JP2007138780A - Sub-chamber internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve stable burning in an auxiliary chamber by forming a proper air-fuel mixture in the auxiliary chamber 12 in an auxiliary chamber type internal combustion engine. <P>SOLUTION: This auxiliary chamber type internal combustion engine comprises the auxiliary chamber 12 communicating with a main combustion chamber 7, fuel injection valves 10a, 10b forming the air-fuel mixture in the main combustion chamber 7 by inter-colliding a plurality of fuel sprays directly jetted into the main combustion chamber 12 and jetting the fuel to supply a part of the air-fuel mixture into the auxiliary chamber 12, and an ignition plug 13 igniting the air-fuel mixture in the auxiliary chamber 12. The fuel injection valves 10a, 10b change the collided positions of the fuel spray by changing the fuel injection pressures and fuel injection start timings according to the rotational speed of the engine. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sub-chamber internal combustion engine having a sub-chamber communicating with a main combustion chamber.

  Conventionally, as shown in Patent Document 1, in a sub-chamber spark ignition two-cycle gas engine, a sub-chamber communicating with a main combustion chamber is formed in a cylinder head, an ignition plug is disposed in the sub-chamber, It is known to provide a fuel injection valve for supplying fuel to the sub chamber and the main combustion chamber. As a result, a lean air-fuel mixture is formed in the main combustion chamber, while a part of the injected fuel collides with the wall surface formed in the sub-chamber to form the air-fuel mixture, and the ignition plug By igniting at, stable spark ignition is possible even during lean combustion.

Further, as shown in Patent Document 2, in a cylinder injection spark ignition engine, an ignition plug is disposed at a substantially central position of the combustion chamber, and two fuel injection valves are disposed so as to face the cylinder side wall. It is known that the fuel spray collision position is moved to the exhaust side according to the load by relatively changing the fuel injection from the fuel injection valve.
JP 7-91256 A Japanese Patent Laid-Open No. 10-176628

  However, in the engine described in Patent Document 1, since a part of the fuel spray injected from the fuel injection valve is guided by the sub chamber wall surface and the air-fuel mixture is supplied to the spark plug in the sub chamber, the sub chamber wall surface The fuel adheres to the surface and a liquid film is formed, rich combustion occurs in the sub chamber, smoke is generated, and as a result, the spark plug is smoldered. In addition, since the volume of the sub chamber is increased due to the construction of the air-fuel mixture in the sub chamber, it is difficult to apply to a general 4-valve 4-cycle engine, and it is difficult to increase the compression ratio. is there.

In the internal combustion engine described in Patent Document 2, it is difficult to change the size of the air-fuel mixture in the main combustion chamber by, for example, a method in which a cavity is formed on the piston crown and an air-fuel mixture is formed in the cavity.
The present invention has been made in view of the above problems, and an object of the present invention is to perform stable sub-chamber combustion by forming an appropriate air-fuel mixture in the sub-chamber in a sub-chamber internal combustion engine.

  Therefore, in the present invention, a sub-chamber communicating with the main combustion chamber and a plurality of fuel sprays directly injected into the main combustion chamber collide with each other to form an air-fuel mixture in the main combustion chamber and And a plurality of fuel injection valves for injecting fuel so as to supply a portion, and an ignition device for igniting an air-fuel mixture in the sub chamber.

  According to the present invention, fuel sprays injected from a plurality of fuel injection valves can collide to form an air-fuel mixture in the main combustion chamber, and a part of the air-fuel mixture can be supplied to the sub-chamber. Even if a fuel supply device for forming an air-fuel mixture in the sub chamber is not separately provided, a combustible air-fuel mixture can be formed in the sub chamber, and an effect is achieved that stable sub chamber combustion can be performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of a sub-chamber internal combustion engine (hereinafter referred to as “engine”) 1 showing a first embodiment of the present invention.
The engine 1 has a main combustion chamber 7 formed by a cylinder head 2, a cylinder block 3, a piston 4, an intake valve 5 and an exhaust valve 6.

The main combustion chamber 7 can supply intake air from the intake port 8 via the intake valve 5, and can discharge exhaust gas to the exhaust port 9 via the exhaust valve 6.
In FIG. 1, fuel injection valves 10 a and 10 b are provided facing the main combustion chamber 7 on the intake side and the exhaust side of the cylinder head 2, respectively. Thus, the fuel injection valves 10a and 10b can inject fuel directly into the main combustion chamber 7. The fuel injection valves 10 a and 10 b are arranged to face the intake side and the exhaust side so that the fuel spray collides in the main combustion chamber 7.

