Control method of internal combustion engine and control device of internal combustion engine

Abstract

If the automatic stop condition is satisfied, fuel injection is stopped to automatically stop the internal combustion engine (1). In a case where a restart request is present during a process of reducing the engine rotation speed based on automatic stop, if the engine rotation speed is greater than or equal to a recoverable combustion rotation speed threshold (R1) that can be restarted by fuel injection alone, the internal combustion engine (1) is started by recovery by fuel injection, and if the engine rotation speed is less than the recoverable combustion rotation speed threshold (R1), the internal combustion engine (1) is started by rotating the engine with the starter motor (2). With respect to the internal combustion engine (1), in a case where a restart request is present in a state where the brake is on, a start by recovery based on fuel injection is not performed, and the engine is started by rotating the engine with the starter motor (2).

Description

TECHNICAL FIELD

[0001] The present application relates to a control method of an internal combustion engine and a control apparatus of an internal combustion engine. BACKGROUND

[0002] An idle stop control of an internal combustion engine is known in which, if a prescribed automatic stop condition is satisfied in an idle operation, the internal combustion engine is automatically stopped, and if a prescribed automatic restart condition is satisfied in the automatic stop, the internal combustion engine is automatically restarted.

[0003] For example, in Patent Literature 1, if an automatic stop request is generated in an operation of the internal combustion engine, fuel injection is stopped. In Patent Literature 1, if a restart request of the internal combustion engine is generated in the fuel injection stop based on the automatic stop request, if the internal combustion engine rotational speed at this time is in a rotational speed region in which the internal combustion engine can be restarted by fuel injection alone (greater than or equal to a lower limit value of a starterless restartable rotational speed), the internal combustion engine is restarted by fuel injection alone, and if the internal combustion engine rotational speed at this time is outside the rotational speed region in which the internal combustion engine can be restarted by fuel injection alone (less than the lower limit value of the starterless restartable rotational speed), the internal combustion engine is restarted by the starter that rotationally drives the crankshaft.

[0004] The lower limit value of the internal combustion engine rotational speed in which the internal combustion engine can be restarted by fuel injection alone (the lower limit value of the starterless restartable rotational speed) is set in accordance with the deceleration of the internal combustion engine. However, in the case where the driver depresses the brake pedal, the deceleration of the internal combustion engine varies in accordance with the size of the depression of the brake pedal (depression amount), and it is difficult to prescribe the lower limit value of the internal combustion engine rotational speed in which combustion start can be achieved. If the lower limit value of the internal combustion engine rotational speed in which combustion start can be achieved is set assuming a situation in which the deceleration of the internal combustion engine based on the emergency brake is large, the region in which combustion start can be achieved is limited in the case where the deceleration of the internal combustion engine is normal (a situation other than emergency braking).

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2010-223006 SUMMARY

[0006] With the internal combustion engine of the present application, in the case where a restart request of the internal combustion engine is present during a process of reducing the internal combustion engine rotational speed achieved based on automatic stop of the internal combustion engine, if the internal combustion engine rotational speed is greater than or equal to a prescribed rotational speed threshold in which the internal combustion engine can be restarted by fuel injection alone, the internal combustion engine is started by the resumption of fuel injection, and if the internal combustion engine rotational speed of the internal combustion engine is lower than the above-described rotational speed threshold, the internal combustion engine is started by rotation of the internal combustion engine by an electric motor. Also, in the case where a restart request is present in a state where the brake is on during a process of reducing the internal combustion engine rotational speed of the internal combustion engine achieved based on automatic stop, the internal combustion engine is started by rotation of the internal combustion engine by the above-described electric motor.

[0007] Thus, without considering the increase in the deceleration of the internal combustion engine accompanying the brake operation of the driver, the rotational speed threshold of the rotational speed of the internal combustion engine that can be restarted only by fuel injection is set. That is, in the case where there is a restart request in a state where the brake is not depressed, the region in which the internal combustion engine is restarted only by fuel injection can be expanded. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a schematic explanatory diagram that schematically represents the system structure of the internal combustion engine to which the present application is applied.

[0009] Figure 2 is a timing chart that represents one example of the situation when the automatically stopped internal combustion engine is restarted.

[0010] Figure 3 is a timing chart that represents one example of the situation when the automatically stopped internal combustion engine is restarted.

[0011] Figure 4 is a timing chart that represents one example of the situation when the automatically stopped internal combustion engine is restarted.

