JP3692749B2 - Piston for in-cylinder internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piston of a cylinder injection internal combustion engine represented by a gasoline engine, in particular, a cylinder capable of both homogeneous combustion and stratified combustion using a tumble component and a swirl component generated in a cylinder combustion chamber. The present invention relates to an improvement of a piston of an injection type internal combustion engine.
[0002]
[Prior art]
A so-called homogeneous combustion is performed by forming a substantially homogeneous air-fuel ratio mixture in the cylinder combustion chamber at the time of fully open output, etc., and in the low load region, a relatively rich mixture is only applied to a part of the combustion chamber, that is, only near the spark plug. Various in-cylinder injection internal combustion engines that perform stratified combustion so that an average air-fuel ratio can be obtained to be very large have been proposed.
[0003]
As a piston of a direct injection internal combustion engine capable of stratified lean combustion, for example, a piston described in Japanese Patent Publication No. 8-35429 is known. In the internal combustion engine described in this publication, a non-circular bowl (cavity) eccentric to the piston outer circle is formed at the top of the piston, and fuel can be injected and supplied toward the bowl at the top dead center of the piston. The fuel injection valve is arranged as described above. The piston top has a reentrant configuration so that fuel and swirl are contained in the bowl. In addition, one of the pair of intake ports is configured as a helical port, and an air control valve that opens and closes the other intake port is provided.
[0004]
That is, in the internal combustion engine disclosed in this publication, at the time of lean combustion, the air control valve is closed and fresh air is introduced only from one helical port to generate a strong swirl in the combustion chamber. Since this swirl is introduced into the bowl as the piston rises, a flammable mixture is formed in the bowl by injecting fuel into the bowl late in the compression stroke, and the spark plug is formed by the swirl in the bowl. Carried around. Therefore, ignition is performed by igniting at an appropriate timing.
[0005]
Japanese Patent Application Laid-Open No. 5-231155 discloses a substantially hemispherical deep bowl (deep dish portion) that is eccentric with respect to the piston outer circle at the top of the piston, and a spark plug on a part of the outer periphery of the bowl. In-cylinder internal combustion engine pistons having plug pockets partially recessed in the radial direction so as to surround the cylinder are disclosed.
[0006]
[Problems to be solved by the invention]
In the case where the plug pocket is formed as in JP-A-5-231155, when the fuel injection amount is small as in stratified combustion, a large amount of fuel is collected in the vicinity of the spark plug to form a good combustible mixture. can do. However, when the fuel injection amount is large as in homogeneous combustion, the sprayed fuel stays around the spark plug, the ignitability deteriorates, and the fuel film attached to the bowl wall surface does not evaporate completely. Diffusing causes problems such as smoke and fouling of the spark plug.
[0007]
With respect to such a problem, in the one described in Japanese Patent Publication No. 8-35429, the bowl shape is non-circular in plan view, and the spark plug is brought close to a substantially straight section in the bowl wall surface. The fuel spray is prevented from staying around the spark plug. However, when the bowl is made non-circular in this way, the bowl volume becomes relatively large, the compression ratio at the time of homogeneous combustion becomes low, and there is a possibility that the fully open performance is lowered.
[0008]
In addition, in both publications, since the injection direction by the fuel injection valve is deflected to the swirl upstream side of the spark plug, it is necessary to narrow the spray angle, which is a major factor that lowers the fully open performance by homogeneous combustion It becomes.
[0009]
The present invention provides a piston for an in-cylinder injection internal combustion engine that can effectively suppress generation of smoke and smoldering of a spark plug in a combustion chamber while achieving both high-level stratified lean combustion and homogeneous combustion. It is aimed.
