JP2020002863A - Fuel injection control device for diesel engine - Google Patents

Abstract

To suppress the generation of soot or others to the utmost by making effective use of air in a combustion chamber part of which is defined by a crown surface having cavities to form homogeneous and lean air-fuel mixture.SOLUTION: The bottom surface of a combustion chamber 6 of a diesel engine to be controlled is defined by a crown surface 50 including first and second cavity parts 51, 52, and a connection part 53 connecting both of them. A fuel injection control part 71 allows an injector 15 to execute main injection P1 or pilot injection P2 directed to the connection part 53, and low penetration injection P4 serving as fuel injection in a PILOT region at an earlier timing than the pilot injection P2 or in an AFTER region at a later timing than the main injection P1. The fuel injection control part 71 retards the injection timing for the low penetration injection P4 when an outside air temperature is high, compared to when it is low.SELECTED DRAWING: Figure 15

Description

  The present invention relates to a fuel injection control device for a diesel engine in which a part of a combustion chamber is defined by a crown surface of a piston having a cavity.

  A combustion chamber of a diesel engine for a vehicle such as an automobile is defined by an inner wall surface of a cylinder, a lower surface of a cylinder head (a ceiling surface of a combustion chamber), and a crown surface of a piston. Fuel is supplied to the combustion chamber from a fuel injection valve arranged near a radial center of the combustion chamber. There is known a combustion chamber structure in which a cavity (recess) is arranged on a crown surface of the piston, and fuel is injected from the fuel injection valve toward the cavity. Patent Documents 1 and 2 disclose that a fuel is injected into a branch portion of a two-stage cavity in a combustion chamber structure in which the cavity has a two-stage structure of an upper cavity and a lower cavity. A fuel injection control device that disperses fuel in a side cavity is disclosed.

French Patent Application Publication No. 2902462 Japanese Patent No. 4906055

  When the two-stage cavity is adopted, the in-cylinder flow of the air-fuel mixture containing the fuel injected from the fuel injection valve is separated into a flow toward the upper cavity and a flow toward the lower cavity at the branch portion, A swirling flow is formed in each cavity. In the case of a single-stage cavity, a relatively strong swirling flow is formed along the cavity since the separation does not occur. In comparison, the swirling flow of the two-stage cavity is relatively weak due to the separation. For this reason, there is a tendency that the air existing in the radially central region of the combustion chamber is hardly drawn into the radially outside of the combustion chamber by the swirling flow. In this case, there is a problem that the air utilization rate decreases, that is, oxygen remaining in the radially central region of the combustion chamber cannot be effectively used.

  The present invention relates to a fuel injection control device for a diesel engine having a cavity in a crown surface of a piston, which forms a homogeneous and thin air-fuel mixture by effectively utilizing air in a combustion chamber to reduce generation of soot and the like. It is an object of the present invention to provide a fuel injection control device capable of suppressing the fuel injection.

  A fuel injection control device for a diesel engine according to one aspect of the present invention includes a combustion chamber of an engine formed by a lower surface of a cylinder head, a crown surface of a cylinder and a piston, and a fuel injection valve that injects fuel into the combustion chamber. A fuel injection control unit for controlling the operation of the fuel injection valve, a fuel injection control device for a diesel engine, wherein a cavity is provided in a crown surface of the piston, the cavity is a radial direction of the crown surface A first cavity portion disposed in a central region and having a first bottom portion having a first depth in a cylinder axis direction; and a first cavity portion disposed on an outer peripheral side of the first cavity portion on the crown surface, and disposed in the cylinder axis direction. A second cavity portion having a second bottom portion having a depth smaller than the first depth, and a connecting portion connecting the first cavity portion and the second cavity portion. The fuel injection valve is for injecting fuel toward the cavity, and is disposed at or near a radial center of the combustion chamber, and the fuel injection control unit determines that at least the piston is near a compression top dead center. The main injection for performing the fuel injection at a timing located at the timing, the pilot injection for performing the fuel injection at a timing earlier than the main injection, and the fuel injection at a timing earlier than the pilot injection or a timing later than the main injection. And performing the low penetration injection to be performed by the fuel injection valve, wherein at least one of the main injection or the pilot injection is performed at a timing when the fuel injection is directed toward the connection portion. And the low penetration injection only in the radially central region of the combustion chamber. A second injection control unit configured to execute the fuel injection so that the injection timing of the low-penetration injection is retarded when the outside air temperature is high as compared to when the outside air temperature is low, It is characterized by the following.

  According to this fuel injection control device, a part of the combustion chamber is formed by the crown surface including the first and second cavities, and the fuel injection of the main injection or the pilot injection is performed by pointing to the connection portion. Is done. For this reason, the in-cylinder flow of the air-fuel mixture is separated at the connecting portion, the in-cylinder swirling flow becomes relatively weak, and air near the radially central region of the combustion chamber tends to be hardly drawn outward in the radial direction. However, according to the fuel injection control device, low penetration injection is executed in addition to the normal main injection and pilot injection. The low penetration injection is performed such that fuel injection is performed only in a radially central region of the combustion chamber. Therefore, an air-fuel mixture can be formed by the air remaining in the radially central region of the combustion chamber and the fuel sprayed by the low penetration injection. As a result, a homogeneous and thin air-fuel mixture is formed by effectively utilizing the air in the combustion chamber, and high-quality diesel combustion in which generation of soot and the like is suppressed can be realized.

  Here, when the outside air temperature is high, premature ignition in which the air-fuel mixture starts burning at a timing earlier than a desired timing is likely to occur as the ignitability of the air-fuel mixture increases. On the other hand, in this device, when the outside air temperature is high, the low penetration injection is executed such that the injection timing of the low penetration injection is on the retard side as compared with when the outside air temperature is low. Therefore, premature ignition can be prevented from occurring when the outside air temperature is high. Further, when the outside air temperature is low and the ignitability is low, the injection timing of the low penetration injection is set to the advanced timing, so that the mixing of fuel and air is promoted and the air-fuel mixture is appropriately burned. it can.

  In the configuration, when the outside air temperature is lower than a predetermined reference temperature, the second injection control unit causes the low penetration injection to be executed at a timing earlier than the pilot injection. When the temperature is equal to or higher than the reference temperature, it is desirable to execute the low penetration injection at a timing later than the main injection (claim 2).

  According to this configuration, when the outside air temperature is lower than the reference temperature and the ignitability of the air-fuel mixture is relatively low, the low penetration injection is executed earlier than the pilot injection. Therefore, it is possible to more reliably obtain the energy of the fuel related to the low penetration injection as an effective torque while avoiding the occurrence of premature ignition. That is, fuel efficiency can be improved.

  Moreover, when the outside air temperature is equal to or higher than the reference temperature and the ignitability of the air-fuel mixture is relatively high, the low penetration injection is executed at a timing later than the main injection. Therefore, the fuel related to the low penetration injection can be burned after the start of the combustion of the fuel related to the main injection, and the premature ignition of the air-fuel mixture related to the main injection accompanying the execution of the low penetration injection can be prevented. Also, when the outside air temperature is high, soot is likely to be generated as the density of intake air (air supplied to the combustion chamber) is low (as the charging efficiency is lowered). On the other hand, by the combustion of the fuel related to the low penetration injection, the soot generated during the combustion of the fuel related to the main injection can be removed by combustion.

  In the above configuration, the second injection control unit executes the low penetration injection at a timing earlier than the pilot injection, and delays the injection timing of the low penetration injection when the outside air temperature is high as compared with when the outside air temperature is low. It is desirable to make a corner (claim 3).

  According to this configuration, the low-penetration injection is executed at a timing earlier than the pilot injection, so that the energy of the fuel related to the low-penetration injection can be effectively obtained as torque, and the fuel efficiency can be improved. In addition, when the outside air temperature is high, the injection timing of the low penetration injection is retarded as compared with when the outside air temperature is low. Therefore, when the outside air temperature is high, the mixing of the fuel and the air related to the low penetration injection is excessively promoted and excessively. Premature ignition can be prevented. Further, when the outside air temperature is low, the mixing can be promoted to burn the fuel related to the low penetration injection at an appropriate timing.

  As a configuration different from the above, the second injection control unit executes the low penetration injection at a timing later than the main injection, and, when the outside air temperature is high, the injection of the low penetration injection as compared with when the outside air temperature is low. The timing may be retarded (claim 4).

  According to this configuration, the low penetration injection is executed at a timing later than the main injection, so that the soot can be burned and removed by the fuel related to the low penetration injection.

  In addition, when the outside air temperature is high, the injection timing of the low penetration injection is retarded as compared with when the outside air temperature is low, so that it is possible to more reliably burn and remove soot and suppress deterioration in fuel efficiency. Specifically, when the outside air temperature is high as described above, soot is easily generated. On the other hand, when the outside air temperature is high, the low-penetration injection is executed at a later time, so that after a large amount of soot is generated, the combustion energy generated by the low-penetration injection can be effectively added to this soot. Further, when the outside air temperature is low and the amount of generated soot is relatively small, the deterioration of fuel efficiency can be suppressed by performing soot relatively early while burning and removing soot by low penetration injection.

  In the above configuration, it is preferable that the second injection control unit executes the low penetration injection so that an outer edge of the radially central region of the combustion chamber becomes a spray penetration (claim 5).

  According to this configuration, the position of the outer edge of the radial center region of the combustion chamber is set as a target of the spray penetration. Therefore, the air-fuel mixture can be formed by making full use of the air existing in the radial center region, and as a result, the generation of soot and the like can be further suppressed.

  In the above configuration, the second injection control unit may control the oxygen generated in a radially central region of the combustion chamber based on an injection pressure, an injection amount, and an injection timing of the main injection or the pilot injection by the first injection control unit. It is desirable to estimate a remaining area and to execute the low penetration injection so that the outer edge of the oxygen remaining area becomes a spray penetration (claim 6).

  According to this configuration, the oxygen remaining area in which the oxygen to be used remains is estimated from the injection control result by the first injection control unit, and the low penetration injection is executed in the estimated oxygen remaining area. Is done. Therefore, it is possible to realize combustion that makes effective use of the residual oxygen in the combustion chamber.

  According to the present invention, there is provided a fuel injection control device for a diesel engine capable of forming a homogeneous and thin air-fuel mixture by effectively utilizing air in a combustion chamber and suppressing generation of soot and the like as much as possible. Can be.

FIG. 1 is a system diagram of a diesel engine to which the fuel injection control device according to the present invention is applied. FIG. 2A is a perspective view of a crown portion of the piston of the diesel engine shown in FIG. 1, and FIG. 2B is a perspective view of the piston with a cross section. FIG. 3 is an enlarged view of the cross section of the piston shown in FIG. FIG. 4 is a cross-sectional view of the piston for explaining the relationship between the crown surface of the piston and the fuel injection axis of the injector. FIG. 5 is a block diagram showing a control system of the diesel engine. FIG. 6A is a diagram schematically illustrating an in-cylinder swirl flow when the cavity according to the comparative example is employed, and FIG. 6B is a diagram illustrating the in-cylinder swirl flow when the cavity according to the present embodiment is employed. It is a figure which shows typically. FIG. 7A shows the state of generation of residual air in the combustion chamber when the cavity according to the comparative example is employed, and FIG. 7B shows the residual air in the combustion chamber when the cavity according to the present embodiment is employed. FIG. 2 is a cross-sectional view of a combustion chamber, each showing a state of occurrence of the combustion. FIG. 8 is a cross-sectional view of the combustion chamber showing an execution state of low penetration injection in the present embodiment. FIGS. 9A to 9C are diagrams for explaining a method of setting a target line for low penetration injection. FIGS. 10A to 10D are time charts showing a mode of low penetration injection according to the first embodiment. FIG. 11 is a flowchart illustrating the low penetration injection control according to the first embodiment. FIG. 12 is a diagram showing control divisions in the low penetration injection control according to the second embodiment. FIGS. 13A to 13E are time charts showing a mode of low penetration injection according to the second embodiment. FIGS. 14A to 14D are time charts showing a mode of low penetration injection according to the second embodiment. FIG. 15 is a flowchart illustrating a part of the low penetration injection control according to the second embodiment. FIG. 16 is a flowchart illustrating a part of the low penetration injection control according to the second embodiment. FIG. 17 is a flowchart illustrating a part of the low penetration injection control according to the second embodiment. FIG. 18 is a flowchart illustrating a part of the low penetration injection control according to the second embodiment.

