JP6429082B2 - Spray interference judgment device, airflow control device - Google Patents

Description

  The present invention relates to a spray interference determination device that determines interference between fuel sprays injected into a cylinder of a compression self-ignition internal combustion engine and an airflow control device that controls the strength of the airflow in the cylinder.

  Conventionally, in a compression self-ignition type internal combustion engine represented by a diesel engine, which directly injects fuel into a cylinder and self-ignites and burns the fuel, for the purpose of improving the mixing state of air and fuel, An internal combustion engine that generates an airflow such as a swirl flow in a cylinder is known.

  In this type of internal combustion engine, it is necessary to appropriately control the strength of the airflow (swirl flow) in order to suppress NOx and soot emissions. Increasing the air flow leads to an increase in the combustion region, and increases the amount of NOx generated by combustion (NOx generation amount). For example, if the airflow is too strong in a state where the post-processing unit that purifies NOx is not functioning sufficiently at the start of the internal combustion engine, the amount of NOx that cannot be purified by the post-processing unit, that is, exhausted from the vehicle. There is a risk that the amount of NOx increases. Further, if the airflow is made too strong, the amount of interference between fuel sprays injected from each injection hole of the injector increases, and in the spray interference region, the amount of soot generated may increase due to an increase in equivalence ratio and insufficient oxygen. There is.

  On the other hand, if the airflow is too weak, the area where the fuel spray does not exist in the cylinder becomes large, and as a result, the combustion area becomes small, and oxygen in the cylinder cannot be effectively used in the combustion area, soot. There is a risk that the amount of generation will increase.

  In Patent Document 1, among the sprays that are injected from the injection holes of the injector and are adjacent to each other in the flow direction of the swirl flow, the swirl upstream side surface position of the spray located downstream in the swirl flow direction and the upstream side in the swirl flow direction The distance from the swirl downstream side surface position of the spray is determined. And the invention which changes the speed | rate of a swirl flow so that the space | interval may be in the predetermined range is disclosed.

JP 2013-160194 A

  In the invention of Patent Document 1, the swirl upstream side surface position and swirl downstream side surface position to be determined in order to determine interference between fuel sprays are determined from the spray angle, the swirl speed, and the spray wall collision time. However, in the invention of Patent Document 1, since the spray interference is determined without considering the mixed state of fuel and air such as the equivalence ratio, there is a possibility that an error may occur from the spray interference when actually burning. In order to suppress the occurrence of soot due to spray interference, it is necessary to determine the spray interference during combustion with high accuracy.

  On the other hand, using CFD technology (CFD: Calculation Fluid Dynamics), the space inside the cylinder is finely divided into meshes on the computer, and the mixing state of fuel and air is obtained for each mesh, and the obtained mixing of each mesh It is also conceivable to calculate the combustion region based on the state and determine the spray interference based on the combustion region. However, in this case, the calculation load becomes high, and it is difficult to mount on an actual system including an internal combustion engine.

  The present invention has been made in view of the above circumstances, and a spray interference determination device capable of easily and accurately determining interference during combustion between fuel sprays injected into a cylinder of a compression ignition type internal combustion engine, and a cylinder It is an object of the present invention to provide an airflow control device that can effectively suppress the generation of soot due to spray interference by controlling the airflow inside.

In order to solve the above-described problem, a spray interference determination device according to the present invention includes a compression self-ignition internal combustion engine that injects fuel into a cylinder from an injector having a plurality of injection holes and performs self-ignition combustion of the fuel. An end concentration acquisition means for acquiring an end concentration that is an oxygen concentration in the cylinder when combustion of the fuel injected into the cylinder ends;
Under the condition that the oxygen concentration in the cylinder is the concentration at the end, the following distance is defined as the combustion end position where the fuel reaches the injection hole at which the equivalence ratio becomes a predetermined value when there is no airflow in the cylinder. An end position estimating means for estimating by the equation of 1;
Time estimation means for estimating the time until the fuel injected at the end of the injection period in the case where there is no air flow in the cylinder reaches the combustion end position from the nozzle hole by the following equation (2);
Index acquisition means for acquiring an angular velocity of a swirl flow generated in the cylinder as an index indicating the airflow strength in the cylinder ;
The multiplication value of the angular velocity and the time is defined as an increase in the spray angle due to the air flow of the fuel spray injected from one of the nozzle holes, and the increase and one injection when there is no air flow in the cylinder. A spray angle estimating means for estimating a total spray angle based on a spray angle per hole and a total number of spray angles of each fuel spray when there is an air flow in the cylinder based on the number of the nozzle holes;
Determination means for determining interference between a plurality of fuel sprays injected from different nozzle holes based on the increase or the comparison between the total spray angle and a threshold;
Equipped with a,
In the following equation 1, the equivalent ratio φ is set to the predetermined value,
In the following formula 2, Δt is the time, and x _e is a combustion end position obtained by the following formula 1 .

  In an internal combustion engine in which fuel is continuously injected over time, the fuels injected at each point in the injection period do not burn at the same position at the same time. Burns close and early. Since the oxygen concentration at the combustion position of the fuel injected earlier is lowered, the fuel having a later injection time burns at a position farther from the injection hole than the combustion position. In this way, the fuel spray continuously burns at different positions.

  Under this assumption, the fuel that burns at the combustion end position among the fuels injected at each point in the injection period, that is, the period until the fuel injected at the end of the injection period reaches the combustion end position, It is the longest compared with the period until the fuel injected at the time reaches each combustion position. Therefore, the fuel combusted at the combustion end position is most easily affected by the airflow. In other words, the combustion end position in the combustion region is most susceptible to the influence of the airflow. In the present invention, since the interference between the fuel sprays is determined based on the combustion end position that is most susceptible to the influence of the airflow and the index indicating the strength of the airflow, the interference during the combustion can be accurately determined. In the present invention, since it is not necessary to calculate the entire combustion region when determining the spray interference, it is possible to easily determine the interference between the fuel sprays.

In the spray interference determination device of the present invention, the determination unit determines a difference between the total spray angle and a threshold value as an interference amount.
Moreover, the airflow control device of the present invention includes the spray interference determination device of the present invention,
An airflow adjusting means for weakening an airflow in the cylinder when the amount of interference is larger than a target value, and weakening or maintaining an airflow in the cylinder when the amount of interference is less than or equal to a target value ;
It is characterized by providing.

  According to the present invention, since the strength of the airflow is controlled based on the highly accurate interference determination result by the spray interference determination device of the present invention, it is possible to effectively suppress the generation of soot due to spray interference. Further, the soot generated by the spray interference at the combustion end timing (combustion end position) is easily discharged from the engine as a soot without being reoxidized because the reoxidation period until the exhaust valve is opened is short. In the present invention, the spray interference is determined based on the combustion end position, and the air flow is controlled based on the determination result. Therefore, the generation of soot at the combustion end timing with a short reoxidation period can be effectively suppressed. Further, by suppressing the generation of soot at the end of combustion, it becomes easy to secure a reoxidation period of soot, and as a result, the discharge of soot from the engine can be suppressed.

