Method and device for controlling restart of internal combustion engine

Abstract

To execute a restart at an appropriate timing for both directions of normal rotation and reverse rotation of a crank shaft when there is a restart request before a complete stop after automatic stopping by idle stop.SOLUTION: After automatic stopping, a rotation speed and a crank angle of an internal combustion engine are determined upon every input of a crank angle sensor signal P1, P2 ... which is generated by a crank angle sensor at every predefined crank angle for both directions of normal rotation and reverse rotation. Based on the rotation speed and the crank angle, an estimated time for the rotation speed of the internal combustion engine to reach a predefined starter acceptance rotation speed range ΔNeST in which a starter motor can be driven is determined, and a timer is set. A timer value is updated upon each input of the crank angle sensor signal P1, P2 ..., and is decremented with lapse of time. When the timer is 0, it is determined whether or not a restart request (time t2) has already been made, and driving of the starter motor is started if a restart request has already been made (time t4).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to restart control when an internal combustion engine is automatically stopped in accordance with predetermined idle stop conditions, and then restart is performed using a starter motor when a restart request is made before the rotation of the crankshaft has completely stopped. [Background technology]

[0002] In a vehicle equipped with an idle stop function, when a predetermined idle stop condition is met, such as when the vehicle is stopped temporarily at an intersection, the internal combustion engine is automatically stopped. After that, when a start request is made following the fulfillment of a release condition, such as when the brake pedal is released, the engine is restarted using the starter motor.

[0003] In some cases, such as when the brake pedal is released immediately after the idle stop condition is satisfied, a restart request may be issued before the rotation of the crankshaft has completely stopped. Restarting the engine using a starter motor generally requires that the engine speed be sufficiently low. However, the crank angle sensor used to detect the engine speed is configured to output a pulse signal, i.e., a crank angle sensor signal, at each relatively large predetermined crank angle. Therefore, when the engine speed is low, the output interval (time interval) of the crank angle sensor signal becomes long.

[0004] Regarding this problem, Patent Document 1 discloses a technique for predicting the engine speed after a predetermined time during inertial rotation by interpolating and calculating the engine speed and crank angle phase every 10 ms using signals from a crank angle sensor when the output interval of the crank angle sensor signal becomes large. This technique predicts the timing when the actual engine speed will become 0 based on the predicted change in speed, and meshes the pinion of the starter motor with the ring gear at this timing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-190159 Summary of the Invention [Problem to be solved by the invention]

[0006] When an internal combustion engine automatically stops, the crankshaft rotates due to inertia, and as the engine comes to a complete stop, the crankshaft may rotate in the reverse direction due to compression pressure in the cylinder and valve spring reaction force. Patent Document 1 calls this reverse rotation "swing-back," and discloses that restarting is prohibited during this swing-back period. However, with the method of Patent Document 1, which uses past signals to interpolate and calculate the engine speed and crank angle phase every 10 ms, it is not possible to determine the appropriate timing until a certain amount of time has passed since the swing-back period ended, which could result in a significant delay between the restart request and the actual restart. [Means for solving the problem]

[0007] The present invention provides a restart control method for an internal combustion engine, which automatically stops the internal combustion engine in accordance with predetermined idle stop conditions, and then restarts the engine using a starter motor when a restart request is made before the rotation of the crankshaft has completely stopped, comprising: After the automatic stop, the engine speed and crank angle are calculated for both forward and reverse rotations each time the crank angle sensor signal is input, which is generated at every predetermined crank angle. Based on the rotation speed and crank angle, a predicted time is calculated for the rotation speed of the internal combustion engine to reach a predetermined permissible starter rotation speed range in which the starter motor can be driven, and the predicted time is updated each time the crank angle sensor signal is input. When this predicted time has elapsed, it is determined whether a restart request has already been made; If a restart request has already been made, the starter motor starts to be driven. [Effects of the Invention]

