JP2006112240A - Cylinder direct injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder direct injection type internal combustion engine in which injected fuel mist can form an air fuel mixture mass without affecting the gas flow generated in the cylinder. <P>SOLUTION: An annular groove 12 is formed on a flat piston crown surface. The air fuel mixture mass is formed near an ignition plug 10 by injecting fuel while the injected fuel mist collides with the annular groove 12. Thereby, the gas flow in the cylinder can be prevented from penetrating into the annular groove 12 to permit the formation of the uniform layered air fuel mixture mass. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an in-cylinder direct injection internal combustion engine, and more particularly to an in-cylinder direct injection internal combustion engine that makes it possible to reliably form an air-fuel mixture in the cylinder.

  In an in-cylinder direct injection internal combustion engine, in order to ignite and burn the air-fuel mixture steadily, the air-fuel mixture of an appropriate size and air-fuel ratio is stratified in the cylinder according to the engine rotation and load. It is important to form.

Therefore, Patent Document 1 discloses an internal combustion engine using a piston in which an inner cavity is provided near the center of the piston crown surface and an outer cavity is provided on the outer periphery thereof. In this prior art, when the engine load is relatively large, the fuel is injected twice during the compression stroke. In other words, the first fuel injection collides with the outer cavity, and the second fuel injection collides with the inner cavity to form a relatively large mixture and a relatively small mixture. It is supposed to form a mixed air mass.
JP 2004-36519 A

  However, in the above-described prior art, various gas flows generated in the cylinder may affect the injected fuel spray. That is, the gas flow that has entered the cavity affects the size, speed, direction, and the like of the air-fuel mixture that rolls up, and may interfere with the formation of the desired air-fuel mixture.

  Accordingly, an object of the present invention is to provide a direct injection type internal combustion engine that can form a uniform air-fuel mixture without the fuel spray being affected by the gas flow in the cylinder.

  In order to achieve the above object, in the present invention, an annular groove is formed on a flat piston crown surface. In the present invention, the fuel spray injected from the fuel injection valve during the compression stroke is injected at the time of collision with the annular groove, so that the air-fuel mixture formed by the collision is in the vicinity of the spark plug disposed at the upper portion of the combustion chamber. To be formed.

  According to the present invention, since the influence of the gas flow generated in the cylinder does not reach the annular groove, the influence of the gas flow on the fuel spray can be suppressed. As a result, a uniform air-fuel mixture can be formed, and stable stratified combustion can be performed.

  Hereinafter, a first embodiment will be described with reference to the drawings.

In FIG. 1, the combustion chamber 4 is formed by a cylinder head 1, a cylinder block 2, and a piston 3, and a gasket 15 is interposed between the cylinder head 1 and the cylinder block 2. The combustion chamber 4 communicates with the intake port 6 via the intake valve 5 and the exhaust port 8 via the exhaust valve 7 at the upper part thereof. Here, the intake port 6 is a port that does not generate a swirl or tumble flow.
The fuel injection valve 9 provided in the cylinder head 1 is positioned substantially coaxially with the piston 3 and in the upper center of the combustion chamber 4, and a spark plug 10 is provided in the vicinity thereof. The fuel injection valve 9 injects fuel spray radially into the combustion chamber 4 along the conical surface when the valve is opened, and the central axis of the conical surface is substantially parallel to the cylinder central axis.

  An annular groove 12 is formed on the flat piston crown surface. The piston crown surface on the inner side of the annular groove 12 is referred to as the center surface 11, and the outer piston crown surface is referred to as the piston peripheral edge portion 13.

  Here, it is preferable that the fuel injection valve 9 has a strong directivity in order to cause fuel spray to collide with the annular groove 12 stably. Therefore, for example, a hole nozzle injection valve shown in FIG. 2 or a swirl nozzle injection valve in which a part of a conical surface as shown in FIG. 3 is cut out along the fuel injection direction is used.

  The fuel injection valve 9 and the spark plug 10 perform fuel injection and ignition based on a signal from an engine control unit (ECU) 14. The ECU 14 performs calculations based on operation state signals such as an air flow meter signal, an accelerator opening signal, a crank angle sensor signal, a cooling water temperature sensor signal, and controls the fuel injection amount, fuel injection timing, and ignition timing.