[0010]
[Means for Solving the Problems]
A cylinder injection internal combustion engine according to the invention of claim 1 is directed to a cylinder in which a piston moves up and down, a cylinder head in which an intake valve and an exhaust valve are disposed, and a substantially center of the cylinder when viewed from the cylinder axial direction. A fuel injection valve which is disposed on the intake valve side in a posture and directly injects fuel into a combustion chamber formed between the cylinder head and the top of the piston, and an ignition plug positioned substantially in the center of the cylinder when viewed from the axial direction And injecting fuel in the vicinity of the intake stroke in a state where a tumble flow component is applied to the combustion chamber, and realizing fuel injection near the compression stroke in a state where a swirl component is applied in the combustion chamber It is the structure which realizes stratified combustion by performing.
[0011]
In the piston according to the present invention, a substantially round bowl as viewed from the axial direction is recessed at the top of the piston, and the center of the bowl as viewed from the axial direction is located within the true circle range. Eccentric to the intake valve side with respect to the plug, and eccentric to the upstream side of the swirl swirling in the combustion chamber along the inner wall surface of the cylinder with reference to a line connecting the spark plug and the fuel injection valve , And the deepest bottom part of the said bowl bottom face is eccentric to the line side which connects the said ignition plug and the said fuel injection valve with respect to the said bowl center, It is characterized by the above-mentioned.
[0012]
During stratified combustion, swirl is generated in the combustion chamber by, for example, fresh air introduced from one intake port. This swirl is carried into the bowl as the piston rises. Here, since the bowl is substantially round when viewed from the axial direction, a sufficient swirl can be secured in the bowl. In the latter half of the compression stroke, the fuel spray injected from the fuel injection valve toward the spark plug in the center of the cylinder collides with the bottom of the bowl and the opposing peripheral wall of the bowl, evaporates and atomizes, and as a whole It moves to the spark plug side while diffusing and evaporating on the swirl, and forms a combustible mixture around the spark plug.
[0013]
Here, when viewed from the axial direction, the center of the bowl is eccentric to the intake valve side with respect to the ignition plug, and is eccentric to the swirl upstream side from the line connecting the ignition plug and the fuel injection valve. That is, the bowl has a shape in which the downstream region of the spark plug relatively expands in the flow direction of the swirl swirling in the bowl. As a result, the air-fuel mixture (fuel) riding on the swirl swirling in the bowl and passing through the periphery of the spark plug is diffused and vaporized well without staying in the downstream region of the spark plug having a relatively large internal volume. . In addition, the surface area of the peripheral wall of the bowl where the fuel that has passed through the spark plug is likely to adhere is substantially enlarged, so the thickness of the liquid fuel film adhering to the peripheral wall of the bowl is reduced and the evaporation time is shortened. It becomes. Therefore, the generation of smoke, smoldering spark plugs, and the like are effectively suppressed.
[0014]
In homogeneous combustion, a tumble flow is generated by the fresh air flowing into the combustion chamber through the intake valve, and fuel is injected in the vicinity of the intake stroke.
[0015]
According to a second aspect of the present invention that further embodies the first aspect of the invention, the cylinder head includes an intake side inclined surface on which a pair of intake valves are disposed and an exhaust valve side on which a pair of exhaust valves are disposed. It has a pent roof shape having an inclined surface, and the piston top portion is substantially parallel to the intake valve side piston inclined surface and the exhaust valve side inclined surface inclined so as to be substantially parallel to the intake valve side inclined surface. An exhaust valve side piston inclined surface that is inclined in a straight line is formed.
[0016]
According to a third aspect of the present invention, in the peripheral wall portion of the bowl, the portion on the downstream side of the swirl from the line connecting the spark plug and the fuel injection valve directly interferes with the fuel spray injected during the compression stroke. In order to avoid this, the amount of eccentricity of the bowl is set.
[0017]
According to a fourth aspect of the present invention, the center of the bowl as viewed from the axial direction swirls in the combustion chamber along the inner wall surface of the cylinder around the spark plug from a line connecting the spark plug and the fuel injection valve. It is characterized in that it is set at a position rotated by a predetermined amount in the direction opposite to the swirl turning direction .