It is a block diagram of an engine system. It is a figure which showed a part of cross section in a cylinder perpendicular to the central axis of a cylinder, and how NOx and Soot amount change according to the combustion area for every strength of airflow, and the strength of airflow. It is a flowchart of the interference determination between fuel sprays and airflow adjustment processing which ECU performs. It is a figure of the fuel injection rate with respect to time. It is the figure which showed a mode that the fuel injected from the injection hole burned by changing a position continuously. It is a flowchart of a spray interference determination process (process of S5 of FIG. 3). It is a figure which shows having set the inspection surfaces 76 and 77 which apply a momentum preservation law with respect to the fuel spray. Upper stage shows a change in heat generation rate is a view showing a change in the average cylinder O ₂ concentration in the lower. It is the figure which showed the mode of spraying when there is no airflow in the upper stage, and showed the mode of spraying when there is an airflow in the lower stage. It is the figure which illustrated the map of the threshold value of the total spray angle with respect to in-cylinder temperature. Heat generation rate with respect to time (upper), the average cylinder O ₂ concentration (middle) is a diagram showing a change in the average temperature cylinder (bottom). It is the figure which showed the injection period in the upper stage, and showed the heat release rate in the lower stage.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of an engine system 1 mounted on a vehicle. The engine system 1 is configured to include a common rail diesel engine 10 (hereinafter simply referred to as an engine) as an internal combustion engine and various configurations necessary for the operation of the engine 10. In the present embodiment, the engine 10 is a four-cylinder engine having four cylinders 11. The engine 10 is a four-stroke engine that generates power in each cylinder 11 through four strokes of intake, compression, combustion, and exhaust. A combustion cycle (“720 ° CA” cycle) by four strokes of intake, compression, combustion, and exhaust is sequentially executed with a shift of “180 ° CA” between the cylinders 11, for example. When numbers 1 to 4 are assigned in order from the cylinder 11 on the right side of FIG. 1, for example, the combustion cycles are executed in order of the cylinders 1, 3, 4, and 2.

  At the center of the cylinder head constituting the upper wall of the cylinder 11, an injector 16 (fuel injection valve) for injecting fuel (for example, light oil) into the cylinder 11 (hereinafter referred to as the cylinder) is provided. A plurality of injection holes are formed at the tip of the injector 16 in the circumferential direction around the central axis of the injector 16, and fuel is injected from the injection holes in different directions. The fuel spray injected from the injector 16 undergoes compression self-ignition combustion in the cylinder. Further, a cooling water passage (water jacket) for circulating cooling water (coolant) is formed in the cylinder block constituting the side wall of the cylinder 11. The cooling water prevents the engine 10 from becoming too hot.

  Each cylinder 11 is formed with two intake ports, a swirl generation port 12 and a tumble generation port 13, as intake ports serving as inlets for intake air (gas) sucked into the cylinder. These intake ports 12 and 13 are formed in the cylinder head. The swirl generation port 12 is an intake port that generates a swirl flow in the gas sucked into the cylinder from the swirl generation port 12. The tumble generation port 13 is an intake port that generates a tumble flow in the gas sucked into the cylinder from the tumble generation port 13. Here, the swirl flow refers to a vortex flow of gas around the central axis of the cylinder 11 (rotating flow, lateral vortex flow). The tumble flow refers to a rotating flow (longitudinal vortex) around an axis in a plane perpendicular to the central axis of the cylinder 11. The gas sucked from the swirl generation port 12 travels in the cylinder while turning in the circumferential direction on the outer side (wall surface side) than the gas sucked from the tumble generation port 13. On the other hand, the gas sucked from the tumble generation port 13 travels downward (in the direction of the top surface of the piston) inside the gas sucked from the swirl generation port 12.

  In addition, an intake valve 14 that opens and closes the opening is provided at an opening that connects each of the intake ports 12 and 13 and the inside of the cylinder. Further, an exhaust port for discharging the gas after combustion in the cylinder from the cylinder is formed in the cylinder head. An exhaust valve 15 for opening and closing the opening is provided at an opening connecting the exhaust port and the inside of the cylinder.

  The engine system 1 is provided with an intake passage 21 through which fresh air (air) drawn into the cylinder flows. The intake passage 21 is provided with a supercharger 31 that compresses fresh air and an intercooler 32 that cools the fresh air compressed by the supercharger 31 from the upstream side. In addition, a throttle 33 for adjusting the amount of fresh air is provided in the intake passage 21 downstream of the intercooler 32. From the intake passage 21 downstream of the throttle 33, a passage 22 (an intake manifold passage, hereinafter referred to as an EGR lean gas passage) connected to each cylinder 11 is branched. Each EGR lean gas passage 22 is connected to the swirl generation port 12 of each cylinder 11. In the EGR lean gas passage 22 and the intake passage 21, only fresh air or a gas mixed with EGR gas flowing in from a connection passage 29 described later (hereinafter referred to as EGR lean gas) flows.

  Each cylinder 11 is connected to an exhaust manifold 23 that collectively collects exhaust gas discharged from the cylinder and passes it to the exhaust passage 27. In the exhaust passage 27, a turbocharger turbine 37 (variable nozzle turbo (VNT)) that recovers energy from the exhaust gas, and a post-processing device 38 that performs a predetermined process on the exhaust gas are provided in the exhaust passage 27 from the upstream side. Arranged in order. The aftertreatment device 38 is an oxidation catalyst that oxidizes and removes CO, HC, etc. in the exhaust gas, a DPF that removes PM in the exhaust gas, a NOx reduction catalyst that reduces and purifies NOx in the exhaust gas, and the like.

  Connected to the exhaust manifold 23 is an EGR passage 24 for returning a part of the exhaust gas to the intake system as EGR gas. The EGR passage 24 is provided with an EGR cooler 34 that cools the EGR gas flowing through the EGR passage 24, and an EGR valve 35 that adjusts the flow rate of the EGR gas downstream from the EGR cooler 34. A passage 25 (hereinafter referred to as an EGR rich gas passage) connected to each cylinder 11 branches off from the EGR passage 24 downstream of the EGR valve 35. Each EGR rich gas passage 25 is connected to the tumble generation port 13 of each cylinder 11. In the EGR rich gas passage 25, a gas (hereinafter referred to as an EGR rich gas) having a higher concentration of EGR gas (a higher exhaust concentration and a lower oxygen concentration) than the EGR lean gas flowing through the EGR lean gas passage 22 flows.

  The engine system 1 is provided with a connection passage 29 that connects the intake passage 21 and the EGR passage 24. The connection passage 29 connects the intake passage 21 before branching to the EGR lean gas passage 22 and the EGR passage 24 before branching to the EGR rich gas passage 25. By flowing EGR gas from the EGR passage 24 to the intake passage 21 via the connection passage 29, or by flowing fresh air from the intake passage 21 to the EGR passage 24, the amount of gas sucked into the cylinder from the swirl generation port 12, and The ratio of the amount of gas sucked into the cylinder from the tumble generating port 13 can be adjusted to a desired EGR rate while maintaining a predetermined value. The EGR rate is obtained by dividing the amount of EGR gas (exhaust gas) sucked into the cylinder by the total amount of gas sucked into the cylinder (fresh air intake amount + EGR gas intake amount). is there.

  Further, each EGR rich gas passage 25 has a swirl control valve 41 (hereinafter referred to as SCV) that adjusts the strength of the swirl flow (air flow) in the cylinder by adjusting the flow rate of the gas flowing through the EGR rich gas passage 25. Is provided. When the flow rate of the EGR rich gas is reduced by reducing the opening of the SCV 41, the momentum of the gas sucked from the swirl generation port 12 increases, and as a result, the swirl flow can be strengthened. On the contrary, if the opening of the SCV 41 is increased to increase the flow rate of the EGR rich gas, the momentum of the gas sucked from the swirl generation port 12 is weakened, and as a result, the swirl flow can be weakened. A motor 42 is connected to the SCV 41. The opening degree of the SCV 41 is controlled by the motor 42.

