JP4155184B2 - In-cylinder internal combustion engine - Google Patents

Description

  The present invention relates to a direct injection internal combustion engine, and more particularly, to a direct injection internal combustion engine in which a cavity is provided in a crown surface of a piston and a fuel supply injector is installed above a central portion of the cavity.

  There is known an internal combustion engine in which an injector for supplying fuel is installed facing a combustion chamber and fuel is injected during the compression stroke by the injector during combustion in a predetermined operation region to form a mixture in a layered manner. . According to this direct injection internal combustion engine, the fuel consumption in these operating regions can be significantly reduced by stratifying the air-fuel mixture in the low load region and the medium load region. In stratified combustion performed by stratifying the air-fuel mixture, it is necessary to concentrate the fuel spray around the spark plug to form an air-fuel mixture mass in order to ensure ignitability.

Conventionally, the following are known as cylinder injection type internal combustion engines. That is, a cavity is formed on the crown surface of the piston, and an injector is installed in the cylinder head above the central portion of the cavity so as to face the crown surface of the piston. According to this, the spray of fuel injected by the injector (hereinafter simply referred to as “spray”) is guided along the wall surface of the cavity to form a circulation flow of the spray toward the spark plug. Thus, the spray can be concentrated around the spark plug while suppressing diffusion (Patent Document 1).
JP-A-11-082028 (paragraph numbers 0010 to 0012)

  However, the above-described cylinder injection internal combustion engine has the following problems. That is, in stratified combustion, it is desired to form an air-fuel mixture having an appropriate size with respect to the amount of fuel supplied, and to make the air-fuel ratio of the air-fuel mixture as a whole moderate. When the air-fuel mass is too small relative to the fuel supply amount, the air-fuel mass becomes excessively concentrated as a whole, and hydrocarbons (hereinafter referred to as “HC”) and carbon monoxide (hereinafter referred to as “CO”). If the air-fuel mixture volume is too large relative to the amount of fuel supplied, the air-fuel mixture volume becomes dilute as a whole, which causes generation of nitrogen oxides (hereinafter referred to as “NOx”) due to an increase in combustion temperature. This is because the ignitability is lowered, which causes an increase in HC and CO due to misfire. Here, the size of the air-fuel mixture formed is substantially determined by the shape and volume of the cavity for guiding the spray. When the shape of the cavity is set to suit the low load, a small air-fuel mixture is formed. Since air mass is formed, the air-fuel mixture tends to become lean at low load.

  An object of the present invention is to avoid the formation of a rich mixture at the time of a high load, ensure the ignitability at the time of a low load, and to enable stable stratified combustion with less emission in a wide operation range. And

A cylinder injection type internal combustion engine according to the present invention includes:
A piston having a cavity in the center of the crown surface;
A multi-hole injector located above the central portion of the cavity and having the injection direction as a whole parallel to the direction of movement of the piston, and spray from each injection hole toward a predetermined position in the circumferential direction;
A spark plug for igniting the fuel injected by the injector;
A controller for controlling the operation of the injector;
Comprising
The cavity of the piston is entirely surrounded by a first wall portion, and a part of the bottom surface of the cavity in the circumferential direction is a piston plane so as to face spray from a part of the nozzle holes. A second wall portion having a fan-like shape is locally raised from the bottom surface, and the wall surface on the inner peripheral side of the second wall portion is closer to the center portion of the cavity than the first wall portion. Located in
The controller sets the first injection timing during the compression stroke that is relatively slow with respect to the crank angle so that the spray from some of the injection holes is directed to the inner portion of the second wall as the injection timing of the injector. And a second injection timing during a compression stroke earlier than the first injection timing so that the spray is directed to a portion outside the second wall portion in the cavity, and these injections are set. The timing is switched according to the operating state of the engine.

