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

Abstract

To suppress an inrush current of a starter motor.SOLUTION: When a starter motor 2 is driven (started), an internal combustion engine 1 switches a supply path for power supplied from a battery 4 to the starter motor 2 to a first path. That is, the internal combustion engine 1 switches an ICR relay drive request flag from "0" to "1" at timing when an automatic restart condition is established, a cranking request flag becomes "1" and an engine speed of the internal combustion engine 1 drops to a starter motor startable speed R2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control method for an internal combustion engine and a control device for an internal combustion engine. [Background technology]

[0002] For example, Patent Document 1 discloses an engine start control device that, when an engine start request is made while the engine (internal combustion engine) is stopped, sets the current circuit from the battery to the starter motor to a first path with high resistance, and starts the engine using the starter motor.

[0003] The engine start control device disclosed in Patent Document 1 includes a determination unit, a start control unit, and a switching control unit. The determination unit determines whether various conditions are met. The start control unit controls starter start, which cranks the engine using a starter motor, and ignition start, which rotates the crankshaft by fuel injection and ignition, based on the determination result from the determination unit. The switching control unit controls switching of the starter motor's current circuit between a first path with high resistance and a second path with lower resistance than the first path, based on the determination result from the determination unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-20404 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, the starting control unit and the switching control unit are each controlled individually based on a signal representing the determination result from the determination unit, and no consideration is given to the relationship between the timing at which the starter motor starts and the timing at which the starter motor's current-carrying circuit switches to the first path with higher resistance. As a result, in Patent Document 1, the starter motor may start before the starter motor's current-carrying circuit switches to the first path with higher resistance, which could result in a large inrush current in the starter motor.

[0006] That is, when controlling the timing of starting the starter motor and the timing of switching the current supply circuit of the starter motor, there is room for further improvement in suppressing the inrush current of the starter motor. [Means for solving the problem]

[0007] The internal combustion engine of the present invention has a starter motor and a relay that switches the supply path of power supplied from a battery to the starter motor to a first path with high electrical resistance when the starter motor is started, and drives the relay so that the supply path is switched to the first path at the timing when the starter motor is driven. [Effects of the Invention]

[0008] According to the present invention, the internal combustion engine switches the power supply path to the first path, which has a high resistance, at the timing of driving (starting) the starter motor, so that the inrush current of the starter motor can be suppressed when driving the starter motor 2. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an explanatory diagram that schematically shows the system configuration of an internal combustion engine to which the present invention is applied; [Figure 2] 6 is a timing chart showing an example of changes in various states during automatic restart of an internal combustion engine of a comparative example. [Figure 3]3 is a timing chart showing an example of changes in various states during automatic restart of the internal combustion engine 1 according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will now be described in detail with reference to the drawings. Figure 1 is an explanatory diagram showing a schematic system configuration of an internal combustion engine 1 to which the present invention is applied.

[0011] The internal combustion engine 1 has a starter motor (starter) 2. The starter motor 2 can be supplied with driving power from a battery 4 via an ICR relay 3. The ICR relay 3 is capable of temporarily switching the power supply path from the battery 4 to the starter motor 2 as a countermeasure against inrush current of the starter motor 2.

[0012] The drive of the internal combustion engine 1, the starter motor 2, and the ICR relay 3 is controlled by a control unit 5 serving as a control section. That is, the fuel injection amount, fuel injection timing, etc. of the internal combustion engine 1 are controlled by the control unit 5. The drive of the starter motor 2 is controlled by the control unit 5. The switching of the power supply path by the ICR relay 3 is controlled by the control unit 5.

[0013] The starter motor 2 cranks the internal combustion engine 1 by inserting a pinion connected to a rotating shaft (not shown) of the starter motor 2 into and meshing with a ring gear connected to a crankshaft (not shown) of the internal combustion engine 1.

[0014] When starting the internal combustion engine 1, the control unit 5 issues an ON command to the ICR relay 3 to temporarily switch part of the power supply path from the battery 4 to the starter motor 2 to a predetermined first path (not shown) as a countermeasure against inrush current in the starter motor 2.

[0015] The ICR relay 3 operates in response to a command from the control unit 5 and is capable of switching a part of the power supply path from the battery 4 to the starter motor 2 from the first path to a predetermined second path (not shown), or from the second path to the first path. Here, the first path is a power supply path with a higher electrical resistance than the second path.

