JP2018096216A - Fuel injection control device, internal combustion engine, and fuel injection control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device or the like enabled, by controlling a fuel injection properly, to suppress the occurrence of accidental fire or white smoke and to reduce the discharge of an unburned fuel.SOLUTION: A fuel injection control device controls a fuel injection to be performed by a fuel injection device disposed at each cylinder of an internal combustion engine. Said device deduces the fuel injection position of a pilot injection and the fuel injection position of a main injection. In the case that it is decided that those positions do not overlap, moreover, the injection timing of at least one of the pilot injection and the main injection is corrected so that the two positions may approach.SELECTED DRAWING: Figure 6

Description

  The present disclosure can be implemented by a fuel injection control device that controls fuel injection performed by a fuel injection device provided in each cylinder of the internal combustion engine, an internal combustion engine that includes the fuel injection control device, and the fuel injection control device. The present invention relates to a fuel injection control method.

  In an internal combustion engine such as an engine, power is obtained by injecting fuel into a cylinder from a fuel injection device provided in the cylinder and burning it. Such a fuel injection device is controlled by an electronic control device such as an ECU, and fuel injection is performed at a predetermined timing in each cycle. Various techniques have been studied for this type of fuel injection control. However, by performing at least one pilot injection prior to the main injection, the cooling of the internal combustion engine, for example, at the time of start-up or in a low-temperature environment is performed. What suppresses the occurrence of misfire under conditions where the water temperature is low is known.

  However, even if such pilot injection is performed, it is difficult to reliably avoid the occurrence of misfire in practice. In order to deal with such a problem, Patent Document 1 describes that the occurrence of misfire can be more effectively suppressed by setting the interval of pilot injection carried out a plurality of times longer than that in the conventional art.

Japanese Patent No. 5029501

  Such fuel injection control in the internal combustion engine is performed by controlling control parameters such as the fuel injection amount, the fuel injection pressure, the number of fuel injections, the fuel injection timing, etc. with respect to the target rotational speed or the target torque, for example. Further, in consideration of the influence on the performance of the internal combustion engine such as the use environment and the operating state, a predetermined correction may be performed on the control parameter. For example, it is conceivable to correct the control parameter according to the coolant temperature of the internal combustion engine.

  Conventionally, correction for such control parameters is based on a map that assumes a steady state, and a correction value corresponding to the target rotational speed or target torque is adopted. Therefore, the operation state changes to a transient state every moment. Is difficult to deal with. In particular, in an internal combustion engine equipped with a supercharger, when the load on the internal combustion engine changes abruptly, it is difficult to cope with the response of the supercharger due to a delay. As a result, the internal combustion engine is not properly operated in a transient state, and there is a risk that misfires, white smoke may occur, or the amount of unburned fuel discharged increases.

  At least one embodiment of the present invention has been made in view of the above circumstances, and by appropriately controlling fuel injection, it is possible to suppress the occurrence of misfire and white smoke even in a transient state, and to discharge unburned fuel. It is an object of the present invention to provide a fuel injection control device capable of reducing the above, an internal combustion engine including the fuel injection control device, and a fuel injection control method that can be implemented by the fuel injection control device.

(1) A fuel injection control device according to at least one embodiment of the present invention is a fuel injection control device that controls fuel injection performed by a fuel injection device provided in each cylinder of an internal combustion engine in order to solve the above problems. A fuel injection control unit that controls the fuel injection device to perform main injection and pilot injection prior to the main injection in one cycle, and pilot injection that estimates an injection fuel position of the pilot injection Position overlap for determining whether the fuel position estimation unit, the main injection fuel position estimation unit for estimating the injection fuel position of the main injection, and the injection fuel position of the pilot injection and the injection fuel position of the main injection overlap If the determination unit and the position overlap determination unit determine that the injected fuel position of the pilot injection and the injected fuel position of the main injection do not overlap Further, a correction unit that corrects at least one of the pilot injection and the main injection set by the injection fuel control unit so that the injection fuel position of the pilot injection and the injection fuel position of the main injection come closer to each other And comprising.

  According to the configuration of (1) above, main injection and pilot injection are performed during one cycle, and the respective injected fuel positions are estimated computationally. It is determined whether or not the fuel injection positions of the main injection and the pilot injection overlap each other by the position overlap determination unit. When both are overlapped, good ignitability is obtained, and correction by the correction unit is not performed. On the other hand, when the two do not overlap, the injection timing of at least one of the pilot injection and the main injection is corrected so that the two approach each other. Thereby, the ignitability is improved, the occurrence of misfire and white smoke is suppressed, and the discharge amount of unburned fuel can be reduced. Such correction by the correction unit is performed based on the injection fuel position estimated in terms of calculation, and thus is effective not only in the steady state but also in the transient state.

(2) In some embodiments, in the configuration of (1), the correction unit corrects the injection timing of the pilot injection without changing the injection timing of the main injection.