  According to the present invention, by adjusting the shape of the cavity and the like at the time of high load so that a relatively large air-fuel mixture mass is formed, in the operation by stratified combustion, at the time of high load, formation of the rich mixture Thus, the air-fuel ratio of the air-fuel mixture can be made moderate as a whole. On the other hand, when the load is low, the air-fuel mixture itself becomes large, but a part of the spray can be guided by the second wall portion and can be directed in a different direction from the case of the cavity itself. By disposing the spark plug, the spray can be distributed around the spark plug and the ignitability can be ensured.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows the configuration of a direct injection internal combustion engine (hereinafter referred to as “engine”) 1 according to an embodiment of the present invention.
A piston 12 is inserted into the cylinder block 11, and a space formed between the crown surface of the piston 12 and the lower surface of the cylinder head 13 becomes a combustion chamber 14. An intake port 15 is formed on one side of the cylinder head 13 with respect to the cylinder center axis m. The intake port 15 is connected to an intake manifold (not shown) to form an intake passage. The intake port 15 is opened and closed by an intake valve 16. On the other hand, an exhaust port 17 is formed on the other side with respect to the cylinder center axis m, and the exhaust port 17 is connected to an exhaust manifold (not shown) to form an exhaust passage. The exhaust port 17 is opened and closed by an exhaust valve 18. The intake valve 16 and the exhaust valve 18 are driven by an intake cam 19 and an exhaust cam 20, respectively.

The cylinder head 13 is provided with an injector 21 for supplying fuel so as to face the substantially upper center of the combustion chamber 14, and an ignition plug 22 is provided adjacent to the injector 21.
In the present embodiment, the injector 21 is installed on the cylinder center axis m. The injector 21 is a multi-hole type injector in which a plurality of injection holes are provided in the circumferential direction in the nozzle portion at the tip, and the fuel injected from each injection hole forms a hollow cone-like spray as a whole. The center line of this cone corresponds to the injection direction line of the injector 21, and this injection direction line is set parallel to the cylinder center axis m (in this embodiment, the injection direction line and the cylinder center axis m are equal to each other). I do it.) Note that the term “parallel” as used herein is a concept that includes not only perfect parallelism but also substantial parallelism. That is, the injection direction line is in a state parallel to or close to the cylinder center axis m, and an action described later is obtained in which the spray is guided by the cavity 121 to form a circulation flow of the spray toward the spark plug 22. If it is in a state. The fuel pressurized by the fuel pump 23 is supplied to the injector 21 through the fuel pipe 24 at a specified pressure. The fuel pump 23 is driven by the output of the engine 1.

  A cavity 121 for guiding the spray is formed on the crown surface of the piston 12. The cavity 121 has a cross section with a plane perpendicular to the cylinder central axis m and is formed in a circular shape, and the center thereof coincides with the cylinder central axis m. The bottom surface 121a of the cavity is formed flat in a plane perpendicular to the cylinder center axis m, and the peripheral wall surface 121b is formed substantially parallel to the cylinder center axis m, and is smooth with an appropriate curved surface with respect to the bottom surface 121a. It is connected.

  In addition, a guide wall 123 is formed on the crown surface of the piston 12 so as to have a height h with respect to the bottom surface 121 a of the cavity in the cavity 121. The guide wall 123 guides part of the spray along a route different from that of the cavity 121. Here, in the piston 12, the wall portion (hereinafter referred to as the “crown surface outer peripheral portion”) 125 whose inner surface is the peripheral wall surface 121 b of the cavity is the “first wall portion”, and the guide wall 123 is the “second wall”. Part.

FIG. 2A shows a state in which the piston 12 is viewed from above along the cylinder center axis m. FIGS. 2B and 2C are cross-sectional views of the piston 12 taken along line AA and BB. A line section is shown.
In the present embodiment, a guide wall 123 is provided in the cavity 121 on the crown surface of the piston 12, and a part of the spray can be guided by the guide wall 123, and the other spray can be guided by the cavity 121.

