JP2018115563A - Control device of internal combustion engine - Google Patents

Abstract

The present invention relates to a control device for an internal combustion engine, in which ignition start control is performed with scavenging control for scavenging cylinders while ensuring engine startability when scavenging cylinders is not sufficiently performed. The purpose is to ensure engine startability at times. When engine stop is predicted, fuel injection into a cylinder is stopped, and scavenging control for scavenging the inside of a cylinder is started by opening a throttle valve. When the scavenging control is completed in the engine stop process from the start of fuel injection according to the engine stop prediction to the completion of engine stop, the ignition start control is selected when restarting the internal combustion engine 12. On the other hand, when the execution of the scavenging control is not completed during the engine stop process, the starter start control is selected when the internal combustion engine 12 is restarted. [Selection diagram] Figure 2

Description

  The present invention relates to an internal combustion engine control device, and more particularly, as engine start control, ignition start control for starting an internal combustion engine by starting fuel injection and ignition from an expansion stroke cylinder in an expansion stroke while the engine is stopped. The present invention relates to a control device for an internal combustion engine using starter start control for starting an internal combustion engine by performing fuel injection and ignition while rotating a crankshaft by an electric motor.

  For example, Patent Document 1 discloses a stop control method for an internal combustion engine. In this internal combustion engine, at the time of restart, ignition start control for starting fuel injection and ignition from an expansion stroke cylinder in an expansion stroke while the engine is stopped to start the internal combustion engine is performed. According to the above stop control method, the throttle valve provided in the intake passage is opened after the engine stop request is issued and before the rotation of the crankshaft is stopped. As a result, the amount of fresh air supplied into the cylinder during the engine stop process increases, so that scavenging of residual gas in the cylinder can be performed.

  If the scavenging in the cylinder is appropriately performed using the method described in Patent Document 1, for example, when the internal combustion engine is subsequently started, a good amount of oxygen is introduced into the expansion stroke cylinder. The ignition start control can be performed in the secured state. Thereby, engine startability at the time of ignition start control can be secured. Further, according to the ignition start control described above, it is possible to start the internal combustion engine while suppressing vibration and noise as compared with the starter start control generally used for starting the engine.

JP 2004-162707 A

  When an engine stall unexpected by the control apparatus for the internal combustion engine occurs, the time from when the engine rotation speed starts to decrease until the engine stop is completed may be shortened. When the time is short, for example, it may be difficult to sufficiently perform scavenging in the cylinder using the method described in Patent Document 1. In this case, it is difficult to secure a good amount of oxygen inside the expansion stroke cylinder when the internal combustion engine is subsequently started. For this reason, there is a possibility that the engine start using the ignition start control cannot be appropriately performed.

  The present invention has been made in view of the above-described problems, and includes scavenging control for scavenging in a cylinder while ensuring engine startability when scavenging in the cylinder cannot be sufficiently performed. An object of the present invention is to provide a control device for an internal combustion engine that can ensure engine startability during ignition start control.

  An internal combustion engine control apparatus according to the present invention includes a fuel injection valve for directly injecting fuel into a cylinder, an ignition device for igniting an air-fuel mixture, and a throttle valve provided in an intake passage; The internal combustion engine is mounted on a vehicle including an electric motor capable of rotationally driving the crankshaft of the internal combustion engine, and controls the internal combustion engine. The engine start control performed by the control device to start the internal combustion engine includes starter start control for starting the internal combustion engine by performing fuel injection and ignition while rotationally driving the crankshaft using the electric motor. And ignition start control for starting the internal combustion engine by starting fuel injection and ignition from the expansion stroke cylinder in the expansion stroke while the engine is stopped. When the engine stop is predicted, the control device stops the fuel injection into the cylinder and starts the scavenging control for scavenging the cylinder by opening the throttle valve. When the scavenging control has been completed in the engine stop process from the start of fuel injection stop to the completion of engine stop accompanying the engine stop prediction, the control device performs the ignition when restarting the internal combustion engine. On the other hand, when the start control is selected, and when the scavenging control is not completed in the engine stop process, the starter start control is selected when the internal combustion engine is restarted.

