JP5026362B2 - Automatic stop and start device for internal combustion engine - Google Patents

Automatic stop and start device for internal combustion engine Download PDF

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JP5026362B2
JP5026362B2 JP2008185577A JP2008185577A JP5026362B2 JP 5026362 B2 JP5026362 B2 JP 5026362B2 JP 2008185577 A JP2008185577 A JP 2008185577A JP 2008185577 A JP2008185577 A JP 2008185577A JP 5026362 B2 JP5026362 B2 JP 5026362B2
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battery
voltage
value
start
discharge current
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JP2010024906A (en
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賢治 上田
成則 斉藤
覚 水野
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株式会社デンソー
株式会社日本自動車部品総合研究所
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02NSTARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N11/00Starting of engines by means of electric motors
    • F02N11/08Circuits or control means specially adapted for starting of engines
    • F02N11/0814Circuits or control means specially adapted for starting of engines comprising means for controlling automatic idle-start-stop
    • F02N11/0818Conditions for starting or stopping the engine or for deactivating the idle-start-stop mode
    • F02N11/0825Conditions for starting or stopping the engine or for deactivating the idle-start-stop mode related to prevention of engine restart failure, e.g. disabling automatic stop at low battery state
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02NSTARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N2200/00Parameters used for control of starting apparatus
    • F02N2200/06Parameters used for control of starting apparatus said parameters being related to the power supply or driving circuits for the starter
    • F02N2200/063Battery voltage
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02NSTARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N2250/00Problems related to engine starting or engine's starting apparatus
    • F02N2250/02Battery voltage drop at start, e.g. drops causing ECU reset
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02NSTARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N2300/00Control related aspects of engine starting
    • F02N2300/20Control related aspects of engine starting characterised by the control method
    • F02N2300/2006Control related aspects of engine starting characterised by the control method using prediction of future conditions
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/40Engine management systems
    • Y02T10/48Switching off the internal combustion engine, e.g. stop and go

Description

  The present invention relates to an automatic stop process for an internal combustion engine to which an initial rotation is applied by a starter using a vehicle-mounted battery as a power source, and an automatic stop / start apparatus for an internal combustion engine that performs an automatic start process after the automatic stop process.

  As this type of automatic stop / start device, when the vehicle is stopped, (a) a condition that there is no abnormal discharge of the battery, and (a) a condition that the integrated value of the battery current from the start is greater than or equal to a predetermined value. And (c) what performs a so-called idle stop process based on the establishment of a logical product condition of three conditions: a condition that the battery temperature is equal to or higher than a predetermined value. Here, the condition (a) is for permitting idle stop on condition that the battery is normal. The above condition (A) is for permitting an idle stop on condition that the battery has sufficient discharge capability. Furthermore, the above condition (c) is for avoiding a rapid decrease in the discharge capacity due to the idle stop, in view of the fact that the rate of decrease in the discharge capacity with respect to the discharge amount increases as the battery temperature decreases.

In addition to the above technique, as a conventional automatic stop / start device, for example, there is one described in Patent Document 1 below.
JP 2005-331518 A

  By the way, after the idle stop process is performed, in addition to the case where the vehicle travel request is made by the user, the automatic start process is also performed when it is determined that the battery capacity is low. For this reason, when performing an idle stop process in the said aspect, there exists a possibility that an automatic start process may be made based on the fall of a battery capacity for a short time after an idle stop start. For this reason, there is a possibility that drivability will be lowered, such as giving the user a sense of discomfort. In addition, since the idle stop is performed even in a situation where the automatic start is performed in a short time after the idle stop, the number of automatic start increases naturally, which may shorten the battery life. .

  The present invention has been made to solve the above-described problems, and an object of the present invention is to more accurately perform an automatic stop process of an internal combustion engine to which an initial rotation is applied by a starting unit that uses a vehicle-mounted battery as a power source. An object of the present invention is to provide an automatic stop / start device for an internal combustion engine.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

The invention according to claim 1 is an automatic stop and start device for an internal combustion engine that performs an automatic stop process of an internal combustion engine to which an initial rotation is applied by a starter that uses a vehicle-mounted battery as a power source, and an automatic start process after the automatic stop process In the stop period of the internal combustion engine, it is determined that a condition is obtained that a voltage acquisition unit that acquires a detection value of the voltage of the battery and that there is no travel intention indication by the user after acquisition by the voltage acquisition unit On the condition that the automatic stop process is assumed, the prediction means for predicting the voltage of the battery immediately before the automatic start process based on the detection value acquired by the voltage acquisition means, and the prediction Judgment for determining whether or not to execute the automatic stop process based on a value obtained by subtracting a predicted value of the voltage drop amount of the battery accompanying the automatic start process from a voltage And a stage, the automatic starting process immediately before the voltage of the battery is characterized in that the stop period of the internal combustion engine is a voltage on the assumption that time having a predetermined length.