The fuel injection valves 10a and 10b used here are hole injection valves, but there are no particular types including swirl injection valves, multi-hole injection valves, and external opening injection valves.
The cylinder head 2 is formed with a sub chamber 12 communicating with the main combustion chamber 7 via a communication passage (communication hole) 11. The sub chamber 12 is formed at a substantially central position of the main combustion chamber 7. The sub chamber 12 has a smaller volume than the main combustion chamber 7. A front end portion 12a of the substantially hemispherical sub chamber 12 protrudes into the main combustion chamber 7, and a plurality of communication holes 11 are formed therein.

A spark plug 13 capable of spark ignition is provided in the sub chamber 12. The spark plug 13 is connected to the ignition coil 14 and ignites a spark in the sub chamber 12 by an ignition signal from an engine control unit (hereinafter referred to as “ECU”) 20. In FIG. 1, these constitute an ignition device.
Further, the ECU 20 receives output signals from the crank angle sensor 15, the accelerator pedal sensor 16, the fuel pressure sensor 17, and the like in order to detect the operating state of the engine 1.

The ECU 20 performs calculations based on these output signals. For example, the engine speed is calculated based on the output signal of the crank angle sensor 15. The engine load is calculated based on the output signal of the accelerator pedal sensor 16. Based on the output signal of the fuel pressure sensor 17, the pressure of the fuel injected from the fuel injection valves 10a and 10b is calculated.
The ECU 20 performs various controls based on these calculation results. For example, the fuel injection pressure and the fuel injection start timing from the fuel injection valves 10a and 10b are controlled, and the ignition timing of the spark plug 13 provided in the sub chamber 11 is controlled. The ECU 20 controls the two fuel injection valves 10a and 10b independently of each other.

  Further, in FIG. 1, as shown in FIG. 2 (a), the fuel injection valves 10a and 10b are inclined to the intake side and the exhaust side, respectively, but the present invention is not limited to this. For example, as shown in FIG. 2 (b), the fuel injection valves 10a and 10b are arranged upright in the cylinder axis direction, and the fuel injection ports are deflected toward the cylinder center axis to cause fuel spray to collide near the cylinder center axis. You may make it make it. Further, as shown in FIG. 2 (c), fuel injection valves 10a and 10b are disposed in the cylinder block 3, and the fuel injection ports are deflected toward the cylinder central axis so that the fuel spray collides in the vicinity of the cylinder central axis. It may be.

  Further, as shown in FIG. 3 (a), the fuel injection valves 10a and 10b are not limited to being arranged one by one on the intake side and the exhaust side of the cylinder head 2 or the cylinder block 3 when viewed in plan. That is, if the fuel spray collides in the main combustion chamber 7, for example, as shown in FIG. 3 (b), the fuel injection valves 10a and 10b are opposed to the front side and the rear side one by one. You may arrange. As shown in FIG. 3C, even if the fuel injection valves 10a and 10b are not arranged to face each other, they are arranged one by one on the intake side and the front side so that the fuel sprays interfere (collision). Also good. Further, as shown in FIG. 3 (d), fuel sprays may collide by arranging three fuel injection valves, one on each of the intake side, the front side, and the rear side.

FIG. 4 is a view showing a state in which fuel is directly injected into the main combustion chamber 7 from the fuel injection valves 10a and 10b.
The fuel sprays injected from the fuel injection valves 10a and 10b in the first half of the intake stroke or the compression stroke collide in the main combustion chamber 7 to form an air-fuel mixture. In FIG. 4, the fuel spray collision position is on the cylinder central axis. The collided fuel spray diffuses in the vertical direction of the cylinder shaft. For this reason, a part of the air-fuel mixture formed in the main combustion chamber 7 is supplied into the sub chamber 12 through the communication passage 11. Further, the compression operation of the piston 4 facilitates supplying a part of the air-fuel mixture into the sub chamber 12. Thereby, since the combustible air-fuel mixture can be supplied into the sub chamber 12, a device for directly injecting and supplying the fuel into the sub chamber 12 becomes unnecessary.

The spark plug 13 disposed in the sub chamber 12 sparks the combustible air-fuel mixture supplied in the sub chamber 12 in the vicinity of the compression top dead center, thereby allowing the main combustion chamber 7 to communicate with the main combustion chamber 7. A flame torch (spout flame) is formed inside. This makes it possible to ignite the air-fuel mixture formed in the main combustion chamber 7 and perform combustion.
FIGS. 5 (a) and 5 (b) are diagrams respectively showing the formation state of the air-fuel mixture when the collision position of the fuel spray injected from the fuel injection valves 10a and 10b is changed according to the engine speed. (C) is a diagram showing a distance (distance shown in (b)) L from the fuel spray collision position X to the center line position Y of the sub chamber 12 according to the engine rotation speed.

