JP2014015907A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device and a control method of promoting vaporization of fuel by preheating the fuel before start-up, and suppressing an increase in unburned gases and particulates due to enhanced fuel penetration caused by the preheating, which is used for a cylinder injection type internal combustion engine.SOLUTION: In a fuel-preheating mode before start-up of an internal combustion engine, a fuel pressure in a common rail is measured or estimated and a fuel injection timing is corrected depending on the fuel pressure at start-up of the internal combustion engine to restrain the fuel spray injected from a fuel injection valve from colliding with a piston crown surface, which can suppress an increase in unburned gases and particulates during combustion.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that controls the operating state of the internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine that directly injects fuel into a cylinder of the internal combustion engine.

  In a cylinder injection type internal combustion engine having a fuel injection valve for directly injecting fuel into a cylinder of the internal combustion engine, the fuel pressure is increased from a fuel injection valve to a cylinder by pressurizing the fuel pressure to a high predetermined fuel pressure, for example, 5 to 20 MPa. By injecting the fuel into the interior, the fuel vaporization is promoted and a homogeneous air-fuel mixture is formed to improve exhaust performance and fuel efficiency.

  In such an in-cylinder internal combustion engine, the injected fuel may adhere to the piston crown depending on the fuel injection timing, and the attached fuel is sufficiently vaporized before being ignited by the spark plug. Otherwise, unburned gas (HC) and particulate matter (PM / PN) during combustion increase.

  Further, unburned gas and particulate matter further increase at the time of low water temperature when the piston crown surface is not sufficiently warmed or at the time of starting.

  Therefore, the fuel to be injected is heated by heating means such as a heater to promote the vaporization of the injected fuel, the amount of fuel adhering to the piston crown surface is reduced, and unburned gas and particulates at the time of low water temperature and starting It is important to suppress the increase in substances.

  Furthermore, when the fuel is heated, the vaporization time of the injected fuel tends to be shorter and the penetration of the injected fuel tends to be shorter than when the fuel is not heated. It is also important to adjust.

  In Japanese Patent Laid-Open No. 2005-291132 (Patent Document 1), as a technique for improving the exhaust performance by promoting the vaporization of fuel at the time of starting, the fuel injected by the fuel injection valve is heated by a heater to improve the vaporization performance. In addition to improving, a technique for adjusting the fuel injection timing within the range from the exhaust stroke to the intake stroke in order to secure the vaporization time for the fuel to stay in the intake manifold depending on the fuel temperature is proposed. Since the technique proposed in Patent Document 1 is a port injection system (a system in which a fuel injection valve is attached to an intake manifold), problems such as the above-described in-cylinder injection system internal combustion engine are considered. It is not.

JP 2005-291132 A

  By the way, when fuel is heated in a direct injection internal combustion engine, unburned gas at the time of combustion is changed by changing the fuel injection amount and the injection timing according to the fuel temperature in the normal operation region after the internal combustion engine is started. And the generation of particulate matter can be suppressed, and a control technology for this has been established.

  Further, in the normal operation region after starting the internal combustion engine, the fuel pressure to be injected is always feedback-controlled to the target value by high-pressure pump control, so that further correction control for the fuel pressure is not so required.

  However, when the fuel is preheated (preheated) before the internal combustion engine is started, the pressure in the common rail between the high pressure pump and the fuel injection valve rises with temperature because the common rail is sealed. Here, preheating is a control in which an electric heating means is provided on the common rail and the fuel in the common rail is heated prior to starting.

  For this reason, the fuel pressure injected at the start of the internal combustion engine increases, the penetration of the fuel injected from the fuel injection valve (the distance reached by the fuel penetration force) increases, and the fuel easily collides with the piston crown surface. There is a phenomenon that causes an increase in unburned gas and particulate matter at the start.

  An object of the present invention is to provide a fuel injection control device for an internal combustion engine that promotes fuel vaporization by preheating before starting and suppresses an increase in unburned gas and particulate matter due to an increase in penetration based on the fuel. There is.

  The feature of the present invention is that the fuel pressure in the common rail is measured or estimated in the mode in which the fuel is preheated before starting the internal combustion engine, and the fuel injection timing is corrected according to the fuel pressure when starting the internal combustion engine. Thus, the fuel injected from the fuel injection valve is prevented from colliding with the piston crown surface.