The guide wall 123 is formed in a generally fan shape around the cylinder central axis m in the cavity 121, and a predetermined one (here, a2) of the central axes a1 to a4 of each injection hole of the injector 21 is formed. It is provided symmetrically as a reference. The guide wall 123 has side surfaces (forms “end edges” of the second wall portion) 123b, 123b formed in a plane perpendicular to the circumferential direction centering on the cylinder central axis m. The side surfaces 123b and 123b terminate in the circumferential direction. The side surfaces 123b and 123b are connected at right angles to the bottom surface 121a of the cavity. On the other hand, the inner peripheral wall surface, that is, the inner surface 123a of the guide wall is formed in an arc shape in a cross section by a plane perpendicular to the cylinder center axis m, and the distance from the cylinder center axis m is lower than the bottom surface 121a. It is formed to be inclined at an angle of less than 90 ° so as to be longer as the position is closer to. The inner surface 123a may be formed in parallel with the cylinder center axis m. Further, the inner surface 123a is smoothly connected to the bottom surface 121a of the cavity by an appropriate curved surface. The spark plug 22 is installed on the central axis a2 of the nozzle hole at a position closer to the cylinder central axis m than the guide wall 123. The specific shape of the inner surface 123a is the installation point of the injector 21 (cylinder central axis). m), and a part of an ellipse having a focal point at the installation point P of the spark plug 22 may be formed. The height h of the guide wall 123 is constant in the circumferential direction and is set to a value smaller than the depth d of the cavity 121. The upper surface 123c of the guide wall is formed to be inclined with respect to the bottom surface 121a of the cavity so that the height h of the guide wall 123 decreases as the distance from the cylinder center axis m (that is, the central portion of the cavity) increases. The outer edge in the radial direction of the guide wall 123 is smoothly connected to the peripheral wall surface 121b of the cavity by an appropriate curved surface.

  Returning to FIG. 1, the operation of the engine 1 is integrally controlled by a control unit (hereinafter referred to as “ECU”) 31. The engine 1 detects a signal from the air flow meter 41 that detects the intake air amount QM, a signal from the crank angle sensor 42 (based on this, the engine speed NE is calculated), and the coolant temperature Tw. A signal from the temperature sensor 43 is input. Based on these signals, the ECU 31 calculates and sets the fuel injection amount and injection timing of the injector 21 and the ignition timing of the spark plug 22.

  In the present embodiment, the combustion mode is switched between diffusion combustion and stratified combustion in accordance with the operating state of the engine 1. In diffusion combustion, the air-fuel ratio is set to the stoichiometric air-fuel ratio, the fuel injection timing is set to the intake stroke, and the spray is diffused throughout the combustion chamber 14 to form an air-fuel mixture. In stratified combustion, the air-fuel ratio is set to a value larger than the stoichiometric air-fuel ratio, the fuel injection timing is set during the compression stroke, the spray is concentrated in the region near the spark plug 22, and the air-fuel mixture is formed in layers.

  In addition, the ratio (hereinafter referred to as “injection amount ratio”) of the fuel injected from the injector 21 toward each position in the circumferential direction with reference to the spray center line (that is, the cylinder center axis m) (hereinafter “injection amount ratio”) R) may be uniform in the circumferential direction, but in the present embodiment, it is made different in the circumferential direction so that the fuel injected toward the guide wall 123 is larger than the other fuels. Yes. In the multi-hole type injector 21, the injection amount ratio can be easily adjusted by making the diameters of some of the nozzle holes (here, the center axis a <b> 2) different from the diameters of the other nozzle holes. It is possible, and the fuel injected toward the guide wall 123 can be increased by setting the diameter of the former nozzle hole to a value larger than the diameter of the latter nozzle hole. The spray injected toward the guide wall 123 is received by the guide wall 123 and guided upward, and travels toward the spark plug 22.

