JP2013160194A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device with which exhaust emission of an internal combustion engine can be remedied and performance of the internal combustion engine can be improved by effectively utilizing oxygen and fuel within a cylinder.SOLUTION: When main injection is executed from a fuel injection valve including a plurality of nozzle holes in a common rail diesel engine, a swirl downstream-side side face position θL and a swirl upstream-side side face position θU of a fuel spray are calculated and a spray interval θD of sprays adjacent to each other is calculated (steps ST8, ST9, ST10). A fuel injection condition or a swirl control valve opening degree is corrected such that the spray interval θD is settled within a predetermined range (0≤θD≤Th)(step ST12). When the spray interval θD is greater than a spray interval allowable maximum value Th, fuel injection pressure is increased or a swirl speed is increased. When the spray interval θD is smaller than "0", main injection is divided or the swirl speed is decreased.

Description

  The present invention relates to a fuel injection control device for a compression ignition type internal combustion engine represented by a diesel engine. In particular, the present invention relates to measures for improving exhaust emission and improving the performance of an internal combustion engine.

  Conventionally, in an internal combustion engine equipped with a fuel injection device that directly injects fuel into a cylinder, as represented by a diesel engine, when incomplete combustion occurs during combustion of an air-fuel mixture in a combustion chamber Smoke is generated in the exhaust gas, leading to deterioration of exhaust emission.

  In particular, during high load operation in which the amount of fuel injected into the cylinder increases, control is required to achieve both the required engine output and the suppression of smoke generation. .

  In the following Patent Document 1, a fuel control index is calculated according to the in-cylinder oxygen amount calculated from the intake air amount and the exhaust gas recirculation amount, and the fuel injection parameter is determined according to the fuel control index and the engine speed. ing. This makes it possible to increase the in-cylinder oxygen amount by increasing the supercharging pressure during high load operation, and to increase the fuel injection amount by correcting the fuel control index to a large value while suppressing the occurrence of smoke. The acceleration of the vehicle is improved.

JP 2008-45503 A JP 2007-177773 A

  However, in the technique of the above-mentioned Patent Document 1, since only the in-cylinder oxygen amount and the fuel injection amount are controlled, combustion is performed by effectively using substantially the entire amount of oxygen in the cylinder. There is no guarantee. Ideally, the equivalent ratio in each combustion field formed by each fuel injected from each injection hole of the injector (fuel injection valve) is set to “1”, and oxygen in the cylinder contributes to combustion without excess or deficiency. It is preferable. In other words, it is ideal that oxygen and fuel in the cylinder are contributed to combustion without leaving them. However, in the technique of Patent Document 1, only the in-cylinder oxygen amount and the fuel injection amount are controlled as described above, and the fuel distribution in the cylinder is not controlled. There is a possibility that a region where the spray does not exist exists as a relatively wide region in the cylinder. That is, the region where oxygen that does not contribute to combustion exists is generated as a relatively wide region, and as a result, the equivalent ratio in the combustion field becomes rich, and smoke may be generated due to oxygen shortage.

  Conversely, if the fuel sprays injected from the injection holes of the injector overlap each other, the equivalence ratio may be rich even in the overlapping region, and smoke may be generated due to lack of oxygen. is there.

  Note that Patent Document 2 discloses an internal combustion engine that performs main injection (hereinafter sometimes referred to as “main injection”) that contributes to torque generation of the internal combustion engine and pilot injection that injects fuel before the main injection. In an engine, the control for defining the interval between the fuel spray in the main injection and the fuel spray in the pilot injection by optimizing the swirl flow is disclosed, but the interval between the fuel sprays injected in the main injection is disclosed. No proposal has yet been made regarding optimization. In general, the injection amount in the main injection during the high load operation is significantly larger than the injection amount in the pilot injection. For this reason, at the time of execution of the main injection, whether or not the region where the fuel spray does not exist is in the cylinder, and whether or not the fuel sprays injected in the main injection overlap. Smoke generation is greatly affected. Therefore, optimizing the interval between the fuel sprays injected in the main injection is extremely important for ensuring both the required engine output and suppressing the occurrence of smoke. .

  The present invention has been made in view of such a point, and an object of the present invention is to improve exhaust emission of an internal combustion engine and improve the performance of the internal combustion engine by effectively using oxygen and fuel in combustion in a cylinder. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can be realized.

-Summary of invention-
The outline of the present invention taken in order to achieve the above-described object is that, when main injection (main injection) is executed, the interval between adjacent fuel sprays is controlled and the interval is optimized. Each of the oxygen and the fuel can be effectively contributed to combustion.

-Solution-
Specifically, the present invention relates to fuel injection in a compression self-ignition internal combustion engine that performs fuel injection for generating engine output from a plurality of nozzle holes of a fuel injection valve toward a cylinder where a swirl flow is generated. The control device is assumed. Among the sprays injected from the respective nozzle holes and adjacent to each other in the swirl flow direction with respect to the fuel injection control device of the internal combustion engine, the swirl upstream side surface position of the spray located downstream in the swirl flow direction, and the swirl flow direction At least one of the fuel injection condition of the fuel injection valve and the speed of the swirl flow is changed so that the interval between the position of the spray located on the upstream side and the side surface on the downstream side of the swirl is within a predetermined range.

  More specific solutions include the following. First, it is assumed a fuel injection control device for a compression self-ignition internal combustion engine that has a swirl control valve that can control the swirl speed in the cylinder and injects fuel into the cylinder from a plurality of nozzle holes of the fuel injection valve And For the fuel injection control device of the internal combustion engine, in-cylinder state calculation means, swirl speed calculation means, spray characteristic calculation means, wall surface collision time calculation means, swirl downstream side face calculation means, swirl upstream side face calculation means, spray interval calculation Means, interval determination means, injection condition correction means, and swirl control valve opening correction means. The in-cylinder state calculating means calculates the in-cylinder density from the engine operating state. The swirl speed calculating means calculates a swirl speed from the engine operating state. The spray characteristic calculation means calculates the penetration, spray angle, and injection period of the spray injected from the fuel injection valve. The wall surface collision time calculating means calculates the time until the spray collides with the wall surface in the combustion chamber from the swirl speed and the spray characteristics. The swirl downstream side surface calculating means calculates a swirl downstream side surface position in the spray. The swirl upstream side surface calculating means calculates a swirl upstream side surface position in the spray. The spray interval calculation means calculates an interval in the swirl flow direction between sprays ejected from adjacent nozzle holes from the wall surface collision time, the swirl downstream side surface position, and the swirl upstream side surface position. The interval determining means determines whether or not the spray interval is within a predetermined range. The injection condition correcting means corrects a condition when the fuel injection valve injects spray. The swirl control valve opening correction means corrects the opening of the swirl control valve. Based on the spray interval, at least one of the injection pressure, the injection timing, the maximum injection amount, the number of divisions, and the swirl control valve opening when the fuel injection valve injects the spray is changed. .