  According to the present invention, since the fuel injection timing is changed according to the fuel pressure at the start of the internal combustion engine, it is possible to reduce the collision of the fuel with the piston crown due to the increase in the penetration of the injected fuel accompanying the increase in the fuel pressure. The increase in unburned gas and particulate matter during combustion can be suppressed.

1 is an overall configuration diagram of a control system for a direct injection internal combustion engine to which the present invention is applied. It is a block diagram which shows the internal combustion engine control unit input / output signal relationship shown in FIG. It is a control flowchart figure explaining fuel injection control at the time of starting which becomes one example of the present invention. It is a characteristic view explaining the fuel pressure behavior from the start of fuel preheating to the start and complete explosion of the internal combustion engine according to one embodiment of the present invention. It is explanatory drawing explaining the relationship of the penetration of the injection fuel regarding a fuel pressure and fuel temperature. It is explanatory drawing explaining the relationship of the fuel particle size regarding a fuel pressure and fuel temperature. It is explanatory drawing explaining the discharge behavior of the unburned gas and particulate matter at the time of start-up of the internal combustion engine with respect to fuel pressure. It is explanatory drawing explaining the discharge behavior of the unburned gas at the time of start-up of an internal combustion engine with respect to fuel injection timing, and a particulate matter. It is a 1st time chart explaining fuel injection control at the time of starting which becomes one example of the present invention. It is a 2nd time chart figure explaining the fuel-injection control at the time of the start which becomes one Example of this invention. It is a 3rd time chart explaining the fuel injection control at the time of the start which becomes one Example of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and application examples are included in the technical concept of the present invention. Is also included in the range.

  An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of a control system for a direct injection internal combustion engine 1.

  In FIG. 1, the intake air taken in from the inlet of the air cleaner 102 passes through an intake air flow meter (air flow sensor) 103, passes through an electric throttle valve 104 that controls the intake air flow rate, and is connected to each cylinder. After being distributed to the pipe 105, it is introduced into the combustion chamber 106 through the intake valve 119 of each cylinder.

  A signal representing the intake air flow rate is output from the intake air flow meter 103 to the internal combustion engine control unit 101. A throttle opening sensor 107 for detecting the opening is attached to the electric throttle valve 104, and its signal is also output to the internal combustion engine control unit 101.

  The fuel stored in the fuel tank is primarily pressurized by a low-pressure fuel pump (not shown) and then secondarily pressurized to a higher pressure by the high-pressure fuel pump 108 and provided to each cylinder via the common rail 117. The fuel injection valve 109 is injected into the combustion chamber 106.

  A fuel heater 112 is attached to the common rail 117 and heats the fuel in the common rail based on a signal from the internal combustion engine control unit 101. A fuel temperature sensor 113 and a fuel pressure sensor 114 are attached to the common rail 117, and signals thereof are output to the internal combustion engine control unit 101.

  The fuel injected into the combustion chamber 106 generates an air-fuel mixture with the intake air, is ignited by the ignition plug 111 by the ignition energy from the ignition coil 110, and burns in the combustion chamber 106.

  The exhaust gas discharged from the combustion chamber 106 is discharged to the exhaust pipe 118, and the air-fuel ratio of the exhaust gas is measured by the air-fuel ratio sensor 203 attached to the exhaust pipe 118 and is output to the internal combustion engine control unit 101.

  A water temperature sensor 202 is attached to the cooling water passage of the cylinder block of the internal combustion engine, and this signal is output to the internal combustion engine control unit 101.

  A signal representing the rotational position of the crankshaft is output to the internal combustion engine control unit 101 by a crank angle sensor 116 attached to the crankshaft 115 of the internal combustion engine.

  Similarly, a signal representing the rotational position of the cam shaft is output to the internal combustion engine control unit 101 by a cam angle sensor 121 attached to the cam shaft 120 of the internal combustion engine.

  Next, the configuration of the internal combustion engine control unit 101 will be described with reference to FIG. The internal combustion engine control unit 101 includes an I / O LSI 101a including an A / D converter, a CPU 101b, and the like.

  The I / O LSI 101a includes signals from various sensors including an airflow sensor 103, a throttle sensor 107, a cam angle sensor 121, a crank angle sensor 116, a water temperature sensor 202, an air-fuel ratio sensor 203, a fuel temperature sensor 113, and a fuel pressure sensor 114. Is input and taken into the CPU 101b.

  The CPU 101b executes predetermined calculation processing from the acquired sensor signal and outputs various control signals calculated as calculation results to the I / O LSI 101a.

