JP2006183576A - Cylinder injection type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure crown surface achievement distance of spray and suppress formation of over rich air fuel mixture when stratified combustion to make spray move by penetration force of itself. <P>SOLUTION: A drive mechanism D moving an injection point p of the injector 21 in relation to a piston crown surface is constructed. When spray is moved by penetration force of itself and ignition of spray before impingement on the crown surface of the piston is performed in stratified combustion, the injection point p is moved to a position far from the crown surface of the piston. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an in-cylinder injection internal combustion engine, and more particularly, to an in-cylinder injection internal combustion engine in which a cavity is provided in a crown surface of a piston and a fuel supply injector is installed to face the crown surface of the piston. .

  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 a cylinder injection type internal combustion engine, in order to achieve more stable and reliable ignition and combustion during stratified combustion, an air-fuel mixture can be formed in an appropriate size and air-fuel ratio in the combustion chamber according to the operating state of the engine. Required.

2. Description of the Related Art Conventionally, the following techniques are known for a direct injection internal combustion engine. That is, in the cylinder head, an injector is disposed outside the intake port with respect to the cylinder center axis, and the intake control valve is operated to spray the fuel sprayed from the side to the combustion chamber itself. Thus, it reaches the vicinity of the spark plug (Patent Document 1).
Further, as an in-cylinder injection type internal combustion engine, there is known a cylinder in which a cavity for guiding spray is formed on a crown surface of a piston and an injector is installed on the cylinder central axis so as to face the crown surface of the piston. (Patent Document 2).
JP 2004-052732 A (paragraph number 0049) Japanese Patent Application No. 11-082028 (FIG. 1)

  However, the above technique has the following problems. That is, in this technique, the spray is moved by the penetration force itself, and it is necessary to perform ignition during fuel injection or immediately after the end of the injection. Therefore, the fuel injection timing is the retarded side of the compression stroke. It will be set near the top dead center. For this reason, at the set injection timing, it is not possible to secure a sufficient distance between the injection point of the injector and the crown surface of the piston (hereinafter referred to as “spray surface arrival distance”), and the tip of the spray However, it will collide with the crown of the piston with insufficient fuel evaporation and mixing. For this reason, a rich mixture is easily formed in the vicinity of the crown surface of the piston, increasing the smoke and reducing the combustion stability. This problem becomes more prominent in a direct injection internal combustion engine in which the injector is installed on the cylinder central axis.

  In the present invention, in the case of performing stratified combustion in which the spray is moved by its penetrating force itself, the crown reachable distance of the spray is secured, and the formation of a rich mixture that causes generation of smoke and deterioration of combustion stability It aims at suppressing.

  The present invention provides a direct injection internal combustion engine. An apparatus according to the present invention includes a fuel supply injector installed so as to face a crown surface of a piston, and an ignition plug for igniting fuel injected by the injector. The injection point is configured to be movable in the injection direction, and the injection timing is set during the compression stroke in a relatively low load side region of the engine operation region. The injection point of the injector is a piston crown surface (for example, compression top) in the first region where ignition by the spark plug is performed on the spray before the collision with the piston crown surface in the low load side region. While the first position is set relatively far from the crown surface of the piston at the dead center), the second area set as an area other than the first area is more than the first position. A second position close to the crown surface is set.

  According to the present invention, in the first region where the ignition is performed on the spray before the collision with the crown surface of the piston, the injection point of the injector is set to the first position relatively far from the crown surface of the piston. As a result, it is possible to ensure the distance that the spray reaches the crown surface, and to allow the fuel to evaporate and mix before the collision with the crown surface, resulting in the generation of smoke and the deterioration of combustion stability. Qi formation can be suppressed. Further, according to the present invention, the injection point is made different between the first region and the second region set as the region other than the first region, and the injection point is changed in the second region. Is set at the second position closer to the crown of the piston than the first position, so that it is possible to form a good air-fuel mixture in both the first region and the second region, Stable stratified combustion can be performed for each region.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of a cylinder injection internal combustion engine (hereinafter referred to as “engine”) 1A according to an embodiment of the present invention in a cross section by a plane perpendicular to the cylinder arrangement direction. FIG. 2 shows a cross section taken along line AA shown in FIG.
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. Two intake ports 15 and two exhaust ports 17 are juxtaposed in the cylinder arrangement direction for each cylinder (FIG. 2). The intake valve 16 and the exhaust valve 18 are respectively driven by an intake cam 19 and an exhaust cam 20 disposed above the valves 16 and 18.