  In the above invention, by learning the battery voltage during the stop period of the internal combustion engine, it is possible to predict the battery voltage during the stop period of the internal combustion engine accompanying the subsequent automatic stop process. Then, in order to determine whether or not to execute the automatic stop process based on the minimum value of the battery voltage associated with the automatic start process predicted according to this, in a short period of time based on the state of charge of the battery after the automatic stop process. It is possible to preferably avoid the automatic start. For this reason, the stop period of the internal combustion engine accompanying the automatic stop process can be set to an appropriate time, and a decrease in drivability can be avoided. In addition, since the automatic start is not inevitably performed, it is possible to suitably suppress the shortening of the battery life.

  According to a second aspect of the present invention, in the first aspect of the invention, the prediction unit predicts a time change of the battery voltage based on a plurality of sampling values of the battery voltage during the stop period. Is calculated, and the prediction is performed based on the prediction formula.

  In the above invention, the battery voltage immediately before the automatic start of the battery is predicted based on a plurality of sampling values. For this reason, it is possible to predict the voltage immediately before the automatic start when the internal combustion engine stop period due to the automatic stop is longer than the sampling period of the sampling value. In addition, noise may be superimposed on the sampling value of the voltage, but since the voltage is predicted based on a plurality of sampling values, the influence of noise is better compared to the case where a single sampling value is used. It can also be suppressed.

  According to a third aspect of the present invention, in the second aspect of the present invention, the detection value used for calculating the prediction formula is a value after the time when the voltage drop rate of the battery becomes a predetermined value or less as the internal combustion engine stops. It is characterized by being.

  Before the internal combustion engine stops, the battery voltage fluctuates greatly. On the other hand, due to the stop process of the internal combustion engine, the voltage of the battery rapidly decreases, and thereafter the voltage drop speed gradually decreases. Here, when calculating the prediction formula including the voltage of the battery immediately after the stop processing of the internal combustion engine, the calculation accuracy of the prediction formula is likely to decrease. On the other hand, after the voltage drop rate decreases, the time change of the voltage is also gentle, so that the prediction formula can be easily calculated with high accuracy. For this reason, in the said invention, a prediction formula is computable with high precision.

  The determination that the voltage drop rate is after the time when the voltage drop rate is equal to or less than a predetermined value may be made by using the detected value of the battery voltage as an input, and further includes means for calculating a polarization correlation amount of the battery, and The calculated polarization correlation amount may be used as an input.

  The invention according to a fourth aspect is the invention according to the second or third aspect, wherein, when the prediction formula is not calculated, the determination means uses the predetermined function regardless of the detection value. The determination is performed by making a prediction.

  In the above invention, by preparing a function in advance, even when the prediction formula is not calculated, the determination by the determination means can be accurately performed.

  According to a fifth aspect of the present invention, in the invention according to the second or third aspect, the determination means has a predetermined value obtained by subtracting a predicted value of a voltage drop amount of the battery accompanying the automatic start process from the predicted voltage. If it is determined that the automatic stop process is to be executed on the condition that the above is true and the prediction formula is not calculated, the condition that the subtracted value is equal to or greater than a predetermined value is satisfied. Regardless of whether or not the battery is charged, it is determined that the automatic stop process is executed on condition that the state of charge of the battery is a predetermined state.

  In the said invention, when the prediction formula is not calculated, the opportunity for calculating the prediction formula can be quickly secured by executing the automatic stop process based on the state of charge.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the prediction means determines the temperature of the battery at each of the acquisition of the detected value and the current time at the time of the prediction. It is characterized by adding.

