JP2022052806A - Internal combustion engine control method and internal combustion engine control apparatus - Google Patents

Abstract

To accurately determine how to restart an internal combustion engine that has automatically stopped.SOLUTION: In a case where restart is required when a revolution speed of an internal combustion engine is reduced due to an automatic stop, the internal combustion engine is restarted by restarting fuel injection if an engine revolution speed is equal to or higher than a given combustion recoverable revolution speed threshold at which the engine can be restarted solely by fuel injection, or the engine is started by using a starter motor if the engine revolution speed is lower than the combustion recoverable revolution speed threshold. The combustion recoverable revolution speed threshold is set in accordance with deceleration of engine revolution as a crank shaft of the engine revolves a given angle or more after the fuel injection is stopped. The combustion recoverable revolution speed threshold is set in accordance with friction of the engine until the crank shaft of the engine revolves a given angle or more after the fuel injection is stopped.SELECTED DRAWING: Figure 4

Description

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

Conventionally known, idle stop control of an internal combustion engine that automatically stops an internal combustion engine when a predetermined automatic stop condition is satisfied during idle operation and automatically restarts the internal combustion engine when a predetermined automatic restart condition is satisfied during automatic stop. ing.

For example, in Patent Document 1, when fuel injection is stopped in order to automatically stop the internal combustion engine and a request for restarting the internal combustion engine is made while the engine speed is decreasing, the decrease speed of the engine rotation speed is taken into consideration and re-started. The predicted engine rotation speed at the ignition timing that generates the first combustion is estimated from the generation timing of the start request, and it is possible to return to self-reliance depending on whether the predicted engine rotation speed is equal to or higher than the preset standard size threshold (restart of fuel injection). It is judged whether it can be started by.

Japanese Unexamined Patent Publication No. 2011-157946

However, even if the automatic stop condition is satisfied and the fuel injection stop is determined (permitted), the combustion of the cylinder injected with fuel by the time the fuel injection stop is determined occurs after the fuel injection stop is determined, so the engine rotation speed is high. It does not decrease immediately after the decision to stop fuel injection.

Therefore, immediately after it is determined that the fuel injection is stopped, the combustion torque still remains in the internal combustion engine. Therefore, it may not be possible to accurately predict how the engine rotation speed will decrease from the decrease speed of the engine rotation speed immediately after it is determined that the fuel injection has stopped.

That is, when restarting an internal combustion engine whose engine rotation speed is decreasing due to automatic stop, there is room for further improvement in determining whether or not the restart is possible only by restarting fuel injection.

The internal combustion engine of the present invention has a predetermined rotation speed threshold or higher at which the engine rotation speed can be restarted only by fuel injection when the internal combustion engine is requested to be restarted while the engine rotation speed is reduced due to the automatic stop of the internal combustion engine. If there is, the internal combustion engine is started by restarting the fuel injection, and if the engine rotation speed of the internal combustion engine is lower than the above rotation speed threshold, the crankshaft of the internal combustion engine is rotated and started by using an electric motor. Then, the rotation speed threshold is set according to the deceleration of the engine rotation when the crankshaft of the internal combustion engine rotates by a predetermined angle or more after the fuel injection is stopped.

According to the present invention, the rotation speed threshold is not based on the deceleration of the engine rotation immediately after the fuel injection is permitted to stop, so it is possible to accurately determine how to restart the automatically stopped internal combustion engine (). Judgment) can be done.

An explanatory diagram schematically showing an outline of a system configuration of an internal combustion engine to which the present invention is applied. An explanatory diagram schematically showing an example of a map used when calculating the combustion recoverable rotation speed threshold value from the target power generation voltage and the cooling water temperature. Timing chart showing the control status of the internal combustion engine after the automatic stop condition is satisfied. The flowchart which shows the control flow of the internal combustion engine which concerns on this invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram schematically showing an outline of a system configuration of an internal combustion engine 1 to which the present invention is applied.

The internal combustion engine 1 is, for example, a multi-cylinder spark-ignition gasoline engine, which is mounted as a drive source in a vehicle such as an automobile. The internal combustion engine 1 may be a diesel engine.

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 optimally controlled by the control unit 21 described later.

Further, the internal combustion engine 1 has a starter motor 2 as an electric motor. The starter motor 2 rotates the crankshaft (not shown) of the internal combustion engine 1 in a stopped state to start the internal combustion engine 1 (cranking start). The starter motor 2 is controlled by a control unit 21 described later.

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 via the final gear 6. It is transmitted to the drive wheel 7 of the vehicle.