  The I / OLSI 101a supplies predetermined control signals to the electric throttle valve 104, the high pressure pump solenoid 206, the ignition coil 110, the low pressure fuel pump 207, each fuel injection valve 109, and the fuel heater 112, which are actuators, and the fuel pressure in the common rail. Control, fuel injection amount control, ignition timing control, and the like are executed.

  The I / O LSI 101a is provided with a drive circuit for driving each fuel injection valve, and a voltage supplied from the battery is boosted and supplied by a booster circuit (not shown), and current is supplied by a drive IC (not shown). Each fuel injection valve is driven by controlling.

  Next, the specific contents of the injection control of the internal combustion engine according to the embodiment of the present invention will be described with reference to the fuel injection timing flowchart shown in FIG. The control shown in this flowchart is an intake process injection method in which fuel injection is performed in the intake process.

  Although not described in this flowchart, the fuel injection amount at the start of the internal combustion engine is basically at least one of the rotational speed, water temperature, fuel temperature, target fuel pressure, cranking elapsed time, intake air amount, etc. of the internal combustion engine. Calculated with one or more parameters.

  In this embodiment, the fuel injection timing at the start of the internal combustion engine is calculated by the following implementation method.

  The fuel injection timing is basically calculated from at least one parameter such as the internal combustion engine speed, water temperature, intake air amount, etc., and when the fuel is heated, the fuel temperature is also used to calculate the fuel injection timing. Used. This fuel injection timing is a reference fuel injection timing, and this reference fuel injection timing is corrected by a fuel pressure that varies due to preheating at the time of starting.

  Further, a reference fuel injection timing at a fixed time may be set without using the above-described parameters, and the reference fuel injection timing may be corrected with a fuel pressure that varies due to preheating at the start.

  In short, it is only necessary to correct the reference fuel injection timing with the fuel pressure that fluctuates due to preheating at the time of starting, and to reduce the collision of the fuel with the piston crown due to the increase in the penetration of the injected fuel accompanying the increase in the fuel pressure.

  In FIG. 3, if the fuel preheating execution condition is satisfied in step 200 (hereinafter, “step” is abbreviated as “S”) before the internal combustion engine is started, the routine proceeds to S201 where fuel preheating is executed and the fuel in the common rail 117 is Start heating the fuel. The condition for heating the fuel in the common rail 117 is typically the fuel temperature before starting. If the temperature is lower than the predetermined temperature before starting, the fuel is heated. If the temperature is higher than the predetermined temperature, the process proceeds to S202. Normal start control is performed.

  When preheating of the fuel is executed in S201 to start heating the fuel in the common rail 117, the process proceeds to S202, and a starter (not shown) is operated to start the internal combustion engine.

  When the internal combustion engine is started in S202, the process proceeds to S203, and the fuel pressure in the common rail 117 is measured by the fuel pressure sensor 114. In this case, since the fuel pressure in the common rail 117 increases due to heating, it is important to always detect an increasing fuel pressure that is different from the behavior of the fuel pressure during normal startup.

  Next, when the measurement of the fuel pressure is completed, the process proceeds to S204, and the calculation of the fuel injection timing is executed in accordance with the measured fuel pressure. In the calculation of the fuel injection timing, when the fuel preheating execution condition is not satisfied in S200, the reference fuel injection calculated based on one or more parameters such as the rotational speed of the internal combustion engine, the water temperature, the intake air amount, the fuel temperature, and the like. Seeking timing. Even in this case, since the fuel pressure is measured, it is possible to perform correction control of the fuel pressure that changes due to fuel injection.

  On the other hand, when the fuel preheating execution condition is satisfied in S200, the reference fuel injection timing calculated based on one or more parameters such as the rotational speed of the internal combustion engine, the water temperature, the intake air amount, the fuel temperature, or a predetermined fixed The corrected reference fuel injection timing is obtained by correcting the reference fuel injection timing corresponding to the increase in fuel pressure caused by the fuel preheating measured in S203.

  As a condition for executing the correction, the above-described correction is performed when the measured fuel pressure exceeds a predetermined determination fuel pressure. In this way, since the same fuel pressure is compared, the control logic and calculation are simplified.

  This correction tends to correct the fuel injection timing so that the higher the fuel pressure is, the more the fuel is injected on the intake bottom dead center side of the piston. That is, fuel injection is executed at a point in the direction in which the distance between the fuel injection valve 109 and the piston crown surface becomes longer as the penetration becomes longer.

  As a result, the distance between the fuel injection valve 3 and the piston crown surface is increased and changed in accordance with the increase in penetration, so that the fuel collision can be efficiently reduced.

