a circular shape. The communication passage connects the main room and the sub-room. The communication passage is formed so as to be inclined diagonally with respect to the radial direction of the sub chamber when viewed from the axial direction of the cylinder. The ignition unit has a first electrode provided in the sub chamber. The first electrode ignites the air-fuel mixture introduced from the main chamber to the sub chamber via the communication passage. The center of the first electrode is arranged at a position different from the center of the sub chamber when viewed from the axial direction of the cylinder.

In this sub-chamber internal combustion engine, the communication passage is formed so as to be inclined diagonally with respect to the radial direction of the sub-chamber, so that a swirling flow of the air-fuel mixture swirling along the inner circumference of the sub-chamber is generated in the sub-chamber. .. Further, the center of the first electrode is arranged at a position different from the center of the sub chamber. As a result, the air-fuel mixture is ignited by the ignition unit at a position where the flow velocity of the swirling flow generated along the inner circumference of the sub-chamber is high. Therefore, advection and flame retention promote initial combustion.

The sub-chamber internal combustion engine may further include a fuel injection valve that injects fuel into the main chamber. The center of the first electrode may be arranged on the fuel injection valve side with respect to the center of the sub chamber.

According to this configuration, since the first electrode is arranged on the fuel injection valve side, the air-fuel mixture is ignited from the fuel injection valve side in the space of the sub chamber. As a result, the flame is emitted first from the fuel injection valve side where the air-fuel ratio of the air-fuel mixture in the main chamber tends to be lean. Therefore, the combustion in the main chamber becomes homogeneous.

The sub-chamber internal combustion engine may have a second electrode into which electrons emitted from the first electrode flow. The communication passage may generate a swirling flow of the air-fuel mixture swirling along the inner circumference of the sub chamber in the sub chamber. Then, the first electrode and the second electrode may be arranged adjacent to each other in the order of the second electrode and the first electrode along the rotation direction of the swirling flow.

When the second electrode is arranged on the downstream side of the swirling flow, heat escapes to the second electrode after ignition. According to this configuration, since the second electrode is arranged on the upstream side of the swirling flow from the first electrode which is the starting point of ignition, heat does not escape after ignition. This promotes combustion in the sub-chamber. Further, since the turbulence of the air-fuel mixture becomes large downstream of the second electrode, combustion in the sub-chamber is further promoted.

The communication passage has an introduction port for introducing the air-fuel mixture into the sub-chamber, and a swirling flow of the air-fuel mixture toward the cylinder head side may be generated in the sub-chamber while swirling along the inner circumference of the sub-chamber. Then, the tip position of the first electrode may be arranged at a position higher than the position where the center line of the introduction port of the communication passage intersects the inner peripheral portion of the sub chamber.

According to this configuration, at a position higher than the position where the center line of the introduction port of the communication passage intersects the inner peripheral portion of the sub chamber, a well-organized swirling flow is formed in the sub chamber, so that a flame is generated at the time of ignition. Propagate efficiently.

The center of the first electrode may be arranged away from the center of the auxiliary chamber by at least half the radius in the circular cross section of the auxiliary chamber.

According to this configuration, the air-fuel mixture is ignited at a position where the speed of the swirling flow of the air-fuel mixture is high, so that the initial combustion is further promoted by advection and flame retention, and the flame is further promoted from one sub chamber to the main chamber. It is sent out quickly.

The vertical sectional view which shows the schematic structure of the auxiliary chamber type internal combustion engine by one Embodiment of this disclosure. The cross-sectional view which shows the formation part of the communication passage of the auxiliary chamber type internal combustion engine of FIG. The vertical sectional view which shows the formation part of the communication passage of the auxiliary chamber type internal combustion engine of FIG.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following specification, the cylinder axial direction Q indicates the direction in which the piston slides along the cylinder. When described as the vertical direction, the cylinder axial direction Q is indicated, and the cylinder head side is referred to as “up” and the piston side is referred to as “down”. Further, the left-right direction L indicates a direction orthogonal to the cylinder axial direction Q and where the intake port and the exhaust port are arranged. Further, the crank axial direction P indicates a direction orthogonal to the cylinder axial direction Q and where the cylinder N is arranged.