  By these specific matters, the interval between the sprays injected from the respective injection holes of the fuel injection valve and adjacent to each other in the swirl flow direction can be adjusted within a predetermined range in which the amount of smoke generated can be suppressed. . For this reason, since the space | interval between the sprays mutually adjacent | abutted in a swirl flow direction is large, the equivalence ratio in a combustion field becomes rich, and it does not occur that smoke generate | occur | produces due to oxygen shortage. In addition, the sprays adjacent to each other in the swirl flow direction partially overlap each other, so that the equivalence ratio becomes rich and smoke is not generated due to lack of oxygen. In particular, during high-load operation where the fuel injection amount increases, it is possible to avoid the generation of smoke while obtaining the required output of the internal combustion engine, and it is possible to improve both the performance of the internal combustion engine and the improvement of exhaust emission. .

  The execution conditions of the operation for changing the fuel injection condition of the fuel injection valve and the speed of the swirl flow include the following. That is, when the time from the start of fuel injection from the nozzle hole until the spray of the fuel collides with the wall surface of the recessed portion of the piston top surface is less than the fuel injection period of the fuel injection valve, the swirl The upstream side surface position and the swirl downstream side surface position are obtained, and at least one of the fuel injection condition of the fuel injection valve and the speed of the swirl flow is changed so that the distance between the side surface positions is within a predetermined range. It is configured to do.

  If the time until the fuel spray collides with the wall surface of the recess on the top surface of the piston exceeds the fuel injection period of the fuel injection valve, the fuel spray may not collide with the wall surface of the recess. In this case, it is difficult to determine whether or not the sprays adjacent to each other in the swirl flow direction overlap each other, and the swirl upstream side surface position, the swirl downstream side surface position, Even if the interval is calculated, there is a high possibility that these values include an error, and there is a possibility that an appropriate fuel injection condition change or swirl flow speed change cannot be performed. For this reason, only when the time from when the fuel injection from the injection hole is started until the spray of the fuel collides with the wall surface of the concave portion of the piston top surface is equal to or shorter than the fuel injection period of the fuel injection valve, The swirl upstream side surface position, the swirl downstream side surface position, and the interval between these side surface positions are calculated, and the fuel injection conditions are changed and the swirl flow speed is changed based on the calculated positions. As a result, the reliability of the control can be ensured, and the effect of improving both the performance of the internal combustion engine and the exhaust emission can be reliably achieved.

  Examples of the calculation method of the swirl downstream side surface position, the swirl upstream side surface position, and the distance between the side surface positions include the following.

The swirl downstream side surface position is expressed by the following formula (1)
θL = (1/2) × spray angle + A × Vsw × time (1)
θL: Swirl downstream side position Vsw; swirl speed tip; time until the spray collides with the wall surface in the combustion chamber A: calculated by the diffusion rate of fuel spray toward the downstream in the swirl flow direction,
The swirl upstream side surface position is expressed by the following equation (2)
θU = (1/2) × spray angle (2)
θU: Calculated based on the swirl upstream side surface position,
The interval between the side surface positions is expressed by the following equation (3).
θD = (360 / number of nozzle holes) − (θL + θU) (3)
θD: It is calculated by the interval between the side surface positions.

  The above formula (1) indicates that the swirl downstream side surface position is moved by the fuel injected from the fuel injection valve flowing in the circumferential direction in the cylinder by the swirl flow, or the swirl downstream side surface by the diffusion of the fuel spray itself. It is considered that the position moves toward the downstream side in the swirl flow direction. Thereby, the space | interval of each side surface position is computable with high precision.

  Specific control for setting the interval between the swirl upstream side surface position and the swirl downstream side surface position within a predetermined range includes the following.

  First, in the case of changing the fuel injection condition of the fuel injection valve, when the interval between the swirl upstream side surface position and the swirl downstream side surface position is a predetermined value or more, the fuel injection pressure from the fuel injection valve To raise.

  As a result, as the fuel injection pressure from the fuel injection valve increases, the spray angle of the fuel increases, the distance between the swirl upstream side surface position and the swirl downstream side surface position decreases, and the fuel in the cylinder Distribution can be equalized. As a result, oxygen in the cylinder can be contributed to combustion without excess or deficiency, and smoke can be avoided.

  Further, when the sprays adjacent to each other partially overlap each other, the fuel injection from the fuel injection valve is divided into a plurality of times and executed.

  As a result, the fuel injection amount per fuel injection (split main injection) is reduced, the fuel spray angle is reduced, and the overlap of sprays is eliminated. As a result, the area where the equivalence ratio is rich is reduced, and it is possible to avoid the occurrence of smoke.

  In the case of changing the speed of the swirl flow, the speed of the swirl flow is increased when the distance between the swirl upstream side surface position and the swirl downstream side surface position is a predetermined value or more. .

  Further, when the sprays adjacent to each other partially overlap, the speed of the swirl flow is reduced.

  By changing the speed of these swirl flows, the diffusion amount of the fuel spray injected into the cylinders downstream in the swirl flow direction changes. Specifically, when the speed of the swirl flow is increased, the diffusion amount of the fuel spray injected into the cylinder to the downstream side in the swirl flow direction increases, and the swirl downstream side surface position is located downstream of the swirl flow direction. The swirl upstream side surface position of the spray located at is approached. On the contrary, when the speed of the swirl flow is reduced, the amount of spray sprayed into the cylinder is reduced downstream in the swirl flow direction, and the side surface position on the downstream side of the swirl is located upstream in the swirl flow direction. Will move towards. By adjusting the position of the swirl downstream side surface in this way, the fuel distribution in the cylinder can be equalized, and oxygen in the cylinder can be contributed to combustion without excess and deficiency. Can be avoided.

  In the present invention, the interval between adjacent fuel sprays is controlled to optimize the interval. Therefore, it is possible to suppress the generation of smoke, and it is possible to improve both the performance of the internal combustion engine and the exhaust emission.