Next, the operation of the ECU 31 will be described with reference to a flowchart.
FIG. 3 is a flowchart of a fuel injection control routine. This routine is started when the ignition switch is turned on, and then executed every predetermined time. In this routine, the combustion mode corresponding to the operating state is selected, and the fuel injection amount Qf and the fuel injection timing IT are set based on the selected combustion mode.

In S101, various operation states such as the intake air amount QM, the engine speed NE, and the cooling water temperature Tw are read.
In S102, the region to which the operating state of the engine 1 belongs is determined. This determination is made by searching the map shown in FIG. 4 according to the rotational speed (for example, engine speed NE) and the load (for example, intake air amount per rotation = QM / NE), and the operating state of the engine 1 depends on the load. This is done by determining which one of the areas A to C belongs to. If the load belongs to the area A, the process proceeds to S103, and if the load belongs to the area C, the process proceeds to S105. When belonging to the region B between these regions A and C, the process proceeds to S104.

In S103, the injection stratified combustion mode is selected once, and the fuel injection amount Qf and the fuel injection timing IT are set according to the flowchart shown in FIG.
In S104, the double injection stratified combustion mode is selected, and the fuel injection amount Qf and the like are set according to the flowchart shown in FIG.
In S105, the diffusion combustion mode is selected, and the fuel injection amount Qf and the like are set according to the flowchart shown in FIG.

In the flowchart shown in FIG. 5, in S201, the fuel injection amount Qf is calculated. In the once-injection stratified combustion mode, the air-fuel ratio is set to a value larger than the stoichiometric air-fuel ratio, and the fuel injection amount Qf is calculated by the following equation. Note that k is a coefficient that gives a fuel injection amount corresponding to the theoretical air-fuel ratio, LAMB is an equivalence ratio, and COEF is an increase correction coefficient corresponding to the coolant temperature Tw and the like.
Qf = k × (QM / NE) × LAMB × COEF (2)
In S202, fuel injection timing (corresponding to “first injection timing”) IT is set. The fuel injection timing IT is set to be retarded at a relatively late time during the compression stroke as the load is low (FIG. 6). In the set IT, the fuel is injected inward of the inner surface 123a of the guide wall in the cavity 121.

In the flowchart shown in FIG. 7, in S301, the fuel injection amount Qf is calculated. In the double injection stratified combustion mode, the air-fuel ratio is set to a value larger than the stoichiometric air-fuel ratio, and an amount of fuel corresponding to the load is injected in two portions. The fuel injection amount Qf is calculated by equation (2), and the calculated Qf indicates the total amount of fuel injected per cycle.
In S302, the amount of fuel injected in the previous fuel injection (hereinafter referred to as “first injection amount”) Q1 is set. The first injection amount Q1 is calculated by multiplying the fuel injection amount Qf by a predetermined ratio RTO.

Q1 = Qf × RTO (3)
In S303, the timing for starting the previous fuel injection (hereinafter referred to as “first injection timing”, which corresponds to “second injection timing”) IT1 is set. The first injection timing IT1 is set at a relatively early time during the compression stroke, with the angle being retarded as the load is low (FIG. 8). In the set IT1, the fuel is injected toward the outside of the inner surface 123a of the guide wall in the cavity 121.

In S304, the amount of fuel to be injected in the subsequent fuel injection (hereinafter referred to as “second injection amount”) Q2 is set. The second injection amount Q2 is calculated by subtracting the first injection amount Q1 from the fuel injection amount Qf.
Q2 = Qf−Q1 (4)
In S305, the timing for starting the subsequent fuel injection (hereinafter referred to as "second injection timing" and corresponding to "third injection timing") IT2 is set. The second injection timing IT2 is set at a timing later than the first injection timing IT1 during the compression stroke, and is retarded as the load is low (FIG. 9). In the set IT2, the fuel is injected inward of the inner surface 123a of the guide wall in the cavity 121.

In the flowchart shown in FIG. 10, in S401, the fuel injection amount Qf is calculated by the equation (2). In the diffusion combustion mode, the air-fuel ratio is set to the stoichiometric air-fuel ratio.
In S402, the fuel injection timing IT is set. The fuel injection timing IT is set during the intake stroke.
Next, the concept of air-fuel mixture formation by the above fuel injection control will be described.

