JP3564146B2 - Engine ignition timing learning control method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an ignition timing learning control method for an engine that performs learning control of an ignition timing according to whether knock has occurred.
[0002]
[Prior art]
Recently, technology for detecting knocking due to abnormal combustion of the engine and optimally controlling the ignition timing has been widely adopted.
[0003]
In this case, the engine knock often detects pressure vibration due to abnormal combustion of the air-fuel mixture as mechanical vibration using an acceleration sensor or the like attached to a cylinder head or a cylinder block. It becomes difficult to distinguish the component from the vibration component of the engine itself.
[0004]
Therefore, in an operation region where knock detection is difficult, the ignition timing is corrected based on a learning value learned in an operation region where knock detection is possible. For example, Japanese Patent Laid-Open No. 60-27782 discloses an engine ( A technique is disclosed in which the updating of the learning retard amount is stopped at the time of a transient transition of the state of the engine) to prevent unnecessary decrease in torque due to an abnormal increase in the learning retard amount.
[0005]
[Problems to be solved by the invention]
However, at the time of acceleration, the operating state of the engine is affected by the shift position (shift range) of the transmission of the vehicle. Therefore, it is difficult to accurately detect knocking even if acceleration is relatively moderate. Learning may not be possible. In addition, since the knock occurrence period is not constant, if the ignition timing learning is uniquely stopped, controllability may be deteriorated.
[0006]
The present invention has been made in view of the above circumstances, and it is possible to prevent deterioration in controllability by stopping ignition timing learning for a period according to the state of the engine during acceleration, and to perform stable ignition timing control. It is an object of the present invention to provide an ignition timing learning control method for an engine.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention providesThe ignition timing correction amount according to the presence or absence of knock is learned, and the ignition timing is controlled based on the learned ignition timing correction amount.At the same time, acceleration is determined, and during acceleration, learning of the ignition timing correction amount is prohibited for a predetermined number of ignitions.In the ignition timing learning control method of the engine,An ignition timing learning control for an engine of a vehicle equipped with an automatic transmission, wherein an acceleration determination level indicating an acceleration level is set based on a change in throttle opening, and it is determined that acceleration is large by comparing the acceleration determination level with the set value. At this time, the learning of the ignition timing correction amount is prohibited, and the number of ignitions that defines the learning prohibition period at this time is set to be higher in the case where the vehicle speed is higher than the set value than in the case where the vehicle speed is lower than the set value. , Set largeIt is characterized by doing.
[0009]
[Action]
According to the present invention, in the ignition timing learning control of an engine of a vehicle equipped with an automatic transmission, when learning of an ignition timing correction amount is prohibited during a predetermined number of ignitions during acceleration, an acceleration determination indicating a degree of acceleration by a change in a throttle opening is performed. Set the level. When it is determined that the acceleration is large by comparing the acceleration determination level with the set value, learning of the ignition timing correction amount is prohibited, and the number of ignitions that defines the learning prohibition period at this time is set to a value equal to or greater than the vehicle speed set value. When the vehicle speed is high, the speed is set to be higher than when the vehicle speed is lower than the set value.
[0011]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings show an embodiment of the present invention. FIG. 1 is a flowchart (part 1) of a learning procedure of a whole correction coefficient and a partial correction ignition timing, and FIG. 2 is a flowchart (part 2) of a learning procedure of a whole correction coefficient and a partial correction ignition timing. FIG. 3 is a flowchart (part 3) of a procedure for learning the whole correction coefficient and the partial correction ignition timing, FIG. 4 is a flowchart (part 1) of the acceleration determination procedure, FIG. 5 is a flowchart (part 2) of the acceleration determination procedure, and FIG. 7 is a flowchart of an ignition timing setting procedure (part 1), FIG. 8 is a flowchart of an ignition timing setting procedure (part 2), and FIG. 9 is a θ2 interrupt in the energization / ignition control procedure. 10 is a flowchart of the θ3 interrupt in the energization / ignition control procedure, and FIG. 11 is a flowchart showing a subroutine for learning the overall correction coefficient. 12 is a flowchart showing a subroutine for learning the whole correction coefficient (part 2), FIG. 13 is a flowchart showing a subroutine for learning the whole correction coefficient (part 3), and FIG. 15 is a flowchart showing a subroutine for learning partially corrected ignition timing (part 2), FIG. 16 is a flowchart showing a subroutine for learning partially corrected ignition timing (part 3), and FIG. FIG. 18 is a conceptual diagram of a partial correction table, FIG. 19 is a schematic diagram of an engine control system, FIG. 20 is a front view of a crank rotor and a crank angle sensor, and FIG. 21 is a cam rotor. FIG. 22 is a circuit configuration diagram of the control device, and FIG. 23 is an ignition timing diagram. Is a time chart showing a grayed.
[0012]
(Configuration of engine control system)
In FIG. 19, reference numeral 1 denotes an engine body, and in the figure, a horizontally opposed four-cylinder engine is shown. An intake manifold 3 communicates with each intake port 2 a formed in a cylinder head 2 of the engine body 1, a throttle chamber 5 communicates with the intake manifold 3 via an air chamber 4, and intake air flows upstream of the throttle chamber 5. An air cleaner 7 is attached via a pipe 6.
[0013]
Further, an intake air amount sensor (in the figure, a hot wire type air flow meter) 8 is interposed immediately downstream of the air cleaner 7 of the intake pipe 6, and a throttle valve 5a provided in the throttle chamber 5 is provided with a throttle valve 5a. A throttle opening sensor 9a and an idle switch 9b for detecting that the throttle valve is fully closed are connected in series.
[0014]
Further, an idle speed control valve (ISCV) 11 is interposed in a bypass passage 10 that connects the upstream side and the downstream side of the throttle valve 5a, and is located immediately upstream of each intake port 2a of each cylinder of the intake manifold 3. , An injector 12 is provided. Further, an ignition plug 13a whose tip is exposed to the combustion chamber is attached to each cylinder of the cylinder head 2, and an igniter 14 is connected to an ignition coil 13b connected to the ignition plug 13a.
[0015]
The injector 12 is connected to a fuel tank 16 via a fuel supply path 15, and an in-tank type fuel pump 17 is provided in the fuel tank 16. The fuel from the fuel pump 17 is pressure-fed to the injector 12 and the pressure regulator 19 through a fuel filter 18 interposed in the fuel supply path 15, and is returned from the pressure regulator 19 to the fuel tank 16 to a predetermined pressure. Regulated to pressure.