The engine system 1 is provided with various sensors necessary for operation control of the engine 10. Specifically, the intake passage 21 is provided with an intake pressure sensor 56 for detecting the pressure of the gas (EGR lean gas in FIG. 1) sucked into the cylinder, that is, the intake pressure (supercharging pressure) P. Similarly, the intake passage 21 is provided with an intake air temperature sensor 57 for detecting the temperature of the gas sucked into the cylinder, that is, the intake air temperature T. The exhaust passage 27 upstream of the turbine 37 is provided with an exhaust O ₂ sensor 58 that detects the oxygen concentration of the exhaust gas flowing through the exhaust passage 27, that is, the gas exhausted from the engine 10. Note that the exhaust O ₂ sensor 58 may be provided in the exhaust manifold 23. Further, instead of the exhaust O ₂ sensor 58, an A / F sensor for detecting the air-fuel ratio (A / F) of the exhaust gas may be provided.

  Further, the engine system 1 is provided with sensors other than these sensors 56 to 58. Specifically, the engine system 1 detects a rotation speed sensor 52 that detects the rotation speed of the engine 10 and an operation amount (depression amount) of an accelerator pedal for notifying the vehicle side of the torque required by the driver of the vehicle. An accelerator pedal sensor 53, an air flow meter 54 for detecting the amount of fresh air drawn into the cylinder, an injection pressure sensor 55 for detecting the injection pressure of fuel injected from the injector 16, and a cylinder for detecting the pressure in the cylinder (in-cylinder pressure) An internal pressure sensor 59 and the like are provided. The rotation speed sensor 52 is, for example, a crank angle sensor that detects the crank angle of the engine 10. The air flow meter 54 is a sensor that is provided in the intake passage 21 and detects a volume flow rate of gas flowing through the intake passage 21, for example. The injection pressure sensor 55 is a sensor that is provided, for example, on a common rail (not shown) that stores high-pressure fuel supplied to the injector 16 and detects the pressure in the common rail. The in-cylinder pressure sensor 59 is attached to the cylinder head such that the tip side is exposed in the cylinder.

  The engine system 1 controls the opening / closing (opening / closing timing, opening degree, etc.) of each valve (the throttle 33, the EGR valve 35, etc.) including the SCV 41 and the fuel supply by the injector 16 based on the detection values input from the sensors. Thus, an ECU 50 that controls the operation of the engine 10 is provided. The ECU 50 is mainly configured by a computer including a CPU, a ROM, a RAM, and the like. The ECU 50 includes a memory 51 such as an EEPROM or a flash memory. The memory 51 stores a program for processing executed by the ECU 50, various maps (for example, a map related to fuel injection and a map related to airflow control), and the like.

  Moreover, ECU50 determines the interference between the several fuel sprays injected from each nozzle hole of the injector 16, and adjusts the intensity | strength of an airflow (swirl flow) based on the determination result. That is, the ECU 50 corresponds to the spray interference determination device and the airflow control device of the present invention. Here, FIG. 2 shows a part of the cross section in the cylinder perpendicular to the central axis of the cylinder 11, and how the combustion region changes when the strength of the airflow is changed and the change of the combustion region. It is a figure explaining how the production | generation amount of NOx and Soot changes. FIG. 2 shows a state of combustion regions 171 to 173 (fuel sprays) of fuel spray injected so as to radiate from the injector 16 toward the wall surface 111 in the cylinder. Specifically, the left side of FIG. 2 shows the state of the combustion region 171 when the strength of the airflow is small, and the middle of FIG. 2 shows the state of the combustion region 172 when the strength of the airflow is medium. The right side of FIG. 2 shows a state of the combustion region 173 when the strength of the airflow is large.

  When the air flow becomes large, mixing of the fuel spray and air is promoted, so that the region of the air-fuel mixture is expanded. That is, as shown in FIG. 2, as the airflow increases, the combustion region expands in the direction of the swirl flow in the order of the combustion region 171 → the combustion region 172 → the combustion region 173. Further, when the airflow is small, the combustion region 171 is small, so the amount of NOx generated is small, but the oxygen in the cylinder cannot be used effectively, and the amount of soot is increased. When the airflow is medium, the combustion region 172 expands from the combustion region 171 when the airflow is small, and this expansion increases the NOx generation amount. On the other hand, the expansion of the combustion region increases the utilization efficiency of oxygen in the cylinder, and as a result, the amount of generated Soot is smaller than when the airflow is small. When the air flow is large, the combustion region 173 is further increased, so that the amount of NOx generated increases as in the case where the air flow is inside. If the airflow is too large, interference (overlap of fuel spray) occurs between adjacent combustion regions 173 (fuel sprays), and soot increases due to an increase in equivalence ratio and insufficient oxygen in the interference region.

  Thus, the combustion region changes depending on the strength of the air flow, and the amount of NOx and Soot changes due to the change in the combustion region. Therefore, in order to suppress the discharge amount of NOx and Soot, it is necessary to appropriately adjust the strength of the airflow according to the combustion region. That is, when interference between fuel sprays occurs, the Soot increases, so it is necessary to adjust the strength of the airflow so that the interference does not occur. On the other hand, in order to suppress the generation of soot, it is necessary to effectively use the oxygen in the cylinder at the time of combustion. For that purpose, it is necessary to secure a combustion area of a certain size, and for that purpose, It is necessary to ensure a certain level of airflow strength. Further, for example, there are times when the aftertreatment device 38 is not functioning sufficiently, such as when the engine 10 is started, and if the airflow becomes too strong at that time, the amount of NOx that cannot be purified by the aftertreatment device 38 may increase. is there.

  Hereinafter, the determination of the interference between the fuel sprays and the airflow adjustment process executed by the ECU 50 will be described. FIG. 3 shows an example of a flowchart of the processing. The process of FIG. 3 is started at the same time as the engine 10 is started, for example, and thereafter repeatedly executed at a predetermined cycle until the engine 10 stops.

When the processing of FIG. 3 is started, the ECU 50 first acquires various conditions necessary for determining interference between sprays in S5 described later (S1). The condition acquisition process of S1 includes a process (S2) of acquiring a condition (engine condition) related to the engine 10. In the process of S2, the engine speed NE is acquired from the speed sensor 52 as the engine condition. Also, the cylinder volume changes due to the vertical movement of the piston, but the cylinder maximum volume V _max that is the maximum value of the changing volume and the cylinder minimum volume V _min that is the minimum value of the volume are acquired as engine conditions. . Maximum volume V _max in the cylinder is the cylinder volume when the piston is in the position of the bottom dead center. Minimum volume V _min within the cylinder is a cylinder volume when the piston is in the position of top dead center. For example, the values of the volumes V _max and V _min are stored in the memory 51, and the volumes V _max and V _min may be acquired from the memory 51 in S2.

The condition acquisition process of S1 includes a process (S3) of acquiring an injection condition of fuel injected from the injector 16. In the processing of S3, the fuel injection pressure P _c , the fuel injection amount Q, the fuel injection timing T _inj (the value of the crank angle at which fuel injection has been performed), the fuel injection period t _inj (the fuel fuel injection has been performed) Corner width) and so on. Injection pressure P _c can be obtained from the injection pressure sensor 55 (see FIG. 1). Further, the injection amount Q, the injection timing T _inj , and the injection period t _inj are controlled by the ECU 50 so that the optimum engine operation can be performed using the engine speed, the engine load (the amount of depression of the accelerator pedal detected by the accelerator pedal sensor 53), and the like as parameters. A value determined by itself (applicable value) may be used.

Further, the condition acquisition process of S1 includes a process (S4) of acquiring a condition (intake condition) of air sucked into the cylinder. In the process of S4, the intake pressure P, the intake air temperature T, the intake O ₂ concentration, the swirl ratio SR, and the like are acquired as the intake conditions. The intake pressure P can be acquired from the intake pressure sensor 56 (see FIG. 1). The intake air temperature T can be acquired from the intake air temperature sensor 57 (see FIG. 1).