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.
As shown in FIG. 2, in the present embodiment, the injector 21 is installed at a position slightly offset from the cylinder central axis m in the cylinder arrangement direction in a state inclined with respect to the cylinder central axis m. The arrangement of the injector 21 is due to a request to place both the injector 21 and the spark plug 22 close to the cylinder center axis m. Of course, the injector 21 may be installed on the cylinder center axis m, and the spark plug 22 may be installed farther from the cylinder center axis m than the position shown in FIG. 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. When the center line of the cone is the injection direction line n of the injector 21, the injection direction line n is directed to the center of the crown surface of the piston 12. In the present embodiment, the injection direction line n is inclined with respect to the cylinder center axis m because the injector 21 is offset from the cylinder center axis m. However, when the injector 21 is installed on the cylinder center axis m, The injection direction line n and the cylinder center axis m can be matched. The setting of the injection direction line n is not limited to these, and the injection direction line n is in a state parallel to or close to the cylinder central axis m and formed on the crown surface 121 of the piston 12 as will be described later. It suffices if the spraying is guided by the cavity c to form a longitudinal circulation flow so that the action described later can be obtained.

A cavity c is formed in the crown surface 121 of the piston 12 for guiding fuel spray injected by the injector 21 (hereinafter simply referred to as “spray”). In the present embodiment, the cavity c121 is formed in a circular shape with a cross section taken along a plane perpendicular to the cylinder central axis m, and the center thereof coincides with the cylinder central axis m.
FIG. 3 shows the configuration of the drive mechanism D of the injector 21 that constitutes the “injection point varying means” according to the present embodiment. In the present embodiment, as the “injection point” p of the injector 21, the centers of the injection holes arranged in the circumferential direction are employed.

  The drive mechanism D moves the injector 21 in the direction of an axis z parallel to the injection direction line n, and includes a hydraulic actuator 101 as a drive source. The injector 21 is inserted into a hole 131 formed in the cylinder head 13 from the tip, and is held in the hole 131 by a cover 132 attached to the cylinder head 13. The injector 21 is urged downward by a spring 102 mounted in a compressed state with the cover 132 and is pushed into the hole 131. The hydraulic actuator 101 supplies hydraulic oil into the hole 131 at a controlled pressure through a hydraulic passage 133 formed in the cylinder head 13. This hydraulic oil acts on the end face of the injector 21 and moves the injector 21 upward against the force of the spring 102. In the cylinder head 13, a recess 134 is formed continuously with the hole 131. The recess 134 has a wall surface formed in a tapered shape, and is enlarged as the area of a cross section perpendicular to the injection direction line n advances in the injection direction. The injection point p is always stored in the recess 134 regardless of its position. In the present embodiment, the drive mechanism D is configured as an external structure added to the injector 21, but the “injection point variable means” is configured as the internal structure of the injector 21, and the injection point is not moved without moving the injector 21 itself. p can also be moved.

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 connected to a camshaft (not shown) and is driven by the output of the engine 1.
Returning to FIG. 1, the operation of the engine 1 is integrally controlled by an engine control unit (hereinafter referred to as “ECU”) 31. The engine 1 detects the signal from the accelerator sensor 41 that detects the accelerator opening APO, the 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, and a signal from the fuel pressure sensor 44 installed in the fuel pipe 24 is input (FIG. 3). Based on these signals, the ECU 31 controls the fuel injection amount and injection timing of the injector 19 and the ignition timing of the spark plug 20 and adjusts the rotational speed of the fuel pump 23.

  In the present embodiment, the combustion mode is switched between homogeneous combustion and stratified combustion in accordance with the rotational speed and load of the engine 1. FIG. 5 shows a map of the combustion mode. FIG. 7 shows the in-cylinder state at the ignition timing for each combustion mode. The combustion mode is switched depending on the engine speed NE and the accelerator opening APO, and among the operating regions of the engine 1, homogeneous combustion is performed in the region C on the high rotation high load side, and stratified combustion is performed in regions A and B other than this region C. Selected. In homogeneous combustion, the air-fuel ratio is set to the stoichiometric air-fuel ratio, the fuel injection timing is set during the intake stroke, and the spray is diffused throughout the combustion chamber 14 to form an air-fuel mixture (FIG. 7c). On the other hand, 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 near the center of the combustion chamber 14, and the air-fuel mixture is It is formed in layers. Further, in the present embodiment, when stratified combustion is performed, the stratified combustion mode is further switched between the low load side region A and the high load side region B. That is, in the region A, the fuel injection timing is set to a timing near the compression top dead center, and ignition is performed on the spray before the collision with the crown surface 121 of the piston 12 (hereinafter referred to as “spray guide combustion”). ) Is selected (FIG. 7a). On the other hand, in the region B, the fuel injection timing is set to a relatively early timing during the compression stroke, and the air-fuel mixture formed by the spray guided by the cavity c of the piston 12 is ignited (hereinafter, “ (Referred to as “wall guide combustion”) (FIG. 7b). In the present embodiment, the area A corresponds to the “first area” and the area B corresponds to the “second area”. Further, the region C corresponds to a “third region”.