[0016] When the ICR relay 3 is turned on by an on command from the control unit 5, it allows power to be supplied from the battery 4 to the starter motor 2 via a first path (not shown), and when it is turned off without an on command, it allows power to be supplied from the battery 4 to the starter motor 2 via a second path (not shown) which has lower resistance than the first path. In other words, unless it receives a command from the control unit 5, the ICR relay 3 allows power to be supplied from the battery 4 to the starter motor 2 via the second path.

[0017] That is, when starting the internal combustion engine 1, the drive of the ICR relay 3 is controlled by the control unit 5. In response to an ON command from the control unit 5, the ICR relay 3 is turned ON for a predetermined time (predetermined period).

[0018] The battery 4 is mounted on the vehicle in which the internal combustion engine 1 is mounted, and is capable of supplying power to various electrical components mounted on the vehicle.

[0019] When a predetermined automatic stop condition is met while the vehicle is running or stopped, the internal combustion engine 1 automatically stops by cutting off the fuel supply. Then, when a predetermined automatic restart condition is met while the internal combustion engine 1 is automatically stopped, the internal combustion engine 1 restarts. In other words, the control unit 5 automatically stops the internal combustion engine 1 when the predetermined automatic stop condition is met, and automatically restarts the internal combustion engine 1 when the predetermined automatic restart condition is met.

[0020] The conditions for automatically stopping the internal combustion engine 1 are, for example, that the accelerator pedal is not depressed, and that the SOC (State Of Charge), which is the ratio of the remaining charge to the charge capacity of the battery 4, is greater than a predetermined battery threshold.

[0021] The internal combustion engine 1 automatically stops when all of these automatic stop conditions are met. In other words, the control unit 5 automatically stops the internal combustion engine 1 when all of these automatic stop conditions are met while the internal combustion engine 1 is operating. In other words, the control unit 5 controls the internal combustion engine 1 to automatically stop by stopping fuel injection when predetermined automatic stop conditions are met.

[0022] The automatic restart condition of the internal combustion engine 1 is, for example, that the accelerator pedal is depressed, that the SOC of the battery 4 (battery SOC) is equal to or lower than a predetermined battery threshold, and so on.

[0023] The internal combustion engine 1 restarts when a restart request is made during an automatic stop. In other words, the control unit 5 restarts the internal combustion engine 1 when any of the above-mentioned automatic restart conditions is met during an automatic stop of the internal combustion engine 1. For example, the internal combustion engine 1 during an automatic stop restarts when the SOC of the battery 4 falls below a predetermined battery threshold. In other words, the control unit 5 automatically stops and restarts the internal combustion engine 1 when a predetermined automatic restart condition is met.

[0024] Examples of automatic stopping of the internal combustion engine 1 include an idle stop, a coast stop, and a sailing stop.

[0025] The idle stop is implemented when the vehicle is temporarily stopped, for example, when the automatic stop conditions described above are met. The idle stop is also canceled when, for example, any of the automatic restart conditions described above is met.

[0026] Coast stop is implemented when, for example, the above-mentioned automatic stop conditions are met while the vehicle is traveling. Coast stop is also canceled when, for example, any of the above-mentioned automatic restart conditions is met. Note that coast stop refers to automatically stopping the internal combustion engine 1 while the vehicle is decelerating at a low vehicle speed with the brake pedal depressed.

[0027] Sailing stop is implemented when, for example, the above-mentioned automatic stop conditions are met while the vehicle is running. Sailing stop is also canceled when, for example, any of the above-mentioned automatic restart conditions is met. Sailing stop refers to automatically stopping the internal combustion engine 1 while the vehicle is coasting at medium to high vehicle speeds without the brake pedal being depressed, for example.

[0028] In other words, the above-mentioned automatic stop condition is a general concept that encompasses the idle stop condition for performing an idle stop, the coast stop condition for performing a coast stop, and the sailing stop condition for performing a sailing stop.

[0029] Furthermore, the above-mentioned automatic restart condition is a general concept that encompasses the idle stop cancellation condition for canceling the idle stop, the coast stop cancellation condition for canceling the coast stop, and the sailing stop cancellation condition for canceling the sailing stop.