It is a mimetic diagram showing the whole engine system composition concerning an embodiment. FIG. 5 is a schematic diagram showing a partial region in the cylinder (around the fuel injection region of the three injection holes), and the state of each spray in the cavity when the main injection is executed (the state of the spray moved by the swirl flow) It is the figure which looked at the state) from the cavity upper direction. It is a figure which shows the relationship between the spraying wall surface collision time and the fuel injection period. It is a figure which shows the main injection control routine. It is the figure seen from the cavity side which shows the change of the distribution of the spray in a cavity. It is a figure which shows an example of each change of the spray space | interval and smoke generation amount with respect to the change of the spray angle of a fuel. FIG. 7A is a diagram showing a state of each spray in the cavity when the spray interval θD is larger than the spray interval allowable value Th, and FIG. 7B is a diagram in which adjacent sprays partially overlap each other. It is a figure which shows the state in the cavity of each spray in a case. FIG. 8A is a diagram showing a state of each spray in the cavity when the spray interval θD is larger than the spray interval allowable value Th, and FIG. 8B is a diagram when the fuel injection pressure is increased. It is a figure which shows the state in the cavity of each spray. FIG. 9A is a diagram showing a state of each spray in the cavity when adjacent sprays partially overlap each other, and FIG. 9B is a diagram showing the inside of each spray cavity when the main injection is divided. It is a figure which shows the state in. FIG. 10A is a diagram showing a state of each spray in the cavity when the spray interval θD is larger than the spray interval allowable value Th, and FIG. 10B is a diagram showing each spray when the swirl speed is increased. It is a figure which shows the state in the cavity of. FIG. 11A is a diagram illustrating a state of each spray in the cavity when adjacent sprays partially overlap each other, and FIG. 11B is a cavity of each spray when the swirl speed is reduced. It is a figure which shows the state in the inside.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

-Overall system configuration-
FIG. 1 is a schematic diagram showing an overall configuration of an engine system in an embodiment of the present invention. As shown in FIG. 1, the engine system includes an internal combustion engine (engine) 1. The internal combustion engine 1 includes four cylinders 2, 2,. A cooling water flow path (water jacket) 3 is formed outside the cylinders 2, 2,..., And a water temperature sensor 21 that generates an output corresponding to the cooling water temperature is disposed in the cooling water flow path 3. Has been.

  A piston (not shown in FIG. 1) is arranged in each cylinder 2, 2,..., And each piston is connected to the crankshaft 5 via connecting rods 4, 4,. A crank angle sensor 22 that transmits a pulse signal every time the crankshaft 5 rotates by a predetermined angle is disposed in the vicinity of the crankshaft 5.

  A direct injection type fuel injection valve (injector) 6, 6,... Is attached to a cylinder head (not shown) of the internal combustion engine 1 corresponding to each cylinder 2, 2,. These fuel injection valves (fuel injection devices) 6, 6,... Are disposed at the center upper portion in the cylinder 2, and are provided with a piezoelectric element (piezo element) inside the cylinder 2. The piezo injector is configured to inject and supply fuel.

  Specifically, the fuel injection valve 6 is provided with a nozzle needle (not shown) at the tip of the casing, and the nozzle needle is configured to be movable back and forth within the casing. A plurality of nozzle holes (for example, twelve at equal intervals in the circumferential direction) are formed at the tip portion of the casing. When the nozzle needle is in the advanced position, each nozzle needle is ejected by the tip portion of the nozzle needle. While the hole is closed, each nozzle hole is opened when the nozzle needle is moved backward (lifted), and the fuel is injected from the fuel injection valve 6 by the pressure difference between the inside of the casing and the cylinder 2. It has become. The fuel injection valve 6 includes a piezoelectric actuator inside, and is connected to an ECU (Electronic Control Unit) 30 via an EDU (Electrical Driving Unit) 40. The EDU 40 includes a known drive circuit that performs charging and discharging of the piezo stack of the piezo actuator based on a command signal (injection command signal) from the ECU 30. Thereby, it is possible to change the lift speed of the nozzle needle that opens and closes each nozzle hole by controlling energization of the piezo actuator of the fuel injection valve 6 (changing the charge application speed to the piezo stack). It has become. Details of the fuel injection control of the fuel injection valve 6 will be described later.

  An intake system including an intake manifold 7 and a throttle valve 8 and an exhaust system including an exhaust manifold and a catalyst device (not shown) are connected to the cylinder head. Then, air is sucked into the cylinder 2 from the intake system in accordance with the opening operation of an intake valve (not shown) provided in each cylinder 2, 2,... The fuel is injected from the fuel injection valve 6 to combust in the cylinder 2. Specifically, as shown in FIG. 5 (a cross-sectional view of a part of the piston 50 viewed from the side), fuel is injected into a cavity (concave portion) 51 formed in the center of the top surface of the piston 50. The fuel is burned. The combustion energy causes the piston 50 to reciprocate, and the reciprocating motion is converted into the rotational motion of the crankshaft 5 by the connecting rod 4 to obtain engine torque as an output. Further, the exhaust gas discharged from the cylinder 2 in accordance with the opening operation of an exhaust valve (not shown) is purified by a catalyst device provided in the exhaust system.

  Further, the intake system is provided with a swirl control valve (swirl speed variable mechanism) 13 for making the speed of the swirl flow (horizontal swirl flow) in the cylinder 2 variable (see FIG. 1). ). Specifically, as the intake port, two systems of a normal port and a swirl port are provided for each cylinder 2, 2,..., Of which a swirl control valve 13 comprising a butterfly valve whose opening degree can be adjusted is provided in the normal port. Is arranged. An actuator (not shown) is connected to the swirl control valve 13 so that the flow rate of air passing through the normal port can be changed according to the opening of the swirl control valve 13 adjusted by driving the actuator. . As the opening degree of the swirl control valve 13 increases, the amount of air taken into the cylinder 2 from the normal port increases. For this reason, the swirl generated by the swirl port becomes relatively weak, and the inside of the cylinder 2 becomes a low swirl (a state where the swirl speed is low). Conversely, the smaller the opening of the swirl control valve 13, the smaller the amount of air drawn into the cylinder 2 from the normal port. For this reason, the swirl generated by the swirl port is relatively strengthened, and the inside of the cylinder 2 becomes a high swirl (state where the swirl speed is high).

  Further, each of the fuel injection valves 6, 6,... Is connected to a common rail 9 as a fuel pressure accumulating container. A common rail pressure sensor 23 for detecting the internal pressure (fuel pressure) is attached to the common rail 9. A booster pump 11 is connected to the common rail 9 via a fuel pipe 10, and a fuel tank 12 is connected to the suction side of the booster pump 11. That is, the fuel in the fuel tank 12 is boosted by the booster pump 11 and supplied to the common rail 9. The supplied high-pressure fuel is distributed from the common rail 9 to the fuel injection valves 6, 6,.

  The ECU 30 is electrically connected to the water temperature sensor 21, crank angle sensor 22, and common rail pressure sensor 23. In addition, an accelerator opening sensor 24 that detects the amount of depression of the accelerator pedal by the driver, an air flow meter 25 that is provided in the intake system and detects the intake air amount, and an intake pressure sensor 26 that detects the intake pressure are also electrically connected to the ECU 30. Connected. And the output from these sensors 21-26 is input into ECU30. The ECU 30 is electrically connected to, for example, the fuel injection valve 6, the booster pump 11, the swirl control valve 13, etc. (the fuel injection valve 6 is connected via the EDU 40 and is connected to the swirl control valve 13). The driver 41, which is a swirl control valve opening correction means, is connected to an actuator (not shown) of the swirl control valve 13) and outputs necessary control signals (command signals) to control these devices.

