JP6555176B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, a vehicle capable of automatically stopping and restarting an internal combustion engine is known. For example, in Patent Document 1, when there is a restart request in the stop operation period from the fuel cut to the rotation stop of the internal combustion engine, the fuel injection and ignition to the cylinder in the expansion stroke are performed immediately before the stop of the internal combustion engine. It is disclosed.

JP 2005-155362 A

  By the way, in the ignition start which performs fuel injection and ignition to the cylinder in the expansion stroke, it is necessary to ensure sufficient fresh air in order to reliably ignite and burn the cylinder in the expansion stroke. If a necessary amount of fresh air is not secured in the cylinder in the expansion stroke that is the subject of the initial explosion at the start of ignition, there is a risk that the start stability at the start of ignition will be reduced.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an internal combustion engine that can reliably restart the internal combustion engine while ensuring start stability at the start of ignition. To do.

  The present invention is mounted on a vehicle capable of automatically stopping and restarting an internal combustion engine, and restarts the internal combustion engine by an ignition start for performing fuel injection and ignition to a cylinder in an expansion stroke after the internal combustion engine is automatically stopped. In the control device for an internal combustion engine, when the internal combustion engine is automatically stopped, the auxiliary machine is stopped after the fuel cut is started and before the rotation of the internal combustion engine is stopped, and the throttle opening or the intake valve opening is adjusted, After the internal combustion engine swings back, if the intake pipe pressure when the cylinder in the expansion stroke performing the first injection at the start of ignition passes through the intake stroke is less than a predetermined value, or the cylinder in the expansion stroke is one cycle before When the fuel cut is not executed, the ignition start is not executed, and the internal combustion engine is restarted using a starter.

  In the present invention, since the auxiliary machine is stopped when the internal combustion engine is automatically stopped, a decrease in the rotational speed of the internal combustion engine is suppressed, and the negative pressure in the intake pipe can be released with the throttle and the intake valve relatively open. it can. Thereby, since it becomes easy to ensure fresh air while suppressing vibrations when the internal combustion engine is stopped, starting stability at the start of ignition is ensured. Furthermore, when the fresh air necessary for the ignition start is not secured, the ignition start is not executed, and the internal combustion engine is restarted using the starter. Thereby, an internal combustion engine can be restarted reliably.

FIG. 1 is a schematic configuration diagram schematically illustrating a control device for an internal combustion engine according to an embodiment. FIG. 2 is a diagram for explaining a method of ensuring fresh air in the expansion stroke cylinder when the engine is swung back. FIG. 3 is a diagram for explaining a method of determining whether fresh air is secured in the expansion stroke cylinder when the engine is swung back. FIG. 4 is a diagram for explaining a method for determining whether the exhaust manifold of the expansion stroke cylinder is scavenged. FIG. 5 is a diagram for explaining a case where fuel injection is performed in the expansion stroke cylinder. FIG. 6 is a diagram for explaining a case where fuel injection is not performed in the expansion stroke cylinder. FIG. 7 is a flowchart showing air securing / scavenging promotion processing. FIG. 8 is a flowchart showing a start method selection process.

  Hereinafter, a control device for an internal combustion engine in an embodiment of the present invention will be described in detail with reference to the drawings.

[1. vehicle]
FIG. 1 is a schematic configuration diagram schematically showing a control device for an internal combustion engine in the embodiment. The vehicle Ve of the present embodiment includes an engine (ENG) 1 that is a power source, an automatic transmission (T / M) 2, an output shaft 3, a differential 4, an axle 5, and drive wheels 6. Yes. The power output from the engine 1 is transmitted from the crankshaft 1 a to the output shaft 3 via the automatic transmission 2, and is transmitted from the output shaft 3 to the axle 5 and the drive wheels 6 via the differential 4.

  The engine 1 is a four-cycle engine constituted by a known internal combustion engine, and is constituted by a direct injection type in which fuel is directly injected into each cylinder. The engine 1 is electrically controlled by a control device (ECU) 10 mounted on the vehicle Ve. Details of the control device 10 will be described later.

  The automatic transmission 2 is a known transmission that can automatically change the gear ratio, and is configured to be automatically set to a neutral state. Note that the vehicle Ve may include a torque converter that generates a torque amplification action by a fluid flow, and the engine 1 may be connected to the automatic transmission 2 via the torque converter so as to be able to transmit torque.