[0030] Here, consider a case where the automatic restart condition is satisfied by a driver operation (change-of-mind operation), such as depressing the accelerator pedal, while the internal combustion engine 1 is automatically stopped after the automatic stop condition is satisfied, i.e., while the engine speed of the internal combustion engine 1 is decreasing toward "0" to automatically stop the engine. In this case, the internal combustion engine 1 is not in a completely stopped state where the engine speed has reached "0." Therefore, even if the automatic restart condition is satisfied, the internal combustion engine 1 may not be able to start cranking until the engine speed decreases to a speed at which the pinion on the starter motor 2 side can be thrust in to mesh with the ring gear on the internal combustion engine 1 side.

[0031] On the other hand, the ICR relay 3 can be turned on regardless of the engine speed if an on command is issued at the timing when the automatic restart condition is met, and it is possible to immediately switch the supply path of power supplied from the battery 4 to the starter motor 2 to the above-mentioned first path.

[0032] Therefore, for example, when an attempt is made to drive the starter motor 2 and switch to the ICR relay 3 at the timing when the automatic restart conditions are met, the ICR relay 3 will be turned ON at the timing when the automatic restart conditions are met, but the starter motor 2 will wait until the engine speed drops before starting, and the starter motor 2 will not start when the ICR relay 3 is ON, which may result in a large inrush current to the starter motor 2.

[0033] 2 is a timing chart showing an example of changes in various states during automatic restart of the internal combustion engine 1 of the comparative example. In the internal combustion engine 1 of the comparative example, when the automatic restart condition is satisfied, the cranking request flag, which is a cranking command, and the ICR relay drive request flag, which is an ON command for the ICR relay 3, are switched to "1."

[0034] Time t1 in FIG. 2 is the timing when the automatic restart condition is met, for example, when the brake is released (the brake pedal is not depressed) during automatic stop of the internal combustion engine 1. In the internal combustion engine 1 of the comparative example, the cranking request flag and the ICR relay drive request flag are switched from "0" to "1" at time t1 in FIG. 2. The cranking request flag becomes "1" when the automatic restart condition is met while the internal combustion engine 1 is in an automatically stopped state, and becomes "0" when the engine speed of the internal combustion engine 1 reaches a predetermined complete combustion determination speed R1. The complete combustion determination speed R1 is a threshold value used to determine whether the internal combustion engine 1 has achieved complete combustion. The internal combustion engine 1 is determined to have achieved complete combustion when the engine speed reaches or exceeds the complete combustion determination speed R1.

[0035] When the ICR relay drive request flag becomes "1", an ON command is issued to the ICR relay 3, and the ICR relay 3 immediately turns ON. In other words, the ICR relay 3 immediately turns ON at the timing t1 when the ICR relay drive request flag switches from "0" to "1".

[0036] Time t2 in Figure 2 is the timing when a predetermined time has elapsed since the ICR relay drive request flag became "1." The ICR relay drive request flag becomes "0" at time t2 in Figure 2. The ICR relay 3 immediately becomes OFF at time t2 in Figure 2 when the ICR relay drive request flag becomes "0."

[0037] In other words, in the internal combustion engine 1 of the comparative example, the power supply path from the battery 4 to the starter motor 2 is immediately switched to the first path with high resistance at the timing of time t1 in Figure 2, and the power supply path from the battery 4 to the starter motor 2 is immediately switched to the second path with low resistance at the timing of time t2 in Figure 2.

[0038] Time t3 in Figure 2 is the timing when the engine speed of the internal combustion engine 1 drops to the starter motor startable speed R2, at which the pinion on the starter motor 2 side can be thrust in to mesh with the ring gear on the internal combustion engine 1 side.

[0039] In the internal combustion engine 1 of the comparative example, the change-of-mind operation permission flag and the starter drive request flag are each switched from "0" to "1" at time t3 in Figure 2. The change-of-mind operation permission flag is switched from "0" to "1" for a predetermined time when the engine speed of the internal combustion engine 1 falls below the starter motor startable speed R2 while the automatic restart conditions are met.