  Specifically, the ECU 30 controls the pressure of the fuel supplied from the fuel tank 12 to the common rail 9 by issuing a control signal to the booster pump 11. Further, the swirl speed is adjusted as described above by controlling the opening degree of the swirl control valve 13. Further, the fuel injection control of the fuel injection valve 6 is performed by issuing a control signal (injection command signal) toward the fuel injection valve 6.

  As fuel injection from the fuel injection valve 6, pre-injection (sub-injection) and main injection (main injection) can be executed. Pre-injection is an operation for injecting a small amount of fuel in advance prior to main injection. The pre-injection is an injection operation for suppressing the ignition delay of fuel due to the main injection and leading to stable diffusion combustion.

  The main injection is an injection operation (torque generating fuel supply operation) for generating torque of the internal combustion engine 1. The injection amount in the main injection is basically determined so as to obtain the required torque according to the operating state such as the engine speed, the accelerator operation amount (accelerator opening), the coolant temperature, the intake air temperature, and the like. . For example, the higher the engine speed (the engine speed calculated based on the detection value of the crank angle sensor 22), the more the accelerator operation amount (the accelerator pedal depression amount detected by the accelerator opening sensor 24). The larger the value (the larger the accelerator opening), the higher the required torque value of the internal combustion engine 1, and the larger the fuel injection amount in the main injection.

  In addition to the above-described pre-injection and main injection, after-injection and post-injection are performed as necessary. After injection is an injection operation for increasing the exhaust gas temperature. Specifically, after injection is executed at a timing at which most of the combustion energy of the supplied fuel is obtained as thermal energy of the exhaust gas without being converted into torque of the internal combustion engine 1. Further, the post injection is an injection operation for directly introducing fuel into the exhaust system to increase the temperature of the catalyst device.

  Further, the fuel injection pressure at the time of executing the fuel injection is determined by the internal pressure of the common rail 9. As the common rail internal pressure, generally, the target value of the fuel pressure supplied from the common rail 9 to the fuel injection valve 6, that is, the target rail pressure, basically becomes higher as the engine load (engine load) becomes higher and the engine speed. The higher the (engine speed), the higher. That is, the ECU 30 adjusts the fuel discharge amount of the booster pump 11 so that the common rail pressure becomes equal to the target rail pressure set based on the engine operating state, that is, the fuel injection pressure matches the target injection pressure. To measure.

-Control system configuration-
As a characteristic configuration of the present embodiment, the ECU 30 includes therein a memory 31, an in-cylinder state calculation unit 32, a swirl speed calculation unit 33, a spray characteristic calculation unit 34, a wall surface collision time calculation unit 35, and a swirl downstream side. A side face calculating means 36, a swirl upstream side face calculating means 37, a spray interval calculating means 38, an interval determining means 39, and a swirl control valve opening correcting means (the driver) 41 are provided. Further, the ECU 30 outputs an injection command signal to the EDU 40 as the injection condition correction means.

  Hereinafter, the function of each means will be described with reference to FIG. FIG. 2 is a schematic diagram showing a part of the area in the cylinder 2 (around the fuel injection area of the three injection holes), and the state of each spray in the cavity 51 when the main injection is executed ( It is the figure which looked at the state of the spray which moved by the swirl flow) from the cavity 51 upper direction. FIG. 2 shows a state in which the sprays partially overlap each other.

  The in-cylinder state calculation means 32 includes a pulse signal from the crank angle sensor 22, a cooling water temperature detection signal from the water temperature sensor 21, an accelerator opening signal from the accelerator opening sensor 24, and intake air from the air flow meter 25. A signal relating to the operating state of the internal combustion engine 1 such as an amount detection signal is read, and the state in the cylinder 2 (in-cylinder density, intake air amount, etc.) is calculated. For example, the density of air flowing into the cylinder is calculated based on the coolant temperature detection signal from the water temperature sensor 21, and the engine speed and the accelerator opening sensor 24 calculated based on the pulse signal from the crank angle sensor 22. The fuel injection amount is calculated from the accelerator opening detected by the above, and the in-cylinder density is calculated from the air density and the fuel injection amount. The method for calculating the in-cylinder density is not limited to this. For example, a map in which the relationship between the output signal of each sensor and the in-cylinder density is defined in advance by experiment or simulation is stored in the ROM of the ECU 30. The in-cylinder density may be obtained from this map.

  The swirl speed calculation means 33 calculates the swirl speed Vsw in the cylinder 2 from the engine speed calculated based on the pulse signal from the crank angle sensor 22 and the intake air amount detected by the air flow meter 25. To do. The swirl speed Vsw is calculated by an arithmetic expression stored in the ROM of the ECU 30 and using the engine speed and the intake air amount as parameters. Further, a map in which the relationship between the output signal of each sensor and the swirl speed Vsw is defined in advance by experiment or simulation may be stored in the ROM of the ECU 30, and the swirl speed Vsw may be obtained from this map.

  The spray characteristic calculation means 34 is an initial value of fuel injection (when performing a plurality of main injections (split main injection), the initial value of each injection), and the cylinder 2 calculated by the in-cylinder state calculation means 32. Penetration (spray penetration force), fuel spray angle, and injection period are calculated from the internal state (in-cylinder density, intake air amount, etc.). The initial value of the fuel injection includes a fuel pressure (corresponding to the fuel injection pressure) detected by the common rail pressure sensor 23, a fuel injection amount, and the like. This fuel injection amount is recognized based on a command signal (injection command signal) output from the ECU 30 to the EDU 40. The penetration and spray angle increase as the fuel injection pressure increases. The injection period is obtained from the fuel injection amount and the fuel injection pressure, and is calculated as a period during which a target fuel injection amount is obtained. In addition, as a calculation method of the spray angle, a well-known arithmetic expression (for example, “Huan's formula”) may be used. Further, a spray angle map obtained by mapping the relationship between the spray form of the main injection mode (the nozzle needle lift speed, the injection pressure, the injection amount, etc.) and the spray angle is stored in the ROM of the ECU 30 beforehand. The spray angle may be obtained from this spray angle map.

  The wall surface collision time calculating unit 35 calculates the wall surface collision time from the penetration calculated by the spray characteristic calculating unit 34 and the injection period. The wall surface collision time is the time from the start of fuel injection until the fuel spray reaches the wall surface (the wall surface 52 of the recess (cavity 51) formed on the top surface of the piston 50). For this reason, when the fuel spray does not reach the cavity wall surface 52, the wall surface collision time is sufficiently long with respect to the injection period.

  FIG. 3 shows the relationship between the wall surface collision time and the fuel injection period. The solid line in the waveform indicating the main injection spray tip position in the figure shows the case where the wall surface collision time is shorter than the fuel injection period. That is, this is a case where part of the fuel spray collides with the cavity wall surface 52 during the fuel injection period (timing at which fuel injection from the fuel injection valve 6 has not yet ended). In this case, the fuel spray colliding with the cavity wall surface 52 is then reversed toward the fuel injection valve 6 side (in the drawing, the position becomes shorter after the main injection spray tip position reaches the cavity wall surface 52). See).