  The voltage drop rate of the battery during the stop period of the internal combustion engine due to the automatic stop increases as the battery temperature decreases. Therefore, when the temperature of the battery is different between the detection of the voltage used for prediction and the current time, the prediction accuracy of the voltage drop may be reduced. In the above invention, in view of this point, the prediction with the temperature of the battery taken into consideration makes it possible to maintain a high prediction accuracy of the voltage drop even when the temperature of the battery fluctuates.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the predicting means is configured to charge the battery at the time of obtaining the detected value and at the present time in the prediction. It is characterized by adding.

  The voltage drop rate of the battery during the stop period of the internal combustion engine due to the automatic stop becomes so large that there is no margin in the state of charge of the battery. Therefore, when the state of charge of the battery is different between the detection of the voltage used for prediction and the current time, the prediction accuracy of the voltage drop may be reduced. In the above invention, in view of this point, prediction with consideration of the state of charge of the battery makes it possible to maintain high prediction accuracy of the voltage drop even when the state of charge of the battery fluctuates.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the predicted value of the voltage drop amount of the battery is variably set according to the temperature of the battery. .

  In the above invention, in view of the fact that the voltage drop amount of the battery depends on the battery temperature, the predicted value of the voltage drop amount is set in consideration of the battery temperature. Thereby, a predicted value can be set with high accuracy.

  The invention according to claim 9 is characterized in that, in the invention according to any one of claims 1 to 8, the predicted value of the voltage drop amount of the battery is variably set according to the state of charge of the battery. To do.

  In the above invention, in view of the fact that the voltage drop amount of the battery depends on the state of charge of the battery, the predicted value of the voltage drop amount is set in consideration of the state of charge of the battery. Thereby, a predicted value can be set with high accuracy.

  A tenth aspect of the present invention is the battery according to any one of the first to ninth aspects, wherein the battery in a predetermined period after the detected value of the voltage of the battery becomes the minimum value due to the start of the internal combustion engine. Discharge current acquisition means for acquiring information on the amount of discharge current of the battery when the detection value of the voltage of the battery becomes the minimum value by the start based on the detected value of the voltage of the battery and the detected value of the discharge current of the battery In addition, the determination unit calculates a predicted value of the voltage drop amount of the battery accompanying the automatic start process based on information acquired by the discharge current acquisition unit.

  The detected value of the battery voltage and the detected value of the discharge current of the battery in a predetermined period after the detected value of the voltage of the battery becomes the minimum value due to the start of the internal combustion engine, the behavior of the discharge current of the battery, the battery Depends on the electrical state. For this reason, even if the discharge current amount of the battery when the detection value of the battery voltage becomes the minimum value cannot be directly detected, what value the discharge current amount is in the detection value? Information that can be estimated is included. In the above invention, in view of this point, information on the amount of discharge current of the battery when the detection value of the battery voltage becomes the minimum value can be acquired based on the detection value.

  Note that the above information is “the amount of discharge current of the battery when the detected value of the battery voltage becomes the minimum value” or “the maximum amount of discharge current of the battery for the start, that is, the discharge current before the start. It is desirable that the difference between the discharge current amounts of the battery when the detected value of the battery voltage becomes the minimum value due to the start with respect to the amount ".

  According to an eleventh aspect of the present invention, in the internal combustion engine according to the tenth aspect, the discharge current acquisition means performs the start with respect to the discharge current amount before the start as the maximum discharge current amount of the battery for the start. It is characterized in that a difference in the discharge current amount of the battery when the detected value of the voltage of the battery becomes a minimum value is estimated.

  The voltage drop amount of the battery accompanying the start can be calculated by multiplying the difference in the discharge current amount when the battery voltage becomes the minimum value by the start with respect to the discharge current amount before the start, by the internal resistance of the battery. For this reason, in the said invention, the voltage drop amount of the battery accompanying an automatic start process can be estimated suitably.

  According to a twelfth aspect of the present invention, in the invention of the eleventh aspect, the discharge current acquisition means estimates the internal resistance of the battery during a period until the voltage of the battery decreases to a minimum voltage due to the starting. The maximum discharge current amount is estimated according to the estimated internal resistance.

  The internal resistance of the battery during the period until the voltage of the battery drops to the minimum voltage determines the relationship between the difference between the voltage before starting the battery and the minimum voltage and the maximum discharge current amount. For this reason, the maximum discharge current amount can be suitably estimated by estimating the internal resistance.

