JP4075471B2 - In-cylinder direct injection internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a center injection type in-cylinder direct injection internal combustion engine in which a fuel injection valve and a spark plug are arranged on or near a piston reciprocating axis, and more particularly to improvement of a cavity shape recessed in a piston crown surface.
[0002]
[Prior art]
As an in-cylinder direct injection internal combustion engine, Japanese Patent Laid-Open No. 2000-265841 discloses a center injection type engine in which a fuel injection valve and a spark plug are arranged on or near a piston reciprocating axis. In the crown of the piston, there is a recess (inner cavity) that is nearly axisymmetric with respect to the reciprocating axis of the piston, and a plurality of shallow dishes (outer cavities) intermittently around this dish. Is recessed.
[0003]
[Problems to be solved by the invention]
The shallow dish portion has a valve recess shape that avoids interference with the intake and exhaust valves, and is not axisymmetric with respect to the piston reciprocating axis. For this reason, when stratified combustion is performed using a shallow dish part, fuel spray injected into the shallow dish part may spill from between adjacent shallow dish parts, leading to deterioration in fuel consumption or increase in unburned HC. There is. Also, when stratified combustion is performed using the deep dish part, the side wall of the deep dish part is gently connected to the shallow dish part, so that the fuel spray injected into the deep dish part is transferred from the deep dish part to the shallow dish. It is easy to spill over to the part, and there is concern that the fuel consumption will deteriorate and the unburned HC will increase. The present invention has been made in view of such problems.
[0004]
[Means for Solving the Problems]
In the in-cylinder direct injection internal combustion engine of the present invention, a fuel injection valve and a spark plug are disposed on or near the piston reciprocating axis, and fuel is directly injected into the combustion chamber from the fuel injection valve. The air-fuel mixture is sparked by a spark spark plug. The outer surface of the piston crown has an outer cavity substantially in the shape of an axial rotator with respect to the piston reciprocating axis, and the outer cavity has a concave inner cavity in the shape of an axial rotator with respect to the piston reciprocating axis. Is done. Typically, stratified combustion is realized using the outer cavity in the stratified high load operation condition, and stratified combustion is realized using the inner cavity in the stratified low load operation condition.
[0005]
【The invention's effect】
Since both the outer cavity and the inner cavity have substantially the same shape as the axis of rotation with respect to the reciprocating axis of the piston, the stratified combustion is performed mainly using the outer cavity, and the stratified combustion is performed mainly using the inner cavity. In either case, it is possible to realize stratified combustion with good fuel efficiency and sufficiently suppressed emission of unburned HC.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0007]
FIG. 1 schematically shows an in-cylinder direct injection internal combustion engine according to the present invention. The combustion chamber 1 is defined by a cylinder head 2, a cylinder block 3, and a piston 4 that fits into a cylinder 3 a of the cylinder block 3. The cylinder head 2 is formed with an intake port 5 and an exhaust port 6 that open to the combustion chamber 1. The intake valve 7 and the exhaust valve 8 that open and close these ports 6 and 7 are driven using an intake valve cam 9 and an exhaust valve cam 10.
[0008]
The cylinder head 2 includes a fuel injection valve 11 that directly injects fuel into the combustion chamber 1 toward the crown surface 15 of the piston 4, and an ignition plug 12 that sparks and ignites the air-fuel mixture in the combustion chamber 1. In a state of facing the combustion chamber 1, they are arranged close to each other on or near the cylinder central axis, that is, the piston reciprocating axis 14. Here, in particular, the fuel injection valve 11 is disposed on the piston reciprocating axis 14, and the spark plug 12 is disposed in the vicinity of the fuel injection valve 11. The fuel injection valve 11 is a multi-hole type injection valve with strong directivity so that the change in the spray shape becomes small even when the cylinder pressure rises in the latter half of the compression stroke. The operations of the fuel injection valve 11 and the spark plug 12 are controlled by the engine control unit 13.