As shown in the figure, in this configuration, the fuel injection valves 10a and 10b are controlled so that the fuel spray collision position approaches the sub chamber 12 as the engine speed increases. Details of this control will be described later.
Each of the fuel injection valves 10a and 10b is injected when the time until the compression top dead center of the piston 4 is longer than that when the engine speed is high, such as when the engine speed is low as shown in FIG. The fuel spray collides in the vicinity of the sub chamber 12 at a position X separated from the position Y of the center line of the sub chamber 12 by a predetermined distance L in the radial direction. Do. Thereby, a part of the air-fuel mixture diffused in the cylinder axial direction due to the collision of the fuel spray is supplied into the sub chamber 12.

  That is, when the engine speed is low, the time to compression top dead center is long, so if the air-fuel mixture is formed in the vicinity of the sub chamber 12 and at the position Y of the center line of the sub chamber 12, An excessively rich air-fuel mixture will be supplied into the sub chamber 12 and smoldering of the spark plug 13 will occur. In order to prevent this, the fuel spray collision position is controlled away from the sub chamber 12 by controlling the fuel injection pressure and the fuel injection start timing of the fuel injection valves 10a and 10b at the time of low engine rotation. Yes. Then, an air-fuel mixture formed in the main combustion chamber 7 through one side of the communication passage 11 formed from the main combustion chamber 7 to the sub chamber 12 (in FIG. 5A, the intake-side communication passage 11). The concentration of the air-fuel mixture in the sub chamber 12 is adjusted by supplying a part of the gas to the sub chamber 12.

  Further, each fuel injection valve 10a, 10b has a shorter time to the compression top dead center of the piston 4 as compared with when the engine speed is low as in the case where the engine speed is high as shown in FIG. When the supply amount of the air-fuel mixture from 7 to the sub chamber 12 decreases and the air-fuel mixture in the sub chamber 12 becomes lean and torch ignition is difficult, fuel spray is performed at the position Y of the central axis of the sub chamber 12 By causing the collision, the air-fuel mixture is formed in the main combustion chamber 7 and the air-fuel mixture is supplied into the sub chamber 12. Thereby, the air-fuel mixture supplied to the sub chamber 12 through the communication passage 11 increases, and as a result, a combustible air-fuel mixture can be formed in the sub chamber 12.

  As described above, by bringing the collision position of the fuel spray in the main combustion chamber 7 closer to the sub chamber 12 as the engine speed increases, an excessively rich air-fuel mixture is supplied into the sub chamber 12 when the engine speed is low. In addition, the air-fuel mixture suitable for combustion is supplied into the auxiliary combustion chamber 12 when the engine speed is high. The combustion in the main combustion chamber 7 can be performed by igniting the air-fuel mixture in the sub chamber 12 by the spark plug 13 disposed in the sub chamber 12. Further, since a combustible air-fuel mixture is formed in the sub chamber 12 by the air-fuel mixture supplied from the main combustion chamber 7, even if the air-fuel ratio of the air-fuel mixture in the main combustion chamber 7 is lean, Combustion can be performed, the limit on the lean air-fuel ratio side can be expanded, and fuel efficiency can be improved.

FIG. 6A shows the average fuel injection pressure (fuel pressure) of the fuel injection valves 10a and 10b with respect to the engine speed, and FIG. 6B shows the fuel injection start timing with respect to the engine speed.
In FIG. 6 (a), the average fuel injection pressure of the fuel injection valves 10a and 10b is constant when the engine speed is less than a predetermined value, and when the engine speed exceeds the predetermined value, the average fuel injection pressure is increased as the engine speed increases. In FIG. 6 (b), the fuel injection start timing from the fuel injection valves 10a and 10b is advanced and the air-fuel mixture is advanced at an early stage as the engine speed increases. Form. For this reason, as the piston 4 rises, more air-fuel mixture (fuel) can be supplied to the sub chamber 12 to form a combustible air-fuel mixture in the sub chamber 12, and the operating range by torch combustion can be expanded to the engine rotation high speed side. .

FIGS. 7 (a) and 7 (b) are diagrams respectively showing the formation state of the air-fuel mixture when the collision position of the fuel spray injected from the fuel injection valves 10a and 10b is changed according to the engine load. (C) is a diagram showing a distance (a distance shown in (b)) L from the fuel spray collision position X to the center line position Y of the sub chamber 12 according to the engine load.
As shown in the drawing, in this configuration, the fuel injection valves 10a and 10b are controlled so that the fuel spray collision position X is moved away from the center line position Y of the sub chamber 12 by a predetermined distance L as the engine load increases. . Details of this control will be described later.