[0018]
The invention according to claim 5 is characterized in that a portion of the peripheral wall portion of the bowl facing the fuel injection valve is formed in a reentrant shape.
[0019]
According to a sixth aspect of the present invention, a notch portion for avoiding direct interference of the fuel spray from the fuel injection valve is provided in a concave portion in the vicinity of the fuel injection valve in the outer peripheral edge portion of the bowl. It is characterized by having.
[0021]
【The invention's effect】
According to the first aspect of the present invention, the volume in the bowl and the surface area of the peripheral wall in the downstream region of the spark plug are relatively enlarged in the flow direction of the swirl swirling in the bowl. Therefore, during stratified combustion, the air-fuel mixture (fuel) that has passed around the spark plug is effectively diffused and vaporized, and the liquid film of fuel adhering to the peripheral wall of the bowl is thinned, shortening the evaporation time, Therefore, it is possible to effectively prevent the generation of smoke and the accompanying smoldering of the spark plug.
[0022]
Further, since the bowl has a substantially perfect circle shape when viewed from the axial direction, the bowl volume is relatively small. Therefore, the compression ratio can be set high, and the fully open performance during homogeneous combustion using a tumble flow can be improved. That is, the fully open performance by homogeneous combustion and stratified lean combustion can be made compatible at a higher level.
[0023]
According to the invention of claim 2, at the piston top dead center, the intake valve side piston inclined surface and the exhaust valve side piston inclined surface are slightly different from each other on the cylinder head side intake valve side inclined surface and exhaust side inclined surface. The bowl occupies most of the space facing through the gap and remaining in the combustion chamber. Therefore, during stratified combustion, swirl and air-fuel mixture are well contained in the bowl, and combustion proceeds well in the bowl.
[0024]
Further, because the bowl is eccentric to the intake valve side and the swirl upstream side, the peripheral wall portion of the bowl facing the fuel injection valve is located closer to the center of the cylinder when viewed from the axial direction, and the surface area thereof is pent rule. It becomes relatively large depending on the shape. For this reason, the liquid film thickness of the fuel adhering to the bowl peripheral wall portion is further reduced.
[0025]
According to the invention of claim 3, the fuel spray injected during the compression stroke directly interferes with the swirl downstream side of the line connecting the spark plug and the fuel injection valve in the bowl peripheral wall. Therefore, there is no possibility that a large amount of fuel adheres to this portion and causes smoke generation or spark plug contamination.
[0026]
According to the invention of claim 4, the axial relative positional relationship of the bowl with respect to the cylinder and the spark plug is the same as when the bowl center is not eccentric with respect to the line connecting the spark plug and the fuel injection valve, for example. The same level of swirl can be secured as in such a case.
[0027]
According to the fifth aspect of the invention, the fuel adhering to the peripheral wall portion of the bowl facing the fuel injection valve and the air-fuel mixture passing through the periphery of this portion jump out to the external combustion chamber beyond the outer peripheral edge of the bowl. Is prevented. That is, at the time of stratified combustion, the fuel, the air-fuel mixture and further the swirl can be reliably contained in the bowl.
[0028]
By the way, when the bowl is eccentric to the swirl upstream side from the line connecting the spark plug and the fuel injection valve as in the invention of claim 1 or 2, the outer peripheral edge of the bowl is the fuel injection valve according to the eccentric amount. Therefore, the fuel spray from the fuel injection valve may interfere with the peripheral edge of the bowl. Therefore, in the invention of claim 6, a notch is formed in the peripheral edge of the bowl adjacent to the fuel injection valve to reliably prevent the above-mentioned fuel adhesion.