[0008] According to this invention, the predicted time is updated for both forward and reverse rotations each time a crank angle sensor signal is input, and when this predicted time has elapsed, if a restart request has already been made, the starter motor begins to drive, so that restart by the starter motor can be performed with relatively simple control at a timing when the actual rotation speeds for both forward and reverse rotations are expected to be within the starter's allowable rotation speed range. Therefore, restart can be achieved without a significant delay from the restart request. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a functional block diagram of a restart control device according to an embodiment. [Figure 2] 4 is a flowchart showing a process flow of restart control according to an embodiment. [Figure 3] 4 is a time chart showing an example of operation of an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. A vehicle equipped with an internal combustion engine according to the embodiment is equipped with a so-called idle stop function. When predetermined idle stop conditions, such as releasing the accelerator pedal and pressing the brake pedal, are met, such as when the vehicle is temporarily stopped at an intersection, the internal combustion engine is automatically stopped. In other words, fuel injection and ignition are stopped in response to a stop command for the internal combustion engine, and the crankshaft rotates by inertia for a short period of time before coming to a complete stop. When a predetermined release condition, such as releasing the brake pedal, is met during the idle stop state, a restart request is output, and the internal combustion engine is restarted as described below. In the embodiment, the internal combustion engine is connected to a stepped automatic transmission via a torque converter, enabling automatic stopping and restart when the vehicle is stopped while the automatic transmission is in the so-called D range.

[0011] FIG. 1 is a functional block diagram of a restart control device 1 according to one embodiment. The restart control device 1 is configured as part of the functions of an engine controller that performs various controls on an internal combustion engine. A crank angle sensor signal output by a crank angle sensor 2 at every predetermined crank angle is input to the restart control device 1. The crank angle sensor 2 is, for example, a general crank angle sensor that includes a disc-shaped signal plate provided at the end of the crankshaft and a pickup that detects the passage of protrusions formed at equal angular intervals on the outer periphery of the signal plate. For example, the crank angle sensor 2 is configured to output a pulse signal shaped into a rectangular wave at intervals of about 6 to 10° CA, that is, a crank angle sensor signal.

[0012] A starter motor 3 is connected to the restart control device 1 to crank the internal combustion engine during restart. The starter motor 3 in one embodiment is a typical starter motor in which a pinion moves axially and meshes with a ring gear of the internal combustion engine when driving starts. A starter permissible rotation speed range is determined in advance to suppress impact noise when the pinion meshes with the ring gear. When restarting the engine using the starter motor 3 while the rotation of the crankshaft has not completely stopped, the rotation speed of the internal combustion engine when the pinion begins to engage with the ring gear must be within the starter permissible rotation speed range. In one embodiment, the starter permissible rotation speed range is set to a range with an upper limit equal to a predetermined threshold value in the forward rotation direction (for example, approximately +100 to +200 rpm) and a lower limit of 0.

[0013] As shown in the figure, the restart control device 1 includes a rotation speed / crank angle calculation unit 11, a predicted time setting unit 12, and a starter drive determination unit 13. After an automatic stop due to idle stop, the rotation speed / crank angle calculation unit 11 calculates the rotation speed (rotational speed) and crank angle of the internal combustion engine based on the crank angle sensor signal for both forward and reverse rotation each time a crank angle sensor signal is input.

[0014] Based on the rotation speed and crank angle, the predicted time setting unit 12 calculates a predicted time required for the rotation speed of the internal combustion engine to reach the above-mentioned permissible starter rotation speed range at which the starter motor 3 can be driven, and updates the predicted time each time a crank angle sensor signal is input. In one embodiment, the predicted time setting unit 12 includes a pre-created map in which predicted times are assigned using the rotation speed and crank angle as parameters, and calculates the predicted time by referencing this map. The predicted time calculated in this manner is set in an appropriate timer, such as a subtraction timer or an addition timer. Then, each time a crank angle sensor signal is input, the newly calculated predicted time is set in the timer. In other words, the value of the predicted time set in the timer is updated each time a crank angle sensor signal is input.