  According to the configuration of (2) above, the correction unit corrects only the injection timing of the pilot injection without changing the injection timing of the main injection. The injection timing of the main injection is generally controlled as a basic parameter for determining the target torque and the target rotational speed in accordance with the operating state of the internal combustion engine. Therefore, if correction is performed on the main injection by the correction unit, the basic control of the internal combustion engine may be affected. Therefore, the correction unit corrects only the pilot injection, whereby the above effect can be obtained while suppressing the influence on the basic control of the internal combustion engine.

  Further, since the pilot injection is performed in a state where the in-cylinder pressure is lower prior to the main injection, the fuel reach distance in the cylinder becomes long. In other words, the pilot injection is more sensitive to the same correction amount than the main injection. Therefore, by performing correction only for pilot injection, the above effect can be obtained more effectively than when correction is performed for main injection.

(3) In some embodiments, in the above configuration (1) or (2), a temperature sensor for detecting the supply air temperature of the internal combustion engine, and a supply air pressure of the internal combustion engine A pressure sensor, and the injection fuel position of the pilot injection and the injection fuel position of the main injection are obtained using an in-cylinder gas density calculated based on the supply air temperature and the supply air pressure. It is done.

  According to the configuration of (3) above, it is possible to estimate the in-cylinder gas density when the environmental conditions (air temperature, atmospheric pressure) change, so the accuracy of estimating the spray reach distance between the pilot injection and the main injection is increased. Thus, correction can be performed more effectively.

(4) In some embodiments, in the configuration of (1) or (2) above, a temperature sensor for detecting a supply air temperature of the internal combustion engine, and an in-cylinder pressure for detecting an in-cylinder pressure of the cylinder A fuel injection position of the pilot injection and an injection fuel position of the main injection are obtained using an in-cylinder gas density calculated based on the supply air temperature and the in-cylinder pressure. .

  According to the configuration of (4), the cylinder gas pressure at the main injection timing and the pilot injection timing and the cylinder gas density are estimated from the supply air pressure and the compression ratio, whereas the cylinder gas pressure is There is no need to estimate and the calculation load can be reduced. Thereby, fuel injection correction can be executed more quickly.

(5) In some embodiments, in any one of the configurations (1) to (4), the system further includes a transient state determination unit that determines whether or not the internal combustion engine is in a transient state. When the determination unit determines that the internal combustion engine is in a transient state, correction by the correction unit is performed.

  According to the configuration of (5) above, the correction by the correction unit is performed only when the internal combustion engine is in a transient state. Therefore, when the internal combustion engine is not in a transient state, correction by the correction unit is not performed. Thereby, misfire and white smoke can be effectively suppressed while efficiently reducing the calculation burden of the control device.

(6) In some embodiments, in any one of the configurations (1) to (5), the fuel injection control unit is configured to a map that defines a relationship between an operation state of the internal combustion engine and the injection timing. Based on this, the injection timing corresponding to the operating state of the internal combustion engine is obtained, and the correction unit corrects the injection timing obtained by the fuel injection control unit.

  According to the configuration of (6) above, the correction by the correction unit is performed on the injection timing obtained as a control parameter used in the normal control by the fuel injection control unit. Thereby, even if the injection timing calculated | required in a fuel-injection control part assumes a steady state, it can respond | correspond favorably also to a transient state by correction | amendment by a correction | amendment part.

(7) In some embodiments, in any one of the configurations (1) to (6), a supercharger is provided for supplying air to the internal combustion engine with overpressure.

  According to the configuration of (7) above, in an internal combustion engine equipped with a supercharger, when the load of the internal combustion engine changes suddenly in a transient state, there is a considerable delay in the response of the supercharger. Although white smoke is likely to be generated, these problems can be effectively solved by adopting the above-described configuration.

(8) In some embodiments, in any one of the configurations (1) to (7), the internal combustion engine is a compression ignition type.

  According to the configuration (8) above, the compression ignition type internal combustion engine has a relatively high in-cylinder pressure, and therefore it is particularly effective to apply the above configuration.

(9) In order to solve the above problems, an internal combustion engine according to at least one embodiment of the present invention includes the fuel injection control device having any one of the configurations (1) to (8).

  According to the configuration of (9) above, even when the internal combustion engine is in a transient state, it is possible to obtain good ignitability by suppressing separation of the fuel injection position of the pilot injection from the fuel injection position of the main injection. It is done. As a result, the occurrence of misfire and white smoke is suppressed even in a transient state, and a stable operation can be realized, and good fuel efficiency can be obtained by reducing the amount of unburned fuel discharged.