[0012] Figure 5 is a timing chart that represents one example of the situation when the automatically stopped internal combustion engine is restarted.

[0013] Figure 6 is a flowchart that represents the control flow of the internal combustion engine to which the present application is applied. DETAILED DESCRIPTION

[0014] Hereinafter, one embodiment of the present application will be explained in detail based on the drawings. Figure 1 is a schematic explanatory diagram that schematically represents the system structure of the internal combustion engine 1 to which the present application is applied.

[0015] The internal combustion engine 1 is, for example, a multi-cylinder spark-ignition gasoline internal combustion engine, and is mounted as a drive source on a vehicle such as an automobile. In addition, the internal combustion engine 1 can also be a diesel internal combustion engine.

[0016] The internal combustion engine 1 has a fuel injection valve (not shown). The fuel injection amount of the fuel injection valve, the fuel injection timing of the fuel injection valve, the pressure of the fuel supplied to the fuel injection valve, and the like are controlled to be optimum by the control unit 21 described later.

[0017] In addition, the internal combustion engine 1 has a starting motor 2 that is an electric motor. The starting motor 2 rotates the crankshaft (not shown) of the internal combustion engine 1 in a stopped state to start (crank start) the internal combustion engine 1. The starting motor 2 is controlled by the control unit 21 described later.

[0018] The driving force of the internal combustion engine 1 is transmitted to the CVT (Continuously Variable Transmission) 5 as a transmission via the torque converter 3 and the clutch 4, and the driving force transmitted to the CVT 5 is transmitted to the drive wheels 7 of the vehicle via the final gear 6.

[0019] That is, the internal combustion engine 1 transmits, for example, the rotation of a crankshaft not shown as the driving force to the drive wheels 7 of the vehicle.

[0020] The clutch 4 is located between the torque converter 3 and the CVT 5, and is engaged in a case where the driving torque from the internal combustion engine 1 can be transmitted to the drive wheels 7. That is, the clutch 4 is provided on a power transmission path that transmits the driving force of the internal combustion engine 1 to the drive wheels 7. Further, the engagement / disengagement of the clutch 4 is performed based on a control command from the control unit 21 described later. The clutch 4 is, for example, disengaged at the time of the coasting stop described later or the like.

[0021] The CVT 5 has a primary pulley 8 on the input side, a secondary pulley 9 on the output side, and a belt 10 that transmits the rotation of the primary pulley 8 to the secondary pulley 9.

[0022] The CVT 5 changes the width of the V-shaped grooves (not shown) of the primary pulley 8 and the secondary pulley 9, on which the belt 10 is wound, using hydraulic pressure, for example, and changes the contact radius of the belt 10 with the primary pulley 8 and the secondary pulley 9, so that the transmission ratio is changed steplessly.

[0023] Further, the CVT 5 is used as the transmission, but a stepped automatic transmission can be used instead of the CVT 5. In this case, the clutch 4 is configured using a plurality of friction engagement elements in the stepped automatic transmission.

[0024] The control unit 21 inputs detection signals of various sensors such as a crank angle sensor 22 that detects the crank angle of the crankshaft, an accelerator opening sensor 23 that detects the depression amount of an accelerator pedal (not shown), a vehicle speed sensor 24 that detects the vehicle speed, a brake sensor (brake switch) 25 that detects the depression amount of a brake pedal (not shown), and a catalyst temperature sensor 26 that detects the catalyst temperature of an exhaust purification catalyst (not shown) provided to an exhaust passage (not shown) of the internal combustion engine 1.

[0025] The control unit 21 calculates the requested load (engine load) of the internal combustion engine 1 using the detection value of the accelerator opening sensor 23.

[0026] In addition, the control unit 21 can detect the SOC (State Of Charge) that is the ratio of the charge remaining amount to the charge capacity of the vehicle-mounted battery (not shown). That is, the control unit 21 corresponds to a battery SOC detection unit.

[0027] The crank angle sensor 22 is capable of detecting the engine rotation speed (engine speed) of the internal combustion engine 1.

[0028] If a prescribed automatic stop condition is satisfied while the vehicle is running or while the vehicle is stopped, fuel supply is stopped to automatically stop the internal combustion engine 1. Further, if a prescribed automatic restart condition is satisfied in the automatic stop, the internal combustion engine 1 is automatically restarted. That is, the control unit 21 automatically stops the internal combustion engine 1 if the prescribed automatic stop condition is satisfied, and automatically restarts the internal combustion engine 1 if the prescribed automatic restart condition is satisfied.