Next, the operation of the ECU 31 will be described with reference to a flowchart.
FIG. 4 is a flowchart of a combustion control routine. A combustion mode is selected by this routine, and a position of an injection point p (hereinafter referred to as “injection position”) Pinj is set. In the description of this routine, reference is made to FIG. 6 showing a table of the injection position Pinj, the injection timing Tinj, and the ignition timing Tign.

  In S101, it is determined whether or not the engine 1 is under start control. When the start control is being performed, the process proceeds to S110, and when the start control is not being performed, the process proceeds to S102. This start control is started when it is determined by the signal from the start switch or the like that the engine 1 is starting, and the fuel injection amount is increased by the increase correction value set according to the coolant temperature Tw, Combustion is performed at an air-fuel ratio lower than the stoichiometric air-fuel ratio. After start-up, the increase correction value is decreased as the cooling water temperature Tw rises. When the warm-up is completed, the routine shifts to normal combustion control and proceeds to S102 and thereafter.

In S102, the engine speed NE and the accelerator opening APO are read as the operating state of the engine 1.
In S103, area determination is performed. When it is determined that the operating state of the engine 1 is in the region A, the process proceeds to S104. When it is determined that the engine 1 is in the region B, the process proceeds to S106. When it is determined that the engine 1 is in the area C, the process proceeds to S108.

In S104, stratified combustion by spray guide combustion is selected.
In S <b> 105, the hydraulic actuator 101 is operated with the maximum set output, and the injection point P is raised to the position Pup farthest from the crown surface 121 of the piston 12.
In the case of spray guide combustion, the fuel injection timing Tinj is set to a timing near the compression top dead center, and is advanced as the accelerator opening APO increases or the engine speed NE increases. On the other hand, the injection point p is fixed at the rising position Pup. The injection position Pinj (in this case, the ascending position Pup) set in the region A by spray guide combustion corresponds to the “first position”.

In S106, stratified combustion by wall guide combustion is selected.
In S107, the output of the hydraulic actuator 101 is adjusted according to the operating state of the engine 1, and the injection point P is moved to a position corresponding to this operating state.
In the case of wall guide combustion, the fuel injection timing Tinj is set at a relatively early timing during the compression stroke, and is advanced according to an increase in the accelerator opening APO. Along with the transition from spray guide combustion to wall guide combustion, the ignition timing Tign is also advanced. The change width δ1 at this transition point is smaller than the change width δ2 of the injection timing Tinj. On the other hand, the injection point p is lowered to a predetermined position at a time along with the transition of this form, and is lowered as the accelerator opening APO is increased to approach the crown surface 121 of the piston 12. The injection position Pinj (changed according to the load or the like here) set in the region B by wall guide combustion corresponds to the “second position”.

In S108, homogeneous combustion is selected.
In S109, the hydraulic actuator 101 is operated with the maximum set output, and the injection point p is moved to the ascending position Pup.
In the case of homogeneous combustion, the fuel injection timing Tinj is set during the intake stroke, and the injection point p is fixed at the ascending position Pup. The injection position Pinj (in this case, the ascending position Pup) set in the region C by homogeneous combustion corresponds to the “third position”.

In S110, it is determined whether or not the cooling water temperature Tw is lower than a predetermined temperature Tw1 (for example, 20 ° C.) in starting control. When it is low, the process proceeds to S111. Otherwise, the process proceeds to S112.
In S <b> 111, the hydraulic actuator 101 is stopped and the injection point p is lowered to the position Pdown closest to the crown surface 121 of the piston 12. The injection position Pinj (here, the lowered position Pdown) set at the time of low temperature start corresponds to the “fourth position”.