(10) A fuel injection control method according to at least one embodiment of the present invention is a fuel injection control method for controlling fuel injection performed by a fuel injection device provided in each cylinder of an internal combustion engine in order to solve the above problems. A fuel injection control step for controlling the fuel injection so as to perform main injection and pilot injection prior to the main injection in one cycle, and the pilot injection based on the injection timing of the pilot injection. A pilot injection fuel position estimation step for estimating an injection fuel position; a main injection fuel position estimation step for estimating an injection fuel position of the main injection based on an injection timing of the main injection; an injection fuel position of the pilot injection; The position overlap determination step for determining whether or not the fuel injection position of the main injection overlaps, and the position overlap determination step, the pi When it is determined that the fuel injection position of the fuel injection and the fuel injection position of the main injection do not overlap, the fuel injection position so that the fuel injection position of the pilot injection and the fuel injection position of the main injection approach each other A correction step of correcting an injection timing of at least one of the pilot injection and the main injection set by the control unit.

  The method (10) can be suitably implemented by the above-described fuel control device (including the various aspects described above).

  According to at least one embodiment of the present invention, by appropriately controlling fuel injection, a fuel injection control device capable of suppressing misfire and white smoke even in a transient state and reducing the amount of unburned fuel discharged. An internal combustion engine including the fuel injection control device and a fuel injection control method that can be implemented by the fuel injection control device can be provided.

It is a mimetic diagram showing the whole fuel injection control device composition concerning at least one embodiment of the present invention. FIG. 2 is a block diagram functionally showing an internal configuration of an ECU in FIG. 1. It is a time chart which shows the time change of the engine supply pressure, the excess air ratio, the fuel flow rate of the fuel injector, and the engine output in a transient state. It is a schematic diagram which shows the mode in a cylinder when a pilot injection fuel position and a main injection fuel position overlap. It is a schematic diagram which shows the mode in a cylinder when a pilot injection fuel position and a main injection fuel position do not overlap. It is a flowchart which shows the fuel-injection control method implemented with ECU of FIG. 1 for every process.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.
In addition, for example, expressions representing shapes such as quadrangular shapes and cylindrical shapes not only represent shapes such as quadrangular shapes and cylindrical shapes in a strict geometric sense, but also within the range where the same effect can be obtained. A shape including a chamfered portion or the like is also expressed.
On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

FIG. 1 is a schematic diagram showing an overall configuration of a fuel injection control device 1 according to at least one embodiment of the present invention. The fuel injection control device 1 controls an engine 10 that is an internal combustion engine that obtains power by burning fuel injected into a cylinder. In the present embodiment, a diesel engine that uses diesel oil as a fossil fuel as fuel and obtains power by compression ignition combustion is exemplified as the engine 10.
In FIG. 1, an in-line four cylinder type is shown as the engine 10, but the number of cylinders and the arrangement method of the cylinders are not limited thereto.

  Each cylinder of the engine 10 includes a combustion chamber (not shown) defined by a substantially cylindrical cylinder and a piston capable of reciprocating in the cylinder, and a fuel injector 12 for injecting fuel into these combustion chambers. Have each. Each fuel injector 12 is supplied with high pressure fuel via a common rail system 14. The common rail system 14 accumulates fuel boosted by a supply pump in a rail from a fuel tank in which fuel is stored, and an appropriate fuel is supplied to each cylinder in a timely manner by electronic control. Such fuel injection control for the fuel injector 12 is performed by the ECU 100 described later.

  The engine 10 has an intake passage 16 for taking in air Fi used for combustion in each cylinder from the outside. The intake passage 16 is configured to purify the air Fi with an air filter 20 provided in the vicinity of the inlet, and then distribute it to each cylinder via an intake manifold (not shown). In addition, a throttle valve 22 for adjusting an air supply amount is disposed in the intake passage 16.

  The engine 10 also has an exhaust passage 24 for exhausting exhaust gas Fe generated by combustion in each cylinder. An exhaust gas purification device 26 for purifying exhaust gas is installed in the exhaust passage 24. The exhaust purification device 26 includes, for example, an oxidation catalyst, a storage reduction type or selective reduction type NOx catalyst, and a DPF (Diesel Particulate Filter) for collecting particulate matter (eg, soot) in the exhaust gas. May be.

A turbocharger 30 having an exhaust turbine 28 that can be driven by exhaust gas Fe is provided upstream of the exhaust purification device 26 in the exhaust passage 24. The exhaust turbine 28 is connected to a compressor 34 disposed in the intake passage 16 via a connecting shaft 32. When the exhaust turbine 28 is rotationally driven by the high-temperature exhaust gas flowing through the exhaust passage 24, the compressor 34 rotates through the connecting shaft 32, and the air Fi taken into the intake passage 16 is compressed.
An intercooler 36 for cooling the air Fi compressed and heated by the compressor 34 is disposed in the intake passage 16 downstream of the compressor 34.