  As a result, the fuel injection pressure of the fuel injection valves 10a and 10b is low as in the low load state shown in FIG. 7 (a), and the amount of air-fuel mixture supplied from the main combustion chamber 7 to the sub chamber 12 is reduced. Even when the air-fuel mixture in the chamber 12 is excessively lean and torch ignition is difficult, by setting the fuel spray collision position to the center position Y of the sub-chamber 12, the air-fuel mixture concentration at this position Y is locally increased. Can be rich. A part of the air-fuel mixture formed by the fuel diffused to the upper side of the cylinder shaft due to the collision of the fuel spray is supplied to the sub chamber 12 through the communication passage 11, and as a result, the combustible air-fuel mixture enters the sub chamber 12. Since it is formed, stable torch ignition is possible.

Further, when the fuel pressure injected from the fuel injection valves 10a and 10b is high as in the case of a high load shown in FIG. 7B, a predetermined distance from the position Y of the center line of the sub chamber 12 in the cylinder radial direction. The fuel injection start timing of the fuel injection valves 10a and 10b is controlled so that an air-fuel mixture is formed at a position X separated by L.
That is, at the time of high load, the fuel injection pressure of the fuel injection valves 10a and 10b is high, so that if the air-fuel mixture is formed at the position Y of the center line of the sub chamber 12, Due to the diffusion, an excessively rich air-fuel mixture is supplied into the sub chamber 12 and smoldering occurs in the spark plug 13. In order to prevent this, at the time of high load, the fuel spray collision position X is set to the position of the center line of the sub chamber 12 by controlling the fuel injection pressure and the fuel injection start timing of the fuel injection valves 10a and 10b. The distance from Y is a predetermined distance L. Then, an air-fuel mixture formed in the main combustion chamber 7 through one side of the communication passage 11 formed from the main combustion chamber 7 to the sub chamber 12 (in FIG. 7B, the intake-side communication passage 11). Is supplied to the sub chamber 12 to prevent an excessively rich mixture from being supplied into the sub chamber 12 and to allow the mixture suitable for combustion to be supplied into the sub chamber 12. Yes.

  As described above, as the engine load increases, the fuel spray collision position in the main combustion chamber 7 is moved away from the sub chamber 12 in the vicinity of the sub chamber 12 than in the low load state, so that combustion occurs in the sub chamber 12 at low load. It is possible to prevent an excessively rich mixture from being supplied into the auxiliary combustion chamber 12 at a high load. When strong torch ignition is performed at high load, knocking may occur. However, by making the sub-chamber 12 in the flammable range weakly lean, the torch flame strength can be reduced, and the main combustion chamber 7, the combustion speed does not increase excessively, and knock resistance is improved.

  As shown in FIG. 7 (b), if the fuel injection is controlled so that the fuel spray collides on the intake side, the tumble flow is strengthened to promote mixing, so that the inside of the cylinder is reached by the torch ignition timing. The air-fuel mixture can be distributed uniformly throughout the main combustion chamber 7. On the other hand, the air-fuel mixture is biased at the time of high load, and there is a concern that the performance of the full load is reduced. However, if fuel injection is controlled so that fuel spray collides on the exhaust side where the wall temperature of the cylinder block 3 is high, fuel evaporation Can be expected to advance.

Next, fuel injection control of the fuel injection valves 10a and 10b will be described with reference to FIG.
FIG. 8 is a diagram showing that the fuel injection pressure and the fuel injection start timing of the fuel injection valves 10a and 10b are controlled according to the engine speed and the engine load. Thereby, the collision position of the fuel spray injected from the fuel injection valves 10a and 10b can be changed, and the air-fuel mixture supplied into the sub chamber 12 can be adjusted to a desired concentration.

When the fuel spray collision position is controlled by the fuel injection pressure, the difference between the fuel injection pressures of the two fuel injection valves 10a and 10b is reduced as the engine speed increases (FIG. 8 (A)). The load is increased as the load increases (FIG. 8C). Thereby, the collision position of the fuel spray is offset to the fuel injection valve side where the fuel injection pressure is relatively low.
In addition, when the fuel spray collision position is controlled by the fuel injection start timing, the difference between the fuel injection start timings of the two fuel injection valves 10a and 10b is reduced as the engine speed increases (see FIG. )), And increases as the engine load increases (FIG. 8D). Thereby, the collision position of the fuel spray is offset to the fuel injection valve side where the fuel injection start timing becomes relatively late.

  As described above, the fuel spray collision position is changed according to the difference in fuel injection pressure or the difference in fuel injection start timing, so that mixing suitable for combustion in the sub chamber 12 according to the operating conditions (engine speed and engine load). Supply your mind. That is, when it is difficult to supply the air-fuel mixture from the main combustion chamber 7 into the sub chamber 12 and the air-fuel ratio in the sub chamber 12 may become excessively lean, the fuel spray collision position X is set to the sub chamber. The combustible air-fuel mixture is supplied into the sub chamber 12 by setting it to the vicinity of the front end portion 12a of 12 (for example, the position Y of the center line of the sub chamber 12 as shown in FIG. 7A). On the other hand, when there is a possibility that the air-fuel ratio in the sub chamber 12 becomes excessively rich, the fuel spray collision position is moved away from the front end portion 12a of the sub chamber 12 (for example, FIG. As shown in the figure, by setting the position X) at a predetermined distance L in the cylinder radial direction from the position Y of the center line of the sub chamber 12, excessive supply of the air-fuel mixture into the sub chamber 12 is suppressed.

