JP5258726B2 - Idle stop control method - Google Patents

Description

  The present invention relates to an idle stop control method for an engine mounted on a vehicle.

  In order to improve fuel efficiency, the vehicle stops with a signal, etc., and when it is determined that a predetermined engine stop condition is satisfied, the engine is automatically stopped and the engine is automatically restarted when starting. Stops are widely known.

  When performing such idle stop control, it is required to reliably restart the engine when starting. For this purpose, for example, paying attention to the fact that engine restart may not be performed smoothly when idling stop is performed when the engine is not sufficiently warm, and idling stop is performed when the engine temperature is lower than a predetermined temperature. Is known (for example, see Patent Document 1).

  However, there are cases where the engine can be reliably restarted even when the engine temperature is low. Nevertheless, in the control described in Patent Document 1, when the engine temperature is lower than the predetermined temperature, the idle stop is uniformly prohibited, so that the engine can be reliably restarted. Even so, idle stop is prohibited, and the effect of improving fuel efficiency is impaired.

  In addition, in the control method described in Patent Document 1, restart after an idle stop is in danger because the battery has deteriorated over time or the amount of charge is insufficient even if the battery is new. There is also a problem that the situation cannot be handled.

JP 58-140439 A

  An object of the present invention is to further improve fuel efficiency while paying attention to the above points and more accurately determining whether or not an idle stop is possible, enabling reliable restart after an idle stop.

  That is, the idle stop control method according to the present invention includes a first minimum value of the battery voltage detected immediately after engine start, a battery temperature, and a second minimum value detected after the battery voltage reaches the first minimum value. And a control method that is performed with reference to the engine temperature, wherein a first threshold value to be compared with a first minimum value is determined according to the level of the battery temperature, and a second threshold value to be compared with a second minimum value Is determined according to the level of the engine temperature, the first minimum value detected at the latest engine start exceeds the first threshold value, and the second minimum value detected at the latest engine start is the second minimum value. When the engine temperature exceeds a threshold and the engine temperature is within a predetermined idle stop permission temperature range, the next idle stop is permitted.

  The first minimum value occurs at the moment when a large start-up inrush current flows into the starter. The first minimum value tends to be lower as the aging of the battery progresses and the charge amount of the battery decreases, but it is also affected by the battery temperature. If the battery temperature is low, the first minimum value will be low even if the battery is new and is sufficiently charged to allow reliable restart of the engine. On the contrary, when the battery temperature is high, the first minimum value is high regardless of the battery state. According to the control method described in the previous stage, if the battery temperature is low, the first threshold is set low, and if the battery temperature is high, the first threshold is set high. Thus, it is possible to more accurately determine whether sufficient power can be supplied to the starter.

  The second minimum value occurs at the moment when the mechanical load of the engine first increases after the start of the engine starts, or when the piston reaches the vicinity of the top dead center. The second minimum value is generated immediately after the energization of the electromagnetic solenoid for hydraulic control is started. This second minimum is affected by engine temperature, in other words, friction loss. When the engine temperature is low, the friction loss is large, and thus the power consumption of the starter motor is also large. Therefore, even if the battery is in a state where sufficient power can be supplied to the solenoid or the like, the second minimum value is low. On the contrary, when the engine temperature is high, the friction loss is small, and the power consumption of the starter motor is also small. Therefore, the second minimum value is high regardless of the battery state. According to the control method described above, if the engine temperature is low, the second threshold value is set low, and if the engine temperature is high, the second threshold value is set high. It is possible to more accurately determine whether sufficient power can be supplied to the electromagnetic solenoid or the like after the motor is started.

  When the first minimum value exceeds the first threshold value, the second minimum value exceeds the second threshold value, and the engine temperature is within a predetermined idle stop permission temperature range, the idle stop is permitted. By doing so, the accuracy of determining whether or not idle stop is possible can be improved, so that restart after an idle stop can be ensured with a simple device without providing an auxiliary battery or the like for suppressing a drop in battery voltage at engine start. Can be allowed to stop idle more times, and further fuel efficiency can be expected.