  One end of an EGR (Exhaust Gas Recirculation) passage 38 is connected to the exhaust passage 24 upstream of the exhaust turbine 28. The other end of the EGR passage 38 is connected to the intake passage 16 so that a part of the exhaust gas Fr returns to the intake passage 16. The EGR passage 38 is provided with an EGR valve 40 for controlling the flow rate of the reflux gas Fr flowing through the EGR passage 38. The opening degree of the EGR valve 40 is also electronically controlled by the ECU 100, and the flow rate of the exhaust gas Fr recirculated through the EGR passage 38 can be adjusted according to the operating conditions. Further, an EGR cooler 42 for cooling the exhaust gas Fr flowing through the EGR passage 38 is provided on the upstream side of the EGR valve 40 in the EGR passage 38.

  Further, a temperature sensor 44 and a pressure sensor 46 for detecting the temperature and pressure of the air sucked into the cylinder are provided downstream of the throttle valve 22 in the intake passage 16. Further, an excess air ratio sensor 48 for detecting an excess air ratio is provided in the cylinder of the engine 10 in the cylinder. An in-cylinder pressure sensor 49 for detecting the in-cylinder pressure is provided in the cylinder of the engine 10. The detection results of these sensors are sent to the ECU 100 described later as electrical signals and used for various arithmetic processes.

The ECU 100 is a control unit (electronic control unit) for electronically controlling each component of the fuel injection control device 1, and is configured by an arithmetic device using a semiconductor element, for example. Regarding the basic control of the engine 10 and the fuel injection control described later, the fuel injection control device 1 is realized by installing corresponding programs in advance.
ECU 100 may be provided in a known control unit such as an engine control ECU for controlling an existing engine, or may be provided separately as a new control unit.

FIG. 2 is a block diagram functionally showing the internal configuration of the ECU 100 of FIG. The ECU 100 includes a fuel injection control unit 102 that controls the fuel injector 12, a pilot injection fuel position estimation unit 104 that estimates pilot injection fuel position S _{pilot_center} by pilot injection, and a main injection fuel position S _{main_tip} that estimates main injection. The injection fuel position estimation unit 106, the transient state determination unit 108 that determines whether or not the operating state of the engine 10 is a transient state, and whether or not the pilot injection fuel position S _{pilot_center} and the main injection fuel position S _{main_tip} overlap. A position overlap determination unit 110 for determining, and a correction unit 112 for correcting at least one of the injection timing of the pilot injection and the main injection set by the fuel injection control unit 102.

  The fuel injection control unit 102 performs fuel injection control according to the operating conditions by controlling the fuel injector 12 of each cylinder. The fuel injection control unit 102 performs such fuel injection control using the number of fuel injections per cycle, the fuel injection amount, the fuel injection timing, the injection cone angle, and the like as control parameters. These control parameters are calculated based on a map prepared in advance based on actual measurement values or estimated values related to the operating state of the engine 10. Such a map is stored in advance in a storage device (not shown) such as a memory, and the fuel injection control unit 102 performs control corresponding to actual measurement values and estimated values obtained by various sensors and algorithms based on the map. Find the parameters.

Particularly in the present embodiment, the fuel injection control unit 102 controls the fuel injector 12 so as to perform main injection and at least one pilot injection performed prior to the main injection during one cycle. That is, the fuel injection control unit 102 performs fuel injection timing related to pilot injection (pilot injection start time t _pilot and pilot injection end time t _{pilot_end} ), fuel injection timing related to main injection (main injection start time t _main) , and main injection. By setting the end time _{tmain_end} ) as a control parameter, the fuel injector 12 is controlled to perform pilot injection and main injection.

The pilot injection fuel position estimation unit 104 estimates the injected fuel position S _{pilot_center} by pilot injection based on the control parameter set by the fuel injection control unit 102. Here, a method for estimating the injected fuel position S _{pilot_center} by pilot injection in the pilot injected fuel position estimating unit 104 will be specifically described.

As described above, the fuel injection control unit 102 sets the pilot injection start time t _pilot and the pilot injection end time t _{pilot_end} as control parameters related to pilot injection. The injected fuel position S _{pilot_center} by pilot injection is before pilot injection before the pilot injection start time (that is, t <t _pilot ), and therefore, the following expression S _{pilot_center} = 0 (1)
It becomes. On the other hand, after the pilot injection ends (that is, _{pilot_end} <t), the injected fuel position S _{pilot_center1} is _expressed by the following equation based on the model of Musculus et al.

It becomes. In addition, from the pilot injection start time to before the pilot injection end (that is, t _pilot ≦ t ≦ t _{pilot_end} ), the injected fuel position S _{pilot_center2} by the pilot injection is _expressed by the following equation:

It becomes.

Note that M _{0 —} pilot in the equations (2) and (3) is the kinetic energy possessed by the fuel injected by the pilot injection.

It is obtained with. R _{noz in the} equation (4) is a nozzle hole diameter of the injector. ρ _pilot is the in-cylinder gas density at the start of pilot injection, and is based on the in-cylinder volume V, the temperature sensor 44, the pressure sensor 46, the excess air ratio sensor 48, and the in-cylinder pressure sensor 49 defined according to the crank angle. Calculated numerically. V _inj is the fuel injection speed, and is obtained based on, for example, a command value for the common rail pressure.
Further, θ is an injection cone angle (spray spread angle) at the time of pilot injection of the fuel injector 12.