[0029]
Furthermore , according to the invention of claim 1, the radius of curvature and the surface area in the region downstream of the spark plug in the flow direction of the swirl swirling in the bowl in the bowl bottom surface are relatively large. Therefore, the air-fuel mixture that has passed through the spark plug is diffused more favorably, and the liquid film of the fuel adhering to the bottom surface of the bowl is thinned, thereby realizing better stratified combustion.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0031]
First, the configuration of a direct injection internal combustion engine in which the piston 4 of the present invention is used will be described with reference to FIGS. As illustrated, a plurality of cylinders 3 are arranged in series on the cylinder block 1, and a cylinder head 2 is fixed so as to cover the upper surface thereof. A piston 4 is fitted in the cylinder 3 so as to be slidable and movable up and down, and a combustion chamber 11 is defined between the top 21 of the piston 4 and the cylinder head 2.
[0032]
The cylinder head 2 is configured as a so-called pent roof type, and a pair of intake valves 5 are arranged on one inclined surface 11a, and a pair of exhaust valves 6 are arranged on the other inclined surface 11b. An ignition plug 7 is disposed at a substantially central position in the axial direction of the cylinder 3 surrounded by the pair of intake valves 5 and the pair of exhaust valves 6.
[0033]
The cylinder head 2 is formed with a pair of intake ports 8 corresponding to the pair of intake valves 5 independently of each other. That is, the pair of intake ports 8 do not merge in the cylinder head 2 and open independently on the side surfaces of the cylinder head 2. An exhaust port 9 is formed corresponding to the exhaust valve 6.
[0034]
The electromagnetic fuel injection valve 10 having a substantially cylindrical shape is disposed on the lower surface portion of the cylinder head 2 near the side wall of the cylinder 3 on the intake valve 5 side, and is attached in such a posture that its central axis is directed obliquely downward. In particular, as shown in FIG. 2, the fuel injection valve 10 is disposed between the two intake valves 5, and the spray axis is directed to the center in the cylinder axial direction where the spark plug 7 is located.
[0035]
As will be described later, a bowl-shaped bowl 12 having a true circle shape when viewed from the cylinder axial direction is formed on the top portion 21 of the piston 4. When the piston 4 is near top dead center, the fuel injection is performed. The spray axis of the valve 10 is directed to the bowl 12.
[0036]
The pair of intake ports 8 are connected to a pair of intake passages 14a and 14b formed independently on the intake manifold 13 side. A butterfly valve type air control valve 15 for opening and closing the intake passage 14b is interposed in the one intake passage 14b. The air control valve 15 is controlled to open and close according to engine operating conditions by a drive mechanism (not shown) via a shaft 16. In the state where the air control valve 15 is closed, fresh air flows only through the intake port 8 connected to the other intake passage 14a. However, the intake port 8 is not a helical port, but is a loosely curved substantially straight line. Port shape.
[0037]
The basic operation of the internal combustion engine will be described. The homogeneous combustion in which a homogeneous air-fuel mixture is formed in the combustion chamber 11 and ignited at the full load of the engine or in a region where the air-fuel ratio is relatively small in the lean combustion region. Is done. More specifically, during the homogeneous combustion, the air control valve 15 is controlled to be in an open state, and fresh air is introduced into the combustion chamber 11 from both the pair of intake ports 8. Thereby, a strong tumble flow (longitudinal vortex) is generated in the combustion chamber 11, and the fuel injected and supplied into the combustion chamber 11 during the intake stroke by this tumble flow does not stay in the bowl 12. Actively diffuses and homogenizes.
[0038]
On the other hand, in a lean combustion region where the air-fuel ratio is very large in a low load region, stratified lean combustion is performed that enables reliable ignition by stratification of the air-fuel mixture. During this stratified lean combustion, the air control valve 15 is closed, and fresh air flows into the combustion chamber 11 from only one intake port 8. Thereby, in the combustion chamber 11, the tumble component is relatively weakened, and the swirl component S1 along the horizontal direction is strongly generated. Therefore, as shown in FIG. 5A, the fuel injected from the fuel injection valve 10 toward the bowl 12 in the latter half of the compression stroke enters the bowl 12 at the top of the piston 4 as shown in FIG. 5B. It rides on the swirl S2 that has flowed in and moves toward the spark plug 7 to form an air-fuel mixture that can be ignited around the spark plug 7.