  The internal combustion engine configured as described above takes two combustion forms. The fuel-air mixture is stratified by performing fuel injection during the compression stroke, and stratified combustion that realizes operation with a lean air-fuel ratio and fuel injection during the intake stroke, and sufficient air-fuel ratio is obtained by taking sufficient mixing time. It is homogeneous combustion that realizes operation in the (theoretical air-fuel ratio) state. In the internal combustion engine of the present invention, stratified combustion is performed in the region of relatively low load and low rotation in all operating conditions, and homogeneous combustion is performed in the region of relatively high load and high rotation.

  FIG. 4 shows a schematic view of the piston in the present embodiment.

  In the present embodiment, the outer wall surface 12c is formed in a so-called reentrant shape that is inclined from the bottom 12b toward the center of the combustion chamber 4. The inclined surface is inclined toward the center of the combustion chamber 4 by an angle d with respect to the vertical line.

  The inner wall surface 12a is inclined from the bottom 12b toward the center of the combustion chamber 4 along the fuel spray injected by the fuel injection valve 9, and the inclined surface is inclined by an angle e with respect to the vertical line. Yes. Here, the angle e is set larger than the angle d.

  In the piston peripheral edge portion 13, the surface 13 a is at the same height as the center surface 11 when viewed in the longitudinal section of the piston, and is connected to the annular groove 12 at the upper end f of the outer wall surface 12 c. That is, in this embodiment, the upper end g of the inner wall surface 12a and the upper end f of the outer wall surface 12c are the same height.

  The surface 13b is connected to the surface 13a at the end h on the piston peripheral side, and is located above the combustion chamber 4 so that the height is lower than the upper end f of the outer wall 12c in the piston peripheral direction when viewed in the piston longitudinal section. It is a tapered surface having the apex of the conical surface. The inclination is set at an angle i with respect to the vertical line. On the other hand, the piston peripheral side of the surface 13b is formed by a surface 13c, and is connected to the surface 13b in FIG. The surface 13c is parallel to the surface 13a and is an annular surface that is lower than the surface 13a by m as viewed in the longitudinal section of the piston.

  During stratified combustion, fuel injection by the fuel injection valve 9 is performed during the compression stroke. The fuel injection is performed such that the injected fuel spray collides with the annular groove 12 to form an air-fuel mixture in the vicinity of the spark plug 10.

  FIG. 5 shows a schematic diagram of fuel spraying and air-fuel mixture formation in the fuel injection.

  First, the fuel spray injected by the fuel injection valve 9 collides with the inner wall surface 12a without being affected by the gas flow in the cylinder ((a) of FIG. 5). The impinging fuel spray is rolled up from the outer wall surface 12c to the upper side of the combustion chamber 4 by the penetrating force (FIG. 5 (b)), and there is no unevenness in the desired size in the vicinity of the spark plug 10. A mixed gas mass is formed ((c) of FIG. 5).

  The effect by 1st Embodiment is demonstrated.

  As shown in FIG. 6 (b), in the conventional piston, the injected fuel spray is affected by the gas flow in the cylinder and affects the air-fuel mixture finally formed. That is, the gas flow generated at the piston central part and the piston peripheral part penetrates into the cavity provided in the piston central part, so that the air-fuel mixture formed is poorly wound, or the direction of the winding is There was a fear that it would not be in the desired direction.

  On the other hand, in the present invention, due to the shape of the annular groove 12 formed on the flat piston crown surface and the central surface 11 surrounded by the annular groove 12, the gas flow generated in the cylinder enters the annular groove 12. Can be suppressed. That is, the gas flow along the flat central surface 11 no longer has a downward velocity component when viewed in the longitudinal section of the piston, and flows in the combustion chamber without entering the annular groove 12. As a result, the fuel spray that has collided with the annular groove 12 can be rolled up without being affected by the gas flow in the cylinder, and an air-fuel mixture having a desired size can be formed (see FIG. 6 ( a)).

  In the present embodiment, the outer wall surface 12c is formed in a reentrant shape inclined from the bottom 12b toward the center of the combustion chamber 4 by an angle d with respect to the vertical line. As a result, the formed air-fuel mixture can be prevented from diffusing and the air-fuel mixture can be effectively carried to the vicinity of the spark plug 10. In this case, even if the outer wall surface 12c of the annular groove 12 is perpendicular to the vertical line, there is an effect of preventing the air-fuel mixture from diffusing, but in order to supply the air-fuel mixture to the vicinity of the spark plug 10 more stably. A reentrant shape is more preferable.