[0016]
A knock sensor 20 is attached to a cylinder block 1a of the engine body 1, and a coolant temperature sensor 21 faces a coolant passage (not shown) formed in the cylinder block 1a. An O2 sensor 23 faces a collecting portion of the exhaust manifold 22 communicating with the exhaust port 2b. Reference numeral 24 denotes a catalytic converter.
[0017]
A crank rotor 25 is axially mounted on a crankshaft 1b supported by the cylinder block 1a. An electromagnetic pickup or the like that detects a projection (or a slit) corresponding to a predetermined crank angle on the outer periphery of the crank rotor 25 is provided. And a cam angle sensor 28 for discriminating a cylinder, such as an electromagnetic pickup, is provided on a cam rotor 27 connected to the camshaft 1c of the cylinder head 2.
[0018]
As shown in FIG. 20, the crank rotor 25 has projections 25a, 25b, 25c formed on the outer periphery thereof, and these projections 25a, 25b, 25c are connected to the cylinders (# 1, # 2, # 3, # 3). 4) before compression top dead center (BTDC) θ1, θ2, θ3 (for example, θ1 = 97 °, θ2 = 65 °, θ3 = 10 °).
[0019]
That is, the engine rotational speed NE is calculated from the passage time between the protrusions 25a and 25b, and the protrusions 25b and 25c respectively indicate the reference crank angle at the time of setting the ignition timing and the fuel injection timing, and the reference crank angle indicating the fixed ignition timing. It becomes.
[0020]
As shown in FIG. 21, projections 27a, 27b and 27c for cylinder discrimination are formed on the outer periphery of the cam rotor 27. For example, the projections 27a are located after the compression top dead center of the # 3 and # 4 (ATDC). The protrusion 27b is formed of three protrusions, and the first protrusion is formed at the position of ATDC θ5 of the # 1 cylinder (for example, θ5 = 5 °). Further, the protrusion 27c is formed by two protrusions, and the first protrusion is formed at the position of ATDC θ6 (for example, θ6 = 20 °) of the # 2 cylinder.
[0021]
The crank angle sensor 26 and the cam angle sensor 28 are not limited to magnetic sensors such as an electromagnetic pickup, but may be optical sensors.
[0022]
(Circuit configuration of control device)
On the other hand, in FIG. 22, reference numeral 30 denotes a control device (ECU) including a microcomputer or the like. The ECU 30 includes a main computer 31 for performing ignition timing control, fuel injection control, and the like, and a dedicated sub-processor for performing knock detection processing. Two microcomputers with the computer 32 are configured as cores.
[0023]
The ECU 30 has a built-in constant voltage circuit 33 for supplying a stabilized voltage to each unit. The constant voltage circuit 33 is connected to a battery 35 directly and via a relay contact of an ECU relay 34. I have. A relay coil of the ECU relay 34 is connected to the battery 35 via a key switch 36, and the fuel pump 17 is connected to the battery 35 via a relay contact of a fuel pump relay 37.
[0024]
The main computer 31 includes a main CPU 38, a ROM 39, a RAM 40, a backup RAM 40a, a timer 41, a serial interface (SCI) 42, and an I / O interface 43 connected to each other via a bus line 44. Are mounted in the ECU 30 as one LSI chip, for example.
[0025]
An input port of the I / O interface 43 is connected to an intake air amount sensor 8, a throttle opening sensor 9a, a cooling water temperature sensor 21, an O2 sensor 23, and a vehicle speed sensor 60 via an A / D converter 45. At the same time, the starter switch 46, the idle switch 9b, the crank angle sensor 26, and the cam angle sensor 28 are connected, and the battery 35 is connected to monitor the battery voltage.
[0026]
The igniter 14 is connected to the output port of the I / O interface 43, and the ISCV 11, the injector 12, and the relay coil of the fuel pump relay 37 are connected via the drive circuit 47.
[0027]
On the other hand, the sub-computer 32 is configured by connecting a sub-CPU 48, a ROM 49, a RAM 50, a timer 51, an SCI 52, and an I / O interface 53 to each other via a bus line 54. For example, it is mounted in the ECU 30 as one LSI chip.
[0028]
The crank angle sensor 26 and the cam angle sensor 28 are connected to the input ports of the I / O interface 53, and the knock sensor 20 is connected via an amplifier 55, a frequency filter 56, and an A / D converter 57. ing.
[0029]
The knock sensor 20 is, for example, a resonance type knock sensor including a vibrator having substantially the same natural frequency as the knock vibration and a piezoelectric element that detects a vibration acceleration of the vibrator and converts the vibration acceleration into an electric signal. Vibration transmitted to the cylinder block 1a is detected by the combustion pressure wave during the explosion stroke of the engine, and the vibration waveform is output as a detection signal.
[0030]
After the detection signal of the knock sensor 20 is amplified to a predetermined level by the amplifier 55, necessary frequency components are extracted by the frequency filter 56, and are converted from analog data to digital data by the A / D converter 57. .
[0031]
The main computer 31 and the sub-computer 32 are connected by a serial line via SCIs 42 and 52, and the output port of the I / O interface 53 of the sub-computer 32 is connected to the I / O of the main computer 31. It is connected to the input port of the O interface 43.
[0032]
The main computer 31 sets the ignition timing and the like based on the crank pulse from the crank angle sensor 26, determines the target cylinder to be ignited based on the cam pulse from the cam angle sensor 28, and sets a predetermined ignition timing. When it reaches, the ignition signal is output to the igniter 14 to ignite the corresponding cylinder.
[0033]
On the other hand, the sub-computer 32 sets a sample section of the detection signal from the knock sensor 20 based on the engine speed and the engine load, and performs high-speed A / D conversion of the detection signal from the knock sensor 20 in this sample section. Then, the vibration waveform is faithfully converted into digital data, and it is determined whether or not knock has occurred.
[0034]
The knock determination data indicating whether or not knock has occurred is output to the I / O interface 53 of the sub-computer 32. In the case of knock occurrence, the knock is transmitted from the sub-computer 32 to the main computer 31 via a serial line via the SCIs 52 and 42. The data is read. The main computer 31 immediately delays the ignition timing of the corresponding cylinder based on the knock data to avoid knocking.