  Further, in order to more reliably perform the restart after the idle stop, the battery is deteriorated and the restart after the idle stop is not reliably performed with respect to the first threshold value and the second threshold value. What is set to the higher potential side than the first minimum value and the second minimum value in the battery use limit which is a limit state is desirable. This is because a margin (safety zone) is provided in order to prevent idle stop in the vicinity of the battery use limit. In addition, by performing idle stop in the vicinity of the battery usage limit, the charge stored in the battery is greatly consumed, thereby preventing a problem that shortens the battery life.

  Furthermore, as a desirable mode in the case of performing control for forcibly restarting the engine (regardless of the driver's intention) to charge the battery when a long time has elapsed since the start of the idle stop, When the time integral value of the supply current from exceeds a predetermined value, the operation of the engine is restarted, and the predetermined value is made smaller as the difference between the first minimum value and the first threshold value is smaller, or Examples include a smaller difference between the second minimum value and the second threshold value. With such a configuration, when the battery voltage is low, the idle stop time can be shortened, and more time can be devoted to charging the battery.

  According to the idle stop control method of the present invention, the first minimum value of the battery voltage detected when the starter is started exceeds the first threshold value, and is detected after the electromagnetic clutch connecting the engine and the transmission is started. The idling stop is permitted only when the second minimum value exceeds the second threshold value, the first threshold value is determined according to the battery temperature level, and the second threshold value is determined based on the engine temperature level. Therefore, when the battery temperature is low, the first threshold value is set low, and when the engine temperature is low, the second threshold value is set low so that the engine can be reliably restarted from the battery. It is possible to more accurately determine that the power can be supplied to such an extent that can be expected. That is, the idling stop can be executed more times within a range where the restart after the idling stop can be surely performed, and the fuel efficiency can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows schematic structure of one Embodiment of this invention. The figure which shows the transient fluctuation | variation of the battery voltage which concerns on the same embodiment. The figure which shows the outline of the 1st threshold value map which concerns on the embodiment. The figure which shows the outline of the 2nd threshold value map which concerns on the same embodiment. The flowchart which shows the outline of the control procedure of the embodiment. The flowchart which shows the outline of the control procedure of the embodiment. The flowchart which shows the outline of the control procedure of the embodiment.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a transmission system to which the present invention is applied. The torque output from the engine 2 rotates the input shaft 30 via the drive plate 83 and the torque converter 3. The rotation of the input shaft 30 is transmitted to the drive shaft 510 via the forward / reverse switching device 4 using the planetary gear mechanism 41, and rotates the driven shaft 520 through a shift in the CVT 5. An output gear 524 is fixed to the driven shaft 520, and this output gear 524 meshes with the ring gear of the differential device 6 to rotate the output shaft 60 and thus a driving wheel (not shown). In this embodiment, the forward / reverse switching device 4 and the CVT 5 are accommodated in a transmission case (not shown).

  The forward / reverse switching device 4 includes the planetary gear mechanism 41, a reverse brake 48, and a direct coupling clutch 49. The sun gear 42 of the planetary gear mechanism 41 is connected to the input shaft 30, and the ring gear 43 is connected to the drive shaft 510. The planetary gear mechanism 41 is a single pinion system. The reverse brake 48 is provided between the carrier 45 that supports the pinion gear 44 and the transmission case. The direct coupling clutch 49 is provided between the carrier 45 and the sun gear 42. Here, the reverse brake 48 and the direct coupling clutch 49 are both formed using a hydraulic clutch mechanism, and hydraulic oil is supplied from a hydraulic supply source (not shown) via the hydraulic control device 9 and the pipes 91 and 92. receive. Here, when the direct clutch 49 of the forward / reverse switching device 4 is released and the reverse brake 48 is engaged, the driving force input from the torque converter 3 is reversely and decelerated and transmitted to the drive shaft 510, and the forward drive state is established. Become. Conversely, when the reverse brake 48 is released and the direct clutch 49 is engaged, the carrier 45 and the sun gear 42 of the planetary gear mechanism 41 rotate together, so that the driving force input from the torque converter 3 is directly applied to the drive shaft 510. It is transmitted and enters the reverse drive state.