[0029] The automatic stop condition of the internal combustion engine 1 is, for example, a state where the accelerator pedal is not depressed, a battery SOC of a vehicle-mounted battery is greater than a prescribed battery threshold value SOCth, a catalyst temperature of an exhaust purification catalyst is higher than a prescribed first catalyst temperature threshold value Tl, and the like.

[0030] The internal combustion engine 1 is automatically stopped when all of the above-described automatic stop conditions are satisfied. In other words, if all of the above-described automatic stop conditions are satisfied during the operation of the internal combustion engine 1, the control unit 21 automatically stops the internal combustion engine 1. That is, the control unit 21 corresponds to a first control portion that automatically stops the internal combustion engine 1 by stopping fuel injection if the prescribed automatic stop condition is satisfied.

[0031] The automatic restart condition of the internal combustion engine 1 is, for example, a state where the accelerator pedal is depressed, the battery SOC of the vehicle-mounted battery is less than or equal to the prescribed battery threshold value SOCth, the catalyst temperature of the exhaust purification catalyst is less than or equal to the prescribed first catalyst temperature threshold value Tl, and the like.

[0032] The internal combustion engine 1 is restarted if a restart request is present in the automatic stop. In other words, if any one of the above-described automatic restart conditions is satisfied in the automatic stop of the internal combustion engine 1, the control unit 21 restarts the internal combustion engine 1. For example, if the battery SOC of the vehicle-mounted battery is less than or equal to the battery threshold value SOCth as a prescribed value, the internal combustion engine 1 in the automatic stop is restarted.

[0033] As the automatic stop of the internal combustion engine 1, there are, for example, an idle stop, a coasting stop, and a cruise stop.

[0034] The idle stop is implemented, for example, when the above-described automatic stop condition is satisfied while the vehicle is temporarily stopped. In addition, the idle stop is released, for example, if any one of the above-described automatic restart conditions is satisfied.

[0035] The coasting stop is implemented in the vehicle running, for example, in a case where the above-described automatic stop condition is established. In addition, the coasting stop is released, for example, if any one of the above-described automatic restart conditions is established. Further, the coasting stop refers to, for example, automatic stop of the internal combustion engine 1 in deceleration in a state of low vehicle speed and with the brake pedal depressed.

[0036] The cruise stop is implemented in the vehicle running, for example, in a case where the above-described automatic stop condition is established. In addition, the cruise stop is released, for example, in a case where any one of the above-described automatic restart conditions is established. Further, the cruise stop refers to, for example, automatic stop of the internal combustion engine 1 in inertial running in a medium-high vehicle speed and without the brake pedal depressed.

[0037] In a case where there is a restart request of the internal combustion engine 1 in the process of reduction of the engine rotational speed of the internal combustion engine 1 achieved based on the automatic stop, if the engine rotational speed of the internal combustion engine 1 is greater than or equal to a prescribed recoverable combustion rotational speed threshold Rl (rotational speed threshold) at which the internal combustion engine 1 can be restarted by recovery of fuel injection alone, the control unit 21 starts the internal combustion engine 1 by recovery of fuel injection (combustion start), and if the engine rotational speed of the internal combustion engine 1 is lower than the recoverable combustion rotational speed threshold Rl, the internal combustion engine 1 is started by rotational driving of the crankshaft with the starting motor 2 (crank rotation). Also, regarding the control unit 21, in a case where there is a restart request in a state of brake-on with the brake pedal depressed, the start of the internal combustion engine 1 achieved based on recovery of fuel injection is not performed, and the internal combustion engine 1 is started by rotation with the starting motor 2 after the engine rotational speed becomes "0". That is, the control unit 21 corresponds to a 2nd control section.

[0038] The recoverable combustion rotational speed threshold Rl is set in consideration of a time difference between a timing at which a fuel injection start command of the internal combustion engine 1 in the automatic stop is issued and a timing at which fuel is ignited in the cylinder (initial combustion timing after recovery of fuel injection). That is, the recoverable combustion rotational speed threshold Rl is set so that the engine rotational speed at the initial combustion timing after recovery of fuel injection is not lower than a rotational speed at which the internal combustion engine 1 can be started by recovery of fuel injection, in consideration of a reduction amount of the engine rotational speed during a period from the timing at which the fuel injection start command is issued to the timing at which fuel is ignited in the cylinder. The recoverable combustion rotational speed threshold Rl is set in accordance with the deceleration of the internal combustion engine 1, for example, to a value of about 600 rpm.