  According to the present invention, when the engine stop is predicted, the fuel injection to the cylinder is stopped, and the scavenging control for scavenging the cylinder is started by opening the throttle valve. And, when the scavenging control has been completed in the engine stop process from the start of fuel injection stop to the completion of the engine stop accompanying the engine stop prediction, the ignition start control is selected when the internal combustion engine is restarted, On the other hand, when the scavenging control is not completed, the starter start control is selected. When the scavenging control is completed, it can be expected that a sufficient amount of oxygen is filled in the expansion stroke cylinder during the ignition start control. For this reason, according to the present invention, the engine startability at the time of ignition start control accompanied with the implementation of the scavenging control for scavenging the cylinder while ensuring the engine startability when the scavenging in the cylinder cannot be sufficiently performed. Can be secured.

It is a figure for demonstrating schematically the system configuration | structure of the vehicle which concerns on Embodiment 1 of this invention. It is a flowchart which shows the procedure of the process regarding the control at the time of the engine stop performed by ECU in Embodiment 1 of this invention. It is a figure showing the flow of the air inside the internal combustion engine in execution of scavenging control. It is a figure showing the relationship between the intake air amount coefficient A and the engine speed Ne. It is a figure showing the various operation examples when the engine speed Ne falls below the idle speed Ne_idle.

  Embodiments of the present invention will be described below with reference to the drawings. However, in the embodiment shown below, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the reference However, the present invention is not limited to these numbers. Further, the structures, steps, and the like described in the embodiments below are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

Embodiment 1 FIG.
1. System Configuration of First Embodiment FIG. 1 is a diagram for schematically explaining the system configuration of a vehicle 10 according to a first embodiment of the present invention. A vehicle 10 shown in FIG. 1 includes a spark ignition type internal combustion engine 12 as a power source. As an example, the internal combustion engine 12 is an in-line four-cylinder engine.

  The internal combustion engine 12 includes a fuel injection valve 14, an ignition device 16, and a throttle valve 18. The fuel injection valve 14 is disposed in each cylinder 56 (see FIG. 3), and directly injects fuel into the cylinder 56. The ignition device 16 ignites the air-fuel mixture in the cylinder 56 using an ignition plug disposed in each cylinder 56. The throttle valve 18 is disposed in the intake passage 54 (see FIG. 2) of the internal combustion engine 12, and controls the amount of air taken into each cylinder 56 (intake air amount).

  The vehicle 10 includes a starter motor 20 as an electric motor that can rotationally drive a crankshaft (not shown) of the internal combustion engine 12. The vehicle 10 also includes a transmission 22 and a clutch 24. The transmission 22 is a manual transmission. The clutch 24 is disposed between the internal combustion engine 12 and the transmission 22. When the clutch 24 is in the engaged state, the torque of the internal combustion engine 12 is transmitted to the transmission 22 via the clutch 24 and further transmitted to the drive wheels 28 via the differential gear 26.

  The system of this embodiment includes an electronic control unit (ECU) 30. The ECU 30 includes at least an input / output interface, a memory, and an arithmetic processing unit (CPU), and is mounted on the vehicle 10 in order to control the operation of the internal combustion engine 12. Various sensors for acquiring the operating state of the vehicle 10 including the operating state of the internal combustion engine 12 are electrically connected to the ECU 30. The ECU 30 is electrically connected to various actuators for controlling the operation of the internal combustion engine 12 such as the fuel injection valve 14, the ignition device 16, the throttle valve 18, and the starter motor 20 described above. In the memory, various control programs and maps for controlling the operation of the internal combustion engine 12 are stored. The CPU reads the control program from the memory and executes it, and generates operation signals for various actuators based on the acquired sensor signals.