[0009]
The piston crown surface 15 has an upwardly convex (virtual) triangular pyramid shape, that is, a pent roof shape so as to follow the shape of the top surface of the pent roof type combustion chamber 1 formed in the cylinder head 2. An outer cavity 16 is recessed in the piston crown surface 15 so as to cut out the central portion thereof, and an inner cavity 17 is further recessed in the surface of the outer cavity 16. That is, a double cavity structure is formed in which two cavities 16 and 17 are formed concentrically on the piston crown surface 15.
[0010]
The outer cavity 16 has a substantially axial rotating body shape (axisymmetric shape, toroidal shape) with respect to the piston reciprocating axis 14. However, since the piston crown surface 15 in which the outer cavity 16 is recessed is not in the shape of a rotating shaft, when the piston crown surface 15 is viewed from above (combustion injection valve side), as shown in FIG. The opening 16k is not a perfect circle with the piston reciprocating axis 14 as the center. The inner cavity 17 has a shaft rotating body shape (axisymmetric shape, toroidal shape) with respect to the piston reciprocating axis 14, and as shown in FIG. 2, the piston crown surface 15 is viewed from above (combustion injection valve side). In this case, the opening 17k has a perfect circle centered on the piston reciprocating axis 14.
[0011]
FIG. 3 simply shows the spray behavior in the stratified high-load operation condition. The wall surface of the outer cavity 16 includes a first outer wall surface 16a, a second outer wall surface 16b continuous to the outer peripheral side of the first outer wall surface 16a, and a third outer wall surface 16c continuous to the second outer wall surface 16b. Can be divided. The first outer wall surface 16a is an inclined surface that becomes higher toward the central piston reciprocating axis 14, and has a virtual conical shape that is convex upward as a whole. The inner cavity 17 is recessed so as to cut out the central portion of the first outer wall surface 16a. The second outer wall surface 16b includes an outer curved surface that smoothly curves toward the third outer wall surface 16c, and a part thereof is a flat surface 16d that is substantially orthogonal to the piston reciprocating axis 14. The third outer wall surface 16c constitutes the outer wall surface of the entire outer cavity 16, and has a reentrant shape that inclines in a direction closer to the piston reciprocating axis 14 toward the upper side of the piston (upward in FIG. 3).
[0012]
The fuel spray injected from the fuel injection valve 11 has an upwardly convex hollow cone shape with the piston reciprocating axis 14 as the center. As shown in FIG. 3A, the fuel spray F1 under the stratified high load operation condition is set so as to collide obliquely with the first outer wall surface 16a. An angle θ1 formed by the (center) injection direction F2 of the spray F1 and a portion of the first outer wall surface 16a on the spray traveling direction side (radially outside the portion where the spray collides) is an obtuse angle (90 ° to 180 °). °) is set. Therefore, the fuel spray F1 collides with the first outer wall surface 16a at a gentle angle, and the fuel spray F1 after the collision does not inadvertently scatter and is along the first outer wall surface 16a. Good guidance to the second outer wall surface 16b side. Due to the outer curved surface of the second outer wall surface 16b, the spray is favorably guided along the third outer wall surface 16c.
The third outer wall surface 16c is an inclined surface that is inclined at an angle close to the spraying direction F2. Specifically, the angle θ2 formed by the extension line 16c ′ of the third outer wall surface 16c and the parallel line F2 ′ in the injection direction F2 is sufficiently small. However, the reentrant angle d of the third outer wall surface 16c with respect to the piston reciprocating axis 14 is smaller than the angle of the injection direction F2 with respect to the piston reciprocating axis 14. By such third outer wall surface 16c, the fuel spray is satisfactorily guided to go in the original injected direction. As a result, as shown in FIGS. 3B and 3C, a swirl flow F3 swirling like a vortex in the vertical direction along the piston reciprocating axis 14 is generated. The surrounding air is entrained by the swirling flow F3, and the air-fuel mixture generated above the outer cavity 16 becomes a homogeneous air-fuel mixture K1 having no concentration unevenness.