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

The clutch 4 is located between the torque converter 3 and the CVT 5, and is engaged when the drive torque from the internal combustion engine 1 can be transmitted to the drive wheels 7. That is, the clutch 4 is arranged on the power transmission path that transmits the driving force of the internal combustion engine 1 to the driving wheels 7. The clutch 4 engagement / release operation is performed based on a control command from the control unit 21, which will be described later. The clutch 4 is released, for example, at the time of a coast stop described later.

The CVT 5 has a primary pulley 8 on the input side, a secondary pulley 9 on the output side, and a belt 10 for transmitting the rotation of the primary pulley 8 to the secondary pulley 9.

For example, the CVT 5 changes the width of the V-groove (not shown) of the primary pulley 8 and the secondary pulley 9 on which the belt 10 is wound by using hydraulic pressure, and contacts the belt 10 with the primary pulley 8 and the secondary pulley 9. The radius is changed and the gear ratio is changed steplessly.

Although the CVT 5 is used as the transmission, it is also possible to use a stepped automatic transmission instead of the CVT 5. In this case, the clutch 4 is configured by diverting a plurality of friction fastening elements in the stepped automatic transmission.

The control unit 21 includes a crank angle sensor 22 that detects the crank angle of the crank shaft, an accelerator opening sensor 23 that detects the amount of depression of the accelerator pedal (not shown), a vehicle speed sensor 24 that detects the vehicle speed of the vehicle, and a brake pedal. A brake sensor (brake switch) 25 that detects the amount of depression (not shown), and a catalyst that detects the catalyst temperature of an exhaust purification catalyst (not shown) provided in the exhaust passage (not shown) of the internal combustion engine 1. Detection signals of various sensors such as the temperature sensor 26 and the water temperature sensor 27 for detecting the cooling water temperature (water temperature) of the internal combustion engine 1 are input.

The control unit 21 calculates the required load (engine load) of the internal combustion engine 1 by using the detected value of the accelerator opening sensor 23.

The control unit 21 can detect SOC (State Of Charge), which is the ratio of the remaining charge to the charge capacity of the vehicle-mounted battery (not shown). That is, the control unit 21 corresponds to the battery SOC detection unit.

The control unit 21 calculates the target power generation voltage of the alternator (not shown) that generates power for charging the vehicle-mounted battery or the like according to the operating state of the vehicle-mounted battery such as SOC. The alternator is an auxiliary machine of the internal combustion engine 1.

The crank angle sensor 22 can detect the engine rotation speed (engine rotation speed) of the internal combustion engine 1.

When a predetermined automatic stop condition is satisfied when the vehicle is running or the vehicle is stopped, the internal combustion engine 1 stops the fuel supply and automatically stops. Then, the internal combustion engine 1 restarts when a predetermined automatic restart condition is satisfied during the automatic stop. That is, the control unit 21 automatically stops the internal combustion engine 1 when the predetermined automatic stop condition is satisfied, and automatically restarts the internal combustion engine 1 when the predetermined automatic restart condition is satisfied.

The automatic stop conditions of the internal combustion engine 1 are, for example, a state in which the accelerator pedal is not depressed, the battery SOC of the vehicle-mounted battery is larger than a predetermined battery threshold SOCth, and the catalyst temperature of the exhaust gas purification catalyst is a predetermined first. 1 It is higher than the catalyst temperature threshold value T1 and the like.

The internal combustion engine 1 automatically stops when all of these automatic stop conditions are satisfied. In other words, the control unit 21 automatically stops the internal combustion engine 1 when all of these automatic stop conditions are satisfied during the operation of the internal combustion engine 1. That is, the control unit 21 corresponds to a first control unit that stops fuel injection and automatically stops the internal combustion engine 1 when a predetermined automatic stop condition is satisfied. When all of these automatic stop conditions are satisfied during the operation of the internal combustion engine 1, the control unit 21 permits the stop of the fuel injection and stops the fuel injection.

The conditions for automatic restart of the internal combustion engine 1 are, for example, that the accelerator pedal is depressed, that the battery SOC of the vehicle-mounted battery is equal to or less than a predetermined battery threshold SOCth, and that the catalyst temperature of the exhaust gas purification catalyst is a predetermined first. 1 The catalyst temperature threshold is T1 or less.

The internal combustion engine 1 restarts when there is a restart request during automatic stop. In other words, the control unit 21 restarts the internal combustion engine 1 when any of the above-mentioned automatic restart conditions is satisfied during the automatic stop of the internal combustion engine 1. For example, the internal combustion engine 1 that is automatically stopped restarts when the battery SOC of the vehicle-mounted battery becomes equal to or less than the battery threshold SOCth as a predetermined value.