[0015] When the predicted time has elapsed, the starter drive determination unit 13 determines whether or not a restart request has already been made, and starts driving the starter motor 3 if a restart request has already been made.

[0016] Strictly speaking, the predicted time is the time required until a command to start driving the starter motor 3 is issued, taking into consideration the starter actuation delay time from when a command to start driving the starter motor 3 is issued until the pinion plunges into the ring gear. In other words, assuming that the predicted time is Dt1 and the starter actuation delay time is Dt2, the predicted time Dt1 is set so that a command to start driving the starter motor 3 is issued when the predicted time Dt1 has elapsed, and the rotation speed of the internal combustion engine reaches the starter allowable rotation speed range at the time when the pinion plunges into the ring gear after the starter actuation delay time Dt2.

[0017] The map also assigns appropriate predicted time values ​​to the rotation speed (positive values ​​for forward rotation and negative values ​​for reverse rotation) and crank angle for both forward and reverse rotation. As described above, when the internal combustion engine automatically stops, the crankshaft rotates by inertia and, in the process of coming to a complete stop, the crankshaft may rotate in reverse due to the compression pressure in the cylinder and the valve spring reaction force. In such a reverse rotation, the predicted time (delay time taking into account the starter activation delay time described above) expected until the crankshaft reaches 0 rpm, the lower limit of the starter's allowable rotation speed range, is set based on the map.

[0018] 2 is a flowchart showing the flow of the restart control process of one embodiment. This process is repeatedly executed at predetermined time intervals after the start of idle stop. In the first step 1, it is determined whether the internal combustion engine has stopped. That is, it is determined whether the rotation of the crankshaft has completely stopped. If the answer is YES, the routine is terminated. Note that restart after the complete stop is performed according to another routine not shown.

[0019] If the crankshaft is rotating inertially, the process proceeds to step 2 and waits for input of a crank angle sensor signal. If input of a crank angle sensor signal is detected, the process proceeds from step 2 to step 3 and calculates the rotation speed and crank angle. Then, in the next step 4, the map described above is referenced to determine a predicted time, and in step 5, the value of this predicted time is set in a timer consisting of a down counter.

[0020] In the next step 6, it is determined whether the timer has reached 0. Since the result is NO the first time, the process proceeds from step 6 to step 7 to determine whether the next crank angle sensor signal has been input. If there is no input of a crank angle sensor signal, the timer is decremented in step 8 and the process returns to step 6. In other words, while the timer is not at 0, the processes of steps 6 to 8 are repeated until the next crank angle sensor signal is input, and the timer value gradually decreases. If the input of a crank angle sensor signal is detected in step 7 before the timer value reaches 0 (i.e., before the predicted time has elapsed), the process returns from step 7 to step 3, and the calculation of the rotation speed and crank angle (step 3), the calculation of the predicted time (step 4), and the setting of the timer (step 5) are performed again. In other words, the predicted time is updated each time a crank angle sensor signal is input, and the timer value is set to the new predicted time.

[0021] If it is determined in step 6 that the timer has reached 0 while the predicted time is being repeatedly updated, the process proceeds from step 6 to step 9, where it is determined whether or not a restart request has been made. If a restart request has already been made, the process proceeds from step 9 to step 10, where a drive signal for the starter motor 3 is output. This drive start causes the pinion to mesh with the ring gear when the rotation of the internal combustion engine enters the starter allowable rotation speed range, and cranking begins.

[0022] On the other hand, if the determination in step 9 is NO, that is, if there is still no restart request when the timer reaches 0, the process proceeds to step 11, where the timer value is reset to the initial value, and then the process returns to step 1. Then, when the next crank angle sensor signal is input, the process proceeds to step 3 and subsequent steps, and the above-mentioned processing is repeated.

