JP2010133367A - Fuel injection control device of cylinder fuel injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly set the fuel injection timing for restraining pre-ignition in a cylinder fuel injection engine. <P>SOLUTION: When a predetermined pre-ignition occurrence condition is established, the operating condition is determined to easily cause pre-ignition. A self ignition delay time which is the time elapsed from the start of fuel injection until self ignition occurs is estimated before fuel injection based on the intake temperature and engine load (e.g. intake air quantity and intake pipe pressure), and a self ignition lag angle, which is a crank angle from the start of fuel injection to the occurrence of self ignition is estimated based on the self ignition delay time and the engine rotating speed. Thus, the fuel injection start timing is set so that the self ignition occurrence timing coincides with the ignition timing based on the self ignition lag angle estimated before fuel injection, thereby restraining pre-ignition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for a direct injection internal combustion engine that directly injects fuel into a combustion chamber of the internal combustion engine.

  2. Description of the Related Art In recent years, some internal combustion engines that are installed in vehicles employ a cylinder injection type internal combustion engine that has the features of low fuel consumption, low emission, and high output. This in-cylinder internal combustion engine tends to increase the compression ratio in order to meet the demand for further reduction in fuel consumption. For this reason, “pre-ignition”, which is a phenomenon in which the air-fuel mixture self-ignites before ignition timing due to the high temperature in the combustion chamber due to compression of the compression stroke, is likely to occur. When pre-ignition occurs, Or vibration may occur, and in the worst case, the internal combustion engine may be damaged.

  Therefore, as described in Patent Document 1 (Japanese Patent No. 3912032), when the occurrence of pre-ignition is detected or predicted, the fuel injection timing is retarded from the reference fuel injection timing according to the engine operating conditions. In some cases, preignition is suppressed by setting the ignition timing closer to the advance side than the reference ignition timing corresponding to the engine operating conditions.

Further, as described in Patent Document 2 (Japanese Patent Laid-Open No. 2005-69049), when the internal combustion engine is restarted at a high temperature, fuel is injected into a cylinder or all cylinders that may cause self-ignition. The pre-ignition at the time of high-temperature restart of the internal combustion engine is suppressed by starting the process of starting the internal combustion engine after changing the air-fuel ratio of the cylinder air-fuel mixture to a rich air-fuel ratio in which self-ignition is unlikely to occur. There is what I did.
Japanese Patent No. 3912032 (first page, etc.) JP-A-2005-69049 (second page, etc.)

  By the way, the pre-ignition is a phenomenon in which the air-fuel mixture self-ignites before the ignition timing. Therefore, the pre-ignition can be prevented if the self-ignition occurs before the ignition timing. .

  However, the technique disclosed in Patent Document 1 simply determines the fuel injection timing as the reference fuel injection timing when the occurrence of pre-ignition is detected or predicted without considering the relationship between the timing at which self-ignition occurs and the ignition timing. Since the ignition timing is only set to the advance side with respect to the reference ignition timing by setting the retard side more than the retard angle side, there is a possibility that the retard correction amount of the fuel injection timing will be excessive or insufficient. For example, if the retard correction amount of the fuel injection timing is too small, there is a possibility that the pre-ignition cannot be sufficiently suppressed because the timing at which self-ignition occurs before the ignition timing. On the other hand, if the retardation correction amount of the fuel injection timing is too large, the fuel injection timing may be far from the appropriate fuel injection timing according to the engine operating conditions, and the combustion state may deteriorate.

  Further, since the technique of Patent Document 2 is configured to supply fuel as means for suppressing pre-ignition at the time of high-temperature restart of the internal combustion engine, the pre-ignition during normal start of the internal combustion engine or during operation is completely suppressed. There is also the disadvantage that it cannot be done.

  The present invention has been made in consideration of these circumstances. Therefore, the object of the present invention is to appropriately set the fuel injection timing for suppressing pre-ignition, and to suppress the effect of suppressing pre-ignition. An object of the present invention is to provide a fuel injection control device for a direct injection internal combustion engine that can suppress deterioration of the combustion state while increasing the fuel consumption.

  In order to achieve the above object, an invention according to claim 1 is directed to a fuel injection control device for a direct injection internal combustion engine in which fuel is directly injected into a combustion chamber of the internal combustion engine. It is equipped with a pre-ignition suppression control means for executing pre-ignition suppression control for suppressing pre-ignition by setting the fuel injection start timing so that the self-ignition occurrence timing at which the auto-ignition occurs coincides with the ignition timing. is there.