[Overall configuration of engine]
Hereinafter, an embodiment of a fuel injection control device for a diesel engine according to the present invention will be described in detail with reference to the drawings. First, the overall configuration of a diesel engine system to which the fuel injection control device according to the present invention is applied will be described with reference to FIG. The diesel engine shown in FIG. 1 is a four-cycle diesel engine mounted on a vehicle as a power source for traveling. The diesel engine system includes an engine body 1 having a plurality of cylinders 2 and driven by receiving a fuel mainly composed of light oil, an intake passage 30 through which intake air introduced into the engine body 1 flows, an engine body An exhaust passage 40 through which the exhaust gas discharged from the exhaust gas 1 flows, an EGR device 44 that recirculates a part of the exhaust gas flowing through the exhaust passage 40 to the intake passage 30, and an exhaust gas passing through the exhaust passage 40 are driven. The turbocharger 46 is provided.

  The engine body 1 has a plurality of cylinders 2 (only one of them is shown in FIG. 1) arranged in a direction perpendicular to the paper surface of FIG. 1, and is driven by supplying a fuel mainly composed of light oil. Engine. The engine body 1 includes a cylinder block 3, a cylinder head 4, and a piston 5. The cylinder block 3 has a cylinder liner forming the cylinder 2. The cylinder head 4 is attached to an upper surface of the cylinder block 3 and closes an upper opening of the cylinder 2. The piston 5 is accommodated in the cylinder 2 so as to be able to slide back and forth, and is connected to the crankshaft 7 via a connecting rod 8. In response to the reciprocating movement of the piston 5, the crankshaft 7 rotates around its central axis. The structure of the piston 5 will be described later in detail.

  A combustion chamber 6 is formed above the piston 5. The combustion chamber 6 is formed by the lower surface of the cylinder head 4 (combustion chamber ceiling surface 6U, see FIGS. 3 and 4), the cylinder 2 and the crown surface 50 of the piston 5. The fuel is supplied to the combustion chamber 6 by injection from an injector 15 described later. Then, a mixture of the supplied fuel and air is burned in the combustion chamber 6, and the piston 5 pushed down by the expansion force due to the combustion reciprocates in the vertical direction.

  The cylinder block 3 is provided with a crank angle sensor SN1 and a water temperature sensor SN2. The crank angle sensor SN1 detects a rotation angle of the crankshaft 7 (crank angle) and a rotation speed of the crankshaft 7 (engine rotation speed). The water temperature sensor SN2 detects the temperature of the cooling water flowing through the cylinder block 3 and the cylinder head 4 (engine water temperature).

  An intake port 9 and an exhaust port 10 communicating with the combustion chamber 6 are formed in the cylinder head 4. On the lower surface of the cylinder head 4, an intake-side opening, which is a downstream end of the intake port 9, and an exhaust-side opening, which is an upstream end of the exhaust port 10, are formed. An intake valve 11 for opening and closing the intake side opening and an exhaust valve 12 for opening and closing the exhaust side opening are attached to the cylinder head 4. Although illustration is omitted, the valve type of the engine body 1 is a four-valve type of two intake valves × two exhaust valves, and two intake ports 9 and two exhaust ports 10 are provided for each cylinder 2. In addition, two intake valves 11 and two exhaust valves 12 are provided.

  The cylinder head 4 is provided with an intake-side valve operating mechanism 13 including a camshaft and an exhaust-side valve operating mechanism 14. The intake valve 11 and the exhaust valve 12 are driven to open and close by the valve operating mechanisms 13 and 14 in conjunction with the rotation of the crankshaft 7. The intake-side valve operating mechanism 13 includes an intake VVT that can change at least the opening timing of the intake valve 11, and the exhaust-side valve operating mechanism 14 includes an exhaust VVT that can change at least the closing timing of the exhaust valve 12. Have been.

  An injector 15 (fuel injection valve) for injecting fuel from the tip into the combustion chamber 6 is attached to the cylinder head 4, one for each cylinder 2. The injector 15 injects fuel supplied through a fuel supply pipe (not shown) into the combustion chamber 6. The injector 15 is assembled to the cylinder head 4 such that the tip (nozzle 151; FIG. 4) for injecting fuel is located at or near the radial center of the combustion chamber 6, and is formed on the crown surface 50 of the piston 5. The fuel is injected toward a cavity 5C (FIGS. 2 to 4) described later.

  The injector 15 is connected to a common rail for accumulating pressure (not shown) common to all the cylinders 2 via a fuel supply pipe. High-pressure fuel pressurized by a fuel pump (not shown) is stored in the common rail. The fuel stored in the common rail is supplied to the injectors 15 of the cylinders 2, so that the fuel is injected from the injectors 15 into the combustion chamber 6 at a high pressure (about 50 MPa to 250 MPa). Between the fuel pump and the common rail, a fuel pressure regulator 16 (not shown in FIG. 1, see FIG. 5) for changing an injection pressure which is a pressure of fuel injected from the injector 15 is provided.

  The intake passage 30 is connected to one side surface of the cylinder head 4 so as to communicate with the intake port 9. Air (fresh air) taken in from the upstream end of the intake passage 30 is introduced into the combustion chamber 6 through the intake passage 30 and the intake port 9. In the intake passage 30, an air cleaner 31, a turbocharger 46, a throttle valve 32, an intercooler 33, and a surge tank 34 are arranged in this order from the upstream side.

  The air cleaner 31 cleans the intake air by removing foreign substances in the intake air. The throttle valve 32 opens and closes the intake passage 30 in conjunction with a depression operation of an unillustrated accelerator, and adjusts a flow rate of intake air in the intake passage 30. The turbocharger 46 sends out the intake air to the downstream side of the intake passage 30 while compressing the intake air. The intercooler 33 cools the intake air compressed by the supercharger 46. The surge tank 34 is disposed immediately upstream of the intake manifold connected to the intake port 9 and provides a space for uniformly distributing intake air to the plurality of cylinders 2.

The intake passage 30, an air flow sensor SN3, an intake air temperature sensor SN4, the intake pressure sensor SN5 and the intake _{O 2} sensor SN6 is disposed. The airflow sensor SN3 is disposed downstream of the air cleaner 31 and detects the flow rate of intake air passing through the portion. The intake air temperature sensor SN4 is arranged downstream of the intercooler, and detects the temperature of intake air passing through the portion. Intake pressure sensor SN5 and the intake O ₂ sensor SN6 is disposed in the vicinity of the surge tank 34, the pressure of the intake air respectively passing through the portion, for detecting the oxygen concentration of the intake air. Although not shown in FIG. 1, an injection pressure sensor SN7 for detecting the injection pressure of the injector 15 is provided.

  The exhaust passage 40 is connected to the other side surface of the cylinder head 4 so as to communicate with the exhaust port 10. The burned gas (exhaust gas) generated in the combustion chamber 6 is discharged to the outside of the vehicle through the exhaust port 10 and the exhaust passage 40. An exhaust purification device 41 is provided in the exhaust passage 40. The exhaust purification device 41 includes a three-way catalyst 42 for purifying harmful components (HC, CO, NOx) contained in the exhaust gas flowing through the exhaust passage 40 and a particulate matter contained in the exhaust gas. And a DPF (diesel particulate filter) 43 for collecting.

The exhaust passage 40, exhaust _{O 2} sensor SN8 and a differential pressure sensor SN9 is disposed. Exhaust O ₂ sensor SN8 is disposed between the exhaust gas purifying device 41 and the turbocharger 46, for detecting the oxygen concentration of exhaust passing through the portion. The differential pressure sensor SN9 detects a differential pressure between the upstream end and the downstream end of the DPF 43.

  The EGR device 44 includes an EGR passage 44A that connects the exhaust passage 40 and the intake passage 30, and an EGR valve 45 provided in the EGR passage 44A. The EGR passage 44 </ b> A connects a portion of the exhaust passage 40 upstream of the turbocharger 46 with a portion of the intake passage 30 between the intercooler 33 and the surge tank 34. An EGR cooler (not shown) that cools exhaust gas (EGR gas) recirculated from the exhaust passage 40 to the intake passage 30 by heat exchange is disposed in the EGR passage 44A. The EGR valve 45 adjusts the flow rate of exhaust gas flowing through the EGR passage 44A.

  The turbocharger 46 includes a compressor 47 disposed on the intake passage 30 side and a turbine 48 disposed on the exhaust passage 40. The compressor 47 and the turbine 48 are connected so as to be integrally rotatable on a turbine shaft. The turbine 48 rotates by receiving the energy of the exhaust gas flowing through the exhaust passage 40. When the compressor 47 rotates in conjunction with this, the air flowing through the intake passage 30 is compressed (supercharged).

[Detailed structure of piston]
Subsequently, the structure of the piston 5, particularly the structure of the crown surface 50, will be described in detail. FIG. 2A is a perspective view mainly showing an upper portion of the piston 5. The piston 5 includes an upper piston head and a lower skirt portion. FIG. 2A shows the piston head portion having a crown surface 50 on a top surface. FIG. 2B is a perspective view of the piston 5 with a radial cross section. FIG. 3 is an enlarged view of a radial cross section shown in FIG. 2A and 2B, the cylinder axial direction A and the combustion chamber radial direction B are indicated by arrows. Hereinafter, a description will be given of a plane perpendicular to the cylinder axis as a horizontal plane (assuming that the piston 5 is arranged such that a plane perpendicular to the cylinder axis is a horizontal plane).

  The piston 5 includes a cavity 5C, a peripheral flat surface portion 55, and a side peripheral surface 56. As described above, a part (bottom surface) of the combustion chamber wall defining the combustion chamber 6 is formed by the crown 50 of the piston 5, and the cavity 5 </ b> C is provided in the crown 50. The cavity 5C is a portion in which the crown surface 50 is recessed downward in the cylinder axial direction A, and is a portion that receives fuel injection from the injector 15. The peripheral flat surface portion 55 is an annular flat surface portion arranged in a region near the outer peripheral edge in the radial direction B on the crown surface 50. The cavity 5 </ b> C is arranged in a central region in the radial direction B of the crown surface 50 excluding the peripheral flat surface portion 55. The side peripheral surface 56 is a surface that comes into sliding contact with the inner wall surface of the cylinder 2 and includes a plurality of ring grooves into which a piston ring (not shown) is fitted.

  The cavity 5C includes a first cavity portion 51, a second cavity portion 52, a connection portion 53, and a peak portion. The first cavity portion 51 is a concave portion arranged in a central region of the crown surface 50 in the radial direction B. The second cavity portion 52 is an annular concave portion disposed on the outer peripheral side of the first cavity portion 51 on the crown surface 50. The connecting portion 53 is a portion that connects the first cavity portion 51 and the second cavity portion 52 in the radial direction B. The peak 54 is a mountain-shaped projection disposed at a center position in the radial direction B of the crown surface 50 (the first cavity 51). The peak 54 protrudes from a position directly below the nozzle 151 of the injector 15 (FIG. 4).

  The first cavity 51 includes a first upper end 511, a first bottom 512, and a first inner end 513. The first upper end portion 511 is at the highest position in the first cavity portion 51 and is connected to the connecting portion 53. The first bottom portion 512 is an annular region in the first cavity portion 51 which is the most concave and concave in a top view. In the entire cavity 5C, the first bottom portion 512 is the deepest portion, and the first cavity portion 51 has a predetermined depth (first depth) in the cylinder axis direction A at the first bottom portion 512. I have. In top view, the first bottom portion 512 is at a position close to the inside of the connecting portion 53 in the radial direction B.

  The first upper end 511 and the first bottom 512 are connected by a radial recess 514 curved outward in the radial direction B. The radial recess 514 has a portion that is recessed outside the connecting portion 53 in the radial direction B. The first inner end portion 513 is located at the radially innermost position in the first cavity portion 51 and is continuous with the lower end of the peak portion 54. The first inner end 513 and the first bottom 512 are connected by a gently curved curved surface in a skirt shape.

  The second cavity 52 includes a second inner end 521, a second bottom 522, a second upper end 523, a tapered region 524, and a standing wall region 525. The second inner end portion 521 is located at the radially innermost position in the second cavity portion 52 and is continuous with the connecting portion 53. The second bottom 522 is a region that is most concave in the second cavity 52. The second cavity 52 has a depth that is smaller than the first bottom 512 in the cylinder axis direction A at the second bottom 522. That is, the second cavity portion 52 is a concave portion located above the first cavity portion 51 in the cylinder axial direction A. The second upper end portion 523 is located at the highest position in the second cavity portion 52 and at the outermost position in the radial direction, and is continuous with the peripheral flat surface portion 55.

  The tapered region 524 is a portion that extends from the second inner end portion 521 toward the second bottom portion 522 and has a surface shape that is inclined outward and downward in the radial direction. As shown in FIG. 3, the tapered region 524 extends along a slope line C2 that intersects a horizontal line (a line along a plane orthogonal to the cylinder axis A) C1 extending in the radial direction B at an inclination angle α. It has a slope. The standing wall region 525 is a wall surface formed to rise relatively steeply outside the second bottom portion 522 in the radial direction. In the cross-sectional shape in the radial direction B, the wall surface of the second cavity portion 52 is curved from the horizontal direction to the upper direction from the second bottom portion 522 to the second upper end portion 523, and the second upper end portion is formed. The portion of the wall near the vertical wall near the vertical wall 523 is the standing wall region 525.