  In the present embodiment, the inner wall surface 12a is inclined along the fuel spray toward the center of the combustion chamber 4 by an angle e with respect to the vertical line. As a result, the collision of the fuel spray with the annular groove 12 is softened, and the air-fuel mixture formed is smoothly rolled up along the bottom surface 12b and the outer wall surface 12c of the annular groove 12. As a result, the air-fuel mixture can be formed more evenly.

  In addition, the piston peripheral edge portion 13 was formed by the surface 13a, the surface 13b, and the surface 13c. By forming this tapered surface, the compression ratio of the cylinder can be increased, leading to an improvement in the performance of the internal combustion engine.

  Further, since the height of the piston peripheral portion 13 is formed to be equal to or lower than the height of the upper end f of the outer wall surface 12c when viewed in the longitudinal section of the piston, the gas flow generated in the combustion chamber 4 flows from the piston peripheral portion 13 to the annular groove 12. Intrusion can be effectively suppressed.

  Furthermore, the upper end g of the inner wall surface 12a of the annular groove 12 and the upper end f of the outer wall surface 12c were formed at the same height when viewed in the longitudinal section of the piston. That is, the height of the piston peripheral edge portion 13 was made to coincide with the height of the central surface 11. Thereby, it is possible to more effectively suppress the gas flow generated in the cylinder from entering the annular groove 12. It should be noted that the same effect is exhibited even when the height of the piston peripheral edge portion 13 is formed lower than the height of the central surface 11.

  A second embodiment will be described.

  FIG. 7 shows a schematic view of the piston in the present embodiment.

  The present embodiment is characterized in that the piston peripheral edge portion 13 is parallel to the center plane 11. Moreover, in this embodiment, the piston peripheral part 13 and the center surface 11 are formed in the same height seeing in a piston longitudinal cross-section. That is, g, f, and h in the figure are located on the same plane.

  The effect by 2nd Embodiment is demonstrated.

  In the present embodiment, the surface area of the piston crown surface can be reduced as compared with the first embodiment. That is, the S / V ratio, which is the ratio between the surface area and the volume of the combustion chamber, can be made smaller than in the first embodiment, and cooling loss can be suppressed. Therefore, in addition to the effects of the first embodiment, the performance of the internal combustion engine can be improved.

  A third embodiment will be described.

  FIG. 8 shows a schematic view of the piston in the present embodiment.

  In this embodiment, two annular grooves of the above embodiment are provided on the concentric circles. That is, the inner annular groove 12-i composed of the inner wall surface 12a-i, the bottom surface 12b-i, and the outer wall surface 12c-i, and the outer annular groove composed of the inner wall surface 12a-o, the bottom surface 12b-o, and the outer wall surface 12c-o. 12-o. Here, the piston crown surface inside the inner annular groove 12-i is the center surface 11-i. In FIG. 8, the upper end f of the outer wall surface 12c-i of the inner annular groove 12-i is connected to the upper end h of the inner wall surface 12a-o of the outer annular groove 12-o through a flat annular surface 11-o. ing. Further, the outer wall surface 12c-o of the outer annular groove 12-o is connected to the piston peripheral portion 13 at its upper end i.

  The piston peripheral portion 13 is the center of the combustion chamber 4 at an angle e with respect to the vertical line so that the height decreases from the end i on the piston center side toward the end j on the piston peripheral side as viewed in the longitudinal section of the piston. It is a tapered surface inclined in the direction.

  In the present embodiment, the upper end g of the inner wall surface 12a-i of the inner annular groove 12-i and the upper end f of the outer wall surface 12c-i have the same height when viewed in the longitudinal section of the piston, and the outer annular groove 12 The upper end h of the inner wall surface 12a-o and the upper end i of the outer wall surface 12c-o have the same height.

  Further, in the present embodiment, the outer wall surfaces of the inner and outer two annular grooves have a reentrant shape that is inclined from the bottom of each annular groove toward the center of the combustion chamber 4. The inclination k of the outer annular groove 12-o with respect to the vertical line of the outer wall surface 12c-o is larger in the center direction of the combustion chamber 4 than the inclination d of the inner annular groove 12-i with respect to the vertical line of the outer wall surface 12c-i. It has an inclined shape.

  Furthermore, the depth m from the center surface 11-i of the bottom surface 12b-i of the inner annular groove 12-i is compared with the depth n from the center surface 11-i of the bottom surface 12b-o of the outer annular groove 12-o. It has a shallow shape.