  In the pre-ignition suppression control, since the fuel injection start timing is set so that the self-ignition occurrence timing coincides with the ignition timing, it is possible to reliably prevent the self-ignition occurrence timing from being earlier than the ignition timing. Ignition can be reliably suppressed. In addition, by setting the fuel injection start timing so that the self-ignition occurrence timing matches the ignition timing, it is possible to prevent the fuel injection start timing from being delayed more than necessary, so that the fuel injection timing depends on the operating conditions. Therefore, it is possible to avoid a significant departure from the appropriate fuel injection timing, and to suppress deterioration of the combustion state. Thereby, the fuel injection timing for suppressing pre-ignition can be set appropriately, and deterioration of the combustion state can be suppressed while enhancing the pre-ignition suppression effect.

  In this case, as in claim 2, the self-ignition delay period from the start of fuel injection to the occurrence of self-ignition during the compression stroke injection mode is determined by the self-ignition delay period determining means, and based on the determined self-ignition delay period Thus, it is preferable to execute the pre-ignition suppression control by setting the fuel injection start timing so that the self-ignition occurrence timing coincides with the ignition timing. Since the time at which the self-ignition delay period elapses from the fuel injection start timing is the auto-ignition occurrence timing, in order to make this self-ignition occurrence timing coincide with the ignition timing, the fuel injection is performed at the time when the auto-ignition delay period is reached from the ignition timing. What is necessary is just to set to a start time. Therefore, if the self-ignition delay period is used, the fuel injection start timing can be set so that the self-ignition occurrence timing coincides with the ignition timing.

  Specifically, as in claim 3, the self-ignition delay time, which is the time from the start of fuel injection to the occurrence of self-ignition based on the intake air temperature and load of the internal combustion engine, is predicted, and the self-ignition delay time The self-ignition delay angle, which is the crank angle from the start of fuel injection to the occurrence of self-ignition, is predicted as the self-ignition delay period based on the rotation speed of the internal combustion engine and the self-ignition occurrence timing based on the predicted self-ignition delay angle The pre-ignition suppression control may be executed by setting the fuel injection start timing so as to coincide with the ignition timing.

  Since the temperature in the combustion chamber in the compression stroke changes due to the intake air temperature and load of the internal combustion engine (for example, intake air amount and intake pipe pressure), the self-ignition delay time changes. The ignition delay time can be predicted with high accuracy, and the auto ignition delay angle can be accurately predicted by converting the predicted auto ignition delay time into the self ignition delay angle based on the rotation speed of the internal combustion engine. . In this way, the self-ignition delay angle can be accurately predicted before fuel injection, and the fuel injection start timing is set so that the self-ignition occurrence timing matches the ignition timing based on the predicted self-ignition delay angle. It can be set with high accuracy.

  Alternatively, a cylinder pressure sensor for detecting an in-cylinder pressure of the internal combustion engine is provided as in claim 4, and the self-ignition occurrence timing is detected based on the output of the in-cylinder pressure sensor. The self-ignition delay angle, which is the crank angle from the start of fuel injection to the occurrence of self-ignition based on the fuel injection start timing, is calculated as the self-ignition delay period, and the self-ignition occurrence timing is calculated based on the calculated self-ignition delay angle The pre-ignition suppression control may be executed by setting the fuel injection start timing so as to coincide with the ignition timing.

  When self-ignition occurs, the in-cylinder pressure rapidly rises. Therefore, if the behavior of the output of the in-cylinder pressure sensor is monitored, the self-ignition occurrence timing can be detected with high accuracy, and the detected self-ignition occurrence timing and fuel injection are detected. The self-ignition delay angle can be accurately calculated from the start time. In this way, the self-ignition delay angle can be accurately calculated based on the actual self-ignition occurrence timing detected after the fuel injection, and the self-ignition occurs based on the self-ignition delay angle calculated after the previous fuel injection. The current fuel injection start timing can be accurately set so that the timing matches the ignition timing.

  Further, as in claim 5, the self-ignition delay period learning means learns the self-ignition delay period for each driving condition, and the self-ignition delay corresponding to the current driving condition from the learned data of the self-ignition delay period. By selecting the learning value for the period and setting the fuel injection start timing so that the self-ignition occurrence timing coincides with the ignition timing based on the learning value for the self-ignition delay period, the plug suppression control is executed. Also good. In this way, it is possible to accurately set the fuel injection start timing so that the self-ignition occurrence timing coincides with the ignition timing based on the learned value of the self-ignition delay period corresponding to the current operating conditions.