[0035]
When the ignition timing is controlled by the main computer 31, learning control is performed on two ignition timing tables, a basic advance value table for low octane fuel and an advanced value table for high octane fuel, and this learning control is performed. , Is stopped during acceleration. Hereinafter, the operation related to the ignition timing learning control will be described.
[0036]
(Cylinder discrimination / engine speed calculation procedure)
FIG. 6 shows a routine of cylinder discrimination and engine speed calculation which is interrupted by the input of a crank pulse from the crank angle sensor 26. First, in step S101, based on the output of the cam angle sensor 28, the ignition target cylinder of #i Is determined, the crank pulse is identified in step S102.
[0037]
As shown in the time chart of FIG. 23, for example, when a cam pulse of θ5 (projection 27b) is output from the cam angle sensor 28, the next compression top dead center is # 3 cylinder, and this # 3 cylinder is ignited. It can be determined that the target cylinder (the # 4 cylinder is the fuel injection target cylinder).
[0038]
If a cam pulse of θ4 (projection 27a) is output after the cam pulse of θ5, the next compression top dead center is cylinder # 2, and this cylinder # 2 is an ignition target cylinder (# 1 is a fuel injection target cylinder). Cylinder).
[0039]
Similarly, the compression top dead center after the output of the cam pulse of θ6 (projection 27c) is # 4 cylinder, and this # 4 cylinder is the ignition target cylinder (# 3 cylinder is the fuel injection target cylinder). Further, when the cam pulse of θ4 (projection 27a) is output after the cam pulse of θ6, the compression top dead center is the # 1 cylinder, and the # 1 cylinder is the cylinder to be ignited (the # 2 cylinder is the fuel injection target). Cylinder).
[0040]
Further, after the cam pulse is output from the cam angle sensor 28, the crank pulse output from the crank angle sensor 26 indicates a reference crank angle (θ1) for calculating a cycle (rotation speed), and the next crank pulse is It can be determined that it indicates the reference crank angle (θ2) when setting the ignition timing and the fuel injection start timing of the corresponding cylinder.
[0041]
That is, in the four-stroke four-cylinder engine of the present embodiment, the combustion stroke is in the order of # 1 → # 3 → # 2 → # 4, and assuming that the cylinder to be ignited of the #i cylinder is the # 1 cylinder, The fuel injection target cylinder #i (+2) is the # 2 cylinder, and the next fuel injection target cylinder #i (+2) is the # 4 cylinder. Then, ignition is performed in the order of cylinders # 1, # 3, # 2, and # 4, and fuel injection is performed once for each cylinder at 720 ° C. (two engine revolutions).
[0042]
Then, in step S103, for example, the input interval time (cycle) Tθ12 of the BTDC θ1 and θ2 crank pulses output from the crank angle sensor 26 is measured, and in step S104, the engine speed NE is calculated from the input interval time Tθ12. Then, the data is stored as the rotation speed data at a predetermined address in the RAM 40, and the routine exits.
[0043]
(Ignition timing setting procedure)
On the other hand, the ignition timing is set in the interrupt routine of FIGS. 7 and 8 that is executed every predetermined time. In this ignition timing setting routine, first, in steps S201 and S202, whether or not the starter switch 46 is ON, and whether or not the engine speed NE has reached the complete explosion speed NESET (for example, NESET = 400 rpm). Is determined.
[0044]
When the starter switch 46 is ON when the engine is started, or when NE ≦ NESET, the flow branches from step S201 or step S202 to step S216 to start the engine and determine whether the engine is running at an extremely low speed. The rotation flag FLAGST is set (FLAGST ← 1), and the routine exits.
[0045]
On the other hand, after cranking the engine by turning on the starter switch 46, when the starter switch 46 is turned off and NE> NESET, and the engine completely explodes, the process proceeds from steps S201 and S202 to step S203, and when starting, extremely low The rotation determination flag FLAGST is cleared (FLAGST ← 0), and in step S204, a water temperature correction value ADVTW (angle data) is set based on the cooling water temperature TW.
[0046]
Next, the process proceeds to step S205, and based on the engine speed NE and the basic fuel injection amount TP as the engine load, the partial correction ignition timing ADVPRT is set with reference to the partial correction table TBADVPRT. The partial correction table TBADVPRT stores partial correction ignition timing ADVPRT for performing partial correction for each operation region in the backup RAM 40a. As shown in FIG. 18, the engine speed NE, the basic fuel injection amount The partial correction ignition timing ADVPRT is stored for each area specified using TP as a parameter.
[0047]
The above-described basic fuel injection amount TP is an example of the engine load, and the fuel injection amount or the intake air amount per stroke may be used.
[0048]
In step S206, based on the engine speed NE and the basic fuel injection amount TP, the basic advance value IGREG is set by referring to the basic advance value table with interpolation calculation. The basic advance value table uses the ignition timing at the knock limit capable of suppressing knocking within an allowable range when a low octane number fuel such as regular gasoline is used as the basic advance value, and sets the engine speed NE, The fuel pulse width TP is obtained as a parameter in advance by an experiment or the like and stored in the ROM 39, and is configured as, for example, a three-dimensional table of a 16 × 16 grid.
[0049]
Thereafter, when the process proceeds to step S207, the overall correction coefficient TCMP stored in the backup RAM 40a is read, and in step S208, the high octane fuel advance value table is interpolated based on the engine speed NE and the basic fuel injection amount TP. A high octane fuel advance angle value IGMBT is set with reference to FIG.
[0050]
The advance value table for high octane fuel has the ignition timing at which the maximum allowable torque that can be exhibited when using high octane fuel with high knock resistance, such as premium gasoline, is determined by the engine speed NE, The fuel pulse width TP is obtained as a parameter in advance by an experiment or the like, and is stored in the ROM 39 as a three-dimensional table of, for example, a 16 × 16 grid.
[0051]
Next, proceeding to step S209, the basic advance value IGREG set in step S206 and the value obtained by multiplying the high octane fuel advance value IGMBT set in step S208 by the overall correction coefficient TCMP read in step S207 are used. To calculate the overall corrected ignition timing (angle data in units of ° CA) ADVTOT (ADVTOT ← IGREG + TCMP × IGMBT).