[0013]
The third outer wall surface 16c is an inclined surface that is inclined at an angle close to the spraying direction F2. Specifically, the angle θ2 formed by the extension line 16c ′ of the third outer wall surface 16c and the parallel line F2 ′ in the injection direction F2 is sufficiently small. However, the reentrant angle d of the third outer wall surface 16c with respect to the piston reciprocating axis 14 is smaller than the angle of the injection direction F2 with respect to the piston reciprocating axis 14. By such third outer wall surface 16c, the fuel spray is satisfactorily guided to go in the original injected direction. As a result, as shown in FIGS. 3B and 3C, a swirl flow F3 swirling like a vortex in the vertical direction along the piston reciprocating axis 14 is generated. The surrounding air is entrained by the swirling flow F3, and the air-fuel mixture generated above the outer cavity 16 becomes a homogeneous air-fuel mixture K1 having no concentration unevenness.
[0014]
FIG. 4 simply shows the spray behavior in the stratified low load operation condition. The wall surface of the inner cavity 17 includes a first inner wall surface 17a, a second inner wall surface 17b continuous to the outer peripheral side of the first inner wall surface 17a, and a third inner wall surface 17c continuous to the second inner wall surface 17b. Can be divided. The first inner wall surface 17a is an inclined surface that becomes higher toward the central piston reciprocating axis 14, and has a conical shape that is convex upward as a whole. The second inner wall surface 17b forms an inner curved surface that curves smoothly toward the third inner wall surface 17c. The third inner wall surface 17c constitutes the outer wall surface of the entire inner cavity 17, and has a reentrant shape that inclines in a direction closer to the piston reciprocating axis 14 toward the upper side of the piston (upward in FIG. 4).
[0015]
As shown in FIG. 4A, the fuel spray F4 under the stratified low load operation condition is set so as to collide obliquely with the first inner wall surface 17a. The angle θ3 formed by the (center) injection direction F5 of the spray F4 and the spray traveling direction side of the first inner wall surface 17a (radially outside the portion where the spray collides) is an obtuse angle (90 ° to 180 °). °) is set. Accordingly, the fuel spray F4 collides with the first inner wall surface 17a at a gentle angle, and the fuel spray F4 after the collision does not inadvertently scatter, so as to follow the first inner wall surface 17a. Good guidance to the second inner wall surface 17b side. Further, the spray is favorably guided along the third inner wall surface 17c by the smoothly curved second inner wall surface 17b.
[0016]
The third inner wall surface 17c is an inclined surface that is inclined at an angle close to the injection direction F5. Specifically, the angle θ4 formed by the extension line 17c ′ of the third inner wall surface 17c and the parallel line F5 ′ of the injection direction F5 is sufficiently small. However, the reentrant angle e of the third inner wall surface 17c with respect to the piston reciprocating axis 14 is smaller than the angle of the injection direction F5 with respect to the piston reciprocating axis 14. By such third inner wall surface 17c, the fuel spray is satisfactorily guided to go in the original injected direction. As a result, as shown in FIGS. 4B and 4C, a swirl flow F6 swirling like a vortex in the vertical direction along the piston reciprocating axis 14 is generated. The surrounding air is entrained by the swirling flow F6, and the air-fuel mixture generated above the cavity 17 becomes a homogeneous air-fuel mixture K2 having no concentration unevenness. The air-fuel mixture mass K2 is sufficiently smaller than the air-fuel mixture mass K1 formed by the outer cavity 16 shown in FIG.
[0017]
Since the injection timing is set to the retard side compared to the high load operation region, even if the injection directions F2 and F4 are the same in the low load operation region and the high load operation region, as described above, the high load region In this case, the spray collides with the first outer wall surface 16a, and the spray collides with the first inner wall surface 17a in the low load range, so that the outer cavity 16 and the inner cavity 17 can be selectively used according to the load.
[0018]
For example, when using an injection valve capable of changing the injection direction as disclosed in Japanese Patent Application Laid-Open No. 2000-303936, the fuel injection direction is preferably directed to the outer cavity 16 close to the cylinder 3a in the stratified high load region. In the low load region, the injection direction is variably controlled so as to be directed to the inner cavity 17 close to the center. Specifically, the angle of the injection direction with respect to the piston reciprocating axis 14 is relatively large in the stratified high load region and relatively small in the stratified low load region.
[0019]
With reference to FIG. 5, the specific shape of the piston and the operational effects associated therewith will be described in further detail.