[0023] 3 is a time chart showing an example of operation of the restart control described above. From top to bottom, the diagram shows (a) brake switch ON / OFF, (b) idle stop permission determination flag, (c) crank angle sensor signal input, (d) actual internal combustion engine speed, (e) timer value, and (f) starter motor drive command. For convenience, the crank angle sensor signals shown in section (c) are numbered P1 to P10. Also, section (d) shows an example of the starter permissible speed range ΔNeST, which is set with an upper limit set to a predetermined threshold value in the forward rotation direction (e.g., approximately +100 to +200 rpm) and a lower limit set to 0.

[0024] In this example time chart, when the accelerator pedal is released and the brake pedal is depressed to stop temporarily at an intersection, the vehicle speed drops to 0, and the idle stop permission determination flag is turned ON at time t1, causing the internal combustion engine to automatically stop. Furthermore, when the brake pedal is released at time t2, the idle stop permission determination flag is turned OFF. This constitutes a restart request.

[0025] After the idle stop permission determination flag is turned ON and fuel injection and ignition of the internal combustion engine are stopped, the crankshaft of the internal combustion engine rotates by inertia for a relatively short period of time, and the actual rotation speed gradually decreases as shown in (d). In this example, after the actual rotation speed reaches 0, it becomes a negative value again. In other words, the compression pressure in the cylinder and the valve spring reaction force cause the crankshaft to rotate in reverse, and after a short reverse rotation, the actual rotation speed returns to 0. As described above, the crank angle sensor signal shown in (c) is output at a predetermined crank angle interval of about 6 to 10° CA, and the lower the rotation speed of the internal combustion engine, the longer the time interval.

[0026] In the example of the time chart shown in the figure, when the first crank angle sensor signal P1 is input after the start of idle stop, the engine speed and crank angle are calculated, and a predicted time is determined based on these. The value of this predicted time is then set in the timer shown in column (e). Thereafter, the timer value gradually decreases as time passes, but because the next crank angle sensor signal P2 is input before the timer value reaches 0, the engine speed and crank angle and the predicted time are calculated again, and the timer value is updated based on this predicted time. Thereafter, each time a crank angle sensor signal P2, P3, P4, etc. is input, the predicted time is updated and a new timer is set.

[0027] In the illustrated example, the timer value set based on the crank angle sensor signal P7 becomes 0 at time t3. However, since there is no restart request at this time, the restart is not initiated and the timer value returns to its initial value. This initial timer value is not decremented until the next crank angle sensor signal is input. Note that a restart request is made at time t2, but at this time the crankshaft is rotating in reverse.

[0028] When the next crank angle sensor signal P8 is input, a predicted time is calculated based on this crank angle sensor signal P8, and the timer value is updated. The predicted time at this time corresponds to the reverse rotation and is the time required for the starter rotation speed to reach 0 rpm, which is the lower limit of the starter permissible rotation speed range ΔNeST.

[0029] In the illustrated example, the timer value set when the crank angle sensor signal P9 is input becomes 0 at time t4. At this time, a restart request has already occurred, so drive of the starter motor 3 begins at time t4. Therefore, after the starter operation delay time described above, the pinion meshes with the ring gear, and actual cranking begins. At the timing when the pinion meshes with the ring gear, the actual rotation speed of the internal combustion engine is within the starter permissible rotation speed range ΔNeST. In the illustrated example, the pinion meshes with the ring gear when the reverse rotation of the crankshaft is completed and the actual rotation speed reaches 0 rpm.

[0030] In the illustrated example, the timing of the restart request (time t2) is after the timing when the timer value first reaches 0 (time t3), so restart does not begin at time t3. However, if a restart request were made before time t3, the starter motor 3 would begin to be driven at this time t3.