  In the fuel injection in this embodiment, for example, when the engine load is relatively low, the fuel spray collides with the inner annular groove 12-i, and when the engine load is relatively high, the outer annular groove 12-o. The fuel spray is set to collide with.

  In the operation region where the engine load increases and any one of the annular grooves cannot form an air-fuel mixture having the required size, fuel injection is performed twice during the compression stroke. That is, fuel is injected so that the first fuel injection collides with the outer annular groove 12-o and the second fuel injection collides with the inner annular groove 12-i.

  A case where fuel injection is performed twice will be described with reference to the schematic diagram of FIG.

  First, the first fuel injection is performed in the middle of the compression stroke, and the fuel spray injected by the fuel injection collides with the inner wall surface 12a-o of the outer annular groove 12-o ((a) in FIG. 9). Thereafter, the fuel spray is directed from the outer wall surface 12c-o to the upper side of the combustion chamber 4 via the bottom surface 12b-o by the penetrating force ((b) of FIG. 9), and the air-fuel mixture without unevenness while entraining the surrounding air. Form lumps. The size of the air-fuel mixture formed at this time is relatively large depending on the size of the outer annular groove 12-o.

  The second fuel injection is performed so as to collide with the inner annular groove 12-i at the end of the compression stroke, and the fuel spray by this fuel injection collides with the inner wall surface 12a-i of the inner annular groove 12-i (see FIG. 9 (c)). The impinging fuel spray is directed upward from the outer wall surface 12c-i to the upper side of the combustion chamber 4 via the bottom surface 12b-i of the inner annular groove 12-i (FIG. 9 (d)). A relatively small air-fuel mixture is formed near the center.

  Then, the air-fuel mixture formed at the time of the first fuel injection and the air-fuel mixture formed at the time of the second fuel injection form a non-uniform air-fuel mixture having a desired size in the vicinity of the spark plug 10 of the combustion chamber 4. (E in FIG. 9).

  The effect by 3rd Embodiment is demonstrated.

  By providing two inner and outer annular grooves on a concentric circle, in addition to the effect of the first embodiment, it becomes possible to adjust the size of the uniform air-fuel mixture formed by one piston, which is more stable Stratified combustion can be performed.

  In particular, in this embodiment, when the engine load is relatively low, the fuel spray collides with the inner annular groove 12-i, and when the engine load is relatively high, the fuel spray collides with the outer annular groove 12-o. Thus, an air-fuel mixture having a size required for each engine load can be formed without being affected by the in-cylinder gas flow and without any unevenness.

  In the operation region where the engine load increases and any one of the annular grooves cannot form an air-fuel mixture having a required size, fuel injection is performed twice during the compression stroke. That is, the fuel spray from the first fuel injection collides with the outer annular groove 12-o, and the fuel spray from the second fuel injection collides with the inner annular groove 12-i. As a result, even when the engine load increases, a desired air-fuel mixture having a uniform size can be formed.

  Further, in the present embodiment, the outer wall surface 12c-o of the outer annular groove 12-o is inclined more toward the center of the combustion chamber 4 with respect to the vertical line than the outer wall surface 12c-i of the inner annular groove 12-i. As a result, the air-fuel mixture formed by the outer annular groove 12-o can be more effectively supplied to the vicinity of the spark plug 10.

  Further, since the inner annular groove 12-i is shallower than the outer annular groove 12-o from the center plane 11-i, the air-fuel mixture formed by the inner annular groove 12-i is compared. Small. Therefore, more stable stratified combustion can be performed even at extremely low loads such as idle.

  A fourth embodiment will be described.

  FIG. 10 shows a schematic view of the piston in the present embodiment.

  This embodiment is characterized in that two concentric annular grooves are provided on the flat piston crown surface as in the above embodiment. In particular, the depth n from the center surface 11-i of the bottom surface 12b-i of the inner annular groove 12-i is larger than the depth m from the center surface 11-i of the bottom surface 12b-o of the outer annular groove 12-o. It is characterized by being deep.

  The effect by 4th Embodiment is demonstrated.

  According to the present embodiment, a relatively large air-fuel mixture can be formed by the inner annular groove 12-i. For this reason, more stable stratified combustion can be performed from low load to medium load.

  When two inner and outer concentric annular grooves are provided on the crown surface of the piston, when the inner diameter of the inner annular groove 12-i decreases, the center surface 11-i disappears as shown in FIG. It is possible. Even in this case, since the annular surface 11-o positioned between the inner annular groove 12-i and the outer annular groove 12-o can suppress the intrusion of the in-cylinder gas flow into the annular groove, the present invention intends. By the way.

