JP7137145B2 - vehicle controller - Google Patents

Description

The present invention relates to a control device for a vehicle equipped with an engine system including a compression ignition engine and a motor connected to the output shaft of the engine and capable of generating electricity.

In a compression ignition engine, air and fuel are mixed in advance, and by adopting a premixed compression ignition system that compresses the mixture and burns it at once, improving fuel efficiency by shortening the combustion period. can be done. However, combustion by homogeneous charge compression ignition tends to increase combustion noise because the heat release rate peak rises steeply. Therefore, when the vehicle in which the engine is mounted travels at a low speed, the running noise is small, so the magnitude of the combustion noise is conspicuous.

In a compression ignition engine, it is known to inject fuel from an injector in multiple stages. Patent Literature 1 discloses a control device for a diesel engine that executes main injection and pilot injection that precedes the main injection. The control device of Patent Document 1 performs control to reduce the amount of fuel injected by the pilot injection when the vehicle interior noise is large compared to when the vehicle interior noise is small.

JP 2006-242125 A

An engine system is known in which a motor capable of generating electricity is connected to the output shaft of a compression ignition engine, and an in-vehicle secondary battery is charged with electric power generated by the motor and assists the engine. In such an engine system, the engine load fluctuates due to the addition of motor resistance, not based on the driver's accelerator work. Therefore, in order to reduce the combustion noise of homogeneous charge compression ignition combustion, it is necessary to perform control that takes into account the addition of motor resistance, but the current situation is that no useful control technology has been proposed yet.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for a vehicle that is equipped with a compression ignition engine and a motor that can generate electricity and that can ensure both quietness and excellent fuel efficiency of the vehicle.

A vehicle control device according to one aspect of the present invention includes a compression ignition engine including a fuel injection valve capable of injecting fuel into a combustion chamber in multiple stages from a compression stroke to an expansion stroke, and an output shaft of the compression ignition engine. A control device for a vehicle equipped with an engine system including a motor capable of generating electricity connected to a vehicle, wherein the operation of the fuel injection valve is controlled based on the amount of depression of the accelerator and the motor resistance when the motor generates electricity. A fuel injection control unit that controls, a motor control unit that controls the operation of the motor, and a vehicle speed detection unit that detects the vehicle speed of the vehicle, and the fuel injection control unit injects fuel during a compression stroke. The fuel injection valve is caused to execute first-stage injection and main injection in which injection is started near compression top dead center and completed during the expansion stroke, and the vehicle speed exceeds a first predetermined value. When the vehicle speed detection unit detects this, and the motor control unit does not issue an instruction to add motor resistance, the injection amount of the front stage injection is set to be larger than the injection amount of the main injection. While the first injection pattern to be set is executed, if the motor control unit issues an instruction to add motor resistance, the injection amount of the first stage injection is set smaller than the injection amount of the main injection. It is characterized by executing two injection patterns.

According to this control device, when the vehicle is running at a vehicle speed exceeding the first predetermined value and the motor control unit does not issue an instruction to add motor resistance, that is, when the fuel injection control unit controls the acceleration The first injection pattern is selected when the fuel injection control is performed based only on the depression amount. In the first injection pattern, the injection amount of the first stage injection performed during the compression stroke is set larger than the injection amount of the main injection. Therefore, the heat release rate peak can appear near the compression top dead center due to the combustion by the first stage injection. That is, it is possible to realize premixed compression ignition combustion in the first stage injection, thereby improving the fuel efficiency.

On the other hand, when the motor control unit issues an instruction to add motor resistance, that is, when the fuel injection control unit performs fuel injection control based on the amount of depression of the accelerator and the motor resistance, the second injection pattern is selected. Since the engine load increases when the motor resistance is added, the fuel injection control section must perform control to increase the fuel injection amount in order to maintain the vehicle speed. In this case, if the first injection pattern is continued, combustion noise also increases. Since the increase in the engine load here is not based on the driver's accelerator work, the driver may feel uncomfortable when the combustion noise increases. Therefore, in such a situation, the second injection pattern is selected, and the injection amount of the first stage injection is set smaller than the injection amount of the main injection. As a result, the heat release rate characteristic associated with combustion does not show a sharp change, and the heat release rate peak appears on the retarded side compared to when the first injection pattern is executed. Therefore, combustion noise can be suppressed when the motor resistance is added.

In the control device described above, the fuel injection control unit causes the second-stage injection to be executed at least once between the first-stage injection and the main injection when the injection of the second injection pattern is executed. Moreover, it is desirable to set the injection amount so that it increases in the order of the first stage injection, the second stage injection, and the main injection.

According to this control device, by increasing the fuel injection amount in the order described above, it is possible to suppress a sharp rise in the heat release rate in the combustion by the main injection, and further reduce the combustion noise during low-speed running. be able to. Moreover, since the second stage injection is added, the penetration of each injection is suppressed, making it easier to suppress the adhesion of fuel to the cylinder wall surface.

In the control device described above, when the vehicle speed detection unit detects a vehicle speed exceeding a second predetermined value that is greater than the first predetermined value by a predetermined value, the fuel injection control unit controls the motor It is desirable to execute the first injection pattern even when the control unit issues an instruction to add motor resistance.

When the vehicle is traveling at a considerably high speed (in the case of a vehicle speed exceeding the second predetermined value), the running noise also becomes considerably loud enough to drown out the combustion noise. According to the above-described control device, the driver does not feel uncomfortable in such a case, so the first injection pattern that exhibits excellent fuel efficiency performance is maintained without changing to the second injection pattern. As a result, the fuel consumption performance of the vehicle can be improved.

In the control device described above, the fuel injection control unit controls, when the first injection pattern is executed, a first pressure wave generated due to combustion due to the first stage injection and a pressure wave generated due to combustion due to the main injection. It is desirable to execute the first stage injection and the main injection such that the second pressure wave appears with a 1/2 cycle shift from each other.

While the engine combustion noise tends to be drowned out by running noise (such as wind noise) during high-speed travel (when the vehicle speed exceeds the first predetermined value), it is desirable to suppress the combustion noise as much as possible. According to the above control device, the first pressure wave and the second pressure wave appear with a shift of 1/2 period from each other, so that these pressure waves cancel each other out. Therefore, combustion noise can be reduced during high-speed running.

In the control device described above, the fuel injection control unit controls, during execution of the first injection pattern, an injection period shorter than that of the first stage injection and the main injection at a timing between the first stage injection and the main injection. It is desirable to further execute middle-stage injection in which fuel is injected at .

According to this control device, the fuel injected by the intermediate injection in the short injection period becomes difficult to reach the radially outer side of the combustion chamber, and is exclusively mixed with the air near the radial center of the combustion chamber to form an air-fuel mixture. and lead to combustion. That is, in the middle stage injection, the oxygen in the region of the combustion chamber that is not used in the first stage injection and the main injection is actively utilized to form the air-fuel mixture. As a result, the oxygen existing in the combustion chamber can be effectively used, and the generation of soot and the like can be suppressed. Further, since the intermediate injection is performed at a timing between the first injection and the main injection, the combustion by the intermediate injection can contribute to the engine torque.

In the above control device, a part of the combustion chamber is defined by a crown surface of the piston, and a cavity is provided in the crown surface of the piston, and the cavity is arranged in a radially central region of the crown surface. a lower cavity having a first bottom portion having a first depth in the cylinder axial direction; and a lower cavity portion disposed on the crown surface on the outer peripheral side of the lower cavity portion and shallower than the first depth in the cylinder axial direction. The fuel injector includes an upper cavity with a second bottom having a second depth, and a lip connecting the lower cavity and the upper cavity, wherein the fuel injector injects fuel toward the cavity. The fuel injection control unit is arranged in the radial center of the combustion chamber or in the vicinity thereof, and the fuel injection control unit is arranged such that, in both the first injection pattern and the second injection pattern, the fuel injection by the front stage injection reaches the lip. While setting the fuel injection timing so as to direct the fuel injection timing, it is desirable to execute the leading stage injection of the first injection pattern at a retarded angle relative to the leading stage injection of the second injection pattern.

According to this control device, the head-stage injection is performed by directing the fuel toward the lip, so that the air utilization rate in the combustion chamber can be increased. That is, when fuel is injected from the fuel injection valve toward the cavity, a mixture of the fuel and the air in the combustion chamber flows toward the first bottom portion and the second bottom portion. Therefore, the air-fuel mixture can be easily directed radially inward and outward of the combustion chamber, and the air in the combustion chamber can be effectively utilized to form a homogeneous and thin air-fuel mixture, thereby suppressing the generation of soot. In addition, since the first injection of the first injection pattern is executed on the retarded side where the pressure in the combustion chamber increases, it becomes easier to execute premixed compression ignition combustion during high-speed running.

According to the present invention, it is possible to provide a vehicle control device capable of ensuring both quietness of the vehicle and excellent fuel efficiency performance in a vehicle equipped with a compression ignition engine and a motor capable of generating electricity.