[0039]
Next, with reference to FIGS. 1 and 3 to 5, the configuration and operation of the piston 4 according to the first embodiment, particularly the top portion 21 thereof, will be described in detail.
[0040]
An intake valve side piston which is a plane substantially parallel to the intake valve side inclined surface 11a and the exhaust valve side inclined surface 11b of the pent roof type cylinder head 2 shown in FIG. An inclined surface 22 and an exhaust valve side piston inclined surface 23 are formed. For this reason, when the piston 4 is at the top dead center, the clearance generated between the inclined surfaces 11a, 11b on the cylinder head 2 side and the piston inclined surfaces 22, 23 becomes very small, and the volume remaining in the combustion chamber 11 is reduced. The bowl 12 occupies most of it. The highest ridge portion in the top portion 21 extends to the vicinity of the piston 4 outer circle along the piston pin axial direction.
[0041]
The bowl 12 is recessed in a range centered on the intake valve side piston inclined surface 22. That is, the bowl 12 has a true circle shape when viewed on the plane of the piston 4 (cylinder axial direction) and has a diameter slightly larger than the radius of the piston 4, and a part of the bowl 12 is an exhaust valve side piston inclined surface. 23 is approaching. The spark plug 7 is set so as to enter the bowl 12 when the piston 4 is at the top dead center and to be positioned in the vicinity of the outer peripheral portion of the bowl 12.
[0042]
In the present embodiment, as shown in FIG. 3, the center 40 of the bowl 12 when viewed from the axial direction is on the intake valve 5 side (lower side in FIG. 3) with respect to the spark plug 7 located within the true circular range. And is more eccentric than the line L connecting the spark plug 7 and the fuel injection valve 10 to the upstream side of the swirl S1 turning inside the combustion chamber 11 along the inner wall surface of the cylinder 3. That is, the bowl center 40 is set at a position rotated from the line L connecting the spark plug 7 and the fuel injection valve 10 by a predetermined angle θ1 about the spark plug 7 toward the upstream side of the swirl S1. Accordingly, the bowl 12 has a substantially enlarged region on the downstream side of the spark plug 7 in the flow direction of the swirl S2 swirling in the bowl 12 as shown in FIG.
[0043]
As described above, when the center 40 of the bowl 12 is eccentric to the upstream side of the swirl S1, the outer peripheral edge (opening edge) of the bowl 12 is moved away from the fuel injection valve 10, and fuel spray from the fuel injection valve 10 is prevented. Since there is a possibility of direct interference, in this embodiment, an appropriate notch 41 that faces the bowl 12 side is recessed in the outer peripheral edge of the bowl 12 adjacent to the fuel injection valve 10, Avoids fuel spray interference.
[0044]
In addition, the deepest bottom portion 42 that is deepest recessed in the bowl 12 is formed in a substantially planar shape, and the bowl 12 is smoothly curved from the deepest bottom portion 42 to the edge of the bowl opening through the peripheral wall portion of the bowl. It is formed in a substantially bowl shape. In addition, you may form the whole wall part of the bowl 12 including the deepest bottom part 42 in smooth spherical shape.
[0045]
Then, a portion 43 facing the fuel injection valve 10 in the peripheral wall portion of the bowl 12, in other words, a portion 43 from the periphery of the spark plug 7 to the downstream side of the swirl as seen from the axial direction is a reentrant as shown in FIG. It is formed into a shape.
[0046]
Further, in the peripheral wall portion of the bowl 12, the portion 44 on the upstream side of the swirl S1 with respect to the line L connecting the fuel injection valve 10 and the spark plug 7 directly receives the fuel spray F1 injected during the compression stroke. The amount of eccentricity of the bowl 12 is set so as not to interfere.