  In addition, the waveform of the main injection spray tip position indicated by the alternate long and short dash line in the figure indicates a case where the wall surface collision time is longer than the fuel injection period. That is, the fuel spray does not reach the cavity wall surface 52 even when the fuel injection period ends.

  The swirl downstream side surface calculation means 36 determines the spray angle (the spray characteristic calculation means when the wall surface collision time is shorter than the injection time (when a part of the fuel spray collides with the cavity wall surface 52 during the fuel injection period). 34) and the swirl speed Vsw (the swirl speed calculated by the swirl speed calculating means 33) are used to calculate the swirl downstream side surface position θL. As shown in FIG. 2, the swirl downstream side surface position θL is the axis of the fuel injected from the nozzle hole (indicated by the alternate long and short dash line in the figure, the axis before flowing by the swirl flow; the central axis of the nozzle hole To the spray side surface on the downstream side in the swirl flow direction, and is calculated by the following equation (1).

θL = (1/2) × spray angle + A × Vsw × time (1)
Here, “timp” is a wall surface collision time, and “A” is a diffusivity of the fuel spray toward the downstream side in the swirl flow direction, for example “1.1”. The value of the diffusivity is not limited to this, and can be obtained by experiments and simulations.

  The fuel injected from the fuel injection valve 6 is caused to flow in the circumferential direction in the cylinder 2 by the swirl flow, so that the swirl downstream side surface position θL moves (moves toward the downstream in the swirl flow direction). In addition, in the fuel spray, the swirl downstream side surface position θL moves toward the downstream side in the swirl flow direction also by diffusion of itself. The equation (1) calculates the swirl downstream side surface position θL in consideration of these.

  The swirl upstream side surface calculation means 37 determines the spray angle (the spray characteristic calculation means when the wall surface collision time is shorter than the injection time (when a part of the fuel spray collides with the cavity wall surface 52 during the fuel injection period). The swirl upstream side surface position θU is calculated from the spray angle calculated by 34. As shown in FIG. 2, the swirl upstream side surface position θU is determined by the swirl flow from the axial center of the fuel injected from the nozzle hole (axial center before flowing by the swirl flow; substantially coincides with the central axis of the nozzle hole). It is given as an angle to the spray side surface upstream in the direction, and is calculated by the following equation (2).

θU = (1/2) × spray angle (2)
In the calculation formula (2) for the swirl upstream side surface position θU, the reason why the swirl velocity Vsw and the fuel spray diffusivity are not included is as follows. Is shorter than the injection time (when a part of the fuel collides with the cavity wall surface 52 during the fuel injection period), the fuel injection from the fuel injection valve 6 is still continued at the start of this calculation. This is because there is a spray that has not yet been diffused and is sprayed in the circumferential direction under the influence of a swirl. That is, the swirl upstream side surface position θU is uniquely determined only by the spray angle.

  The spray interval calculation means 38 calculates the spray interval θD using the swirl downstream side surface position θL and the swirl upstream side surface position θU. The spray interval θD is adjacent to the sprays adjacent to each other (circumferential interval in the cylinder 2; the swirl downstream side surface position θL of the spray located upstream in the swirl flow direction and the downstream in the swirl flow direction. The distance from the swirl upstream side surface position θU of the spray). When the sprays adjacent to each other do not overlap and there is a gap between them, the spray interval θD is a positive value. When the sprays adjacent to each other partially overlap, the spray interval θD is a negative value (see the state shown in FIG. 2).

  This spray interval θD is calculated by the following equation (3).

θD = (360 / number of nozzle holes) − (θL + θU) (3)
The interval discriminating means 39 discriminates whether or not the spray interval θD calculated by the spray interval calculating means 38 is within an appropriate range. As an appropriate range, from the value (spray interval θD = 0) in which adjacent sprays do not overlap with each other and no gap is generated, the gap between adjacent sprays can ensure a predetermined oxygen utilization rate or more. The value is within the range (spraying interval θD ≦ Th). Hereinafter, this Th is referred to as “a spray interval allowable maximum value”. This allowable spray interval maximum value Th is set in advance through experiments, simulations, and the like, and is set as a value that suppresses the amount of smoke generated during fuel combustion to less than a predetermined regulated amount.

  The injection condition correction means (EDU) 40 changes the fuel injection condition when the spray interval θD is not appropriate. Specifically, the spray interval θD is adjusted within a predetermined range (0 ≦ θD ≦ Th) by controlling the fuel injection pressure and the fuel injection mode. Specific control operations will be described later.

  The swirl control valve opening correction means 41 changes the opening of the swirl control valve 13 when the spray interval θD is not appropriate. Specifically, the swirl speed Vsw is controlled by changing the opening degree of the swirl control valve 13, thereby adjusting the spraying interval θD within a predetermined range (0 ≦ θD ≦ Th). Specific control operations will be described later.

−Main injection control operation−
Next, the main injection control operation in the engine system configured as described above will be specifically described. FIG. 4 is a flowchart (main injection control routine) showing the procedure of the main injection control operation in the present embodiment. This flowchart is repeatedly executed every predetermined time after the internal combustion engine 1 is started or every time fuel injection from the fuel injection valve 6 (main injection) is performed.

  First, in step ST1, the current operating state of the internal combustion engine 1 is read. Specifically, the coolant temperature detection signal from the water temperature sensor 21, the pulse signal from the crank angle sensor 22, the accelerator opening signal from the accelerator opening sensor 24, and the intake air amount detection signal from the air flow meter 25. A signal relating to the operating state of the internal combustion engine 1 such as is read.

  In step ST2, the state (cylinder density, intake air amount, etc.) in the cylinder 2 is calculated from the read operating state of the internal combustion engine 1 (in-cylinder state calculation in the in-cylinder state calculation means 32 described above). Operation).

  Next, the process proceeds to step ST3, where the swirl in the cylinder 2 is determined from the rotational speed of the internal combustion engine 1 calculated based on the pulse signal from the crank angle sensor 22 and the intake air amount detected by the air flow meter 25. The speed Vsw is calculated (the above-described swirl speed calculating operation in the swirl speed calculating means 33).

  Next, the process proceeds to step ST4, and an initial value of fuel injection (in the case of performing a plurality of main injections (divided main injection), the initial value of each injection) is read.

  Then, in step ST5, penetration (spray penetration force), fuel spray angle, and injection period are calculated from the read initial value of the fuel injection and the state in the cylinder 2 calculated in step ST2. The above-described spray characteristic calculation operation in the spray characteristic calculation means 34).

  In step ST6, the wall collision time timp is calculated from the penetration calculated in step ST5 and the fuel injection period (the above-described wall collision time calculation operation in the wall collision time calculation means 35).