As shown in FIG. 1, the sub-chamber type internal combustion engine 1 includes a main chamber 4, a sub-chamber 6 adjacent to the main chamber 4, a plurality of communication passages 8 communicating the main chamber 4 and the sub-chamber 6, and a spark plug. (Example of ignition unit) 10, a second electrode 10b, and a fuel injection valve 12 are provided. In the present embodiment, the sub-chamber internal combustion engine 1 is a series-type internal combustion engine in which a plurality of cylinders N including a main chamber 4 and a sub chamber 6 are arranged in series. That is, the main chamber 4, the sub chamber 6, the plurality of communication passages 8, the spark plug 10, the second electrode 10b, and the fuel injection valve 12 are provided in each cylinder N. However, the arrangement of the cylinders N is not limited to this, and may be a V type or a horizontally opposed type. Further, a plurality of sub-chambers 6 may be provided in each cylinder N.

The main chamber 4 is a space defined by the cylinder 101a of the cylinder block 101, the cylinder head 102, and the piston 103. In the present embodiment, the main chamber 4 has a pent roof shape and has two slopes toward the intake port 105 side and the exhaust port 110 side of the cylinder head 102. The main chamber 4 is connected to the intake port 105 via an intake valve 104 driven by an intake cam (not shown). The intake port 105 is connected to an intake passage, a throttle valve, and an air cleaner (not shown). Further, the main chamber 4 is connected to an exhaust port 110, an exhaust passage (not shown), and an exhaust purification catalyst (not shown) via an exhaust valve 109 driven by an exhaust cam (not shown). To.

The sub chamber 6 is provided at the top of the pent roof shape and is adjacent to the main chamber 4. The sub-chamber 6 is a space defined by the bottom portion 61a and the side wall 61b of the sub-chamber wall 61. More specifically, the sub-chamber wall 61 has a circular horizontal cross section (a cross-section perpendicular to the protruding direction of the sub-chamber 6) seen from the cylinder axial direction Q, and the bottom portion 61a is formed in a hemispherical shape. The sub chamber 6 projects from the cylinder head 102 toward the main chamber 4 and is separated from the main chamber 4 via the sub chamber wall 61. In the present embodiment, the sub chamber 6 is provided substantially in the center of the line of intersection (ridge line) of the two slopes of the main chamber 4 having a pent roof shape. Further, in the present embodiment, the center X1 of the sub chamber 6 is the same as that of the main chamber 4. However, the sub chamber 6 may be provided offset from the substantially center of the main chamber 4 toward the inner wall surface of the cylinder 101a. The volume of the sub chamber 6 is smaller than that of the main chamber 4, and the flame of the air-fuel mixture ignited by the spark plug 10 quickly propagates into the sub chamber 6.

A plurality of communication passages 8 are provided at the bottom 61a of the sub chamber wall 61. The communication passage 8 communicates the main room 4 and the sub-chamber 6 and guides the air-fuel mixture of the main room 4 to the sub-chamber 6. Further, the connecting passage 8 sends out the flame generated in the sub chamber 6 to the main chamber 4. The communication passage 8 has an injection port 8a facing the main room 4 and an introduction port 8b facing the sub room 6. In the present embodiment, for example, six communication passages 8 are provided. FIG. 2 is a view of the cross section of the sub chamber 6 in the bottom portion 61a in which the communication passage 8 is formed, as viewed from the piston 103 side. As shown in FIG. 1, the communication passage 8 is inclined in the vertical direction (same as the cylinder axial direction Q) from the main chamber 4, and as shown in FIG. 2, the sub chamber 6 is perpendicular to the cylinder axial direction Q. In the cross section, the cylindrical sub-chamber 6 is inclined diagonally with respect to the radial direction. Further, during the compression stroke, the air-fuel mixture in the main chamber 4 passes through the communication passage 8 and is introduced into the sub chamber 6. As a result, a swirling flow SF of the air-fuel mixture toward the cylinder head 102 side while spirally swirling is formed along the side wall 61b (inner circumference of the sub chamber 6) of the sub chamber wall 61. The flow velocity of the swirling flow SF is faster on the side wall 61b side of the sub chamber 6 than on the center side of the sub chamber 6.

