JP4228823B2 - In-cylinder injection spark ignition internal combustion engine fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device for an in-cylinder injection spark ignition type internal combustion engine provided with a fuel injection valve for directly injecting fuel into a combustion chamber for each cylinder.

In an in-cylinder injection spark ignition internal combustion engine, the fuel injection valve is disposed so that its injection hole faces the combustion chamber. Thereby, fuel is directly injected into the combustion chamber.
2. Description of the Related Art Conventionally, a fuel injection control device for an internal combustion engine of this type is known as disclosed in Patent Document 1. This conventional fuel injection control device detects the piston position while the engine is stopped, and performs fuel injection immediately after the start of the engine to a cylinder that is stopped in the compression stroke immediately before the start of the engine. In a cylinder stopped in the compression stroke, when the piston of the cylinder is raised by cranking, the in-cylinder pressure and temperature are increased, and the conditions that allow spark ignition are immediately met. Therefore, it is possible to accelerate the initial explosion by performing spark ignition on the fuel injection immediately after the start of cranking. On the other hand, depending on the engine operation state, self-ignition occurs before the spark ignition, and the self-ignition may cause problems such as generation of knocking noise. Therefore, in the fuel injection control device described in the above document, combustion by normal spark ignition is realized by controlling the fuel injection amount so that self-ignition does not occur during the fuel injection.

  By the way, in general, the start of fuel injection at the time of engine start is different from the above, after the crank position is determined based on the output signal of a sensor for detecting the crank position. That is, in a general in-cylinder injection spark ignition internal combustion engine, the crank position is determined prior to the start of fuel injection in order to appropriately control the fuel injection timing.

  In this way, when the crank position is determined after cranking is started and fuel injection is started thereafter, fuel injection is not performed at the beginning of cranking. However, it has been found that even when such fuel injection is not performed, self-ignition occurs and problems such as the generation of knocking noise can occur.

That is, in a cylinder injection spark ignition type internal combustion engine, the fuel injection valve injection hole faces the combustion chamber as described above, so that fuel remaining inside the fuel injection valve leaks into the combustion chamber while the engine is stopped. There is. If such fuel leaks in the combustion chamber of a cylinder in the compression stroke or intake stroke while the engine is stopped, the piston in that cylinder rises due to cranking when the engine is restarted, increasing the in-cylinder pressure and temperature. It has become clear that the conditions for occurrence of self-ignition are satisfied and the leaked fuel may self-ignite.
JP 2001-173488 A

  The problem to be solved by the present invention is to avoid the occurrence of self-ignition caused by fuel leaking from the fuel injection valve into the combustion chamber while the engine is stopped.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
The invention according to claim 1 is applied to an in-cylinder injection spark ignition type internal combustion engine provided with a fuel injection valve for each cylinder for directly injecting fuel into the combustion chamber, and an output signal of a sensor for detecting a crank position when the engine is started. In the fuel injection control device for an in-cylinder spark-ignition internal combustion engine, which determines a crank position based on the engine and starts normal fuel injection for combustion by spark ignition from the fuel injection valve after the determination. A determination means for determining a specific cylinder that may generate self-ignition at the time of cranking before starting normal fuel injection based on a piston position when the engine is stopped, and a predetermined condition relating to the occurrence of self-ignition determining whether satisfied, self-on condition the establishment of the predetermined condition, the combustion chamber of the the determined specific cylinder against the cranking, via the fuel injection from the fuel injection valve As previously supplying the amount of fuel that the fuel concentration beyond the range that may occur in the fire, provides an instruction signal to the fuel injection valve of the specific cylinder, pre-injection for performing fuel injection for said specific cylinder The gist is to provide execution means.

In the above-described configuration, a predetermined condition relating to the occurrence of self-ignition is applied to a specific cylinder that may cause self-ignition due to fuel leakage from the fuel injection valve when the engine is stopped as described above into the combustion chamber. Fuel concentration exceeding a range where self-ignition may occur through fuel injection from the fuel injection valve of the specific cylinder in cranking on the condition that the predetermined condition is satisfied. The amount of fuel to be supplied is supplied. As a result, the fuel concentration in the combustion chamber of the specific cylinder can be increased during cranking, the self-ignition condition is not established, and the occurrence of self-ignition can be avoided. Further, such fuel injection is executed only for a specific cylinder that may cause self-ignition, and therefore, unnecessary fuel consumption is suppressed.
In addition, self-ignition occurs under certain conditions such as when the combustion chamber is in a high temperature environment during cranking. Therefore, if fuel injection to a specific cylinder by the pre-injection execution means is executed on the condition that a predetermined condition relating to the occurrence of self-ignition is satisfied as in the above configuration, unnecessary fuel injection is avoided and unnecessary fuel is injected. Consumption can be reduced.