[0020]
The depth b of the inner cavity 17 with respect to the piston crown surface 15 is larger than the depth a of the outer cavity 16 with respect to the piston crown surface 15. Thereby, the crown wall flow can be effectively suppressed / prevented in the low load operation region where the injection timing is set to the retard side.
[0021]
The depth c of the inner cavity 17 itself is smaller than the depth a (of the shallowest part) of the outer cavity 16 itself. As a result, in the high load operation region, the spray is satisfactorily introduced into the outer cavity 16 without being blocked by the inner cavity 17.
[0022]
Since both the third outer wall surface 16c of the outer cavity 16 and the third inner wall surface 17c of the inner cavity 17 have a reentrant shape that approaches the piston reciprocation axis 14 toward the upper side of the piston, the air-fuel mixture is satisfactorily mixed in the cavities 16 and 17. Can be contained. In particular, the reentrant angle e of the inner cavity 17 is set larger than the reentrant angle d of the outer cavity 16. Thereby, fuel spillage from the inner cavity 17 can be positively prevented, and stable stratified combustion can be realized even in an extremely low load operation region such as an idle.
[0023]
The angle g formed between the first inner wall surface 17 a of the inner cavity 17 and the orthogonal surface of the piston reciprocating axis 14 is smaller than the angle f formed between the third outer wall surface 16 c of the outer cavity 16 and the orthogonal surface of the piston reciprocating axis 14. Thereby, the crown wall flow can be effectively suppressed / prevented particularly in a high-load stratified operation region where the crown wall flow tends to increase. Incidentally, as shown in the real施例described later, the inclination angle g of the inner cavity 17 to zero, may be a flat surface perpendicular to the first inner wall surface 17a of the piston reciprocation axis 14.
[0024]
The curvature radius Ri of the second inner wall surface 17b, that is, the inner curved surface is smaller than the curvature radius Rh of the outer curved surface of the second outer wall surface 16b. Thereby, the stratified mixture block K2 produced | generated in the inner side cavity 17 becomes a compact thing, and the stratified combustion in a low load operation area | region is stabilized.
[0025]
Figure 6 shows schematically a piston crown surface shape of the actual施例. Note that components substantially the same as those of the reference example are denoted by the same reference numerals, and redundant description is omitted. In this real施例, mixed air mass produced by the inner cavity 17 is smaller than the reference example. That is, the piston shape is set so as to enhance the stability in the extremely low load operation region such as the idle in the low load stratification operation region. Specifically, the first inner wall surface 17 a ′ of the inner cavity 17 is a flat surface orthogonal to the piston reciprocating axis 14. The depth b ′ of the inner cavity relative to the piston crown 15 is smaller than the depth a ′ of the outer cavity 16 relative to the piston crown 15. The reentrant angle of the third inner wall surface 17c with respect to the piston reciprocating axis 14 is set to be smaller or equivalent to the reentrant angle of the third outer wall surface 16c with respect to the piston reciprocating axis 14. Thereby, it is possible to prevent the air-fuel mixture in the inner cavity 17 from becoming excessively concentrated from low load to medium load, and to effectively suppress and prevent the generation of smoke and unburned HC.
[0026]
The technical ideas of the present invention that can be grasped from the above reference examples and examples will be listed together with their effects.
[0027]
(1) In a center injection type in-cylinder direct injection internal combustion engine in which a fuel injection valve and a spark plug are arranged on or in the vicinity of a piston reciprocating axis, an outer cavity having a substantially rotating shaft shape with respect to the piston reciprocating axis Is recessed in the piston crown surface, and an inner cavity is formed in the outer cavity, which is also substantially in the shape of an axially rotating body with respect to the piston reciprocating axis. By adopting such a double cavity structure, for example, stratified combustion is realized using the inner cavity in the low load region, and stratified combustion is realized using the outer cavity in the high load region. In a wide load range including the region, it is possible to realize stratified combustion with stable fuel efficiency and low unburned HC.