FIG. 9 is a diagram showing a case where fuel injection is performed using the fuel injection valves 10a and 10b having the injection port variable mechanism that changes the injection angle θ of the injected fuel.
FIG. 9A shows the mixture distribution when the fuel injection angle θ is wide-angle injection, and FIG. 9B shows the mixture distribution when narrow-angle injection is used. FIG. 9C shows the fuel injection angle θ according to the engine speed, and FIG. 9D shows the fuel injection angle θ according to the engine load.

  As shown in FIG. 9C, as the engine speed increases, the fuel injection angle θ of the fuel injection valves 10a and 10b is increased as shown in FIG. To bring it closer to the sub chamber 12. Thereby, even when the engine speed increases and the period until the piston top dead center is short, the air-fuel mixture suitable for combustion can be supplied into the sub chamber 12.

  Further, as shown in FIG. 9D, as the engine load increases, the fuel injection angle θ of the fuel injection valves 10a and 10b is reduced as shown in FIG. A position X ′ that is a predetermined distance L ′ downward from the position Y ′ of the front end 12a (communication path 11) of the cylinder 12 in the cylinder axial direction is set. Thus, when the fuel injection pressure is high and the load is high, the concentration of the air-fuel mixture supplied into the sub chamber 12 is adjusted to prevent the air-fuel mixture in the sub chamber 12 from becoming excessively rich.

  The effect in this case is equivalent to the case where the collision position is changed depending on the fuel injection pressure and the fuel injection start timing. However, in the case of control by the fuel injection angle θ, the collision position is almost in the center of the cylinder, so the main combustion There is an advantage that the air-fuel mixture in the chamber 7 does not deviate in the cylinder horizontal cross-sectional direction. In this way, the fuel spray collides (interferences) in the cylinder and changes the timing and concentration at which the air-fuel mixture is formed in the vicinity of the sub-chamber 12, thereby changing the air-fuel mixture concentration in the sub-chamber 12 to the engine speed or engine load. It can be optimized accordingly.

FIG. 10 is a diagram showing the mixture formation with respect to the crank angle.
FIG. 10A shows a state in which fuel injection is started from the fuel injection valves 10a and 10b into the main combustion chamber 7 when the crank angle is in the vicinity of the bottom dead center. In (b), the injected fuel sprays collide with each other to form an air-fuel mixture in the main combustion chamber 7. A part of the air-fuel mixture formed in the main combustion chamber 7 is supplied into the sub chamber 12 through the communication passage 11 by the piston 4 rising. (C) shows the state of the air-fuel mixture when torch ignition is performed by the spark plug 13 in the sub chamber 12 when the piston 4 is near the top dead center.

  In the illustrated engine 1, the crown of the piston 4 is flat, so that the fuel spray injected from the fuel injection valves 10 a and 10 b is burned to the main dead center near the top dead center where the torch ignition is performed. It is distributed uniformly throughout the chamber 7 (FIG. 10 (C)). The fuel sprays injected by the two fuel injection valves 10a and 10b collide in the main combustion chamber 7 to form an air-fuel mixture, and a part of the air-fuel mixture is supplied into the sub-chamber 12, and the sub-chamber In order to form a combustible air-fuel mixture in the cylinder 12, when a spark plug 13 is ignited, a substantially columnar flame is ejected from the communication passage 11 of the sub chamber 12 and torch combustion can be performed in the main combustion chamber 7. .

  According to the present embodiment, the sub-chamber 12 communicating with the main combustion chamber 7 and a plurality of fuel sprays directly injected into the main combustion chamber 12 collide to form an air-fuel mixture in the main combustion chamber 7. A plurality of fuel injection valves (in FIG. 1, two fuel injection valves 10a and 10b) that inject fuel to supply a part of the air-fuel mixture into the sub chamber 12 and the air fuel mixture in the sub chamber 12 are ignited. And an ignition device (including a spark plug 13 and an ignition coil 14 in FIG. 1). For this reason, fuel sprays injected from a plurality of fuel injection valves collide to form an air-fuel mixture in the main combustion chamber 7 and a part of the air-fuel mixture can be supplied into the sub chamber 12. The combustible air-fuel mixture can be formed in the sub-chamber 12 without providing a separate fuel supply device for forming the air-fuel mixture in the sub-chamber 12, and stable combustion can be performed.