In S112, the hydraulic actuator 101 is operated with the maximum set output, and the injection point p is moved to the ascending position Pup.
In S113, it is determined whether or not a failure has occurred in the drive mechanism D. This determination is performed by determining whether or not a misfire has occurred based on the engine speed NE or the in-cylinder pressure or the like during spray guide combustion (region A) in which the hydraulic actuator 101 is operated at the maximum set output. Can do. This is because if the injection point p is not sufficiently raised due to a failure during spray guide combustion, a rich mixture is formed by spraying with insufficient evaporation and mixing, which causes ignition failure.

In S114, the hydraulic actuator 101 is forcibly stopped, and the injection point p is moved to the lowered position Pdown. The injection position Pinj (here, the lowered position Pdown) set at the time of failure corresponds to the “fifth position”.
In S115, a failure mode is executed in which only the homogeneous combustion is performed at a rotational speed and a load that are limited to a narrow range compared to the normal time.

According to this embodiment, the following effects can be obtained.
First, in the present embodiment, the injection point p of the injector 21 is moved to the rising position Pup relatively far from the crown surface 121 in the region A due to the spray guide combustion. For this reason, the crown reachable distance l (FIG. 9a) of the spray can be secured, and the formation of a rich mixture that causes the generation of smoke and the deterioration of the combustion stability can be prevented.

  Second, in the present embodiment, the injection position Pinj is made different between the region A by spray guide combustion and the region B by wall guide combustion, and in this region B, the injection point p is set to be higher than that in the region A. It was decided to move to the lowered position Pdown close to the crown surface 121. For this reason, stable stratified combustion can be performed in both regions A and B. 8 and 9 show the in-cylinder state in the case of wall guide combustion when the injection point p is set to the lowered position Pdown (FIG. 8) and when it is set to the raised position Pup (FIG. 9). Yes.

  In the wall guide combustion, the fuel is injected into the cavity c formed in the crown surface 121 of the piston 12. Therefore, the fuel injection timing is determined by the geometry of the spray spread angle θ and the position of the piston 12. It is determined from the relationship. At high rotations where the actual time per cycle is short or at high loads where a long injection time is required, the injection timing must be advanced to inject the required amount of fuel. If the point p is kept elevated, the spray surface S reaches a long distance l, and the spray S may not fit in the cavity c (FIG. 9b). On the other hand, in the present embodiment, the injection point p is lowered during wall guide combustion and brought closer to the crown surface 121 (FIG. 8), so that the spray crown arrival distance l is shortened and the injection timing is advanced. Even if it makes it, the spray S can be stored in the cavity c, and the favorable air-fuel mixture mass M1 can be formed (FIGS. 8b and c). Further, since the injection point p is lowered as the load increases or the rotational speed increases, regardless of the operating state of the engine 1, the spray S is always injected into the cavity c to form the air-fuel mixture M1. can do.

  Thirdly, in the present embodiment, in the region C by homogeneous combustion, the injection point p is moved to the ascending position Pup, and the injector 21 is retracted from the combustion chamber 14 into the cylinder head 13. In the region C, the amount of fuel injection is large and the temperature in the cylinder is on average high. However, by retracting the injector 21 in this way, the influence of heat from the combustion chamber 14 on the injector 21 is suppressed. The injector 21 can be protected.

  Fourth, in the present embodiment, the injection point p is moved to the lowered position Pdown at the time of cold start. At the time of low temperature start, the temperature in the cylinder is low, and it is difficult for the injected fuel to evaporate. However, the evaporation is reduced by lowering the injection point p and actively removing the spark plug 22 from the fuel passage region. It is possible to prevent fuel in a state where the fuel is not sufficiently advanced from adhering to the spark plug 22.

  Fifth, in the present embodiment, the injection point p is moved to the lowered position Pdown at the time of failure. For this reason, combustion in a state where the injection point p is not fixed can be avoided, and ignition failure due to fuel adhering to the spark plug 22 can be prevented particularly at low temperatures. Further, in the present embodiment, the failure mode by homogeneous combustion is forcibly executed in conjunction with the movement of the injection point p, so that instability of combustion due to poor formation of the stratified mixture is prevented, and repair is possible. It is possible to ensure drivability until completion.