  The vehicle Ve is equipped with a starter (starter) 7 that starts the engine 1. The starting device 7 is constituted by an electric motor electrically connected to a battery (not shown), and is driven and controlled by the control device 10 when the engine is started.

  The vehicle Ve can automatically stop and restart the engine 1 under the control of the control device 10. Note that the power train of the vehicle Ve shown in FIG. 1 described above is an example. The vehicle on which engine 1 and control device 10 are mounted may be an FF vehicle or an FR vehicle.

[2. Control device]
The control device 10 is constituted by an electronic control device that controls fuel injection and ignition timing of the engine 1. The control device 10 performs various calculations using signals input from various sensors mounted on the vehicle Ve and data stored in the storage device, and outputs a command signal as a result to the engine 1. 1 is controlled.

  As shown in FIG. 1, a sensor output signal is input from the crank angle sensor 20 to the control device 10. The crank angle sensor 20 detects the rotation direction and crank angle of the engine 1 and outputs a signal thereof. Further, the control device 10 receives signals from various sensors (not shown) (for example, an accelerator opening sensor, a brake stroke sensor, a vehicle speed sensor, a throttle opening sensor, etc.).

  The control device 10 controls the fuel injection and ignition timing to the engine 1 according to the vehicle state, and automatically stops and restarts the engine 1. The control device 10 includes an automatic stop control unit as a control unit that automatically stops the engine 1 and a start control unit as a control unit that restarts the engine 1.

  For example, when it is determined that a predetermined stop condition is satisfied, the control device 10 performs engine stop control to automatically stop the engine 1. Examples of the stop condition include a case where the vehicle is temporarily stopped by waiting for a signal or the like, a case where the traveling vehicle is decelerating, or a case where the depression of the accelerator pedal is released while traveling at a certain high vehicle speed. The engine stop control includes fuel cut control (F / C control) for stopping fuel injection (supply) to the engine 1.

  The crank angle sensor 20 detects the crank angle and the rotation speed of the engine 1 until the rotation of the engine 1 stops and also after the rotation of the engine 1 stops. As a result, the control device 10 determines the crank angle and the engine rotation based on the signal input from the crank angle sensor 20 from the start of fuel cut until the engine 1 stops rotating and after the engine 1 stops rotating. Speed and can be detected.

  When it is determined that the restart condition is satisfied after the engine 1 is automatically stopped, the control device 10 executes engine start control to restart the engine 1. As a restart condition (start request), there is a charge request when it is detected that the accelerator pedal is depressed, when the brake pedal is released while the vehicle is stopped, or when the remaining battery capacity is reduced. Cases. Further, the control device 10 includes a determination unit that determines whether or not an input signal from various sensors including the crank angle sensor 20 is detected, and the determination unit determines whether or not a restart condition is satisfied. Can do.

  The engine start control includes two controls, ignition start control and starter start control. The ignition start control is control for performing ignition (fuel injection and ignition) on the cylinder in the expansion stroke and rotating the crankshaft 1a by the combustion energy. On the other hand, the starter start control is control for rotating the crankshaft 1 a by consuming the battery power and driving the starter 7. When executing the starter start control, the control device 10 outputs a starter signal to drive the starter 7.

  The control device 10 starts the engine 1 only when starting ignition according to the vehicle state, when starting the engine 1 using both ignition start and the starting device 7, and only when the starting device 7 starts the engine 1. Use properly when restarting. For example, when there is a start request until the engine 1 stops rotating, the engine 1 is used only by the ignition start in which ignition is performed simultaneously with the fuel injection to the cylinder in the expansion stroke, or the ignition start and the starter 7 are used in combination. 1 is restarted.

  In particular, when executing the ignition start control, the state of the cylinder in the expansion stroke to be ignited, that is, the piston position (crank angle) in the cylinder of the expansion stroke and securing of fresh air required at the start of ignition are ignitable ( This is important from the viewpoint of starting stability. Therefore, after the fuel injection is stopped (after the start of F / C), until the rotation of the engine 1 stops (during the engine stop process), the amount of air required for restart can be adjusted and secured. It is configured. Specifically, the vehicle Ve includes an air adjusting device (not shown) having a throttle, an intake valve, and the like that adjust the amount of intake air (fresh air) flowing into the engine 1 to adjust the air amount (intake air amount). Thus, the minimum air necessary for restarting is secured in the cylinder in the expansion stroke. Thereby, ignitability (starting stability) is ensured at the time of restart, and vibration deterioration when the engine is stopped can be suppressed.