  According to a second aspect of the present invention, in the fuel injection control apparatus for an in-cylinder injection spark ignition type internal combustion engine according to the first aspect, the determining means is configured to perform the compression stroke before the exhaust stroke after the cranking starts. The gist of the present invention is to determine the cylinders that meet the above-mentioned specific cylinders.

  In the above configuration, the cylinder that reaches the compression stroke before the exhaust stroke after the start of cranking is determined as the specific cylinder, and the fuel injection by the pre-injection executing means is executed. In such a cylinder, fuel leaking from the fuel injection valve into the combustion chamber while the engine is stopped is not scavenged from the combustion chamber before the compression stroke is reached, so that the probability of occurrence of self-ignition increases. Therefore, if fuel injection by the pre-injection execution means is executed with such a cylinder as the specific cylinder, the occurrence of self-ignition can be reliably avoided.

The invention according to claim 3 is the fuel injection control apparatus for an in-cylinder injection spark ignition type internal combustion engine according to claim 1 or 2 , wherein the pre-injection execution means determines whether the predetermined condition is satisfied. The gist of this is that the determination signal and provision of a command signal to the fuel injection valve of the specific cylinder on condition that the predetermined condition is satisfied are performed at the start of cranking.

  The timing at which the command signal is supplied to the fuel injection valve by the pre-injection execution means can be either when the engine is stopped or when the engine is restarted. Even if a command signal is given to the fuel injection valve at any of these timings, the fuel can be supplied into the combustion chamber of the specific cylinder through fuel injection from the fuel injection valve in cranking. However, when a command signal is given to the fuel injection valve when the engine is stopped, the condition that causes self-ignition is not satisfied when the engine is restarted because the internal combustion engine is left standing for a long time after that. There is a possibility that the fuel injection may be wasted. In this regard, as in the above configuration, it is determined whether or not the predetermined condition is satisfied at the start of cranking, and a command signal is given to the fuel injection valve of the specific cylinder on the condition that the predetermined condition is satisfied. If so, the fuel injection by the pre-injection execution means is executed only when the conditions for the occurrence of self-ignition are surely established. Therefore, according to the above configuration, unnecessary fuel consumption can be further suppressed.

The invention according to claim 4 is the fuel injection control device for a cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 3, wherein the predetermined condition is a lower limit condition of a temperature in the combustion chamber. Or a lower limit condition of a temperature parameter correlated with the temperature in the combustion chamber.

  As described above, self-ignition occurs when cranking is performed when the combustion chamber is in a high temperature environment. Therefore, by setting predetermined conditions as described above, unnecessary fuel consumption can be suitably suppressed. it can. Incidentally, the temperature parameter correlated with the temperature in the combustion chamber includes the cooling water temperature of the internal combustion engine, the intake air temperature, the outside air temperature, the temperature of the lubricating oil used for lubricating the internal combustion engine, and the like. The combustion chamber temperature may be obtained by estimating based on the history of the engine operating state before the engine is stopped, etc., in addition to the direct measurement.

The invention according to claim 5 is the fuel injection control apparatus for a cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 4 , wherein the predetermined condition includes an operation of the fuel injection valve. The gist is to include the upper limit condition of the number of times or the upper limit condition of the state quantity correlated with the number of times of operation.

  In the fuel injection valve, since the sliding contact portion proceeds, the amount of fuel leakage tends to decrease as the number of operations increases. Therefore, unnecessary fuel consumption can be suppressed by setting predetermined conditions as in the above configuration. Examples of the state quantity that correlates with the number of operations include the total number of revolutions and the total operating time of the internal combustion engine from the time of manufacture, the total travel distance from the time of manufacture of the vehicle on which the internal combustion engine is mounted, and the like.

Further, in the fuel injection control device for an in-cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 5 , the invention described in claim 6 is the upper limit of the engine stop time. The gist is to include at least one of the conditions and the lower limit condition.

  If the engine stop time is short, the fuel concentration in the combustion chamber due to fuel leaked from the fuel injection valve during engine stop may not reach the lower limit of the combustible range, and self-ignition may not occur. Therefore, by including the lower limit condition of the engine stop time in the predetermined condition, it is possible to suppress unnecessary fuel consumption in such a case. In addition, if the engine stop time is long, the fuel concentration in the combustion chamber due to the leaked fuel exceeds the upper limit of the combustible range. Therefore, it is also unnecessary to include the upper limit condition of the engine stop time in the predetermined condition. Fuel consumption can be suppressed. Of course, if both the upper limit condition and the lower limit condition of the engine stop time are included in the predetermined condition, unnecessary fuel consumption can be further suppressed.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS.
An internal combustion engine 10 shown in FIG. 1 is configured as an in-cylinder injection spark ignition type internal combustion engine in which a V-type 6-cylinder arrangement is adopted. A fuel injection valve 12 is disposed in the combustion chamber 11 of each cylinder of the internal combustion engine 10 so that the injection hole faces the combustion chamber 11, and the fuel is directly injected into the combustion chamber 11. ing. A spark plug 13 is attached to each cylinder of the internal combustion engine 10, and the fuel injected from the fuel injection valve 12 is ignited by a spark by being supplied with a high-voltage current generated by the igniter 13a. Yes.