[0031] In this way, in the above embodiment, if a restart request is made while the crankshaft is rotating inertially, restart by the starter motor 3 can be initiated before it is determined that the crankshaft is in a completely stopped state, thereby shortening the delay from, for example, timing t2 when the brake pedal is released until restart completion and starting. In particular, even if a restart request is made while the crankshaft is rotating in reverse, restart can be initiated at an earlier, more appropriate timing, just as when the crankshaft is rotating in forward direction.

[0032] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, the elapse of the predicted time is determined using a countdown timer, but the elapse of the predicted time may be determined using an countdown timer. Furthermore, the specific types of the starter motor and crank angle sensor are not limited to those in the above embodiment and may be other appropriate types. Furthermore, the permissible starter rotation speed range may be set to include a negative rotation speed range. [Explanation of symbols]

[0033] 1...Restart control device 2...Crank angle sensor 3...Starter motor 11...Crank angle calculation unit 12...Prediction time setting section 13...Starter drive determination unit

Claims

1. 1. A restart control method for an internal combustion engine, which automatically stops the internal combustion engine in accordance with predetermined idle stop conditions, and then restarts the engine using a starter motor when a restart request is made before rotation of a crankshaft has completely stopped, After the automatic stop, the rotation speed and crank angle of the internal combustion engine are calculated for both forward and reverse rotations each time a crank angle sensor signal is input, the crank angle sensor outputting the signal at every predetermined crank angle. Based on the rotation speed and crank angle, a predicted time is calculated for the rotation speed of the internal combustion engine to reach a predetermined permissible starter rotation speed range in which the starter motor can be driven, and the predicted time is updated each time the crank angle sensor signal is input. When this predicted time has elapsed, it is determined whether a restart request has already been made; If a restart request has already been made, the starter motor will begin to operate. A method for controlling restart of an internal combustion engine.

2. A map is created in advance in which predicted times are assigned using rotation speed and crank angle as parameters, Refer to this map to find the estimated time.

2. The restart control method for an internal combustion engine according to claim 1.

3. In the map, predicted times are assigned for forward and reverse rotation, with the rotation speed and crank angle as parameters.

3. The restart control method for an internal combustion engine according to claim 2.

4. The starter allowable rotation speed range is set with a predetermined threshold value in the forward rotation direction as an upper limit and 0 as a lower limit.

2. The restart control method for an internal combustion engine according to claim 1.

5. setting the value of the predicted time in a timer each time the crank angle sensor signal is input; When the value of the timer, which is decremented as time passes, reaches 0, it is determined whether a restart request has already been made.

2. The restart control method for an internal combustion engine according to claim 1.

6. When the timer value reaches 0, if there is no restart request, the timer value is set to the initial value.

6. The restart control method for an internal combustion engine according to claim 5.

7. The starter motor is a starter motor of a type in which a pinion moves axially and meshes with a ring gear of an internal combustion engine when driving is started.

2. The restart control method for an internal combustion engine according to claim 1.

8. The predicted time is set in consideration of a starter operation delay time from when a command to start driving the starter motor is issued until when the pinion enters the ring gear.

8. The restart control method for an internal combustion engine according to claim 7.

9. 1. A restart control device for an internal combustion engine that automatically stops the internal combustion engine in accordance with predetermined idle stop conditions, and then restarts the engine using a starter motor when a restart request is made before rotation of a crankshaft has completely stopped, a crank angle sensor that outputs a crank angle sensor signal at every predetermined crank angle in both forward and reverse directions; a rotation speed / crank angle calculation unit that calculates the rotation speed and crank angle of the internal combustion engine for both forward and reverse rotations each time the crank angle sensor signal is input after the automatic stop; a predicted time setting unit that calculates a predicted time required for the rotational speed of the internal combustion engine to reach a predetermined permissible starter rotational speed range that allows the starter motor to be driven, based on the rotational speed and crank angle, and updates the predicted time each time the crank angle sensor signal is input; a starter drive determination unit that determines whether a restart request has already been made when the predicted time has elapsed, and starts driving the starter motor if a restart request has already been made; A restart control device for an internal combustion engine comprising:

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