  Note that the fuel pressure in the common rail 117 gradually decreases because the high-pressure pump is not fully functioning and the fuel is injected from the fuel injection valve 109 in each combustion cycle until the internal combustion engine is completely detonated. Conversely, the fuel pressure tends to increase with heating. Therefore, it is important to always measure the fuel pressure during startup of the internal combustion engine and calculate the fuel injection timing for each fuel injection from the fuel injection valve 109 corresponding to the change in the fuel pressure.

  When the fuel injection timing is obtained in S204, the process proceeds to S205 to execute a process of injecting fuel from the fuel injection valve 109.

  In this fuel injection process, the fuel injection amount at the start is calculated by at least one parameter such as the rotational speed of the internal combustion engine, water temperature, fuel temperature, target fuel pressure, cranking elapsed time, intake air amount, etc. Fuel is injected for a time corresponding to the fuel injection amount at the fuel injection timing.

  Then, when fuel is injected in S205, the process proceeds to S206 to determine whether or not the internal combustion engine has completely exploded. If not, the process returns to S200 and the same process is repeated. The determination of complete explosion is determined as complete explosion when the rotational speed is equal to or higher than a predetermined rotational speed.

  If it is determined in S206 that the complete explosion has occurred, the start injection control according to this flowchart is terminated, and the routine proceeds to fuel injection control in the normal operation range. In this case, the fuel pressure is sufficiently secured, so that the target fuel pressure feedback control by the high pressure pump is started.

  Note that an increase in penetration due to an increase in fuel pressure due to preheating becomes a problem when the number of injections is about 1 to 5 times in the initial stage of the start, so basically the fuel injection timing in the initial stage of the start may be corrected. Of course, the fuel pressure may be corrected in the subsequent injection.

  Next, specific contents of the above-described injection control of the internal combustion engine will be described. The behavior of the fuel pressure in the common rail at the time of preheating the fuel that heats the fuel before starting the internal combustion engine will be described with reference to FIG.

  The fuel pressure in the common rail 117 before the start of fuel preheating is a pressure pressurized by a low-pressure pump (not shown) or a residual pressure remaining on the common rail when the internal combustion engine was stopped last time.

  When the fuel preheating condition is satisfied at time t0 and heating of the fuel is started, the fuel temperature in the common rail 117 rises with time, but the fuel in the common rail 117 is in a sealed state, so that the fuel pressure is also increased. It rises with it. The rate of increase in the fuel temperature and fuel pressure varies depending on the heat generation characteristics of the heater, its control method, the amount of fuel in the common rail, the temperature, and the like.

  When starting is started at time t1, the fuel in the common rail 117 is injected into the combustion chamber of the internal combustion engine for each combustion cycle by the fuel injection valve 109, so that the fuel pressure in the common rail 117 gradually decreases, and time t2 After the complete explosion of the internal combustion engine shown in Fig. 5, feedback control is performed to the target fuel pressure by a high-pressure pump that has started normal operation.

  When the heating of the fuel is started before the start in this way, the fuel temperature in the common rail 117 rises with the passage of time, and the fuel pressure in the common rail 117 rises as the fuel in the common rail 117 is in a sealed state. Therefore, it can be understood that since the penetration of the fuel injected from the fuel injection valve 109 increases under the fuel pressure after the time point t0, it is necessary to correct this.

  Next, the relationship between the penetration of the injected fuel with respect to the fuel pressure and the fuel temperature and the particle size of the injected fuel will be described with reference to FIGS.

  FIG. 5 shows the relationship between the fuel pressure and the fuel temperature penetration. The penetration of the injected fuel tends to become longer as the fuel pressure is increased, and the penetration distance tends to become slower as the fuel pressure is further increased.

  Conversely, when the fuel temperature is increased, the penetration of the injected fuel tends to be short, and as the fuel temperature is further increased, the penetration distance tends to be slow. As can be seen, the fuel pressure has a higher influence on the penetration of the injected fuel. Therefore, it can be understood that the handling of the penetration related to the fuel pressure is important.

  FIG. 6 shows the relationship between the fuel pressure and the fuel temperature and the injected fuel particle size. When the fuel pressure is increased, the particle size of the injected fuel tends to become finer, but the tendency becomes slower as the fuel pressure is further increased.

  Also, when the fuel temperature is increased, the particle size of the injected fuel tends to become smaller as with the fuel pressure, and the tendency decreases as the fuel temperature increases. As can be seen, the influence of the injected fuel on the particle size is high both in fuel pressure and fuel temperature.