  In addition, the internal combustion engine 10 is provided with a starter motor 15 as an auxiliary machine that imparts an initial rotation necessary for starting the engine to a crankshaft 14 that is an engine output shaft. Further, a crank position rotor 16 having a plurality of teeth formed on the outer periphery thereof is provided on the crankshaft 14 so as to be integrally rotatable, and a crank position sensor 17 is disposed in the vicinity thereof. The crank position sensor 17 is configured as an electromagnetic pickup that generates an electromotive force when the teeth pass in the vicinity thereof as the crank position rotor 16 rotates.

  Various controls of the internal combustion engine 10 are performed by the electronic control unit 20. The electronic control unit 20 includes a CPU that executes various processes, a memory that stores programs and information necessary for control, and the like. The electronic control unit 20 is also provided with a backup RAM 21 for storing and holding necessary information while the engine is stopped, and a timer 22 for measuring the engine stop time.

  In addition to the crank position sensor 17, the electronic control unit 20 receives detection signals from various sensors that detect the rotational phase of the camshaft, that is, the engine operation state such as the cam position sensor 23 for detecting the cam position. Yes. In the present embodiment, as the various sensors, there are provided temperature sensors such as a water temperature sensor 24 that detects the cooling water temperature THW, an intake air temperature sensor 25 that detects the intake air temperature THA, and an outside air temperature sensor 26 that detects the outside air temperature THAIR. Yes. The cam position sensor 23 is configured as an electromagnetic pickup similar to the crank position sensor 17, and the teeth provided on the outer periphery of the cam position rotor for detecting the cam position provided on the camshaft are used to rotate the rotor. Along with that, an electromotive force is generated by passing through the vicinity.

  On the other hand, an ignition switch (IG) and a starter switch (STA) are connected to the electronic control unit 20, and the operation status of these switches can be detected. Then, the electronic control unit 20 generates the high-pressure power necessary for spark ignition and supplies it to the spark plug 13 based on the detection signals of these sensors and the operation state of the switch, and the like. A command signal is output to, and fuel injection control, ignition control, and the like are performed.

  Further, a relay circuit 28 that opens and closes a power feeding path from the in-vehicle power supply 27 to the starter motor 15 is connected to the electronic control unit 20. Then, the electronic control unit 20 opens and closes the relay circuit 28 according to the operation status of the starter switch, and allows / cuts off the power supply to the starter motor 15.

The internal combustion engine 10 is started in the following manner.
First, when the driver closes the ignition switch, the electronic control unit 20 is activated, and various processes for preparing for starting the engine are executed. At this time, pre-injection control described later is executed as part of such processing.

  Subsequently, when it is detected that the driver has closed the starter switch, the electronic control unit 20 closes the relay circuit 28 and starts supplying power to the starter motor 15. The starter motor 15 to which power is supplied generates a rotational driving force to give the crankshaft 14 an initial rotation necessary for starting the engine. Thereby, cranking is performed and the engine start is started.

  When cranking is performed and the crankshaft 14 is rotated, the electronic control unit 20 determines the crank position based on the detection signals of the crank position sensor 17 and the cam position sensor 23. Specifically, the determination of the crank position is performed in the following manner.

  FIG. 2 shows waveform examples of the NE signal and the G2 signal obtained by shaping the output signals of the crank position sensor 17 and the cam position sensor 23 into rectangular waves, along with the transition of each cylinder stroke for each crank position. Has been. The shaping of the output signal here is performed by a waveform shaping circuit provided in the electronic control unit 20, and these shaped signals are inputted to the CPU.

  Since a part of the outer periphery of the crank position rotor 16 is missing a tooth, as shown in the figure, the NE signal includes a tooth for each rotation of the crankshaft 14 (crank angle 360 °). A signal corresponding to the multiplied portion, that is, a missing tooth signal is output. On the other hand, since the camshaft is rotated once every two rotations of the crankshaft 14, and only one tooth is formed on the cam position rotor, the G2 signal is shown surrounded by a broken-line circle in FIG. Such a pulse signal corresponding to the passage of the tooth is output at every crank angle of 720 °.

  Here, for one of the two missing tooth signals output during one cycle of the internal combustion engine 10, that is, during a crank angle of 720 °, the pulse signal based on the output of the cam position sensor 23 immediately after the output. Is output, while the other is not output with such a pulse signal. Therefore, the electronic control unit 20 first detects the missing tooth signal after the engine is started, and then confirms whether or not the pulse signal is detected in a predetermined cylinder discrimination section thereafter, thereby determining the crank position.