  The various sensors connected to the ECU 30 include a crank angle sensor 32, an air flow sensor 34, an intake pressure sensor 36, and a throttle opening sensor 38. The crank angle sensor 32 is used for detecting the engine rotation speed. The air flow sensor 34 detects the intake air amount. The intake pressure sensor 36 detects the intake pressure in the intake passage 54 on the downstream side of the throttle valve 18. The throttle opening sensor 38 detects the opening (throttle opening) of the throttle valve 18.

  The various sensors include a brake switch 40, an accelerator opening sensor 42, a clutch switch 44, and a neutral switch (Nsw) 46. The brake switch 40 detects whether or not the brake pedal 48 is depressed. The accelerator opening sensor 42 detects the amount of depression of the accelerator pedal 50 (accelerator opening). The clutch switch 44 detects whether the clutch pedal 52 is depressed. The neutral switch 46 detects whether or not the transmission 22 is in a neutral state.

2. Control of Embodiment 1 2-1. Engine start control The ECU 30 is configured to alternatively execute starter start control and ignition start control as engine start control for starting the internal combustion engine 12.

2-1-1. Starter start control The starter start control is basically used to start the internal combustion engine 12 in a cold state. According to the starter start control, when a predetermined engine stop request is issued, the internal combustion engine 12 can be started by performing fuel injection and ignition while rotating the crankshaft using the starter motor 20.

2-1-2. Ignition start control The control executed by the ECU 30 includes S & S (Stop & Start) control. In the S & S control, when a predetermined engine automatic stop condition is satisfied while the vehicle 10 is temporarily stopped, the operation of the internal combustion engine 12 is automatically stopped by stopping the fuel supply, and then a predetermined engine restart condition is satisfied. Sometimes the internal combustion engine 12 is restarted.

  The ignition start control is superior to the starter start control in terms of vibration noise when starting the engine. Further, in the ignition start control, the amount of fuel required for start-up is increased compared to the starter start control, but the work efficiency is improved compared to the starter start control using an electric motor such as the starter motor 20. For this reason, fuel consumption can be improved by using the ignition start control.

  The ignition start control is basically used when the internal combustion engine 12 is restarted during the execution of the above-described S & S control. According to the ignition start control, the internal combustion engine 12 in a warm state is started by starting fuel injection and ignition from a cylinder in an expansion stroke (hereinafter referred to as an “expansion stroke cylinder”) while the engine is stopped. Can do.

2-2. Control when engine stall occurs (engine stall control)
During operation of the vehicle 10, an engine stall may occur without being based on either a request from the driver or an engine automatic stop request by S & S control. As an example of the situation of occurrence of an engine stall here, when the clutch 24 is not released during sudden deceleration due to a mistake in shifting operation, or when the clutch 24 is suddenly braked, Applicable when not done.

  Here, the following scavenging control is known in order to ensure good engine startability during ignition start control. That is, according to the scavenging control, the throttle valve is opened after the fuel injection to each cylinder is stopped. As a result, the amount of fresh air passing through each cylinder can be increased during the engine stop process from the start of fuel injection stop to the stop of crankshaft rotation. Thereby, scavenging of the residual gas in each cylinder can be performed. For this reason, when the ignition start control is subsequently performed, the ignition start can be performed in a state in which a good amount of oxygen is secured in the expansion stroke cylinder. In the engine stop process, the throttle valve is opened at an arbitrary opening, thereby obtaining a scavenging effect by increasing the amount of fresh air. For this reason, as the throttle opening when it is opened by scavenging control, a fully open opening or an arbitrary intermediate opening can be used.