Intake O ₂ concentration (O ₂ concentration in the cylinder) is fresh air (air) oxygen concentration (about 21%) in, the fresh air amount, the oxygen concentration and EGR of the EGR gas (exhaust gas) to be suctioned into the cylinder It can be determined based on the amount of gas. Here, the amount of fresh air can be obtained from the detected value of the air flow meter 54, for example. More specifically, the volume V of fresh air sucked into the cylinder is obtained from the detection value of the air flow meter 54. From the volume V, the intake pressure P, the intake air temperature T, and the ideal gas equation of state PV = nRT, the number of moles n of fresh air drawn into the cylinder (= m / M, where m is the mass of air, M Is the molecular weight of air), and the number of moles n is converted to the mass m of fresh air to obtain the fresh air amount. Further, the oxygen ratio in the EGR gas may be the O ₂ concentration in the exhaust gas detected by the exhaust O ₂ sensor 58. Further, the amount of EGR gas can be obtained from the opening degree (EGR rate) of the EGR valve 35. For example, if the fresh air amount is 100, the oxygen concentration in the fresh air is 21%, the EGR gas amount obtained from the EGR rate is 50, and the oxygen concentration in the EGR gas is 10% (detected value of the exhaust O ₂ sensor 58), The total amount of gas sucked into the cylinder is 150 (= 100 + 50), and the oxygen amount is 26 (= 21 (= 100 × 21%) + 5 (= 50 × 10%)). Therefore, the intake O ₂ concentration is calculated as 26 ÷ 150 × 100, and is about 17.3%.

Incidentally, the intake O ₂ concentration is provided an O ₂ sensor for detecting the oxygen concentration in the intake passage 21, it may be determined directly by the O ₂ sensor.

  The swirl ratio SR is an index indicating the ratio between the rotational speed ω of the swirl flow and the engine speed NE, that is, an index indicating how many times the swirl flow rotates while the piston makes one reciprocation. The swirl ratio SR correlates with the opening degree of the SCV 41, and specifically, the swirl ratio SR increases as the opening degree of the SCV 41 decreases. Therefore, the relationship between the opening degree of the SCV 41 and the swirl ratio SR is examined in advance and stored in the memory 51. Then, the swirl ratio SR may be obtained based on the relationship stored in the memory 51 and the current opening degree of the SCV 41.

Further, in the condition acquisition process of S1, in addition to the conditions acquired in the processes of S2 to S4, detection values from each sensor provided in the engine system 1 are also acquired. Specifically, for example, the exhaust O ₂ sensor 58 detects The exhaust O ₂ concentration to be acquired is also acquired. The exhaust O ₂ concentration is used for estimating the combustion end position, which will be described later. The ECU 50 that executes the process of S1 corresponds to the end-time concentration acquisition means of the present invention. The exhaust O ₂ concentration corresponds to the end concentration of the present invention.

After acquiring various conditions in S1, next, spray interference is determined based on the conditions acquired in S1 (S5). Here, FIG. 4 and FIG. 5 are diagrams for explaining the concept of determination of spray interference. Specifically, FIG. 4 is a diagram _showing the fuel 70 injected during the injection period t _inj as a fuel injection rate (vertical axis) with respect to time (horizontal axis). FIG. 5 is a view showing combustion regions 101 to 103 of fuel injected from the injection holes 161 of the injector 16. The fuel injected from the injector 16 is gradually mixed with air as it leaves the injection hole, and the fuel is considered to burn when the mixed state of the fuel and air becomes appropriate. In other words, since the fuel is dispersed in a wider range in the cylinder as the distance from the injection hole is increased, the equivalent ratio per unit volume in the fuel injection direction becomes smaller as the distance from the injection hole is increased. In the present invention, the fuel is considered to burn when the equivalence ratio reaches a certain value (for example, equivalence ratio = 1). The equivalence ratio is an index representing the fuel concentration in the fuel / air mixture, and is an inverse of the excess air ratio λ, that is, a value obtained by dividing the theoretical air-fuel ratio by the actual air-fuel ratio.

More specifically, as shown in FIG. 4, when the fuel 70 is continuously injected with _respect to time, the fuel 71 injected at the beginning (first) of the injection period t _inj burns in the region 101 near the injection hole 161. (See the upper part of FIG. 5). The fuel 72 injected in the middle period of the injection period t _inj has a lower oxygen concentration in the region 101 due to the combustion of the fuel 71, and therefore, as shown in the middle stage of FIG. The fuel 71 burns after the combustion of the fuel 71. Further, the fuel 73 injected in the latter half (final) of the injection period t _inj is delayed in the combustion of the fuels 71 and 72 in the region 103 slightly farther than the region 102 because the oxygen concentration in the regions 101 and 102 is reduced. And burn. Here, the last injected fuel 73 has the longest period from the injection to the completion of combustion as compared with the fuels 71 and 72, and thus is most susceptible to the influence of airflow. Therefore, if it is determined whether or not the fuel 73 interferes, it can be determined whether or not the entire combustion has interfered. In the process of S5, spray interference is determined based on this concept. Details of the process of S5 will be described below.

FIG. 6 shows a flowchart of the process of S5. In the process of FIG. 6, first, the fuel that burns last among the total fuel injected from one injection hole during the injection period t _inj , that is, the fuel injected at the end of the injection period t _inj The reach distance (combustion position) from the hole is estimated as the combustion end position for the entire combustion (S21). The ECU 50 that executes the process of S21 corresponds to the end position estimating means of the present invention. Hereinafter, a method for obtaining the combustion end position will be described.

As shown in FIG. 7, with respect to the fuel spray 75 injected from one injection hole 161, an inspection surface 76 that is perpendicular to the injection direction at the position of the injection hole 161 and at a distance x from the injection hole 161, 77 is set. The following equation 1 is established according to the momentum conservation law between the inspection surfaces 76 and 77. In Equation 1, ρ _f represents the fuel density, that is, the mass of the fuel per unit volume. d indicates the diameter of the nozzle hole 161 (the nozzle hole diameter). v ₀ indicates the fuel spray speed at the position of the nozzle hole 161, that is, the spray initial speed. ρ _a indicates the gas density in the cylinder at the time of fuel injection. x indicates the distance (spray position) that the fuel spray reaches from the nozzle hole 161 in the fuel injection direction. θ represents the spray angle per spray hole (spray spread angle) when there is no airflow in the cylinder. v indicates the spray speed at the spray position x.

The left side of Equation 1 shows the momentum of spray on the inspection surface 76 (the nozzle hole position). That is, the value π (d / 2) ² v _{0 obtained} by multiplying the cross-sectional area π (d / 2) ² of the nozzle hole 161 by the initial spray velocity v ₀ indicates the volume of the spray passing through the inspection surface 76 per unit time, A value ρ _f π (d / 2) ² v _{0 obtained} by multiplying the volume by the fuel density ρ _f indicates the mass of the spray passing through the inspection surface 76 per unit time. A value ρ _f π (d / 2) ² v ₀ ^{2 obtained} by multiplying the mass by the initial spray velocity v ₀ is the momentum of spray on the inspection surface 76.

The right side of Equation 1 indicates the momentum of the gas being sprayed on the inspection surface 77. That is, assuming that the spray spreads in a conical shape with the position of the nozzle hole 161 as the apex as the distance from the nozzle hole 161 increases, the cross-sectional area of the spray at the position of the inspection surface 77 π [xtan (θ / 2) ] value obtained by multiplying the spray rate v to ² [pi [xtan (θ / 2)] ^{2 v} indicates the volume of gas in the spray passing through the inspection surface 77 per unit time, the in-cylinder gas density in the volume [rho _a A value ρ _a π [xtan (θ / 2)] ² v obtained by multiplying by ² represents the mass of the gas in the spray that passes through the inspection surface 77 per unit time. A value ρ _a π [xtan (θ / 2)] ² v ² obtained by multiplying the mass by the spray velocity v indicates the momentum of the gas being sprayed on the inspection surface 77.