FIG. 1 is a schematic diagram of a vehicle to which an engine control device according to the present invention is applied. FIG. 2 is a system diagram of a diesel engine to which the engine control device according to the present invention is applied. FIG. 3(A) is a perspective view of the crown portion of the piston of the diesel engine shown in FIG. 2, and FIG. 3(B) is a perspective view with a section of the piston. FIG. 4 is an enlarged view of the cross section of the piston shown in FIG. 3(B). FIG. 5 is a cross-sectional view of the piston for explaining the relationship between the crown surface of the piston and the injection axis of fuel by the injector. FIG. 6 is a block diagram showing the control system of the engine. FIG. 7 is a diagram showing an operation map of the engine. FIG. 8 is a time chart showing an example of the fuel injection timing and heat release rate when the low-speed injection pattern (second injection pattern) is executed. FIG. 9 is a time chart showing an example of the timing of fuel injection and the heat generation rate when the high-speed injection pattern (first injection pattern) is executed. FIG. 10 is a time chart showing injection pattern switching control when motor resistance is added. FIGS. 11A and 11B are time charts comparing the first injection pattern and the second injection pattern. FIG. 12(A) is a graph showing intervals of peaks of heat release rate of combustion by first stage injection and main injection, and FIG. 12(B) is a schematic for explaining the effect of canceling pressure waves generated by these combustions. It is a diagram. FIG. 13 is a graph showing changes in heat release rate characteristics due to middle-stage injection. FIG. 14 is a cross-sectional view of the combustion chamber showing the flow state of the air-fuel mixture in the first stage injection of the first injection pattern. FIG. 15 is a cross-sectional view of the combustion chamber, showing the area where combustion occurs due to the first stage injection of the first injection pattern. FIG. 16 is a cross-sectional view of a combustion chamber showing a region where combustion occurs due to middle-stage injection. FIG. 17 is a cross-sectional view of a combustion chamber showing a region where combustion occurs due to main injection of the first injection pattern. FIG. 18 is a flow chart showing an example of fuel injection control.

[Vehicle configuration]
An embodiment of a vehicle control device according to the present invention will be described in detail below with reference to the drawings. This embodiment shows an example in which the present invention is applied to control of a vehicle equipped with a diesel engine, which is an example of a compression ignition engine. FIG. 1 is a schematic diagram of a vehicle 100 to which an engine control device according to the present invention is applied. A vehicle 100 is equipped with an engine body 1, a transmission 81, a motor 82, a battery 83, and a processor 70 (engine control device) of a diesel engine system, which will be described in detail with reference to FIG.

The transmission 81 is connected to the output shaft (crankshaft) of the engine body 1 , and in the process of transmitting the engine output to the drive wheels of the vehicle 100 , changes the torque and rotation speed to required values. The motor 82 is an electric motor capable of generating electricity, and its motor shaft is always connected to the output shaft of the engine body 1 by a timing belt 84 . The battery 83 is a rechargeable secondary battery.

The motor 82 performs an engine assist operation and a charging operation for the battery 83 . The engine assist operation is an operation of transmitting the torque of the motor 82 to the output shaft of the engine body 1 via the timing belt 84, for example, when the vehicle 100 is rapidly accelerated or restarted after idling stop. At this time, power is supplied from the battery 83 to the motor 82 . The charging operation is an operation of causing the motor 82 to function as a generator when a charge request for the battery 83 is generated, for example, when the remaining amount of the battery 83 is insufficient or when the vehicle 100 decelerates. In this case, in addition to the normal load, the engine main body 1 is superimposed with motor resistance that rotationally drives the rotor of the motor 82 as a generator.

[Overall structure of the engine]
Next, the overall configuration of the diesel engine system mounted on the vehicle 100 as a power source for running will be described with reference to FIG. The diesel engine system includes the engine main body 1, an intake passage 30 through which intake air introduced into the engine main body 1 flows, an exhaust passage 40 through which exhaust gas discharged from the engine main body 1 flows, and an exhaust passage 40. An EGR device 44 that recirculates a part of the exhaust gas passing through the exhaust passage 30 , and a turbocharger 46 that is driven by the exhaust gas passing through the exhaust passage 40 .

The engine body 1 is a four-cycle diesel engine that is driven by being supplied with fuel containing light oil as a main component. The engine body 1 has a plurality of cylinders 2 (only one of which is shown in FIG. 2) arranged in a direction perpendicular to the paper surface of FIG. is the engine. The engine body 1 includes a cylinder block 3 , a cylinder head 4 and pistons 5 . Cylinder block 3 has a cylinder liner that forms cylinder 2 . The cylinder head 4 is attached to the upper surface of the cylinder block 3 and closes the upper opening of the cylinder 2 . A piston 5 is housed in the cylinder 2 so as to be reciprocally slidable, and is connected to the crankshaft 7 via a connecting rod 8 . As the piston 5 reciprocates, the crankshaft 7 rotates about its central axis. The structure of the piston 5 will be detailed later.

A combustion chamber 6 is formed above the piston 5 . The combustion chamber 6 is defined by the lower surface of the cylinder head 4 (combustion chamber ceiling surface 6U, see FIG. 4 ), the crown surfaces 50 of the cylinder 2 and the piston 5 . The fuel is supplied to the combustion chamber 6 by injection from an injector 15, which will be described later. A mixture of the supplied fuel and air is combusted in the combustion chamber 6, and the piston 5, which is pushed down by the expansion force of the combustion, reciprocates vertically.

A crank angle sensor SN1 and a water temperature sensor SN2 are attached to the cylinder block 3 . The crank angle sensor SN1 detects the rotation angle (crank angle) of the crankshaft 7 and the rotation speed of the crankshaft 7 (engine rotation speed). The water temperature sensor SN2 detects the temperature of cooling water (engine water temperature) flowing inside the cylinder block 3 and the cylinder head 4 .

An intake port 9 and an exhaust port 10 communicating with the combustion chamber 6 are formed in the cylinder head 4 . An intake side opening, which is the downstream end of the intake port 9 , and an exhaust side opening, which is the upstream end of the exhaust port 10 , are formed on the lower surface of the cylinder head 4 . The cylinder head 4 is assembled with an intake valve 11 that opens and closes the intake side opening and an exhaust valve 12 that opens and closes the exhaust side opening. Although illustration is omitted, the valve format of the engine body 1 is a 4-valve format of 2 intake valves x 2 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 also provided.

The cylinder head 4 is provided with an intake-side valve mechanism 13 and an exhaust-side valve mechanism 14 including camshafts. The intake valve 11 and the exhaust valve 12 are driven to open and close by these valve mechanisms 13 and 14 in conjunction with the rotation of the crankshaft 7 . The intake valve mechanism 13 incorporates an intake VVT capable of changing at least the opening timing of the intake valve 11, and the exhaust valve mechanism 14 incorporates an exhaust VVT capable of changing at least the closing timing of the exhaust valve 12. It is

One injector 15 (fuel injection valve) for injecting fuel into the combustion chamber 6 from the tip of the cylinder head 4 is attached to each cylinder 2 . The injector 15 is assembled to the cylinder head 4 and formed on the crown surface 50 of the piston 5 so that the tip (nozzle 151; FIG. 14) for injecting fuel is positioned at or near the radial center of the combustion chamber 6. The fuel is injected toward a cavity 5C (FIGS. 2 to 4), which will be described later. As the injector 15 of this embodiment, one capable of injecting fuel into the combustion chamber in multiple stages from the compression stroke to the expansion stroke is selected. For this reason, it is desirable to use a high-speed response type injector 15 having a valve opening response speed (the time required from the start of energization to the completion of valve opening) of about 50 μs to 200 μs.

The injector 15 is connected to a pressure accumulation common rail (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 pressure-accumulated in this common rail is supplied to the injector 15 of each cylinder 2, and fuel is injected into the combustion chamber 6 from each injector 15 at a high pressure (approximately 50 MPa to 250 MPa). A fuel pressure regulator 16 (not shown in FIG. 2, see FIG. 6) is provided between the fuel pump and the common rail to change the injection pressure, which is the pressure of the fuel injected from the injector 15.

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 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 . An air cleaner 31 , a turbocharger 46 , a throttle valve 32 , an intercooler 33 and a surge tank 34 are arranged in the intake passage 30 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 depression of an accelerator (not shown) to adjust the 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 turbocharger 46 . The surge tank 34 is a tank that is arranged immediately upstream of the intake manifold connected to the intake port 9 and provides a space for evenly distributing the intake air to the plurality of cylinders 2 .

An airflow sensor SN3, an intake air temperature sensor SN4, an intake pressure sensor SN5 and an intake _O2 sensor SN6 are arranged in the intake passage 30. As shown in FIG. The airflow sensor SN3 is arranged on the downstream side of the air cleaner 31 and detects the flow rate of intake air passing through this portion. The intake air temperature sensor SN4 is arranged downstream of the intercooler and detects the temperature of the intake air passing through that portion. An intake pressure sensor SN5 and an intake _O2 sensor SN6 are arranged in the vicinity of the surge tank 34, and detect the pressure of the intake air passing through these portions and the oxygen concentration of the intake air, respectively. Although not shown in FIG. 2, an injection pressure sensor SN7 (FIG. 6) 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 . Burned gas (exhaust gas) generated in the combustion chamber 6 is discharged outside 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 an oxidation catalyst 42 that oxidizes harmful components (CO and HC) contained in the exhaust gas to render them harmless, and a DPF (diesel filter) for collecting particulate matter contained in the exhaust gas. • A particulate filter) 43 is incorporated. Note that a NOx catalyst that reduces NOx to make it harmless may be further arranged at a position downstream of the exhaust purification device 41 in the exhaust passage 40 .

An exhaust _O2 sensor SN8 and a differential pressure sensor SN9 are arranged in the exhaust passage 40 . The exhaust _O2 sensor SN8 is arranged between the turbocharger 46 and the exhaust purification device 41, and detects the oxygen concentration of the exhaust passing through that portion. A 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 connecting the exhaust passage 40 and the intake passage 30, and an EGR valve 45 provided in the EGR passage 44A. The EGR passage 44A connects a portion of the exhaust passage 40 upstream of the turbocharger 46 and a portion of the intake passage 30 between the intercooler 33 and the surge tank 34 to each other. An EGR cooler (not shown) is arranged in the EGR passage 44A to cool the exhaust gas (EGR gas) recirculated from the exhaust passage 40 to the intake passage 30 by heat exchange. The EGR valve 45 adjusts the flow rate of exhaust gas flowing through the EGR passage 44A.