FIG. 11 shows a case in which the load is relatively low in the case of the single injection stratified combustion mode (region A), where (a) shows the state at the fuel injection timing IT, and (b) shows ignition. It shows the state at the time.
The fuel injection timing IT here is set to a timing at which fuel is injected toward the inside of the guide wall 123, but is set to a particularly late timing in the region A. The spray S collides with the bottom surface 121a of the cavity and spreads outward along the bottom surface 121a. Here, a part of the spray S is guided upward along the inner surface 123 a by the guide wall 123 to form a vertical circulation flow toward the spark plug 22. By setting the fuel injection timing IT to a late timing, the spray S other than the one injected toward the guide wall 123 is held in the cavity 121, and the ignition timing is reached before the diffusion proceeds. At the ignition timing, the spray S is held in the cavity 121 and a relatively small air-fuel mixture M is formed in which the spray S is distributed around the spark plug 22 at an appropriate air-fuel ratio.

FIG. 12 shows a case where the load is relatively high in the case of the single injection stratified combustion mode (region A), where (a) shows the state at the fuel injection timing IT, and (b) shows ignition. It shows the state at the time.
The fuel injection timing IT here is set to a timing at which fuel is injected toward the inside of the guide wall 123, but is set to an earlier timing than that at the time of the low load. The spray S collides with the bottom surface 121a of the cavity and spreads outward. Particularly, the spray S directed toward the guide wall 123 forms a circulation flow and is directed to the spark plug 22 as described above. Here, since the fuel injection timing IT is set to a relatively early time, a certain amount of time is secured until the ignition timing is reached, and the spray S other than the one injected toward the guide wall 123 is also present. , Guided upward along the peripheral wall surface 121b of the cavity. For this reason, at the ignition timing, a larger air-fuel mixture M is formed in the cavity 121 (excluding the region where the flow is hindered by the guide wall 123) and above the spray S is concentrated, compared to when the load is low. The Note that the air-fuel mass M formed here is also smaller in size than the air-fuel mass M formed in the next higher load region, and overspreading of the spray S is prevented.

FIG. 13 shows the case of the double injection stratified combustion mode (region B), where (a) shows the state at the first injection timing IT1, and (b) shows the state immediately before the second injection timing IT2. (C) shows the state at the second injection timing IT2, and (d) shows the state at the ignition timing. (A)-(d) has shown the state in a cylinder in time series order.
The first injection time IT1 is set at a relatively early time during the compression stroke, and the fuel is injected toward the outside of the guide wall 123 at the set IT1. The spray S1 collides with the bottom surface 121a of the cavity and the top surface 123c of the guide wall, spreads outward along these surfaces 121a and 123c, and is guided upward along the peripheral wall surface 121b of the cavity, thereby circulating the circulating flow. Form. On the other hand, the second injection timing IT2 is set to a time later than the first injection timing IT1 during the compression stroke, and the fuel is injected toward the inside of the guide wall 123 at the set IT2. The spray S <b> 2 is guided along the bottom surface 121 a of the cavity as in the case of the one-split stratified combustion mode, and a part thereof is guided by the guide wall 123 to form a circulating flow and travels toward the spark plug 22. At the ignition timing, a large air-fuel mixture M in which the spray S is concentrated in the entire cavity 121 and above is formed.

According to this embodiment, the following effects can be obtained.
First, in the present embodiment, a guide wall 123 for actively guiding a part of the spray S toward the spark plug 22 is provided in the cavity 121. In the stratified combustion region, the guide wall 123 is provided when the load is low. The fuel is injected toward the outside of the guide wall 123 at the time of high load. Since the air-fuel mixture M formed by the cavities 121 itself becomes large, it is possible to avoid the formation of an excessively rich air-fuel mixture at a high load. On the other hand, since the air-fuel mixture mass M becomes large, the air-fuel mixture mass M tends to be thin as a whole at low load, but a part of the spray S is guided toward the spark plug 22 by the guide wall 123. Therefore, the spray S can be distributed around the spark plug 22 at an appropriate air-fuel ratio, and ignitability can be ensured.