Here, the in-cylinder gas density ρ _pilot may be calculated based on the supply air temperature detected by the temperature sensor 44 and the supply air pressure detected by the pressure sensor 46. In this case, it becomes possible to estimate the in-cylinder gas density when the environmental conditions (temperature, pressure) change, so the estimation accuracy of the spray reach distance of the pilot injection and the main injection is improved, and the correction is made more effectively. It can be carried out.

The in-cylinder gas density ρ _pilot may be calculated based on the supply air temperature detected by the temperature sensor 44 and the in-cylinder pressure detected by the in-cylinder pressure sensor 49. In this case, the in-cylinder gas pressure and the in-cylinder gas density at the main injection timing and the pilot injection timing are estimated from the supply air pressure and the compression ratio, but it is not necessary to estimate the in-cylinder gas pressure. Can be suppressed. Thereby, fuel injection correction can be executed more quickly.

By the way, the in-cylinder pressure changes every moment, and when the pilot injection is performed, the in-cylinder pressure gradually increases as time elapses. Therefore, fuel injected at an early timing among pilot injections is released during a low in-cylinder pressure, and therefore has a higher injection speed than a fuel injected at a later timing and a longer reach in the cylinder. Tend. Therefore, the injection fuel position S _{pilot_center2} calculated by the equation (3) during the pilot injection (t _pilot ≦ t ≦ t _{pilot_end} ) is calculated by the equation (2) after the pilot injection ends (that is, _{pilot_end} <t). There is a case where the fuel position S _{pilot_center1} is overtaken. Therefore, the pilot injected fuel position estimating unit 104 continues the injected fuel position S _{pilot_center} until the injected fuel position S _{pilot_center2} calculated by the expression (3) _{exceeds the} injected fuel position S _{pilot_center1} calculated by the expression (2). Expression S _{pilot_center} = S _{pilot_center1} (5)
Estimated. On the other hand, (3) After overtaking the injected fuel position _{S Pilot_center1} the injected fuel position _{S Pilot_center2} calculated is calculated by equation (2) by the equation, the following equation injection fuel position _{S pilot_center S pilot_center = S pilot_center3 (} 6 )
Estimated. here,


It is. In this manner, the pilot injection fuel position estimation unit 104 can accurately estimate the injection fuel position of pilot injection in consideration of the change in the in-cylinder pressure.

Subsequently, the main injection fuel position estimation unit 106 estimates the injection fuel position S _{main_tip} due to the main injection based on the control parameter relating to the main injection obtained by the injection control unit 102. Here, a method for estimating the injected fuel position S _{main_tip} by the main injection in the main injected fuel position estimating unit 106 will be specifically described.

As described above, the fuel injection control unit 102 sets the main injection start time t _main and the main injection end time t _{main_end} as control parameters relating to the main injection. The fuel injection position S _{main_tip due} to the main injection is before the main injection is performed before the main injection start time (that is, t <t _main ), and therefore, the following expression S _{main_tip} = 0 (9)
It becomes. On the other hand, after the main injection ends (that is, t _{main_end} <t), the injected fuel position S _{main_tip} is _expressed by the following equation according to the above (3).


It is estimated to be.

It should be noted that the cylinder gas density ρ _main at the time of main injection used in the equation (10) is also determined by the supply air temperature detected by the temperature sensor 44 and the pressure sensor 46 in the same manner as the cylinder gas density ρ _pilot. It may be calculated based on the detected supply air pressure, or may be calculated based on the supply air temperature detected by the temperature sensor 44 and the in-cylinder pressure detected by the in-cylinder pressure sensor 49.

Subsequently, the transient state determination unit 108 determines whether or not the operating state of the engine 10 is a transient state. Here, FIG. 3 shows the supply pressure of the engine 10 (detected value of the pressure sensor 46), the excess air ratio (detected value of the excess air ratio sensor 48), the fuel flow rate Q _inj of the fuel injector 12, and the output of the engine 10 in the transient state. It is a time chart which shows a time change. In this example, as shown in FIG. 3D, the operating state of the engine 10 changes transiently so that the output changes from P0 to P1 from time t0 to time t1. In the transient state in which the output increases in this way, the supply air pressure of the engine 10 increases as shown in FIG. 3A, the excess air ratio in the cylinder decreases as shown in FIG. The fuel flow rate of the fuel injector 12 changes so as to increase as shown in FIG. These changes require a certain amount of time from time t0 to time t1.

  The transient state determination unit 108 monitors at least one state parameter in order to determine such a transient state of the engine 10. In the present embodiment, the air pressure detected by the pressure sensor 46 described above, the excess air ratio in the cylinder detected by the excess air ratio sensor 48, the indicated value of the fuel flow rate transmitted to the ECU 100 fuel injector 12, and the ECU 100 Monitoring at least one of the indication values of the output request input to. For the monitored state parameter, the rate of change from time t0 to t1 is calculated, and when the rate of change exceeds a predetermined value, it is determined that the state is in a transient state.