Here, the following equation 2 is established with respect to the initial spray velocity v ₀ by the flow rate equation of the orifice. In Equation 2, c is a contraction coefficient, and is a constant determined by the nozzle shape of the injector 16. P _c is the injection pressure, P _cyl is the in-cylinder pressure at the time of fuel injection, and ρ _f is the fuel density.

Further, when Expression 1 is transformed into an expression for the spray velocity v, the following Expression 3 is established.

Here, since the relationship of v = dx / dt and ∫dt = ∫ (1 / v) dx is established, if the spray velocity v is eliminated from Equation 3 using this relationship, the following Equation 4 is established. In Expression 4, t is an elapsed time after the fuel is injected from the nozzle hole 161. This expression 4 is used in the processing of S23 described later.

Further, the equivalent ratio φ with respect to the spray position x can be expressed by the following Expression 5. In Equation 5, L _th is the stoichiometric air-fuel ratio, O 2 is the oxygen concentration at the spray position x, and the others are described above.

Ρ _a π [xtan (θ / 2)] ² v in the denominator of Equation 5 is the gas amount (gas mass) on the inspection surface 77 in FIG. Ρ _f π (d / 2) ² v ₀ in the numerator in Expression 5 is the amount of fuel (mass of fuel) on the inspection surface 77. The amount of fuel that passes through the inspection surface 77 per unit time is the same as the amount of fuel that passes through the inspection surface 76 per unit time. Further, in order to reflect the influence of the oxygen concentration O _{2 at} the spray position x on the equivalent ratio, Equation 5 includes 21 / O ₂ . This means that, at the spray position x, when the oxygen concentration is smaller than 21%, the equivalent ratio becomes larger than when the oxygen concentration is 21%. In other words, it means that the spray position x at which the equivalence ratio becomes a predetermined value (for example, 1) increases as the oxygen concentration O ₂ decreases.

Further, when Expression 3 is substituted for the spray velocity v in Expression 5, the following Expression 6 is obtained.

  The derivation of each of the above equations is described in the literature “Yutaro Waguri, Masaru Fujii, Tatsuo Amitani, Reijiro Tsuneya,“ Study on Spray Distance of Diesel Engine ”, Transactions of the Japan Society of Mechanical Engineers 25-156 (1959). , P. 820 ".

Here, FIG. 8 shows the change in the heat generation rate in the cylinder with respect to time in the upper stage, and shows the change in the average O ₂ concentration in the cylinder (average value of O ₂ concentration at each position in the cylinder) with respect to time in the lower stage. It shows. In the upper diagram of FIG. 8, the period in which the heat generation rate is generated indicates the combustion period. As shown in FIG. 8, the in-cylinder average O ₂ concentration in the combustion period gradually decreases with time. Further, the average cylinder O ₂ concentration in the combustion start t _s becomes intake O ₂ concentration. The average cylinder O ₂ concentration of combustion at the end t _e becomes O ₂ concentration in the exhaust gas discharged from the engine 10 in the exhaust stroke (exhaust O ₂ concentration).

Further, if the combustion is performed when the equivalence ratio φ = 1, the oxygen concentration in the cylinder at the end of combustion is _defined as the exhaust gas O2 concentration O 2 — _ex , and the equation 6 is transformed, the combustion end position x _e can be expressed by the following equation 7. it can. Equation 7, and phi = 1 in Formula 6, and _O 2 = _{O 2_ex,} x as x _e, is migrated formula that x _e on the left side. Equation 7 means the spray distance at which the equivalence ratio is 1 under the condition that the oxygen concentration in the cylinder is the exhaust O ₂ concentration. Combustion end position x _e corresponds to the last combustion position of the burning fuel of the total fuel injected during the injection period (reach from the injection hole), in other words, end the injection of the injection period This corresponds to the combustion position (reach distance from the nozzle hole) of the fuel that has been used.

In the process of S21 in FIG. 6 estimates the combustion end position x _e based on Equation 7. At this time, the fuel density ρ _f , the nozzle hole diameter d, the theoretical air-fuel ratio L _th, and the spray angle θ may use constant values stored in advance in the memory 51. The exhaust O ₂ concentration O _{2_Ex} in Formula 7 may be the detected value of the exhaust O ₂ sensor 58, which is acquired in the process of S1. The exhaust O ₂ concentration O _{2_Ex} may be determined based on the intake O ₂ concentration and injection amount Q obtained in the processing of S1. The injection amount Q correlates with the amount of combustion in the cylinder, and the combustion amount correlates with the amount of oxygen consumed by combustion. Therefore, by obtaining the amount of oxygen consumed by combustion based on the injection amount Q and reducing the intake O ₂ concentration by that amount of oxygen, the exhaust O ₂ concentration O _{2 — ex} can be obtained.

The in-cylinder gas density ρ _a in Equation 7 is expressed as follows, assuming that the fuel is injected when the piston is at the top dead center, as shown in Equation 8 below, the in-cylinder gas mass m _cyl at the top dead center is a value obtained by dividing the volume (minimum volume in the cylinder) V _min of the inner.

Minimum volume V _min within the cylinder is obtained in the process of S2 in FIG. The in-cylinder gas mass m _cyl is obtained by using the in-cylinder pressure P _{cyl at the} top dead center, the in-cylinder minimum volume V _min , the in-cylinder gas molecular weight M, the gas constant R, and the in-cylinder gas temperature T _cyl at the top dead center. The following equation 9 can be used. Equation 9 can be derived from the ideal gas equation of state PV = nRT.

In Equation 9, the in-cylinder minimum volume V _min is acquired by the process of S2 in FIG. As the molecular weight M, a predetermined value (about 29) may be used as the molecular weight of air. Further, the in-cylinder pressure P _cyl and the temperature T _cyl can be obtained by the following expressions 10 and 11. Expressions 10 and 11 are expressions obtained from Poisson's law. In Expressions 10 and 11, P is the intake pressure, V _max is the maximum volume in the cylinder, V _min is the minimum volume in the cylinder, T is the intake air temperature, and γ is the specific heat ratio of the gas in the cylinder. P, V _max , V _min , and T are acquired in the process of S1. A specific value may be used for the specific heat ratio γ. The in-cylinder pressure P _cyl may be obtained directly from the in-cylinder pressure sensor 59 (see FIG. 1).

After estimating the combustion end position in S21, next, the angular velocity ω of the airflow, which is an index indicating the strength of the airflow (swirl flow), is estimated based on the following equation 12 (S22). In Expression 12, NE is the number of revolutions of the engine 10, and is obtained by the process of S2 in FIG. SR is a swirl ratio, and is acquired by the process of S4. Note that a sensor for detecting the angular velocity ω may be provided, and the angular velocity ω may be acquired by the sensor. The ECU 50 that executes the process of S22 corresponds to the index acquisition means of the present invention.

Then, finally injected fuel injection period is estimated based on Equation 13 below time Δt to reach from the injection hole 161 into the combustion end position x _e (S23). In Equation 13, the combustion end position x _e is obtained by Equation 7 above. A predetermined value may be used for the fuel density ρ _f , the nozzle hole diameter d, and the spray angle θ. Further, the in-cylinder gas density [rho _a is obtained by the above equation 8. The initial spray velocity v ₀ is obtained by the above equation 2. It should be noted that constant values determined in advance may be used for the shrinkage coefficient c and the fuel density ρ _f in Equation 2. Injection pressure P _c is acquired in the process of S3. The in-cylinder pressure P _cyl in Equation 2 is obtained by Equation 10 above.