  Therefore, it can be understood that heating the common rail 117 reduces the particle size of the fuel to promote vaporization, and it is important to cope with the increase in penetration with respect to the increase in fuel pressure by this heating control.

  As described in FIGS. 4, 5, and 6, when the fuel in the common rail 117 is heated by performing preheating of the fuel, the fuel temperature in the common rail 117 rises and atomization of the injected fuel is promoted. At the same time, since the fuel pressure is also increased, the penetration of the injected fuel at the start of the internal combustion engine becomes longer, and the injected fuel tends to collide with the piston crown. For this reason, it is necessary to cope with the penetration of the injected fuel caused by the increase in fuel pressure due to the preheating of the fuel.

  Next, the influence of unburned gas (HC) and particulate matter (PM / PN) during combustion on the fuel pressure and fuel injection timing when starting the internal combustion engine will be described with reference to FIGS.

  7 and 8 show an example of the injection control system when the fuel pressure is not corrected by the preheating of the fuel as in the present embodiment, and the reference fuel injection timing is the intake air intake This is an injection control system of a so-called intake process injection system located between the dead center and the intake bottom dead center.

  FIG. 7 shows the discharge behavior of unburned gas and particulate matter with respect to the fuel pressure at the start of the internal combustion engine at the same fuel injection timing.

  As explained in FIG. 6, the higher the fuel pressure, the finer the particle size of the injected fuel, so that the fuel tends to vaporize, and the discharge of unburned gas and particulate matter at the start of the internal combustion engine tends to decrease. is there. Therefore, it can be seen that a higher fuel pressure has a greater effect of reducing unburned gas (HC) and particulate matter (PM / PN).

  Therefore, when the fuel pressure is increased by the preheating of the fuel and the particle size of the fuel is reduced, an effect and an effect of improving the vaporization efficiency due to the high fuel temperature are obtained.

  However, if the fuel pressure is increased by the preheating of the fuel, the penetration of the injected fuel becomes longer as the fuel pressure becomes higher as explained in FIG. 5, so that the injected fuel easily collides with the piston crown surface. The effect of reducing unburned gas and particulate matter cannot be obtained sufficiently. For this purpose, it is necessary to prevent the fuel pressure from being affected even if the fuel pressure is increased by the preheating of the fuel and the penetration of the injected fuel becomes longer.

  FIG. 8 shows the discharge behavior of unburned gas and particulate matter with respect to the fuel injection timing at the start of the internal combustion engine at the same high fuel pressure. In order to reduce the amount of fuel colliding with the piston crown due to increased penetration of injected fuel at high fuel pressure, measures are taken by changing the fuel injection timing at the start of the internal combustion engine to the lag side (intake bottom dead center direction) I understand that I can do it.

  That is, when the distance between the fuel injection valve 109 and the piston crown surface is increased corresponding to the increase in the penetration of the injected fuel, the fuel is injected to reduce the degree of collision of the fuel with the piston crown surface. ing. For this reason, the discharge amount of unburned gas and particulate matter is reduced, and the effect of fuel atomization can be sufficiently exhibited.

  In this embodiment, the fuel injection timing at the start of the internal combustion engine is shifted to the delay side (toward the intake bottom dead center direction) as the fuel pressure increases. The control method is based on FIGS. 9 to 11. I will explain.

  FIG. 9 shows a case where the fuel pressure is low. The ignition switch is turned on and the internal combustion engine control unit 101 calculates the fuel injection timing by taking in the fuel pressure as shown in FIG. 9 (e). Actually, fuel injection is not executed.

  Next, when the preheating of the fuel is started as shown in FIG. 9C, the fuel pressure in the common rail 117 gradually increases as shown in FIG. 9D in order to heat the fuel.

  In this process, the start is started by the starter switch as shown in FIG. 9B. At this start point, the fuel pressure exceeds the determined fuel pressure, but the heating time is short, so the increase in the fuel pressure is small. As shown in FIG. 9E, the correction amount to the delay side of the fuel injection timing is small.

  Then, as shown in FIG. 9D, fuel is consumed by fuel injection, so the fuel pressure in the common rail 117 gradually decreases.

  Along with this, as shown in FIG. 9 (e), the fuel injection timing is advanced as the fuel pressure decreases, and the fuel pressure in the common rail 117 is controlled to the normal fuel pressure until the complete explosion occurs.