  The connecting portion 53 has a shape that protrudes radially inward in a radially inward shape between the first cavity portion 51 located on the lower side and the second cavity portion 52 located on the upper side in the cross-sectional shape in the radial direction B. are doing. The connecting portion 53 has a lower end portion 531 and a third upper end portion 532 (an upper end portion in the cylinder axis direction), and a central portion 533 located at a center therebetween. The lower end portion 531 is a portion provided continuously with the first upper end portion 511 of the first cavity portion 51. The third upper end 532 is a portion provided continuously with the second inner end 521 of the second cavity 52.

  In the cylinder axial direction A, the lower end 531 is the lowermost portion of the connecting portion 53, and the third upper end 532 is the uppermost portion. The above-described tapered region 524 is also a region extending from the third upper end 532 toward the second bottom 522. The second bottom 522 is located lower than the third upper end 532. That is, the second cavity portion 52 of the present embodiment does not have a bottom surface that extends horizontally outward in the radial direction B from the third upper end portion 532, in other words, the peripheral flat surface portion extends from the third upper end portion 532. 55 is not connected in a horizontal plane, but has a second bottom 522 that is recessed below the third upper end 532.

  The peak 54 protrudes upward, but the protruding height is the same as the height of the third upper end 532 of the connecting portion 53, and is located at a position depressed from the peripheral flat surface 55. The peak portion 54 is located at the center of the first cavity portion 51 which is circular in a top view, whereby the first cavity portion 51 has a shape of an annular groove formed around the peak portion 54.

[In-cylinder flow after fuel injection]
Next, the state of fuel injection into the cavity 5C by the injector 15 and the flow of the air-fuel mixture after the injection will be described with reference to FIG. FIG. 4 is a simplified cross-sectional view of the combustion chamber 6, showing the relationship between the crown surface 50 (cavity 5C) and the injection axis AX of the injected fuel 15E injected from the injector 15, and the flow of the air-fuel mixture after the injection. Are schematically shown as arrows F11, F12, F13, F21, F22 and F23.

  The injector 15 includes a nozzle 151 disposed so as to protrude downward from the combustion chamber ceiling surface 6U (the lower surface of the cylinder head 4) to the combustion chamber 6. The nozzle 151 has an injection hole 152 for injecting fuel into the combustion chamber 6. FIG. 4 shows one injection hole 152, but actually a plurality of injection holes 152 are arranged at equal pitches in the circumferential direction of the nozzle 151. Fuel injected from the injection hole 152 is injected along the injection axis AX in the figure. The injected fuel diffuses with the spray angle θ. FIG. 4 shows an upper diffusion axis AX1 indicating upward diffusion with respect to the injection axis AX, and a lower diffusion axis AX2 indicating downward diffusion. The spray angle θ is an angle formed by the upper diffusion axis AX1 and the lower diffusion axis AX2. The fuel injected from the injection hole 152 scatters through a region between the upper diffusion axis AX1 and the lower diffusion axis AX2 in a side view. Note that the injection axis AX is the central axis of the fuel spray injected from the injector 15 and substantially coincides with the extension of the central axis of the injection hole 152.

  The injection hole 152 is capable of injecting fuel toward the connecting portion 53 of the cavity 5C. That is, by performing the fuel injection operation from the injection hole 152 at a predetermined crank angle of the piston 5, the injection axis AX can be directed to the connecting portion 53. FIG. 4 shows the positional relationship between the injection shaft AX and the cavity 5C at the predetermined crank angle. The fuel injected from the injection holes 152 is blown against the connecting portion 53 while being mixed with the air in the combustion chamber 6 to form an air-fuel mixture.

  As shown in FIG. 4, the fuel 15 </ b> E injected toward the connecting portion 53 along the injection axis AX collides with the connecting portion 53, and then goes toward the first cavity portion 51 (downward) ( It is spatially separated into an arrow F11) and a direction toward the second cavity 52 (upward) (arrow F21). That is, the fuel injected toward the central portion 533 of the connecting portion 53 is vertically separated and thereafter mixed with the air existing in the first and second cavities 51 and 52, respectively. , 52 along the surface shape.

  Specifically, the air-fuel mixture flowing in the direction of the arrow F11 (downward) enters the radial recess 514 of the first cavity portion 51 from the lower end 531 of the connecting portion 53 and flows downward. Thereafter, the air-fuel mixture changes the flow direction from the downward direction to the inner side in the radial direction B by the curved shape of the radial recess 514, and as shown by an arrow F12, the bottom surface of the first cavity portion 51 having the first bottom portion 512. It flows according to its shape. At this time, the air-fuel mixture is mixed with the air in the first cavity portion 51 to decrease the concentration. Due to the presence of the peaks 54, the bottom surface of the first cavity 51 has a shape that rises toward the center in the radial direction. Accordingly, the air-fuel mixture flowing in the direction of arrow F12 is lifted upward, and finally flows outward from the ceiling surface 6U of the combustion chamber in the radial direction as indicated by arrow F13. Even during such a flow, the air-fuel mixture mixes with the air present in the combustion chamber 6 and becomes a homogeneous and thin air-fuel mixture.

  On the other hand, the air-fuel mixture flowing in the direction of the arrow F21 (upward) enters the tapered region 524 of the second cavity portion 52 from the third upper end portion 532 of the connecting portion 53, and goes obliquely downward along the inclination of the tapered region 524. . Then, as indicated by an arrow F22, the air-fuel mixture reaches the second bottom portion 522. Here, the tapered region 524 is a surface having an inclination along the injection axis AX. For this reason, the air-fuel mixture can smoothly flow radially outward. That is, the air-fuel mixture reaches the deep position radially outside the combustion chamber 6 due to the presence of the tapered region 524 and the second bottom portion 522 where the third upper end portion 532 of the connecting portion 53 is also located below. Can be.

  Thereafter, the air-fuel mixture is lifted upward by the rising curved surface between the second bottom portion 522 and the rising wall region 525, and flows radially inward along the combustion chamber ceiling surface 6U. At the time of such a flow indicated by the arrow F22, the air-fuel mixture is mixed with the air in the second cavity 52, and becomes a homogeneous and thin air-fuel mixture. Here, the presence of the upright wall region 525 extending substantially vertically in the radially outer side of the second bottom portion 522 allows the injected fuel (air-fuel mixture) to flow into the inner peripheral wall of the cylinder 2 (generally, a liner not shown). Is present). That is, the air-fuel mixture can flow to the vicinity of the radial outside of the combustion chamber 6 due to the formation of the second bottom portion 522, but the presence of the standing wall region 525 suppresses interference with the inner peripheral wall of the cylinder 2. Therefore, it is possible to suppress the occurrence of the cooling loss due to the interference.

  As described above, the fuel injected toward the connecting portion 53 along the injection axis AX collides with the connecting portion 53 and is spatially separated and exists in the spaces of the first and second cavities 51 and 52, respectively. The air mixture is utilized to generate an air-fuel mixture. Thereby, a uniform and thin air-fuel mixture can be formed by widely utilizing the space of the combustion chamber 6, and generation of soot and the like during combustion can be suppressed.

[Control configuration]
FIG. 5 is a block diagram showing a control configuration of the diesel engine system. The engine system of the present embodiment is generally controlled by a processor 70 (a fuel injection control device for a diesel engine). The processor 70 includes a CPU, a ROM, a RAM, and the like. Detection signals from various sensors mounted on the vehicle are input to the processor 70. In addition to the sensors SN1 to SN9 described above, the vehicle includes an accelerator opening sensor SN10 that detects an accelerator opening, an atmospheric pressure sensor SN11 that measures the atmospheric pressure of the traveling environment of the vehicle, and an outside air temperature, that is, the traveling of the vehicle. And an outside temperature sensor SN12 for measuring the temperature of the environment.

Processor 70, a crank angle sensor SN1 described above, the water temperature sensor SN2, airflow sensor SN3, an intake air temperature sensor SN4, the intake pressure sensor SN5, the intake _{O 2} sensor SN6, injection pressure sensor SN7, the exhaust _{O 2} sensor SN8, the differential pressure sensor SN9 , The accelerator opening sensor SN10, the atmospheric pressure sensor SN11, and the outside air temperature sensor SN12. Information detected by these sensors SN1 to SN12, namely, crank angle, engine rotation speed, engine water temperature, intake flow rate, intake temperature, intake pressure, intake oxygen concentration, injector 15 injection pressure, exhaust oxygen concentration, before and after DPF 43 Information such as the differential pressure, the accelerator opening, the outside air temperature, and the atmospheric pressure is sequentially input to the processor 70. The intake pressure sensor SN5 is provided downstream of the compressor 47, and the intake pressure detected by the intake pressure sensor SN5 is the same as the supercharging pressure. Hereinafter, the intake pressure may be referred to as a supercharging pressure.

  The processor 70 controls various parts of the engine while executing various determinations and calculations based on input signals from the sensors SN1 to SN12 and others. That is, the processor 70 is electrically connected to the injector 15 (fuel pressure regulator 16), the throttle valve 32, the EGR valve 45, and the like, and outputs a control signal to each of these devices based on the result of the calculation and the like. I do.

  The processor 70 functionally includes a fuel injection control unit 71 (first injection control unit, second injection control unit) that controls the operation of the injector 15. In the present embodiment, the fuel injection control unit 71 includes at least a main injection for performing the fuel injection at a timing when the piston 5 is located near the compression top dead center, and a pilot injection for performing the fuel injection at a timing earlier than the main injection. And a low penetration injection for injecting fuel at a timing earlier than the pilot injection or later than the main injection.

  Here, the main injection and the pilot injection are fuel injections generally used in the conventional combustion control. There are many forms of these injections. After injection may be performed at a timing later than the main injection to suppress soot. In addition to these injections, the present embodiment is characterized in that low penetration injection is performed in which the penetration is more restricted than other injections. As will be described in detail later, the low penetration injection is a fuel injection for effectively utilizing air (oxygen) remaining in the radially central region of the combustion chamber 6. The fuel injection control unit 71 performs a first injection control for executing at least one of the main injection and the pilot injection at a timing of injecting fuel in a direction directed to the connecting portion 53 of the cavity 5C, and performs the low penetration injection in a combustion chamber. And a second injection control that is executed so that fuel injection is performed only in the radial center region of No. 6.

  The fuel injection control unit 71 functionally includes an injection range setting unit 72, an operation state determination unit 73, a remaining oxygen amount determination unit 74, a mode determination unit 76, an injection pattern setting unit 77, and an injection timing setting unit 78.

  The injection range setting unit 72 sets a penetration target for each of the above fuel injections. In particular, in the low penetration injection described above, the injection range setting section 72 predicts the mode of the in-cylinder swirling flow formed by the cavity 5C and sets a penetration target (described later in detail based on FIG. 9).

  The operating state determining unit 73 determines the operating state of the engine body 1 based on the engine speed based on the value detected by the crank angle sensor SN1 and the engine load based on the opening information of the accelerator opening sensor SN10. This determination result is used depending on whether or not the operation mode is such that the low penetration injection is executed.

Residual oxygen amount determination unit 74 based on the detection value of the exhaust O ₂ sensor SN8, oxygen utilization in the combustion chamber 6, i.e. whether the remaining oxygen in the combustion chamber 6 is generated, the amount of oxygen addition is left Is determined. Incidentally, without depending on the detection value of the exhaust O ₂ sensor SN8, the intake air amount of the air flow sensor SN3 detects, by model calculations with reference to the fuel injection amount and the like of the injector 15, may be derived residual oxygen.

  The mode determination unit 76 determines the current operation mode based on the injection pressure set value data calculated based on the injection pressure of the injector 15 detected by the injection pressure sensor SN7 or according to the engine load. .

  The injection pattern setting unit 77 sets a pattern of fuel injection from the injector 15. In the low penetration injection described above, the injection pattern setting unit 77 sets the injection pattern of the low penetration injection according to the operation mode determined by the mode determination unit 76. The fluctuation factors of this injection pattern include rough execution timing of low penetration injection (for example, timing earlier than pilot injection or later timing than main injection), the number of low penetration injections (single-shot injection or split injection). Or).

  The injection timing setting unit 78 sets the injection timing of the fuel injection from the injector 15 according to various conditions.

[Why low penetration injection is required]
As described above, by adopting the two-stage structure cavity including the first and second cavity portions 51 and 52, the air in the combustion chamber 6, particularly the squish region on the radially outer side (in the present embodiment, the peripheral flat portion It is possible to expect an advantage that a uniform and thin air-fuel mixture can be formed by effectively using the air in the region above (55), an advantage of suppressing the generation of cooling loss through the inner peripheral wall of the cylinder 2, and the like. On the other hand, the present inventors have found that when a two-stage structure cavity is employed, the utilization rate of air in the radially central region of the combustion chamber 6 tends to decrease. This will be described with reference to FIG.