  In a general vehicle system, the occurrence of the engine stall described above is not predicted. For this reason, when the above-described scavenging control is to be performed when the engine is stopped on the premise of such a vehicle system, if an unexpected engine stall occurs in the vehicle system, the scavenging control is not performed and the internal combustion engine is stopped. . As a result, when the ignition start control is subsequently performed, depending on the situation inside the expansion stroke cylinder, the amount of unburned gas is large and the amount of oxygen is small, so it may be difficult to establish the ignition start. There is sex. As a result, it is necessary to use the starter start control instead of the ignition start control, and there is concern about an increase in vibration noise and deterioration in fuel consumption at the start.

  Therefore, in the present embodiment, when engine stoppage due to engine stall is predicted, fuel injection to each cylinder 56 is stopped, and scavenging control by opening the throttle valve 18 is started. When the scavenging control has been completed in the engine stop process from the start of fuel injection stop prediction to the completion of the engine stop accompanying the engine stop prediction, the ignition start control is selected when the internal combustion engine 12 is restarted. The On the other hand, when the scavenging control is not completed in the engine stop process accompanying the engine stop prediction, the starter start control is selected when the internal combustion engine 12 is restarted.

2-3. FIG. 2 is a flowchart showing a procedure of a process related to the control at the time of engine stop executed by the ECU 30 in the first embodiment of the present invention. Note that the processing of this flowchart is started during the operation of the internal combustion engine 12 and is repeatedly executed. The control when the engine is stopped as described below is based on the assumption that the transmission 22 is not in the neutral state.

Prior to the description of the flowchart shown in FIG. 2, the relationship among the three engine rotational speed values Ne_idle, Ne_lolimit, and Ne_idlelimit that appear in this flowchart will be described. Ne_idle is a predetermined idle rotation speed. Ne_lolimit is a lower limit value of the scavenging control start rotational speed (hereinafter, referred to as “scavenging start lower limit value”) in which a sufficient scavenging effect can be expected by the scavenging control (that is, the scavenging control can be surely completed). For this reason, there is a possibility that scavenging cannot be sufficiently performed when the scavenging control is started under the engine rotation speed Ne that is less than the scavenging start lower limit value Ne_lolimit. Ne_idlelimit is a lower limit value of the engine rotation speed (hereinafter referred to as “idle maintenance lower limit value”) at which the internal combustion engine 12 can return autonomously and maintain idling operation. As shown below, the scavenging start lower limit value Ne_lolimit is lower than the idle rotation speed Ne_idle, and the idle maintenance lower limit value Ne_idlelimit is lower than the scavenging start lower limit value Ne_lolimit.
Ne_idlelimit <Ne_lolimit <Ne_idle

  In the flowchart shown in FIG. 2, first, it is determined whether or not the engine rotational speed Ne detected by the crank angle sensor 32 is lower than the idle rotational speed Ne_idle (step S100). As a result, when the engine rotational speed Ne is equal to or higher than the idle rotational speed Ne_idle, the process of the current flowchart is ended.

  For example, when the vehicle 10 is suddenly decelerated due to an operation mistake of the transmission 22 or sudden braking, the engine rotational speed Ne may be lower than the idle rotational speed Ne_idle. In such a case, the determination in step S100 is established. In this case, it is then determined whether or not the clutch 24 is not released based on the signal from the clutch switch 44 (step S102).

  If it is determined in step S102 that the clutch 24 has not been released, there is a concern that engine stall will occur. In this case, it is determined whether or not the engine rotational speed Ne is lower than the scavenging start lower limit value Ne_lolimit (step S104). While this determination is not established, the determination in step S104 is repeatedly executed.

  On the other hand, if the determination in step S104 is established, that is, if the engine rotational speed Ne falls below the scavenging start lower limit value Ne_lolimit, the engine stop due to the engine stall is predicted, so the engine determination flag is turned ON ( Step S106).

  If it is determined in step S102 that the clutch 24 has been released, it is then determined whether the engine speed Ne is higher than the idle maintenance lower limit Ne_idlelimit (step S108).