  If the reference fuel injection timing is between the intake top dead center and the intake bottom dead center and the fuel pressure at the time of starting the internal combustion engine is lower than the judgment fuel pressure in the process leading to the complete explosion, the reference fuel injection timing is set to the intake top dead center. It is also possible to correct to the leading side in the point direction. Note that when the complete explosion is determined, the fuel injection timing is naturally controlled to the normal fuel injection timing.

  And by these controls, the rotation speed of the internal combustion engine changes as shown in FIG.

  Next, FIG. 10 shows a case where the fuel pressure is high. When the ignition switch is turned on, the internal combustion engine control unit 101 calculates the fuel injection timing by taking in the fuel pressure as shown in FIG. However, the fuel injection is not actually executed.

  Next, when the preheating of the fuel is started early as shown in FIG. 9C, the fuel pressure in the common rail 117 gradually increases as shown in FIG. 10D in order to heat the fuel. .

  In this process, the start is started by the starter switch as shown in FIG. 10B. At this start point, the heating time by the heater is long, so the increase in the fuel pressure becomes large.

  For this reason, as shown in FIG.10 (e), the correction amount to the delay side of a fuel injection timing increases. The fuel preheating control is continued until the starter switch is disconnected. In this way, if the heating time of the fuel is increased, the fuel temperature can be increased, so that the particle size of the injected fuel can be reduced, and the effect of contributing to the phenomenon of harmful exhaust components can be achieved.

  Then, as shown in FIG. 10 (d), the fuel pressure in the common rail 117 gradually decreases due to the fuel injection at the start.

  Along with this, as shown in FIG. 10 (e), the fuel injection timing is advanced as the fuel pressure decreases, and the fuel pressure in the common rail 117 is controlled to the normal fuel pressure until the complete explosion occurs.

  As in the case of FIG. 9, in the process of reaching the complete explosion, when the reference fuel injection timing is between the intake top dead center and the intake bottom dead center, and the fuel pressure at the start of the internal combustion engine is lower than the determination fuel pressure, It is also possible to correct the reference fuel injection timing to the advancing side in the intake top dead center direction. Note that when the complete explosion is determined, the fuel injection timing is naturally controlled to the normal fuel injection timing.

  Here, the judgment fuel pressure shown in FIG. 9 and FIG. 10 represents the fuel pressure that becomes a reference when it is judged that the ratio of penetration to the piston crown surface is small at the reference fuel injection timing. Can be determined appropriately according to the specifications of the fuel injection system.

  Next, FIG. 11 shows control when the fuel pressure becomes too high and the fuel injection timing becomes too late.

  Basically, the control is the same as that shown in FIG. 10, but if the fuel pressure becomes too high as shown in FIG. 11 (d), the fuel injection timing is greatly delayed. For this reason, there is a possibility that the charge injection timing may pass through the intake bottom dead center of the piston and reach the compression process.

  When the piston passes the intake bottom dead center and shifts to the compression process, the distance between the fuel injection valve and the piston crown surface becomes close, and the injected fuel easily collides with the piston.

  In order to solve such a problem, a delay limit value is set for the fuel injection timing, and if the fuel injection timing exceeds the delay limit value by the correction calculation, the corrected fuel injection timing is set to the delay limit value. The fuel injection is started at the replaced delay side limit value.

  Further, as described above, when the reference fuel injection timing is between the intake top dead center and the intake bottom dead center and the fuel pressure at the time of starting the internal combustion engine is lower than the determination fuel pressure, the reference fuel injection timing is set to the intake top dead center. Although it is possible to correct the direction to the advancing side, if the advancing is excessive, the distance between the fuel injection valve and the piston crown surface becomes close, and the injected fuel easily collides with the piston.

  Therefore, if the advance side limit value is set to the fuel injection timing and the fuel injection timing exceeds the advance side limit value by the correction calculation, the corrected fuel injection timing is replaced with the advance side limit value. The fuel injection may be started with the advanced side limit value.

  As described above, when the fuel is preheated before the internal combustion engine is started, the fuel pressure in the common rail is measured or estimated, and when the internal combustion engine is started, the fuel is injected from the fuel injection valve according to the fuel pressure. The fuel is injected at the fuel injection timing that does not collide with the piston crown.

  As a result, the fuel injection timing is changed according to the fuel pressure at the start of the internal combustion engine, so that it is possible to reduce the collision of the fuel with the piston crown due to the increase in the penetration of the injected fuel accompanying the increase in the fuel pressure. The increase in unburned gas and particulate matter can be suppressed.