The position overlap determination unit 110 determines whether or not the pilot injection fuel position S _{pilot_center} estimated by the pilot injection fuel position estimation unit 104 and the main injection fuel position S _{main_tip} estimated by the main injection fuel position estimation unit 106 overlap. judge. Here, FIG. 4 is a schematic view showing the inside of the cylinder when the pilot injection fuel position S _{pilot_center} and the main injection fuel position S _{main_tip} overlap, and FIG. 5 is the pilot injection fuel position S _{pilot_center} and the main injection fuel position S _{main_tip.} It is a schematic diagram which shows the mode in a cylinder when and do not overlap.

4 and 5, the injected fuel (one-dot chain line) 50 by the pilot fuel and the injected fuel (solid line) 52 by the main injection are schematically shown with respect to the center O in the cylinder. Also the injected fuel position _{S Pilot_center} pilot injection estimated by pilot injection fuel position estimating unit 104, and the injected fuel position _{S Main_tip} of main injection which is estimated in the main injection fuel position estimation unit 106 is expressed in total. The injected fuel positions S _{pilot_center} and S _{main_tip} indicate radial distances with the center O in the cylinder as a reference point.

In Figure 4, the reference point O, the injected fuel position _{S Pilot_center} pilot injection becomes closer than the injected fuel position _{S Main_tip} of the main injection. In such a case, the position overlap determination unit 110 determines that the injected fuel for pilot injection and the injected fuel for main injection overlap. In the state shown in FIG. 4, the ignitability of the injected fuel of the main injection is improved by the pilot injection. As a result, it is possible to effectively prevent misfire and white smoke from being easily generated due to ignition delay and lean combustion, and increase in the amount of unburned fuel discharged.

On the other hand, in FIG. 5, the reference point O, the injected fuel position _{S Pilot_center} pilot injection becomes far from the injected fuel position _{S Main_tip} of the main injection. In such a case, the position overlap determination unit 110 determines that the injected fuel for pilot injection and the injected fuel for main injection do not overlap. In the state as shown in FIG. 5, the ignitability in the cylinder is lowered. As a result, misfire or white smoke is likely to occur due to ignition delay or lean combustion, and the amount of unburned fuel discharged increases.

The correction unit 112 corrects at least one of the pilot injection timing and the main injection timing set by the fuel injection control unit 102. Such correction, the injected fuel position _{S Pilot_center} pilot injection is carried out so as to approach and the injected fuel position _{S Main_tip} of the main injection. The correction unit 112 may perform correction so as to change the injection timing of the pilot injection while fixing the injection timing of the main injection, or change the injection timing of the main injection while fixing the injection timing of the pilot injection. You may correct | amend so that it may carry out, or you may correct | amend so that both pilot injection and main injection may be changed.

  By the way, in the transient state as shown in FIG. 3, the operating state of the engine 10 changes every moment. In the operation control of the engine 10, in order to optimize the operation state, for example, correction based on a use environment affecting the performance of the engine 10 and a parameter reflecting the operation state (for example, cooling water temperature) is performed. In the conventional correction, a map that defines the correction value associated with the driving state is prepared in advance, and the correction value corresponding to the driving state is used. However, since such a correction value is obtained based on a map assuming that the engine 10 is in a steady state, it is difficult to cope with a transient state in which the operating state changes with time. In particular, in the engine 10 provided with the supercharger 30 as shown in FIG. 1, the above problem becomes remarkable because there is a considerable delay in the response of the supercharger 30 when a transient state occurs.

In the transient state, as shown in FIG. 3, the supply air pressure is low at time t0 and rises with time. Therefore, fuel injected by pilot injection is injected at a lower in-cylinder pressure than fuel injected by main injection, which is performed later in time, and therefore has a higher injection speed and a farther reach. As a result, as shown in FIG. 5, the fuel injection position S _{pilot_center} of the pilot injection and the fuel injection position S _{main_tip} of the main injection are separated from each other, the ignitability is deteriorated, and misfiring is caused by the ignition delay or lean combustion. And white smoke may be generated, and the amount of unburned fuel may increase.

  As described above, in the prior art, it is difficult to obtain good ignitability in a transient state, but such a problem can be solved by a fuel injection control method implemented by the ECU 100 having the above-described configuration as described below. is there. FIG. 6 is a flowchart showing a fuel injection control method executed by ECU 100 of FIG.

First, the fuel injection control unit 102 of the ECU 100 sets control parameters related to pilot injection and main injection based on the operating state of the engine 10 (step S1). In the following description, among the control parameters set by the fuel injection control unit 102, only the injection timing related to pilot injection and main injection will be described. However, other control parameters are also controlled based on the same technical idea. May be. Specifically, the fuel injection control unit 102 sets the start timing t _pilot and the end timing t _{pilot_end} of the pilot injection, and the start timing t _main and the end timing t _{main_end} of the main injection.