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

[Detailed structure of the piston]
Next, the structure of the piston 5, especially the structure of the crown surface 50 will be described in detail. FIG. 3A is a perspective view mainly showing the upper portion of the piston 5. FIG. The piston 5 has an upper piston head and a lower skirt portion, and FIG. 3A shows the piston head portion having a crown surface 50 on its top surface. FIG. 3B is a perspective view of the piston 5 with a radial cross section. FIG. 4 is an enlarged view of the radial cross section shown in FIG. 3(B). In FIGS. 3A and 3B, the axial direction A of the cylinder and the radial direction B of the combustion chamber are indicated by arrows.

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

The cavity 5</b>C includes a lower cavity 51 , an upper cavity 52 , a lip 53 and peaks 54 . The lower cavity 51 is a recess that is arranged in the center region of the crown surface 50 in the radial direction B and recessed downward in the cylinder axial direction A from the crown surface 50 . The upper cavity 52 is an annular recess that is arranged on the crown surface 50 on the outer peripheral side of the lower cavity 51 and recessed downward in the cylinder axial direction A from the crown surface 50 . The lip 53 is a portion that connects the lower cavity 51 and the upper cavity 52 in the radial direction B. As shown in FIG. The peak portion 54 is a peak-shaped convex portion arranged at the center position in the radial direction B of the crown surface 50 (lower cavity 51). The peak portion 54 is protruded at a position directly below the nozzle 151 of the injector 15 (FIG. 14).

The lower 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 lower cavity 51 and continues to the lip 53 . The first bottom portion 512 is the most recessed area in the lower cavity 51 and has an annular shape when viewed from above. The first bottom 512 is the deepest part of the cavity 5C as a whole, and the lower cavity 51 has a predetermined depth (first depth) in the cylinder axial direction A at the first bottom 512 . When viewed from the top, the first bottom portion 512 is positioned close to the inside in the radial direction B with respect to the lip 53 .

The first upper end portion 511 and the first bottom portion 512 are connected by a radial recess portion 514 curved outward in the radial direction B. As shown in FIG. The radial recessed portion 514 has a portion recessed outward in the radial direction B from the lip 53 . The first inner end portion 513 is located at the radially innermost position in the lower cavity 51 and continues to the lower end of the peak portion 54 . The first inner end portion 513 and the first bottom portion 512 are connected by a curved surface gently curved in a foot shape.

The upper cavity 52 includes a second inner end 521 , a second bottom 522 , a second top end 523 , a descending plane 524 and a standing wall region 525 . The second inner end portion 521 is located at the radially innermost position in the upper cavity 52 and continues to the lip 53 . The second bottom 522 is the most recessed area in the upper cavity 52 . The upper cavity 52 has a depth (second depth) shallower than the first bottom 512 in the cylinder axial direction A at the second bottom 522 . The second upper end portion 523 is located at the highest position and radially outermost in the upper cavity 52 and continues to the squish area 55 .

The descending plane 524 is a portion that extends from the second inner end portion 521 toward the second bottom portion 522 and has a planar shape that slopes downward in the radial direction outward. As shown in FIG. 4, the descending plane 524 has a slope along a slope line C2 that intersects a horizontal line C1 extending in the radial direction B at a slope angle α.

The standing wall region 525 is a wall surface formed to rise relatively steeply on the radially outer side of the second bottom portion 522 . In the cross-sectional shape in the radial direction B, the wall surface of the upper cavity 52 is curved upward from the horizontal direction from the second bottom portion 522 to the second upper end portion 523 . A standing wall region 525 is a wall surface near the vertical wall. The lower portion of the standing wall region 525 is located inside in the radial direction B with respect to the upper end position of the standing wall region 525 . As a result, the air-fuel mixture is prevented from returning too much to the inside of the combustion chamber 6 in the radial direction B, and combustion can be performed by effectively utilizing the space (squish space) radially outside the standing wall region 525. - 特許庁

The lip 53 has a cross-sectional shape in the radial direction B that protrudes radially inward in the shape of a hump between the lower cavity 51 positioned on the lower side and the upper cavity 52 positioned on the upper side. The lip 53 has a lower end portion 531, a third upper end portion 532 (upper end portion in the axial direction of the cylinder), and a central portion 533 located in the middle between them. The lower end portion 531 is a continuous portion with respect to the first upper end portion 511 of the lower cavity 51 . The third upper end portion 532 is a continuous portion with respect to the second inner end portion 521 of the upper cavity 52 .

In the cylinder axial direction A, the lower end portion 531 is the lowest portion of the lip 53, and the third upper end portion 532 is the uppermost portion thereof. The descending plane 524 described above is also the area extending from the third top end 532 toward the second bottom 522 . The second bottom portion 522 is located below the third upper end portion 532 . In other words, the upper cavity 52 of this embodiment does not have a bottom surface extending horizontally outward in the radial direction B from the third upper end portion 532. In other words, from the third upper end portion 532 to the squish area 55 It has a second bottom portion 522 that is recessed below the third upper end portion 532 instead of being connected on a horizontal plane.

The peak portion 54 protrudes upward, but its protrusion height is the same as the height of the third upper end portion 532 of the lip 53 and is recessed from the squish area 55 . The peak portion 54 is positioned at the center of the circular lower cavity 51 when viewed from the top, so that the lower cavity 51 is in the form of an annular groove formed around the peak portion 54 .

[Regarding the curved shape of the cavity]
FIG. 5 is a cross-sectional view along the cylinder axial direction A for explaining the curved shapes of the first and second cavities 51 and 52 and the lip 53. As shown in FIG. The lower cavity 51 has a surface shape along a Cartesian egg-shaped elliptic curve (hereinafter referred to as an egg shape) in a cross section including the cylinder axis. Specifically, the lower cavity 51 includes a first arc-shaped portion R1 farthest from the injector 15 (injection hole 152), a second portion R2 located between the first portion R1 and the lip 53, and a first and a third portion R3 extending inward in the radial direction B from the portion R1. When applied to the shape of FIG. 4 described above, the first portion R1 is in the central region of the radial recess portion 514, the second portion R2 is in the region extending from the radial recess portion 514 to the first upper end portion 511, and The three portions R3 respectively correspond to regions extending from the radially recessed portion 514 to the first bottom portion 512 .

FIG. 5 shows a state in which the injection axis AX of fuel injected from the injector 15 intersects the first portion R1 farthest from the injector 15 . In the egg-shaped shape of the lower cavity 51, the radius r1 of the first portion R1 is the smallest, and the radius r1 increases from the first portion R1 toward the second portion R2, and from the first portion R1 to the third portion R3. It is an arc shape whose radius increases continuously toward the direction side. That is, the radius r2 of the second portion R2 increases as it moves away from the first portion R1 in the counterclockwise direction in the cross section of FIG. Also, the radius r3 of the third portion R3 increases at the same rate as the radius r2 of the second portion R2 as the distance from the first portion R1 increases in the clockwise direction (r2=r3). Expressing the egg-shaped shape with the lip 53 as a starting point, it has an arc shape in which the radius of the arc decreases from the second portion R2 to the first portion R1, and the radius of the arc increases from the first portion R1 to the third portion R3. is doing.

The lip 53 has a convex curved surface having a predetermined radius r4 from a lower end portion 531 (first upper end portion 511) to a third upper end portion 532 (second inner end portion 521). The upper cavity 52 has a curved concave shape with a predetermined radius r5 from the second bottom portion 522 to the standing wall region 525 . The second upper end portion 523 has a curved convex shape with a predetermined radius r6. The distance in the cylinder axial direction A between the center point of the radius r4 and the center point of the radius r5 is defined as the first distance Sv, and the distance in the radial direction B between the center point of the radius r5 and the center point of the radius r6 is defined as the second distance Sv. When the distance Sh is
r4+r5>Sv
r5+r6≦Sh
The values of the radii r4, r5, r6 are chosen so as to satisfy the relationship

A portion of the upper cavity 52 extending from the second bottom portion 522 to the upper end position R4 of the standing wall region 525 is formed by an approximately quarter arc with a radius r5. The upper end position R4 of the standing wall region 525 continues to the lower end position of the second upper end portion 523 which is approximately a quarter arc of radius r6. The upper end of the second upper end portion 523 continues to the squish area 55 . As a result of such a curved surface shape, the lower portion of the standing wall region 525 is located inside in the radial direction B with respect to the upper end position R4 of the standing wall region 525 . That is, in the standing wall region 525 , there is no portion hollowed outward in the radial direction B like the radial recess portion 514 of the lower cavity 51 . As will be described in detail later, the reason why the standing wall region 525 has such an arc shape is that, in cooperation with the egg-shaped shape of the lower cavity 51, the air-fuel mixture returns to the inside of the combustion chamber 6 in the radial direction B. This is because the space outside the standing wall region 525 in the radial direction B (squish space) is also effectively used for combustion.

[Control configuration]
Next, the control configuration of the diesel engine system will be described with reference to the block diagram of FIG. The diesel engine system of this embodiment is centrally controlled by a processor 70 (engine control device). The processor 70 is composed of a CPU, ROM, 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 has an accelerator opening sensor SN10 that detects the accelerator opening (the amount of depression of the accelerator), an atmospheric pressure sensor SN11 that measures the atmospheric pressure of the vehicle's running environment, and an outside air temperature sensor SN12 for measuring the air temperature of the environment in which the vehicle runs.