Examples of the automatic stop of the internal combustion engine 1 include an idle stop, a coast stop, and a sailing stop.

The idle stop is performed when the vehicle is temporarily stopped, for example, when the above automatic stop condition is satisfied. Further, the idle stop is released when, for example, any of the above-mentioned automatic restart conditions is satisfied.

The coast stop is performed when, for example, the above-mentioned automatic stop condition is satisfied while the vehicle is running. Further, the coast stop is canceled when, for example, any of the above-mentioned automatic restart conditions is satisfied. The coast stop is, for example, the automatic stop of the internal combustion engine 1 during deceleration in a state where the brake pedal is depressed at a low vehicle speed.

The sailing stop is performed when, for example, the above-mentioned automatic stop condition is satisfied while the vehicle is running. Further, the sailing stop is canceled when, for example, any of the above-mentioned automatic restart conditions is satisfied. The sailing stop is, for example, the automatic stop of the internal combustion engine 1 during inertial running in which the brake pedal is not depressed at a medium or high vehicle speed.

When the control unit 21 receives a request to restart the internal combustion engine 1 while the engine rotation speed of the internal combustion engine 1 is reduced due to automatic stop, the control unit 21 can restart the internal combustion engine 1 only by injecting fuel. If it is equal to or higher than the recoverable rotation speed threshold (rotation speed threshold), the internal combustion engine 1 is started (combustion start) by restarting fuel injection, and if the engine rotation speed of the internal combustion engine 1 is lower than the combustion recoverable rotation speed threshold, the starter motor The internal combustion engine 1 is started (cranked) by rotationally driving the crankshaft using 2. That is, the control unit 21 corresponds to the second control unit.

The combustion recoverable rotation speed threshold is set according to the deceleration of the engine rotation when the crankshaft of the internal combustion engine 1 rotates by a predetermined angle or more after the fuel injection is permitted to stop (after the fuel injection is stopped). .. Further, the combustion recoverable rotation speed threshold value corresponds to the friction of the internal combustion engine 1 until the crankshaft of the internal combustion engine 1 rotates by a predetermined angle or more after the stop of the fuel injection is permitted (after the fuel injection is stopped). Is set.

The combustion recoverable rotation speed threshold value is set by the control unit 21. That is, the control unit 21 corresponds to the rotation speed threshold setting unit.

Immediately after the stop of the fuel injection of the internal combustion engine 1 is permitted, the combustion of the cylinder in which the fuel is injected occurs immediately before the stop of the fuel injection is permitted, so that the engine rotation speed does not decrease (decrease) immediately.

That is, immediately after it is determined that the fuel injection is stopped, the combustion torque still remains in the internal combustion engine 1, so that the engine rotation (engine rotation) is caused by the friction of the internal combustion engine 1 from the descent speed (deceleration) of the engine rotation (engine rotation). ) Can not be predicted how it will descend.

Therefore, when the combustion recoverable rotation speed threshold is set according to the deceleration of the engine rotation, the crankshaft of the internal combustion engine 1 is in a state of rotating by a predetermined angle or more after the stop of fuel injection is permitted.

As a result, the combustion recoverable rotation speed threshold value is not based on the deceleration of the engine rotation immediately after the fuel injection is permitted to stop, so it is possible to accurately determine how to restart the automatically stopped internal combustion engine 1. (Judgment) can be done. In other words, immediately after the stop of fuel injection is permitted, it is not determined whether or not it can be restarted only by fuel injection using the rotation speed threshold set according to the deceleration of the engine rotation, so that it is automatic. It is possible to accurately determine (determine) how to restart the stopped internal combustion engine 1.

Further, the predetermined rotation angle is an angle at which combustion of the fuel-injected cylinder ends at least before the fuel injection is allowed to stop.

This makes it possible to switch to the combustion recoverable rotation speed threshold according to the deceleration of the engine rotation as quickly as possible, and widen (expand) the area where the automatically stopped internal combustion engine 1 is started by restarting fuel injection. Is possible.

When the combustion recoverable rotation speed threshold value is set according to the deceleration of the engine rotation, it is set so as to increase as the deceleration of the engine rotation increases.

By setting the combustion recoverable rotation speed threshold to be larger as the deceleration of the engine rotation becomes larger, the automatically stopped internal combustion engine 1 can be reliably started by restarting the fuel injection.