[0052]
Then, the process proceeds to step S210, where the control advance angle ADV is calculated by adding the partial correction ignition timing ADVPRT and the water temperature correction value ADVTW to the overall correction ignition timing ADVTOT calculated in step S209 (ADV ← ADVTOT + ADVPRT + ADVTW), and in step S211. Then, the ignition timing based on the control advance angle ADV based on the θ2 pulse, that is, the ignition timing TADV obtained by converting the angle into time data is set (TADV ← Tθ12 × (θ2−ADV) / θ12). Here, θ12 is an angle difference corresponding to the θ1 crank pulse and the θ2 crank pulse (for example, when θ1 = 97 ° CA and θ2 = 65 ° CA, θ12 = 32 ° CA).
[0053]
Next, in step S212, the basic energizing time DWLB is set by referring to the basic energizing time table with the interpolation calculation based on the battery voltage, and in step S213, the rotation correction table is interpolated based on the engine speed NE. To set the rotation correction KDWLN. The basic energization time DWLB is set shorter as the battery voltage is higher, and the rotation correction KDWLN is set smaller as the engine speed NE is higher.
[0054]
Then, proceeding to step S214, when the energization time DWL is calculated by multiplying the basic energization time DWLB by the rotation correction KDWLN (DWL ← DWLB × KDWLN), in step S215, the energization start time based on the θ2 crank pulse, that is, energization start The timing TDWL is set (TDWL ← TADV-DWL) and the process exits.
[0055]
With respect to the ignition timing set in this ignition timing setting routine, the routine of the energization / ignition control procedure shown in FIGS. 9 and 10 is started by the θ2 and θ3 crank pulse interruption, and the dwell (energization) and Perform dwell cut (ignition).
[0056]
In the interruption by the θ2 crank pulse shown in FIG. 9, in step S301, the value of the start-time / extremely low-speed discrimination flag FLAGST is referred to, and FLAGST = 1, that is, the process branches to step S302 at the time of start-up or at extremely low speed. The dwell of the cylinder #i to be ignited is started to exit the routine, and FLAGST = 0, that is, at normal time, the process proceeds to step S303, and the counting of the dwell set timer TIM1 and the ignition set timer TIM2 is started.
[0057]
Next, when the routine proceeds to step S304, a loop for determining whether or not the count value of the dwell set timer TIM1 has reached the energization start timing TDWL. When the energization start timing TDWL has been reached, the routine proceeds to step S305 and the ignition target cylinder # The dwell of i is started, the dwell set timer TIM1 is cleared in step S306 (TIM1 ← 0), and in step S307, it is determined whether or not the count value of the ignition set timer TIM2 has reached the ignition timing TADV.
[0058]
When the count value of the ignition set timer TIM2 reaches the ignition timing TADV in step S307, the process proceeds to step S308, in which dwell cut, that is, ignition is performed on the cylinder #i to be ignited. In step S309, the ignition set timer TIM2 is reset. Clear (TIM2 ← 0) and exit the routine.
[0059]
Next, when the crank pulse of θ3 is input, the interruption routine of FIG. 10 is started, and in step S401, the value of the start-time / extremely-low-speed discrimination flag FLAGST is referred to, and FLAGST = 0, that is, at the normal time, The process exits the routine as it is, and when FLAGST = 1, that is, at the time of starting or extremely low rotation, in step S402, the cylinder to be ignited #i is cut off, and the routine exits.
[0060]
That is, as shown in FIG. 23, at the time of starting or extremely low rotation, the dwell of the corresponding cylinder #i is started immediately after the θ2 (for example, BTDC 65 °) crank pulse is input, and the θ3 (for example, BTDC 10 °) crank is started. The ignition timing is a fixed ignition timing for igniting with a pulse. On the other hand, in normal times, the dwell is started at the energization start timing TDWL after a lapse of a predetermined time from the reference with reference to the θ2 crank pulse, and the ignition is performed at the ignition timing TADV. .
[0061]
In the normal ignition timing control, the value of the ignition timing required by the current engine is determined by two ignition timing tables: a basic advance value table for low octane fuel and an advanced value table for high octane fuel. An overall correction for determining the position is performed, and a partial correction for correcting the value of the ignition timing based on whether knock has occurred or not for each region using the engine speed and the engine load as parameters. Hereinafter, the procedure will be described.
[0062]
1 to 3 show a procedure for learning the whole correction coefficient and the partly corrected ignition timing. In the four-cylinder engine according to the present embodiment, the procedure is executed for ignition every 1/2 engine revolution (for a 6-cylinder engine, the engine 1 / Every three rotations).
[0063]
First, learning conditions are determined in steps S501, S502, and 503. That is, in a step S501, it is determined whether or not the start-up / extremely low rotation time determination flag FLAGST is “0”. Whether the cooling water temperature TW is equal to or higher than the warm-up completion temperature TWSET is determined in step S503.
[0064]
If there is a condition that is not satisfied in steps S501, S502, and S503, the routine exits from that step. On the other hand, FLAGST = 0 in step S501, which is normal time, and knock sensor 20, ISCV11 in step S502. If the sensors and actuators that affect the ignition timing are normal and the cooling water temperature TW is equal to or higher than the warm-up completion temperature TWSET in step S503, it is determined that the learning condition is satisfied, and the process proceeds to step S504. It is determined whether or not the value of the learning stop ignition number COUNTACC indicating the number of ignitions at which the timing learning is stopped is 0.
[0065]
If COUNTACC ≠ 0 in step S504, the process jumps to step S509, counts down the learning suspension ignition count COUNTACC, and exits the (COUNTACC ← COUNTACC-1) routine. If COUNTACC = 0, in step S505, the acceleration determination level is set. LEVACC (set in an acceleration determination routine to be described later, the smaller the value, the greater the acceleration) is compared with a set value ACCDVG (for example, ACCDVG = 4).
[0066]
As a result, when LEVACC ≦ ACCDVG in the above step S505, the process proceeds to step S506, where it is determined whether or not the vehicle speed VSP is less than a set value VSPACT (for example, VSPACT = 20 to 60 km). In step S507, the set value ACTN (for example, 30) is set in the learning suspension ignition count COUNTACC (COUNTACC ← ACCTN), the countdown is performed in step S509, and the routine is exited. When VSP ≧ VSPACT, learning is performed in step S508. The set value ACCNTV (for example, 150 times) is set in the number of times of suspension ignition COUNTACC (COUNTACC ← ACCNTV), the countdown is performed in step S509, and the routine exits.