Next, another embodiment of the present invention will be described.
FIG. 10 shows the configuration of the engine 1B according to this embodiment, and FIG. 11 shows a cross section taken along line BB shown in FIG.
The structural difference from the engine 1A according to the previous embodiment is as follows.
That is, in the engine 1B, an inner cavity c1 is formed at the center of the crown surface as a cavity for guiding the spray on the crown surface 121 of the piston 12, and an outer cavity c2 is formed around the inner cavity c1. The inner cavity c1 is formed in a circular shape with a cross section of a plane perpendicular to the cylinder center axis m, and the center thereof is set at a position slightly offset from the cylinder center line m in the cylinder arrangement direction ( FIG. 11). The arrangement of the inner cavity c1 is associated with the injector 21 being offset from the cylinder center axis m. When the injector 21 is installed on the cylinder center axis m, the center of the inner cavity c1 is set to the cylinder center axis m. Can be matched. On the other hand, the outer cavity c2 is formed in an annular shape in the cross section, and its center coincides with the cylinder center axis m, unlike the inner cavity c1.

  In this embodiment, the combustion mode is switched between stratified combustion and homogeneous combustion, and in the case of stratified combustion, the configuration is further switched between spray guide combustion and wall guide combustion (FIG. 13). In the case of wall guide combustion, the cavity to be used is switched according to the load of the engine 1, and the inner cavity c1 is used in the region B1 where the load is lower than the predetermined load Tq1, while the outer cavity is used in the region B2 other than this. A mixed gas mass is formed using c2.

  FIG. 12 shows a part of a combustion control routine performed by the ECU 31 according to the present embodiment. This routine is executed by replacing the processing of S107 with the processing of S201 to S205 of FIG. 12 in the flowchart shown in FIG. FIG. 14 shows a table of the injection position Pinj, the injection timing Tinj, and the ignition timing Tign, and FIG. 14 is referred to when explaining the flowchart.

That is, in this embodiment, it is determined whether or not the load Tq is lower than the predetermined load Tq1 in the regions B1 and B2 due to wall guide combustion. If it is low, the operation state of the engine 1B is in the region B1, and the process proceeds to S202. Otherwise, the operation state is in the region B2, and the process proceeds to S204.
In S202, the time when the spray is directed to the inner cavity c1 is set as the fuel injection timing Tinj.

In S203, the injection point p is moved to a position corresponding to the operating state of the engine 1B.
In the region B1, since the fuel is injected toward the inner cavity c1, the fuel injection timing Tinj is set earlier than that in the region A due to spray guide combustion, and is advanced as the accelerator opening APO increases. The As described above, the width δ1 at which the ignition timing Tign is advanced with the transition from the spray guide combustion to the wall guide combustion is smaller than the width δ2 at which the injection timing Tinj is advanced with the transition from this form. It is. On the other hand, the injection point p is lowered to a predetermined position at a time along with the transition of this form, and is lowered as the accelerator opening APO is increased to approach the crown surface 121 of the piston 12.

In S204, the fuel injection timing Tinj is set to the time when the spray is directed to the outer cavity c2.
In S205, the injection point p is moved to a position corresponding to the operating state of the engine 1B, as in the region B1.
In the region B2, since the fuel is injected toward the outer cavity c2, the fuel injection timing Tinj is set earlier than that in the region B1 using the inner cavity c1, and the accelerator opening is performed as in the region B1. The angle is advanced as the degree APO increases. In order to reliably switch the cavity to be used between the inner cavity c1 and the outer cavity c2, the injection is performed at the minimum load (or minimum speed) point P1 of the region B2 than at the maximum load (or maximum speed) point P2 of the region B1. The point p is set at a position far from the crown surface 121 of the piston 12.

The injection position Pinj set in the regions B1 and B2 due to wall guide combustion corresponds to the “second position”.
According to this embodiment, the following effects can be obtained.
First, in this embodiment, two cavities c1 and c2 are formed in the crown surface 121 of the piston 12, and the cavities to be used are switched according to the operating state of the engine 1B. For this reason, when performing wall guide combustion, an air-fuel mixture having an appropriate size and air-fuel ratio can be formed in accordance with the operating state, and stable stratified combustion can be realized.

  Second, when the cavity to be used is switched between the inner cavity c1 and the outer cavity c2, for example, when the cavity to be used is switched from the inner cavity c1 to the outer cavity c2, the injection point p is changed to the crown surface of the piston 12. It was decided to move to a position farther from 121. For this reason, the spray is reliably stored in one of the cavities (here, the outer cavity c2), and the spray collides with the corner of the crown surface 121 formed at the boundary between the cavities c1 and c2. By being divided, it is possible to prevent the air-fuel mixture from becoming excessively diluted.