  FIG. 6A is a diagram schematically illustrating the in-cylinder swirling flow when the cavity according to the comparative example is employed. The piston 500 of the comparative example includes a cavity 500C having a single-stage structure. The cavity 500C includes a cavity portion 501, a cavity edge 502 serving as a radially outer opening edge of the cavity portion 501, and a peak portion 503 protruding from a central region in the radial direction B. The cavity portion 501 has a cross-sectional shape curved in an oval shape.

  In the combustion chamber 6A defined by the cavity 500C, it is assumed that fuel is injected from a not-shown injector along the injection axis AX toward the cavity edge 502. In this case, the in-cylinder flow of the air-fuel mixture containing the injected fuel becomes a swirling flow E1 indicated by an arrow in the figure. The swirling flow E1 hits the cavity edge 502, sequentially goes downward in the axial direction A and inward in the radial direction B along the shape of the cavity portion 501, is guided upward by the peak portion 503, and is directed outward in the radial direction B. Create a flow toward you. Such a swirling flow E1 is a relatively strong vortex, and the drawing force EP1 that draws the air AR existing in the radially central region of the combustion chamber 6A (near the upper part of the peak 503) outward in the radial direction B is also increased. . Therefore, an air-fuel mixture can be formed using the air AR in the radially central region.

  On the other hand, FIG. 6B is a diagram schematically showing the in-cylinder swirling flow when the piston 5 having the two-stage cavity 5C according to the present embodiment is employed. It is assumed that fuel is injected from the injector (not shown) along the injection axis AX toward the connecting portion 53 in the combustion chamber 6. In this case, the in-cylinder flow of the air-fuel mixture is branched at the connecting portion 53 and separated into a flow toward the lower first cavity 51 in the axial direction A and a flow toward the upper second cavity portion 52. Then, the lower swirling flow E2 and the upper swirling flow E3 are formed by the cavities 51 and 52, respectively. The lower swirling flow E2 is a flow similar to the swirling flow E1, and sequentially goes downward in the axial direction A and inward in the radial direction B along the shape of the first cavity portion 51 and upward by the peak portion 54. The flow is induced and directed outward in the radial direction B. The upper swirling flow E3 is a flow that flows from the outside in the radial direction B upward in the axial direction A, and then sequentially goes inward in the radial direction B. It can be seen that the formation of the upper swirling flow E3 makes it possible to utilize the air in the squish region as compared with the single-stage cavity 500C.

  However, the utilization rate of the air AR in the central area in the radial direction of the combustion chamber 6 tends to be inferior to that of the single-stage cavity 500C. That is, in the case of the cavity 5C having the two-stage structure, the swirl flow is separated into the lower swirl flow E2 and the upper swirl flow E3, so that the retraction force EP2 for drawing the air AR to the outside in the radial direction B is relatively weak. It becomes. That is, the lower swirling flow E2 contributing to the drawing in of the air AR is weaker than the swirling flow E1 of the comparative example due to the separation of the swirling flow, and the drawing force EP2 based on the swirling flow is weakened.

  FIG. 7A shows the state of generation of residual air in the combustion chamber 6A when the cavity 500C according to the comparative example is adopted, and FIG. 7B shows the combustion when the cavity 5C according to the present embodiment is adopted. It is sectional drawing which shows the generation | occurrence | production situation of the residual air in the chamber 6, respectively. As described with reference to FIG. 6A, in the comparative example, a swirling flow E1 of a relatively strong vortex is formed. Therefore, as shown in FIG. 7A, the air existing in the central area in the radial direction B of the combustion chamber 6A is easily drawn into the swirling flow E1, and the oxygen remaining area in which unused air (oxygen) can remain. G1 is a relatively narrow area.

  On the other hand, in the cavity 5C according to the present embodiment, as described with reference to FIG. 6B, since the lower swirling flow E2 is a relatively weak vortex, it exists in the radially central region of the combustion chamber 6. The flowing air is less likely to be drawn into the lower swirling flow E2. That is, it becomes difficult for the air to move outward in the radial direction B. For this reason, as shown in FIG. 7B, the oxygen remaining area G2 in which unused air (oxygen) can remain occupies a wide area in the radial center area. Therefore, there is a problem that oxygen remaining in the radially central region of the combustion chamber 6 cannot be effectively used.

[Utilization of residual air by low penetration injection]
In view of the above-described problem, in the present embodiment, in addition to the main injection and the pilot injection generally performed in the combustion control of the diesel engine, the low penetration injection for performing the fuel injection only in the radially central region of the combustion chamber 6 is performed. Is done. FIG. 8 is a cross-sectional view of the combustion chamber 6 showing the execution state of the low penetration injection 15A from the injector 15.

  The low penetration injection 15A is an injection for generating an air-fuel mixture by utilizing air remaining in the central region of the combustion chamber 6 in the radial direction B. For this reason, the spray penetration of the low penetration injection 15A is set to the outer edge H of the region where air (oxygen) can exist in the radial center region of the combustion chamber 6. That is, the arrival position of the tip of the fuel spray of the low penetration injection 15A is set to the outer edge H. The outer edge H corresponds to the outer edge of the oxygen remaining area G2 previously shown in FIG. The spray penetration of the low penetration injection 15A may be set inside the radial direction B with respect to the outer edge H. However, from the viewpoint of utilizing the oxygen in the oxygen remaining area G2 as much as possible, it is desirable to set the outer edge H to the spray penetration. If the spray penetration is set outside the outer edge H in the radial direction B, an excessively fuel-rich region may be generated outside the outer edge H in the radial direction B, so that it is desirable to avoid this.

  For the above reason, the injection range setting unit 72 (FIG. 5; the second injection control unit) sets the outer edge H to be the target line of the spray penetration when performing the low penetration injection 15A. Although the outer edge H cannot be detected by a sensor or the like, it must be estimated from the position where the swirling flow (the lower swirling flow E2 and the upper swirling flow E3) generated in the combustion chamber 6 reaches the inside in the radial direction B. Can be.

  FIGS. 9A to 9C are diagrams for explaining a method of setting the target line H1 of the low penetration injection 15A, which is the outer edge H of the oxygen remaining area G2. It can be said that the oxygen remaining area G2 in which unused air stays is generated in a region where the swirling flow of the lower swirling flow E2 and the upper swirling flow E3 does not occur or in a region where the swirling flow does not reach. Therefore, the target line H1 can be derived by obtaining the inner boundary line in the radial direction B where the swirling flow reaches. That is, the position where the outermost peripheral portions of the swirling flows E2 and E3 are closest to the center of the combustion chamber 6 in the radial direction B is the above-described boundary line, that is, the target line H1.

  The size of the swirl flow of the lower swirl flow E2 and the upper swirl flow E3 generated in the combustion chamber 6 having the two-stage structure cavity 5C is the spray penetration of the injection having the maximum energy per cycle, that is, the main injection. It is determined by factors such as the distribution of the spray penetration to the upper and lower cavities 51 and 52, the shape (turning curvature) and the volume (turning distance) of the cavities 51 and 52.

  As shown in FIG. 9A, the swirling flows E2 and E3 are swirling flows having a swirling diameter in the radial direction B that fluctuates according to the above-described factors. Since the shape and volume of the cavity 5C are fixed, the fluctuation factors of the turning diameter are spray penetration and its distribution. The position where the outermost peripheral portions of the swirling flows E2 and E3 are closest to the center in the radial direction B of the combustion chamber 6 is the above-described boundary line, that is, the target line H1. In the present embodiment, the target line H1 is determined solely by the swirl diameter of the lower swirl flow E2 generated in the first cavity portion 51 disposed radially inside the second cavity portion 52.

  The spray penetration of the main injection is determined by the injection pressure and the injection amount of the fuel from the injector 15 as shown in FIG. That is, as the integrated value of the injection pressure and the injection amount increases, the spray penetration also increases, which means that the swirl diameter (swirl energy) of the swirl flow also increases. On the other hand, the distribution of the spray penetration to the upper and lower cavities 51 and 52 depends on the positional relationship between the injection axis AX and the cavities 51 and 52, that is, the injection timing.

  FIG. 9C is a graph showing a relationship between the injection timing and the spray penetration in the lower first cavity portion 51. Since the main injection is generally performed after the compression top dead center, the piston 5 descends toward the retard side. Therefore, the more the injection timing is retarded, the more the injection axis AX is directed toward the upper side of the connecting portion 53, that is, toward the second cavity portion 52 side. That is, the more the injection timing is retarded, the smaller the spray penetration distributed to the first cavity portion 51, and accordingly, the smaller the swirl diameter (swirl energy) of the lower swirl flow E2.

  As described above, the turning diameter of the lower swirling flow E2 can be estimated from the injection pressure, the injection amount, and the injection timing of the main injection. The injection range setting unit 72 (FIG. 5) determines the size of the oxygen remaining area G2 (FIG. 7B) generated in the radial center region of the combustion chamber 6 based on the estimated swirling diameter of the lower swirling flow E2. Is estimated. Then, the injection range setting unit 72 sets the outer edge H (FIG. 8) of the oxygen remaining area G2 to the target line H1 in the low penetration injection. Then, the fuel injection control unit 71 executes the low penetration injection with the target line H1 as the penetration target at an appropriate timing, so that the air remaining in the oxygen remaining area G2 and the spray fuel by the low penetration injection can be used. An air-fuel mixture can be formed. As a result, a uniform and thin air-fuel mixture is formed by effectively utilizing the air in the combustion chamber 6, and high-quality diesel combustion in which generation of soot and the like is suppressed can be realized.

[First Embodiment]
Next, a first embodiment of low penetration injection control will be described. In the first embodiment, the low-penetration injection described above is defined as “timing earlier than pilot injection” (hereinafter, referred to as “PILOT region”) or “timing later than main injection” (hereinafter, referred to as “AFTER region”). The following is a simple example of selecting which of the above is executed according to the outside air temperature.

  FIGS. 10A to 10D are time charts showing a mode of low penetration injection according to the first embodiment. Here, the injection timing (crank angle CA) of fuel injection performed per cycle and the injection amount are schematically shown. The injection pattern setting unit 77 of the fuel injection control unit 71 sets at least an injection pattern as shown in FIGS. 10A to 10D and causes the injector 15 to execute the fuel injection.

  FIG. 10A shows a basic injection pattern when low penetration injection is not performed. Here, an example in which the main injection P1, the pilot injection P2, and the after injection P3 are executed as the basic injection pattern is shown. The main injection P1 is an injection having the maximum energy (injection amount), and is an injection executed near the compression top dead center (for example, 2 to 6 deg_ATDC). The pilot injection P2 is an injection that is executed at a timing earlier than the main injection P1 (for example, 1 to 10 deg_BTDC), and is executed for the purpose of creating an air-fuel mixture in advance to enhance ignitability. FIG. 10A shows an example in which the pilot injection P2 is executed in two stages, that is, the first pilot injection P21 and the second pilot injection P22. The after-injection P3 is an injection that is executed at a timing later than the main injection P1 (for example, 8 to 15 deg_BTDC), and is executed for the purpose of completely burning the fuel so as not to generate soot. Note that these injections P1, P2, and P3 are injections in which the spray penetration is not limited to the central region within the target line H1, as in the low penetration injection described above.

  FIG. 10B shows an injection pattern in which low penetration injection P4 is executed in the PILOT region on the more advanced side than pilot injection P2. In general, the injection amount of the low penetration injection P4 is smaller than the injections P1, P2, and P3 of the basic injection pattern because the spray penetration is limited to the target line H1.

  FIG. 10C illustrates an injection pattern in which the low penetration injection P5 is executed in the AFTER region that is more retarded than the after injection P3. The injection amount of the low penetration injection P5 performed in the AFTER region is also smaller than the injections P1, P2, and P3 of the basic injection pattern.

  In the present embodiment, the injection pattern of FIG. 10B and the injection pattern of FIG. 10C are changed by the injection pattern setting unit 77 according to the outside air temperature.

  First, the injection pattern in FIG. 10 (B) indicates that the outside air temperature is lower than the preset reference temperature, and it is determined that the mixture is difficult to ignite in the combustion chamber 6 (low ignitability). Adopted. In the present embodiment, the injection pattern setting unit 77 determines whether or not the outside air temperature is lower than the reference temperature. That is, when the outside air temperature is low, the temperature of the intake air (air) introduced into the combustion chamber 6 is low, and the ignitability of the air-fuel mixture in the combustion chamber 6 is low. Under such a low ignitability condition, fuel and air are injected into the oxygen remaining area G2 (FIG. 7B) at the center in the radial direction of the combustion chamber 6 earlier in the PILOT area. Can be promoted, and the ignitability of the region can be enhanced. Therefore, the air in the oxygen remaining area G2 can be effectively burned and used.