  Further, according to the present embodiment, the plurality of fuel injection valves (in FIG. 1, the two fuel injection valves 10a and 10b) change the fuel injection pressures according to operating conditions (for example, engine speed and engine load). The fuel spray collision position in the main combustion chamber 7 is changed in the cylinder radial direction. Therefore, it is possible to adjust the concentration of the air-fuel mixture supplied into the sub chamber 12 by colliding the fuel spray on the side where the speed of the fuel injected from the fuel injection valve is low.

  Further, according to the present embodiment, the average fuel injection pressure of the plurality of fuel injection valves (in FIG. 1, two fuel injection valves 10a and 10b) is increased as the engine speed increases. For this reason, atomization of the fuel spray can be promoted as the engine speed increases, and even when the time to top dead center is shortened, an air-fuel mixture is formed in the vicinity of the sub chamber 12 and sufficient in the sub chamber 12 An air-fuel mixture can be supplied.

  Further, according to the present embodiment, the plurality of fuel injection valves (in FIG. 1, the two fuel injection valves 10a and 10b) have their fuel injection start timings according to operating conditions (for example, engine speed and engine load). The collision position of the fuel spray in the main combustion chamber 7 is changed in the cylinder radial direction. For this reason, it is possible to adjust the concentration of the air-fuel mixture supplied into the sub chamber 12 by colliding the fuel spray on the later side of the fuel injection start timing. Further, it is not necessary to excessively increase the fuel injection pressure, and this can be realized at a low cost. Furthermore, since the atomization level between the plurality of fuel sprays is the same, the homogeneity of the air-fuel mixture on the main combustion chamber 7 side can be maintained.

  Further, according to the present embodiment, the collision position of the fuel spray in the main combustion chamber 7 is brought closer to the sub chamber 12 as the engine speed increases. For this reason, for example, the fuel mixing time from the fuel injection to the compression top dead center is relatively short as in a high load, compared with the low load, and the amount of air-fuel mixture flowing into the sub chamber 12 is reduced. Even in the case where the gas inside is lean and ignition tends to be unstable, the combustible air-fuel mixture can be stably supplied into the sub chamber 12.

Further, according to the present embodiment, the collision position of the fuel spray in the main combustion chamber 7 is moved away from the sub chamber 12 as the engine load increases. For this reason, it is possible to prevent the air-fuel mixture formed in the vicinity of the sub chamber 12 from being diluted and the air-fuel mixture in the sub chamber 12 from becoming excessively rich.
Moreover, according to this embodiment, it has the nozzle angle variable mechanism which changes the fuel injection angle (theta) of the fuel injection valves 10a and 10b, and this nozzle angle variable mechanism changes the collision position of a fuel spray to a cylinder axial direction. For this reason, it is not necessary to shift the collision position of the fuel spray in the cylinder horizontal direction, and the concentration of the air-fuel mixture supplied to the sub chamber 12 can be varied. As shown in FIG. 1, when the sub chamber 12 is formed at a substantially central position of the main combustion chamber 7, the fuel spray collision position is almost directly below the sub chamber 12, so that the main chamber 1 is symmetrical. A good mixture can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 11A is a diagram showing the configuration of the engine 1 of the second embodiment, and the configuration is substantially the same as the configuration described in the first embodiment. However, it is different in that a cavity 4a is formed on the crown surface of the piston 4.
As the fuel injection valves 10a and 10b, multi-hole injection valves having a plurality of fuel injection holes at the tip end portions are used as shown in FIG. Thereby, the fuel injected from the fuel injection valves 10a and 10b is injected at a predetermined interval in the circumferential direction when viewed in the cross section of the fuel spray.

  This embodiment has a stratified combustion operation mode in which stratified combustion is performed by forming a stratified mixture in the main combustion chamber 7 by colliding fuel sprays under predetermined stratified combustion operation conditions. The predetermined stratified combustion operation condition is set in advance according to the engine speed and the engine load. For example, it is assumed that a predetermined stratified combustion operation condition is satisfied when the engine speed and the engine load are within a predetermined operation region (for example, a region where the engine speed is low and the load is low).

In order to promote the formation of the stratified mixture in the main combustion chamber 7, a substantially circular cavity 4 a is formed on the crown surface of the piston 4 as viewed from above the cylinder shaft. The cavity 4a is formed with a side wall portion formed on the upper side in the cylinder axial direction from the peripheral edge portion of the substantially circular bottom portion.
The cavity 4a is formed almost directly under the cylinder axis position where the fuel spray collides and interferes. Even when the fuel spray collision position is offset in the horizontal cross-sectional direction of the cylinder, the collided fuel spray remains in the cavity 4a and the cylinder. The aperture is such that a stratified mixture can be formed on the upper side in the axial direction.