[0039] In the case where the engine 1 in automatic stop is started by resumption of fuel injection (combustion start), there is a time difference between the timing at which the instruction to start fuel injection is issued and the timing at which the fuel in the cylinder is ignited (the timing of the first combustion after the resumption of fuel injection). That is, the timing at which the combustion in the engine 1 is started lags behind the timing at which the instruction to start fuel injection is issued. This is because the fuel is supplied to the cylinder that becomes the intake stroke after the instruction to start fuel injection is issued, and the fuel in the cylinder is ignited (burned) via the compression stroke.

[0040] Here, in the case where the engine 1 in automatic stop is started by resumption of fuel injection (combustion start), if the deceleration of the vehicle is increased by further depressing the brake pedal at the timing at which the instruction to start fuel injection is issued, the engine rotational speed can be greatly reduced before the ignition timing of the cylinder in which the fuel is first burned. If the deceleration of the vehicle is increased by further depressing the brake pedal, the engine rotational speed of the engine 1 is further reduced due to the deceleration of the vehicle, and the reduction speed of the engine rotational speed is increased.

[0041] Therefore, in the case of the engine 1, the engine rotational speed is greatly reduced before the ignition timing of the cylinder in which the fuel is first burned, the fuel cannot be burned, and the engine stalls (stall), and it can be difficult to start the engine 1 by resumption of fuel injection.

[0042] Therefore, in the case where the restart request is present in the state where the brake pedal is depressed, the start based on the resumption of fuel injection is not performed, and the engine 1 is started by the starting motor 2.

[0043] The restart request at the time when the brake pedal is depressed is not caused by the acceleration request of the driver. Therefore, in the case of the restart request at the time when the brake is on, the necessity to start the engine 1 early is low. Therefore, in the case where the restart request is present in the state where the brake pedal is depressed, the start of the engine 1 based on the resumption of fuel injection is not performed, and the engine 1 is started by the starting motor 2 after the engine rotational speed becomes "0".

[0044] Therefore, the lower limit value of the engine rotational speed at which the engine can be restarted only by fuel injection (recoverable combustion rotational speed threshold R1) does not need to be set considering the increase in the deceleration of the engine 1 that accompanies the brake operation of the driver.

[0045] That is, in the case where the restart request is present in the state where the brake pedal is not depressed, the region in which the engine can be restarted only by fuel injection can be expanded.

[0046] Figure 2is a timing chart showing the case where the engine 1 that has been automatically stopped is restarted, and shows the case where the engine 1 is restarted in the state where the brake is engaged.

[0047] Figure 2 The timing tl in FIG. 10 is the timing at which the automatic stop condition of the engine 1 is satisfied. In the case where the brake is engaged and the vehicle speed is reduced, the automatic stop condition is satisfied at the timing tl, and the automatic stop of the engine 1 is permitted. Figure 2

[0048] The timing t2 in FIG. 11 is the timing at which there is a request for restart of the engine 1 that is in the automatic stop. That is, the timing t2 in FIG. 11 is the timing at which any one of the above automatic restart conditions is satisfied. Figure 2 Figure 2 The timing t2 in FIG. 11 is the timing at which there is a request for restart of the engine 1 that is in the automatic stop. That is, the timing t2 in FIG. 11 is the timing at which any one of the above automatic restart conditions is satisfied.

[0049] Figure 2 At the timing t2 in FIG. 11, the engine rotation speed is greater than the recoverable combustion rotation speed threshold value Rl, but the state where the brake is engaged is changed to the state where the brake is disengaged. Therefore, the engine 1 does not perform the restart based on the combustion start implementation, and waits for the engine rotation speed to become "0" to perform the restart based on the starting motor 2 implementation.

[0050] Figure 2 The timing t3 in FIG. 12 is the timing at which the engine rotation speed becomes "0" after the request for restart. The starting motor 2 is started (engaged) at the timing t3. Figure 2 The timings t3 to t4 in FIG. 12 are the period during which the crankshaft of the engine 1 is rotated by the starting motor 2.