[0028]
(2) A first outer wall surface in which fuel spray collides obliquely with the wall surface of the outer cavity, a second outer wall surface continuing to the outer peripheral side of the first outer wall surface, and a third outer surface continuing to the second outer wall surface. A wall surface, and a part or all of the second outer wall surface is an outer curved surface that smoothly curves toward the third outer wall surface, and the third outer wall surface is close to the injection direction of the fuel spray. The inclined surface is inclined at an angle. Thereby, for example, fuel injected in the stratified high load region and colliding with the first outer wall surface is guided to the outer curved surface and the third outer wall surface of the second outer wall surface, and swivels in the vertical direction in the outer cavity and the sky above it. -A circulating swirling flow is generated. Thereby, since the fuel is easily mixed with air and it is difficult to produce uneven concentration, a homogeneous air-fuel mixture field (lump) can be formed in the outer cavity. Accordingly, smoke emission can be suppressed and prevented, and stable combustion can be obtained even when a large amount of EGR is introduced, so that good stratified combustion with little NOx emission can be realized. In addition, since the stratified mixture is formed by the outer cavity having a larger volume than the inner cavity, stable combustion can be realized in a high load operation region where the load is relatively large.
[0029]
(3) The first inner wall surface where the fuel spray strikes obliquely on the wall surface of the inner cavity, the second inner wall surface continuing to the outer peripheral side of the first inner wall surface, and the third inner wall continuing to the second inner wall surface And a part or all of the second inner wall surface is an inner curved surface that smoothly curves toward the third inner wall surface, and the third inner wall surface is close to the injection direction of the fuel spray. The inclined surface is inclined at an angle. Thereby, for example, fuel injected in the stratified low load region and colliding with the first inner wall surface is guided to the inner curved surface and the third inner wall surface of the second inner wall surface, and swivels in the longitudinal direction in the inner cavity and the sky above it. -A circulating swirling flow is generated. As a result, the fuel is easy to mix with the air, and the concentration unevenness is difficult to occur, so that a homogeneous air-fuel mixture field (lump) can be formed in the inner cavity. Accordingly, smoke emission can be suppressed and prevented, and stable combustion can be obtained even when a large amount of EGR is introduced, so that good stratified combustion with little NOx emission can be realized. In addition, since the stratified mixture is formed by the inner cavity having a smaller volume than the outer cavity, stable combustion can be realized in a relatively low load operation region.
[0030]
(4) The curvature radius of the inner curved surface is made smaller than the curvature radius of the outer curved surface. Thereby, it becomes easy to form a small air-fuel mixture under low load stratification conditions using the inner cavity, and stable stratified combustion can be realized.
[0031]
(5) The third outer wall surface has a reentrant shape that approaches the piston reciprocation axis as it goes upward. As a result, the fuel injected into the outer cavity can be well contained, and good stratified combustion with less unburned HC and good fuel efficiency can be realized.
[0032]
(6) The third inner wall surface has a reentrant shape that approaches the piston reciprocation axis as it goes upward. Thereby, the fuel injected into the inner cavity can be contained well, and stratified combustion with less unburned HC and good fuel efficiency can be realized.
[0033]
(7) The inclination of the third inner wall surface with respect to the piston reciprocation axis is made larger than the inclination of the third outer wall surface with respect to the piston reciprocation axis. Thereby, it is possible to more reliably prevent the fuel spray from spilling from the inside cavity, and to realize stable stratified combustion at an extremely low load such as idle.
[0034]
(8) The inclination of the third inner wall surface with respect to the piston reciprocating axis is made smaller than the inclination of the third outer wall surface with respect to the piston reciprocating axis. Thereby, it is possible to prevent the air-fuel mixture in the inner cavity from becoming excessively rich, and to suppress and prevent the generation of smoke and unburned HC.
[0035]
(9) The depth of the inner cavity with respect to the piston crown surface is made smaller than the depth of the outer cavity with respect to the piston crown surface. As a result, the stratified air-fuel mixture formed in the inner cavity becomes compact, and stable stratified combustion can be realized in an extremely low load region such as an idle.
[0036]
(10) The depth of the inner cavity with respect to the piston crown surface is made larger than the depth of the outer cavity with respect to the piston crown surface. In this case, the stratified air-fuel mixture formed in the inner cavity becomes relatively large, and stable stratified combustion can be realized from the low load region to the medium load region.