As shown in an enlarged manner in FIG. 1, the spark plug 10 is arranged to face the first electrode 10a and the first electrode 10a, and the second electrode 10b into which the electrons emitted from the first electrode 10a flow into the spark plug 10 Have. In this embodiment, the second electrode 10b is provided on the spark plug 10. Further, in the present embodiment, the second electrode 10b has an L-shaped bent shape, and is arranged with a gap below the rod-shaped first electrode 10a. The spark plug 10 discharges electric energy from the first electrode 10a toward the second electrode 10b to generate sparks. The generated spark ignites the air-fuel mixture in the sub-chamber 6. That is, in the present embodiment, the first electrode 10a and the second electrode 10b form a pair of electrodes and ignite the air-fuel mixture in the sub chamber 6. As shown in FIG. 1, the center X2 of the first electrode 10a is arranged at a position different from the center X1 of the sub chamber 6 and protrudes into the sub chamber 6. More specifically, as shown in FIG. 2, the center X2 of the first electrode 10a is arranged closer to the fuel injection valve 12 than the center X1 of the sub chamber 6. Further, the center X2 of the first electrode 10a is separated from the center X1 of the sub chamber 6 toward the side wall 61b by half R / 2 or more of the radius R of the side wall 61b of the sub chamber 6.

As shown in FIG. 2, the second electrode 10b is arranged on the upstream side of the swirling flow SF of the air-fuel mixture with respect to the center X2 of the first electrode 10a. In other words, the first electrode 10a and the second electrode 10b are arranged adjacent to each other in the order of the second electrode 10b and the first electrode 10a along the rotation direction of the swirling flow SF of the air-fuel mixture. FIG. 3 is a vertical sectional view of the sub chamber 6 perpendicular to the left-right direction L. That is, it is a cross-sectional view of the sub chamber 6 of FIG. 1 as viewed from the center X1 of the sub chamber 6 in the direction of the center X2 of the first electrode 10a. As shown in FIG. 3, at the tip position 10c of the first electrode 10a, the center line C (including the extension line of the center line C) of the introduction port 8b of the communication passage 8 is the side wall 61b of the sub chamber wall 61 of the sub chamber 6. It is arranged at a position higher than the position H intersecting with.

The fuel injection valve 12 is directed to the main chamber 4. Further, the fuel injection valve 12 is provided outside the sub chamber 6. In the present embodiment, the fuel injection valve 12 injects fuel directly into the main chamber 4. That is, the sub-chamber internal combustion engine 1 is a direct injection type internal combustion engine. The injection amount and injection timing of the fuel injection valve 12 are controlled by a control unit (not shown). Further, the fuel injection valve 12 is connected to a fuel injection pump (not shown) and a fuel tank. The fuel injection valve 12 is arranged on the intake valve 104 side of the cylinder head 102. In the present embodiment, the air-fuel ratio of the sub-chamber internal combustion engine 1 is set to a value leaner than the theoretical air-fuel ratio. That is, the sub-chamber internal combustion engine 1 is operated by lean burn. This improves fuel efficiency.

In the sub-chamber type internal combustion engine 1 configured as described above, in the intake stroke, the intake valve 104 is opened, the piston 103 is lowered, and the intake air flows into the main chamber 4 and the sub-chamber 6. In this embodiment, the intake air is pressurized by a supercharger (not shown). As a result, the pressure in the main chamber 4 and the sub chamber 6 becomes the same as the pressure of the intake air. In the intake stroke, the fuel injection valve 12 is controlled so as to mainly perform fuel injection for supplying fuel to the main chamber 4. The injected fuel mixes with the intake air in the main chamber 4 to form an air-fuel mixture. The air-fuel mixture is supplied to the entire main chamber 4 as the piston 103 is lowered.

In the compression stroke, the intake valve 104 is closed and the piston 103 is raised, so that the air-fuel mixture in the main chamber 4 is compressed. At this time, the pressure in the main chamber 4 rises. When the piston 103 rises in the compression stroke, the air-fuel mixture is introduced from the main chamber 4 to the sub chamber 6 via the communication passage 8. At this time, the air-fuel mixture becomes a swirling flow rising by the communication passage 8 and is introduced into the sub-chamber 6. As described above, the flow velocity of the swirling flow is faster on the side wall 61b side (outer peripheral side) of the sub chamber 6 than on the center X1 side of the sub chamber 6.