[3-1. How to ensure freshness]
FIG. 2 is a diagram for explaining a method of ensuring fresh air in the expansion stroke cylinder when the engine is swung back. FIG. 2 illustrates four items of an F / C execution flag, a starter signal, a crank counter, and an engine speed.

  As shown in FIG. 2, when the engine 1 is automatically stopped, fuel cut control is started (F / C control start), and the F / C execution flag is switched from OFF to ON. After the start of the F / C control, the fuel injection in the expansion stroke is stopped from the top dead center (TDC) of the F / C start cylinder, and the engine speed is reduced. When the rotation of the crankshaft 1a is stopped, the crankshaft 1a rotates in the reverse direction during the swing-back period, and the piston position (crank angle) increases in the cylinder in the expansion stroke (the cylinder that is initially exploded when the ignition start is executed). Shaking back to the dead center occurs. When the swingback occurs, the state of the cylinder (expansion stroke cylinder) that is the target of ignition at the time of restart is not stable, and the ignitability becomes unstable at the start of ignition, which may reduce the restartability. Therefore, the control device 10 is configured to ensure fresh air in the cylinder in the expansion stroke at the time of swingback in order to improve restartability (ignitability).

  Specifically, as shown in FIG. 2, the control device 10 uses an air adjustment mechanism such as a throttle until the cylinder in the expansion stroke at the time of swingback passes through the intake stroke. It is configured to relieve pressure. Furthermore, by slowing down the engine rotation speed, it is possible to ensure a long period of time for removing the negative pressure in the intake pipe. Further, the control device 10 is configured to accurately determine whether fresh air is secured in the cylinder in the expansion stroke at the time of occurrence of swingback.

  FIG. 3 is a diagram for explaining a method of determining whether fresh air is secured in the expansion stroke cylinder when the engine is swung back. As shown in FIG. 3, when the first injection is performed on the cylinder in the expansion stroke after the occurrence of the swing back, the pressure of the intake pipe (intake pipe pressure) when the cylinder passes through the intake stroke is stored in the storage device. Based on the intake pipe pressure, it is determined whether or not injection into the expansion stroke cylinder is possible. If it is determined that injection cannot be performed, the control device 10 does not perform fuel injection to the cylinder in the expansion stroke, performs only starter start control, and restarts the engine 1 using the starter 7. Let

  Specifically, the control device 10 checks the intake pipe pressure during the intake stroke for the expansion stroke cylinder of the first injection cylinder. When the intake pipe pressure is greater than or equal to a predetermined value, the control device 10 starts fuel injection into the expansion stroke cylinder. On the other hand, when the intake pipe pressure is less than the predetermined value, the control device 10 stops the injection to the expansion stroke cylinder and starts the engine 1 using the start device 7.

[3-2. Judgment method of scavenging completed]
FIG. 4 is a diagram for explaining a method for determining whether the exhaust manifold (exhaust manifold) of the expansion stroke cylinder is scavenging. As shown in FIG. 4, when fuel is injected into the expansion stroke cylinder, if the exhaust valve (EX valve) is open, it is determined whether or not the exhaust manifold is scavenged. For example, when the engine 1 is a four-cylinder engine, the exhaust valve is temporarily opened when the swing back occurs. If the pressure in the cylinder in the expansion stroke is negative when the exhaust valve is opened, the combustion gas is sucked back into the cylinder from the exhaust manifold. That is, the combustion gas is sucked from the exhaust manifold while the exhaust valve is open. Then, when the piston returns to near the top dead center due to rocking back, fuel injection / ignition is executed. In this case, there is a risk of misfire if the exhaust manifold contains combustion gas.

  Therefore, the control device 10 executes the fuel injection to the expansion stroke cylinder and the fuel injection to the expansion stroke cylinder based on the determination result of whether or not the first injection cylinder at the start of ignition has been scavenged. The start control is executed separately from the case where the control is not executed.