  The CVT 5 is a belt type that includes a driving pulley 51 and a driven pulley 52 and a belt 53 wound around the pulleys 51 and 52 as elements. The drive pulley 51 includes a fixed sheave 511 fixed to a drive shaft (pulley shaft) 510, a movable sheave 512 supported on the drive shaft 510 so as to be axially displaceable via a roller spline, and a movable sheave 512. A hydraulic servo 513 disposed behind the vehicle is provided, and the gear ratio can be changed steplessly by operating the hydraulic servo 513 and displacing the movable sheave 512. The driven pulley 52 includes a fixed sheave 521 fixed to a driven shaft (pulley shaft) 520, a movable sheave 522 supported on the driven shaft 520 via a roller spline so as to be axially displaceable, and a movable sheave. A hydraulic servo 523 disposed on the rear side of 522 is provided, and a belt thrust necessary for torque transmission is given by operating the hydraulic servo 523 and displacing the movable sheave 522. Here, the hydraulic servo 513 of the driving pulley 51 and the hydraulic servo 523 of the driven pulley 52 are both supplied with hydraulic oil from a hydraulic supply source (not shown) via the hydraulic control device 9 and the pipes 93 and 94. .

  The hydraulic control device 9 includes a solenoid valve 9a that controls the hydraulic pressure supplied to the reverse brake 48 and the direct coupling clutch 49 (hereinafter referred to as the reverse brake 48), and the hydraulic pressure supplied to the hydraulic servo 513 of the drive pulley 51. And a solenoid valve 9c for controlling the hydraulic pressure supplied to the hydraulic servo 523 of the driven pulley 52.

  The starter motor 81 that cranks the engine 2 when the engine 2 is started has its pinion gear 82 engaged with the ring gear 84 on the outer periphery of the drive plate 83 to drive the drive plate 83 to rotate.

  The engine 2, the CVT 5, the starter motor 81, the hydraulic control device 9 and the like are controlled by the electronic control device 1. The electronic control device 1 is a microcomputer system including a CPU, a RAM, a ROM, an I / O interface, and the like. The control program is stored in the ROM in advance, and when executed, it is read from the ROM into the RAM and decoded by the CPU.

  The electronic control unit 1 outputs a rotation speed signal 71 output from a sensor that detects the engine rotation speed, a depression amount signal 72 that is output from a sensor that detects a depression amount of a brake pedal, and an ignition key (or an ignition switch). Ignition operation signal 73 to be performed, water temperature signal 74 output from a sensor for detecting the cooling water temperature of the engine 2, battery temperature signal 75 output from a sensor for detecting the temperature of the battery, and voltage for detecting a voltage between both electrodes of the battery Refer to the voltage signal 76 output from the meter, the current signal 77 output from the ammeter that detects the magnitude of the current supplied from the battery to the electrical system, the vehicle speed signal 78 output from the sensor that detects the vehicle speed, etc. To do. The water temperature signal 74 is a state quantity representing the friction loss of the engine 2 body.

  Further, the electronic control unit 1 inputs a fuel injection signal and an ignition signal to the fuel injection valve and the spark plug of the engine 2 and controls the gear ratio for the hydraulic servos 513 and 523 of the CVT 5. Enter. At the time of starting the engine 2, the starter motor 81 is energized to operate it.

  When the electronic control unit 1 starts the internal combustion engine 2, the following processing is performed. That is, when the electronic control unit 1 senses that an operation for starting the internal combustion engine 2 has been performed, such as when the ignition key is operated or the foot is released from the brake pedal during idle stop, the starter motor 81 is detected. The start command is input to the starter motor 81 and the fuel injection control and the ignition control are started.

Therefore, in the present embodiment, when the internal combustion engine 2 is started, the electronic control device 1 executes the following threshold determination program. This threshold value determination program includes a first minimum value of battery voltage (hereinafter referred to as A point voltage V _a ) that is detected and detected when the starter is started immediately after engine start time t ₁ as shown in FIG. Specifically, a process for storing a second minimum value (hereinafter referred to as B point voltage V _b ) detected immediately after the start of energization of the solenoid valve 9a for supplying hydraulic pressure to the reverse brake 48, the battery temperature signal 75 process for determining the first threshold value V _ath the first threshold value map as shown in FIG. 3 the battery temperature T _b as a parameter indicating, and as shown in FIG. 4 the engine temperature T _e indicated by the coolant temperature signal 74 as a parameter The second threshold value V _bth is determined by the second threshold map. Then, the first threshold value V _ath and the second threshold value V _bth determined by the threshold determination program, so as to use as the first threshold value V _ath and the second threshold value V _bth in idle stop control program that is executed immediately after ing. The first threshold map and the second threshold map actually store the first threshold V _ath or the second threshold V _bth corresponding to a typical battery temperature or engine temperature in a predetermined area of the ROM, The determination of the first threshold value V _ath or the second threshold value V _bth is performed by interpolation calculation. _Further , as shown in FIGS. 3 and 4, the first threshold value V _ath and the second threshold value V _bth are battery usage limits that are in a limit state in which the battery is deteriorated and restart after an idle stop is not reliably performed. _Are set on the higher potential side than the point A voltage _Valim and the point B voltage _Vblim .