  In step ST7, the wall surface collision time timp calculated in step ST6 is compared with the injection period calculated in step ST4. Specifically, whether or not the wall surface collision time timp is equal to or shorter than the injection period, that is, when the fuel injection operation from the fuel injection valve 6 is completed or before the fuel spray is applied to the cavity wall surface 52. It is determined whether or not the collision occurs (the tip position of the fuel spray reaches the cavity wall surface 52).

  When the wall surface collision time timp exceeds the injection period and NO is determined in step ST7, the fuel spray does not collide with the cavity wall surface 52. Therefore, the correction of the injection condition and the swirl control valve 13 It returns without performing opening correction together. In the case where the fuel spray does not collide with the cavity wall surface 52, it is difficult to determine whether or not the adjacent sprays overlap each other, and the swirl downstream side surface position θL, the swirl upstream side Even if the side surface position θU and the spray interval θD are calculated, there is a high possibility that these values include an error, and it may not be possible to correct the correct injection conditions or the swirl control valve 13. It is.

  On the other hand, if the wall surface collision time timp is equal to or shorter than the injection period and YES is determined in step ST7, the process proceeds to step ST8 to calculate the swirl downstream side surface position θL. In other words, the swirl downstream side surface position θL is calculated using the equation (1) (the swirl downstream side surface calculation operation described above in the swirl downstream side surface calculation means 36).

  In step ST9, the swirl upstream side surface position θU is calculated. That is, the swirl upstream side surface position θU is calculated using the equation (2) (the above-described swirl upstream side surface calculation operation in the swirl upstream side surface calculation means 37).

  In step ST10, the spray interval θD is calculated. That is, the spray interval θD is calculated by using the formula (3) (the above-described spray interval calculating operation in the spray interval calculating means 38).

  Next, the process proceeds to step ST11, where it is determined whether or not the spray interval θD calculated in step ST10 is within the predetermined range described above. As described above, the predetermined range is set to “0” to “Th (a spray interval allowable maximum value)” (0 ≦ θD ≦ Th).

  In general, as shown in FIG. 5, the fuel injected from the fuel injection valve 6 diffuses into the cavity 51, and the fuel is injected in the cavity wall surface 52 (in the extending direction of the spray axis indicated by the dashed line I in the figure). After colliding with the wall 6 facing the valve 6 (see FIG. 5A), it grows while inverting along the cavity wall 52 (see the arrow shown in FIG. 5A), and the fuel injection valve 6 The flow direction changes so as to go to (see FIG. 5B).

  In this case, if the spray angle of the fuel injected from the fuel injection valve 6 is smaller than an appropriate value, as shown in FIG. 7A (this FIG. The upper stage is when the fuel spray reaches the cavity wall surface 52, and the lower stage shows a state where the spray is reversed along the cavity wall surface 52 after a predetermined time has elapsed. In other words, the gap (spray interval θD) between the fuel sprays adjacent to each other increases, and a region where no fuel spray exists may occur as a relatively wide region in the cylinder 2. In such a situation, there is a region where oxygen that does not contribute to fuel combustion exists, and as a result, smoke may be generated due to insufficient oxygen in the combustion field. In such a case, the relationship between the spray interval θD and the amount of smoke generated with respect to the fuel spray angle is in the range indicated by the spray angle α in FIG. 6, and the smaller the spray angle, the larger the spray interval θD, and accordingly the combustion field. The amount of smoke generated due to the lack of oxygen at this time will increase. Such a situation is assumed, for example, when the fuel injection pressure is relatively low or when the swirl speed is relatively low. Further, in this case, the momentum of the spray (the momentum in which the fuel injected from the fuel injection valve 6 flows toward the cavity wall surface 52) is relatively large, and the momentum in the swirl flow direction is relatively small. The spray interval θD is increased.

  On the other hand, when the spray angle of the fuel injected from the fuel injection valve 6 is larger than an appropriate value, as shown in FIG. 7B (this FIG. In the case of overlapping, the upper stage is a state before the fuel spray reaches the cavity wall surface 52, and the lower stage is a state in which the spray is reversed along the cavity wall surface 52 after a predetermined time has passed. 2), the adjacent fuel sprays partially overlap each other, and there is a possibility that smoke is generated due to lack of oxygen in the overlapping region. In such a case, the relationship between the spray interval θD and the amount of smoke generated with respect to the fuel spray angle is in the range indicated by the spray angle β in FIG. 6. The larger the spray angle, the smaller the spray interval θD (the spray interval θD is negative) As a result, the fuel sprays overlap each other), and accordingly, the amount of smoke generated is increased by the fuel in the overlapping region. Such a situation is assumed, for example, when the fuel injection pressure is relatively high or when the swirl speed is relatively high. Further, in such a situation, the growth on the fuel injection valve 6 side after the fuel spray collides with the cavity wall surface 52 is weakened. As a result, the air utilization rate in the cylinder deteriorates, and this also causes the amount of smoke generated. (In the diagram shown in the lower part of FIG. 7B, the air in the region A1 does not contribute to the combustion, and as a result, the equivalence ratio in the spray becomes rich). Moreover, in this case, the momentum of the spray (the momentum in which the fuel injected from the fuel injection valve 6 flows toward the cavity wall surface 52) is relatively small, and the momentum in the swirl flow direction is relatively large. The fuel sprays overlap each other.

  If the spray interval θD is not within the predetermined range, that is, if the spray interval θD is smaller than “0”, or if the spray interval θD is larger than “Th”, NO is determined in step ST11. Here, the case where the spray interval θD is smaller than “0” means that adjacent fuel sprays partially overlap each other, and when combustion is performed in this overlapped part, smoke is caused due to lack of oxygen. This is a case where the occurrence is a concern. On the other hand, when the spray interval θD is larger than “Th”, the interval between adjacent fuel sprays is large and the oxygen utilization rate is low, so that the oxygen in the cylinder is not fully utilized. This is a case where there is a concern about the generation of smoke due to lack of oxygen in the combustion field.

  If NO is determined in step ST11, the process proceeds to step ST12, and it is determined that the spray interval θD is not optimized, and the injection condition correction or the swirl control valve 13 opening correction is executed (about these correction operations). Will be described later).

  On the other hand, when the spray interval θD is within the predetermined range, that is, when the spray interval θD is within the range of “0” to “Th”, YES is determined in step ST11. Here, the case where the spray interval θD is in the range of “0” to “Th” means that there is no interval between adjacent fuel sprays, or even if there is an interval, the value is This is a small case where a sufficient oxygen utilization rate is secured and smoke is hardly generated.

  If the spray interval θD is within the predetermined range and YES is determined in step ST11, the spray interval θD has been optimized, and the amount of smoke generated is less than the predetermined regulated amount. It returns without executing correction of conditions or correction of the opening of the swirl control valve 13.

  By repeating the above operation, the injection condition correction or the swirl control valve 13 opening degree correction is performed so that the spray interval θD is within the predetermined range.

−Adjustment operation of spray interval−
Next, the correction operation (correction of injection conditions and correction of the opening degree of the swirl control valve 13) performed in step ST12 will be described. This correction operation includes a fuel injection pressure adjustment operation, an injection division operation, and a swirl speed adjustment operation. Each will be described below.