  It goes without saying that the present invention is not limited to the above-described embodiments, and includes various modifications and improvements that can be made within the scope of the technical idea thereof.

It is a block diagram of the direct injection type internal combustion engine in this invention. It is the schematic of a hole nozzle injection valve. It is the schematic of a swirl nozzle injection valve with a notch. It is the schematic of the piston in 1st Embodiment. It is the schematic of fuel spray in this invention, and air-fuel | gaseous mass formation. It is the schematic which showed the relationship between the gas flow in a cylinder, and fuel spray. It is the schematic of the piston in 2nd Embodiment. It is the schematic of the piston in 3rd Embodiment. It is the schematic of formation of the fuel spray and the air-fuel | gaseous mass at the time of performing fuel injection twice in 3rd Embodiment. It is the schematic of the piston in 4th Embodiment. It is the schematic of the piston in 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Cylinder block 3 Piston 4 Combustion chamber 5 Intake valve 6 Intake port 7 Exhaust valve 8 Exhaust port 9 Fuel injection valve 10 Spark plug 11 Center surface 12 Annular groove 13 Piston peripheral part 14 Engine control unit (ECU)
15 Gasket

Claims (13)

In a direct injection type internal combustion engine having an ignition plug and a fuel injection valve at the upper part of the combustion chamber,
An annular groove is formed on the flat piston crown,
The fuel is injected when the radial fuel spray injected from the fuel injection valve collides with the annular groove during the compression stroke, and an air-fuel mixture is formed in the vicinity of the spark plug. In-cylinder direct injection internal combustion engine.   2. The direct injection internal combustion engine according to claim 1, wherein an outer wall surface of the annular groove has a reentrant shape inclined from a bottom portion of the annular groove toward a center direction of the combustion chamber.   The inner wall surface of the annular groove is inclined from the bottom of the annular groove toward the center of the combustion chamber along the fuel spray injected by the fuel injection valve. 2. The direct injection type internal combustion engine according to 2.   4. The piston crown surface outside the annular groove is formed below the height of the upper end of the outer wall surface of the annular groove when viewed in a piston longitudinal section. The direct injection type internal combustion engine described in 1.   4. The piston crown surface outside the annular groove is formed by a flat surface parallel to the piston crown surface inside the annular groove. An in-cylinder direct injection internal combustion engine according to claim 1.   The said piston crown surface outside the said annular groove is formed below the height of the said piston crown surface inside the said annular groove seeing in a piston longitudinal cross section. In-cylinder direct injection internal combustion engine.   7. The piston crown surface outside the annular groove is formed in a taper shape having at least a part thereof having a conical apex above the combustion chamber when viewed in a longitudinal section of the piston. The direct injection type internal combustion engine described in 1.   The in-cylinder direct injection internal combustion engine according to claim 1, wherein the annular groove is provided in two concentric circles inside and outside.   9. In-cylinder direct injection according to claim 8, wherein fuel is injected into the inner annular groove when the engine load is relatively low, and fuel is injected into the outer annular groove when the engine load is relatively high. Injection-type internal combustion engine.   When the engine load is in a specific operating range, fuel is injected twice during the compression stroke, and the first fuel injection collides with the outer annular groove, and the second fuel injection collides with the inner annular groove. The direct injection internal combustion engine according to claim 8 or 9, wherein the fuel is injected as described above.   The outer wall surfaces of the two inner and outer annular grooves each have a reentrant shape inclined from the bottom of the two inner and outer annular grooves toward the center of the combustion chamber, and the outer wall surfaces of the outer annular grooves are perpendicular to each other. The in-cylinder direct injection internal combustion engine according to claim 8, wherein the inclination formed by the inner annular groove is larger than the inclination formed by the outer wall surface of the inner annular groove formed by a vertical line.   9. The cylinder according to claim 8, wherein a depth of a bottom surface of the inner annular groove from the piston crown surface is shallower than a depth of a bottom surface of the outer annular groove from the piston crown surface. Internal direct injection internal combustion engine.   The cylinder according to claim 8, wherein a depth of a bottom surface of the inner annular groove from the piston crown surface is deeper than a depth of a bottom surface of the outer annular groove from the piston crown surface. Internal direct injection internal combustion engine.