  By the way, in the compression stroke injection mode, when the internal combustion engine is started, during low rotation and high load operation (for example, during acceleration), when the intake air temperature of the internal combustion engine is high, or when the fuel supplied to the internal combustion engine is a fuel with a low octane number (for example, In the case of (regular gasoline), the driving conditions are likely to cause pre-ignition.

  Therefore, as described in claim 6, pre-ignition suppression control may be executed when the internal combustion engine is started. In this way, it is possible to reliably suppress pre-ignition that occurs when the internal combustion engine is started (for example, during normal startup or during high-temperature startup).

  Further, as in the seventh aspect, the pre-ignition suppression control may be executed during the low rotation and high load operation of the internal combustion engine. In this way, pre-ignition that occurs during low rotation and high load operation (for example, acceleration) of the internal combustion engine can be reliably suppressed.

  Further, as in the eighth aspect, the pre-ignition suppression control may be executed when the intake air temperature of the internal combustion engine is equal to or higher than a predetermined value. In this way, pre-ignition that occurs when the intake air temperature of the internal combustion engine is high can be reliably suppressed.

  Further, as described in claim 9, when the fuel supplied to the internal combustion engine is a fuel having a low octane number, the pre-ignition suppression control may be executed. In this way, it is possible to reliably suppress pre-ignition that occurs when the fuel supplied to the internal combustion engine is a fuel having a low octane number (for example, regular gasoline).

  Further, the present invention is applied to a center injection type in-cylinder injection internal combustion engine in which a fuel injection valve is arranged so as to inject fuel into the combustion chamber from substantially above the center of the combustion chamber of the internal combustion engine. Good. The center injection type in-cylinder injection internal combustion engine has the advantage that the area operated in the compression stroke injection mode can be expanded to reduce fuel consumption. However, if the area operated in the compression stroke injection mode is expanded, the pre-ignition is correspondingly increased. Since the operation range that is likely to occur is also expanded, if the preignition suppression control is executed during the compression stroke injection mode by applying the present invention, the region that is operated in the compression stroke injection mode is expanded to reduce fuel consumption. Pre-ignition can be reliably suppressed while satisfying the requirements.

  Several embodiments embodying the best mode for carrying out the present invention will be described below.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is a center injection type cylinder injection internal combustion engine. A throttle valve 15 whose opening degree is adjusted by a motor 14 is provided downstream of the air cleaner 13. Is provided. Further, a surge tank 16 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 17 for detecting the intake pipe pressure is provided in the surge tank 16. The surge tank 16 is provided with an intake manifold 18 that introduces air into each cylinder of the engine 11.

  A fuel injection valve 19 that directly injects fuel into the cylinder is attached to the cylinder head 31 of the engine 11 for each cylinder. The fuel discharged from the high-pressure fuel pump 21 is sent to the delivery pipe 23 through the high-pressure fuel pipe 22, and the high-pressure fuel is distributed from the delivery pipe 23 to the fuel injection valve 19 of each cylinder. A fuel pressure sensor 24 that detects the pressure (fuel pressure) of the fuel supplied to the fuel injection valve 19 is attached to the delivery pipe 23.

  As shown in FIG. 2, a spark plug 20 is attached to each cylinder of the cylinder head 31 of the engine 11, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 20. The engine 11 is a center injection type in-cylinder injection engine, in which fuel is injected downward into the combustion chamber 32 from a fuel injection valve 19 disposed substantially above the center of the combustion chamber 32 (near the spark plug 20). The fuel adhering to the piston upper surface 33 and the cylinder inner wall surface 34 is set by making the fuel injection force (penetration force) weak so that the fuel injected from the fuel injection valve 19 does not collide with the piston upper surface 33 and the cylinder inner wall surface 34. Is trying to reduce.

  On the other hand, as shown in FIG. 1, the exhaust pipe 25 of the engine 11 is provided with an exhaust gas sensor 26 (an air-fuel ratio sensor, an oxygen sensor, or the like) that detects an air-fuel ratio or rich / lean of the exhaust gas.