  Conversely, if the low air-fuel injection P4 in the PILOT region is performed under the condition (high ignitability) that the air-fuel mixture is easy to ignite when the outside air temperature is equal to or higher than the reference temperature, the fuel related to the injection P4 Because the reaction with air is excessively promoted, the mixture of fuel and air, and the mixture of fuel and air related to the subsequent pilot injection or main injection start combustion earlier than desired. This may cause so-called premature ignition. Therefore, when the outside air temperature is equal to or higher than the reference temperature and the ignitability is determined to be high, the low penetration injection P4 in the PILOT region is avoided.

  On the other hand, the injection pattern shown in FIG. 10C is employed when it is determined that the outside air temperature is equal to or higher than the reference temperature and the air-fuel mixture is ignited easily in the combustion chamber 6 (high ignitability). . In the case of such a high ignitability condition, ignitability does not matter, but the use of the PILOT region causes the problem of premature ignition described above. Therefore, the injection pattern of FIG. 10C is adopted, and the AFTER region is utilized.

  FIG. 10D shows an injection pattern in which the low penetration injections P41 and P42 are divided into two and executed in the PILOT region. That is, in the present embodiment, the injector 15 can execute the low penetration injection in a plurality of times. As shown in FIG. 9B, the spray penetration is determined by the injection pressure and the injection amount (when the injection pressure is high and when the injection amount is large, the spray penetration becomes large). Here, the injection pressure is generally set according to the operating state of the engine body 1 (engine load and rotation speed). Therefore, when the set injection pressure is high, when the injection amount of the low penetration injection is set such that the spray penetration of the low penetration injection becomes the target line H1, the fuel supplied in one low penetration injection is The amount may be so low that the amount of air in the oxygen remaining area G2 may not be sufficiently used. Specifically, in the present embodiment, the injection pressure is kept constant during at least one combustion cycle. Therefore, the injection pressures of the low penetration injection, the pilot injection, the main injection, and the after injection, which are performed in at least the same combustion cycle, are all substantially the same. Then, as the injection pressure, a pressure suitable as the injection pressure of the main injection is adopted according to the operating state of the engine main body 1 (engine load and rotation speed). Therefore, as described above, since the set injection pressure is high, it is necessary to reduce the injection amount of one low penetration injection, and accordingly, there is a case where the total injection amount of the low penetration injection cannot be sufficiently secured. Can occur. Therefore, in such a case, a required injection amount can be secured by executing the low penetration injections P41 and P42 in a plurality of times.

  FIG. 11 is a flowchart illustrating the low penetration injection control according to the first embodiment. The fuel injection control unit 71 (FIG. 5) of the processor 70 acquires information on the traveling area of the vehicle (the operating state of the engine body 1) and the outside air temperature from each of the sensors SN <b> 1 to SN <b> 12 shown in FIG. 5 and other sensors. (Step S1).

  Subsequently, the operating state determination unit 73 determines that the engine rotational speed detected by the crank angle sensor SN1 and the engine load detected by the accelerator opening sensor SN10 fall within a predetermined traveling range (operating state). It is determined whether or not to perform (step S2). The predetermined traveling region is a traveling region in which the oxygen remaining area G2 shown in FIG. 7B is formed. The region not included in the predetermined traveling region is exemplified by, for example, a case where the spray penetration of the main injection P1 or the pilot injection P2 is larger than a predetermined set amount. The predetermined set amount is a spray penetration that produces an injection amount such that air cannot remain in a radially central region of the combustion chamber 6, and a region not included in the predetermined traveling region generally has a high load and a high rotational speed. The traveling area of the speed corresponds.

  When it does not correspond to the predetermined traveling region (NO in step S2), that is, when the oxygen remaining area G2 is not formed, the operating state determination unit 73 determines that the operation mode is not the operation mode for executing the low penetration injection. In this case, the fuel injection control unit 71 prohibits the low penetration injection (step S3). This is because if the low penetration injection is performed in such a traveling region, the air-fuel mixture becomes rich, and the combustibility and the fuel consumption performance deteriorate.

On the other hand, if it corresponds to the predetermined traveling region (YES in step S2), a state in which the oxygen remaining area G2 is formed in the radially central area of the combustion chamber 6 is established. In this case, the remaining oxygen amount determination unit 74 determines whether or not the amount of oxygen equal to or more than the predetermined value remains in the oxygen remaining area G2 (step S4). This judgment, as described above, is performed based on the detected value or the model calculations of the exhaust O ₂ sensor SN8. When the amount of oxygen equal to or more than the predetermined value does not remain in the oxygen remaining area G2 (NO in step S4), since there is no oxygen to be used by executing low penetration injection in the first place, the fuel injection control unit 71 Penetration injection is prohibited (step S3).

  On the other hand, when the remaining oxygen amount determination unit 74 determines that the oxygen amount equal to or more than the predetermined value remains in the radial center region (YES in step S4), the mode is a mode in which low penetration injection is executed. In this case, next, the injection pattern setting unit 77 determines whether or not the outside air temperature is equal to or higher than the reference temperature (step S5).

  If it is determined in step S5 that the outside air temperature is equal to or higher than the reference temperature (YES in step S5), the injection pattern setting unit 77 sets an injection pattern for executing low penetration injection in the AFTER region (step S6). For example, the injection pattern including the low penetration injection P5 shown in FIG. 10C is set. On the other hand, if it is determined in step S5 that the outside air temperature is lower than the reference temperature (NO in step S5), the injection pattern setting unit 77 sets an injection pattern for executing low penetration injection in the PILOT region (step S7). For example, the injection pattern including the low penetration injection P4 or the injection pattern including the divided low penetration injections P41 and P42 shown in FIG. 10B is set.

[Second embodiment]
Next, a second embodiment of low penetration injection control will be described. In the second embodiment, an example will be described in which the operation mode is determined according to the injection pressure of the injector 15 determined according to the operation state, and the injection pattern of the low penetration injection is determined according to each operation mode and ignitability.

<Explanation of basic control categories>
FIG. 12 is a diagram showing basic control divisions in low penetration injection control according to the second embodiment. In FIG. 12, the horizontal axis represents the fuel injection pressure from the injector 15, that is, the injection pressure of the injector 15, and indicates the set maximum injection pressure FPmax and the set minimum injection pressure FPmin. The vertical axis indicates the fuel amount injected from the injector 15 by the low penetration injection. The oblique line H2 in the figure is a line connecting the injection pressure and the injection amount when the spray penetration (the tip position of the spray) of the low penetration injection becomes the target line H1 (FIG. 9), that is, the spray penetration of the low penetration injection. Is a basic control target line for the injection pressure and the injection amount for setting the target line H1. The vertical axis in FIG. 12 represents the amount of fuel injected from the injector 15 by one low penetration injection. Hereinafter, the amount of fuel injected from the injector 15 by this one low penetration injection is referred to as a single-shot low penetration injection amount, as appropriate.

  As described above, the spray penetration increases as the injection pressure increases, and the spray penetration increases as the injection amount increases. Accordingly, the control target line H1 is a line in which the higher the injection pressure is, the smaller the single-shot low penetration injection amount is.

  In the present embodiment, as described above, the injection pressure is set according to the operating state of the engine body 1. Thus, the injection amount is adjusted according to the set injection pressure in order to make the low penetration injection spray fly to the target line H1. That is, in the low penetration injection control of the present embodiment, the injection penetration of the target line H1 is achieved by receiving the injection pressure data as an existing value and setting the injection quantity according to the injection pressure. The control target line H2 represents such an injection amount setting line.

  Generally, in a region where the injection pressure is relatively high, low penetration injection is performed utilizing the PILOT region, and in a region where the injection pressure is relatively low, low penetration injection is performed utilizing the AFTER region. The reason for this roughly division is as follows.

  First, it is more advantageous to utilize the PILOT region in terms of fuel efficiency. Since the injection in the AFTER region is performed after the combustion of the main injection, heat is generated mainly while the piston is descending, and the fuel consumption loss increases. On the other hand, the fuel injected in the PILOT region is burned with high thermal efficiency near the compression top dead center, so that much of the combustion energy can be extracted as effective torque. Therefore, it is desirable to utilize the PILOT region as much as possible in order to improve fuel efficiency.

  However, as shown in the control target line H2, when the injection pressure is low, it is necessary to increase the injection amount so that the tip of the spray reaches the target line H1. If a large amount of fuel is supplied to the combustion chamber 6 in the PILOT region, a problem of premature ignition occurs. Specifically, when a large amount of fuel is supplied to the combustion chamber 6 by low penetration injection in the PILOT region, there is a possibility that this fuel will start combustion before the start of combustion of fuel related to pilot injection or main injection, or that low fuel injection will occur. The reaction between the fuel and the fuel related to the pilot injection or the main injection may be accelerated by the reaction between the fuel and the air, and the fuel related to the injection may start burning earlier than a desired timing. On the other hand, when the low penetration injection is performed in the AFTER region, the fuel related to the low penetration injection burns after the fuel related to the pilot injection or the main injection is burned, so that the problem of premature ignition does not occur.

  Accordingly, in the present embodiment, basically, when the injection pressure is low and the amount of fuel supplied to the combustion chamber 6 by the low penetration injection is large, the AFTER region is used to supply the fuel to the combustion chamber 6 by the low penetration injection. When the amount of fuel to be used is small, the PILOT region is used.

  Here, there is a characteristic of a diesel engine that the lower the injection pressure, the larger the particle size of the spray particles and the more easily soot is generated. Therefore, if the fuel is injected in the AFTER region when the injection pressure is low as described above, the effect that the soot can be reburned can be obtained.

  As described above, the PILOT region is generally used in the high injection pressure region, and the AFTER region is used in the low injection pressure region.

  Next, a further division of the PILOT area and the AFTER area will be described. As shown in FIG. 12, the PILOT region includes the first region on the high injection pressure side where the injection is performed in a divided manner, as illustrated in FIG. 10D, and the PILOT region, as illustrated in FIG. , And a second region on the low injection pressure side where injection is performed in a single shot. The AFTER region is also divided into a third region on the high injection pressure side where the injection is performed in a divided manner and a fourth region on the low injection pressure side where the injection is performed in a single shot.

  In the division between the single injection and the split injection, in the injection along the control target line H2, the injection amount necessary to burn all the oxygen in the oxygen remaining area G2 generated in the radially central area of the combustion chamber 6 can be secured. Or not. In the region where the injection pressure is high (the first region and the third region), the injection amount per injection (single-shot low penetration injection amount) is small (if it is large, the injection will exceed the target line H1). Therefore, two or more injections are performed to secure the required injection amount. On the other hand, in the region where the injection pressure is low, the injection amount per injection (single-shot low penetration injection amount) is relatively large, so that the required injection amount can be ensured by one injection.

  The first area is a “PILOT split” area where the low penetration injection is executed by dividing into a plurality of times in the PILOT area, and the second area is a “PILOT single shot” where the low penetration injection is executed once in the PILOT area. Area. Further, the third area is an “AFTER split” area where the low penetration injection is executed a plurality of times in the AFTER area, and the fourth area is the “AFTER single shot” where the single low injection is executed in the AFTER area. Area. FIG. 12 shows first, second, third, fourth, and fifth lines L1, L2, L3, L4, and L5 indicating the upper or lower limit injection amounts of these sections. The fuel injection amount has a relationship of L1 <L2 <L3 <L4 <L5.

  The third line L3 is the upper limit of the injection amount of the low penetration injection when utilizing the PILOT region, and the first region and the second region are set at least in the region where the single-shot low penetration injection amount is equal to or less than the third line L3. Have been. As described above, when a large amount of fuel is supplied into the combustion chamber 6 by low penetration injection in the PIROT region, premature ignition occurs. The third line L3 is an upper limit line of the injection amount at which premature ignition does not occur when low penetration injection is performed in the PILOT region.

  Here, the third line L3 is an upper limit line of the total amount of fuel supplied into the combustion chamber 6 per combustion cycle by low penetration injection. Therefore, when the low penetration injection is performed a plurality of times in the PILOT region, it is necessary that the total amount of fuel related to each injection does not exceed the third line L3.

  Note that the third line L3 is consequently the lower limit of the AFTER split injection in the third area, but this is not the lower limit in the functional sense of the AFTER split injection. As described above, the utilization of the PILOT region is advantageous in view of fuel consumption loss. Therefore, the PILOT region is preferentially applied, and the injection amount region that cannot be covered by the PILOT region due to the problem of premature ignition is supplemented by the AFTER region. This is the lower limit from the viewpoint of.