  If the determination in step S108 is not satisfied (Ne ≦ Ne_idlelimit), then starter start control is selected to restart the internal combustion engine 12 (step S110). More specifically, in this case, since the engine speed Ne is below the scavenging start lower limit Ne_lolimit that is higher than the idle maintenance lower limit Ne_idlelimit, the scavenging control cannot be completed even if the scavenging control is performed. Therefore, a sufficient scavenging effect cannot be expected. For this reason, starter start control is selected.

  On the other hand, if the determination in step S108 is true (Ne> Ne_idlelimit), that is, if the clutch 24 is released under an engine rotation speed Ne higher than the idle maintenance lower limit Ne_idlelimit, the engine rotation speed Ne is autonomously restored. Can be determined to be possible. Therefore, in this case, it is determined whether or not the engine rotational speed Ne is equal to or higher than the scavenging start lower limit value Ne_lolimit (step S112).

  If it is determined in step S112 that the engine rotational speed Ne is equal to or higher than the scavenging start lower limit value Ne_lolimit, engine stall avoidance control for avoiding engine stall is executed (step S114). As an example of the engine stall avoidance control, idle speed control control (ISC control) that controls the throttle opening according to the engine load is used in order to make the engine rotational speed Ne approach the idle rotational speed Ne_idle. it can.

  If it is determined in step S112 that the engine rotational speed Ne is lower than the scavenging start lower limit value Ne_lolimit, the engine rotational speed Ne can be restored autonomously, but the scavenging start lower limit value that allows sufficient scavenging. The engine speed Ne is lower than Ne_lolimit. In this embodiment, in this case, the process proceeds to step S106.

  If the engine stall determination flag is turned on in step S106, then, process steps S116 to S124 relating to engine stall control (control when engine stall occurs) are executed.

  First, fuel injection stop processing (F / C) and scavenging control (opening of the throttle valve 18) are executed (step S116). The throttle opening at the time of scavenging control can maximize the amount of fresh air passing through each cylinder 56. Therefore, the fully open opening is desirable, but it may be any intermediate opening as described above. In step S116, an intake air amount integration process for a scavenging completion determination process described later is started.

  After the process of step S116, it is determined using the crank angle sensor 32 whether or not the engine stop (crankshaft rotation stop) has been completed (step S118). This determination is repeatedly performed until it is satisfied. And while this determination is repeatedly performed, scavenging control is continued, and the intake air amount integration process is continued. If this determination is established, it is then determined whether scavenging has been completed during the engine stop process (step S120).

  The scavenging completion determination process in step S120 is the integrated suction in the engine stop process from the start of scavenging control by the process in step S116 (same as the start of stopping fuel injection in this example) to the completion of engine stop (step S118; Yes). It is executed based on whether or not the air amount is larger than the threshold Sum_Vair0. The threshold Sum_Vair0 is an integrated value of the intake air amount necessary for completing scavenging, and is determined in advance according to the engine specifications. Hereinafter, an example of the scavenging completion determination process using the integrated intake air amount will be described more specifically with reference to FIGS. 3 and 4.

  FIG. 3 is a diagram showing the flow of air inside the internal combustion engine 12 during the execution of the scavenging control. FIG. 4 is a graph showing the relationship between the intake air amount coefficient A and the engine rotational speed Ne. As shown in FIG. 3, the air (fresh air) taken into the intake passage 54 passes through the inside of the cylinder 56 and is then discharged into the exhaust passage 58.

  In the scavenging completion determination process in step S120, the integrated intake air amount during execution of the scavenging control is calculated using the following method. That is, the integrated intake air amount is integrated over time with a flow rate value obtained by multiplying the intake air amount (intake air flow rate) per unit time measured by the air flow sensor 34 by the intake air amount coefficient A. It is calculated by.

  More specifically, FIG. 4 shows the relationship between the engine speed Ne and the intake air amount coefficient A when the other conditions (intake air flow rate, intake pressure, etc.) other than the engine speed Ne are the same. . According to the relationship shown in FIG. 4, the intake air amount coefficient A increases as the engine speed Ne increases. Such a relationship is experimentally obtained in advance when designing the engine, and is stored in the ECU 30 as a map. According to such a map, the intake air amount coefficient A corresponding to the current engine speed Ne detected using the crank angle sensor 32 can be calculated.