  Subsequently, the transient state determination unit 108 determines whether or not the engine 10 is in a transient state based on the operating state of the engine 10 (step S2). Specifically, as shown in FIG. 4, the transient state determination unit 108 detects the detected value (supply pressure) of the pressure sensor 46, the detected value (excess air rate) of the excess air rate sensor 48, and the fuel injection control unit 102. A change rate is calculated for at least one of the indicated value of the fuel flow rate transmitted to the fuel injector 12 and the indicated value of the output request to the engine 10, and when the change rate exceeds a predetermined value, a transient state is obtained. It is determined that

  When the transient state determination unit 108 determines that the engine 10 is not in a transient state (step S2: NO), the ECU 100 performs normal control (step S8). In this normal control, the fuel injection control is performed based on the control parameter set in step S1, but in the steady state, the ignitability of the main injection can be satisfactorily obtained by pilot injection. Further, when the engine 10 is not in a transient state, correction by the correction unit 112 is not performed, so that misfire and white smoke can be effectively suppressed while efficiently reducing the calculation burden on the ECU 100.

On the other hand, when the transient state determination unit 108 determines that the engine 10 is in the transient state (step S2: YES), the pilot injection fuel position estimation unit 104 estimates the injected fuel position S _{pilot_center} by the pilot injection ( In step S3), the main fuel injection position estimation unit 106 estimates the main fuel injection fuel position _{Smain_tip} (step S4).
The estimation methods by the pilot injection fuel position estimation unit 104 and the main injection fuel position estimation unit 106 are as described above.

Subsequently, the position overlap determination unit 110 determines whether or not the pilot injection fuel position S _{pilot_center} estimated in step S4 and the main injection fuel position S _{main_tip} estimated in step S5 overlap (step S5). As a result, as shown in FIG. 4, when the pilot injected fuel position S _{pilot_center} and the main injected fuel position S _{main_tip} overlap (step S5: YES), good ignitability is obtained even in a transient state. (Step S8). That is, in this case, correction by the correction unit 112 is not performed.

On the other hand, as shown in FIG. 5, when the pilot injected fuel position S _{pilot_center} and the main injected fuel position S _{main_tip} do not overlap (step S5: NO), correction by the correction unit 112 is performed (step S6). The correction by the correction unit 112 is performed on at least one of the main injection and the pilot injection so that the pilot injection fuel position S _{pilot_center} and the main injection fuel position S _{main_tip} are close to each other. Thereby, the ignitability in a cylinder improves.

As shown in FIG. 4, the correction amount by the correction unit 112 may be set so that the pilot injection fuel position S _{pilot_center} and the main injection fuel position S _{main_tip} overlap each other. Thereby, the ignitability in a cylinder improves more. From the viewpoint of improving the ignitability, it is preferable that the degree of overlap between the pilot injected fuel position S _{pilot_center} and the main injected fuel position S _{main_tip} is large (the best is 100%), but the operation state by correcting the injection timing is improved. Considering the influence, it is better to make a comprehensive decision.

  Particularly in the present embodiment, the correction unit 112 corrects the injection timing of the pilot injection without changing the injection timing of the main injection. The injection timing of the main injection is controlled as a basic parameter for determining the target torque and the target rotation speed according to the operating state of the engine 10. Therefore, if the correction unit 112 corrects the main injection, the basic control of the engine 10 may be affected. Therefore, the correction unit 112 corrects only the pilot injection, whereby the above effect can be obtained while suppressing the influence on the basic control of the engine 10.

  Further, as described above, pilot injection is performed in a state where the in-cylinder pressure is lower prior to main injection, so that the fuel reach distance in the cylinder becomes long. In other words, the pilot injection is more sensitive to the same correction amount than the main injection. Therefore, by performing correction only for pilot injection, the above effect can be obtained more effectively than when correction is performed for main injection. This means that the correction amount for the entire fuel injection control can be suppressed, which is preferable from the viewpoint of suppressing the influence on the basic control of the engine 10.

The fuel injection control unit 102 performs fuel injection control based on the control parameter corrected in step S7 (step S7). Thereby, the main injection and the pilot injection are performed so that the main injection fuel position S _{pilot_center} and the main injection fuel position S _{main_tip} are close to each other, and good ignitability is obtained in the cylinder. As a result, even when the engine 10 is in a transient state, it is possible to effectively prevent misfire and white smoke from being easily generated due to ignition delay and lean combustion, and increase in the amount of unburned fuel.

  As described above, according to the present embodiment, by appropriately controlling the fuel injection, fuel injection control capable of suppressing misfire and white smoke even in a transient state and reducing the amount of unburned fuel discharged. Apparatus, an internal combustion engine provided with the fuel injection control device, and a fuel injection control method that can be implemented by the fuel injection control device.