[0047]
5A to 5C are plan views of the piston 4 showing the stratified combustion process. In the latter half of the compression stroke shown in FIG. 5 (A), the fuel spray F1 is injected from the fuel injection valve 10 into the bowl 12, and the swirl S1 swirling in the combustion chamber 11 as the piston 4 rises is in the bowl. 12 is introduced. As shown in FIG. 5B, the fuel spray F1 rides on the swirl S2 in the bowl 12 and moves toward the spark plug 7 while diffusing and vaporizing, thereby forming a combustible mixture F2 around the spark plug 7. Ignition is performed by igniting this combustible mixture at an appropriate timing. Then, as shown in FIG. 5C, the air-fuel mixture F3 that has passed around the spark plug 7 flows together with the remaining liquid fuel while diffusing from the spark plug 7 to the swirl S2 downstream region.
[0048]
Here, in the present embodiment, the center 40 of the bowl 12 is eccentric to the intake valve 5 side with respect to the spark plug 7 and is upstream of the swirl S1 from the line L connecting the spark plug 7 and the fuel injection valve 10. Accordingly, the bowl 12 has a relatively larger downstream area than the spark plug 7 in the direction of flow of the swirl S2 in the bowl 12. As a result, at the time of stratified combustion in which fuel injection is performed in the vicinity of the compression stroke, the air-fuel mixture (fuel) that has passed around the spark plug 7 is diffused and vaporized without stagnation. Further, the peripheral wall portion of the bowl 12 to which the fuel that has passed around the spark plug 7 easily adheres has a substantially enlarged shape, the thickness of the fuel liquid film adhering to the peripheral wall portion of the bowl 12 is reduced, and evaporation is performed in a short time. Can be completed. As a result, it is possible to effectively suppress the generation of smoke and the smoldering of the spark plug 7.
[0049]
Moreover, since the bowl 12 occupies most of the combustion chamber 11 near the top dead center of the piston as described above, the swirl S2 and the air-fuel mixture can be well contained in the bowl 12.
[0050]
Furthermore, since the bowl 12 is substantially circular in plan view, the volume of the bowl 12 can be made relatively small and the compression ratio can be set sufficiently high. Further, the swirl S2 having a sufficient strength can be stored in the bowl 12 during stratified combustion. That is, the fully open performance by homogeneous combustion and stratified lean combustion can be made compatible at a higher level.
[0051]
In addition, because the bowl 12 is eccentric, the peripheral wall portion 43 of the bowl 12 facing the fuel injection valve 10 is located closer to the center, and the surface area thereof becomes relatively large according to the pent roof shape. Accordingly, the thickness of the fuel liquid film adhering to the portion 43 is reduced, and the fuel evaporation time is shortened.
[0052]
Further, since the center 40 of the bowl 12 is set at a position rotated by a predetermined angle θ1 about the spark plug 7, the relative axial relationship of the bowl 12 with respect to the cylinder 3 and the spark plug 7 is, for example, the bowl center 40 being ignited. This is the same as the case where the plug 7 and the fuel injection valve 10 are located on the line L, and the same level of swirl can be secured as in such a case.
[0053]
Further, since the peripheral wall portion 43 of the bowl 12 facing the fuel injection valve 10 has a reentrant shape, the fuel adhering to the portion 43 and the air-fuel mixture passing near the portion 43 exceed the outer peripheral edge of the bowl 12. Jumping out into the external combustion chamber 11 is effectively prevented. That is, at the time of stratified combustion, the fuel, the air-fuel mixture, and further the swirl can be surely contained in the bowl 12, and the stratified combustion becomes good.
[0054]
Next, FIGS. 6 and 7 show a second embodiment of the piston 4 according to the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.
[0055]
In this embodiment, the center 40 of the bowl 12 is set at the same position as in the first embodiment, whereas the deepest bottom portion 45 of the bowl 12 has a spark plug 7 and a fuel injection valve with respect to the bowl center 40. 10 is eccentric to the line L side (right side in FIG. 6). More specifically, the center 45a of the deepest bottom 45 is set on the line L. In other words, in the bottom surface of the bowl 12, the surface area and the radius of curvature of the downstream region 46 of the spark plug 7 are relatively large in the flow direction of the swirl in the bowl 12. Accordingly, the air-fuel mixture passes and diffuses well around the region 46 without stagnation, and the liquid film of the fuel adhering to the region 46 can be thinned to realize better stratified combustion.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a configuration of a direct injection internal combustion engine according to the present invention.