  The fuel injection timing cannot be appropriately controlled during the period from the start of cranking to the determination of the crank position. Therefore, the electronic control unit 20 starts normal fuel injection for combustion by spark ignition after the crank position is determined.

  When normal fuel injection is thus started, the electronic control unit 20 outputs a command signal to the fuel injection valve 12 of each cylinder to inject an appropriate amount of fuel at an appropriate time. Further, the electronic control unit 20 outputs a command signal to the igniter 13a so that spark ignition by the spark plug 13 is performed at an appropriate time for the fuel injection. When the complete explosion is performed and the internal combustion engine 10 can rotate by itself, the electronic control unit 20 opens the relay circuit 28, stops the power supply to the starter motor 15, and cancels the cranking.

  In the present embodiment, the crank position is determined, and in order to avoid the self-ignition caused by the leaked fuel from the fuel injection valve 12 as described above in the period before the normal fuel injection is started, The electronic control unit 20 executes the pre-injection control as a preparation process for starting after startup. The pre-injection control is performed according to the following procedure.

  First, after the start-up, the electronic control unit 20 determines the specific cylinder that may cause the self-ignition based on the piston position (crank position) when the engine is stopped. In order to make such a determination, the electronic control unit 20 stores the last detected piston position in the backup RAM 21 when the engine is stopped.

Here, the following cylinders are determined as specific cylinders.
In the cylinder that reaches the exhaust stroke before the compression stroke after the start of the cranking, the fuel leaked before reaching the compression stroke is discharged from the combustion chamber 11 in the exhaust stroke, so the probability of occurrence of self-ignition is low. Become. On the other hand, in the cylinder that reaches the compression stroke before the exhaust stroke after the start of cranking, the leaked fuel reaches the compression stroke without being discharged from the combustion chamber 11, so the probability of occurrence of self-ignition is high. Become. According to the transition of the stroke of each cylinder shown in FIG. 2 for each crank position, when the internal combustion engine 10 is stopped at a crank position of 120 ° CA, it can be said that the cylinder is highly likely to generate self-ignition upon restart. The three cylinders are the sixth cylinder # 6, the first cylinder # 1, and the second cylinder # 2.

  However, in a cylinder stopped in the middle of the compression stroke, the compression amount of the cylinder gas immediately after cranking is small, and the conditions for occurrence of self-ignition may not be satisfied. Therefore, a cylinder that is stopped at a position that involves compression that causes self-ignition before the exhaust stroke, for example, compression with a crank angle of 60 ° or more, is a cylinder that has a high probability of occurrence of self-ignition.

  However, when the engine is stopped, the crankshaft 14 slightly moves between the last detection of the piston position and the restart, or the crankshaft 14 slightly reversely rotates immediately before it is completely stopped. In some cases, the last detected piston position does not necessarily accurately represent the crank position at the time of restart. Therefore, in the present embodiment, in consideration of such an error, a cylinder stopped at a position with compression of a crank angle of 30 ° or more at the last detected piston position is replaced with a cylinder having a high probability of occurrence of self-ignition. To be certified as. In the internal combustion engine 10 of this embodiment having six cylinders, three cylinders correspond to such cylinders.

  According to the results of experiments by the inventors, among the above-mentioned three cylinders accompanied by compression with a crank angle of 30 ° or more before the exhaust stroke, the cylinder that reaches the third compression stroke (hereinafter referred to as the third cylinder). As for the compression cylinder), it has been confirmed that self-ignition hardly occurs. This is because the third compression cylinder is stopped near the exhaust top dead center, and intake air is introduced into the combustion chamber 11 before the compression stroke, and the temperature in the combustion chamber 11 is lowered, or the engine is stopped. It is considered that the exhaust valve and the intake valve are opened and the combustion chamber 11 is not sealed, so that the leaked fuel vapor is discharged from the combustion chamber 11 to some extent.

  Therefore, in the present embodiment, after the cranking is started, among the cylinders with compression with a crank angle of 30 ° or more before the exhaust stroke, the cylinder that first reaches the compression stroke (hereinafter referred to as the first compression cylinder). In addition, the cylinder that reaches the second compression stroke (hereinafter referred to as the second compression cylinder) is determined as the specific cylinder. FIG. 3 shows the first and second cylinders determined as the specific cylinders for each piston position (crank position) when the engine is stopped, according to the transition of the stroke of each cylinder shown in FIG. 2 for each crank position. A second compression cylinder is shown.

  When the specific cylinder is determined in this way, the electronic control unit 20 determines whether or not the internal combustion engine 10 at that time is in a state of causing the occurrence of self-ignition, that is, whether or not the self-ignition condition is satisfied. Do. The contents of the self-ignition conditions here will be described later.