  In particular, in the engine 10 including the supercharger 30, when the load of the engine 10 changes suddenly in a transient state, the response of the supercharger 30 is delayed, and misfire or white smoke is likely to occur. By adopting the above-described configuration, these problems can be effectively solved. In addition, when the engine 10 is of a compression ignition type such as a diesel engine, it has a relatively high in-cylinder pressure, so that the above configuration is particularly effective.

  At least one embodiment of the present invention is directed to a fuel injection control device that controls fuel injection performed by a fuel injection device provided in each cylinder of the internal combustion engine, an internal combustion engine that includes the fuel injection control device, and the fuel injection control. The present invention can be used for a fuel injection control method that can be implemented by the apparatus.

DESCRIPTION OF SYMBOLS 1 Fuel injection control apparatus 10 Engine 12 Fuel injector 14 Common rail system 16 Intake passage 20 Air filter 22 Throttle valve 24 Exhaust passage 26 Exhaust purification device 28 Exhaust turbine 30 Supercharger 32 Connecting shaft 34 Compressor 36 Intercooler 38 EGR passage 40 EGR valve 42 EGR cooler 44 Temperature sensor 46 Pressure sensor 48 Excess air ratio sensor 49 In-cylinder pressure sensor 100 ECU
102 fuel injection control unit 104 pilot injection fuel position estimation unit 106 main injection fuel position estimation unit 108 transient state determination unit 110 position overlap determination unit 112 correction unit

Claims (10)

A fuel injection control device for controlling fuel injection performed by a fuel injection device provided in each cylinder of an internal combustion engine,
A fuel injection control unit that controls the fuel injection device to perform main injection and pilot injection prior to the main injection during one cycle;
A pilot injection fuel position estimation unit that estimates an injection fuel position of the pilot injection;
A main injection fuel position estimation unit for estimating an injection fuel position of the main injection;
A position overlap determination unit that determines whether the injected fuel position of the pilot injection and the injected fuel position of the main injection overlap;
When the position overlap determination unit determines that the injected fuel position of the pilot injection and the injected fuel position of the main injection do not overlap, the injected fuel position of the pilot injection approaches the injected fuel position of the main injection. As described above, a correction unit for correcting the injection timing of at least one of the pilot injection and the main injection set by the injected fuel control unit,
A fuel injection control device.   The fuel injection control device according to claim 1, wherein the correction unit corrects the injection timing of the pilot injection without changing the injection timing of the main injection. A temperature sensor for detecting a supply air temperature of the internal combustion engine;
A pressure sensor for detecting a supply air pressure of the internal combustion engine;
Further comprising
The injection fuel position of the pilot injection and the injection fuel position of the main injection are obtained using an in-cylinder gas density calculated based on the supply air temperature and the supply air pressure. The fuel injection control device described. A temperature sensor for detecting a supply air temperature of the internal combustion engine;
An in-cylinder pressure sensor for detecting an in-cylinder pressure of the cylinder;
Further comprising
The injection fuel position of the pilot injection and the injection fuel position of the main injection are obtained using in-cylinder gas density calculated based on the supply air temperature and the in-cylinder pressure. The fuel injection control device described. A transient state determination unit for determining whether or not the internal combustion engine is in a transient state;
5. The fuel injection control device according to claim 1, wherein when the internal combustion engine is determined to be in a transient state by the transient state determination unit, the correction by the correction unit is performed. The fuel injection control unit obtains the injection timing corresponding to the operation state of the internal combustion engine based on a map that defines a relationship between the operation state of the internal combustion engine and the injection timing;
6. The fuel injection control device according to claim 1, wherein the correction unit corrects the injection timing obtained by the fuel injection control unit.   The fuel injection control device according to any one of claims 1 to 6, further comprising a supercharger for supplying air to the internal combustion engine with overpressure.   The fuel injection control device according to any one of claims 1 to 7, wherein the internal combustion engine is of a compression ignition type.   An internal combustion engine comprising the fuel injection control device according to any one of claims 1 to 8. A fuel injection control method for controlling fuel injection performed by a fuel injection device provided in each cylinder of an internal combustion engine,
A fuel injection control step of controlling the fuel injection so as to perform main injection and pilot injection prior to the main injection during one cycle;
A pilot injection fuel position estimation step of estimating an injection fuel position of the pilot injection based on an injection timing of the pilot injection;
A main injection fuel position estimation step for estimating an injection fuel position of the main injection based on an injection timing of the main injection;
A position overlap determination step of determining whether or not the fuel injection position of the pilot injection and the fuel injection position of the main injection overlap;
When it is determined in the position overlap determination step that the injected fuel position of the pilot injection and the injected fuel position of the main injection do not overlap, the injected fuel position of the pilot injection and the injected fuel position of the main injection approach each other. A correction step of correcting at least one of the pilot injection and the main injection set by the injected fuel control unit,
A fuel injection control method.