In the present embodiment, the center X2 of the first electrode 10a of the spark plug 10 is arranged closer to the side wall 61b than the center X1 of the sub chamber 6. As a result, the air-fuel mixture is ignited by the spark plug 10 at a position where the flow velocity of the swirling flow generated along the side wall 61b in the sub chamber 6 is high. Therefore, advection and flame retention promote initial combustion, and the flame is quickly sent out from the sub chamber 6 toward the main chamber 4.

Further, since the center X2 of the first electrode 10a is arranged closer to the fuel injection valve 12 than the center X1, the air-fuel mixture having a richer air-fuel ratio is ignited by the spark plug 10. As a result, the flame from the sub-chamber 6 toward the main room 4 becomes stronger, and a powerful flame is quickly sent out from the sub-chamber 6 toward the main room 4.

As described above, in the sub-chamber type internal combustion engine 1 of the present embodiment, the center X2 of the first electrode 10a of the spark plug 10 is arranged at a position different from the center X1 of the sub-chamber 6. As a result, the air-fuel mixture is ignited by the spark plug 10 at a position where the flow velocity of the swirling flow generated along the side wall 61b in the sub chamber 6 is high. Therefore, advection and flame retention promote initial combustion, and the flame is quickly sent out from the sub chamber 6 toward the main chamber 4.

<Other embodiments>
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various changes can be made without departing from the gist of the invention. In particular, the plurality of modifications described in the present specification can be arbitrarily combined as needed.

In the above embodiment, the sub-chamber internal combustion engine 1 is a direct injection type internal combustion engine, but the present disclosure is not limited thereto. For example, it may be a sub-chamber type internal combustion engine provided with an intake port injector provided in the intake port 105.

In the above embodiment, the entire spark plug 10 is arranged on the side wall 61b side of the center X1 of the sub chamber 6, but the present disclosure is not limited to this. For example, the first electrode 10a may be an eccentric spark plug. Further, a spark plug having no second electrode 10b may be used, and the second electrode 10b may be provided on the side wall 61b of the sub chamber 6. Further, the second electrode 10b is, for example, a creeping spark plug or the like, and a plurality of the second electrodes 10b may be provided. Further, the center of the first electrode of the creeping spark plug may be arranged on the side wall 61b side of the center X1 of the sub chamber 6.

According to the embodiment of the present disclosure, the sub-chamber internal combustion engine (1) is
A main chamber (4) defined by a cylinder (101a), a cylinder head (102), and a piston (103).
A sub-chamber (6) separated from the main chamber (4) and having a circular cross section seen from the axial direction of the cylinder (101a).
A communication passage (8) connecting the main room (4) and the sub room (6), and
Ignition having a first electrode (10a) provided in the sub chamber (6) and igniting an air-fuel mixture introduced from the main chamber (4) into the sub chamber (6) via the communication passage (8). Part (10) and
Equipped with
The communication passage (8) is formed so as to be inclined diagonally with respect to the radial direction of the sub chamber (6) when viewed from the axial direction of the cylinder (101a).
The center (X2) of the first electrode (10a) is arranged at a position different from the center (X1) of the sub chamber (6) when viewed from the axial direction of the cylinder (101a).

The sub-chamber internal combustion engine (1) may further include an injection valve (12) for injecting fuel into the main chamber (4). Then, the center (X2) of the first electrode (10a) may be arranged closer to the injection valve (12) than the center (X1) of the sub chamber (6).

The sub-chamber internal combustion engine (1) may further include a second electrode (10b) into which electrons emitted from the first electrode (10a) flow. The communication passage (8) may generate a swirling flow (SF) of the air-fuel mixture swirling along the inner circumference of the sub chamber (6) in the sub chamber (6). The first electrode (10a) and the second electrode (10b) are adjacent to the second electrode (10b) and the first electrode (10a) in this order along the rotation direction of the swirling flow (SF). May be arranged.

The communication passage (8) has an introduction port (8b) for introducing the air-fuel mixture into the sub chamber (6), and the cylinder head (102) swivels along the inner circumference of the sub chamber (6). The swirling flow (SF) of the air-fuel mixture toward the) side may be generated in the sub-chamber. The tip position of the first electrode (10a) is higher than the position (H) where the center line (C) of the introduction port (8b) intersects the inner peripheral portion of the sub chamber (6). It may be arranged.