  When it is determined that the self-ignition condition is satisfied, the electronic control unit 20 performs cranking and supplies fuel to each combustion chamber 11 of the determined specific cylinder through fuel injection from the fuel injection valve 12. An injection command signal is output to the fuel injection valve 12 of the specific cylinder so as to be supplied. The injection command at this time is performed so that a sufficient amount of fuel is injected in the combustion chamber 11 to make the fuel concentration exceeding the upper limit of the combustible range.

  When such fuel injection is performed, the inside of the combustion chambers 11 of these specific cylinders is in an overrich state in which the fuel concentration exceeds the upper limit of the combustible range. Therefore, the occurrence of self-ignition due to the leaked fuel while the engine is stopped is avoided. That is, in the pre-injection control, the fuel that is not used for combustion is injected and supplied to the specific cylinders that are likely to generate self-ignition and the combustion chamber 11 is overrich in the start of cranking. By doing so, the occurrence of self-ignition is avoided.

  The fuel injection for the specific cylinder may be performed simultaneously for both the first compression cylinder and the second compression cylinder or sequentially with a time difference. In any case, if fuel injection is performed so that the combustion chamber 11 of the cylinder is in an overrich state before the specific cylinder reaches the compression stroke, the occurrence of self-ignition can be avoided.

  FIG. 4 is a flowchart showing the processing procedure of the pre-injection control at the time of starting the engine. A series of processes shown in this flowchart are sequentially executed by the electronic control unit 20 after the ignition switch is closed (ON).

  When the ignition switch is closed and the processing of this flowchart is started, the electronic control unit 20 first determines a specific cylinder in step S10 based on the piston position when the engine is stopped. In order to perform this processing, the memory of the electronic control unit 20 stores in advance the correspondence between the piston position when the engine is stopped as illustrated in FIG. 3 and the first and second compression cylinders that are the specific cylinders. Yes.

  Subsequently, in step S20, the electronic control unit 20 waits for execution of the subsequent step S30 until it is detected that the starter switch is closed (ON), and then in step S30, the self-ignition condition is satisfied. It is determined whether or not it is established. If the self-ignition condition is satisfied (YES), the electronic control unit 20 advances the process to step S40, and if not (NO), advances the process to step S50.

  In step S40, the electronic control unit 20 outputs a command signal to the fuel injection valve 12 of the determined specific cylinder so as to execute fuel injection. After the fuel is injected and supplied so that the combustion chamber 11 of the specific cylinder is in an overrich state in this way, the electronic control unit 20 advances the process to step S50.

  In step S50, the electronic control unit 20 once waits for normal fuel injection to be performed for combustion based on spark ignition until the crank position is determined based on the detection result of the crank position sensor 17, and then pre-injection. Processing related to control is terminated, and normal fuel injection control is started.

  FIG. 5 is a flowchart showing details of processing of the electronic control unit 20 related to the self-ignition condition determination in step S30. Since self-ignition is likely to occur when the inside of the combustion chamber 11 at the start of cranking is in a high temperature environment, here, the coolant temperature THW, the intake air temperature THA, and the outside that correlate with the combustion chamber temperature at the start of cranking. When the three temperature parameters of the temperature THAIR satisfy the lower limit conditions set for each, it is determined that the self-ignition condition is satisfied.

Specifically, in steps S31 to S33 in the figure, the electronic control unit 20 has the following lower limit conditions (a1) to (a3), that is, (a1) cooling water temperature THW ≧ determination value A (for example, 85 ° C.).
(A2) Intake air temperature THA ≧ determination value B (for example, 70 ° C.)
(A3) Outside air temperature THAIR ≧ determination value C (for example, 35 ° C.)
It is determined whether or not each holds.

  If all of these lower limit conditions (a1) to (a3) are satisfied, the electronic control unit 20 determines in step S34 that the self-ignition condition is satisfied, and the lower limit conditions (a1) to (a If any one of a3) is not established, it is determined in step S35 that the self-ignition condition is not established.

  In the present embodiment described above, step S10 in FIG. 4 corresponds to the process of the determination unit, and steps S30 and S40 in FIG. 4 correspond to the process of the pre-injection execution unit. The self-ignition condition corresponds to a predetermined condition relating to the occurrence of the self-ignition.

According to this embodiment, the following effects can be obtained.
(1) In cranking, fuel is supplied through fuel injection from the fuel injection valve 12, and the combustion chamber of a specific cylinder that may cause self-ignition is overrich, so that self-ignition occurs. Can be avoided.

(2) Since the fuel injection is limited to a specific cylinder that may cause self-ignition, unnecessary fuel consumption can be suppressed.
(3) Since the fuel is injected only when the self-ignition condition based on the lower limit condition of the temperature parameter correlated with the combustion chamber temperature is satisfied, the interior of the combustion chamber 11 is not in a high temperature environment at the time of cranking. Unnecessary fuel consumption in the situation where it does not occur can be prevented.