[0051] Figure 3 is a timing chart showing the case where the engine 1 that has been automatically stopped is restarted, and shows the case where the engine 1 is restarted in the state where the brake is disengaged and is accelerated again at the time of restart of the engine 1 that has been automatically stopped.

[0052] Figure 3 The timing tl in FIG. 10 is the timing at which the automatic stop condition of the engine 1 is satisfied. In the case where the brake is engaged and the vehicle speed is reduced, the automatic stop condition is satisfied at the timing tl, and the automatic stop of the engine 1 is permitted. Figure 3

[0053] The timing t2 in FIG. 11 is the timing at which there is a request for restart of the engine 1 that is in the automatic stop. That is, the timing t2 in FIG. 11 is the timing at which any one of the above automatic restart conditions is satisfied. Figure 3 Figure 3 Figure 3 The timing t2 in FIG. 11 is the timing at which there is a request for restart of the engine 1 that is in the automatic stop. That is, the timing t2 in FIG. 11 is the timing at which any one of the above automatic restart conditions is satisfied.

[0054] At the timing t2 in FIG. 11, the engine rotation speed is greater than the recoverable combustion rotation speed threshold value Rl, but the state where the brake is engaged is changed to the state where the brake is disengaged. Therefore, the engine 1 does not perform the restart based on the combustion start implementation, and waits for the engine rotation speed to become "0" to perform the restart based on the starting motor 2 implementation. Figure 3 ​​​​the time t2, the brake is brought to the off state, and the engine rotation speed is greater than the recoverable combustion rotation speed threshold Rl. Therefore, at the time t2, the restart of the engine 1 based on the combustion start is started. Figure 3 the time t2, the brake is brought to the off state, and the engine rotation speed is greater than the recoverable combustion rotation speed threshold Rl. Therefore, at the time t2, the restart of the engine 1 based on the combustion start is started. Figure 3 the time t3 is the timing of the initial combustion after the fuel injection is resumed.

[0055] Further, in the case where the restart request is present in the state where the clutch 4 is off and the driving force of the engine 1 is not transmitted to the drive wheels 7, if the engine rotation speed of the engine 1 is greater than or equal to the recoverable combustion rotation speed threshold Rl (rotation speed threshold), the control unit 21 starts the engine 1 by the resumption of the fuel injection even in the state where the brake is on with the brake pedal depressed.

[0056] In the state where the clutch 4 is off (clutch off), the engine 1 is not affected by the increase in deceleration accompanying the brake operation by the driver. Therefore, if the engine rotation speed of the engine 1 is greater than or equal to the recoverable combustion rotation speed threshold Rl in the state where the clutch 4 is off even in the state where the brake is on when the restart request is present, the control unit 21 starts the engine 1 by the resumption of the fuel injection.

[0057] Thus, the engine 1 can expand the region where the restart is performed by the fuel injection alone.

[0058] Figure 4 is a time chart showing the case where the engine 1 that has been automatically stopped is restarted, and shows the case where the clutch 4 is brought off when the engine 1 that has been automatically stopped is restarted.

[0059] Figure 4 the time tl is the timing at which the automatic stop condition of the engine 1 is satisfied. In Figure 4 In the case shown in FIG. 7, the automatic stop condition is satisfied at the time tl in the course where the brake is on and the vehicle speed is reduced, and the automatic stop (coast stop) of the engine 1 is permitted. In Figure 4 At the timing of the time tl, the clutch 4 is brought off as the coast stop is started.

[0060] Figure 4 the time t2 is the timing at which the restart request is present for the engine 1 that is in the automatic stop. That is, Figure 4 the time t2 in the case shown in FIG. 7 is the timing at which any one of the above automatic restart conditions is satisfied.

[0061] In the case shown in FIG. 7, the brake is brought to the on state at the time t2, the clutch 4 is off, and the engine rotation speed is greater than the recoverable combustion rotation speed threshold Rl. Therefore, at the time t2, the restart of the engine 1 based on the combustion start is started. Figure 4 the time t2, the brake is brought to the off state, and the engine rotation speed is greater than the recoverable combustion rotation speed threshold Rl. Therefore, at the time t2, the restart of the engine 1 based on the combustion start is started. Figure 4 the restart of the engine 1 based on the combustion start is started.

[0062] Figure 4 The time t3 is the timing of the initial combustion after fuel injection recovery. Figure 4 The moment t4 is the timing at which the clutch 4 engages after the combustion of the internal combustion engine 1 is started.