Secondly, since the side surface 123b is formed on the guide wall 123 and a step is provided on the edge of the guide wall 123, the diffusion of the spray S guided by the guide wall 123 in the circumferential direction can be suppressed. it can. For this reason, the spray S can be actively concentrated around the spark plug 22 particularly at a low load.
Thirdly, since the inner surface 123a of the guide wall is formed in an arc shape, the spray S colliding with the guide wall 123 can be guided well upward (that is, the spark plug 22). By making the shape of the inner surface 123a a part of an ellipse with the respective installation points of the injector 21 and the spark plug 22 as a focal point, this effect becomes better.

Fourth, by increasing the amount of fuel injected from the injector 21 toward the guide wall 123 as compared with the fuel injected in the other direction, the fuel is concentrated around the spark plug 22 and is ignitable. Can be improved.
Fifth, in the region B where the load is relatively high in the stratified combustion region, the amount of fuel corresponding to the load is injected in two portions, and the previous fuel injection is directed to the outside of the guide wall 123. The subsequent fuel injection is directed toward the inside of the guide wall 123. For this reason, the air-fuel mixture M itself is large, so that the formation of a rich air-fuel mixture can be avoided, and the air-fuel mixture around the spark plug 22 can be prevented from becoming lean, and the ignitability can be ensured.

Next, another embodiment of the present invention will be described.
FIG. 14 shows the configuration of the piston 12 according to the present embodiment, and FIG. 14A shows the state of the piston 12 viewed from above along the cylinder central axis m. ) Shows an AA line cross section and a BB line cross section of the piston 12.
In the present embodiment, the height h of the guide wall 123 gradually decreases as the guide wall 123 moves away from the central axis (here, a2) of the nozzle hole in the circumferential direction, and the edge of the guide wall 123 becomes the bottom surface 121a of the cavity. It is formed in the same plane. For this reason, in this embodiment, the substantial level | step difference is not formed in the edge of the guide wall 123. FIG. Further, in the present embodiment, the function of guiding the spray S is ensured by increasing the inclination of the upper surface 123c of the guide wall as the position is closer to the edge, thereby increasing the area of the central portion of the inner surface 123a. The guide wall 123 is provided symmetrically with respect to the central axis a 2, the inner surface 123 a is formed in an arc shape, and the maximum height H (= h 1) of the guide wall 123 is smaller than the depth d of the cavity 121. The configuration other than the point in which the step is not formed on the edge of the guide wall 123, such as the point set to, is the same as in the previous embodiment.

  According to this embodiment, the upper surface 123c of the guide wall is inclined with respect to the bottom surface 121a of the cavity so that no step is formed on the edge of the guide wall 123 (FIG. 14 (d)). Compared to the case, the diffusion of the spray S colliding with the guide wall 123 in the circumferential direction is allowed. For this reason, it is possible to prevent the spray S from being excessively concentrated around the spark plug 22 by the guide of the guide wall 123 and incomplete combustion especially at high load.

  In the above, the injection amount ratio of the injector 21 is varied in the circumferential direction so that the fuel injected toward the guide wall 123 is larger than the fuel injected toward the other direction. On the contrary, by making the latter fuel more than the former fuel (in other words, by reducing the amount of fuel injected toward the guide wall 123), the fuel around the spark plug 22 becomes excessive. The concentration can be prevented and the ignitability can be improved.