The first electrode (10a) may be arranged away from the center (X1) of the sub chamber (6) by at least half of the radius in the circular cross section of the sub chamber (6).

This application is based on Japanese Patent Application No. 2019-061127 filed on March 27, 2019, the contents of which are incorporated herein by reference.

1: Sub-chamber internal combustion engine 4: Main room 6: Sub-chamber 8: Communication passage 10: Spark plug (ignition part)
10a: 1st electrode 10b: 2nd electrode 10c: Tip position 12: Fuel injection valve 61: Sub chamber wall,
61b: Side wall 101a: Cylinder 102: Cylinder head 103: Piston C: Center line R: Radius R / 2: Half radius SF: Swirling flow X1: Center of sub-chamber X2: Center of first electrode

As shown enlarged in FIG. 1, the spark plug 10 is provided along the cylinder axial direction. Further, the spark plug 10 has a first electrode 10a and a second electrode 10b which is arranged so as to face the first electrode 10a and into which electrons emitted from the first electrode 10a flow. In this embodiment, the second electrode 10b is provided on the spark plug 10. Further, in the present embodiment, the second electrode 10b has an L-shaped bent shape, and is arranged with a gap below the rod-shaped first electrode 10a. The spark plug 10 discharges electric energy from the first electrode 10a toward the second electrode 10b to generate sparks. The generated spark ignites the air-fuel mixture in the sub-chamber 6. That is, in the present embodiment, the first electrode 10a and the second electrode 10b form a pair of electrodes and ignite the air-fuel mixture in the sub chamber 6. As shown in FIG. 1, the center X2 of the first electrode 10a is arranged at a position different from the center X1 of the sub chamber 6 and protrudes into the sub chamber 6. More specifically, as shown in FIG. 2, the center X2 of the first electrode 10a is arranged closer to the fuel injection valve 12 than the center X1 of the sub chamber 6. Further, the center X2 of the first electrode 10a is separated from the center X1 of the sub chamber 6 toward the side wall 61b by half R / 2 or more of the radius R of the side wall 61b of the sub chamber 6.

Claims (5)

The main chamber defined by the cylinder, the cylinder head, and the piston,
A sub-chamber separated from the main chamber and having a circular cross section when viewed from the axial direction of the cylinder.
A communication passage connecting the main room and the sub room,
An ignition unit provided in the sub-chamber and having a first electrode for igniting the air-fuel mixture introduced from the main room through the communication passage into the sub-chamber.
Equipped with
The communication passage is formed so as to be inclined diagonally with respect to the radial direction of the sub chamber when viewed from the axial direction of the cylinder.
The center of the first electrode is arranged at a position different from the center of the sub chamber when viewed from the axial direction of the cylinder.
Sub-chamber internal combustion engine. The sub-chamber internal combustion engine further includes an injection valve for injecting fuel into the main chamber.
The center of the first electrode is arranged on the injection valve side with respect to the center of the sub chamber.
The sub-chamber internal combustion engine according to claim 1. The sub-chamber internal combustion engine further includes a second electrode into which electrons emitted from the first electrode flow.
The communication passage generates a swirling flow of the air-fuel mixture that swirls along the inner circumference of the sub-chamber in the sub-chamber.
The first electrode and the second electrode are arranged adjacent to each other in the order of the second electrode and the first electrode along the rotation direction of the swirling flow.
The sub-chamber internal combustion engine according to claim 1 or 2. The communication passage has an introduction port for introducing the air-fuel mixture into the sub-chamber, and swirls the air-fuel mixture toward the cylinder head side while swirling along the inner circumference of the sub-chamber into the sub-chamber. Generate,
The one according to any one of claims 1 to 3, wherein the tip position of the first electrode is arranged at a position higher than the position where the center line of the introduction port intersects the inner peripheral portion of the sub chamber. Sub-chamber internal combustion engine. The first electrode is arranged away from the center of the subchamber for more than half of the circular radius.
The sub-chamber internal combustion engine according to any one of claims 1 to 4.

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