[0063] When a restart request is made while the internal combustion engine 1 is stopped, or when a restart request is made while the vehicle speed is less than or equal to a predetermined low speed threshold V1 where the deceleration of the internal combustion engine 1 has a smaller impact, the control unit 21 restarts the internal combustion engine 1 by restoring fuel injection, even when the brake is engaged.

[0064] When the vehicle is stationary and its speed is less than or equal to a predetermined low speed threshold V1, the internal combustion engine 1 is not affected by the increased deceleration associated with the driver's braking operation. Therefore, even when the brake is applied, the control unit 21 restarts the internal combustion engine 1 by resuming fuel injection.

[0065] Thus, the internal combustion engine 1 can expand the area where it can be restarted solely through fuel injection.

[0066] Figure 5 This is a timing diagram showing the situation when the internal combustion engine 1, which has been automatically stopped, restarts. It shows the situation where the vehicle speed is less than or equal to the low vehicle speed threshold V1 when the internal combustion engine 1, which has been automatically stopped, restarts.

[0067] Figure 5 Time t1 is the timing at which the automatic stop condition of internal combustion engine 1 is met. Figure 5 In the process of the brake being applied and the vehicle speed decreasing, the automatic stop condition is met at time t1, which permits the automatic stop of the internal combustion engine 1.

[0068] Figure 5 Time t2 is the time at which a restart request is made for the internal combustion engine 1, which is in automatic shutdown. That is, Figure 5 The time t2 in the equation is the time at which any of the above automatic restart conditions are met.

[0069] exist Figure 5 At time t2, the brakes are engaged, but the vehicle speed is less than or equal to the low speed threshold V1, and the internal combustion engine rotation speed is greater than the recoverable combustion rotation speed threshold R1. Therefore, at Figure 5 At time t2, the internal combustion engine 1 is restarted based on combustion start-up. Figure 5 The time t3 is the timing of the initial combustion after fuel injection recovery.

[0070] Figure 6is a flowchart showing a control flow of the internal combustion engine 1 of the above-described embodiment.

[0071] In step S1, it is determined whether a restart request of the internal combustion engine 1 is generated. That is, it is determined whether an automatic restart condition is established in the automatic stop of the internal combustion engine 1. In a case where it is determined in step S1 that the restart request is generated, the process proceeds to step S2. In a case where it is not determined in step S1 that the restart request is generated, the process of this time is ended.

[0072] In step S2, it is determined whether the engine rotation speed is greater than or equal to the recoverable combustion rotation speed threshold Rl. If the engine rotation speed is greater than or equal to the recoverable combustion rotation speed threshold Rl in step S2, the process proceeds to step S3. If the engine rotation speed is not greater than or equal to the recoverable combustion rotation speed threshold Rl in step S2, the process proceeds to step S7.

[0073] In step S3, it is determined whether a state where the brake is off is present. In step S3, if the state where the brake is off is present, the process proceeds to step S4. In step S3, if the state where the brake is off is not present, the process proceeds to step S5.

[0074] In step S4, the internal combustion engine 1 is started by recovery of fuel injection.

[0075] In step S5, it is determined whether a state where the clutch is off is present. If the state where the clutch is off is present in step S5, the process proceeds to step S4. If the state where the clutch is off is not present in step S5, the process proceeds to step S6.

[0076] In step S6, it is determined whether the vehicle speed is less than or equal to a low vehicle speed threshold Vl. In step S6, if the vehicle speed is less than or equal to the low vehicle speed threshold Vl, the process proceeds to step S4. In step S6, if the vehicle speed is not less than or equal to the low vehicle speed threshold Vl, the process proceeds to step S7.

[0077] In step S7, the internal combustion engine 1 is started by rotation of the crankshaft realized based on the starting motor 2.

[0078] The above-described embodiment of the present application has been described, but the present application is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist thereof.

[0079] For example, the rotation speed threshold is set in accordance with the deceleration of the internal combustion engine, but in the state where the brake is on, a response that is not set in accordance with the deceleration of the internal combustion engine can also be considered. In addition, in the process of reducing the rotation speed of the internal combustion engine based on automatic stop, in the case where there is a restart request in the state where the brake is on, the rotation speed threshold can not be set, or the rotation speed threshold can be set to infinity, and the internal combustion engine is started by rotating the internal combustion engine with the electric motor. Also, the rotation speed threshold can be set to a constant value in the state where the brake is on.