The processor 70 controls the aforementioned crank angle sensor SN1, water temperature sensor SN2, airflow sensor SN3, intake air temperature sensor SN4, intake pressure sensor SN5, intake _O2 sensor SN6, injection pressure sensor SN7, exhaust _O2 sensor SN8, differential pressure sensor SN9. , an accelerator position sensor SN10, an atmospheric pressure sensor SN11, and an outside air temperature sensor SN12. Information detected by these sensors SN1 to SN12, that is, crank angle, engine speed, engine water temperature, intake flow rate, intake air temperature, intake pressure, intake oxygen concentration, injection pressure of injector 15, exhaust oxygen concentration, accelerator opening , outside temperature, atmospheric pressure, etc. are sequentially input to the processor 70 .

The processor 70 controls each section of the engine while executing various judgments 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, the shift hydraulic solenoid 80, the control circuit for the motor 82 and the battery 83, and the like. Control signals are output to each of these devices based on the above.

By executing a predetermined program, the processor 70 functionally includes a vehicle speed detection unit 71, a target torque setting unit 72, a fuel injection control unit 73 that controls the operation of the injector 15, a remaining battery level calculation unit 77, a motor It operates to have a control unit 78 and a storage unit 79 .

The vehicle speed detector 71 detects the vehicle speed of the vehicle in which the engine body 1 is mounted. In this embodiment, the vehicle speed detection unit 71 detects the vehicle speed based on the operating state of the shift hydraulic solenoid 80 . A transmission hydraulic solenoid 80 is a solenoid for automatically switching gears of a transmission 81 ( FIG. 1 ) connected to the output shaft of the engine body 1 . The vehicle speed detection unit 71 determines at least whether the vehicle is running at a low speed or a high speed from the gear set by the shift hydraulic solenoid 80 . For example, if the transmission 81 is a 6-speed automatic transmission, the 1st to 3rd stages are defined as low speed gears, and the 4th to 6th stages are defined as high speed gears. If it is selected, it can be determined as "high speed".

The target torque setting unit 72 sets the target torque of the engine according to the operating conditions. Specifically, the target torque setting unit 72 sets the target torque of the engine based on the accelerator opening detected by the accelerator opening sensor SN10. Further, when the motor 82 is charging the battery 83, the target torque setting unit 72 adds the motor resistance when the motor 82 generates power to set the target torque.

The fuel injection control section 73 controls the fuel injection operation of the injector 15 . As will be described in detail later, the fuel injection control unit 73 of the present embodiment is configured such that, in each cycle in a specific operating region, the injector 15 is injected with fuel during the compression stroke, and near the top dead center of the compression stroke. A main injection that initiates injection and completes injection during the expansion stroke is performed. The fuel injection control unit 73 adjusts the injection amount of fuel to be injected from the injector 15 per cycle so as to achieve the target torque set by the target torque setting unit 72 (the target torque based on the accelerator depression amount and the motor resistance). set. The fuel injection control unit 73 operates to functionally include an operating state determination unit 74, an injection pattern selection unit 75, and a correction unit 76 by executing a predetermined program.

Based on the values detected by the sensors SN1 to SN12, the operating state determination unit 74 determines the engine speed, engine load, engine water and oil temperature, outside air temperature, intake air temperature, intake air pressure, oxygen concentration, and the degree of opening of the EGR valve 45. and the like to determine the operating state of the engine body 1 and the like.

The injection pattern selector 75 reads out an injection pattern preset for each target injection amount (combination of engine speed and load), and sets a fuel injection pattern according to the target injection amount. In the present embodiment, the injection pattern selection unit 75 operates when the vehicle speed detection unit 71 detects that the vehicle is running at high speed in a partial operation area (second area K2 in FIG. 7) of the specific operation area. control is performed to switch the fuel injection pattern depending on whether or not the motor resistance of the motor 82 is added to the target torque. Further, the injection timings of the first stage injection and the main injection are set so that the pressure waves generated due to combustion by these injections cancel each other out. These will be detailed later.

The correction unit 76 corrects the first stage injection timing set by the injection pattern selection unit 75 in accordance with fluctuations in combustion environment factors. That is, the correcting unit 76 corrects the difference between the timing of the occurrence of the heat release rate peak when the first stage injection is executed at the preset injection timing and the timing of the occurrence of the heat release rate peak considering the combustion environment factors. The fuel injection timing is corrected so as to eliminate the problem.

The remaining battery capacity calculator 77 performs processing for calculating the remaining charge capacity of the battery 83 . Furthermore, the remaining battery capacity calculation unit 77 outputs a signal indicating a charge request when the remaining charge capacity of the battery 83 falls below a predetermined threshold.

A motor control unit 78 controls the operation of the motor 82 . Specifically, the motor control unit 78 causes the motor 82 to perform the above-described engine assist operation or charging operation for the battery 83 . The motor control unit 78 supplies electric power from the battery 83 to the motor 82 and applies motor torque to the output shaft of the engine body 1 during the engine assist operation. During the charging operation, the motor control unit 78 operates the motor 82 as a power generator and supplies power generated by the motor 82 to the battery 83 . When a charge request signal is output from the remaining battery capacity calculator 77, the charging operation is executed. Upon receiving the charging request, the motor control unit 78 turns off the power supply path from the battery 83 to the motor 82 and turns on the charging path from the motor 82 to the battery 83 , and sets the target torque setting unit 72 to the motor resistance. output additional instructions.

The storage unit 79 stores various injection patterns that the injection pattern selection unit 75 refers to when setting the injection pattern. The storage unit 79 also stores various programs, various set values, an operation map shown in FIG. 7, and the like.

[Operation map and injection pattern]
FIG. 7 is a diagram showing an operation map of the engine body 1. As shown in FIG. The operation map includes a specific region K which is a low to medium speed range and is set near a light to medium load region, and a non-specific region N other than the specific region K. The specific region K is an operating region where quiet running with suppressed combustion noise is desired. When this specific region K is met, the fuel injection control unit 73 causes the injector 15 to perform first-stage injection to inject fuel at least during the compression stroke, and to start injection near the top dead center of the compression stroke and complete injection during the expansion stroke. Multi-stage injection combustion is executed. When it falls under the non-specific region N, the fuel injection control unit 73 causes the injector 15 to execute an injection mode in which, for example, general diffusion combustion is performed. Of course, in the non-specific region N, an injection mode that realizes general diffusion combustion and different combustion may be adopted.

In the specific area K, a first area K1 and a second area K2, which is a partial area on the low load side, are set. In the second region K2, the fuel injection control unit 73 performs control to change the injection amount ratio of the first stage injection and the main injection of the multi-stage injection according to the vehicle speed of the vehicle. As a basic setting, the fuel injection control unit 73 sets the injection amount of the first stage injection to be higher than the injection amount of the main injection when the vehicle speed detection unit 71 detects a vehicle speed (high-speed running) faster than a predetermined vehicle speed. Executes a high-speed injection pattern that sets a large number of On the other hand, when the vehicle speed detection unit 71 detects a vehicle speed lower than the predetermined vehicle speed (low speed running), the fuel injection control unit 73 sets the injection amount of the first stage injection to be smaller than the injection amount of the main injection. The injection pattern for low speed (second injection pattern) is executed. The basic setting does not change the total injection quantity per cycle.

In addition, in the second region K2, the fuel injection control unit 73 is controlled when the vehicle speed detection unit 71 detects that the vehicle is running at high speed (running at a vehicle speed exceeding the first predetermined value). , the injection pattern is switched depending on whether or not the motor resistance of the motor 82 is added. Referring to FIG. 7, it is assumed that the operating point a1 in the second area K2 is the operating point in which the motor resistance is not applied. The load in this case is determined only by the amount of depression of the accelerator. When motor resistance is added to this state, the load increases and the operating point shifts from a1 to a2. In other words, even though the driver does not change the accelerator depression amount, the engine speed cannot be maintained unless the engine load is increased (the total fuel injection amount per cycle is increased) in order to cope with the superimposition of the motor resistance. state.

Assuming that such an event occurs, when high-speed running is performed in the second region K2, the fuel injection control unit 73 controls the fuel injection control unit 73 when the motor control unit 78 does not issue an instruction to add motor resistance ( At the operating point a1), a high-speed injection pattern (first injection pattern) is executed in which the injection amount of the first stage injection is set larger than the injection amount of the main injection, as in the basic setting described above. On the other hand, when the motor control unit 78 issues an instruction to add motor resistance (operation point a2), the fuel injection control unit 73 changes the above-described basic settings to increase the injection amount of the first stage injection. A low-speed injection pattern (second injection pattern) that is set to be smaller than the injection amount of the main injection is executed.

FIG. 8 is a time chart showing an example of fuel injection timing and heat generation rate when the low-speed injection pattern is executed. The low-speed injection pattern is a basic injection pattern that the fuel injection control unit 73 causes the injector 15 to execute in the specific region K, is executed unconditionally in the first region K1, and is executed in the second region K2 when the vehicle Executed when adding resistance. The low-speed injection pattern includes a first-stage injection P1, a second-stage pre-injection Pa (one of the second-stage injections), and a third-stage pre-injection Pb (one of the second-stage injections), which are sequentially executed toward the advance side. one), a main injection M1, a first-stage after-injection AF1 and a second-stage after-injection AF2.