  A cooling water temperature sensor 27 that detects the cooling water temperature and a crank angle sensor 28 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 28, the crank angle and the engine speed are detected. The intake air temperature of the engine 11 is detected by the intake air temperature sensor 29.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 19 and The ignition timing of the spark plug 20 is controlled.

  At that time, the ECU 30 changes the injection mode (combustion mode) between the compression stroke injection mode (stratified combustion mode) and the intake stroke injection mode (homogeneous combustion mode) according to the engine operating state (engine speed, required torque, etc.). Switch with. In the compression stroke injection mode (stratified combustion mode), a small amount of fuel is directly injected into the cylinder in the compression stroke, and a stratified mixture is formed in the vicinity of the spark plug 20 for stratified combustion, thereby improving fuel efficiency. On the other hand, in the intake stroke injection mode (homogeneous combustion mode), the engine output is increased by increasing the fuel injection amount and directly injecting the fuel into the cylinder in the intake stroke to form a homogeneous mixture and performing homogeneous combustion.

  Incidentally, during the intake stroke injection mode, “pre-ignition”, which is a phenomenon in which the air-fuel mixture self-ignites before the ignition timing, is likely to occur. Further, when the engine 11 is started or during low-speed and high-load operation. When the intake air temperature of the engine 11 is high (for example, during acceleration) or when the fuel supplied to the engine 11 is a fuel having a low octane number (for example, regular gasoline), the driving conditions are likely to cause pre-ignition.

  Therefore, the ECU 30 executes a fuel injection control routine of FIG. 4 to be described later during the intake stroke injection mode, so that it is determined that the operating condition is likely to cause pre-ignition when a predetermined pre-ignition generation condition is satisfied. Thus, the self-ignition delay time, which is the time from the start of fuel injection to the occurrence of self-ignition, is predicted based on the intake air temperature and the engine load (for example, intake air amount and intake pipe pressure) before fuel injection. Based on the delay time and the engine speed, a self-ignition delay angle (self-ignition delay period) that is a crank angle from the start of fuel injection to the occurrence of self-ignition is predicted. Preignition is suppressed by setting the fuel injection start timing so that the self-ignition occurrence timing coincides with the ignition timing based on the self-ignition delay angle predicted before fuel injection in this way, that is, switching to the compression stroke injection mode. The pre-ignition suppression control is executed.

  Because the temperature in the combustion chamber in the compression stroke changes due to the intake air temperature and engine load (for example, intake air amount and intake pipe pressure), the self-ignition delay time changes. Therefore, if the intake air temperature and load are used, the auto-ignition delay time is accurate. The self-ignition delay angle can be accurately predicted by converting the predicted self-ignition delay time into the self-ignition delay angle based on the engine rotation speed.

As shown in FIG. 3, the time at which the self-ignition delay angle elapses from the fuel injection start timing is the self-ignition occurrence timing. Therefore, in order to make this self-ignition occurrence timing coincide with the ignition timing, It is only necessary to set the fuel injection start time at the point when the fuel is only burned. Therefore, if the self-ignition delay angle is used, the fuel injection start timing can be set so that the self-ignition occurrence timing coincides with the ignition timing.
Hereinafter, the processing content of the fuel injection control routine of FIG. 4 executed by the ECU 30 will be described.

[Fuel injection control routine]
The fuel injection control routine shown in FIG. 4 is executed at a predetermined cycle regardless of the injection mode. When this routine is started, first, at step 101, it is determined whether or not the pre-ignition generation condition is satisfied, for example, by whether or not one of the following operating conditions (1) to (4) is satisfied. To do.

(1) At the time of starting the engine 11
(2) The engine 11 is operating at low speed and high load (for example, during acceleration).
(3) The intake air temperature of the engine 11 is not less than a predetermined value.
(4) The fuel supplied to the engine 11 is a low octane fuel (for example, regular gasoline).

  Here, the determination method of the fuel having a low octane number is, for example, that the vibration intensity detected by a knock sensor (not shown) in a predetermined operation region (for example, a low rotation and high load operation region where knocking or pre-ignition is likely to occur). It is determined whether or not the fuel has a low octane number depending on whether or not the fuel has a predetermined strength or more. Alternatively, it may be determined whether or not the fuel has a low octane number by determining whether or not the fuel is likely to cause knocking based on the learning value of the knock control.

  The above operating conditions (1) to (4) are all operating conditions where pre-ignition is likely to occur. Therefore, if the operating conditions are any of (1) to (4) above, the pre-ignition generating condition is satisfied. However, if none of the operating conditions (1) to (4) is satisfied, the pre-ignition generation condition is not satisfied.