  Although the above explanation has been given for the start of the intake process injection method, the same can be said for the start of the compression process injection method, but in the compression process, the piston rises from the compression bottom dead center toward the compression top dead center. Therefore, it is necessary to perform control opposite to the above description.

  Although the detailed explanation is omitted, the main point is that the higher the fuel pressure in the intake stroke injection, the more the fuel injection timing is moved to the intake bottom dead center side of the piston. The fuel injection timing is moved to the point side, and basically the same control as in the intake process injection method may be executed.

  The compression process injection method is a method that has been studied for use in an idle stop system and the like, and is a method in which fuel is injected into a cylinder that is shifted to the compression process. In this case, since the internal combustion engine is stopped, the common rail is heated by the heat generated by the internal combustion engine. For this reason, the fuel temperature at the start after the idle stop is high, and an increase in the penetration of the injected fuel is caused by the increase in the fuel pressure accompanying the temperature increase.

  Therefore, when the reference fuel injection timing is between the compression bottom dead center and the compression top dead center, it is necessary to correct the reference fuel injection timing with the fuel pressure that varies depending on the fuel temperature at the time of starting. Specifically, as the fuel pressure increases, the fuel injection timing is moved to the leading side of the compression bottom dead center side to reduce the collision of the fuel with the piston crown due to the increase in the penetration of the injected fuel accompanying the increase in the fuel pressure. Is.

  That is, during idle stop, the fuel pressure in the common rail increases due to heating by the internal combustion engine. If the idling stop is canceled in this process and the start is started, the fuel pressure is greatly increased at the start time, so that the penetration increases. Therefore, the fuel injection timing for the cylinders in the compression process is moved to the compression side dead center side in accordance with the increase in penetration.

  As described above, when the fuel is heated by the heat of the internal combustion engine during the idling stop, the fuel pressure in the common rail is measured or estimated, and when the internal combustion engine is started, the fuel injection valve according to the fuel pressure. The fuel is injected at a fuel injection timing that does not collide with the piston crown at least.

  As a result, the fuel injection timing is changed according to the fuel pressure at the start of the internal combustion engine, so that it is possible to reduce the collision of the fuel with the piston crown due to the increase in the penetration of the injected fuel accompanying the increase in the fuel pressure. The increase in unburned gas and particulate matter can be suppressed.

  DESCRIPTION OF SYMBOLS 1 ... In-cylinder injection type internal combustion engine, 101 ... Internal combustion engine control unit, 102 ... Air cleaner, 103 ... Air flow sensor, 104 ... Electric throttle valve, 105 ... Intake pipe, 106 ... Combustion chamber, 107 ... Sultle sensor, 108 DESCRIPTION OF SYMBOLS ... High pressure fuel pump, 109 ... Fuel injection valve, 110 ... Ignition coil, 111 ... Spark plug, 112 ... Fuel heater, 113 ... Fuel temperature sensor, 114 ... Fuel pressure sensor, 115 ... Crankshaft, 116 ... Crank angle sensor, 117 ... Fuel common rail, 118 ... Exhaust pipe, 119 ... Intake valve, 120 ... Cam shaft, 121 ... Cam angle sensor, 202 ... Water temperature sensor, 203 ... Air-fuel ratio sensor.

Claims (15)