[0080] Further, the above-described embodiments relate to a control method of an internal combustion engine and a control device of an internal combustion engine.

Claims

1. A control method for an internal combustion engine, wherein, If the specified automatic stop conditions are met, fuel injection is stopped to execute the automatic stop of the internal combustion engine. If a restart request for the internal combustion engine occurs during the reduction of the engine rotation speed based on this automatic stop mechanism, the following steps are performed: If the brake is determined to be in the brake open state and the internal combustion engine rotation speed is greater than or equal to the rotation speed threshold, the internal combustion engine is restarted by restoring fuel injection without rotating the internal combustion engine crankshaft. The rotation speed threshold is defined as the lower limit of the rotation speed at which the engine can be restarted by restoring fuel injection without rotating the internal combustion engine crankshaft. If the brake is determined to be in the brake-on state and the internal combustion engine rotation speed is greater than or equal to the rotation speed threshold, the internal combustion engine is restarted by restoring fuel injection and using an electric motor to rotate the internal combustion engine crankshaft. If it is determined that the internal combustion engine's rotational speed is below the aforementioned rotational speed threshold, then regardless of the brake's status, the internal combustion engine is restarted by restoring fuel injection and using an electric motor to rotate the engine crankshaft.

2. The control method for an internal combustion engine according to claim 1, wherein, If a restart request is made while the clutch on the power transmission path that transmits the driving force of the internal combustion engine to the drive wheels is disengaged and the driving force of the internal combustion engine is not transmitted to the drive wheels, the internal combustion engine is started even when the brake is engaged by restoring fuel injection without rotating the crankshaft of the internal combustion engine.

3. The control method for an internal combustion engine according to claim 1 or 2, wherein, When a restart request is made while the vehicle driven by the internal combustion engine is stopped, the internal combustion engine is started by restoring fuel injection without rotating the crankshaft, even when the brakes are engaged.

4. The control method for an internal combustion engine according to claim 1 or 2, wherein, When a restart request is made while the vehicle speed of a vehicle powered by an internal combustion engine is less than or equal to a specified low speed threshold, the internal combustion engine is started by restoring fuel injection without rotating the crankshaft of the internal combustion engine, even when the brakes are engaged.

5. The control method for an internal combustion engine according to claim 1 or 2, wherein, The aforementioned rotational speed threshold is set based on the deceleration of the internal combustion engine.

6. The control method for an internal combustion engine according to claim 5, wherein, The aforementioned rotational speed threshold is not set based on the deceleration of the internal combustion engine when the brake is engaged.

7. The control method for an internal combustion engine according to claim 5, wherein, During the process of reducing the rotational speed of an internal combustion engine based on automatic stop, if a restart request is made while the brake is engaged, the aforementioned rotational speed threshold is not set, or the aforementioned rotational speed threshold is set to infinity. The internal combustion engine is restarted by restoring fuel injection and rotating the crankshaft of the internal combustion engine using the aforementioned electric motor.

8. The control method for an internal combustion engine according to claim 5, wherein, The aforementioned rotational speed threshold is set to a constant value when the brake is engaged.

9. A control device for an internal combustion engine, comprising: An electric motor is used to rotate a crankshaft, thereby starting an internal combustion engine. If the specified automatic stop conditions are met, the first control unit stops fuel injection to perform automatic stop of the internal combustion engine. as well as The second control unit executes the following steps when a restart request for the internal combustion engine occurs during the reduction of the engine rotation speed based on automatic stop: If the brake is determined to be in the brake open state and the internal combustion engine rotation speed is greater than or equal to the rotation speed threshold, the internal combustion engine is restarted by restoring fuel injection without rotating the internal combustion engine crankshaft. The rotation speed threshold is defined as the lower limit of the rotation speed at which the engine can be restarted by restoring fuel injection without rotating the internal combustion engine crankshaft. If the brake is determined to be in the brake-on state and the internal combustion engine rotation speed is greater than or equal to the rotation speed threshold, the internal combustion engine is restarted by restoring fuel injection and using an electric motor to rotate the internal combustion engine crankshaft. If it is determined that the internal combustion engine's rotational speed is below the aforementioned rotational speed threshold, then regardless of the brake's status, the internal combustion engine is restarted by restoring fuel injection and using an electric motor to rotate the engine crankshaft.

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