Equation 13 can be obtained from Equation 4 above. That is, when x in Expression 4 is replaced with x _e and t is replaced with Δt, the following Expression 14 is obtained. When this equation 14 is transformed into an equation for Δt, equation 13 is obtained. In addition, ECU50 which performs the process of S23 is equivalent to the time estimation means of this invention.

Next, the total spray angle θ all — ₀ is estimated by summing the spray angles of the fuel sprays injected from the nozzle holes when there is no airflow in the cylinder (S24). Specifically, assuming that the spray angle θ of each fuel spray is the same between the fuel sprays when there is no airflow in the cylinder, the total spray is calculated by the following formula 15 based on the spray angle θ and the number N of nozzle holes. The angle θ all — ₀ is obtained.

Next, a total spray angle θ _{all — 1} is estimated by summing up the spray angles of the fuel sprays when there is an air flow in the cylinder (S25). Specifically, as shown in FIG. 9, the air flow when there is (angular velocity omega), while Δt the last injected fuel injection period reaches the combustion end position x _e from the injection hole, the angular velocity omega and time Δt And the total spray angle θ _{all — 1} is _obtained by the following equation (16). In Equation 16, θ all — ₀ is the total spray angle when there is no airflow obtained by the process of S24. N is the number of nozzle holes. ω is the angular velocity of the airflow obtained by the process of S22. Δt is the time obtained by the process of S23.

Next, the presence / absence of interference between fuel sprays and the amount of interference are determined based on the total spray angle θ _{all_1} (S26). Specifically, a threshold (for example, 360 °) for interference determination is set, and the total spray angle θ _{all — 1} is compared with the threshold θ _th . Then, when the total spray angle θ _{all — 1} is larger than the threshold value θ _th, it is determined that the spray interferes, and when the total spray angle θ _{all — 1} is equal to or less than the threshold value θ _th , it is determined that the spray does not interfere. Further, a difference (= θ _all — 1− θ _th ) between the total spray angle θ _{all — 1} and the threshold value θ _th is obtained as the amount of spray interference. When this interference amount is a positive value, it indicates that the spray is interfering, and when it is a negative value, it indicates that there is no interference.

Here, in the present embodiment, it is assumed that the combustion is performed under the condition where the equivalence ratio is 1. However, depending on the conditions, there is a case where combustion does not occur even when the equivalence ratio becomes 1 due to the time delay of the combustion reaction. In particular, the lower the in-cylinder temperature, the greater the reaction time delay. Therefore, in the process of S26, if combustion does not occur even when the equivalence ratio becomes 1 due to a reaction time delay, the requirement for interference is changed. Specifically, for example, as shown in FIG. Then, the threshold value for interference determination is changed. That is, even if the total spray angle θ _{all — 1} is the same value, the threshold value that is the criterion for interference is decreased as the in-cylinder temperature is _lowered so that it is easier to determine that there is interference as the in-cylinder temperature is lower. The reason for this is that the lower the in-cylinder temperature, the longer the reaction time delay, and the more easily affected by the airflow until combustion.

For example, the initial threshold is 360 °, the estimated total spray angle θ _{all — 1} is 350 °, and due to the reaction time delay, when the spray expands beyond the threshold (360 ° or more), it burns, that is, with interference. And Also in this case, in order to determine that there is interference, for example, by changing the threshold from 360 ° to 340 ° based on the in-cylinder temperature, it is possible to determine that the total spray angle θ _{all — 1} > threshold, that is, that there is interference. become.

Here, a method of acquiring the in-cylinder temperature used for threshold setting will be described. FIG. 11 shows the time change of the heat generation rate in the cylinder in the upper stage, shows the time change of the average O ₂ concentration in the cylinder (average value of O ₂ concentration at each position in the cylinder) in the middle stage, and shows in the lower stage. A time variation of the in-cylinder average temperature (the average value of the temperature at each position in the cylinder) is shown. A period t _b (a period in which the heat generation rate is equal to or higher than a predetermined value) in which the heat generation rate in the upper part of FIG. 11 is generated indicates the combustion period. As shown in the middle and lower stages of FIG. 11, the in-cylinder average O ₂ concentration and the in-cylinder average temperature are not constant in the combustion period t _{b and} change as the combustion proceeds. Specifically, the in-cylinder average O ₂ concentration is highest at the start of combustion, and gradually decreases as combustion progresses. The average temperature is cylindrical, in the compression stroke will gradually increase in accordance with the piston rises, becomes the initial highest combustion period t _b, it decreases gradually in accordance with the combustion progresses.

In the present embodiment, an average value T _ave of the in-cylinder average temperature at each time point in the combustion period t _b (hereinafter simply referred to as the average in-cylinder temperature during the combustion period) is obtained as the in-cylinder temperature used for setting the threshold value. Specifically, the average in-cylinder temperature T _ave during the combustion period is estimated based on the following Expression 17.

In Expression 17, T _{cyl0 — s} is the in-cylinder temperature at the start of combustion, and is the in-cylinder temperature when the temperature increase due to combustion is not taken into account (that is, when there is no combustion). The in-cylinder temperature T _{cyl0 — s} can be obtained by the following equation 18. Expression 18 is an expression obtained from Poisson's law. In Equation 18, T is the intake air temperature, V _max is the maximum cylinder volume, γ is the specific heat ratio, and V _s is the cylinder volume at the start of combustion. Intake air temperature T, maximum volume V _max in the cylinder is acquired in the process of S1. A specific value may be used as the specific heat ratio γ. The in-cylinder volume V _s at the start of combustion is determined as described below, for example.

Here, FIG. 12 shows the injection period t _{inj in the} upper stage and the heat generation rate in the lower stage. As shown in FIG. 12, the combustion start time t _s is the start time T _{Inj_s} the injection period t _inj, initially injected fuel injection period t _inj reaches the combustion position x _s of the fuel from the injection hole the point in time plus the time Δt _s up to. In other words, the _{t s = T inj_s + Δt s} . The combustion position x _s means the combustion position of the fuel that burns first out of the total fuel injected during the injection period t _inj , that is, the combustion start position of the total fuel. The injection start time T _{inj_s} is acquired as the injection timing T _inj in the process of S3. Time Delta] t _s can be obtained by equation 19 below.

The equation 19, the x in the above formula 4 by replacing x _s, t to Delta] t _s, is an equation that is modified to equation for Delta] t _s. In Expression 19, parameters θ, d, v ₀ , ρ _a , and ρ _f are the same as Expression 13, and the combustion start position x _s can be obtained by Expression 20 below. Expression 20 is an expression in which the equivalent ratio φ = 1, oxygen concentration O ₂ = intake O ₂ concentration O _{2 —in} , and x = x _{s in} Expression 6 above, and x _s is shifted to the left side. Equation 20 means the spray distance at which the equivalence ratio is 1 under the condition that the oxygen concentration in the cylinder is the intake O ₂ concentration. In Formula 20, the reason for the oxygen concentration and the intake O ₂ concentration O _{2_In} is because the cylinder average O ₂ concentration in the combustion start time t _s, as shown in FIG. 8 the intake O ₂ concentration.

The memory 51 stores the relationship between the crank angle and the in-cylinder volume. Then, knowing the _{t s} = _{T inj_s} + _Δt s combustion start time t _s based on the equation of the crank angle at the combustion start time t _s, the relationship between the crank angle and the cylinder volume, which is stored in the memory 51 based on, it is possible to determine the in-cylinder volume V _s at the combustion start time t _s. Incidentally, on the basis of the cylinder pressure cylinder pressure sensor 59 to detect and calculate the heat release rate may be specified combustion start time t _s based on the heat generation rate. In this case, the heat generation rate may be set to point to the combustion start time t _s of switching the state of a predetermined value or more from a state of less than the predetermined value.