[0037]
(11) The depth of the inner cavity itself is made smaller than the depth of the outer cavity itself. As a result, the air-fuel mixture formed in the inner cavity is relatively small, the air-fuel mixture formed in the outer cavity is relatively large, and a low load region that uses the inner cavity and a high load that uses the outer cavity. Stable stratified combustion can be realized in both load ranges.
[0038]
(12) The first outer wall surface is an inclined surface that becomes higher toward the piston reciprocating axis. As a result, the momentum of the fuel spray that collides with the first outer wall surface can be reduced to prevent wall flow, and the generation of smoke and the increase in unburned HC can be reduced / prevented.
[0039]
(13) The first inner wall surface is an inclined surface that becomes higher toward the piston reciprocating axis. As a result, the momentum of the fuel spray that collides with the first inner wall surface can be reduced to prevent wall flow, and the generation of smoke and the increase in unburned HC can be reduced or prevented.
[0040]
(14) The inclination of the first inner wall surface with respect to the orthogonal plane of the piston reciprocating axis is made smaller than the inclination of the first outer wall surface with respect to the orthogonal plane. As a result, wall flow in the outer cavity is reliably reduced / prevented, and in the stratified high-load operation region where the injection amount is large and smoke and unburned HC tend to increase, smoke is generated and unburned HC using the outer cavity. Can be effectively reduced / prevented.
[0041]
(15) By making the first inner wall surface a flat surface substantially orthogonal to the piston reciprocating axis, combustion stability in an extremely low load stratified operation region such as an idle with little smoke or unburned HC emission is secured. However, it is possible to improve workability and reduce cooling loss.
[0042]
(16) When the fuel injection valve is a multi-hole injection valve, even when the in-cylinder pressure in the latter half of the compression stroke increases, the directivity of the spray is strong and a spray swirl flow is easily generated. It is easy to produce a stratified mixture.
[0043]
(17) When performing stratified combustion in which fuel is injected in the latter half of the compression stroke, the injection timing in the high load operation condition is advanced from the injection timing in the low load operation condition. As a result, an air-fuel mixture having an appropriate size can be formed under both low and high load operating conditions, and stable stratified combustion can be realized at both low and high loads.
[0044]
(18) When the fuel injection valve can change the injection direction, the angle of the injection direction with respect to the piston reciprocating axis is relatively large so as to be directed to the inner cavity when the load is low, and the outer cavity when the load is high Make it relatively small so that it is oriented.
[0045]
(19) As described above, the injection direction of the fuel injection valve is directed to the outer cavity in the high load operation condition, and is directed to the inner cavity in the low load operation condition. A small air-fuel mixture is formed, and a relatively large air-fuel mixture can be formed by the outer cavity under high load operation conditions, and stable stratified combustion can be realized in both the low load region and the high load region.
[Brief description of the drawings]
FIG. 1 is a configuration diagram schematically showing a direct injection type internal combustion engine according to the present invention.
FIG. 2 is a top view corresponding to a piston crown surface as viewed from above.
FIG. 3 is an explanatory view showing a piston shape and a spray behavior under a stratified high load condition according to a reference example.
FIG. 4 is an explanatory diagram showing a piston shape and spray behavior under a stratified low load condition according to a reference example.
FIG. 5 is a cross-sectional view showing the shape and various dimensions of a piston according to a reference example.
FIG. 6 is a cross-sectional corresponding view showing the shape and various dimensions of the piston according to the actual施例.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Combustion chamber 4 ... Piston 11 ... Fuel injection valve 12 ... Spark plug 15 ... Piston crown surface 16 ... Outer cavity 16a ... First outer wall surface 16b ... Second outer wall surface 16c ... Third outer wall surface 17 ... Inner cavity 17a ... First 1 inner wall surface 17b ... second inner wall surface 17c ... third inner wall surface

Claims (17)

A fuel injection valve disposed on or near the piston reciprocating axis and directly injecting fuel into the combustion chamber;
An ignition plug that is disposed on or in the vicinity of the piston reciprocating axis and sparks the air-fuel mixture in the combustion chamber;
An outer cavity that is recessed in the piston crown and has a substantially axially rotating shape with respect to the piston reciprocating axis;
An inner cavity that is recessed in the outer cavity and forms a substantially axially rotating body with respect to the piston reciprocating axis.