Configuration of a cylinder injection internal combustion engine according to an embodiment of the present invention Section along line AA in FIG. Injector drive mechanism configuration Flow chart of combustion control routine Combustion mode map related to the same routine Movement of injection point position, injection timing, and ignition timing according to the same routine The concept of stratified combustion (spray guide combustion, wall guide combustion) and homogeneous combustion Description of the effects of wall guide combustion according to the present invention Comparative example for FIG. Configuration of a cylinder injection internal combustion engine according to another embodiment of the present invention Section along line BB in FIG. Another example of flowchart of combustion control routine Combustion mode map related to the same routine Movement of injection point position, injection timing, and ignition timing according to the same routine

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A, 1B ... In-cylinder injection internal combustion engine, 11 ... Cylinder block, 12 ... Piston, 121 ... Crown surface of piston, 13 ... Cylinder head, 14 ... Combustion chamber, 15 ... Intake port, 16 ... Intake valve, 17 ... Exhaust Port, 18 ... Exhaust valve, 21 ... Injector, 22 ... Spark plug, 31 ... Engine control unit, 41 ... Accelerator sensor, 42 ... Crank angle sensor, 43 ... Coolant temperature sensor, 44 ... Fuel pressure sensor, 101 ... Hydraulic actuator , 102 ... Spring, 131 ... Nozzle hole, 132 ... Cover, 133 ... Hydraulic passage, c ... Cavity, c1 ... Inner cavity, c2 ... Outer cavity, m ... Cylinder central axis, n ... Injection direction line.

Claims (11)

An injector for fuel supply installed facing the crown of the piston;
A spark plug for igniting the fuel injected by the injector;
Injection point variable means for moving the injection point of the injector in its injection direction,
The injector is a relatively low load side of the engine operating range, and the injection timing is set during the compression stroke,
In the first region where the ignition plug is ignited with respect to the spray before the collision with the crown surface of the piston in the low load side region, the injection point varying means is configured to set the injection point to the crown of the piston. While setting the first position relatively far from the surface, in the second region set as a region other than the first region, the injection point is closer to the crown surface of the piston than the first position A direct injection internal combustion engine set to the second position. A cavity for guiding the spray is formed on the crown surface of the piston,
The injector is installed to face the cavity of the crown surface of the piston,
2. The direct injection internal combustion engine according to claim 1, wherein in the second region, the spark plug ignites an air-fuel mixture formed by the spray guided by the cavity.   The in-cylinder injection internal combustion engine according to claim 2, wherein, in the second region, the injection point varying means brings the injection point closer to the crown surface of the piston as the engine load is larger or the engine rotational speed is higher. organ. On the crown surface of the piston, as the cavity, an inner cavity at the center of the crown surface and an outer cavity around it are formed,
In the second region, in the low load region where the engine load is lower than the predetermined load, the time when the spray is directed to the inner cavity is set as the injection timing of the injector, while the engine load is the predetermined load. The in-cylinder injection internal combustion engine according to claim 2 or 3, wherein, in a high load region that is equal to or higher than a load, a time when the spray is directed toward the outer cavity is set as an injection time of the injector.   5. The injection point varying means brings the injection point closer to the crown surface of the piston as the load increases or the rotation speed increases in both the low load region and the high load region in the second region. The cylinder injection internal combustion engine described in 1.   In the second region, the injection point varying means sets the injection point at the minimum load or minimum speed point in the high load region more than the maximum load or maximum speed point in the low load region. The in-cylinder injection internal combustion engine according to claim 5, which is away from the cylinder.   7. The injector according to claim 1, wherein an injection timing of the injector is set during an intake stroke in a third region on a higher load side than a region on the low load side in an engine operation region. In-cylinder internal combustion engine.   8. The direct injection internal combustion engine according to claim 7, wherein in the third region, the injection point varying means sets the injection point to a third position farther from the crown surface of the piston than the second position.   The injection point varying means sets the injection point to a fourth position closer to the crown surface of the piston than the third position at the time of starting in a state where the temperature of the engine is lower than a predetermined temperature. The in-cylinder injection internal combustion engine according to claim 8. It further comprises failure detection means for detecting a failure of the injection point variable means,
When the failure of the injection point variable means is detected by this means, the injection point variable means sets the injection point at a fifth position closer to the crown surface of the piston than the first position. Item 10. The cylinder injection internal combustion engine according to any one of Items 1 to 9.   The engine operating range is limited at the time of the failure as compared with other normal times, and the injection timing of the injector is set during the intake stroke throughout the limited operating range. The in-cylinder injection internal combustion engine according to 10.

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