[0067]
That is, at the time of acceleration, accurate knock detection is difficult, and accurate ignition timing learning cannot be expected. In addition, since the acceleration state is short, there is no problem even if learning is stopped. When the value is equal to or less than the set value ACCDVG, the acceleration is determined and the learning is stopped during the predetermined number of ignitions.
[0068]
At this time, in a vehicle equipped with an automatic transmission, when the vehicle speed VSP is high (VSP ≧ VSPACT), a kick-down occurs, and it takes time for the engine speed to rapidly change and stabilize. If it is low (VSP <VSPACT), kickdown does not occur and the change in engine speed is relatively small. Therefore, when learning is stopped, if VSP ≧ VSPACT, the number of ignitions at which learning is stopped is made larger than in the case where VSP <VSPACT.
[0069]
On the other hand, if LEVACC> ACCDVG in step S505, the process branches from step S505 to step S510 and thereafter to perform learning. The learning procedure will be described below. In step S510, the value of the overall correction end flag FLAGTCMP is read from a predetermined address in the backup RAM 40a, and it is determined whether or not the overall correction has been completed.
[0070]
When FLAGTCMP = 0, that is, when the overall correction has not been completed, the process proceeds from step S510 to step S511, in which the knock-free duration timer TIM3 that counts the duration of the knock-free state is cleared (TIM3 ← 0). In step S512, the subroutine for learning the overall correction coefficient is called to learn the overall correction coefficient TCMP, and the routine ends.
[0071]
On the other hand, when FLAGTCMP = 1 in step S510, that is, when the overall correction has been completed, the process branches from step S510 to step S513 and thereafter. Then, the limit count value COUNTTCMP for counting the state where the total correction coefficient TCMP has reached the upper and lower limits and the knock value count value COUNTNK for counting the state where no knock has occurred are cleared (COUNTTCMP ← 0, COUNTNK ← 0). ).
[0072]
Thereafter, in step S515, the subroutine for learning the partially corrected ignition timing is called to learn the partially corrected ignition timing ADVPRT. Then, as a result of the partial correction, the entire correction becomes inappropriate, and the whole correction is returned to perform the whole correction again. It is determined in steps S516 to S520 whether or not the condition is satisfied.
[0073]
That is, in step S516, it is determined whether or not the learned partial correction ignition timing ADVPRT in the operation region is a negative value (whether or not retard), and in step S517, the overall correction coefficient TCMP is set to the set value TCLOW (where 1 .0> TCLOW> 0) is determined, and if ADVPRT <0 (retard) and TCMP ≧ TCLOW, the process proceeds to step S518. Otherwise, the routine exits.
[0074]
In step S518, a high octane fuel advance value IGMBT is set from the high octane fuel advance value table based on the engine speed NE and the basic fuel injection amount TP, and the set value for the high octane fuel advance value IGMBT is set. In step S519, the value IGMBT × PCMPL multiplied by PCMPL (for example, PCMPL = 0.1 to 0.4) is compared with the absolute value | ADVPRT | of the partial correction ignition timing ADVPRT in step S519.
[0075]
When | ADVPRT | <IGMBT × PCMPL, the routine exits from step S519, and when | ADVPRT | ≧ IGMBT × PCMPL, the routine proceeds from step S519 to step S520, where the engine speed NE and the basic fuel injection amount TP are set. It is determined whether or not it is within the range (NESETL3 ≦ NE ≦ NESETH3 and TPSETL3 ≦ TP ≦ TPSETH3). If it is not within the set range, the routine exits. If it is within the set range, the overall correction end flag is set at step S521. FLAGTCMP is cleared (FLAGTCMP ← 0), and the routine exits.
[0076]
The acceleration determination level LEVACC in the above-described step S505 is set in an acceleration determination routine (FIGS. 4 and 5) executed every predetermined time. In this acceleration determination routine, first, in step S601, the throttle opening θ from the throttle opening sensor 9a is read, and in step S602, the throttle opening θ MEMO during the previous execution of the routine is read from the RAM 40.
[0077]
Next, the routine proceeds to step S603, where the throttle opening change d (θ−θ MEMO) / dt is calculated from the current throttle opening θ and the previous throttle opening θ MEMO, and the throttle opening change d (θ−θ) after step S604. The acceleration determination level LEVACC is determined based on a magnitude comparison result of the set values SET0, SET1, SET2, SET3, SET4, SET5, and SET6 of (θMEMO) / dt (SET0> SET1> SET2> SET3> SET4> SET5> SET6).
[0078]
That is, when d (θ−θMEMO) / dt> SET0 in step S604, the process proceeds to step S605, in which the acceleration determination level LEVACC is set to 0 (LEVACC ← 0) and stored in the RAM 40, and d (θ−θMEMO) / dt If .ltoreq.SET0, the flow branches to step S606 to compare the throttle opening change d (.theta .-. Theta.MEMO) / dt with the set value SET1.
[0079]
If d (θ−θMEMO) / dt> SET1 as a result of the comparison in step S606, in step S607, the acceleration determination level LEVACC is set to 1 (LEVACC ← 1) and stored in the RAM 40, and d (θ−θMEMO) / dt If ≤ SET1, the flow branches to step S608 and subsequent steps.
[0080]
Then, similarly, the throttle opening change d (θ-θMEMO) / dt and the set values SET2, SET3, SET4, SET5, SET6 are sequentially compared in the same manner, and the throttle opening change d (θ-θMEMO) / dt. Is larger than the set value, in one of the steps S609, S611, S613, S615, and S617, the acceleration determination level LEVACC is set to 2, 3, 4, 5, or 6, (LEVACC ← 2, LEVACC ← 3, LEVACC). ← 4, LEVACC ← 5, or LEVAC ← 6) Store in the RAM 40, and finally, in step S616, when d (θ−θMEMO) / dt ≦ SET6, proceed to step S618 to set the acceleration determination level LEVACC. 7 is stored in the RAM 40 (LEVACC ← 7).
[0081]
Thereafter, when the acceleration determination level LEVACC is determined, the process proceeds to step S619, where the throttle opening θ read this time is stored as a throttle opening θ MEMO at a predetermined address of the RAM 40, and the routine exits.
[0082]
The subroutines for learning the whole correction coefficient and the partial correction ignition timing in steps S512 and S515 of the above-described whole correction coefficient and partial correction ignition timing learning routine are shown in FIGS. 11 to 13 and FIGS. 14 to 17, respectively. Is shown.