In Expression 17, T _{cyl0_e} is the in-cylinder temperature at the end of combustion, and is the in-cylinder temperature when the temperature increase due to combustion is not considered (that is, when there is no combustion). The in-cylinder temperature T _{cyl0_e} can be obtained by the following equation 21. Equation 21 is obtained from Poisson's law. In the formula 21, T is the intake air temperature, the _{V max} maximum volume in the cylinder, gamma is the specific heat ratio, _{V e} is the cylinder volume of the combustion end. Intake air temperature T, maximum volume V _max in the cylinder is acquired in the process of S1. A specific value may be used as the specific heat ratio γ. Cylinder volume V _e of the combustion end is obtained as described below, for example.

As shown in FIG. 12, a combustion end time t _e is the end point T _{Inj_e} the injection period t _inj, the last injected fuel injection period t _inj are to reach the combustion end position x _e from the injection hole It is the time when the time Δt is added. That is, t _e = T _{inj_e} + Δt. The injection end time T _{inj_e} is acquired as the injection timing T _inj in the process of S3. The time Δt is obtained by the above equation 13. The memory 51 stores the relationship between the crank angle and the in-cylinder volume. Then, knowing the _t e = _{T inj_e} + _Δt combustion end time t _e Based on the equation, the basis of the crank angle at the combustion end time t _e, on the relationship between the crank angle and the cylinder volume, which is stored in the memory 51 Thus, the in-cylinder volume V _e at the combustion end time t _e can be obtained. Incidentally, on the basis of the cylinder pressure cylinder pressure sensor 59 to detect and calculate the heat release rate may be specified combustion end time t _e on the basis of the heat generation rate. In this case, the heat generation rate may be set to point to the combustion termination point t _e switched to a state of less than the predetermined value in the state of a predetermined value or more.

In Expression 17, ΔT represents the temperature rise in the cylinder due to the combustion of the fuel, and can be obtained from Expression 22 below. In the formula 22, n is the number of moles of the in-cylinder gas, and the above formula 9 is modified so that the number of moles n = m _cyl / M = ( P _cyl · V _min ) / (R · T _cyl ) Can be sought. C _p is a constant pressure specific heat, that is, an amount of heat necessary to raise the temperature once while keeping the pressure constant, and a predetermined value may be used. ΔQ is the total amount of heat generated when the fuel burns. The total heat generation amount ΔQ correlates with the fuel injection amount, and increases as the injection amount increases. Therefore, for example, the relationship between the injection amount and the total heat generation amount ΔQ may be checked in advance and stored in the memory 51, and the total heat generation amount ΔQ may be obtained based on the relationship and the current injection amount. The injection amount is acquired by the process of S3. The total heat generation amount ΔQ may be obtained based on the in-cylinder pressure detected by the in-cylinder pressure sensor 59 (see FIG. 1).

Further, in equation 17, _{t b} is the burn period. Based on FIG. 12, the combustion period t _b can be expressed by the following Expression 23. In Expression 23, t _inj is the fuel injection period (see the upper part of FIG. 12), and is acquired in the process of S3. Δt is finally injected fuel injection period t _inj is the time to reach the combustion end position x _e from the injection hole, obtained by the above equation 13. Δt _s is the time _taken for the fuel injected at the beginning of the injection period t _inj to reach the combustion start position x _s from the injection hole, and is obtained by Equation 19 above. Incidentally, the cylinder pressure sensor 59 (see FIG. 1) is based on the cylinder pressure to detect and calculate the heat release rate, may be calculated combustion period t _b on the basis of the heat generation rate. In this case, the period during which the heat generation rate is equal to or greater than a predetermined value and the combustion duration t _b.

The first term (( T _{cyl0_s} + T _{cyl0_e} ) / 2) on the right side of Equation 17 indicates the average in-cylinder temperature during the combustion period when the temperature rise due to combustion is not taken into consideration, and the second term (ΔT / t _b ) It shows a value that the rise in temperature averaged over the combustion period t _b by combustion. Thus, by using Expression 17, the average in-cylinder temperature T _ave during the combustion period can be easily estimated without obtaining the in-cylinder temperature at all times during the combustion period.

In the process of S26, after obtaining the average in-cylinder temperature T _ave during the combustion period as described above, a threshold value for interference determination is set based on the average in-cylinder temperature T _ave and the map of FIG. To do. Then, based on a comparison between this threshold value and the total spray angle θ _{all — 1} obtained from Equation 16, the presence or absence of spray interference and the amount of interference are determined. 10 is stored in the memory 51 in advance. In FIG. 10, the upper limit of the threshold is 360 °, but an angle other than 360 ° (for example, an angle larger than 360 °) may be used as the upper limit of the threshold. After S26, the process in FIG. 6 is terminated and the process returns to the process in FIG.

In addition, ECU50 which performs the process of S24 and S25 is equivalent to the spray angle estimation means of this invention. The ECU 50 that executes the process of S26 corresponds to the determination means of the present invention.

Returning to the process of FIG. 3, next, the amount of interference (difference between the total spray angle θ _{all — 1} and the threshold θ _th ) obtained by the process of S5 (the process of S26 of FIG. 6) is a predetermined target. It is determined whether or not the value is larger (S6). This target value is determined, for example, from the viewpoint of suppressing the occurrence of soot, and is set to a value corresponding to the amount of interference in the middle combustion region 172 in FIG. 2 where the combustion region is neither too small nor too large. The target value is set to, for example, zero or a value slightly larger than zero.

  When the amount of interference is larger than the target value (S6: Yes), the opening of the SCV 41 is increased to weaken the airflow (swirl flow) (S7). At this time, how much the opening degree of the SCV 41 is increased may be a constant change amount of the opening degree of the SCV 41 regardless of the interference amount, or may be changed according to the interference amount. When the opening degree of the SCV 41 is changed according to the amount of interference, the opening degree of the SCV 41 is increased as the amount of interference increases. That is, the larger the amount of interference, the weaker the airflow. Thus, by weakening the airflow, the combustion region can be reduced from the state on the right side in FIG. 2 to the middle state, interference between sprays can be suppressed, and soot generation due to interference can be suppressed. Further, an increase in NOx due to the combustion region being too large can be suppressed. After S7, the process of FIG. 3 is terminated.

  On the other hand, when the amount of interference is equal to or less than the target value (S6: No), the opening of the SCV 41 is reduced to increase the airflow, or the SCV 41 is maintained at the current opening to maintain the strength of the airflow ( S8). At this time, for example, when the difference between the interference amount and the target value is less than a predetermined value, that is, when the interference amount is near the target value (in the case of the combustion region 172 in the middle of FIG. 2), the airflow strength is maintained. When the difference is greater than or equal to a predetermined value, that is, when the amount of interference is far from the target value (in the case of the combustion region 171 on the left side in FIG. 2), the airflow is increased. When the air flow is strengthened, the amount of change in the opening of the SCV 41 may be constant regardless of the amount of interference, or the amount of opening may be changed according to the amount of interference. When changing the opening according to the amount of interference, for example, the opening of the SCV 41 is reduced as the amount of interference decreases. That is, the smaller the amount of interference, the stronger the airflow.

  In this way, by strengthening the air flow, the combustion region can be expanded from the state on the left side in FIG. 2 to the middle state, and as a result, the generation of soot can be suppressed by making effective use of oxygen in the cylinder. . Further, by maintaining the airflow, the combustion region can be maintained in the middle state of FIG. 2, and as a result, the generation of soot can be suppressed. After FIG. 8, the process of FIG. 3 is terminated. In addition, ECU50 which performs the process of S6-S8 corresponds to the airflow adjustment means of this invention.