(Fuel injection pressure adjustment operation)
First, the fuel injection pressure adjustment operation will be described. This fuel injection pressure adjusting operation is performed when the spray interval θD is larger than the spray interval allowable value Th as shown in FIG. 8A, for example.

  Specifically, when the spray interval θD is larger than the spray interval allowable maximum value Th (Th <θD), the ECU 30 increases the fuel discharge amount of the booster pump 11 by increasing the target rail pressure. Increase the amount. As a result, the internal pressure of the common rail 9 increases, and the fuel injection pressure from the fuel injection valve 6 increases accordingly. When the fuel injection pressure increases in this way, the fuel spray angle increases and the penetration of the injected fuel increases.

  Then, as shown in FIG. 8B, the fuel injection pressure is fed back so that the spray interval θD is within the predetermined range (0 ≦ θD ≦ Th) when the spray tip position reaches the cavity wall surface 52. Control.

  Here, the target value of the spray interval θD is set to a value slightly larger than “0 (0 = θD)”, for example. This is because when the target value of the spray interval θD is set to “0”, some sprays partially overlap each other due to the influence of the sensing value error of each sensor and the variation in the diameter of each nozzle hole. This is to avoid this. The target value of the spray interval θD is not limited to this.

  By the above fuel injection pressure adjusting operation, as shown in the upper part of FIG. 8B, the fuel distribution in the cylinder is equalized, and oxygen in the cylinder can contribute to combustion without excess or deficiency. Also, the equivalent ratio does not become rich because the sprays partially overlap each other. Further, as shown in the lower part of FIG. 8B, the fuel injection valve 6 when the fuel spray colliding with the cavity wall surface 52 is reversed along the cavity wall surface 52 as the penetration increases as the fuel injection pressure increases. In this way, the spray can be diffused over a wide range.

  As a result, it is possible to avoid the generation of smoke due to oxygen shortage in the combustion field. In particular, during high-load operation where the amount of fuel injection increases, it is possible to avoid the generation of smoke while obtaining the required output of the internal combustion engine 1, and to improve both the performance of the internal combustion engine 1 and the improvement of exhaust emissions. Can do.

(Split split operation)
Next, the injection division operation will be described. For example, as shown in FIG. 9A, the injection division operation is performed when the sprays partially overlap (when the spray interval θD is a negative value).

  Specifically, when the spray interval θD is a negative value, the ECU 30 is required for this main injection by executing two or three divided main injections as the main injection mode. The total main injection amount (total fuel injection amount for obtaining the required torque) is ensured. That is, after the preceding main injection is executed, the fuel injection is temporarily stopped, and after a predetermined interval, the subsequent main injection is executed. This interval is set, for example, as the shortest valve closing period determined by the performance of the fuel injection valve 6 (the shortest period from when the fuel injection valve 6 is closed until the valve opening is started: 200 μs, for example). The interval of this divided main injection is not limited to the above value. By executing such divided main injection, the fuel spray angle is reduced by reducing the fuel injection amount per main injection.

  Then, as shown in FIG. 9B, the number of divisions of the main injection so that the spray interval θD when the spray tip position reaches the cavity wall surface 52 is within the predetermined range (0 ≦ θD ≦ Th). And feedback control of the interval. Further, a map defining the number of divisions of main injection and the interval with respect to the value (negative value) of the spray interval θD is stored in the ROM of the ECU 30, and the division number and interval of main injection are determined from this map. You may make it ask.

  By the above injection split operation, as shown in the upper part of FIG. 9 (b), the fuel distribution in the cylinder is equalized, and oxygen in the cylinder can contribute to combustion without excess or deficiency. Also, the equivalent ratio does not become rich because the sprays partially overlap each other. Further, as shown in the lower part of FIG. 9B, the fuel spray of each divided injection is diffused over a wide range in the cavity 51. Specifically, when the injection amount of the preceding main injection (split main injection) is increased and the injection amount of the subsequent main injection (split main injection) is decreased, the fuel injected by the preceding main injection The penetration of the spray is high, and the penetration of the fuel spray injected in the subsequent main injection is low. For this reason, the fuel spray of the preceding main injection reaches the cavity wall surface 52 and reverses along the cavity wall surface 52. Then, a combustion field is formed around the cavity wall surface 52 (see the spray F1 in the lower stage of FIG. 9B). Further, the fuel spray of the subsequent main injection does not reach the cavity wall surface 52, and forms a combustion field on the front side of the cavity wall surface 52 (see the spray F2 in the lower stage of FIG. 9B).

  As a result, it is possible to avoid the generation of smoke due to oxygen shortage in the combustion field. In particular, during high-load operation where the amount of fuel injection increases, it is possible to avoid the generation of smoke while obtaining the required output of the internal combustion engine 1, and to improve both the performance of the internal combustion engine 1 and the improvement of exhaust emissions. Can do.

(Swirl speed adjustment operation)
Next, the swirl speed adjustment operation will be described. In this fuel injection pressure adjusting operation, for example, as shown in FIG. 10A, when the spray interval θD is larger than the spray interval allowable value Th, and as shown in FIG. Can be executed in any case (when the spray interval θD is a negative value).

  First, when the spray interval θD is larger than the spray interval allowable value Th (Th <θD), the ECU 30 increases the swirl speed by reducing the opening of the swirl control valve 13. As a result, the amount of spray injected into the cylinder to the downstream side in the swirl flow direction increases, and the swirl downstream side surface position θL becomes the swirl upstream side surface position θU of the spray located downstream in the swirl flow direction. It will approach.

  Then, as shown in FIG. 10B, the swirl control valve 13 is set so that the spray interval θD when the tip position of the spray reaches the cavity wall surface 52 is within the predetermined range (0 ≦ θD ≦ Th). Feedback control of the opening. In FIG. 10B, the two-dot chain line indicates the state of each spray before the execution of the swirl speed adjustment operation, and the solid line indicates the state of each spray after the execution of the swirl speed adjustment operation.

  The target value of the spray interval θD here is also set to a value slightly larger than “0 (0 = θD)”, as in the case of the fuel injection pressure adjustment operation described above. The target value of the spray interval θD is not limited to this.

  On the other hand, when the sprays partially overlap each other (when the spray interval θD is a negative value), the ECU 30 decreases the swirl speed by increasing the opening of the swirl control valve 13. As a result, the diffusion amount of the spray injected into the cylinder toward the downstream side in the swirl flow direction is reduced, and the swirl downstream side surface position θL moves toward the upstream side in the swirl flow direction.