  If it is determined in step 101 that the pre-ignition generation condition is not satisfied, the process proceeds to step 102, where fuel injection is started based on the current operating conditions (for example, engine speed, engine load, cooling water temperature, intake air temperature, etc.). The time is calculated by a map or a mathematical formula.

  On the other hand, if it is determined in step 101 that the pre-ignition generation condition is satisfied, it is determined that the operation condition is likely to cause pre-ignition, and the process proceeds to step 103, where the current intake air temperature and the engine load are determined. The self-ignition delay time is predicted by calculating the self-ignition delay time (the time from the start of fuel injection until the occurrence of self-ignition) based on (for example, the intake air amount or the intake pipe pressure) using a map or a mathematical expression. Here, the map or formula of the self-ignition delay time is created in advance based on design data, test data, simulation data, and the like, and is stored in the ROM of the ECU 30.

  Thereafter, the routine proceeds to step 104, where the self-ignition delay time is converted into a self-ignition delay angle (crank angle from the start of fuel injection to the occurrence of self-ignition) based on the current engine speed, thereby reducing the self-ignition delay angle. Predict. The processing of these steps 103 and 104 serves as a self-ignition delay period determining means in the claims.

  Thereafter, the process proceeds to step 105, and the ignition timing set in an ignition control routine (not shown) is read. This ignition timing is calculated based on the current operating conditions (for example, whether or not warm-up control is being performed at the start or after startup, engine speed, engine load, cooling water temperature, intake air temperature, etc.).

  After that, the routine proceeds to step 106, where the crank angle obtained by setting the crank angle obtained by the self-ignition delay angle from the ignition timing is set as the fuel injection start timing so that the self-ignition occurrence timing coincides with the ignition timing, thereby suppressing the pre-ignition. Perform suppression control. The processing in step 106 serves as a pre-gage suppression control means in the claims.

  After setting the fuel injection start time in this way, the routine proceeds to step 107, where the fuel injection valve 19 is injected when the crank angle detected by the crank angle sensor 28 reaches the fuel injection start time.

  In the first embodiment described above, the pre-ignition suppression control is executed by setting the fuel injection start timing so that the self-ignition occurrence timing coincides with the ignition timing. It is possible to reliably prevent the occurrence of the front and to suppress pre-ignition with certainty. Moreover, by setting the fuel injection start timing so that the self-ignition occurrence timing matches the ignition timing, it is possible to prevent the fuel injection start timing from being delayed more than necessary, so that the fuel injection timing depends on the operating conditions. Therefore, it is possible to avoid a significant departure from the appropriate fuel injection timing, and to suppress deterioration of the combustion state. Thereby, the fuel injection timing for suppressing the pre-ignition can be set appropriately, and the deterioration of the combustion state can be suppressed while enhancing the effect of suppressing the pre-ignition.

  The center injection type in-cylinder injection engine 11 has an advantage that the area operated in the compression stroke injection mode can be expanded to reduce fuel consumption. However, if the area operated in the compression stroke injection mode is expanded, the pre-ignition is correspondingly increased. Since the operation region that is likely to occur is also expanded, if the pre-ignition suppression control is executed even during the compression stroke injection mode as in the first embodiment, the region that is operated in the compression stroke injection mode is expanded and reduced. Pre-ignition can be reliably suppressed while satisfying the demand for higher fuel consumption.

  In the first embodiment, the self-ignition delay time is predicted based on the intake air temperature and the engine load, and the self-ignition delay angle is predicted based on the self-ignition delay time and the engine rotation speed. The auto-ignition delay angle can be accurately predicted before injection, and the fuel injection start timing can be accurately set so that the auto-ignition occurrence timing coincides with the ignition timing based on the predicted auto-ignition delay angle. .

  Further, in the first embodiment, in the compression stroke injection mode, the fuel supplied to the engine 11 is supplied when the engine 11 is started or when the engine 11 is in a low rotation and high load operation (for example, during acceleration), when the intake air temperature of the engine 11 is high, or when In consideration of the fact that any low-octane fuel (for example, regular gasoline) is an operating condition in which pre-ignition is likely to occur, pre-ignition suppression control is executed under these operating conditions in which pre-ignition is likely to occur. Since it did in this way, a pre-ignition can be suppressed reliably at the driving condition where pre-ignition tends to occur.