  (4) By determining whether the self-ignition condition is satisfied at the start of cranking, the fuel injection can be performed more reliably only when the self-ignition occurrence condition is satisfied. That is, unnecessary fuel injection in a situation where self-ignition does not occur can be avoided more reliably.

(Other embodiments)
Subsequently, a modification of the above embodiment will be described focusing on differences from the above embodiment.
(Modification 1)
The timing for giving a command signal to the fuel injection valve for avoiding the occurrence of self-ignition may be when the engine is stopped, in addition to the above-described engine restart. Even in this case, the combustion chamber of a specific cylinder that may cause self-ignition upon cranking can be brought into an overrich state by supplying fuel through fuel injection from the fuel injection valve.

  FIG. 6 is an example of a flowchart showing a processing procedure of such pre-injection control when the engine is stopped. A series of processing shown in this flowchart is sequentially executed by the electronic control unit 20 from the time when the engine is stopped.

  When the process of this control is started, first, in step S110, the electronic control unit 20 determines a specific cylinder that may cause self-ignition upon restart, based on the piston position when the engine is stopped.

  Subsequently, in step S120, the electronic control unit 20 determines whether or not the self-ignition condition is satisfied. As the self-ignition condition here, as in the above-described embodiment, a condition based on the lower limit condition of the temperature parameter correlated with the combustion chamber temperature such as the cooling water temperature THW, the intake air temperature THA, and the outside air temperature THAIR can be set. . However, considering the temperature drop during engine stop until restart, the lower limit condition of the coolant temperature THW is higher than the lower limit value of the coolant temperature during cranking, which may cause self-ignition. It is desirable to set (for example, 95 ° C.). In addition, as a determination value of the lower limit condition of the intake air temperature THA, taking into account that the internal combustion engine 10 has been operating until just before that and fresh air has been introduced into the intake passage, the occurrence of self-ignition It is desirable to set a value (for example, 45 ° C.) lower than the lower limit value of the intake air temperature at the time of cranking that may be incurred.

  If it is determined that the self-ignition condition is satisfied (S120: YES), the electronic control unit 20 advances the process to step S130. In step S130, the determined fuel injection valve 12 of the specific cylinder is applied. A fuel injection command signal is output, and fuel is injected and supplied into the combustion chamber 11 of the cylinder. After that, the electronic control unit 20 opens the ignition switch (OFF), and temporarily stops its operation until restarting.

  On the other hand, when it is determined that the self-ignition condition is not established (S120: NO), the electronic control unit 20 opens the ignition switch as it is and temporarily stops its operation until restarting.

  As described above, even when the command signal to the fuel injection valve 12 for avoiding the occurrence of self-ignition is given when the engine is stopped, the same effects as the above (1) to (3) can be obtained. Further, when fuel injection related to the pre-injection control is performed when the engine is stopped, the injected fuel evaporates while the engine is stopped and is diffused into the air in the combustion chamber 11. The air-fuel mixture in the combustion chamber 11 becomes more uniform. Therefore, it becomes possible to more surely suppress the self-ignition of the partial combustible mixture.

(Modification 2)
If the engine stop time until the restart is short, the fuel concentration in the combustion chamber 11 due to the fuel leaked from the fuel injection valve 12 during the engine stop does not reach the lower limit of the combustible range, and self-ignition may not occur. Further, if the engine stop time is long, the fuel concentration in the combustion chamber 11 due to the leaked fuel exceeds the upper limit of the combustible range, so that self-ignition does not occur. Therefore, if the self-ignition condition includes at least one of the upper limit condition and the lower limit condition of the engine stop time, unnecessary fuel consumption in a situation where no self-ignition occurs can be further suppressed.

  FIG. 7 shows an example of the self-ignition condition determination process including the upper limit condition and lower limit condition of Tsoak for such engine stop time. The process shown in FIG. 4 is executed by the electronic control unit 20 instead of the process shown in FIG. 5 during the process in step S30 shown in FIG.

  When the process of FIG. 6 is started, first, in step S231, the electronic control unit 20 determines whether or not the lower limit conditions for the respective temperature parameters are satisfied as in steps S31 to S33 of FIG. That is, here, it is determined whether any one of the coolant temperature THW, the intake air temperature THA, and the outside air temperature THAIR satisfies the respective lower limit conditions.

  In step S232, the electronic control unit 20 determines whether the engine stop time Tsoak is greater than or equal to the determination value D and less than the determination value E. Here, in the determination value D, the engine stop time (for example, 5 minutes) necessary for setting the fuel concentration in the combustion chamber 11 to the lower limit value of the combustible range due to the leaked fuel is set as the value. The determination value E is also set as the value of the engine stop time (for example, 80 minutes) necessary for causing the fuel concentration to exceed the upper limit value of the combustible range. The engine stop time Tsoak is measured by the timer 22 incorporated in the electronic control unit 20.