  The second line L2 is a lower limit line that secures an injection amount that does not cause an ignition delay in the oxygen remaining area G2 in the PILOT single injection in the second area. When the injection amount per injection (single-shot low penetration injection amount) becomes equal to or less than the second line L2, a single injection cannot secure a sufficient amount of fuel for the air existing in the oxygen remaining area G2, No combustion occurs in the remaining area G2, or the combustion start timing is delayed. In other words, the second line L2 is a line that is set from the viewpoint that a minimum amount of heat that can appropriately cause combustion using the oxygen in the region G2 is provided by one low penetration injection.

  Accordingly, the second region in which the PILOT single injection is performed is a region between the second line L2 and the third line L3 on the control target line H2.

  The first region where the PILOT split injection is performed is a region below the second line L2 on the control target line H2. That is, as described above, if the injection amount per injection is equal to or less than the second line L2, the required injection amount cannot be secured by one low penetration injection, and the divided injection is required. In L2 and below, low penetration injection is performed in a plurality of times.

  In the present embodiment, in the first region, the low penetration injection is performed twice. The level (injection amount) of the second line L2 is set to be equal to or less than half of the level (injection amount) of the third line L3. Even if low penetration injection is performed twice in the first region, the total Is suppressed to an amount equal to or less than the third line L3.

  The first line L1 with the smallest injection amount is a lower limit line that secures an injection amount that does not cause an ignition delay in the oxygen remaining area G2 in the PILOT split injection in the first area. If the injection amount per injection is further reduced, the required injection amount cannot be ensured even by the split injection, and as a result, no combustion occurs in the oxygen remaining area G2, or the combustion start timing is delayed. That is, the first line L1 is a line set from the viewpoint of providing a minimum amount of heat capable of causing combustion using the oxygen in the region G2. The first line L1 is also an injection amount at which the control target line H2 intersects with the set maximum injection pressure FPmax, and is actually a line from which the injection amount cannot be reduced any more.

  The fourth line L4 is a lower limit line that secures an injection amount for exhibiting a function of oxidizing soot in AFTER single injection in the fourth region. If the injection amount per injection is smaller than that of the fourth line L4, the injection amount for sufficiently oxidizing the soot cannot be secured by the single injection, and the split injection is required (third region). On the other hand, the fifth line L5 is an upper limit line for limiting the injection amount in the AFTER single injection in the fourth area so that the oxygen remaining area G2 is not excessively rich. When the injection amount per injection is larger than that in the fifth line L5, heat more than the amount of oxygen existing in the oxygen remaining area G2 is given, and soot can be newly generated.

  As described above, in the low penetration injection, the injection pattern is properly used according to the division of the first to fourth regions. However, these sections (first to fifth lines L1 to L5) and the injection timing are not fixed, and are corrected (set) according to the driving situation. The influences on the division and the injection timing are mainly the ignitability of the air-fuel mixture in the combustion chamber 6 and the appearance of soot.

  The ignitability and soot development vary depending on the outside air temperature. Specifically, when the outside air temperature is high, the ignitability of the air-fuel mixture becomes high. In addition, when the outside air temperature increases, soot is generated because the density of intake air (air supplied to the combustion chamber) is low and the charging efficiency is low (the weight of oxygen introduced into the combustion chamber 6 is easily reduced). Easier to do. Thus, in the present embodiment, the injection pattern and injection timing of the low penetration injection are set according to the outside air temperature.

  The ignitability affects the setting of the second line L2 and the third line L3 shown in FIG.

  When the outside temperature is high and the ignitability is high, the ignitability can be ensured even with a smaller injection amount. Therefore, when the outside air temperature is high and the ignitability is high, the second line L2 set from the viewpoint of preventing ignition delay can be set to a lower injection level. That is, the lower limit of the second region can be enlarged. On the other hand, since the third line L3 tends to cause premature ignition, it is necessary to set a lower injection amount level when the outside temperature is high and the ignition is high. That is, when the outside air temperature is high and the ignitability is high, it is necessary to expand the lower limit of the third region and expand the utilization range of the AFTER region.

  Regarding the injection timing, when utilizing the PILOT region, from the viewpoint of suppressing premature ignition, when the outside air temperature is high and the ignition is high, the injection timing of the low penetration injection should be set to a retarded tendency. Is desirable. In other words, if the injection timing is early, the mixing time of the fuel-air mixture becomes longer and the mixing is promoted, and ignition becomes easier earlier. Therefore, in order to delay the ignition (to avoid premature ignition, ), It is desirable to set the injection timing to the retard side.

  On the other hand, when the outside air temperature is low and low ignitability, it is desirable to set the second line L2 to a higher injection amount level in order to ensure ignitability. On the other hand, in the case of the third line L3, if the outside air temperature is low and the ignition performance is low, premature ignition tends to be difficult to occur, so that a higher injection amount level can be set. That is, when the outside air temperature is low and the ignition performance is low, the utilization range of the PILOT region (second region) that is advantageous in terms of fuel consumption loss can be expanded.

  Also, regarding the injection timing, when utilizing the PILOT region, in order to improve the ignitability by increasing the degree of mixing of fuel and air by the low penetration injection, if the outside air temperature is low and the ignitability is low, the low penetration It is desirable to set the injection timing of the injection to an advanced angle tendency.

  The change in the expression of soot with the change in the outside air temperature affects the setting of the fourth line L4 shown in FIG.

  When the outside air temperature is high and soot is likely to be generated, the fourth line L4 is set to a higher injection amount level to promote soot oxidation, and low penetration injection is performed even at a higher injection amount. It is desirable to perform it several times.

  In the case where the outside air temperature is high and soot is easily generated when the AFTER region is used, the low penetration is set so that the thermal energy generated by the low penetration injection is effectively used for the oxidation of the generated soot. It is desirable to set the injection timing of the injection to a retarded tendency.

  On the other hand, when the outside air temperature is low and soot is hardly generated, the fourth line L4 is injected at a lower level in order to prevent fuel consumption performance from being deteriorated due to a large amount of fuel being injected after the main injection. It is desirable to set the amount level to reduce the total amount of fuel supplied to the combustion chamber 6 by the low penetration injection.

  In addition, when utilizing the AFTER region, when the outside air temperature is low and soot is not easily generated, it is desirable to set the injection timing of the low penetration injection to an advanced angle in order to prevent deterioration of fuel efficiency.

<Setting of injection pattern based on outside temperature>
(Specific example of injection pattern)
FIGS. 13 (A) to 13 (E) and FIGS. 14 (A) to 14 (D) are time charts schematically showing nine injection modes of low penetration injection adopted in the second embodiment. Here, similarly to FIG. 10A, an example is shown in which the main injection P1, the pilot injection P2 (first and second pilot injections P21 and P22), and the after injection P3 are executed as the basic injection patterns. I have. In addition to these injections P1 to P3, low penetration injection is executed.

  FIG. 13A shows an ejection pattern called “PILOT division-A”, which is a pattern adopted as a basic ejection pattern of the first region in FIG. In the PILOT division-A, the low penetration injection P4 is executed in the PILOT region preceding the injections P1 to P3 of the basic injection pattern. The low penetration injection P4 includes a first injection P41 executed at a predetermined crank angle CA11, and a second injection P42 executed on the retard side at a predetermined interval t11 from the first injection P41. The injection amount of the first injection P41 and the second injection P42 is set to the injection amount Fa along the control target line H2.

  FIG. 13B shows an injection pattern referred to as “PILOT division-B”, in which the low penetration injection P4 is executed at a more advanced timing than PILOT division-A. The low penetration injection P4 of the PILOT split-B is the same split injection as the PILOT split-A, but is executed at the crank angle CA12 in which the first injection P41 is more advanced than the crank angle CA11. Then, the second injection P42 is executed on the retard side with an interval t12 shorter than the interval t11. By advancing the injection timing of the first injection P41, time from injection to ignition can be gained, and ignitability can be improved. Further, by setting the interval between the first and second injections P41 and P42 to be a short interval t12, a rich zone is formed in which the injected fuel of the first injection P41 and the injected fuel of the second injection P42 are superimposed. The ignitability can be improved.

  FIG. 13C shows an ejection pattern called “PILOT single shot-A”, which is a pattern adopted as a basic ejection pattern of the second region. In the PILOT single shot-A, in the PILOT region, a low penetration injection P4 consisting of a single shot is executed at a predetermined crank angle CA2. The injection amount of the low penetration injection P4 is set to the injection amount Fb along the control target line H2. That is, the injection amount Fb is an amount larger than the injection amount Fa per single split injection. The “PILOT single shot-A” means that the injection timing (CA2) of the low penetration injection P4 is equal to the injection timing of the low penetration injection P4 of the PILOT split-A (FIG. 13A) (the injection timing of the first injection P41, This pattern is set on the more retarded side than CA11).

  FIG. 13D shows an injection pattern called “PILOT single shot-B”, in which the single low penetration injection P4 is executed at a timing delayed by ΔCA1 from PILOT single shot-A. Premature ignition can be suppressed by retarding ΔCA1.

  On the other hand, FIG. 13E shows an injection pattern called “PILOT single shot-C”, in which the single low-penetration injection P4 is executed at a timing advanced by ΔCA2 from PILOT single shot-A. It is. By the advance of ΔCA2, the ignitability can be improved as described in PILOT division-B.

  FIG. 14A shows an ejection pattern called “AFTER division-A”, which is a pattern adopted as a basic ejection pattern of the third region. In AFTER division-A, low penetration injection P5 is executed in the AFTER region after execution of injections P1 to P3 of the basic injection pattern. The low penetration injection P5 includes a first injection P51 executed at a predetermined crank angle CA31, and a second injection P52 executed on the retard side at a predetermined interval t21 from the first injection P51. The injection amount of the first injection P51 and the second injection P52 is set to the injection amount Fc along the control target line H2.

  FIG. 14B is an injection pattern called “AFTER division-B”, in which the low penetration injection P5 is executed at a timing more retarded than AFTER division-A. The low penetration injection P5 of AFTER split-B is the same split injection as AFTER split-A, but the first injection P51 is executed at a crank angle CA32 that is more retarded than the crank angle CA31. Then, the second injection P52 is executed on the retard side after an interval t22 longer than the interval t21. By delaying the injection timing of the first injection P51, it becomes advantageous for soot oxidation and combustion, and the generation of soot can be further suppressed. In addition, making the interval between the first and second injections P51 and P52 a long interval t22 also contributes to the suppression of soot.

  FIG. 14C shows an ejection pattern called “AFTER single shot-A”, which is a pattern adopted as a basic ejection pattern in the fourth region. In AFTER single shot-A, in the AFTER region, low penetration injection P5 consisting of single shot is executed at a predetermined crank angle CA4. The injection amount of the low penetration injection P5 is set to the injection amount Fd along the control target line H2. That is, the injection amount Fd is an amount larger than the injection amount Fc per single split injection. In the “AFTER single shot-A”, the injection timing (CA4) of the low penetration injection P5 is the injection timing of the low penetration injection P5 (FIG. 14B) of the “AFTER division-B” (the first injection P51). This is a pattern set on the advance side of the injection timing CA32).

  FIG. 14D shows an injection pattern called “AFTER single shot-B”, in which the single low penetration injection P5 is executed at a timing advanced by ΔCA3 from AFTER single shot-A. Fuel consumption loss can be improved by the advance of ΔCA3. “AFTER single shot-B” is a pattern in which the injection timing of the low penetration injection P5 is set to be more advanced than the injection timing of the first injection P51 of AFTER division-A (FIG. 14A). . In other words, the injection pattern of “AFTER single shot-B” is a pattern in which the injection timing of the low penetration injection is set to the advanced side than any of the injection patterns in which the low penetration injection is performed in the AFTER region.

(Selection of injection pattern)
The use of the nine injection patterns described above will be described next.

  In the following, the injection pressure and the single-shot low penetration injection amount are the injection pressure and the injection amount using the PILOT division-A pattern in FIG. 13A in a state where the outside air temperature is within a preset basic temperature range. The case is the first region mode, the case where the outside air temperature is within the basic temperature range, the injection pressure and the injection amount using the PILOT single shot-A pattern of FIG. In the third area mode, the case where the injection pressure and the injection amount use the AFTER division-A pattern of FIG. 14A in the state where the outside air temperature is within the basic temperature range is shown in FIG. The case where the AFTER single shot-A pattern of (C) is the injection pressure and injection amount used is referred to as a fourth region mode.

  The above-mentioned basic temperature range is a range in which the outside air temperature is not too high or too low, and is a range from a temperature lower than the predetermined basic temperature by a predetermined temperature to a temperature higher than the basic temperature by a predetermined temperature. is there. The basic temperature range (the upper limit and the lower limit of the basic temperature range) is set in advance and stored in the mode determination unit 76.