  FIG. 5 is a diagram for explaining a case where fuel injection is performed in the expansion stroke cylinder. As shown in FIG. 5, when the first injection is made to the expansion stroke cylinder (No. 4) after the occurrence of the swing back, if the cylinder has been cut once (F / C) one cycle before the exhaust, Even when the valve opens, fresh air comes in by sucking back the exhaust manifold. One cycle before refers to a state before the crank rotation amount 720 degrees or more, and means, for example, the case where the expansion stroke cylinder (No. 4) at the time of the occurrence of swingback is before the previous expansion stroke. In the example shown in FIG. 5, the expansion stroke cylinder (No. 4) at the time of occurrence of swing back corresponds to the F / C start cylinder, and the fuel cut (F / C) occurs at the TDC (crank rotation amount 0) of the F / C start cylinder. Is running. Thereby, it is possible to determine whether or not fresh air is secured in the expansion stroke cylinder (No. 4) at the time of occurrence of swing back. In this case, since the ignitability is ensured because the cylinder of the first explosion target (first injection) has been scavenged, the control device 10 performs injection (first injection) to the expansion stroke and starts the engine by starting ignition. 1 is restarted. Note that “F / C” shown in FIG. 5 means execution of fuel cut, and represents that fuel injection is stopped in the compression stroke. In addition, “scavenging” indicating that scavenging is performed in the exhaust stroke is described in the cylinder that has been cut even once.

  FIG. 6 is a diagram for explaining a case where fuel injection is not performed in the expansion stroke cylinder. As shown in FIG. 6, when the first injection is made to the expansion stroke cylinder (No. 3) after the occurrence of the swing back, if the cylinder (No. 3) is not cut even once before the cycle, the exhaust valve When opened, combustion gas enters from the exhaust manifold (cannot be scavenged). In this case, since the first explosion target cylinder (No. 3) is not scavenged, the control device 10 restarts the engine 1 using the starter 7 without executing the expansion stroke injection (ignition start). When scavenging is not completed, combustion gas is sucked.

  In addition, the control device 10 performs control to alleviate the decrease in the engine rotation speed so that the securing of fresh air and the scavenging are promoted. Furthermore, the control device 10 selects execution of the ignition start control at the time of restart depending on whether the fresh air is secured and the scavenged state is reached.

[3-3. Securing air and promoting scavenging]
FIG. 7 is a flowchart showing air securing / scavenging promotion processing. The processing flow shown in FIG. 7 is executed by the control device 10 during execution of engine stop control.

  As shown in FIG. 7, the control device 10 determines whether or not the fuel is being cut during the engine stop control (intermittent stop control) (step S1). In step S1, it is determined whether or not fuel cut is started. When the fuel cut is in progress (step S1: Yes), the control device 10 determines whether or not the engine 1 has been stopped (step S2).

  If it is before the engine 1 stops rotating (step S2: Yes), the control device 10 outputs a throttle opening instruction so as to achieve an opening according to the engine speed (step S3), and issues an air conditioner cut request. (Step S4), an alternator power generation restriction request is made (Step S5). In order to secure the minimum necessary air at the time of restart, the throttle opening is controlled during the engine stop process by the process of step S3 and adjusted to the amount of air required at the time of restart. Thereby, vibration deterioration can be suppressed. The process of step S3 is a process for releasing the negative pressure in the intake pipe, and may be configured to adjust the intake air amount by outputting an intake valve opening instruction and adjusting the intake valve opening. Thereby, the negative pressure in the intake pipe can be released even when the throttle and the intake valve are not relatively open. In addition, in steps S4 to S5, the auxiliary machinery (air conditioner, alternator) is stopped to gently decrease the engine speed. This lengthens the period during which the negative pressure in the intake pipe is released. Moreover, the control apparatus 10 can perform step S4, S5 simultaneously with the start of fuel cut control.

  When the fuel cut is not in progress (step S1: No), or when the engine 1 has not stopped rotating (step S2: No), the control device 10 does not issue a throttle opening instruction (step S6) and issues an air conditioner cut request. (Step S7), no alternator power generation restriction request is made (Step S8). For example, if the determination in step S2 is negative, the engine 1 is after the rotation is stopped, and therefore, the reduction speed of the engine rotation speed cannot be reduced as described above, so that no auxiliary machine stop request is made. .

[3-4. Starting method selection process]
FIG. 8 is a flowchart showing a start method selection process. The processing flow shown in FIG. 8 is executed by the control device 10 when a start request is generated after the occurrence of engine swingback.

  As shown in FIG. 8, the control device 10 determines whether or not it is after the occurrence of swing back (step S <b> 11). If it is not after the occurrence of shakeback (step S11: No), this control routine ends.

  On the other hand, when it is after the occurrence of the swingback (step S11: Yes), the control device 10 specifies the cylinder in the expansion stroke (step S12). In step S12, the piston position (crank angle) is specified based on the signal input from the crank angle sensor 20, and the cylinder in the expansion stroke is specified. Then, the control device 10 determines whether or not the intake pipe pressure when the cylinder in the expansion stroke specified in step S12 passes through the intake stroke is greater than or equal to a predetermined value (step S13). The control device 10 stores the intake pipe pressure when passing through the intake stroke in the storage device, and reads the intake pipe pressure from the storage device in step S13. The predetermined value used in step S13 is a predetermined value.