[0083]
In the subroutine for learning the entire correction coefficient shown in FIGS. 11 to 13, whether the engine speed NE and the basic fuel injection amount TP are within the learning range (NESETL1 ≦ NE ≦ NESETH1 and TPSETL1 ≦ TP ≦ TPSETH1) in step S701. If it is not in the learning region, the process exits the routine. If it is in the learning region, it is determined in step S702 whether or not knocking has occurred. If knocking has occurred, the process proceeds to step S703 and subsequent steps. If no occurrence has occurred, the flow branches to step S713 and subsequent steps.
[0084]
First, the case where knock has occurred will be described. In step S703, the value of the overall correction knock presence / absence change determination flag FLAGNK1 for determining the change of presence / absence of knock is referred to, and when FLAGNK1 = 1, that is, If the knocking state is present and the knocking presence state has not changed, the process jumps to step S705. If FLAGNK1 = 0, that is, if there was no knocking last time and this time knocking occurred, the process proceeds to step S705. In step S704, the variation ΔTCMP for updating the overall correction coefficient TCMP is updated to の of the previous value (ΔTCMP ← ΔTCMP / 2), and the process proceeds to step S705.
[0085]
In step S705, the total correction coefficient TCMP up to the previous time is updated by subtracting the variation ΔTCMP (TCMP ← TCMP−ΔTCMP), and in step S706, the partial correction table TBADVPRT is initialized. That is, when knocking has occurred, the overall correction coefficient TCMP is updated to the retard side every 1/2 engine revolution, and the table values of the partial correction table TBADVPRT are all set to "0" with the update of the overall correction coefficient TCMP. It is cleared and initialized.
[0086]
When the backup power is turned off and the data in the backup RAM 40a is destroyed, the partial correction table TBADVPRT is cleared and initialized when the power is turned on again.
[0087]
Thereafter, when the flow proceeds to step S707, it is determined whether or not the overall correction coefficient TCMP has been updated to the retard side and has become a negative value. When TCMP ≦ 0, the overall correction coefficient TCMP is set to “0” in step S708. (TCMP ← 0) and the retarding is limited, the limit count value COUNTTCMP for counting the state where the total correction coefficient TCMP has reached the upper and lower limits is counted up in step S709 (COUNTTCMP ← COUNTTCMP + 1), and step S711 is performed. Proceed to.
[0088]
If TCMP> 0 in the above step S707, the limit count value COUNTTCMP is cleared in step S709 (COUNTTCMP ← 0). In step S711, the overall correction knock presence / absence change determination flag FLAGNK1 is set (FLAGNK1 ← 1). In step S712, the knock occurrence non-occurrence count value COUNTNK for counting the state where no knock occurs is cleared (COUNTNK ← 0), and the flow proceeds to step S725.
[0089]
On the other hand, if no knock has occurred in step S702, the value of the overall correction knock presence / absence change determination flag FLAGNK1 is referred to in step S713, and when FLAGNK1 = 1, that is, from the previous knock occurrence state, the knock has occurred. When the state has changed to the absence state, the process proceeds to step S714, in which the change amount ΔTCMP is updated to １ ／ of the previous value (ΔTCMP ← ΔTCMP / 2), and in step S724, the overall correction knock presence / absence change determination flag FLAGNK1 is cleared. (FLAGNK1 ← 0) and the process proceeds to step S725.
[0090]
If FLAGNK1 = 0 in step S713 and the knock-free state continues from the previous time, the process proceeds from step S713 to step S715 to count up the knock-free count value COUNTNK (COUNTNK). ← COUNTNK + 1), and in a step S716, it is determined whether or not the knock occurrence non-occurrence count value COUNTNK is equal to or larger than the set value CTOTJD.
[0091]
If COUNTNK <CTOTJD in step S716, the process branches to step S724, and if COUNTNK ≧ CTOTJD, that is, if knock has not occurred by the set number of ignitions, the process proceeds to step S717 and continues until the previous time. The amount of change ΔTCMP is added to the total correction coefficient TCMP of (1) to update the value on the advance side (TCMP ← TCMP + ΔTCMP), and in step S718, the partial correction table TBADVPRT is initialized.
[0092]
Next, the process proceeds to step S719, where it is determined whether or not the total correction coefficient TCMP has become 1.0 or more by updating to the advance side. When TCMP ≧ 1.0, in step S720, the total correction coefficient TCMP is set to 1 .0 (TCMP ← 1.0) and the advance limit is performed, the limit count value COUNTTCMP is counted up in step S721 (COUNTTCMP ← COUNTTCMP + 1). If TCMP <1.0, the limit count value is counted in step S722. Clear the value COUNTTCMP (COUNTTCMP ← 0).
[0093]
Next, when the process proceeds from step S721 or step S722 to step S723, the knock occurrence-free count value COUNTNK is cleared (COUNTNK ← 0), and in step S724, the overall correction knock presence / absence change determination flag FLAGNK1 is cleared (FLAGNK1 ← 0). Then, in step S725, the variation ΔTCMP is compared with the set value DTCMP2 (for example, 1/16), and in step S726, the limit count value COUNTTCMP is compared with the set value NTCMP.
[0094]
If the conditions of ΔTCMP ≦ DTCMP2 or COUNTTCMP ≧ NTCMP are not satisfied in steps S725 and S726, in step S727, the overall correction end flag FLAGTCMP is cleared and the routine exits (FLAGTCMP ← 0), and the condition becomes 1 If at least one is satisfied, that is, if the change amount ΔTCMP is equal to or less than the set value DTCMP2, or if the state in which the total correction coefficient TCMP is at the upper and lower limits has continued for a set number of times, the overall correction end flag FLAGTCMP is set in step S728. Then, the (FLAGTCMP ← 1) routine is exited, and when the routine of the learning procedure of the overall correction coefficient and the partial correction ignition timing described above is started next time, the entire correction is terminated and the process is shifted to the partial correction.
[0095]
The overall correction coefficient TCMP, the change amount ΔTCMP, and the overall correction end flag FLAGTCMP are stored in the backup RAM 40a, and when the backup power is turned off by removing the battery 35 or the like, the data in the backup RAM 40a is destroyed. Are initially set to initial values when the power is turned on again (TCMP ← TCMPINI (for example,）), ΔTCMP ← ΔTCMPINI (for example, ４), FLAGTCMP ← 0).