The first stage injection P1 is the earliest injection in one cycle, and is an injection that injects fuel during the above-described compression stroke. The fuel injection timing of the first stage injection P1 is set so that the injected fuel spray is directed toward the lip 53 of the cavity 5C. The main injection M1 is an injection that starts the injection near the compression top dead center and completes the injection during the expansion stroke. The second-stage pre-injection Pa and the third-stage pre-injection Pb are injections executed between the first-stage injection P1 and the main injection M1, and in this embodiment, both are executed during the compression stroke. ing. Both the first-stage after-injection AF1 and the second-stage after-injection AF2 are injections performed after the main injection M1. In this way, in the low-speed injection pattern, fuel injection is performed in multiple stages during the period from about -26 degrees to about 17 degrees of the crank angle. Although FIG. 8 shows an example in which pre-injection and after-injection are performed in two stages, each injection may be performed in a single injection or in three or more stages.

The injection amount of the first stage injection P1 is set smaller than the injection amount of the main injection M1. The injection amounts of the second-stage and third-stage pre-injections Pa and Pb and the first-stage and second-stage after-injections AF1 and AF2 are set to be larger than the first-stage injection P1 but smaller than the injection amount of the main injection M1. ing. Mainly, the injection amount of the main injection M1 is increased or decreased according to the increase or decrease of the load.

Combustion when the low-speed injection pattern is executed is generally diffuse combustion. The upper part of FIG. 8 shows the heat release rate characteristic H1 when the low-speed injection pattern is executed. The heat release rate characteristic H1 has a mountain shape with one peak H1P. The height of this peak H1P is set lower than when the high-speed injection pattern described below is executed. Therefore, combustion noise is suppressed.

Since the fuel injected in the first stage injection P1 is injected at a relatively early stage, combustion by premixed compression ignition (hereinafter referred to as PCI (Premixed Compression Ignition) combustion) occurs. However, since the fuel injection amount of the first stage injection P1 is small, the heat release rate characteristic H1 does not show a sharp rise. The second- and third-stage pre-injections Pa and Pb are injections performed before the main injection M1 in order to control the heat release rate characteristic H1.

The fuel injected by the main injection M1 generally diffusely burns with the combustion by the first-stage injection P1 and the second- and third-stage pre-injections Pa and Pb as fire sources. Therefore, the peak H1P occurrence timing of the heat release rate characteristic H1 substantially coincides with the injection timing of the main injection M1. The first-stage injection P1 and the second- and third-stage pre-injections Pa and Pb ensure an appropriate amount of heat for pre-combustion (PCI combustion) that assists the ignition of the fuel in the main injection M1. The injection timing and the injection amount are set so as to obtain the heat release rate characteristic H1 of . The first-stage and second-stage after-injections AF1 and AF2 are injections that are executed for the purpose of completely combusting the fuel so as not to generate soot.

Next, FIG. 9 is a time chart showing an example of fuel injection timing and heat release rate when the high-speed injection pattern is executed. The high-speed injection pattern is executed in the second region K2 when the vehicle is running at high speed. However, as described above, even during high-speed running in the second region K2, when motor resistance is applied, the low-speed injection pattern is selected instead of the high-speed injection pattern. . The high-speed injection pattern has a leading stage injection P2, a main injection M2, and a middle stage injection Pm.

The first stage injection P2 is the earliest injection in one cycle, and is an injection that injects fuel during the above-described compression stroke. The first stage injection P2 is intended for PCI combustion of the injected fuel, and is executed in the latter half of the compression stroke when the in-cylinder pressure and the in-cylinder temperature rise to some extent. The fuel injection timing is set so that the injector 15 can direct the fuel toward the lip 53 and inject fuel in the first stage injection P2 of the high-speed injection pattern as well.

The main injection M2 is an injection that starts the injection near the compression top dead center and completes the injection during the expansion stroke. The main injection M2 is started during the PCI combustion of the fuel injected in the first stage injection P2. In other words, the main injection M2 is an injection designed to diffusely burn the injected fuel using the heat of PCI combustion. FIG. 9 shows an example in which the main injection M2 is started at a timing that is slightly retarded from TDC. In terms of the positional relationship with the cavity 5</b>C, the main injection M<b>2 is set at an injection timing at which the injector 15 can inject fuel toward the upper cavity 52 . Contrary to the case of the low-speed injection pattern, the injection amount of the main injection M2 is set smaller than the injection amount of the front stage injection P2.

The intermediate injection Pm is an injection that is performed at a timing between the initial injection P2 and the main injection M2. The fuel injected in the middle injection Pm is intended to be burned between the combustion of the first injection P2 and the main injection M2. The middle-stage injection Pm is also generally diffuse combustion. The fuel injection amount (injection period) of the intermediate injection Pm is set to a smaller injection amount (shorter injection period) than both of the initial injection P2 and the main injection M2.

The upper part of FIG. 9 shows the heat release rate characteristic H2 when the high-speed injection pattern is executed. The heat release rate characteristic H2 is composed of a pre-combustion portion HA, which is a peak caused by PCI combustion accompanying the first injection P2, a post-burning portion HB, which is a peak caused by diffusion combustion accompanying the main injection M2, and both combustion portions HA. , and an intermediate combustion portion HC intermediate of HB. That is, in the heat release rate characteristic H2, peaks of the heat release rate occur in two stages due to the respective combustions of the first injection P2 and the main injection M2 that are performed separately in terms of time. Since the first stage injection P2 is an injection with a relatively large injection amount and performs PCI combustion, the heat release rate characteristic H2 exhibits a sharp rise, and the peak value is also higher than the heat release rate characteristic H1 described above. Therefore, combustion noise increases. Note that the intermediate injection Pm is an injection for suppressing the peak of the heat release rate caused by each combustion of the first injection P2 and the main injection M2, in other words, the injection for suppressing the drop in the heat release rate in the intermediate combustion portion HC. be.

[About switching the injection pattern]
FIG. 10 is a time chart showing injection pattern switching control according to the addition of motor resistance, which is performed during high-speed running in the second region K2. Until the time Tx, high-speed driving (vehicle speed exceeding the first predetermined value) is performed under the accelerator depression amount and the engine load corresponding to the driving point in the second region K2 in a state where the motor resistance is not applied. Suppose you are In this case, the fuel injection control unit 73 selects the high-speed injection pattern (first injection pattern) shown in FIG.

At time Tx, for example, the motor control unit 78 issues an instruction to add motor resistance (motor resistance ON) in response to the remaining battery level calculation unit 77 outputting a charge request. It is assumed that there is no change in the accelerator depression amount. In this case, the motor resistance is superimposed on the required torque corresponding to the accelerator depression amount, so the engine load increases. Correspondingly, the total injection of fuel is also increased to take up the additional torque of the motor resistance. Thereby, the vehicle speed is maintained. Then, the fuel injection control unit 73 changes the fuel injection pattern from the high speed injection pattern to the low speed injection pattern (second injection pattern) shown in FIG. Combustion noise is thereby suppressed.

11A and 11B are time charts for comparing low-speed injection patterns and high-speed injection patterns. FIG. 11A shows an example of a low-speed injection pattern, and FIG. 11B shows an example of a high-speed injection pattern. ing. The total injection quantity in the low speed injection pattern and the total injection quantity in the high speed injection pattern are the same when the engine speed and load are the same.

First, it is assumed that the motor control unit 78 does not issue an instruction to add motor resistance, that is, the fuel injection control unit 73 performs fuel injection control based only on the amount of depression of the accelerator. In this case, when the vehicle is driven in the second region K2 of the driving map shown in FIG. If the vehicle is traveling at high speed, the injectors 15 are caused to perform fuel injection according to the high-speed injection pattern shown in FIG. 11(B). When the low-speed injection pattern is executed, the injection amount of the first stage injection P1 is set smaller than the injection amount of the main injection M1. As a result, the heat release rate characteristic H1 associated with combustion does not show a steep change (FIG. 8), and the peak H1P of the heat release rate appears on the retarded side compared to when the high-speed injection pattern is executed. Therefore, combustion noise can be suppressed when the low-speed injection pattern is executed, in which running noise such as wind noise is reduced due to low-speed running.

In contrast, when the high-speed injection pattern is executed, the injection amount of the first stage injection P2 is set larger than the injection amount of the main injection M2. Therefore, the peak of the heat release rate due to the front-stage combustion portion HA due to the front-stage injection P2 can appear near the compression top dead center (FIG. 9). In other words, the PCI combustion can be realized in the first stage injection P2, and the fuel consumption performance can be improved. Here, when the high-speed injection pattern is executed, the vehicle speed is high and the running noise of the vehicle increases. Therefore, although the PCI combustion increases the combustion noise, the running noise has the effect of drowning out the combustion noise. It is difficult to feel discomfort. In this way, by performing PCI combustion only under driving conditions where noise reduction is not required, fuel consumption performance can be improved without making the driver aware of the magnitude of combustion noise.

Next, it is assumed that the motor control unit 78 issues an instruction to add motor resistance, that is, the fuel injection control unit 73 performs fuel injection control based on the amount of depression of the accelerator and the motor resistance. In this case, even if the vehicle speed detector 71 detects that the vehicle is traveling at high speed within the second region K2, the low speed injection pattern is selected. As shown in the chart of FIG. 10, when the motor resistance of the motor 82 is added, the engine load also increases, so the fuel injection control unit 73 must perform control to increase the fuel injection amount in order to maintain the vehicle speed. . In this situation, if the high-speed injection pattern is continued, the combustion noise also increases. Since the increase in the engine load here is not based on the driver's accelerator work, the driver may feel uncomfortable when the combustion noise increases. Therefore, in such a situation, the fuel injection control unit 73 selects the low speed injection pattern instead of the high speed injection pattern. As a result, combustion noise can be suppressed when motor resistance is added.