  If the intake pipe pressure when passing through the intake stroke is greater than or equal to a predetermined value (step S13: Yes), the control device 10 swings from the top dead center of the cylinder that started the fuel cut (TDC of the F / C start cylinder). It is determined whether or not the crank rotation amount until the return occurs is 900 degrees or more (step S14). In step S14, it is determined whether or not the first explosion target cylinder has been scavenged, as in the example shown in FIG. When the engine 1 is a four-cylinder engine, when the engine 1 is rotating more than 720 deg from the top dead center (TDC of the F / C start cylinder) where the fuel cut is started to the occurrence of the swingback, at least 1 expansion stroke cylinder is injected. It can be determined that the fuel cut (F / C) is executed before the cycle. Therefore, the exhaust manifold is scavenged with fresh air, and fresh air can be secured even if the gas (gas) is sucked back into the cylinder in the expansion stroke.

  When the crank rotation amount from the top dead center (TDC of the F / C start cylinder) starting the fuel cut to the occurrence of the swing back is 900 degrees or more (step S14: Yes), the control device 10 sends the expansion stroke cylinder to the expansion stroke cylinder. The fuel injection execution is selected (step S15). In step S15, since the expansion stroke cylinder (the cylinder targeted for the first explosion at the start of ignition) has been scavenged, the ignition start control is selected as the start control.

  Further, when the intake pipe pressure when passing through the intake stroke is not equal to or higher than a predetermined value (step S13: No), or from the top dead center of the cylinder that has started fuel cut (TDC of the F / C start cylinder) to the occurrence of swing back If the crank rotation amount is not 900 deg or more (step S14: No), the control device 10 selects engine start by the starter 7 (step S16). In step S16, as shown in FIG. 6 described above, since the expansion stroke cylinder (the cylinder targeted for the initial explosion at the start of ignition) cannot be scavenged, the fresh air necessary for restart is not secured. The ignition start is not executed, and the starter start control is selected as the start control. As described above, when a negative determination is made in step S13 or a negative determination is made in step S14, the engine is started using only the starter 7 without performing fuel injection to the expansion stroke cylinder. Switch.

  As described above, according to the control device 10, it is possible to accurately determine whether or not the fuel can be started by injecting fuel into the expansion stroke cylinder, and start stability at the start of ignition is ensured. As a result, it is possible to realize a restart with less discomfort and discomfort for the driver. Further, in order to ensure the starting stability at the start of ignition, it is necessary to put a necessary amount of fresh air into the cylinder targeted for the first explosion during the engine stop process. In this case, if the electronic throttle is opened, fresh air enters, but there is a contradiction in which the vibration when the rotation stops is increased. On the other hand, according to the control device 10, it is possible to achieve both introduction of fresh air and suppression of vibration at the time of stop. Furthermore, when it is determined that the required amount of fresh air is not secured in the cylinder targeted for the first explosion, the engine 1 is restarted using the starter 7 without performing the ignition start. Thereby, the engine 1 can be restarted reliably.

1 Engine (ENG)
7 Starter (Starter)
10 Control unit (ECU)
20 Crank angle sensor

Claims (1)

Control of an internal combustion engine mounted on a vehicle capable of automatically stopping and restarting the internal combustion engine and restarting the internal combustion engine by an ignition start for performing fuel injection and ignition to a cylinder in an expansion stroke after the internal combustion engine is automatically stopped In the device
When automatically stopping the internal combustion engine, after starting the fuel cut and before stopping the rotation of the internal combustion engine, stop the auxiliary machine, adjust the throttle opening or intake valve opening,
If the internal combustion engine of the swing-back is determined to have occurred, and the intake pipe pressure when the cylinder of the expansion stroke has passed the intake stroke immediately before stopping of the plan to the first injection during the ignition start is a predetermined value In the case of the following, or when it is determined that the internal combustion engine has been shaken back, and the cylinder in the expansion stroke scheduled to perform the first injection at the start of ignition, the fuel still remains at the time before one cycle. If it was a state that is not running the cut does not run the ignition starter control device for an internal combustion engine, characterized in that for restarting the internal combustion engine using a starting device.

Images