  Here, as parameters affecting the integrated intake air amount during execution of the scavenging control, in addition to the engine speed Ne, the throttle opening, the opening characteristics of the intake valve 60 and the exhaust valve 62, and the intake pressure (throttle) Downstream pressure). The intake air amount coefficient A is desirably changed according to each of these parameters. Therefore, similarly to the relationship with the engine speed Ne, the relationship between each parameter and the intake air amount coefficient A is acquired and mapped in advance, and the sensor value and the suction value of each parameter are referenced with reference to such a map. An intake air amount coefficient A corresponding to the operating state of the exhaust valves 60 and 62 may be calculated on the actual machine.

  The scavenging completion determination process is not limited to the method using the integrated intake air amount as described above, and may be performed more simply using, for example, a method using the integrated engine rotation speed. More specifically, when using the accumulated engine speed, the accumulation of the engine speed Ne may be started in step S116. Whether or not scavenging has been completed can be determined based on whether or not the integrated engine rotation speed is greater than the threshold Sum_Ne0. The threshold Sum_Ne0 is an integrated value (specifically, about 5 or 6 revolutions (2, 3 cycles in each cylinder 56)) of the engine rotation speed Ne required for the completion of scavenging, and is previously determined according to the engine specifications. To be determined.

  If it is determined in step S120 that the cumulative intake air amount is larger than the threshold Sum_Vair0 and thus scavenging has been completed in the engine stop process, it is determined that the scavenging state is enabled to start by ignition start control after engine stall. The Therefore, in this case, ignition start control is selected for subsequent engine restart (step S122).

  On the other hand, when it is determined in step S120 that scavenging has not been completed in the engine stop process because the integrated intake air amount is equal to or less than the threshold Sum_Vair0, the scavenging state is incapable of starting by ignition start control after engine stall. It is judged. Therefore, in this case, starter start control is selected for subsequent engine restart (step S124).

  After the control used at the time of engine restart is selected by the process of step S122 or S124, the engine stall determination flag is turned OFF (step S126). Thereby, engine stall control is complete | finished.

2-4. Operational Example FIG. 5 is a diagram illustrating various operational examples when the engine rotational speed Ne is reduced to be lower than the idle rotational speed Ne_idle. FIG. 5 shows five operation examples of operation examples 1 to 5.

  First, the operation example 1 is an operation example in a situation where a sudden deceleration due to an operation mistake of the transmission 22 occurs and the clutch 24 is not operated until an engine stall occurs. Operation example 1 corresponds to an example in which the determinations in steps S102 and S104 are satisfied and the determination in step S120 is not satisfied in the flowchart shown in FIG.

  In the first operation example, when the engine rotational speed Ne falls below the scavenging start lower limit value Ne_lolimit (in other words, the engine stall determination rotational speed), the engine stall determination flag is turned ON, and the scavenging control is executed. The operation example 1 corresponds to an example in which the integrated intake air amount in the engine stop process is smaller than the threshold Sum_Vair0. Therefore, in the operation example 1, the execution of the scavenging control is not completed and the engine stop state is reached. As a result, the starter start control is executed instead of the ignition start control for the subsequent restart.

  The operation example 2 is an operation example in a situation where sudden deceleration due to sudden braking occurs and the operation of the clutch 24 is not performed until an engine stall occurs. The operation example 2 corresponds to an example in which the determinations in steps S102 and S104 are established and the determination in step S120 is also established in the flowchart shown in FIG.