  Needless to say, the operating conditions for executing the pre-ignition suppression control may be changed as appropriate.

  Next, Embodiment 2 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the second embodiment, an in-cylinder pressure sensor 35 (see FIG. 1) for detecting the in-cylinder pressure is provided for each cylinder of the engine 11. It should be noted that an in-cylinder pressure sensor 35 may be provided only in a specific cylinder of the engine 11 to detect the in-cylinder pressure of only the specific cylinder and control other cylinders in the same manner. This in-cylinder pressure sensor 35 may be of a type integrated with the spark plug 20 or of a type attached so that a sensor part separate from the spark plug 20 faces the combustion chamber 32. It may be used.

  Further, the ECU 30 executes a fuel injection control routine shown in FIG. 5 to be described later, thereby detecting the self-ignition occurrence time based on the output of the in-cylinder pressure sensor 35 after fuel injection, and the self-ignition occurrence time and the start of fuel injection. Based on the timing, a self-ignition delay angle (a crank angle from the start of fuel injection to the occurrence of self-ignition) is calculated. The pre-ignition suppression control is executed by setting the current fuel injection start timing so that the self-ignition occurrence timing matches the ignition timing based on the self-ignition delay angle calculated after the previous fuel injection.

  As shown in FIG. 6, when self-ignition occurs, the in-cylinder pressure suddenly increases. Therefore, if the behavior of the output of the in-cylinder pressure sensor 35 is monitored, the actual self-ignition occurrence timing can be detected with high accuracy. The self-ignition delay angle can be accurately calculated from the detected self-ignition occurrence time and fuel injection start time.

  In the fuel injection control routine shown in FIG. 5, first, in step 201, it is determined whether or not the pre-ignition generation condition is satisfied. If it is determined that the pre-ignition generation condition is not satisfied, the process proceeds to step 202 and the current Based on the operating conditions, the fuel injection start timing is calculated by a map or mathematical formula.

  On the other hand, if it is determined in step 201 that the pre-ignition generation condition is satisfied, it is determined that the operation condition is such that pre-ignition is likely to occur, the process proceeds to step 203, and is set by an ignition control routine (not shown). After reading the ignition timing, the routine proceeds to step 204 where the self-ignition delay angle calculated after the previous fuel injection is read.

  Thereafter, the routine proceeds to step 205, where the pre-ignition suppression control is executed by setting, as the fuel injection start timing, a crank angle obtained by adding a self-ignition delay angle from the ignition timing so that the self-ignition occurrence timing coincides with the ignition timing. .

  After setting the fuel injection start time in this way, the routine proceeds to step 206, and when the crank angle detected by the crank angle sensor 28 reaches the fuel injection start time, the fuel injection valve 19 is injected.

Thereafter, the process proceeds to step 207, and the self-ignition occurrence time (time when the in-cylinder pressure suddenly increases) is detected based on the output of the in-cylinder pressure sensor 35. At this time, for example, when the amount of increase in the in-cylinder pressure detected by the in-cylinder pressure sensor 35 exceeds a predetermined value, it is determined that the in-cylinder pressure has suddenly increased, and the auto-ignition occurs at that point Detect as time.
Thereafter, the routine proceeds to step 208, where the self-ignition delay angle (crank angle from the start of fuel injection to the occurrence of self-ignition) is calculated based on the self-ignition occurrence timing and the fuel injection start timing.

  In the second embodiment described above, the self-ignition occurrence timing is detected based on the output of the in-cylinder pressure sensor 35, and the self-ignition delay angle is calculated based on the self-ignition occurrence timing and the fuel injection start timing. Therefore, the self-ignition delay angle can be accurately calculated based on the actual self-ignition occurrence time detected after fuel injection, and the self-ignition occurrence time can be calculated based on the self-ignition delay angle calculated after the previous fuel injection. The current fuel injection start timing can be accurately set so as to coincide with the ignition timing.

  Next, Embodiment 3 of the present invention will be described with reference to FIG. However, description of substantially the same parts as those of the second embodiment will be omitted or simplified, and different parts from the second embodiment will be mainly described.

  In the third embodiment, the ECU 30 executes a fuel injection control routine of FIG. 7 to be described later, thereby learning the self-ignition delay period for each operating condition and creating a map of learning values of the self-ignition delay period. Select the learning value for the self-ignition delay period corresponding to the current operating condition from the learning value map for the ignition delay period, and match the self-ignition occurrence timing with the ignition timing based on the learning value for the self-ignition delay period By setting the fuel injection start time so as to cause the pre-ignition suppression control to be executed.