Further, the combustion recoverable rotation speed threshold value is set according to the friction of the internal combustion engine 1 from the time when the fuel injection is allowed to stop until the crankshaft of the internal combustion engine 1 rotates by a predetermined angle or more.

As a result, the internal combustion engine 1 can be started by resuming fuel injection even until the combustion recoverable rotation speed threshold can be set according to the deceleration of the engine rotation.

Here, when the combustion recoverable rotation speed threshold value is set according to the friction of the internal combustion engine 1, for example, the auxiliary load or the cooling water temperature of the internal combustion engine 1 may be used as a substitute characteristic of the friction. That is, when the combustion recoverable rotation speed threshold value is set according to the friction of the internal combustion engine 1, it may be set according to the auxiliary load of the internal combustion engine 1 or the cooling water temperature. The auxiliary load is, for example, the target power generation voltage of the alternator.

By using the auxiliary load or the cooling water temperature as a substitute characteristic of friction, it is possible to finely set the combustion recoverable rotation speed threshold value according to the friction.

The combustion recoverable rotation speed threshold value may be calculated using, for example, the target power generation voltage of the alternator and the cooling water temperature, and using a map as shown in FIG. 2 stored in the control unit 21. FIG. 2 is an explanatory diagram schematically showing an example of a map used when calculating the combustion recoverable rotation speed threshold value from the target power generation voltage and the cooling water temperature.

The combustion recoverable rotation speed threshold value is set to increase as the target power generation voltage (auxiliary load) of the alternator increases or the cooling water temperature decreases. The friction of the internal combustion engine 1 increases as the target power generation voltage (auxiliary load) of the alternator increases or as the cooling water temperature decreases.

By setting the combustion recoverable rotation speed threshold value to be larger as the friction becomes larger, the automatically stopped internal combustion engine 1 can be reliably started by restarting the fuel injection.

The combustion recoverable rotation speed threshold value may be set using only the auxiliary load of the internal combustion engine 1 (the target power generation voltage of the alternator). In this case, the combustion recoverable rotation speed threshold value is set so as to increase as the auxiliary load (target power generation voltage of the alternator) increases. Further, the combustion recoverable rotation speed threshold value may be set using only the cooling water temperature. In this case, the combustion recoverable rotation speed threshold value is set to increase as the cooling water temperature decreases.

FIG. 3 is a timing chart showing a control state of the internal combustion engine 1 after the automatic stop condition is satisfied.

In FIG. 3, the automatic stop condition of the internal combustion engine 1 is satisfied at time t1. That is, the stop of fuel injection is permitted at the timing of time t1. The time t2 in FIG. 3 is the timing at which the crankshaft of the internal combustion engine 1 rotates by a predetermined angle after the stop of fuel injection is permitted. The time t3 in FIG. 3 is the timing at which the engine rotation speed of the internal combustion engine 1 becomes equal to or less than the combustion recoverable rotation speed threshold value. The time t4 in FIG. 3 is the timing at which the engine rotation speed becomes “0”.

The characteristic line A shown by the broken line in FIG. 3 shows the change in the combustion recoverable rotation speed threshold value.

The deceleration of the engine rotation is calculated from the timing of time t2 to the timing of time t4 when the engine rotation speed of the internal combustion engine 1 becomes "0". Therefore, the combustion recoverable rotation speed threshold is calculated from, for example, a map (see FIG. 2) allocated according to the target power generation voltage of the alternator and the cooling water temperature between the time t1 and the time t2.

The combustion recoverable rotation speed threshold is calculated according to the deceleration of the engine rotation from time t2 to time t4. The combustion recoverable rotation speed threshold value between the times t2 and t4 is set so as to increase as the deceleration of the engine rotation increases.
Therefore, the characteristic line A (combustion recoverable rotation speed threshold value) in FIG. 3 is a curve in which the deceleration of the engine rotation in FIG. 3 is convex upward as a whole. In No. 3, the curve is convex downward.

In FIG. 3, the period from time t1 to time t3 when the engine rotation speed is equal to or higher than the combustion recoverable rotation speed threshold value is a region in which restart is possible only by fuel injection. In FIG. 3, the period after the time t3 when the engine rotation speed becomes less than the combustion recoverable rotation speed threshold is the region where the internal combustion engine 1 is rotated and started by using the starter motor 2.

FIG. 4 is a flowchart showing a control flow of the internal combustion engine 1 in the above-described embodiment.