  In the operation example 2, as in the operation example 1, the scavenging control is executed when the engine rotational speed Ne falls below the scavenging start lower limit value Ne_lolimit (engine determination rotational speed). The operation example 2 corresponds to an example in which the integrated intake air amount in the engine stop process is larger than the threshold Sum_Vair0. Therefore, in the operation example 2, the engine stop state is reached when the scavenging control is completed. As a result, the ignition start control is executed for the subsequent restart.

  The operation example 3 corresponds to an example in which the release operation of the clutch 24 is performed after the engine stall determination flag is turned on and the scavenging control is started in a case where a relatively gentle brake is performed. In this case, engine stall control is already started before it is detected that the clutch 24 has been released. For this reason, in the operation example 3, the engine stall control is continuously performed.

  Further, as shown in FIG. 5, the scavenging start lower limit value Ne_lolimit is higher than the idle maintenance lower limit value Ne_idlelimit. For this reason, as in the case of the operation example 3, when the engine 24 is disengaged, the engine rotation speed Ne is within the rotation speed range from the scavenging start lower limit value Ne_lolimit to the idle maintenance lower limit value Ne_idlelimit. The execution of the engine stall control is prioritized over the automatic return (autonomous return) of the engine rotation speed Ne by the ISC control.

  The operation example 4 is different from the operation example 3 in the case where a relatively gentle brake is performed, and the operation for releasing the clutch 24 is performed before the engine rotation speed Ne falls below the scavenging start lower limit value Ne_lolimit (engine determination rotation speed). Corresponds to an example in which In this operation example 4, ISC control is executed to avoid engine stall, and as a result, the engine rotation speed Ne autonomously returns to the vicinity of the idle rotation speed Ne_idle.

  The operation example 5 corresponds to an example in which the engine rotation speed Ne drops suddenly due to sudden braking. More specifically, in the operation example 5, after the engine speed Ne becomes less than the idle speed Ne_idle, it quickly decreases to the idle maintenance lower limit value Ne_idlelimit or less. As described above, the operation example 5 corresponds to an example in which the determination in step S108 is not established immediately after the determination in step S100 is established in the flowchart shown in FIG. Therefore, in this case, since the scavenging by the scavenging control is impossible, the starter start control is selected.

  Further, the reason why the control content is changed depending on whether or not the clutch 24 is disengaged will be described in connection with operation examples 1 to 4. In operation examples 1 and 2 in which the clutch 24 is not released, the internal combustion engine 12 stops while being dragged by the transmission 22 while the internal combustion engine 12 and the transmission 22 are connected. On the other hand, in the operation examples 3 and 4 in which the clutch 24 is released, the internal combustion engine 12 stops due to its own friction. Due to this, the first and second operation examples 1 and 3 and 4 differ in the speed at which the engine speed Ne drops. More specifically, the first and second operation examples 1 and 2 in which the clutch 24 is not disengaged have the engine speed Ne dropping more rapidly than the third and fourth operation examples. Therefore, the operation examples 1 and 2 make the internal combustion engine 12 stall more easily than the operation examples 3 and 4. Here, it can be determined that the operation of the driver depressing the clutch pedal 52 is intended to avoid engine stall. Therefore, in the engine stall control of the present embodiment, in the situation as in the operation example 4, the engine stall is avoided by the ISC control. By including such processing, it is possible to perform ignition start control by specifying a case involving sufficient scavenging as described later while avoiding the occurrence of engine stall as much as possible.

2-5. Effect According to the process according to the flowchart shown in FIG. 2 described above, the presence or absence of engine stop due to engine stall is predicted. As a result, when the engine stop is predicted, engine stall control is executed. That is, fuel injection stop processing (F / C) and scavenging control are executed. After completion of the engine stop, a scavenging completion determination process (determination as to whether scavenging has been completed during the engine stop process) is executed. As a result, when the scavenging control has been completed in the engine stop process, the ignition start control is selected when the internal combustion engine 12 is restarted. On the other hand, when the scavenging control is not completed during the engine stop process, the starter start control is selected when the internal combustion engine 12 is restarted.