Here, when the vehicle 100 is traveling at a higher speed (very high speed traveling) at a driving point within the second region K2, it is possible to maintain the high speed injection pattern without switching to the low speed injection pattern. desirable. For example, a vehicle speed that exceeds a predetermined first predetermined value is defined as "high speed", and a vehicle speed that exceeds a second predetermined value that is greater than the first predetermined value by a predetermined value is defined as "very high speed". back. When the vehicle speed detection unit 71 detects a vehicle speed corresponding to "high speed" at the driving point within the second region K2, the fuel injection control unit 73 instructs the motor control unit 78 to add motor resistance. is issued, the injector 15 is caused to execute the injection pattern for high speed.

When the vehicle 100 is traveling at a high speed at a considerably high speed, the traveling noise also becomes considerably large enough to drown out the combustion noise. In such a case, the driver does not feel uncomfortable, so the high-speed injection pattern that exhibits excellent fuel efficiency is maintained without changing to the low-speed injection pattern. Thereby, the fuel consumption performance of the vehicle 100 can be improved.

[Desired injection pattern]
As is clear from the comparison between FIGS. 11A and 11B, the fuel injection control unit 73 causes the leading injection P2 of the high-speed injection pattern to be delayed relative to the leading injection P1 of the low-speed injection pattern. let it run. That is, the start timing of the first injection P2 is set at a timing delayed by ΔCA from the start timing of the first injection P1. Due to the retardation of ΔCA, the front stage injection P2 is executed with a large amount of injection while the pressure in the combustion chamber is increased.

Further, the fuel injection control unit 73 sets the fuel injection timing so that the fuel injection by the first stage injections P1 and P2 is directed to the lip 53 of the cavity 5C in both the high speed injection pattern and the low speed injection pattern. Although the low-speed first-stage injection P1 is advanced by ΔCA from the high-speed first-stage injection P2, the injection amount is small and the penetration is weak. . Therefore, the fuel spray is distributed from the lip 53 to the lower cavity 51 and the upper cavity 52, effectively utilizing the air in the combustion chamber 6 to form a homogeneous and thin air-fuel mixture and suppressing the generation of soot. be able to.

The fuel injection control unit 73 performs the second-stage pre-injection Pa and the third-stage pre-injection Pb (at least once) at the timing between the first stage injection P1 and the main injection M1 when the injection of the injection pattern for low speed is executed. an example of the second stage injection) is executed. Furthermore, the fuel injection control unit 73 sets the injection amount of each injection so that the injection amount increases in order of the first stage injection P1, the second stage pre-injection Pa, the third stage pre-injection Pb, and the main injection M1.

As shown in FIG. 11A, in the low-speed injection pattern, when the injection amount of the first stage injection P1 is f1 and the injection amount of the main injection M1 is f4, f1<f4 is set as described above. . In addition to this, in the present embodiment, when the injection amount of the second-stage pre-injection Pa is f2 and the injection amount of the third-stage pre-injection Pb is f3, the injection amount is gradually increased toward the retarded side. , f1<f2<f3<f4. By gradually increasing the fuel injection amount in this way, it is possible to suppress a sharp increase in the heat release rate in the combustion by the main injection M1, and to further reduce the combustion noise during low-speed running. In addition, since the total injection amount is constant and the second and third stage pre-injections Pa and Pb are added, the penetration of each injection is suppressed, making it easier to suppress the adhesion of fuel to the cylinder wall surface.

[Suppression of combustion noise in high-speed injection pattern]
As described above, when the high-speed injection pattern intended for PCI combustion is executed, the combustion noise can be made less conspicuous by the running noise, but it is desirable to suppress the combustion noise as much as possible. In view of this point, in the present embodiment, measures are taken to suppress combustion noise in the high-speed injection pattern. Specifically, the settings are noise cancellation and mid-stage injection.

<Noise cancellation>
In the high-speed injection pattern, the initial stage injection P2 and the main injection M2 are executed so that pressure waves generated due to combustion by these injections cancel each other out. That is, the fuel injection control unit 73 causes the injector 15 to perform the first stage injection P2 and the main injection M2 so that each combustion occurs at a timing at which the combustion noise caused by each injection cancels out each other. This point will be described with reference to FIG.

FIG. 12A shows a heat release rate characteristic H0 having two stages of heat release rate peaks, like the heat release rate characteristic H2 shown in FIG. The heat release rate characteristic H0 shown here is a characteristic when the intermediate injection Pm is not executed, and the values of the front peak HAp of the front combustion portion HA and the rear peak HBp of the rear combustion portion HB are increased accordingly. In other words, the degree of drop in the heat release rate in the intermediate combustion portion HC is large.

The interval In (peak interval) between the time at which the front peak HAp occurs and the time at which the rear peak HBp occurs has a great influence on the suppression of combustion noise. Assuming that the interval In is the interval at which the amplitude of the pressure wave (sound wave) caused by the combustion in the pre-burning portion HA and the amplitude of the pressure wave caused by the combustion in the post-burning portion HB cancel each other out, the frequency effect will It is possible to suppress the pressure wave (combustion noise) to be emitted.

FIG. 12B is a schematic diagram for explaining the effect of canceling pressure waves. FIG. 12B shows the front pressure wave EAw (first pressure wave) generated due to the combustion of the front combustion portion HA by the front injection P2 and the combustion of the rear combustion portion HB due to the main injection M2. A post-stage pressure wave EBw (second pressure wave) generated at the same time is shown. Here, for the sake of simplification, it is assumed that the peak heights of the front peak HAp and the rear peak HBp are the same, and the amplitude of the front pressure wave EAw and the amplitude of the rear pressure wave EBw are the same.

Here, in order to cancel both pressure waves, the former pressure wave EAw and the latter pressure wave EBw should appear with a shift of 1/2 cycle from each other. That is, the pressure wave interval Fin until the rear pressure wave EBw occurs following the front pressure wave EAw should be set to 1/2 times the cycle of both pressure waves EAw and EBw. In this case, the front pressure wave EAw and the rear pressure wave EBw have opposite phases and interfere with each other so as to cancel each other out, and the amplitude of the composite wave EM becomes zero. That is, the combustion noise is canceled by the cancellation effect. Therefore, by executing the front injection P2 and the main injection M2 so that the rear pressure wave EBw is generated with a delay of 1/2 cycle with respect to the front pressure wave EAw, combustion noise can be suppressed.

<Middle stage injection>
Combustion noise can theoretically be suppressed by the above noise cancellation. However, while the combustion by the first injection P2 is PCI combustion, the combustion by the main injection M2 is diffusive combustion, and the combustion modes of the two are different. For this reason, the rise characteristics of the heat release rates of the two combustions are different, and as a result, the frequency component of the front pressure wave EAw and the frequency component of the rear pressure wave EBw are naturally different. Even if the representative frequency components of both pressure waves EAw and EBw are adjusted to be in opposite phase, the other frequency components will not be in opposite phase, so both pressure waves EAw and EBw are sufficiently offset. I can't let you. Therefore, even if the first stage injection P2 and the main injection M2 are executed aiming at a 1/2 cycle shift between the two pressure waves EAw and EBw, it is not possible to sufficiently reduce the combustion noise.

In the present embodiment, the above problem is alleviated by executing the middle stage injection Pm. The fuel injection control unit 73 reduces a part of the injection quantity assigned to each of the first stage injection P2 and the main injection M2 while maintaining the injection quantity ratio between the two, and assigns the injection quantity corresponding to this decrease to the middle stage injection. Set injection Pm. That is, while aiming for a 1/2 cycle shift between the pressure waves EAw and EBw, the intermediate injection Pm reduces the front and rear peaks HAp and HBp of the front and rear combustion portions HA and HB in the heat release rate characteristic H0. I am letting The injection amounts of the first injection P2 and the main injection M2 can be reduced by the amount of the intermediate injection Pm. It can be suppressed.

FIG. 13 shows the heat release rate characteristic H0 (solid line) when only the first injection P2 and the main injection M2 are performed, and the heat release rate characteristic H0 (solid line) when the middle injection Pm is performed in addition to the first injection P2 and the main injection M2. A heat release rate characteristic Hx (dotted line; corresponding to the heat release rate characteristic H2 in FIG. 9) is shown. As shown in FIG. 13, the execution of the intermediate injection Pm causes the front peak HAp of the front-stage combustion portion HA to decrease according to the decrease in the front-stage injection P2, and the rear-stage peak HAp to decrease according to the decrease in the main injection M2. The post-stage peak HBp of the combustion portion HB also decreases. Since the peaks HAp and HBp of the heat release rate can be suppressed in this way, the magnitudes of the pressure waves EAw and EBw generated due to the combustion of the first stage injection P2 and the main injection M2 can be suppressed. can be done. As the amplitudes of the pressure waves EAw and EBw become smaller, the combustion noise also becomes smaller. Therefore, in combination with the injection mode in which the pressure waves EAw and EBw cancel each other, combustion noise can be effectively suppressed.

On the other hand, the heat release rate of the intermediate combustion portion HC is increasing. Since the intermediate injection Pm is executed between the first injection P2 and the main injection M2, the combustion by the intermediate injection Pm fills the valley between the front peak HAp and the rear peak HBp. Therefore, the heat release rate of the intermediate combustion portion HC is raised. Therefore, unlike the after-injection performed on the retarded side of the main injection M, the combustion by the middle-stage injection Pm directly contributes to the engine torque and does not reduce the thermal efficiency. Moreover, since the intermediate injection Pm is executed with a smaller amount of injection than the initial injection P2 and the main injection M2, it is possible to complete combustion before the main injection M2, which affects the combustion by the main injection M2. can be avoided. That is, the combustion mode of the main injection M2, which is set so that the pressure waves EAw and EBw cancel each other, can be maintained, so that the effect of canceling out the combustion noise can be prevented from being lowered.