As described above, according to the present embodiment, the spray interference is determined based on the fuel combustion end position, and the combustion end position is determined based on the combustion condition (equivalence ratio) of the fuel injected at the end of the injection period. = 1, oxygen concentration = exhaust O ₂ concentration), the spray interference during combustion can be accurately determined. Further, by determining the spray interference based on the combustion end position that is most susceptible to the influence of the air flow in the combustion region, the determination can be performed easily and accurately. Further, since the exhaust O ₂ concentration is used as the in-cylinder oxygen concentration at the end of combustion in the estimation of the combustion end position, the oxygen concentration can be easily acquired without specifying the end of combustion.

  In addition, since the strength of the airflow is adjusted based on the amount of spray interference determined from the combustion end position, the combustion region is made to have an appropriate size that suppresses the spray interference without estimating the entire combustion region. As a result, the generation of soot can be effectively suppressed. The soot generated by the spray interference at the combustion end timing (combustion end position) is likely to be discharged from the engine as a soot without being reoxidized because the reoxidation period until the exhaust valve is opened is short. In the present invention, the spray interference is determined based on the combustion end position, and the air flow is controlled based on the determination result. Therefore, the generation of soot at the combustion end timing with a short reoxidation period can be effectively suppressed. Further, by suppressing the generation of soot at the end of combustion, it becomes easy to secure a reoxidation period of soot, and as a result, the discharge of soot from the engine can be suppressed.

  In the present embodiment, since the spray interference is determined based on the total spray angle obtained by summing the spray angles of the fuel sprays when there is an air flow, the spray interference of the entire combustion can be accurately determined. Further, since the total spray angle is estimated based on the time Δt until the fuel injected at the end of the injection period that is most susceptible to the airflow reaches the combustion end position from the nozzle hole, The impact can be accurately reflected.

  Moreover, since the threshold of the total spray angle (interference criterion) is reduced as the in-cylinder temperature during the combustion period is lower, it is possible to more accurately determine the spray interference in a manner that reflects the reaction time delay according to the in-cylinder temperature. .

  In addition, this invention is not limited to the said embodiment, A various change is possible to the limit which does not deviate from description of a claim. For example, in the above-described embodiment, the combustion end position is estimated by setting the value of the equivalence ratio φ in Equation 7 to 1. However, when it is assumed that combustion occurs when the equivalence ratio φ is other than 1, the equivalence ratio φ is other than 1. May be the value.

  Further, in the above embodiment, the spray interference is determined based on the total spray angle. However, the increase in the spray angle due to the air current, that is, the angular velocity ω of the air current and the fuel injected at the end of the injection period from the nozzle hole. The spray interference may be determined based on the multiplication value ωΔt with the time Δt until reaching the combustion end position. In this case, it is determined that there is interference when the increment ωΔt of the spray angle per nozzle hole is greater than the threshold value, and it is determined that there is no interference when it is equal to or less than the threshold value. Further, the spray interference may be determined based on the increase NωΔt caused by the air flow of the total spray angle obtained by multiplying the increase ωΔt of the spray angle by the number N of nozzle holes. According to this, since it is not necessary to calculate the total spray angle, spray interference can be determined more easily.

  In S6 to S8 of FIG. 3, the airflow is controlled based on whether or not the amount of interference is larger than the target value. However, the airflow may be controlled based on the presence or absence of interference. That is, the process of S6 in FIG. 3 may be changed to a process of determining the presence or absence of interference.

In the above embodiment, the threshold of the total spray angle is changed according to the in-cylinder temperature when determining the spray interference. However, the threshold is _kept constant, and the estimated total spray angle θ _{all_1} is set to the in-cylinder temperature. It may be corrected (changed) accordingly. In this case, the lower the in-cylinder temperature, the higher the total spray angle θ _{all — 1} is corrected. This also makes it possible to determine the spray interference in a manner that reflects the time delay of the reaction according to the in-cylinder temperature.

Further, in the above embodiment, the average in-cylinder temperature T _ave during the combustion period is acquired as the in-cylinder temperature used for setting the threshold value of the total spray angle, but instead of the average in-cylinder temperature T _ave , a specific period during the combustion period is obtained. The in-cylinder temperature at the time (for example, the in-cylinder temperature at the end of combustion) may be acquired.

  In the above embodiment, the strength of the airflow (swirl flow) is adjusted by SCV, but the strength of the swirl flow may be adjusted by other methods. Specifically, for example, the strength of the swirl flow may be adjusted by making the opening / closing timing and opening degree of the intake valve 14 different between the swirl generation port 12 and the tumble generation port 13. For example, the swirl flow can be strengthened by making the opening degree of the intake valve 14 of the tumble generation port 13 smaller than the opening degree of the intake valve 14 of the swirl generation port 12. The SCV can be omitted by adjusting the strength of the swirl flow with the intake valve 14.

1 Engine System 10 Diesel Engine 16 Injector 161 Injection Hole 50 ECU

Claims (7)

Combustion of fuel injected into the cylinder of a compression self-ignition internal combustion engine (10) in which fuel is injected into a cylinder from an injector (16) having a plurality of injection holes (161) and the fuel is self-ignited and combusted. End concentration acquisition means (S1) for acquiring an end concentration which is an oxygen concentration in the cylinder at the end of
Under the condition that the oxygen concentration in the cylinder is the concentration at the end, the following distance is defined as the combustion end position where the fuel reaches the injection hole at which the equivalence ratio becomes a predetermined value when there is no airflow in the cylinder. End position estimating means (S21) estimated by the formula 1;
Time estimation means (S23) for estimating the time until the fuel injected at the end of the injection period in the case where there is no airflow in the cylinder reaches the combustion end position from the nozzle hole by the following equation (2);
Index acquisition means (S22) for acquiring an angular velocity of a swirl flow generated in the cylinder as an index indicating the airflow strength in the cylinder ;
The multiplication value of the angular velocity and the time is defined as an increase in the spray angle due to the air flow of the fuel spray injected from one of the nozzle holes, and the increase and one injection when there is no air flow in the cylinder. Spray angle estimating means for estimating a total spray angle obtained by summing the spray angles of the fuel sprays when there is an air flow in the cylinder based on the spray angle per hole and the number of the nozzle holes (S24, S25) When,
Determination means (S26) for determining interference between a plurality of fuel sprays injected from different nozzle holes based on the comparison between the increment or the total spray angle and a threshold value;
Equipped with a,
In the following equation 1, the equivalent ratio φ is set to the predetermined value,
In the following equation 2, Δt is the time, and x _e is a combustion end position obtained by the following equation 1, A spray interference determination device (50).

_2. The spray interference determination device according to claim 1 , wherein the end concentration acquisition unit acquires an exhaust O ₂ concentration that is an O ₂ concentration of gas discharged from the cylinder as the end concentration. The spray interference determination apparatus according to claim 1 or 2 , wherein the predetermined value is set to 1. The said determination means determines the presence or absence of the said interference based on the comparison with the said increase and the said threshold value, or the comparison with the said total spray angle and the said threshold value, The any one of Claims 1-3 characterized by the above-mentioned. The spray interference determination apparatus as described. The determination means determines the presence or absence of the interference based on a comparison between the total spray angle and the threshold, and the threshold or the total in a direction that makes it easier to determine that there is interference as the temperature in the cylinder during the combustion period decreases. The spray interference determination device according to claim 4 , wherein the spray angle is changed.   The spray interference determination apparatus according to claim 1, wherein the determination unit determines a difference between the total spray angle and the threshold value as an interference amount. A spray interference judging device (50) according to claim 6 ;
Airflow adjusting means for weakening or maintaining the airflow in the cylinder when the amount of interference is greater than the target value, and for weakening or maintaining the airflow within the cylinder when the amount of interference is less than or equal to the target value (S6 to S8) When,
An airflow control device (50) comprising:

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