A fuel preheating means for driving a fuel heating means for heating fuel sent to a fuel injection valve to be injected into the combustion chamber before starting the internal combustion engine;
Fuel pressure measuring means for measuring or estimating fuel pressure during preheating of the fuel;
Fuel injection timing setting means for setting a reference fuel injection timing when starting the internal combustion engine;
A fuel injection control device for an internal combustion engine, comprising: fuel injection timing correction means for correcting the reference fuel injection timing corresponding to the fuel pressure during preheating of fuel. The fuel injection control device for an internal combustion engine according to claim 1,
When the fuel pressure at the start of the internal combustion engine is higher than a predetermined determination fuel pressure, the fuel injection timing correction means adjusts the fuel injection timing from the reference fuel injection timing to the delay side in the piston bottom dead center direction. A fuel injection control device for an internal combustion engine characterized by correcting. The fuel injection control device for an internal combustion engine according to claim 1,
When the fuel pressure at the start of the internal combustion engine is higher than a predetermined determination fuel pressure, the fuel injection timing correction means delays the piston in the direction of the bottom dead center of the piston from the reference fuel injection timing according to the degree. A fuel injection control device for an internal combustion engine, wherein the fuel injection timing is corrected to the side. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3,
The fuel injection timing correction means corrects the fuel injection timing from the reference fuel injection timing toward the piston bottom dead center when the fuel pressure at the start of the internal combustion engine is higher than a predetermined determination fuel pressure. The fuel injection control device for an internal combustion engine, wherein when the corrected fuel injection timing exceeds a predetermined delay side limit value, the corrected fuel injection timing is replaced with the delay side limit value. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3,
The fuel injection timing correction means returns the corrected fuel injection timing to the reference fuel injection timing side in response to the fuel pressure when the fuel pressure has decreased during startup of the internal combustion engine. A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1,
When the fuel pressure at the start of the internal combustion engine is lower than a predetermined determination fuel pressure, the fuel injection timing correction means adjusts the fuel injection timing from the reference fuel injection timing to the advance side in the intake top dead center direction of the piston. A fuel injection control device for an internal combustion engine characterized by correcting. The fuel injection control device for an internal combustion engine according to claim 1,
When the fuel pressure at the start of the internal combustion engine is lower than a predetermined determination fuel pressure, the fuel injection timing correction means advances from the reference fuel injection timing in the direction of the intake top dead center of the piston according to the degree. A fuel injection control device for an internal combustion engine, wherein the fuel injection timing is corrected to the side. The fuel injection control device for an internal combustion engine according to claim 6 or 7,
The fuel injection timing correction means corrects the fuel injection timing from the reference fuel injection timing toward the intake top dead center of the piston when the fuel pressure at the start of the internal combustion engine is lower than a predetermined determination fuel pressure. A fuel injection control device for an internal combustion engine, wherein when the corrected fuel injection timing exceeds a predetermined advance side limit value, the corrected fuel injection timing is replaced with an advance side limit value. The fuel injection control device for an internal combustion engine according to claim 1,
When the reference fuel injection timing at the start of the internal combustion engine is between the compression bottom dead center and the compression top dead center, the fuel injection timing correction means determines that the fuel pressure at the start of the internal combustion engine is predetermined. A fuel injection control device for an internal combustion engine, wherein when the fuel pressure is higher than the fuel pressure, the fuel injection timing is corrected from the reference fuel injection timing toward the advance side in the compression bottom dead center direction of the piston. The fuel injection control device for an internal combustion engine according to claim 9,
When the fuel pressure at the start of the internal combustion engine is higher than a predetermined determination fuel pressure, the fuel injection timing correction means advances the compression bottom dead center direction of the piston from the reference fuel injection timing according to the degree. A fuel injection control device for an internal combustion engine, wherein the fuel injection timing is corrected to the side. The fuel injection control device for an internal combustion engine according to claim 9,
The fuel injection timing correction means corrects the fuel injection timing from the reference fuel injection timing toward the compression bottom dead center when the fuel pressure at the start of the internal combustion engine is higher than a predetermined determination fuel pressure. The fuel injection control device for an internal combustion engine, wherein when the corrected fuel injection timing exceeds a predetermined advance side limit value, the corrected fuel injection timing is replaced with the advance side limit value. The fuel injection control device for an internal combustion engine according to claim 9,
The fuel injection timing correction means returns the corrected fuel injection timing to the reference fuel injection timing side in response to the fuel pressure when the fuel pressure has decreased during startup of the internal combustion engine. A fuel injection control device for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 9,
The fuel injection timing correction means adjusts the fuel injection timing from the reference fuel injection timing to the delay side in the compression top dead center direction when the fuel pressure at the start of the internal combustion engine is lower than a predetermined determination fuel pressure. A fuel injection control device for an internal combustion engine characterized by correcting. The fuel injection control device for an internal combustion engine according to claim 9,
When the fuel pressure at the start of the internal combustion engine is lower than a predetermined determination fuel pressure, the fuel injection timing correction means advances the compression top dead center direction of the piston from the reference fuel injection timing according to the degree. A fuel injection control device for an internal combustion engine, wherein the fuel injection timing is corrected to the side. The fuel injection control device for an internal combustion engine according to claim 13 or 14,
The fuel injection timing correction means corrects the fuel injection timing from the reference fuel injection timing toward the compression top dead center of the piston when the fuel pressure at the start of the internal combustion engine is lower than a predetermined determination fuel pressure. The fuel injection control device for an internal combustion engine, wherein when the corrected fuel injection timing exceeds a predetermined delay side limit value, the corrected fuel injection timing is replaced with the delay side limit value.

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