Incidentally, the A point voltage V _a is the minimum value of battery voltage generated at the moment when the flow is large startup inrush current to the starter, when the battery temperature is low, a though battery new, re-engine the point a voltage V _a even in a state in which to perform the start surely is a degree sufficient charging expected decreases. Conversely, when the battery temperature is high, the A point voltage V _a without depending on the battery state how the higher. Reflecting this, as shown in FIG. 3, the first threshold value V _ath becomes lower as the battery temperature T _b becomes lower, and conversely becomes higher as the battery temperature T _b becomes higher. Is set.

The point B voltage V _b is a minimum value of the battery voltage generated at the moment when the mechanical load of the engine first increases after the start of the engine, for example, when the piston reaches near the top dead center. As described above, the point in time when the point voltage _Vb is generated is immediately after the start of energization of the solenoid valve 9a for supplying hydraulic pressure to the reverse brake 48 and the like. When the engine temperature _Te is low, the power consumption of the starter motor 81 due to the friction loss inside the engine 2 increases, so that the hydraulic control with a high voltage V _s that ensures operation while supplying power to the starter motor 81 The solenoid valve 9a of the device 9 was also in a battery state where power sufficient to operate the solenoid valve 9a was supplied and hydraulic oil was supplied to the reverse brake 48 etc. so that the engaged state of the reverse brake 48 etc. could be maintained. Even so, the point B voltage _Vb becomes low. On the contrary, when the engine temperature is high, the power consumption of the starter motor 81 due to the friction loss becomes small regardless of the battery state, so that the point B voltage _Vb becomes high. Reflecting this, as shown in FIG. 4, the second threshold value V _bth is such that the lower value the lower the engine temperature T _e, so that the engine temperature T _e becomes higher the higher the value in the opposite It is set. The second threshold value V _bth at the lower limit temperature at which idle stop is permitted (hereinafter referred to as the idle stop permission lower limit temperature T ₁ ) is higher than the voltage V _s at which the operation of the solenoid valve 9a is guaranteed. It is set.

  Hereinafter, the procedure of the process performed by the threshold value determination program will be described with reference to FIG. 5 which is a flowchart.

First, in step S1, the starter activation time t minimum value, that is the point A voltage V _a of the first battery voltage detected after _1, and time t of the A point voltage V _a the recorded measurement points (in Fig. 2 determining the battery temperature T _b at _2).

In step S2, the first threshold value V _ath is determined using the battery temperature T _b as a parameter.

In step S3, the present time is the starter start time t ₁ to a predetermined length period tt energization to the start to the hydraulic supply start i.e. the solenoid valve 9a has passed to the reverse brake 48 or the like (time in FIG. 2 t ₃ ) Wait. If the said period has passed, it will progress to step S4.

In step S4, the minimum value of the first battery voltage detected after time t ₃ , that is, the point B voltage V _b , and the measurement point (time t ₄ in FIG. 2) where the point B voltage V _b is recorded. The engine temperature _Te is determined.

In step S5, it determines the second threshold value V _bth the engine temperature T _e as a parameter.

Further, the electronic control unit 1 also executes an idle stop permission determination program for performing control as described below. The idle stop permission determination program, wherein is performed subsequent to the threshold determination program, the A point voltage V _a detected when the engine is started exceeds the first threshold V _ath, the B that are detected during engine start point voltage V _b exceeds the second threshold value V _bth, and the water temperature signal 74 is the engine temperature T _e indicated allow next idle stop when within a predetermined idle stop permission temperature range, otherwise Performs control to prohibit the next idle stop.

  A procedure of processing performed by the idle stop permission determination program will be described below with reference to FIG. 6 which is a flowchart.