  Then, as shown in FIG. 11B, the swirl control valve 13 is set so that the spray interval θD when the tip position of the spray reaches the cavity wall surface 52 is within the predetermined range (0 ≦ θD ≦ Th). Feedback control of the opening. In FIG. 11B, the two-dot chain line indicates the state of each spray before execution of the swirl speed adjustment operation, and the solid line indicates the state of each spray after execution of the swirl speed adjustment operation. In this case, as the swirl speed decreases, the spray momentum (the momentum in which the fuel injected from the fuel injection valve 6 flows toward the cavity wall surface 52) becomes relatively large, and the fuel spray diffuses toward the cavity wall surface 52 side. The amount is expanding.

  The target value of the spray interval θD here is also set as a value slightly larger than “0 (0 = θD)”. The target value of the spray interval θD is not limited to this.

  As described above, by adjusting the swirl speed by controlling the opening degree of the swirl control valve 13, the fuel distribution in the cylinder is equalized, and oxygen in the cylinder can contribute to combustion without excess or deficiency. Also, the equivalent ratio does not become rich because the sprays partially overlap each other. As a result, it is possible to avoid the generation of smoke due to oxygen shortage. In particular, during high-load operation where the fuel injection amount increases, it is possible to avoid the generation of smoke while obtaining the required output of the internal combustion engine 1, and to improve both the performance of the internal combustion engine 1 and the improvement of exhaust emission. Can do.

-Other embodiments-
In the embodiment, the case where the present invention is applied to an in-line four-cylinder diesel engine mounted on an automobile has been described. The present invention is applicable not only to automobiles but also to engines used for other purposes. Further, the number of cylinders and the engine type (separate type engine, V-type engine, horizontally opposed engine, etc.) are not particularly limited.

  In the embodiment, the case where the spray interval θD between the fuel sprays injected at the same time is optimized has been described as an example. The present invention is not limited to this, and when a plurality of main injections (split main injection) are performed, the spray between the fuel spray injected in advance and the fuel spray injected subsequently. The present invention can also be applied to the case where the interval is optimized.

  The number of injection holes of the fuel injection valve 6 is not limited to the above (12), and the present invention is applicable to any internal combustion engine equipped with a fuel injection valve having a plurality of injection holes in the circumferential direction. is there.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a control that achieves both ensuring engine performance and improving exhaust emission by optimizing the interval between sprays of main injection injected from each injection hole of a fuel injection valve in a common rail type diesel engine. It is.

1 Internal combustion engine 2 Cylinder 6 Fuel injection valve (fuel injection device)
30 ECU
32 In-cylinder state calculation means 33 Swirl speed calculation means 34 Spray characteristic calculation means 35 Wall surface collision time calculation means 36 Swirl downstream side face calculation means 37 Swirl upstream side face calculation means 38 Spray interval calculation means 39 Interval discrimination means 40 EDU (injection condition) Correction means)
41 Swirl control valve opening correction means 50 Piston 51 Cavity 52 Cavity wall surface θU Swirl upstream side surface position θL Swirl downstream side surface position θD Spray interval Vsw Swirl speed tip Wall surface collision time

Claims (8)

In a fuel injection control device for a compression self-ignition internal combustion engine that performs fuel injection for generating engine output from a plurality of injection holes of a fuel injection valve toward a cylinder where a swirl flow is generated,
Among the sprays injected from the respective nozzle holes and adjacent to each other in the swirl flow direction, the swirl upstream side surface position of the spray located on the downstream side in the swirl flow direction and the swirl downstream side surface of the spray located on the upstream side in the swirl flow direction A fuel injection for an internal combustion engine, wherein at least one of a fuel injection condition of a fuel injection valve and a speed of a swirl flow is changed so that an interval with a position is within a predetermined range Control device. In a fuel injection control device for a compression ignition type internal combustion engine that includes a swirl control valve capable of controlling a swirl speed in a cylinder, and injects fuel from a plurality of nozzle holes of the fuel injection valve toward the cylinder,
In-cylinder state calculating means for calculating the in-cylinder density from the engine operating state;
Swirl speed calculating means for calculating the swirl speed from the engine operating state;
Spray characteristic calculation means for calculating the penetration, spray angle, and injection period of the spray injected from the fuel injection valve;
From the swirl speed and the spray characteristics, wall surface collision time calculating means for calculating the time until the spray collides with the wall surface in the combustion chamber,
Swirl downstream side surface calculating means for calculating a swirl downstream side surface position in the spray;
Swirl upstream side surface calculating means for calculating the side surface position of the swirl upstream side in the spray;
Spray interval calculation means for calculating an interval in the swirl flow direction between the sprays injected from the adjacent nozzle holes from the wall surface collision time, the swirl downstream side surface position, and the swirl upstream side surface position;
Interval determining means for determining whether or not the spray interval is within a predetermined range;
Injection condition correcting means for correcting a condition when the fuel injection valve injects spray;
A swirl control valve opening correction means for correcting the opening of the swirl control valve;
Based on the spray interval, at least one of the injection pressure, the injection timing, the maximum injection amount, the number of divisions, and the swirl control valve opening when the fuel injection valve injects the spray is changed. A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1 or 2,
When the time from the start of fuel injection from the nozzle hole until the spray of the fuel collides with the wall surface of the recessed portion of the piston top surface is less than the fuel injection period of the fuel injection valve, the swirl upstream side A configuration in which the side surface position and the swirl downstream side surface position are obtained, and at least one of the fuel injection condition of the fuel injection valve and the speed of the swirl flow is changed so that the interval between the side surface positions is within a predetermined range. A fuel injection control device for an internal combustion engine, characterized in that The fuel injection control device for an internal combustion engine according to claim 1, 2, or 3,
The swirl downstream side surface position is expressed by the following formula (1)
θL = (1/2) × spray angle + A × Vsw × time (1)
θL; swirl downstream side surface position Vsw; swirl speed tip; time until the spray collides with the wall surface in the combustion chamber A: calculated by the diffusion rate of the fuel spray toward the downstream in the swirl flow direction,
The swirl upstream side surface position is expressed by the following equation (2)
θU = (1/2) × spray angle (2)
θU is calculated from the swirl upstream side surface position,
The interval between the side surface positions is expressed by the following equation (3).
θD = (360 / number of nozzle holes) − (θL + θU) (3)
θD: A fuel injection control device for an internal combustion engine, characterized in that the fuel injection control device is calculated based on an interval between each side surface position. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4,
The fuel injection control of the internal combustion engine, wherein the fuel injection pressure from the fuel injection valve is increased when the distance between the swirl upstream side surface position and the swirl downstream side surface position is a predetermined value or more. apparatus. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4,
A fuel injection control device for an internal combustion engine, wherein when the sprays adjacent to each other partially overlap, the fuel injection from the fuel injection valve is divided into a plurality of times and executed. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4,
A fuel injection control device for an internal combustion engine, characterized in that when the distance between the swirl upstream side surface position and the swirl downstream side surface position is equal to or greater than a predetermined value, the speed of the swirl flow is increased. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4,
A fuel injection control device for an internal combustion engine, characterized in that when the adjacent sprays partially overlap each other, the speed of the swirl flow is reduced.

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