When fuel spray collides with the cavity 4a in the main combustion chamber 7, the fuel spray descending downward in the cylinder axial direction collides with the cavity 4a, and the fuel spray rises through the bottom and side walls of the cavity 4a. An air stream is formed to form a stratified mixture.
Further, as described above, the fuel sprays injected from the two fuel injection valves 10a and 10b supply air-fuel mixture into the sub chamber 12 after colliding. And by igniting in the subchamber 12 with the spark plug 13, the substantially columnar flame is ejected from the communication path 11 of the subchamber 12 to the stratified mixture in the main combustion chamber 7, and torch combustion is performed.

  Here, if the air-fuel mixture in the main combustion chamber is guided into the sub chamber using only the cavity of the piston crown surface, the positional relationship between the fuel spray and the piston cavity depends on the fuel injection start timing and the engine speed. In addition to the difficulty in supplying fuel to the sub-chamber at high engine speeds, the amount of unburned HC emissions increases and smoke worsens due to fuel adhering to the cylinder wall. Is concerned.

However, in the present embodiment, the fuel spray is collided in the main combustion chamber 7, the air-fuel mixture is supplied into the sub chamber 12, and the stratified air-fuel mixture is formed in the cavity 4a and on the upper side in the cylinder axial direction. Prevents increase in HC emissions and smoke deterioration due to fuel adhering to the cylinder wall.
FIG. 12 shows a state where the injected fuel spray is swollen by the Coanda effect when fuel is injected from the multi-hole injection valve shown in FIG. That is, the fuel spray injected from the fuel injection valves 10a and 10b has a sag due to the Coanda effect after the fuel spray interference, and has been atomized in the axial direction of the fuel injection valves 10a and 10b (the fuel spray centerline direction). Only the droplets have the property of being carried by the surrounding flow. For this reason, even when a plurality of fuel sprays interfere and collide with each other in the space in the main combustion chamber 7, the mixture size can be made compact with little rebound of the droplets after the collision, and fuel injection can be performed quickly. Even if it performs, the effect that the diffusion of the air-fuel mixture is difficult to proceed is obtained.

FIG. 13 shows a state in which an air-fuel mixture is formed in the main combustion chamber 7 with respect to the crank angle when such a multi-hole injection valve is used.
The basic control method is the same as that of the first embodiment except that the stratified mixture is formed in the cavity 4a that receives the fuel spray collided (or interfered) in the main combustion chamber 7.

That is, by controlling the injection pressure of the fuel injected from the fuel injection valves 10a and 10b, the injection start timing, etc., at a position near the sub chamber 12 or a position away from the sub chamber 12 by a predetermined distance L according to operating conditions. The fuel spray is collided to form an air-fuel mixture in the cavity 4a in the main combustion chamber 7 and above it, and the concentration of the air-fuel mixture supplied into the sub chamber 12 is adjusted.
In addition, in the fuel spray characteristic in which the fuel spray is reduced by the Coanda effect, the air-fuel mixture is stratified to the center of the combustion chamber on the contrary in the homogeneous operation, and it is difficult to distribute it uniformly throughout the combustion chamber.

  For this reason, as shown in FIG. 14, during homogeneous operation, a phase difference is provided at each fuel injection start timing of the two fuel injection valves 10 a and 10 b to alternately perform multistage injection, thereby interfering with the injected fuel spray. Control is performed without (collision). This promotes homogenization of the air-fuel mixture in the cylinder. In addition, when there are three or more fuel injection valves, each fuel injection valve alternates to perform fuel injection so that fuel sprays do not collide.

Further, during the homogeneous operation, fuel injection may be performed with only one of the two fuel injection valves 10 a and 10 b to form a stratified mixture in the main combustion chamber 7. In this case, control is performed so that fuel injection from the other fuel injection valve is stopped. In this case, homogenization is achieved by strengthening the flow.
According to the present embodiment, the fuel injection valves 10a and 10b are multi-hole injection valves having a plurality of fuel injection holes at the tip portions. For this reason, as shown in FIG. 12, the atomization of the fuel spray is achieved by colliding the droplets and the air-fuel mixture which are atomized by the flow due to the sag phenomenon due to the Coanda effect such as initial spraying, and the deterioration of smoke and HC Can be suppressed.

According to the present embodiment, the cavity 4 a is formed in the piston 4. For this reason, the air-fuel mixture formed by the collision of the fuel spray can be held in the cavity 4a and above it. And a clear air-fuel mixture having an interface resistant to diffusion can be formed, and deterioration of unburned HC can be prevented.
Further, according to the present embodiment, under predetermined stratified combustion operation conditions (for example, at low engine speed and low load), a plurality of fuel sprays collide with each other to form a stratified mixture in the main combustion chamber 7 and The air-fuel mixture in the chamber 12 is ignited to burn the stratified air-fuel mixture in the main combustion chamber 7. Therefore, for example, a stratified mixture can be generated by colliding fuel spray in the main combustion chamber 7 at a low load, and a stable operation can be performed.