  The mode determination unit 76 sets the control target line H2 (the relationship between the target injection pressure and the injection amount) based on the target line H1 set as described above by the injection range setting unit 72. Further, the mode determination unit 76 calculates an injection pressure at a point where the control target line H2 intersects with the second line L2 to the fourth line L4 when the outside air temperature is in the basic temperature range. That is, on the control target line H2, the injection pressure at which the injection amount reaches the level of the second line L2 to the fourth line L4 when the outside air temperature is in the basic temperature range is calculated. The levels of these lines L2 to L4 when the outside air temperature is in the basic temperature range are set in advance and stored in the mode determination unit 76. The mode determination unit 76 compares the separately set injection pressure with the injection pressure corresponding to the lines L2 to L4 when the outside air temperature is in the basic temperature range, and determines that the set injection pressure is the control target line. When the injection pressure at the point where H2 and the second line L2 intersect is equal to or higher than the injection pressure (hereinafter, referred to as the second line injection pressure), it is determined that the first region mode is set, and the control target line H2 intersects with the third line L3. If the injection pressure is equal to or higher than the injection pressure at the point (hereinafter, referred to as a third line injection pressure) and the set injection pressure is lower than the second line injection pressure, it is determined that the mode is the second region mode. When the set injection pressure is equal to or higher than the injection pressure at the point where the control target line H2 and the fourth line L4 intersect (hereinafter, referred to as a fourth line injection pressure) and lower than the third line injection pressure, the third region mode is set. When the set injection pressure is less than the fourth line injection pressure, it is determined that the fourth region mode is set.

(1) First Area Mode In the first area mode, as described above, when the outside air temperature is within the basic temperature range, the PILOT division-A pattern of FIG. 13A is used.

  On the other hand, when the outside air temperature is higher than the basic temperature range (upper limit temperature of the basic temperature range), that is, under the condition of high ignitability, the PILOT single shot-B pattern in FIG. 13D is used. This is because, as described above, as the ignitability improves, the injection amount that defines the second line L2 decreases. Here, as described above, the injection timing of the low penetration injection P4 of “PILOT single shot-B” is more retarded than the injection timing of the low penetration injection P4 of PILOT split-A, and in the first region mode, When the outside air temperature is higher than the basic temperature range, the injection timing of the low penetration injection P4 is delayed more than when the outside air temperature is within the basic temperature range.

  On the other hand, when the outside air temperature is lower than the basic temperature range (lower limit temperature of the basic temperature range), that is, under the condition of low ignition performance, the PILOT division-B pattern in FIG. 13B is used. That is, the injection timing of the first injection P41 is advanced more than when the outside air temperature is in the basic temperature range. Further, the interval between the first and second injections P41 and P42 is shortened, and the injection timing of the second injection P41 is advanced more than when the outside air temperature is in the basic temperature range. This is because, as described above, when the ignitability is low, it is necessary to improve the ignitability.

(2) Second region mode In the second region mode, as described above, when the outside air temperature is within the basic temperature range, the PILOT single-A pattern of FIG. 13C is used.

  On the other hand, when the outside air temperature is higher than the basic temperature range, that is, under the condition of high ignitability, the pattern of AFTER division-B in FIG. 14B is used. That is, when the outside air temperature is higher than the basic temperature range, the injection timing of the low penetration injection is delayed from a timing before the pilot injection P2 to a timing after the after injection P3. This is because it is necessary to reduce the injection amount defining the third line L3 (using the AFTER region) in order to avoid premature ignition under the condition of high ignitability as described above. It depends. In addition, an environment in which soot is likely to be generated as the outside air temperature is high. In contrast, the adoption of AFTER division-B in which the low penetration injection (the first and second injections P51 and P52) is performed at a relatively late timing can suppress soot generation.

  On the other hand, when the outside air temperature is lower than the basic temperature range, that is, when the ignitability is low, the pattern of PILOT division-B in FIG. 13B is used. This is because, as described above, as the ignitability deteriorates, the injection amount that defines the second line L2 increases. Here, as described above, the injection timing CA2 of the low penetration injection P4 in the PILOT single shot-A pattern is more retarded than the injection timing CA11 of the low penetration injection (first injection P41) in the PILOT split-A pattern. The injection timing CA12 of the low penetration injection (first injection P41) of the PILOT division-B pattern is further advanced than the injection timing CA11. Thus, when the outside air temperature is lower than the basic temperature range, the injection timing of the low penetration injection is advanced compared to when the outside air temperature is within the basic temperature range. Due to the advance of the injection timing and the low penetration injection being divided and executed, the mixing of fuel and air is promoted, and the ignitability is improved.

(3) Third Region Mode In the third region mode, as described above, when the outside air temperature is within the basic temperature range, the pattern of the AFTER division-A of FIG. 14A is basically used. .

  On the other hand, when the outside air temperature is higher than the basic temperature range, that is, when soot is easily generated, the pattern of AFTER division-B in FIG. 14B is used. That is, the injection timing of the first injection P51 of the low penetration injection is delayed more than when the outside air temperature is within the basic temperature range. Further, the interval between the first and second injections P51 and P52 is lengthened, and the injection timing of the second injection P51 is delayed more than when the outside air temperature is within the basic temperature range. This is because, as described above, when the outside air temperature is low and soot is likely to be generated, the fuel supplied by low penetration injection more effectively contributes to soot oxidation and combustion.

  On the other hand, when the outside air temperature is lower than the basic temperature range, that is, when the condition in which soot is unlikely to be generated, and when the condition of low ignition performance is used, the PILOT single-shot pattern of FIG. 13E is used. That is, the injection timing of the low penetration injection is advanced from a timing that is more retarded than the after injection P3 to a timing that is more advanced than the pilot injection P2. This is because an environment in which premature ignition is unlikely to occur due to low ignitability can be achieved, and the injection amount that defines the third line L3 can be increased, so that the PILOT region where fuel consumption loss is small can be utilized. Further, the fact that the ignitability can be improved by executing the advanced low penetration injection P4 is also the reason for employing PILOT single shot-C.

(4) Fourth Region Mode In the fourth region mode, as described above, when the outside air temperature is within the basic temperature range, the AFTER single-A pattern of FIG. 14C is used.

  On the other hand, when the outside air temperature is higher than the basic temperature range, that is, when soot is easily generated, the pattern of AFTER division-B in FIG. 14B is used. This is because it is necessary to increase the injection amount that defines the fourth line L4. The injection timing of the low penetration injection (first injection P51, second injection P51) of the AFTER division-B pattern shown in FIG. The injection timing CA4 of the low penetration injection P5 in the AFTER single shot-A pattern of FIG. 14C adopted when the air temperature is within the basic temperature range is set to be more retarded. Thus, when the outside air temperature is lower than the basic temperature range, the injection timing of the low penetration injection is delayed more than when the outside air temperature is within the basic temperature range. Owing to the retardation of the injection timing, the low penetration injection is performed in a divided manner and a large amount of fuel is injected, so that the oxidation and combustion of soot is promoted.

  On the other hand, when the outside air temperature is lower than the basic temperature range, that is, when soot is not easily generated, the AFTER single shot-B pattern in FIG. 14D is used. That is, the injection timing of the low penetration injection P5 is advanced more than when the outside air temperature is within the basic temperature range. This makes it possible to improve the fuel efficiency while appropriately oxidizing and burning the soot.

  As described above, in the second embodiment, in both the case where the PILOT region is utilized and the case where the AFTER region is utilized, the injection timing of the low penetration injection is low when the outside air temperature is high. It is a time on the more advanced side.

<Control flow of low penetration injection>
Subsequently, the flow of the low penetration injection control according to the second embodiment will be described with reference to the flowcharts shown in FIGS.

  Referring to FIG. 15, first, the same processing as the processing shown in steps S1 to S4 of FIG. 11 is executed. That is, the fuel injection control unit 71 (FIG. 5) of the processor 70 acquires information on the traveling area of the vehicle and the outside air temperature (step S11). Next, the operating state determination unit 73 determines whether or not the engine rotation speed and the engine load fall within the range of a predetermined traveling region (high load, high rotational speed operating state) (see FIG. 3). Step S12).

  When the vehicle does not fall within the predetermined traveling region (NO in step S12), the operating state determination unit 73 determines that the operation mode is not the operation mode for executing the low penetration injection, and the fuel injection control unit 71 prohibits the low penetration injection (step S12). S13). On the other hand, if it corresponds to the predetermined travel region (YES in step S12), remaining oxygen amount determination section 74 determines whether or not the amount of oxygen equal to or greater than the predetermined value remains in oxygen remaining area G2. (Step S14). When the oxygen amount equal to or more than the predetermined value does not remain in the oxygen remaining area G2 (NO in step S14), the fuel injection control unit 71 prohibits the low penetration injection (step S13).

  On the other hand, when the remaining oxygen amount determination unit 74 determines that the oxygen amount equal to or larger than the predetermined value remains in the oxygen remaining area G2 (YES in step S14), low penetration injection is performed. In this case, the mode determination unit 76 determines the current operation mode based on the set value data of the injection pressure of the injector 15 as described above (step S15). In step S15, it is determined whether the operation mode is the first region mode. As the injection pressure setting value data, a detection value of the injection pressure sensor SN7 or a calculation value calculated by the processor 70 according to the engine load can be used.

  When the current operation mode is the first region mode (YES in step S15), the injection pattern setting unit 77 determines whether or not the outside air temperature is within the basic temperature range (step S16). In FIG. 15 and the like, the basic temperature range is simply indicated as the basic range. When the outside air temperature is within the basic temperature range (YES in step S16), the injection pattern setting unit 77 sets the PILOT division-A pattern in FIG. 13A as the injection pattern of the low penetration injection (step S17). ). Thus, in the cycle, the injector 15 injects fuel in the pattern of PILOT division-A.

  On the other hand, when the outside air temperature is not within the basic temperature range (NO in step S16), the injection pattern setting unit 77 compares the air-fuel mixture in the combustion chamber 6 with the outside air temperature being higher than the basic temperature range. It is determined whether the environment is a highly ignitable environment in which the target is easily ignited or a low ignitable environment in which the outside air temperature is lower than the basic temperature range and the ignition is relatively difficult (step S18). When determining that the outside air temperature is higher than the basic temperature range (YES in step S18), the injection pattern setting unit 77 sets the PILOT single shot-B pattern in FIG. 13D as the injection pattern of the low penetration injection. (Step S19). On the other hand, when determining that the outside air temperature is lower than the basic temperature range, the injection pattern setting unit 77 sets the PILOT division-B pattern in FIG. 13B as the injection pattern (step S20).

  On the other hand, when the mode determining unit 76 determines that the current operation mode is not the first region mode in step S15 (NO in step S15), the process proceeds to the flow in FIG. In this case, the mode determination unit 76 determines whether the current operation mode is the second region mode (step S21). When the current operation mode is the second region mode (YES in step S21), the injection pattern setting unit 77 determines whether the outside air temperature is within the basic temperature range, as in step S16 (step S22). ). If the outside air temperature is within the basic temperature range (YES in step S22), the injection pattern setting unit 77 sets the PILOT single shot-A pattern in FIG. 13C as the injection pattern of the low penetration injection (step S23). ).

  On the other hand, when the outside air temperature is not within the basic temperature range (NO in step S22), the injection pattern setting unit 77 determines whether or not the outside air temperature is higher than the basic temperature range, as in step S18. It is determined whether the driving environment is a high ignitability environment or a low ignitability environment (step S24). When it is determined that the outside air temperature is higher than the basic temperature range and the condition is high ignitability (YES in step S24), the injection pattern setting unit 77 sets the injection pattern to the AFTER division-B pattern in FIG. Is set (step S25). On the other hand, when it is determined that the outside air temperature is lower than the basic temperature range and the low ignitability condition is satisfied (NO in step S24), the injection pattern setting unit 77 determines the injection pattern as the PILOT division-B in FIG. Are set (step S26).

  In step S21, when the mode determination unit 76 determines that the current operation mode is not the second region mode (NO in step S21), the process proceeds to the flow in FIG. In this case, the mode determination unit 76 determines whether the current operation mode is the third region mode (Step S31). When the current operation mode is the third region mode (YES in step S31), the injection pattern setting unit 77 determines whether or not the outside air temperature is within the basic temperature range, as in steps S16 and S22. Step S33). If the outside air temperature is within the basic temperature range (YES in step S33), the injection pattern setting unit 77 sets the AFTER division-A pattern in FIG. 14A as the injection pattern of the low penetration injection (step S34). ).

  On the other hand, when the outside air temperature is not within the basic temperature range (NO in step S33), the injection pattern setting unit 77 determines whether or not the outside air temperature is higher than the basic temperature range, similarly to steps S18 and S24. It is determined whether the current operating environment is an environment in which soot is easily generated or an environment in which soot is hardly generated (step S35). When it is determined that the condition is such that the outside air temperature is higher than the basic temperature range and soot is likely to be generated (YES in step S35), the injection pattern setting unit 77 sets the injection pattern to AFTER division-B in FIG. A pattern is set (step S36). On the other hand, when it is determined that the condition is such that the outside air temperature is lower than the basic temperature range and soot is not easily generated (NO in step S35), the injection pattern setting unit 77 determines the injection pattern as the PILOT single shot- The pattern of C is set (step S37).