[Utilization of oxygen in the combustion chamber by high-speed injection pattern]
The ideal mode of combustion in the combustion chamber 6 is to use up all the oxygen present in the combustion chamber 6 . As in the present embodiment, in the combustion chamber 6 whose bottom surface is defined by the crown surface 50 having the lower and upper cavities 52, 52, the above-described high-speed injection pattern of the first stage injection P2, the middle stage injection Pm and the main injection M2 are executed. Oxygen existing in the combustion chamber 6 can be effectively utilized by setting the temperature. In this embodiment, in order to effectively utilize the oxygen in the combustion chamber 6, the combustion regions in each injection P2, Pm, M2 are separated spatially and temporally. This point will be illustrated below with reference to FIGS. 14 to 17. FIG.

<Regarding the first stage injection>
FIG. 14 is a diagram showing the state of fuel injection by the first stage injection P2 into the cavity 5C by the injector 15 and the flow of the air-fuel mixture after the injection. FIG. 14 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 15P1 injected from the injector 15, and the air-fuel mixture after injection. Arrows F11, F12, F13, F21, F22, and F23 are shown to schematically represent the flow.

The injector 15 has a nozzle 151 arranged to protrude downward into the combustion chamber 6 from the combustion chamber ceiling surface 6U (the lower surface of the cylinder head 4). The nozzle 151 has injection holes 152 for injecting fuel into the combustion chamber 6 . Although one injection hole 152 is shown in FIG. 14, a plurality of injection holes 152 are actually arranged in the circumferential direction of the nozzle 151 at equal pitches. The fuel injected from the injection hole 152 is injected along the injection axis AX in the figure. The injected fuel diffuses at a spray angle θ. FIG. 14 shows an upper diffusion axis AX1 indicating upward diffusion with respect to the ejection axis AX, and a lower diffusion axis AX2 indicating downward diffusion. The spray angle θ is the angle between the upper diffusion axis AX1 and the lower diffusion axis AX2.

As described above, in the first stage injection P2, the injector 15 injects fuel toward the lip 53 of the cavity 5C. The fuel 15P1 injected from the injection hole 152 is mixed with the air in the combustion chamber 6 to form an air-fuel mixture, and blows against the lip 53. As shown in FIG. The fuel 15P1 that has collided with the lip 53 is then spatially directed toward the lower cavity 51 (downward) (arrow F11) and toward the upper cavity 52 (upward) (arrow F21). separated. That is, the fuel 15P1 injected toward the central portion 533 of the lip 53 is separated into upper and lower portions, and then mixed with the air existing in the cavities 51 and 52, respectively, along the surface shapes of these cavities 51 and 52. flow.

Specifically, the air-fuel mixture flowing in the direction of arrow F11 (downward) enters from the lower end 531 of the lip 53 into the radial recess 514 of the lower cavity 51 and flows downward. After that, the air-fuel mixture changes its flow direction from downward to inward in the radial direction B due to the curved shape of the radial recess 514, and as indicated by the arrow F12, forms the bottom surface of the lower cavity 51 having the first bottom 512. imitate and flow. At this time, the air-fuel mixture is mixed with the air in the lower cavity 51 to reduce its concentration. Due to the existence of the peak portion 54, the bottom surface of the lower cavity 51 has a shape that rises toward the center in the radial direction. Therefore, the air-fuel mixture flowing in the direction of arrow F12 is lifted upward, and finally flows radially outward from the combustion chamber ceiling surface 6U as indicated by arrow F13. Even during such flow, the air-fuel mixture mixes with the air remaining in the combustion chamber 6 to become a homogeneous and lean air-fuel mixture.

On the other hand, the air-fuel mixture flowing in the direction of arrow F21 (upward) enters the descending plane 524 of the upper cavity 52 from the third upper end portion 532 of the lip 53 and travels obliquely downward along the inclination of the descending plane 524 . Then, the air-fuel mixture reaches the second bottom portion 522 as indicated by an arrow F22. Here, the descending plane 524 is a plane inclined along the injection axis AX (FIG. 4). Therefore, the air-fuel mixture can smoothly flow radially outward. That is, the air-fuel mixture can reach a deep position radially outside of the combustion chamber 6 due to the presence of the descending plane 524 and the presence of the second bottom portion 522 below which the third upper end portion 532 of the lip 53 is also located. can.

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 from the combustion chamber ceiling surface 6U. During the flow indicated by the arrow F22, the air-fuel mixture mixes with the air in the upper cavity 52 to become a homogeneous and thin air-fuel mixture. Here, the presence of the standing wall region 525 extending substantially vertically outside the second bottom portion 522 in the radial direction prevents the injected fuel from reaching the inner peripheral wall of the cylinder 2 . In other words, the formation of the second bottom portion 522 allows the air-fuel mixture to flow to the vicinity of the radially outer side of the combustion chamber 6 , but the presence of the standing wall region 525 prevents the air-fuel mixture from interfering with the inner peripheral wall of the cylinder 2 . Therefore, it is possible to suppress the occurrence of cold loss due to the interference.

Here, the standing wall region 525 has a shape in which the lower portion is located inside in the radial direction B with respect to the upper end position. Therefore, the flow indicated by the arrow F22 is not excessively strong, and the air-fuel mixture can be prevented from returning too much to the inside in the radial direction B. If the flow indicated by the arrow F22 is too strong, the partially combusted air-fuel mixture collides with the newly injected fuel before it sufficiently diffuses, impeding homogeneous combustion and generating soot. However, the standing wall region 525 of the present embodiment does not have a shape that is scooped outward in the radial direction, so that the flow in the arrow F22 is suppressed, and the flow directed outward in the radial direction B indicated by the arrow F23 is also generated. do. In particular, in the latter stage of combustion, the air may be pulled by a reverse squish flow, and the flow indicated by arrow F23 is likely to occur. Therefore, the space above the squish area 55 can also be effectively used for combustion.

FIG. 15 is a cross-sectional view of the combustion chamber 6, showing the main occurrence regions of PCI combustion due to the first stage injection P2. As described above, in the first stage injection P2, the fuel 15P1 injected along the injection axis AX toward the lip 53 collides with the lip 53 and is spatially separated into the spaces of the lower and upper cavities 51 and 52. Each mixes with the air (oxygen) present to form a mixture, leading to combustion. Therefore, the combustion caused by the first stage injection P2 occurs in the combustion area G1 existing in the space of the lower cavity 51 using oxygen and the combustion area G2 existing in the space of the upper cavity 52 using oxygen. Become. In this way, the PCI combustion by the first-stage injection P2 is performed after widely utilizing the spaces of the upper and lower cavities 51 and 52 to form a homogeneous and lean air-fuel mixture.

<About middle stage injection>
FIG. 16 is a cross-sectional view of the combustion chamber 6 showing the main areas where PCI combustion is generated by the intermediate injection Pm. In the intermediate injection Pm, a combustion area G3 is defined as a region near the center in the radial direction of the combustion chamber 6, which is not used for combustion by the first injection P2 and the main injection M2. Oxygen in the upper and lower cavities 51 and 52 is utilized in the first stage injection P2. On the other hand, in the main injection M2, oxygen remaining in the lower cavity 51 is utilized. Both of these combustions are combustions that occur in regions other than near the center in the radial direction of the combustion chamber 6 . On the other hand, in the intermediate injection Pm, the oxygen in the radially central region of the combustion chamber 6 is actively used to form an air-fuel mixture and burn it.

The middle-stage injection Pm is an injection that is executed in a shorter injection period (injection amount) than the first-stage injection P2 and the main injection M2, and has a small penetration. Therefore, the fuel 15P3 injected along the injection axis AX in the intermediate injection Pm becomes difficult to reach the lower and upper cavities 51 and 52, and is exclusively mixed with the air near the center in the radial direction of the combustion chamber 6. It forms a ki and creates a combustion area G3. By providing such a combustion area G3, the oxygen present in the combustion chamber 6 can be effectively used, and the generation of soot and the like can be suppressed. Further, since the intermediate injection Pm is executed at a timing between the first injection P2 and the main injection M2 to create the combustion area G3, the combustion by the intermediate injection Pm can contribute to the engine torque. .

<About main injection>
FIG. 17 is a cross-sectional view of the combustion chamber 6, showing the main areas where diffusion combustion is generated by the main injection M2. As the piston 5 rises, the fuel 15P2 injected along the injection axis AX in the main injection M2 executed near TDC goes to a position slightly below the lip 53, that is, toward the upper layer region of the lower cavity 51. . After hitting the upper layer region, the fuel 15P2 follows the shape of the bottom surface of the lower cavity 51 as indicated by an arrow F31, and then flows radially outward from the combustion chamber ceiling surface 6U as indicated by an arrow F32. Flow as you go.

The main injection M2 is performed after the fuel (air-fuel mixture) injected in the first-stage injection P2 enters the spaces between the upper and lower cavities 51 and 52 and is spatially separated, and then the space between the two separated air-fuel mixtures is injected. This is an injection that utilizes the air remaining in the gas to form a new air-fuel mixture to create a combustion area G4. That is, the fuel of the first stage injection P2 that was injected earlier enters each of the cavities 51 and 52 and mixes with the air in each space to form an air-fuel mixture, thereby generating combustion areas G1 and G2. (spatial separation).

Therefore, immediately before the main injection M2 is started, there is unused air (air that is not mixed with fuel) between the combustion areas G1 and G2. The egg-shaped shape of the lower cavity 51 contributes to the formation of such an unused air layer. The injected fuel of the main injection M2 takes the form of entering between the combustion areas G1, G2 and mixes with the virgin air to form a mixture. A combustion area G4 is formed by diffusive combustion by applying heat to this air-fuel mixture from the combustion areas G1 and G2 resulting from the preceding front-stage injection P2. This is the temporal separation of fuel injection.