In step S1, it is determined whether or not the fuel injection is stopped due to the automatic stop of the internal combustion engine 1. If the fuel injection is stopped by the automatic stop of the internal combustion engine 1 in step S1, the process proceeds to step S4. If the fuel injection is not stopped due to the automatic stop of the internal combustion engine 1 in step S1, the process proceeds to step S2.

In step S2, it is determined whether or not the automatic stop of the internal combustion engine 1 has been started. That is, it is determined whether or not the automatic stop condition of the internal combustion engine 1 is satisfied during fuel injection. If the automatic stop of the internal combustion engine 1 is started in step S2, the process proceeds to step S3. If the automatic stop of the internal combustion engine 1 is not started in step S2, the current routine is terminated.

In step S3, the fuel injection of the internal combustion engine 1 is stopped.

In step S4, it is determined whether or not the crankshaft of the internal combustion engine 1 has rotated by a predetermined angle or more after the fuel injection is stopped.

If the crankshaft of the internal combustion engine 1 is rotated by a predetermined angle or more after the fuel injection is stopped in step S4, the process proceeds to step S5. If the crankshaft of the internal combustion engine 1 has not rotated by a predetermined angle or more after the fuel injection is stopped in step S4, the process proceeds to step S6.

In step S5, the combustion recoverable rotation speed threshold value is set according to the deceleration of the engine rotation.

In step S6, the combustion recoverable rotation speed threshold value is set according to the friction of the internal combustion engine 1.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

The above-described embodiment relates to a control method for an internal combustion engine and a control device for the internal combustion engine.

1 ... Internal combustion engine 2 ... Starter motor 3 ... Torque converter 4 ... Clutch 5 ... CVT
6 ... Final gear 7 ... Drive wheel 8 ... Primary pulley 9 ... Secondary pulley 10 ... Belt 21 ... Control unit 22 ... Crank angle sensor 23 ... Accelerator opening sensor 24 ... Vehicle speed sensor 25 ... Brake sensor 26 ... Catalyst temperature sensor 27 ... Water temperature Sensor

Claims (7)

When the predetermined automatic stop condition is satisfied, the fuel injection is stopped and the internal combustion engine is automatically stopped. If the internal combustion engine is requested to restart while the internal combustion engine rotation speed is reduced due to this automatic stop, the internal combustion engine is rotated. If the speed is equal to or higher than the predetermined rotation speed threshold that can be restarted only by fuel injection, the internal combustion engine is started by restarting the fuel injection, and if the engine rotation speed of the internal combustion engine is lower than the above rotation speed threshold, an electric motor is used. Start by rotating the internal combustion engine,
The rotation speed threshold is a control method for an internal combustion engine, which is set according to the deceleration of the engine rotation when the crankshaft of the internal combustion engine rotates by a predetermined angle or more after the fuel injection is stopped. The control method for an internal combustion engine according to claim 1, wherein the predetermined angle is at least an angle at which combustion of the fuel-injected cylinder ends before the fuel injection is permitted to stop. The control method for an internal combustion engine according to claim 1 or 2, wherein the rotation speed threshold value is set to increase as the deceleration of the engine rotation speed increases. One of claims 1 to 3, wherein the rotation speed threshold value is set according to the friction of the internal combustion engine from the time when the fuel injection is stopped until the crankshaft of the internal combustion engine rotates by a predetermined angle or more. The method for controlling an internal combustion engine described. The control method for an internal combustion engine according to claim 4, wherein the rotation speed threshold value is set by using the auxiliary load of the internal combustion engine or the cooling water temperature as a substitute characteristic of the friction. The control method for an internal combustion engine according to claim 5, wherein the rotation speed threshold value is set to increase as the auxiliary load increases or the cooling water temperature decreases. An electric motor that can start an internal combustion engine and
A first control unit that stops fuel injection and automatically stops the internal combustion engine when a predetermined automatic stop condition is satisfied.
When there is a request to restart the internal combustion engine while the engine rotation speed of the internal combustion engine is decreasing due to automatic stop, if the engine rotation speed of the internal combustion engine is equal to or higher than the predetermined rotation speed threshold that can be restarted only by fuel injection, fuel is used. A second control unit that starts the internal combustion engine by restarting injection, and starts the internal combustion engine using the electric motor if the engine rotation speed of the internal combustion engine is lower than the rotation speed threshold.
The internal combustion engine is characterized by having a rotation speed threshold setting unit that sets the rotation speed threshold according to the deceleration of the engine rotation when the crankshaft of the internal combustion engine rotates by a predetermined angle or more after the fuel injection is stopped. Control device.

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