  In step S31, when the mode determining unit 76 determines that the current operation mode is not the third region mode (NO in step S31), the process proceeds to the flow in FIG. In this case, the mode determination unit 76 determines whether the current operation mode is the fourth region mode (Step S41). When the current operation mode is the fourth region mode (YES in step S41), the injection pattern setting unit 77 determines whether the outside air temperature is within the basic temperature range, as in steps S16, S22, and 33. (Step S42). When the outside air temperature is within the basic temperature range (YES in step S42), the injection pattern setting unit 77 sets the AFTER single-B pattern in FIG. 14D as the injection pattern of the low penetration injection (step S45). .

  On the other hand, when the outside air temperature is not within the basic temperature range (NO in step S42), the injection pattern setting unit 77 determines whether the outside air temperature is higher than the basic temperature range, similarly to steps S18, S24, and S35. That is, it is determined whether the current operating environment is an environment where soot is easily generated or an environment where soot is hardly generated (step S44). When it is determined that the condition is such that the outside air temperature is higher than the basic temperature range and soot is likely to be generated (YES in step S44), the injection pattern setting unit 77 sets the injection pattern to AFTER division-B in FIG. A pattern is set (step S45). On the other hand, when it is determined that the condition is such that the outside air temperature is lower than the basic temperature range and the ignitability is low and soot is not easily generated (NO in step S44), the injection pattern setting unit 77 sets the injection pattern in FIG. The pattern of AFTER single shot-B) is set (step S46).

  When it is determined in step S14 that the operation mode is not in the fourth region (NO in step S41), the current operation mode is referred to as an irregular state that does not correspond to any of the first to fourth region modes. Will be. In this case, the fuel injection control unit 71 prohibits the low penetration injection (step S13).

[Effects]
According to the diesel engine fuel injection control device according to the present embodiment described above, the following operation and effect can be obtained. The bottom surface of the combustion chamber 6 of the diesel engine to be controlled is defined by a crown surface 50 including first and second cavities 51 and 52 and a connecting portion 53 connecting the two. Then, the fuel injection control section 71 causes the injector 15 to execute the main injection P1 or the pilot injection P2 directed to the connection section 53. For this reason, the in-cylinder flow of the air-fuel mixture is separated at the connecting portion 53, the in-cylinder swirling flow becomes relatively weak, and air near the central region of the combustion chamber 6 in the radial direction B is less likely to be drawn radially outward. There is a tendency.

  However, according to the fuel injection control device, the fuel injection control unit 71 injects fuel only in the radially central region of the combustion chamber 6 in addition to the normal main injection P1 and pilot injection P2, that is, in-cylinder. The injector 15 performs the low penetration injection in which the outer edge H (FIG. 8) of the central region where oxygen can remain due to the weakening of the swirling flow is targeted for penetration. Therefore, an air-fuel mixture can be formed by the air remaining in the radial center region of the combustion chamber 6 and the fuel sprayed by the low penetration injection. Further, since the outer edge H is set as the penetration target, it is possible to form the air-fuel mixture by fully utilizing the air existing in the radially central region. As a result, a uniform and thin air-fuel mixture is formed by effectively utilizing the air in the combustion chamber 6, and high-quality diesel combustion in which generation of soot and the like is suppressed can be realized.

  Further, as described above, the fuel injection control unit 71 sets the injection timing of the low penetration injection to a timing on the retard side when the outside air temperature is higher than the basic range as compared with when it is within the basic range. Further, when the outside air temperature is lower than the basic range, the injection timing of the low penetration injection is set to the advanced side timing as compared with when it is within the basic range. That is, the fuel injection control unit 71 delays the injection timing of the low penetration injection when the outside air temperature is high as compared with when the outside air temperature is low.

  Therefore, in the case where the operating mode is the first or second region mode, when the outside air temperature is high and premature ignition is likely to occur, the ignition timing of the low penetration injection is retarded and the low penetration injection causes the combustion chamber 6 to enter the combustion chamber 6. Mixing of the supplied fuel and air can be suppressed, and the occurrence of premature ignition can be prevented. Further, in the case where the operation mode is the first or second region mode, when the outside air temperature is low and the ignition delay easily occurs, the fuel is supplied to the combustion chamber 6 by the low penetration injection due to the advance of the injection timing of the low penetration injection. It is possible to promote the mixing of the fuel and the air thus generated, and to prevent ignition delay.

  Further, in the case where the operation mode is set to the third or fourth region mode, when the outside air temperature is high and soot is easily generated, the fuel is supplied to the combustion chamber 6 by the low penetration injection due to the delay of the injection timing of the low penetration injection. The oxidation and combustion of soot can be promoted by the combustion energy of the fuel. Further, in the case where the operation mode is the third or fourth region mode, when the outside air temperature is low and soot is not easily generated, the fuel consumption performance can be improved by advancing the injection timing of the low penetration injection.

  Further, the fuel injection control unit 71 prohibits the low penetration injection when the spray penetration of the main injection P1 or the pilot injection P2 is larger than a predetermined set amount (Steps S2 and S3 in FIG. 11 and Step S12 in FIG. 15). , S13). The spray penetration of the main injection P1 or the pilot injection P2 becomes larger than the predetermined set amount, for example, when the engine load is large and the fuel injection amount in these injections is relatively large. In such a case, no air remains in the radially central area of the combustion chamber 6 (the oxygen remaining area G2 does not occur). Therefore, by prohibiting the low penetration injection, the mixture is excessively enriched. Can be prevented.

  Further, the fuel injection control unit 71 prohibits the low penetration injection under the condition that the oxygen amount in the radial center region of the combustion chamber 6 is equal to or less than a predetermined value (steps S4 and S3 in FIG. 11 and step S14 in FIG. 15). , S13). Under the condition where the oxygen amount in the radially central region of the combustion chamber 6 is low, it is not necessary to execute low penetration injection in the first place even under the condition where the oxygen remaining area G2 is generated. Under such conditions, the fuel injection control unit 71 prohibits low penetration injection, so that unnecessary fuel consumption can be prevented.

[Modification]
As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the embodiments. For example, the following modified embodiments can be adopted.

  (1) In the above-described embodiment, an example in which the main injection P1, the pilot injection P2, and the after injection P3 are executed as the basic injection pattern has been described (FIGS. 10, 13, and 14). The basic injection pattern only needs to include at least the main injection P1 and the pilot injection P2, and the after injection P3 may be omitted. Further, in the above-described embodiment, an example has been described in which the pilot injection P2 is executed separately in two times, that is, the first pilot injection P21 and the second pilot injection P22. Instead, the pilot injection P2 may be a single injection or three or more injections. Further, in the above-described embodiment, an example is described in which the main injection P1 is an injection having the maximum energy (injection amount). However, the pilot injection P2 is set to the maximum injection amount, and the pilot injection P2 is directed to the connecting portion 53. It is good also as an aspect. In this case, the outer edge H of the oxygen remaining area G2, that is, the target line H1, is set by the injection range setting section 72 based on the injection amount, the injection pressure, and the injection timing of the pilot injection P2.

  (2) In the above-described embodiment, the injection timing of the low penetration injection is selectively used according to the operating state or the environment, the timing earlier than the pilot injection P2 (PILOT region) or the timing later than the main injection P1 (AFTER region). Examples have been given. Instead, the low penetration injection may be executed in both the PILOT region and the AFTER region in consideration of the function in each region. Alternatively, low penetration injection may be performed only in one of the PILOT region and the AFTER region.

  (3) In the above-described embodiment, when the low penetration injection is executed by the split injection, the example in which the injection is divided into two injections is described, but the injection may be performed three or more times. Further, in the PILOT division-B control of FIG. 13B and the AFTER division-B control of FIG. 14B, an example is shown in which the interval of the divided injection is reduced or enlarged as compared with the injection control in the center region. . Instead, the control may be such that the interval is not changed.

  (4) In the above embodiment, the patterns (PILOT split-A, PILOT split-B, PILOT single shot-A, PILOT split-B, PILOT single shot-C, AFTER split-A, AFTER split-B, AFTER single shot-A, AFTER single shot-B) are set, and these injection patterns are switched according to the outside air temperature. The example in which the injection timing of the low penetration injection is retarded when the temperature is high compared to when it is low is shown. Alternatively, only the injection timing of the low penetration injection may be changed without changing the injection pattern.

  More specifically, as the injection patterns, PILOT-split that performs low penetration injection twice before pilot injection, PILOT-single shot that performs single low injection before pilot injection, and AFTER injection After that, AFTER-split which performs low penetration injection twice and AFTER-split which executes low penetration injection once after AFTER injection are set. Also, PILOT-division is performed in the first region mode, PILOT-single operation is performed in the second region mode, AFTER-division is performed in the third region mode, and AFTER-single operation is performed in the fourth region mode. To be configured. Then, while performing the above-described injection pattern in each operation mode, the injection timing of the low penetration injection may be changed according to the outside air temperature (when the outside air temperature is high, the injection timing of the low penetration injection is lower than when the outside air temperature is low. Set to be retarded).

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Cylinder 4 Cylinder head 44 EGR apparatus 5 Piston 50 Crown surface 5C cavity 51 First cavity part 512 First bottom part 52 Second cavity part 522 Second bottom part 53 Connection part 6 Combustion chamber 6U Combustion chamber ceiling surface (cylinder head) Underside of
15 Injector (fuel injection valve)
70 Processor (Diesel engine fuel injection control device)
71 Fuel injection control unit (first injection control unit, second injection control unit)
P1 Pilot injection P2 Main injection P4, P5 Low penetration injection

Claims (6)

A combustion chamber of the engine formed by the lower surface of the cylinder head, the cylinder and the crown of the piston,
A fuel injection valve for injecting fuel into the combustion chamber,
A fuel injection control unit that controls the operation of the fuel injection valve, and a fuel injection control device for a diesel engine comprising:
A cavity is provided in a crown surface of the piston, and the cavity includes:
A first cavity portion disposed in a radial center region of the crown surface and having a first bottom portion having a first depth in a cylinder axis direction;
A second cavity portion provided on the outer peripheral side of the first cavity portion on the crown surface, the second cavity portion including a second bottom portion having a depth smaller than the first depth in a cylinder axis direction;
A connection portion that connects the first cavity portion and the second cavity portion,
The fuel injection valve is for injecting fuel toward the cavity, and is disposed at or near a radial center of the combustion chamber,
The fuel injection control unit,
A main injection for performing fuel injection at least at a timing when the piston is located near the compression top dead center, a pilot injection for performing fuel injection at a timing earlier than the main injection, and a timing earlier than the pilot injection or the main injection. And low-penetration injection to perform the fuel injection at a timing later than the injection, and to cause the fuel injection valve to execute,
A first injection control unit configured to execute at least one of the main injection and the pilot injection at a timing of injecting fuel by directing the connection unit;
A second injection control unit that executes the low penetration injection so that fuel injection is performed only in a radially central region of the combustion chamber,
The fuel injection control device for a diesel engine, wherein the second injection control unit delays the injection timing of the low penetration injection when the outside air temperature is high as compared to when the outside air temperature is low. The fuel injection control device for a diesel engine according to claim 1,
The second injection control unit causes the low penetration injection to be executed at an earlier timing than the pilot injection when the outside air temperature is lower than a predetermined reference temperature,
The fuel injection control device for a diesel engine, wherein the second injection control unit executes the low penetration injection at a timing later than the main injection when an outside air temperature is equal to or higher than the reference temperature. The fuel injection control device for a diesel engine according to claim 1,
The second injection control unit executes the low penetration injection at an earlier timing than the pilot injection, and delays the injection timing of the low penetration injection when the outside air temperature is high compared to when the outside air temperature is low, A fuel injection control device for a diesel engine. The fuel injection control device for a diesel engine according to claim 1,
The second injection control unit executes the low penetration injection at a later timing than the main injection, and delays the injection timing of the low penetration injection when the outside air temperature is higher than when the outside air temperature is low, A fuel injection control device for a diesel engine. The fuel injection control device for a diesel engine according to any one of claims 1 to 4,
The fuel injection control device for a diesel engine, wherein the second injection control unit executes the low penetration injection so that an outer edge of the radially central region of the combustion chamber becomes a spray penetration. The fuel injection control device for a diesel engine according to any one of claims 1 to 5,
The second injection control unit sets an oxygen remaining area generated in a radially central area of the combustion chamber based on an injection pressure, an injection amount, and an injection timing of the main injection or the pilot injection by the first injection control unit. The fuel injection control device for a diesel engine, wherein the low-penetration injection is performed such that the outer periphery of the oxygen remaining area is assumed to be a spray penetration.

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