As described above, according to the present embodiment, the injected fuel of the first stage injection P2 is spatially separated to utilize the oxygen in the lower and upper cavities 51 and 52 . Also, unused oxygen existing between the combustion areas G1 and G2 generated by the first stage injection P2 is utilized in the temporally separated injection of the main injection M2 to form a combustion area G4. Oxygen near the center in the radial direction of the combustion chamber 6, which is not utilized in the first stage injection P2 and the main injection M2, is utilized in the middle stage injection Pm set for the penetration (injection period), and the combustion area G3 is to form As a result, combustion effectively utilizing the oxygen present in the combustion chamber 6 can be realized, and generation of soot and the like can be suppressed.

[Control flow]
FIG. 18 is a flowchart showing an example of fuel injection control by the fuel injection control section 73 of the processor 70. As shown in FIG. The fuel injection control unit 73 receives information on the operating range of the vehicle (operating state of the engine body 1) from sensors SN1 to SN12 shown in FIG. environment information is acquired (step S1).

Subsequently, the driving state determination unit 74 identifies which region of the driving map shown in FIG. 7 the current driving point corresponds to from the information about the driving region acquired in step S1. The injection pattern selection unit 75 sets a preset fuel injection pattern and injection amount according to the specified operating range. First, the injection pattern selector 75 determines whether or not the operating region specified in step S1 belongs to the specified region K of the operating map of FIG. 7 (step S2).

If it belongs to the specific region K (YES in step S2), the injection pattern selector 75 subsequently determines whether or not the identified operating region belongs to the second region K2 (step S3). On the other hand, if it does not belong to the specific region K (NO in step S2), the injection pattern selector 75 selects an injection pattern set for the non-specific region N (step S4). For example, in step S4, the injection pattern selection unit 75 sets an injection pattern capable of performing general diffusion combustion.

In step S3, if it belongs to the second region K2 (YES in step S3), the injection pattern selection unit 75 subsequently refers to the vehicle speed detection result of the vehicle speed detection unit 71, and determines that the vehicle speed of the vehicle 100 is the predetermined number. It is determined whether or not the speed is equal to or higher than one predetermined value (step S5). On the other hand, if it does not belong to the second region K2 (NO in step S3), that is, if the specified operating region belongs to the first region K1, the injection pattern selector 75 selects the fuel injection pattern as the low-speed injection pattern (second injection pattern) (step S6).

In step S5, if the vehicle speed is equal to or greater than the first predetermined value (YES in step S5), the injection pattern selection unit 75 determines whether the remaining battery capacity calculation unit 77 is outputting a charge request signal for the battery 83, in other words, Then, it is determined whether or not the motor control unit 78 issues an instruction to add motor resistance (step S7). If the charging request signal is output (YES in step S7), the injection pattern selection unit 75 further refers to the vehicle speed detection result of the vehicle speed detection unit 71 to set the vehicle speed of the vehicle 100 to a predetermined second predetermined value. It is determined whether or not the speed is as follows (step S8). As described above, the second predetermined value is a threshold for distinguishing between "high speed", which is the vehicle speed exceeding the first predetermined value, and "high speed", which is the higher vehicle speed.

If the "high speed" is equal to or lower than the second predetermined value (YES in step S8), the injection pattern selector 75 sets the fuel injection pattern to the low speed injection pattern (second injection pattern) shown in FIG. step S9). As a result, combustion noise can be suppressed even when motor resistance is added.

On the other hand, if the charging request signal is not output in step S7 (NO in step S7), the motor resistance is not added and the engine load does not increase. , the high-speed injection pattern (first injection pattern) shown in FIG. 9 (step S10). Thereby, fuel consumption performance can be improved. Also, when the vehicle speed exceeds the second predetermined value in step S8 (NO in step S8), the combustion noise is sufficiently drowned out by the running noise even if the motor resistance is added. The pattern selector 75 sets the fuel injection pattern to the high speed injection pattern (step S10).

If any one of the injection patterns in steps S4, S6, S9, or S10 is set, the fuel injection control unit 73 causes the injector 15 to execute the fuel injection operation in accordance with the set injection pattern (step S11), Finish one cycle of processing.

[Modification]
Although the embodiment of the present invention has been described above, the present invention is not limited to this, and for example, the following modified embodiments can be adopted.

(1) In the above embodiment, the low-speed injection pattern (second injection pattern) includes the first-stage injection P1 and the main injection M1, as well as the second- and third-stage pre-injections Pa and Pb, and the first- and second-stage pre-injections Pa and Pb. An example in which stage after-injections AF1 and AF2 are executed is shown. The injection pattern for low speed should include at least the first stage injection P1 and the main injection M1 with a larger injection amount than the first stage injection P1, and one of the pre-injections Pa, Pb and the after-injections AF1, AF2. , or both may be omitted.

(2) Similarly, in the above-described embodiment, the middle injection Pm is executed as the high-speed injection pattern (first injection pattern) in addition to the first injection P2 and the main injection M2. The high-speed injection pattern may include at least the first stage injection P2 and the main injection M2 having a smaller injection amount than the first stage injection P2, and the middle stage injection Pm may be omitted. Alternatively, an after-injection may be added in which the middle-stage injection Pm is divided into a plurality of times.

(3) In the above embodiment, the cavity 5C of the piston 5 defining the bottom surface of the combustion chamber 6 has a two-step egg shape with the lower cavity 51 and the upper cavity 52 . The fuel injection control of the present invention can also be applied to the case where the cavity 5C has a concave shape other than the two-step egg shape.

1 engine body (compression ignition engine)
2 Cylinder 5 Piston 50 Crown 5C Cavity 51 Lower Cavity 52 Upper Cavity 53 Lip 6 Combustion Chamber 7 Crankshaft (Output Shaft)
15 injector (fuel injection valve)
70 processor (vehicle control device)
71 Vehicle speed detection unit 73 Fuel injection control unit 78 Motor control unit 82 Motor A Cylinder axial direction B Radial direction of combustion chamber P1, P2 First stage injection M1, M2 Main injection Pa, Pb Second stage, third stage pre-injection two-stage injection)
Pm Middle injection EAw, EBw Front pressure wave EAw (first pressure wave), rear pressure wave EBw (second pressure wave)

Claims (6)

An engine system including a compression ignition engine equipped with a fuel injection valve capable of injecting fuel into a combustion chamber in multiple stages from a compression stroke to an expansion stroke, and a motor capable of generating power coupled to an output shaft of the compression ignition engine. A control device for a vehicle equipped with
a fuel injection control unit that controls the operation of the fuel injection valve based on the depression amount of the accelerator and the motor resistance during power generation of the motor;
a motor control unit that controls the operation of the motor;
A vehicle speed detection unit that detects the vehicle speed of the vehicle,
The fuel injection control unit is
causing the fuel injection valve to perform first stage injection for injecting fuel during a compression stroke and main injection for starting injection near compression top dead center and completing injection during an expansion stroke;
When the vehicle speed detection unit detects that the vehicle speed exceeds the first predetermined value and the motor control unit does not issue an instruction to add motor resistance, the injection of the first stage injection While executing the first injection pattern in which the injection amount is set larger than the injection amount of the main injection, when the motor control unit issues an instruction to add motor resistance, the injection amount of the first stage injection is set to the above executing a second injection pattern that is set to be smaller than the injection amount of the main injection;
A vehicle control device characterized by: In the vehicle control device according to claim 1,
The fuel injection control unit is
At least one second-stage injection is executed between the first-stage injection and the main injection when the injection of the second injection pattern is executed, and
A control device for a vehicle that sets the injection amount so as to increase in the order of the first stage injection, the second stage injection, and the main injection. In the vehicle control device according to claim 1 or 2,
When the vehicle speed detection unit detects a vehicle speed exceeding a second predetermined value that is greater than the first predetermined value by a predetermined value,
The vehicle control device, wherein the fuel injection control unit executes the first injection pattern even when the motor control unit issues an instruction to add motor resistance. In the vehicle control device according to any one of claims 1 to 3,
When the first injection pattern is executed, the fuel injection control unit generates a first pressure wave caused by combustion caused by the front injection and a second pressure wave caused by combustion caused by the main injection. A control device for a vehicle that executes the first-stage injection and the main injection such that . In the vehicle control device according to any one of claims 1 to 4,
When the first injection pattern is executed, the fuel injection control unit is configured to inject fuel at a timing between the first stage injection and the main injection in an injection period shorter than the first stage injection and the main injection. A control device for the vehicle that causes further injection. In the vehicle control device according to any one of claims 1 to 5,
A portion of the combustion chamber is defined by the crown surface of the piston, and the crown surface of the piston is provided with a cavity, the cavity comprising:
a lower cavity disposed in a radially central region of the crown surface and having a first bottom having a first depth in the axial direction of the cylinder;
an upper cavity having a second bottom portion disposed on the crown surface on the outer peripheral side of the lower cavity portion and having a second depth shallower than the first depth in the cylinder axial direction;
a lip connecting the lower cavity and the upper cavity,
The fuel injection valve injects fuel toward the cavity and is arranged at or near the radial center of the combustion chamber,
The fuel injection control unit is
In both the first injection pattern and the second injection pattern, the fuel injection timing is set so that the fuel injection by the first stage injection is directed toward the lip;
A control device for a vehicle, which executes the leading stage injection of the first injection pattern at a retarded side of the leading stage injection of the second injection pattern.

Images