In the subroutine for learning the partial correction ignition timing shown in FIGS. 14 to 17, in step S801, the engine speed NE and the basic fuel injection amount TP are set within the range of the partial correction table TBADVPRT (NE0 ≦ NE ≦ NEN and TP0). ≤TP≤TPN), the routine exits if it is not in the area, and if it is in the area, it is determined in step S802 whether knock has occurred.
[0096]
If knock has occurred, the process proceeds from step S802 to step S803, in which a knock-free duration timer TIM3 for counting the duration of the absence of knock is cleared (TIM3 ← 0), and in step S804, the engine is stopped. Based on the rotational speed NE and the basic fuel injection amount TP, the partial correction ignition timing ADVPRT is set with reference to the partial correction table TBADVPRT.
[0097]
Next, the process proceeds to step S805, in which the partial correction ignition timing ADVPRT set in step S804 is set to the old table value (ADVPRT) OLD ((ADVPRT) OLD ← ADVPRT), and in step S806, the set value is calculated from the old table value (ADVPRT) OLD. By subtracting DRETP to obtain a new table value (ADVPRT) NEW ((ADVPRT) NEW ← (ADVPRT) OLD-DRETP), the retard is set by the set value DRETP each time knock occurs once, and the process proceeds to step S807. .
[0098]
In step S807, the new table value (ADVPRT) NEW is compared with the retard limit value LWLMTP. When (ADVPRT) NEW> LWLMTP, the process jumps to step S809. On the other hand, when (ADVPRT) NEW ≦ LWLMTP, the process proceeds to step S808. The new table value (ADVPRT) NEW is fixed to the retardation limit value LWLMTP ((ADVPRT) NEW ← LWLMTP), and the process proceeds to step S809 to prevent the retardation beyond the limit value.
[0099]
In step S809, the partial correction ignition timing ADVPRT in the corresponding area ADDRESS of the partial correction table TBADVPRT is updated with the new table value (ADVPRT) NEW (ADVPRT ← (ADVPRT) NEW), and in step S810, it is determined whether or not knocking has occurred. The flag FLAGNK2 for setting the partial correction knock presence / absence change is set for this purpose (FLAGNK2 ← 1), and the routine exits.
[0100]
On the other hand, if no knock has occurred in step S802, the process branches from step S802 to step S811 to refer to the value of the partial correction knock presence / absence change determination flag FLAGNK2, and when FLAGNK2 = 1, that is, When the state has changed from the occurrence state to the no knock state, the process jumps to step S832 to start the no-knock duration timer TIM3. In step S833, the partial correction knock presence / absence change determination flag FLAGNK2 is cleared (FLAGNK2 ← 0) Exit the routine.
[0101]
When the partial correction knock presence / absence change determination flag FLAGNK2 is FLAGNK2 = 0, that is, when no knock occurs during the previous execution of the routine, the process proceeds from step S811 to step S812, where the engine speed NE and the basic fuel injection amount TP are set. The area ADDRESS in the partial correction table TBADVPRT is specified based on the above, and in step S813, the area ADDRESS is set as a new area (ADDRESS) NEW ((ADDRESS) NEW ← ADDRESS).
[0102]
Then, it is determined in step S814 whether or not the new area (ADDRESS) NEW at the time of execution of the current routine is the same as the previous area (ADDRESS) OLD, and the new area (ADDRESS) NEW is set to the old area at the time of execution of the previous routine. If it is different from (ADDRESS) OLD, the process branches from step S814 to step S830 to clear the knock-free duration timer TIM3 (TIM3 ← 0), and in step S831, the new area (ADDRESS) NEW is replaced with the old area (ADDRESS). As OLD ((ADDRESS) OLD ← (ADDRESS) NEW), the routine exits through the above-described steps S832 and S833.
[0103]
On the other hand, if the new area (ADDRESS) NEW at the time of executing the current routine is the same as the old area (ADDRESS) OLD at the time of executing the previous routine, the process proceeds from step S814 to step S815, where the new area (ADDRESS) NEW is set. The old area (ADDRESS) OLD is set ((ADDRESS) OLD ← (ADDRESS) NEW), and in step S816, it is determined whether or not the time measured by the knock-free duration timer TIM3 has exceeded a set time TIMPRT.
[0104]
In step S816, when the timer of the knock-free duration timer TIM3 does not exceed the set time TIMPRT, the process exits the routine through the above-described step S833, and when the timer of the knock-free duration timer TIM3 exceeds the set time TIMPRT. In step S817, the knock-free duration timer TIM3 is cleared (TIM3 ← 0), and the flow advances to step S818 to read the partial correction ignition timing ADVPRT from the corresponding area ADDRESS of the partial correction table TBADVPRT.
[0105]
Thereafter, the process proceeds to step S819, where the read partial correction ignition timing ADVPRT is set to the old table value (ADVPRT) OLD ((ADVPRT) OLD ← ADVPRT), and in step S820, the set value DADVP is added to the old table value (ADVPRT) OLD. By setting the new table value (ADVPRT) NEW ((ADVPRT) NEW ← (ADVPRT) OLD + DADVP), if no knock occurs in the same operation region, the set value DADVP is advanced by the set value DIMPVP for each set time TIMPRT. Proceed to step S821.
[0106]
In step S821, based on the engine speed NE and the basic fuel injection amount TP, the high octane fuel advance value IGMBT is set with reference to the high octane fuel advance value table. In step S822, the overall correction coefficient TCMP is set. Read from backup RAM 40a.
[0107]
Next, in step S823, the value obtained by multiplying the high octane fuel advance value IGMBT by the difference (1-TCMP) from the upper limit of the overall correction coefficient TCMP is set as the partial correction ignition timing limit value ADVPRTLIM (ADVPRTLIM ← IGMBT × ( 1-TCMP)), and the advance of the new table value (ADVPRT) NEW is limited to a smaller value of the set value UPLMTP and the partial correction ignition timing limit value ADVPRTLIM in step S824 and thereafter.
[0108]
That is, in step S824, the partial correction ignition timing limit value ADVPRTLIM is compared with the set value UPLMTP. When UPLMTP ≦ ADVPRTLIM, the process proceeds from step S824 to step S825, and the new table value (ADVPRT) NEW set in step S820 is set. And the set value UPLMTP.