In step S6, it is determined whether the point A voltage V _a exceeds the first threshold V _ath. A point voltage V _a is the case above the first threshold value V _ath, the process proceeds to step S7. If point A voltage V _a does not exceed the first threshold value V _ath, the process proceeds to step S10.

At step S7, B point voltage V _b is equal to or above or a second threshold value V _bth. B point voltage V _b is the case above the second threshold value V _bth, the process proceeds to step S8. If the voltage at the point B V _b does not exceed the second threshold value V _bth, the process proceeds to step S10.

In step S8, the engine temperature T _e indicated by the temperature signal h from the water temperature sensor 75 is within a predetermined idle stop permission temperature range, in particular the engine temperature T _e exceeds the idle stop permission lower limit temperature T ₁ of and determines whether below the idle stop permission upper limit temperature T _2. If the engine temperature T _e exceeds the idle stop permission lower limit temperature T ₁ of and below the idle stop permission upper limit temperature T _2, the process proceeds to step S9. Otherwise, the process proceeds to step S10.

  In step S9, the next idle stop control is permitted.

  On the other hand, in step S10, the next idle stop control is prohibited.

  When the next idle stop control is permitted by this idle stop permission determination program, when it is determined that a predetermined idle stop condition is satisfied, specifically, the vehicle speed indicated by the vehicle speed signal 78 is 0 km / h. Idle stop control is performed when a certain condition that the depression amount signal 72 indicates that the brake pedal is operated is satisfied. On the other hand, when the next idle stop control is prohibited by the idle stop permission determination program, the idle stop control is not performed even when it is determined that the predetermined idle stop condition is satisfied.

In addition, in the present embodiment, the electronic control device 1 is executed immediately after the start of the idle stop control, and also executes an engine operation resumption control program for performing control as described below. The engine operation restart control program, battery gradually calculates the time integral I _p of the current supplied from the time of reaching the fully charged, the engine if the time integral is determined to have reached the predetermined current integral I _th Control to resume operation is performed. In the present embodiment, the predetermined current integral I _th, to determine the point B and the voltage V _b of the difference between the second threshold value V _bth as parameters. Specifically, so that performed by referring to a predetermined current integral map showing the correspondence between the difference and the predetermined current integral value I _th and the B point voltage V _b and the second threshold value V _bth. The predetermined current integral I _th is set so that the smaller the value the difference [Delta] V _b is smaller between the point B and the voltage V _b the second threshold value V _bth. The predetermined current integrated value map actually indicates a predetermined current integrated value I _th corresponding to a difference value between the representative point B voltage V _b and the second threshold value V _{bth in} a predetermined area of the storage device 42. I remember the determination of a predetermined current integral I _th is to perform the interpolation calculation.

  A procedure of processing performed by the engine operation resumption control program will be described below with reference to FIG. 7 which is a flowchart.

In step S11, a difference ΔV _b between the point B voltage V _b and the second threshold value V _bth is obtained.

In step S12, the difference [Delta] V _b between said B point voltage V _b determined second threshold value V _bth in step S11 as parameters, determines a predetermined current integral I _th.

In step S13, the time integration _Ip from the time when the battery of the supply current I from the battery indicated by the current amount signal 77 reaches full charge is calculated. Specifically, after the battery reaches full charge, the supply current I from the battery is detected every predetermined unit time, and the sum of the supply current I at each measurement point after the battery reaches full charge is Calculate as time integration I _p .

In step S14, it is determined whether or not the time integration I _p exceeds the predetermined current integration value I _th . If it is determined that the time integration I _p exceeds the predetermined current integration value I _th , the process proceeds to step S15. If it is determined that the time integration I _p does not exceed the predetermined current integration value I _th , the process returns to step S13.

  In step S15, the engine operation is resumed, and the engine operation resumption control program is terminated.