[0040] More specifically, when the automatic restart condition is met and the engine speed of the internal combustion engine 1 falls within a range of less than the starter motor startable speed R2 and greater than a predetermined change-of-mind operation allowable lower limit speed R3, the change-of-mind operation permission flag switches from "0" to "1" for a predetermined time. The starter drive request flag immediately switches from "0" to "1" when the change-of-mind operation permission flag becomes "1," and immediately switches from "1" to "0" when the engine speed of the internal combustion engine 1 becomes greater than or equal to the complete combustion determination speed R1. In other words, the starter drive request flag switches from "0" to "1" when the cranking request flag becomes "1" and the engine speed of the internal combustion engine 1 becomes less than the starter motor startable speed R2, and then switches from "1" to "0" when the engine speed of the internal combustion engine 1 becomes greater than or equal to the complete combustion determination speed R1.

[0041] At time t3, power supply from the battery 4 to the starter motor 2 begins via the second path. Power is supplied to the starter motor 2 until time t4, when the engine speed of the internal combustion engine 1 becomes equal to or higher than the complete combustion determination speed R1. In other words, the starter motor 2 is in an operating (driving) state from time t3 to time t4. At this time, power is supplied from the battery 4 to the starter motor 2 via the second path from the start of the starter motor 2. Therefore, when the starter motor 2 starts, the inrush current of the starter motor 2 increases, and the voltage of the battery 4 drops significantly due to the influence of the inrush current at time t3, when the starter motor 2 begins operating.

[0042] In contrast to such a comparative example, the internal combustion engine 1 of the embodiment according to the present invention switches the supply path of electric power supplied from the battery 4 to the starter motor 2 to the first path at the timing when the starter motor 2 is driven (started). That is, the internal combustion engine 1 of the embodiment does not switch the ICR relay drive request flag from "0" to "1" at the timing when the automatic restart condition is satisfied and the cranking request flag is switched from "0" to "1", but rather switches the ICR relay drive request flag from "0" to "1" at the timing when the cranking request flag becomes "1" and the engine speed of the internal combustion engine 1 drops to the starter motor startable speed R2.

[0043] 3 is a timing chart showing an example of changes in various states during automatic restart of the internal combustion engine 1 of the embodiment according to the present invention. In the internal combustion engine 1 of the embodiment according to the present invention, after the automatic restart condition is met, the ICR relay drive request flag is switched to "1" at the timing when the change of mind operation permission flag is switched to "1".

[0044] Time t1 in Fig. 3 is the timing when the automatic restart condition is met, for example, by the brake being released (the brake pedal being released) during automatic stop of the internal combustion engine 1. In the internal combustion engine 1 according to the embodiment of the present invention, the cranking request flag is switched from "0" to "1" at the timing of time t1 in Fig. 3.

[0045] Time t2 in Fig. 3 is the timing when the engine speed of the internal combustion engine 1 of the embodiment according to the present invention drops to the starter motor startable speed R2. In the internal combustion engine 1 of the embodiment according to the present invention, the ICR relay drive request flag, the change-of-mind operation permission flag, and the starter drive request flag are all switched from "0" to "1" at time t2 in Fig. 3. As a result, the ICR relay 3 immediately enters the ON state at time t2 in Fig. 3 when the ICR relay drive request flag switches from "0" to "1." Also, the starter motor 2 immediately enters the operating state at time t2 in Fig. 3 when the starter drive request flag switches from "0" to "1."

[0046] In other words, in the internal combustion engine 1 according to an embodiment of the present invention, at time t2 in Figure 3, the power supply path from the battery 4 to the starter motor 2 is immediately switched to the first path with high resistance, and the starter motor 2 is immediately started (driven) by the power supplied via the first path.

[0047] Time t3 in Fig. 3 is the timing when a predetermined time has elapsed since the ICR relay drive request flag became "1." The ICR relay drive request flag switches from "1" to "0" at time t3 in Fig. 3. The ICR relay 3 immediately becomes OFF at time t3 in Fig. 3 when the ICR relay drive request flag becomes "0."

[0048] Time t4 in Fig. 3 is the timing when the engine speed of the internal combustion engine 1 of the embodiment according to the present invention becomes equal to or higher than the complete combustion determination speed R1. In the internal combustion engine 1 of the embodiment according to the present invention, the cranking request flag and the starter drive request flag become "0" at time t4 in Fig. 3. The starter motor 2 immediately comes to a stop at time t4 when the starter drive request flag switches from "1" to "0."

[0049] In the internal combustion engine 1 according to the embodiment of the present invention, the battery voltage drops due to the influence of an inrush current at the timing of time t3 in Fig. 3 when the starter motor 2 starts to operate. However, in the internal combustion engine 1 according to the embodiment of the present invention, at this time (time t3 in Fig. 3), the starter motor 2 is supplied with power from the battery 4 via the first path, which has a large resistance.