  The fuel injection control routine of FIG. 7 changes the process of step 204 of the fuel injection control routine of FIG. 5 described in the second embodiment to step 204a and adds the process of step 209 after the process of step 208. The process of each step other than this is the same as FIG.

  In the fuel injection control routine shown in FIG. 7, if it is determined in step 201 that the pre-ignition generation condition is satisfied, it is determined that the pre-ignition is likely to occur, and the process proceeds to step 203. After reading the ignition timing set by an ignition control routine (not shown), the routine proceeds to step 204, where a map of the learned value of the self-ignition delay angle is searched, and the current operating conditions (for example, whether the engine is at the start time, The learning value of the auto-ignition delay angle in the learning region corresponding to whether the fuel is low or not, the coolant temperature, the engine speed, the engine load, the intake air temperature, etc.) is selected and read.

  Here, the map of the learning value of the self-ignition delay angle is based on the operating conditions (for example, whether it is at the start, whether the fuel is a low octane number, the cooling water temperature, the engine speed, the engine load, the intake air temperature, etc. ) And a learning value of the self-ignition delay angle is stored for each learning region. The learning value map of the self-ignition delay angle is stored in a rewritable nonvolatile memory (a rewritable memory that retains stored data even when the ECU 30 is powered off), such as a backup RAM (not shown) of the ECU 30. Yes.

  Thereafter, the routine proceeds to step 205, where the pre-ignition suppression control is executed by setting, as the fuel injection start timing, a crank angle obtained by adding a self-ignition delay angle from the ignition timing so that the self-ignition occurrence timing coincides with the ignition timing. .

  After the fuel injection start timing is set in this manner, the fuel injection valve 19 is injected when the crank angle detected by the crank angle sensor 28 reaches the fuel injection start timing (step 206). Thereafter, the self-ignition occurrence time is detected based on the output of the in-cylinder pressure sensor 35, and the self-ignition delay angle is calculated based on the self-ignition occurrence time and the fuel injection start time (steps 207 and 208).

  Thereafter, the process proceeds to step 209, and in the learning value map of the self-ignition delay angle, the learning value of the self-ignition delay angle in the learning region corresponding to the current operating condition is updated with the current self-ignition delay angle, Learn the self-ignition delay angle for each driving condition. The process of step 209 serves as a self-ignition delay period learning means in the claims.

  In the third embodiment described above, the self-ignition delay angle is learned for each operation condition, and when the fuel injection start timing is set, the current operation condition is selected from the map of the learned value of the self-ignition delay angle. Since the learning value of the corresponding self-ignition delay angle is selected and used, fuel injection is performed so that the self-ignition occurrence timing matches the ignition timing based on the learning value of the self-ignition delay period corresponding to the current operating conditions. The start time can be set with high accuracy.

  In the third embodiment, the self-ignition delay angle calculated based on the actual self-ignition occurrence time detected after fuel injection is learned. However, the prediction is based on the self-ignition delay time predicted before fuel injection. The self-ignition delay angle may be learned.

  In the first to third embodiments, the present invention is applied to a center injection type in-cylinder injection engine in which the fuel injection valve 19 is disposed so as to inject fuel into the combustion chamber 32 from substantially above the center of the combustion chamber 32. However, the present invention may be applied to an in-cylinder injection engine in which a fuel injection valve is arranged so as to inject fuel into the combustion chamber from the side of the combustion chamber (for example, near the intake port).

  In addition, the present invention can be applied to a dual-injection engine having both a fuel injection valve for intake port injection and a fuel injection valve for in-cylinder injection.