FIG. 2 is a bottom view showing a state in which the cylinder head of FIG. 1 is viewed from the lower surface side.
FIG. 3 is a plan view showing a first embodiment of a piston according to the present invention.
4 is a cross-sectional view taken along the line AA in FIG. 3;
FIG. 5 is a plan view of a piston showing a process of stratified combustion.
FIG. 6 is a plan view showing a second embodiment of the piston according to the present invention.
7 is a cross-sectional view taken along line BB in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 4 ... Piston 7 ... Spark plug 10 ... Fuel injection valve 11 ... Combustion chamber 12 ... Bowl 21 ... Top part 22 ... Intake valve side piston inclined surface 23 ... Exhaust valve side piston inclined surface 40 ... Bowl center 41 ... Notch part 42 ... Deepest bottom part 43, 44 ... Bowl peripheral wall part

Claims (6)

A cylinder in which a piston moves up and down, a cylinder head in which an intake valve and an exhaust valve are disposed, and an intake valve side arranged in a posture oriented substantially in the center when viewed from the cylinder axial direction. A fuel injection valve that directly injects fuel into the combustion chamber formed between the spark plug and a spark plug positioned substantially in the center of the cylinder when viewed from the axial direction, with a tumble flow component applied to the combustion chamber In-cylinder injection that achieves homogeneous combustion by injecting fuel near the intake stroke at the same time and stratified combustion by injecting fuel near the compression stroke with the swirl component applied to the combustion chamber In the internal combustion engine,
A substantially round bowl as viewed from the axial direction is recessed at the top of the piston, and the center of the bowl as viewed from the axial direction is on the intake valve side with respect to the spark plug located within the true circular range. And eccentric to the upstream side of the swirl that swirls in the combustion chamber along the inner wall surface of the cylinder with reference to a line connecting the ignition plug and the fuel injection valve ,
The deepest bottom portion of the bottom surface of the bowl is eccentric to the line connecting the spark plug and the fuel injection valve with respect to the center of the bowl . The cylinder head has a pent roof shape having an intake side inclined surface on which a pair of intake valves are arranged and an exhaust valve side inclined surface on which a pair of exhaust valves are arranged,
An intake valve side piston inclined surface inclined so as to be substantially parallel to the intake valve side inclined surface and an exhaust valve side piston inclined surface inclined so as to be substantially parallel to the exhaust valve side inclined surface are formed on the piston top portion. The piston of the direct injection internal combustion engine according to claim 1, wherein the piston is provided.   In the peripheral wall portion of the bowl, the portion on the downstream side of the swirl from the line connecting the spark plug and the fuel injection valve does not directly interfere with the fuel spray injected during the compression stroke. The eccentric amount is set, The piston of the cylinder injection internal combustion engine according to claim 1 or 2. When viewed from the axial direction, the center of the bowl is opposite to the swirling direction of the swirl that swirls in the combustion chamber along the inner wall surface of the cylinder around the ignition plug from the line connecting the spark plug and the fuel injection valve. The piston of the direct injection internal combustion engine according to claim 1 or 2, wherein the piston is set at a position rotated by a predetermined amount in the direction.   The piston of the direct injection internal combustion engine according to claim 1 or 2, wherein a portion of the peripheral wall portion of the bowl facing the fuel injection valve is formed in a reentrant shape.   A notch for avoiding direct interference of fuel spray from the fuel injection valve is recessed in a portion adjacent to the fuel injection valve in the outer peripheral edge of the bowl. The piston of the cylinder injection type internal combustion engine of Claim 1 or 2.

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