[0050] Therefore, the internal combustion engine 1 of the embodiment according to the present invention can suppress the inrush current of the starter motor 2 when the starter motor 2 is driven (started) compared to the internal combustion engine 1 of the comparative example in which power is supplied from the battery 4 via the second path with low resistance when the starter motor 2 is activated. That is, the internal combustion engine 1 of the embodiment according to the present invention switches the power supply path between the battery 4 and the starter motor 2 from the second path to the first path with high resistance at the timing of driving (starting) the starter motor 2, thereby suppressing the inrush current of the starter motor 2 and suppressing a voltage drop of the battery 4 at the timing of driving (starting) the starter motor 2 (time t3 in FIG. 3). The amount of drop V1 in the battery voltage at time t3 in FIG. 3 is smaller than the amount of drop V0 in the battery voltage at time t2 in FIG. 2.

[0051] In the internal combustion engine 1 according to the embodiment of the present invention, even if the automatic restart conditions are met by the driver's operation (change of mind operation) during an automatic stop such as an idle stop, the ICR relay 3 is activated at the desired timing, thereby suppressing the inrush current of the starter motor 2 when the starter motor 2 is driven (started).

[0052] Furthermore, in the internal combustion engine 1 of the embodiment according to the present invention, the starter motor start condition for starting the starter motor 2 is that the engine speed of the internal combustion engine 1 becomes equal to or lower than a predetermined starter motor startable speed R2, which is a preset predetermined speed, when the automatic restart condition is met.

[0053] More specifically, the starter motor start condition is that if the engine speed of the internal combustion engine 1 is higher than the starter motor startable speed R2 when the automatic restart condition is met, the engine speed of the internal combustion engine 1 becomes equal to or lower than the starter motor startable speed R2. Also, the starter motor start condition is that the automatic restart condition is met when the engine speed of the internal combustion engine 1 is "0".

[0054] In other words, in the internal combustion engine 1 of the embodiment according to the present invention, if the engine speed is "0" and the engine is stopped when the automatic restart conditions are met, the power supply path from the battery 4 to the starter motor 2 is immediately switched to the first path, which has a higher resistance, at the timing when the automatic restart conditions are met, and the starter motor 2 is immediately started (driven) by the power supplied via the first path.

[0055] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0056] The above-described embodiment relates to a control method for the internal combustion engine 1 and a control device for the internal combustion engine 1. [Explanation of symbols]

[0057] 1...Internal combustion engine 2...Starter motor 3...ICR relay 4. Battery 5...Control unit

Claims

1. a starter motor that is driven when starting the internal combustion engine; a relay that switches a power supply path from a battery to the starter motor to a first path with a large electrical resistance when the starter motor is started. a control method for an internal combustion engine, comprising: driving the relay so that the supply path is switched to the first path at a timing when the starter motor is driven.

2. A control method for an internal combustion engine, which automatically stops the engine when predetermined automatic stop conditions are met, and automatically restarts the engine by driving a starter motor when predetermined automatic restart conditions are met during the automatic stop and predetermined starter motor start conditions are met, 2. The control method for an internal combustion engine according to claim 1, wherein, when the automatic restart condition is satisfied while the internal combustion engine is automatically stopped due to satisfaction of the automatic stop condition and the engine speed is decreasing, the relay is driven so that the supply path is switched to the first path not at the timing when the automatic restart condition is satisfied but at the timing when the starter motor start condition is satisfied after the automatic restart condition is satisfied.

3. 3. The control method for an internal combustion engine according to claim 2, wherein, when the automatic restart condition is satisfied in a state where the engine speed is zero due to the automatic stop, the relay is driven so that the supply path is switched to the first path at a timing when the automatic restart condition is satisfied.

4. 4. The method for controlling an internal combustion engine according to claim 3, wherein the starter motor starting condition is that the engine speed of the internal combustion engine is equal to or lower than a predetermined speed.

5. a starter motor that is driven when starting the internal combustion engine; a relay that switches a power supply path from a battery to the starter motor to a first path having a large electrical resistance when the starter motor is started; a control unit that drives the relay so that the supply path is switched to the first path at a timing when the starter motor is driven.

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