  According to the engine stall control described above, the ignition start control can be performed after appropriately determining the situation in which the ignition start control can be performed even after the engine stall.

  Further, according to the engine stall control, the following effects can be obtained. That is, according to the engine stall control, when the engine rotational speed Ne is reduced to less than the idle rotational speed Ne_idle, the use frequency of the ignition start control can be increased as described above. Therefore, the engine stall is avoided using the ISC control. If so, it is possible to suppress the occurrence of vibrations generated in the internal combustion engine 12 in the extremely low rotational speed region. In addition, even when the engine is restarted after the engine stalls, the drivability of the internal combustion engine 12 can be improved by performing the ignition start control that enables a quiet start compared to the starter start control. Furthermore, according to the ignition start control, energy consumed for assistance by an external mechanism such as the starter motor 20 becomes unnecessary, so that fuel efficiency can be improved.

  In addition, according to the engine stall control described above, the idling maintenance lower limit value Ne_idlelimit (in other words, the engine speed at which engine stall normally occurs) at which the internal combustion engine 12 returns autonomously and can maintain idling operation is higher. When the scavenging start lower limit value Ne_lolimit is not reached, stop of fuel injection and scavenging control are performed. As a result, the engine stall occurs at a higher engine rotational speed Ne than when the engine stall occurs without such engine stall control. However, according to the present embodiment, it is possible to restart using the ignition start control immediately after the engine stalls.

  By the way, in Embodiment 1 mentioned above, scavenging control is continuously performed in the whole engine stop process from the stop start of the fuel injection accompanying an engine stop prediction to the completion of an engine stop. However, the execution period of the scavenging control is not necessarily limited to the entire period of the engine stop process as long as the effect of the scavenging by the scavenging control can be secured. Good. In addition, the scavenging control does not necessarily need to be started immediately after the start of fuel injection stop, and does not necessarily have to be continued until the engine stop is completed.

  Further, in the first embodiment described above, when the engine stop due to the engine stall is predicted, the fuel injection stop and the scavenging control are executed, and the scavenging is completed after the engine stop is completed. As the control used for restarting, ignition start control or starter start control is selected. However, such control is not limited to that executed in accordance with the prediction of engine stop caused by engine stall, and is executed, for example, when engine stop is predicted triggered by an engine automatic stop request by S & S control. May be.

DESCRIPTION OF SYMBOLS 10 Vehicle 12 Internal combustion engine 14 Fuel injection valve 16 Ignition device 18 Throttle valve 20 Starter motor 22 Transmission 24 Clutch 28 Drive wheel 30 Electronic control unit (ECU)
32 Crank angle sensor 34 Air flow sensor 36 Intake pressure sensor 38 Throttle opening sensor 40 Brake switch 42 Accelerator opening sensor 44 Clutch switch 46 Neutral switch

Claims (1)

An internal combustion engine comprising a fuel injection valve for directly injecting fuel into the cylinder, an ignition device for igniting the air-fuel mixture, and a throttle valve provided in the intake passage;
An electric motor capable of rotationally driving the crankshaft of the internal combustion engine;
And a control device for controlling the internal combustion engine.
The engine start control performed by the control device to start the internal combustion engine is:
Starter start control for starting the internal combustion engine by performing fuel injection and ignition while rotationally driving the crankshaft using the electric motor;
Ignition start control for starting fuel injection and ignition from an expansion stroke cylinder in an expansion stroke while the engine is stopped to start the internal combustion engine;
Including
When the engine stop is predicted, the control device stops the fuel injection to the cylinder and starts the scavenging control for scavenging the cylinder by opening the throttle valve,
When the scavenging control has been completed in the engine stop process from the start of fuel injection stop to the completion of engine stop accompanying the engine stop prediction, the control device performs the ignition when restarting the internal combustion engine. The starter control is selected, and when the scavenging control is not completed in the engine stop process, the starter start control is selected when the internal combustion engine is restarted. Control device.

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