  When the electronic control unit 20 makes an affirmative determination in both step S231 and step S232, the electronic control unit 20 determines that the self-ignition condition is satisfied in step S233 and makes a negative determination in any of them. In step S234, it is determined that the self-ignition condition is not established, and the process is terminated.

(Modification 3)
The fuel injection valve 12 tends to decrease the amount of fuel leakage each time the number of operations thereof increases because the sliding contact portion advances. Therefore, when the number of operations of the fuel injection valve 12 exceeds a certain number, self-ignition hardly occurs. Therefore, in the self-ignition condition, the upper limit condition of the number of operations of the fuel injection valve 12 or a state quantity correlated with the number of operations, for example, the total number of revolutions and the total operating time of the internal combustion engine 10 from the time of manufacture, or the internal combustion engine 10 If an upper limit condition such as the total travel distance from the time of manufacture of the vehicle on which the vehicle is mounted is included, unnecessary fuel consumption can be suppressed.

  FIG. 8 is an example of a self-ignition condition determination process when the upper limit condition of the number of actuations of the fuel injection valve 12 is included in the self-ignition condition. The process of FIG. 5 is also executed by the electronic control unit 20 instead of the process of FIG. 5 during the process of step S30 of FIG.

  When the process of FIG. 6 is started, the electronic control unit 20 performs the same determination as in step S231 of FIG. 6 in step S331. In step S332, the electronic control unit 20 determines that the number of operations of the fuel injection valve 12 is less than a determination value F (for example, 3 million times), which is a lower limit value of the number of operations in which the leakage amount is reduced to the extent that self-ignition is not generated. It is determined whether or not. When the electronic control unit 20 makes an affirmative determination in both step S331 and step S332, it makes a determination that the self-ignition condition is satisfied in step S333, and makes a negative determination in any of them. In step S334, it is determined that the self-ignition condition is not established, and the process is terminated.

  The upper limit condition for the number of operations of the fuel injection valve 12 or the upper limit condition for the state quantity correlated with the number of operations can be included in the self-ignition condition in the pre-injection control when the engine is stopped according to the second modification. In that case, unnecessary fuel consumption can be similarly suppressed.

(Modification 4)
The ease with which self-ignition occurs due to the leaked fuel also varies depending on the properties of the fuel used. For example, when using a high octane fuel, self-ignition is less likely to occur. Therefore, in accordance with the properties of the fuel being used, it is determined whether or not fuel injection can be performed to avoid the occurrence of self-ignition, and the lower and upper limit conditions of each parameter in the self-ignition condition are changed. Thus, unnecessary fuel consumption can be further suppressed.

  In many of the in-cylinder injection spark ignition internal combustion engines, ignition timing knock control (KCS) is performed to bring the ignition timing closer to the maximum torque point while avoiding the occurrence of knocking during engine operation. In such knock control, while detecting the occurrence of knocking, the ignition timing is advanced within a range in which the occurrence of knocking can be avoided based on the detection result. Therefore, the amount of advancement of the ignition timing in such knock control, or the learned value thereof, is an index value for the ease of occurrence of knocking in the fuel being used, that is, the ease of occurrence of self-ignition. Therefore, unnecessary fuel consumption can be suppressed by including the conditions based on the advance amount of the ignition timing in the knock control in the self-ignition conditions.

  FIG. 9 shows an example of a self-ignition condition determination process when a condition based on the KCS advance learning amount, which is a learned value of the advance amount of the ignition timing in such knock control, is included in the self-ignition condition. The process of FIG. 5 is also executed by the electronic control unit 20 instead of the process of FIG. 5 during the process of step S30 of FIG. The larger the value of the KCS advance learning amount, the lower the occurrence frequency of knocking during engine operation, that is, the higher the octane number of the fuel in use.

  Now, when the process of the same figure is started, the electronic control apparatus 20 will perform determination similar to step S231 of FIG. 6 in step S431. In step S432, the electronic control unit 20 determines that the value of the KCS advance learning amount is a lower limit value (for example, 10) indicating that the fuel having a high octane number is being used to the extent that self-ignition due to the leaked fuel is not generated. It is determined whether or not the determination value G is less than CA. When the electronic control unit 20 makes an affirmative determination in either step S431 or step S432, it makes a determination that the self-ignition condition has been established in step S433, and makes a negative determination in any of them. In step S434, it is determined that the self-ignition condition is not established, and the process is terminated.

  Note that such conditions due to the fuel properties can be included in the self-ignition conditions in the pre-injection control when the engine is stopped according to the modified example 2, and in that case, unnecessary fuel consumption can be similarly suppressed.

The embodiment described above and its modifications can be modified as follows.
In the above embodiment, only the first compression cylinder and the second compression cylinder are determined as the specific cylinders. However, if necessary, the third compression cylinder may be added to the specific cylinders. However, the number of cylinders determined as specific cylinders and the conditions thereof are determined by the number of cylinders of the internal combustion engine to be applied, and it is desirable to change appropriately according to the internal combustion engine to be applied.