Configuration of engine according to one embodiment of the present invention Configuration of piston according to the embodiment Flow chart of fuel injection control routine Area judgment map Flow chart of control in the once-split stratified combustion mode Fuel injection timing setting table for combustion mode as above Flow chart of control in double-spray stratified combustion mode First injection timing setting table Second injection timing setting table Flow chart of control in diffusion combustion mode The concept of mixture formation in the low load region of the stratified combustion region The concept of mixture formation in the middle load region of the stratified combustion region The concept of air-fuel mixture formation in the high load region of the stratified combustion region Configuration of piston according to another embodiment of the present invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 11 ... Cylinder block, 12 ... Piston, 121 ... Cavity, 121a ... Cavity bottom surface, 121b ... Perimeter wall surface of cavity, 123 ... Guide wall as 2nd wall part, 123a ... Inner surface of guide wall, 123b DESCRIPTION OF SYMBOLS ... Side surface of guide wall, 123c ... Upper surface of guide wall, 125 ... Crown surface outer peripheral part as first wall part, 13 ... Cylinder head, 14 ... Combustion chamber, 15 ... Intake port, 16 ... Intake valve, 17 ... Exhaust Port, 18 ... Exhaust valve, 21 ... Injector, 22 ... Spark plug, 31 ... Control unit, 41 ... Air flow meter, 42 ... Crank angle sensor, 43 ... Coolant temperature sensor, S ... Spray, M ... Air mixture, P ... installation point of spark plug, m ... center axis of cylinder.

Claims (8)

A piston having a cavity in the center of the crown surface;
A multi-hole injector located above the central portion of the cavity and having the injection direction as a whole parallel to the direction of movement of the piston, and spray from each injection hole toward a predetermined position in the circumferential direction ;
A spark plug for igniting the fuel injected by the injector;
A controller for controlling the operation of the injector;
Comprising
The cavity of the piston is entirely surrounded by a first wall portion, and a part of the bottom surface of the cavity in the circumferential direction is a piston plane so as to face spray from a part of the nozzle holes. A second wall portion having a fan-like shape is locally raised from the bottom surface, and the wall surface on the inner peripheral side of the second wall portion is closer to the center portion of the cavity than the first wall portion. Located in
The controller sets the first injection timing during the compression stroke that is relatively slow with respect to the crank angle so that the spray from some of the injection holes is directed to the inner portion of the second wall as the injection timing of the injector. And a second injection timing during a compression stroke earlier than the first injection timing so that the spray is directed to a portion outside the second wall portion in the cavity, and these injections are set. A direct injection internal combustion engine characterized in that the timing is switched according to the operating state of the engine. The in-cylinder injection internal combustion engine according to claim 1, wherein the inner peripheral wall surface of the second wall portion has an arc shape in a cross section taken along a plane perpendicular to the central axis of the piston. 3. The in-cylinder injection type according to claim 2, wherein a wall surface on an inner peripheral side of the second wall portion forms a part of an ellipse having a long axis as a straight line connecting each installation point of the injector and the spark plug in the cross section. Internal combustion engine. The in-cylinder injection internal combustion engine according to any one of claims 1 to 3 , wherein the spark plug is disposed so as to be biased toward one side from the cylinder central axis in correspondence with the circumferential position of the second wall portion .   The in-cylinder injection internal combustion engine according to claim 4, wherein the spark plug is provided at a position closer to the cylinder central axis than the second wall portion. 6. The direct injection internal combustion engine according to claim 5, wherein an angle formed between the bottom surface of the cavity and the wall surface on the inner peripheral side of the second wall portion is 90 ° or less. The fuel contained in the 1st spray injected toward the 2nd wall part from an injector is more than the fuel contained in the 2nd spray injected toward the other position. The in-cylinder injection internal combustion engine according to any one of the above. In the operating state in which the second injection timing is set, in addition to the second injection timing, a third injection timing during the compression stroke later than this is set, and the second and third injection timings per cycle. Each of the fuel is injected,
The in-cylinder injection internal combustion engine according to any one of claims 1 to 7 , wherein fuel is injected toward a portion of the cavity inside the second wall portion at the third injection timing.

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