[0109]
As a result of the comparison, when (ADVPRT) NEW <UPLMTP, the process jumps from step S825 to step S829, and when (ADVPRT) NEW ≧ UPLMTP, in step S826, the set value UPLMTP is set as a new table value (ADVPRT) NEW ((( ADVPRT) NEW ← UPLMTP), and the process proceeds to step S829.
[0110]
On the other hand, if UPLMTP> ADVPRTLIM as a result of the comparison in step S824, the process branches from step S824 to step S827 to compare the new table value (ADVPRT) NEW with the partially corrected ignition timing limit value ADVPRTLIM, and (ADVPRT) NEW. If <ADVPRTLIM, the process jumps to step S829; if (ADVPRT) NEW ≧ ADVPRTLIM, in step S828, the partial correction ignition timing limit value ADVPRTLIM is set to a new table value (ADVPRT) NEW (((ADVPRT) NEW ← ADVPRTLIM), step S829). Proceed to.
[0111]
When the process proceeds to step S829 through a series of advance angle limiting steps, the partial correction ignition timing ADVPRT of the corresponding area ADDRESS of the partial correction table TBADVPRT is updated with the new table value (ADVPRT) NEW (ADVPRT ← (ADVPRT)). NEW), in step S833, the partial correction knock presence / absence change determination flag FLAGNK2 is cleared (FLAGNK2 ← 0), and the routine exits.
[0112]
As a result, the added value of the overall corrected ignition timing ADVTOT (= IGREG + TCMP × IGMBT) and the partially corrected ignition timing ADVPRT is limited to IGREG + IGMBT or less, and an over-advance angle is prevented.
[0113]
【The invention's effect】
According to the present invention as described above,In the ignition timing learning control of an engine of a vehicle equipped with an automatic transmission, an acceleration determination level indicating an acceleration level is set by a change in a throttle opening when learning of an ignition timing correction amount is prohibited for a predetermined number of ignitions during acceleration. . When it is determined that the acceleration is large by comparing the acceleration determination level with the set value, learning of the ignition timing correction amount is prohibited, and the number of ignitions that defines the learning prohibition period at this time is set to a value equal to or greater than the vehicle speed set value. When the vehicle speed is high, the speed is set to be higher than when the vehicle speed is lower than the set value. That is, in a vehicle equipped with an automatic transmission, a shift pattern is defined by the throttle opening and the vehicle speed. During acceleration when the throttle opening changes, if the vehicle speed is high, a kick-down occurs and the engine speed rapidly changes, It takes time for the engine state to stabilize, and when the vehicle speed is low, kickdown does not occur, the change in engine speed is relatively small, and the time until the engine stabilizes is short. Here, using the same parameters that determine the shift pattern affecting kickdown, that is, the throttle opening and the vehicle speed, an acceleration determination level that indicates the degree of acceleration by changing the throttle opening is set, and the acceleration determination level is set. When it is judged that the acceleration is large by comparing with the value, the number of ignitions that determines the learning inhibition period is set larger when the vehicle speed is higher than the set value and higher than when the vehicle speed is lower than the set value. Since the learning inhibition period during acceleration is determined by the number of ignitions, the effect of kickdown during acceleration and the learning inhibition period can be accurately matched.
Therefore, when the vehicle equipped with an automatic transmission is accelerating, the learning suspension period can be appropriately determined in accordance with the period until the engine state is stabilized due to the change in the engine speed due to the kickdown, thereby deteriorating the controllability. Thus, stable ignition timing control can be reliably realized, and the ignition timing controllability can be significantly improved.
[Brief description of the drawings]
FIG. 1 is a flowchart (part 1) of a procedure for learning a whole correction coefficient and a partial correction ignition timing.
FIG. 2 is a flowchart (part 2) of a procedure for learning a whole correction coefficient and a partly corrected ignition timing.
FIG. 3 is a flowchart (part 3) of a procedure for learning a whole correction coefficient and a partial correction ignition timing;
FIG. 4 is a flowchart of an acceleration determination procedure (part 1).
FIG. 5 is a flowchart of an acceleration determination procedure (part 2).
FIG. 6 is a flowchart of a cylinder discrimination / engine speed calculation procedure;
FIG. 7 is a flowchart of an ignition timing setting procedure (part 1).
FIG. 8 is a flowchart of an ignition timing setting procedure (part 2).
FIG. 9 is a flowchart of a θ2 interrupt in the energization / ignition control procedure.
FIG. 10 is a flowchart of a θ3 interrupt in the energization / ignition control procedure.
FIG. 11 is a flowchart showing a subroutine for learning the entire correction coefficient (part 1).
FIG. 12 is a flowchart showing a subroutine for learning the entire correction coefficient (part 2);
FIG. 13 is a flowchart showing a subroutine for learning the entire correction coefficient (part 3).
FIG. 14 is a flowchart showing a subroutine for learning a partially corrected ignition timing (part 1);
FIG. 15 is a flowchart showing a subroutine for learning a partially corrected ignition timing (part 2);
FIG. 16 is a flowchart showing a subroutine for learning a partially corrected ignition timing (part 3);
FIG. 17 is a flowchart illustrating a subroutine for learning a partially corrected ignition timing (part 4);
FIG. 18 is a conceptual diagram of a partial correction table.
FIG. 19 is a schematic diagram of an engine control system.
FIG. 20 is a front view of a crank rotor and a crank angle sensor.
FIG. 21 is a front view of a cam rotor and a cam angle sensor.
FIG. 22 is a circuit configuration diagram of a control device.
FIG. 23 is a time chart showing ignition timing.
[Explanation of symbols]
LEVACC acceleration judgment level
ACCDVG setting value
VSP vehicle speed
COUNTACC Learning stop ignition count

Claims (1)

The ignition timing correction amount according to the presence or absence of knock is learned, the ignition timing is controlled based on the learned ignition timing correction amount , the acceleration is determined, and the acceleration timing correction is performed for a predetermined number of ignitions during acceleration. In the engine ignition timing learning control method for prohibiting the learning of the amount ,
An ignition timing learning control of an engine of a vehicle equipped with an automatic transmission, wherein an acceleration determination level indicating an acceleration level is set by a change in a throttle opening,
When it is determined that the acceleration is large by comparing the acceleration determination level with the set value, learning of the ignition timing correction amount is prohibited,
In addition, the ignition count for setting the learning inhibition period at this time is set larger when the vehicle speed is higher than the set value, when the vehicle speed is higher than the set value, compared to when the vehicle speed is lower than the set value. Timing learning control method.

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