  -Based on the upper limit condition of the engine stop time described in the above-described modified examples 2 to 4 and the lower limit condition thereof, the number of operations of the fuel injection valve 12, or the upper limit condition of the state quantity correlated with the number of operations, and the properties of the fuel Two or more of the conditions may be included in the self-ignition condition. In addition, the upper limit condition of the state quantity that correlates with the number of operations of the fuel injection valve 12 or the number of operations and the condition based on the properties of the fuel are both set as the self-ignition conditions related to the pre-injection control at the time of engine stop according to the first modification. It can also be included.

  One or more of the lower limit conditions of each temperature parameter correlated with the combustion chamber temperature, that is, the lower limit conditions of the cooling water temperature THW, the intake air temperature THA, and the outside air temperature THAIR may be omitted from the self-ignition conditions.

-The combustion chamber temperature may be directly measured, and the lower limit condition of the measured value may be included in the self-ignition condition.
Further, the combustion chamber temperature may be estimated from the operation history of the internal combustion engine 10 before the engine is stopped, and the lower limit condition of the estimated value may be included in the self-ignition condition.

The schematic diagram which shows the whole structure about one Embodiment of this invention. The figure which shows together the transition of the stroke example of each cylinder for every crank position, and the waveform example of NE signal and G2 signal. The figure which shows the correspondence of the piston position at the time of an engine stop, and the cylinder corresponding to 1st and 2nd compression. The flowchart of the pre-injection control at the time of the engine start applied to the said embodiment. The flowchart of the self-ignition condition determination process in the same pre-injection control. The flowchart of the pre-injection control at the time of the engine stop applied to the modification 1 of the said embodiment. The flowchart of the self-ignition condition determination process applied to the modification 2 of the said embodiment. The flowchart of the self-ignition condition determination process applied to the modification 3 of the said embodiment. The flowchart of the self-ignition condition determination process applied to the modification 4 of the said embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... In-cylinder injection spark ignition internal combustion engine, 11 ... Combustion chamber, 12 ... Fuel injection valve, 13 ... Spark plug, 13a ... Igniter, 14 ... Crankshaft, 15 ... Starter motor, 16 ... Crank position rotor, 17 ... Crank Position sensor, 20 ... electronic control device, 21 ... backup RAM, 22 ... timer, 23 ... cam position sensor, 24 ... water temperature sensor, 25 ... intake air temperature sensor, 26 ... outside air temperature sensor, 27 ... vehicle power supply, 28 ... relay circuit .

Claims (6)

Applied to an in-cylinder injection spark ignition type internal combustion engine provided with a fuel injection valve for each cylinder directly injecting fuel into the combustion chamber, the crank position is determined based on an output signal of a sensor that detects the crank position when the engine is started, In the fuel injection control device for a cylinder injection spark ignition internal combustion engine that starts normal fuel injection for combustion by spark ignition from the fuel injection valve after the determination,
Determining means for determining a specific cylinder that may cause self-ignition during cranking before starting the normal fuel injection based on a piston position when the engine is stopped;
It is determined whether or not a predetermined condition relating to the occurrence of self-ignition is satisfied, and on the condition that the predetermined condition is satisfied, the fuel injection from the fuel injection valve is injected into the combustion chamber of the specific cylinder determined upon cranking as previously fueled amounts of the fuel concentration in excess of the range that may occur self-ignition through the given command signal to the fuel injection valve of a specific cylinder, executes the fuel injection for the identified cylinder Pre-injection execution means;
A fuel injection control device for an in-cylinder spark ignition internal combustion engine. 2. The fuel injection control device for an in-cylinder spark ignition internal combustion engine according to claim 1, wherein after the cranking is started, the determination unit determines a cylinder that reaches a compression stroke before an exhaust stroke as the specific cylinder. The pre-injection execution means determines whether or not the predetermined condition is satisfied, and provides a command signal to the fuel injection valve of the specific cylinder on the condition that the predetermined condition is satisfied at the start of cranking. The fuel injection control device for a cylinder injection spark ignition type internal combustion engine according to claim 1 or 2 to be implemented . The in-cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 3, wherein the predetermined condition includes a lower limit condition of a combustion chamber temperature or a lower limit condition of a temperature parameter correlated with the combustion chamber temperature . Fuel injection control device. The in-cylinder injection spark ignition type according to any one of claims 1 to 4 , wherein the predetermined condition includes an upper limit condition of an operation count of the fuel injection valve or an upper limit condition of a state quantity correlated with the operation count. A fuel injection control device for an internal combustion engine. The fuel injection control device for a cylinder injection spark ignition type internal combustion engine according to any one of claims 1 to 5, wherein the predetermined condition includes at least one of an upper limit condition and a lower limit condition of the engine stop time .

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