The fuel spray injected from the fuel injection valve, Ri substantially conical shape der around the piston reciprocation axis,
A direct injection type internal combustion engine , wherein a depth of the inner cavity with respect to the piston crown surface is equal to or less than a depth of the outer cavity with respect to the piston crown surface . The outer cavity includes a first outer wall surface on which fuel spray strikes obliquely, a second outer wall surface continuous with the outer peripheral side of the first outer wall surface, and a third outer wall surface continuous with the second outer wall surface. Have
The second outer wall surface includes an outer curved surface that smoothly curves toward the third outer wall surface,
The in-cylinder direct injection internal combustion engine according to claim 1, wherein the third outer wall surface is an inclined surface inclined at an angle close to an injection direction of the fuel spray. The inner cavity includes a first inner wall surface on which fuel spray strikes obliquely, a second inner wall surface continuous with the outer peripheral side of the first inner wall surface, and a third inner wall surface continuous with the second inner wall surface. Have
The second inner wall surface includes an inner curved surface that smoothly curves toward the third inner wall surface,
The in-cylinder direct injection internal combustion engine according to claim 2, wherein the third inner wall surface is an inclined surface inclined at an angle close to an injection direction of the fuel spray.   The direct injection type internal combustion engine according to claim 3, wherein a radius of curvature of the inner curved surface is smaller than a radius of curvature of the outer curved surface.   The in-cylinder direct injection internal combustion engine according to any one of claims 2 to 4, wherein the third outer wall surface has a reentrant shape that approaches a piston reciprocation axis as it goes upward of the piston.   The in-cylinder direct injection internal combustion engine according to claim 3 or 4, wherein the third inner wall surface has a reentrant shape that approaches a piston reciprocation axis as it goes upward of the piston.   7. The direct injection type internal combustion engine according to claim 3, wherein an inclination of the third inner wall surface with respect to the piston reciprocating axis is larger than an inclination of the third outer wall surface with respect to the piston reciprocating axis.   The direct injection type internal combustion engine according to any one of claims 3, 4 and 6, wherein the inclination of the third inner wall surface with respect to the piston reciprocating axis is smaller than the inclination of the third outer wall surface with respect to the piston reciprocating axis. The in-cylinder direct injection internal combustion engine according to any one of claims 1 to 8 , wherein a depth of the inner cavity itself is smaller than a depth of the outer cavity itself.   The direct injection type internal combustion engine according to any one of claims 2 to 8, wherein the first outer wall surface is an inclined surface that becomes higher toward the piston reciprocating axis.   The in-cylinder direct injection internal combustion engine according to any one of claims 3, 4, 6 to 8, wherein the first inner wall surface is an inclined surface that becomes higher toward the piston reciprocating axis. The direct injection internal combustion engine according to claim 11 , wherein an inclination of the first inner wall surface with respect to an orthogonal plane of the piston reciprocating axis is smaller than an inclination of the first outer wall surface with respect to the orthogonal plane.   The in-cylinder direct injection internal combustion engine according to any one of claims 3, 4, 6 to 8, wherein the first inner wall surface is a flat surface substantially orthogonal to the piston reciprocating axis. Cylinder direct injection internal combustion engine according to any of claims 1 to 1 3 the fuel injection valve is a multi-hole injector. In the case of performing the stratified charge combustion in which the fuel is injected in the compression stroke late with changing the injection timing by the load, it claims to advance the injection timing in the high load operating conditions than the injection timing in the low load operating condition 1-14 The direct injection type internal combustion engine according to any one of the above. The fuel injection valve is an injection valve capable of changing the injection direction,
The in-cylinder direct injection internal combustion engine according to any one of claims 1 to 15 , wherein an angle in an injection direction with respect to a piston reciprocating axis is larger in a low load condition than in a high load condition. The direct injection internal combustion engine according to claim 15 or 16 , wherein an injection direction of the fuel injection valve is directed to an outer cavity in a high load operation condition and directed to an inner cavity in a low load operation condition.

Images