As described above, if the idle stop control method according to the present embodiment is employed, the battery voltage T _a is directly detected and the battery temperature T _b is low, as shown in FIG. Compared with a mode in which the first threshold value V _ath is set to a uniform value regardless of the temperature by setting the first threshold value V _ath high when the first threshold value V _ath is low and conversely the battery temperature T _b is high. Thus, it is possible to more accurately determine whether sufficient power can be supplied to the starter. Also, if the engine temperature T _e is low is low the second threshold value V _bth, as shown in FIG. 4, when the engine temperature T _e is high conversely by setting high the second threshold value V _bth, the Compared with the mode in which the two threshold values V _bth are set to a uniform value regardless of the temperature, it is determined whether or not sufficient power can be supplied to operate the solenoid valve 9a of the hydraulic control device 9 after the starter is started. Can be performed more accurately. Then, the A point voltage V _a exceeds the first threshold V _ath, the point B exceeds the voltage V _b the second threshold value V _bth, and the engine temperature T _e is within the predetermined idle stop permission temperature range By allowing the idling stop only in the case of the engine, the accuracy of determining whether or not the idling stop is possible can be improved, so that an auxiliary battery or the like for suppressing a drop in the battery voltage at the time of starting the engine is not provided. In addition, the simple device can reliably perform the restart after the idling stop, and can permit the idling stop more times, and can further improve the fuel consumption. Also, the first threshold value V _ath and the second threshold value V _bth can be set. , since each set to a high potential side than the point a voltage V _alim and the B point voltage V _blim in the battery usage limit, the battery used Will be provided a margin for preventing performed an idle stop at the limit vicinity and thus, it is possible to restart after idle stop more securely. In addition, by setting the first threshold value V _ath and the second threshold value V _bth in this way, by performing idle stop in the vicinity of the use limit, the charge stored in the battery is greatly consumed and the battery life is shortened. It can also prevent inconveniences.

Further, in order to charge the battery when the vehicle is stopped for a long time, the engine is activated when the time integral value I _p of the supply current from the battery after the battery reaches full charge exceeds the predetermined current integral value I _th. And the predetermined current integrated value I _th is made smaller as the difference ΔV _b between the point B voltage V _b and the second threshold value V _bth is smaller, so that the idle stop time is shortened. And more time can be devoted to charging the battery. From this, the point B voltage V _b at the engine restart immediately after that is sufficiently higher than the second threshold value V _bth and the minimum voltage (V _{s in} FIG. 4) with which the operation of the solenoid valve 9a is guaranteed. Can be high. Therefore, it is possible to increase the possibility of idling stop when the vehicle is stopped immediately after that, and the fuel efficiency can be further improved from this point.

  The present invention is not limited to the embodiment described above.

  For example, the first threshold value and the second threshold value may be set to the first minimum value and the second minimum value at the battery usage limit.

  In addition, when the time integral value of the current supplied from the battery after the start of the idle stop exceeds a predetermined value, the predetermined value when performing the control to restart the operation of the engine is set to the first minimum value and the first threshold value. Even if it is determined based on the difference that the predetermined value decreases as the difference decreases, the same effect as the above-described embodiment can be obtained. Further, the predetermined value may be determined based on both the difference between the first minimum value and the first threshold value and the difference between the second minimum value and the second threshold value. On the other hand, in some cases, the predetermined value may always be set to a constant value.

  In addition, various changes may be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Electronic controller 74 ... Water temperature signal 75 ... Battery temperature signal 76 ... Voltage signal 77 ... Current amount signal

Claims (3)

Control performed with reference to the first minimum value of the battery voltage detected immediately after engine startup, the battery temperature, the second minimum value detected after the battery voltage reaches the first minimum value, and the engine temperature A method,
Determining a first threshold value to be compared with the first minimum value according to the level of the battery temperature, determining a second threshold value to be compared with the second minimum value according to the level of the engine temperature;
The first minimum value detected at the latest engine start exceeds the first threshold, the second minimum value detected at the latest engine start exceeds the second threshold, and the engine temperature is a predetermined idle An idle stop control method characterized by permitting a next idle stop when the temperature is within a stop permission temperature range.   The first threshold value and the second threshold value are higher than the first minimum value and the second minimum value at the battery use limit, which is a limit state in which the battery deteriorates and the restart after the idle stop is not reliably performed. 2. The idle stop control method according to claim 1, wherein the idle stop control method is set on the potential side.   When the time integral value of the supply current from the battery exceeds a predetermined value, control is performed to restart the operation of the engine, and the predetermined value is determined by a difference between the first minimum value and the first threshold value. 3. The idle stop control method according to claim 1, wherein the idle stop control method is made smaller as it is smaller, or smaller as a difference between the second minimum value and the second threshold value is smaller.

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