It is a schematic block diagram of the whole engine control system in Example 1 of this invention. It is a longitudinal cross-sectional view of a fuel injection valve and its peripheral part. It is a figure explaining the setting method of fuel injection start time. 3 is a flowchart for explaining a flow of processing of a fuel injection control routine of Embodiment 1. 7 is a flowchart for explaining a flow of processing of a fuel injection control routine of Embodiment 2. It is a figure explaining the detection method of self-ignition generation time. 10 is a flowchart for explaining a flow of processing of a fuel injection control routine of Embodiment 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 15 ... Throttle valve, 19 ... Fuel injection valve, 20 ... Spark plug, 25 ... Exhaust pipe, 28 ... Crank angle sensor, 29 ... Intake temperature sensor, 30 ... ECU ( Pre-ignition suppression control means, self-ignition delay period determination means, self-ignition delay period learning means), 35 ... cylinder pressure sensor

Claims (10)

In a fuel injection control device for a direct injection internal combustion engine that directly injects fuel into a combustion chamber of the internal combustion engine,
Pre-ignition suppression control that suppresses pre-ignition by adopting a compression stroke injection mode that sets the fuel injection start timing so that the self-ignition generation timing at which self-ignition of the air-fuel mixture occurs in the compression stroke of the internal combustion engine coincides with the ignition timing A fuel injection control device for a direct injection internal combustion engine, comprising a pre-ignition suppression control means to be executed. A self-ignition delay period determining means for determining a self-ignition delay period from the start of fuel injection to the occurrence of self-ignition during the compression stroke injection mode;
The pre-ignition suppression control means sets the fuel injection start timing so as to make the self-ignition occurrence timing coincide with the ignition timing based on the self-ignition delay period determined by the self-ignition delay period determination means. The fuel injection control device for a direct injection internal combustion engine according to claim 1, further comprising means for executing the following. The self-ignition delay time determination means predicts a self-ignition delay time that is a time from the start of fuel injection to the occurrence of self-ignition based on the intake air temperature and load of the internal combustion engine, and the self-ignition delay time and the internal combustion engine Means for predicting, as the self-ignition delay period, a self-ignition delay angle that is a crank angle from the start of fuel injection to the occurrence of self-ignition based on the rotation speed of
The pre-ignition suppression control means sets the fuel injection start timing so as to make the self-ignition occurrence timing coincide with the ignition timing based on the self-ignition delay angle predicted by the self-ignition delay period determination means. The fuel injection control device for a direct injection internal combustion engine according to claim 2, further comprising means for executing the following. A cylinder pressure sensor for detecting the cylinder pressure of the internal combustion engine;
The self-ignition delay period determination means detects self-ignition occurrence timing based on the output of the in-cylinder pressure sensor, and self-ignition occurs from the start of fuel injection based on the self-ignition occurrence timing and the fuel injection start timing. Means for calculating a self-ignition delay angle which is a crank angle until the self-ignition delay period,
The pre-ignition suppression control means sets the fuel injection start timing so as to make the self-ignition occurrence timing coincide with the ignition timing based on the self-ignition delay angle calculated by the self-ignition delay period determination means. The fuel injection control device for a direct injection internal combustion engine according to claim 2, further comprising means for executing the following. A self-ignition delay period learning means for learning the self-ignition delay period determined by the self-ignition delay period determination means for each driving condition;
The pre-ignition suppression control means selects a learning value of the self-ignition delay period corresponding to the current operating condition from the learning data of the self-ignition delay period learned by the self-ignition delay period learning means, and the self-ignition delay 5. The means for executing the pre-ignition suppression control by setting a fuel injection start timing so that the self-ignition occurrence timing coincides with the ignition timing based on a learning value of a period. A fuel injection control device for a cylinder injection internal combustion engine according to any one of the above.   The fuel injection control device for a direct injection internal combustion engine according to any one of claims 1 to 5, wherein the preg suppression control means includes means for executing the preg suppression control when the internal combustion engine is started.   The fuel of the direct injection internal combustion engine according to any one of claims 1 to 6, wherein the pre-ignition suppression control means includes means for executing the pre-ignition suppression control during low rotation and high load operation of the internal combustion engine. Injection control device.   The in-cylinder injection internal combustion engine according to any one of claims 1 to 7, wherein the pre-ignition suppression control means includes means for executing the pre-ignition suppression control when an intake air temperature of the internal combustion engine is equal to or higher than a predetermined value. Fuel injection control device.   The in-cylinder engine according to any one of claims 1 to 8, wherein the pre-ignition suppression control means includes means for executing the pre-ignition suppression control when the fuel supplied to the internal combustion engine is a fuel having a low octane number. A fuel injection control device for an injection internal combustion engine.   10. The invention is applied to a center injection type in-cylinder injection internal combustion engine in which a fuel injection valve is arranged so as to inject fuel into the combustion chamber from substantially above the center of the combustion chamber of the internal combustion engine. A fuel injection control device for a cylinder injection internal combustion engine according to any one of the above.

Images