Further, according to the present embodiment, during the homogeneous operation, the plurality of fuel injection valves 10a and 10b alternately perform fuel injection and do not cause fuel spray collision. For this reason, a homogeneous air-fuel mixture can be formed in the entire main combustion chamber 7 during the homogeneous operation.
Further, according to the present embodiment, during the homogeneous operation, the plurality of fuel injection valves 10a and 10b inject fuel from only one and do not cause fuel spray collision. For this reason, at the time of homogeneous operation, a homogeneous air-fuel mixture can be formed in the entire main combustion chamber 7 with easy control.

Configuration diagram of the sub-chamber internal combustion engine of the first embodiment Sectional drawing which shows the position which provides a fuel injection valve Plan view showing the position where the fuel injection valve is provided Diagram showing collision of fuel spray The figure which shows the state which changes the formation position of air-fuel | gaseous mixture according to an engine speed The figure which shows the average fuel-injection pressure of a fuel-injection valve with respect to engine speed, and fuel-injection start time The figure which shows the state which changes the formation position of air-fuel | gaseous mixture according to engine load The figure which shows the relationship between the difference of the fuel injection pressure with respect to engine speed or the difference of fuel injection start time, and the difference of the fuel injection pressure with respect to engine load, or the difference of fuel injection start time The figure which showed the case where the fuel injection angle is changed according to the operating condition Diagram showing mixture formation with respect to crank angle The block diagram which shows the subchamber internal combustion engine of 2nd Embodiment The figure which shows the state by which the injected fuel spray is squeezed by the Coanda effect Diagram showing mixture formation with respect to crank angle The figure which shows the state which provides the phase difference in fuel injection timing and performs multistage injection

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder head 3 Cylinder block 4 Piston 4a Cavity 7 Main combustion chamber 10a, 10b Fuel injection valve 11 Communication path 12 Subchamber 12a Tip part 13 Spark plug 14 Ignition coil 15 Crank angle sensor 16 Accelerator pedal sensor 17 Fuel pressure detection sensor 20 ECU

Claims (12)

A sub-chamber communicating with the main combustion chamber;
A plurality of fuel sprays directly injected into the main combustion chamber collide with each other to form an air-fuel mixture in the main combustion chamber, and a plurality of fuel injections to supply a part of the air-fuel mixture into the sub chamber A fuel injection valve;
An ignition device for igniting the air-fuel mixture in the sub chamber;
A sub-chamber internal combustion engine comprising:   2. The sub chamber according to claim 1, wherein each of the plurality of fuel injection valves changes each fuel injection pressure in accordance with an operating condition to change a collision position of fuel spray in the main combustion chamber in a cylinder radial direction. Internal combustion engine.   3. The sub-chamber internal combustion engine according to claim 2, wherein an average fuel injection pressure of the plurality of fuel injection valves is increased as the engine speed increases.   The plurality of fuel injection valves change the fuel injection start timing according to operating conditions, and change the collision position of fuel spray in the main combustion chamber in the cylinder radial direction. 4. The sub-chamber internal combustion engine according to any one of 3.   The sub-chamber internal combustion engine according to any one of claims 2 to 4, wherein a collision position of fuel spray in the main combustion chamber is brought closer to the sub chamber as the engine rotation speed increases.   The sub-chamber internal combustion engine according to any one of claims 2 to 5, wherein the collision position of the fuel spray in the main combustion chamber is moved away from the sub-chamber as the engine load increases.   The sub-chamber type according to claim 1, further comprising a nozzle angle variable mechanism that changes a fuel injection angle of the fuel injection valve, and the nozzle angle variable mechanism changes a collision position of fuel spray in a cylinder axial direction. Internal combustion engine.   The sub-chamber internal combustion engine according to any one of claims 1 to 7, wherein the fuel injection valve is a multi-hole injection valve having a plurality of fuel injection holes at a tip portion.   The sub-chamber internal combustion engine according to any one of claims 1 to 8, wherein a cavity is formed in the piston.   Under predetermined stratified combustion operation conditions, the fuel sprays collide with each other to form a stratified mixture in the main combustion chamber, ignite the mixture in the sub chamber, and the stratified mixture in the main combustion chamber The sub-chamber internal combustion engine according to any one of claims 1 to 9, wherein combustion is performed.   11. The sub-chamber internal combustion engine according to claim 10, wherein during the homogeneous operation, the plurality of fuel injection valves alternately perform fuel injection to prevent collision of fuel spray.   11. The sub-chamber internal combustion engine according to claim 10, wherein during the homogeneous operation, the plurality of fuel injection valves perform fuel injection from only one of them and do not cause fuel spray collision.

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