  The discharge current acquisition means calculates a maximum amount of decrease in the battery voltage based on a difference between a value before starting by the starting means and a minimum value by starting with respect to a detected value of the battery voltage. And means for estimating the internal resistance of the battery based on a plurality of sets of detected values relating to the voltage of the battery and the discharge current of the battery at the time of starting, and the estimated internal resistance and the maximum reduction amount And a means for calculating the maximum discharge current amount.

  In the above invention, the maximum amount of decrease in voltage in order to make the maximum discharge current amount the difference in the discharge current amount of the battery when the detected value of the battery voltage becomes the minimum value due to the start with respect to the discharge current amount of the battery before starting. Is a parameter suitable for use in estimating the maximum discharge current amount. Further, since the internal resistance of the battery regulates the behavior of the discharge current of the battery, this is also a suitable parameter for estimating the maximum discharge current amount. In particular, if the internal resistance and voltage are determined, the discharge current amount of the battery is determined, and therefore the maximum discharge current amount can be estimated based on the maximum decrease amount and the internal resistance.

  Further, the discharge current acquisition means calculates the internal resistance of the battery based on a plurality of sets of detected values related to the battery voltage and the battery discharge current after the battery voltage is reduced to the minimum voltage by the starting. Means for estimating, means for estimating a difference between values before and after starting the starting means for the open circuit voltage of the battery based on the estimated internal resistance and the detected value; And a means for estimating the internal resistance of the battery when the voltage of the battery drops to the lowest voltage based on the difference and the estimated internal resistance.

  The internal resistance of the battery determined from the behavior of the current and voltage when the voltage of the battery decreases to the minimum voltage may be different from the internal resistance determined from the behavior of the current and voltage after decreasing to the minimum voltage. However, the inventors have found that these differences correlate with the difference between the values of the open circuit voltage of the battery before and after starting of the starting means. In the above invention, by paying attention to this point, the internal resistance of the battery when the voltage of the battery drops to the lowest voltage can be estimated with high accuracy. The internal resistance of the battery during the period until the battery voltage drops to the minimum voltage determines the relationship between the difference between the voltage before starting the battery and the minimum voltage and the maximum discharge current amount. For this reason, the maximum discharge current amount can be suitably estimated by estimating the internal resistance.

  According to a thirteenth aspect of the present invention, in the twelfth aspect of the present invention, the discharge current acquisition means is configured to determine the voltage of the battery and the discharge of the battery during a predetermined period after the voltage of the battery is reduced to the minimum voltage by the start. Means for estimating an internal resistance of the battery based on a plurality of sets of detected values relating to current, and based on a difference between a value before starting by the starting means and a minimum value by starting the detected value of the battery voltage The maximum amount of discharge current is estimated based on the maximum amount of decrease in the battery voltage and the estimated internal resistance, and the internal resistance of the battery during the predetermined period is reduced by the start of the battery. It is set to a period that is assumed to approximate the internal resistance of the battery in the period until the voltage drops to the lowest voltage. And butterflies.

  The internal resistance estimated based on the detected value in the predetermined period approximates the internal resistance of the battery in the period until the voltage of the battery decreases to the minimum voltage due to the start. It is possible to estimate the maximum discharge current amount based on the maximum decrease amount.

  The invention according to a fourteenth aspect is the invention according to the eleventh aspect, wherein the discharge current acquiring means is configured to discharge the battery voltage and the battery voltage in a predetermined period after the voltage of the battery is reduced to the minimum voltage by the starting. Means for estimating an internal resistance of the battery based on a plurality of sets of detected values relating to current, and a minimum voltage due to start by the starting means for a detected value of the battery voltage and a predetermined voltage after becoming the minimum voltage And the estimated internal resistance, the maximum discharge current amount is estimated. During the predetermined period, the internal resistance of the battery is reduced to the lowest voltage with the start. It is set to a period assumed to approximate the slope of a straight line connecting the time point when the voltage drops to the predetermined voltage and the time point when the voltage rises to the predetermined voltage. That.

  The internal resistance estimated based on the detected value in the predetermined period is calculated by approximating the slope of a straight line connecting the time when the battery voltage reaches the minimum voltage and the time when the battery voltage rises to the predetermined voltage. The amount of change in the discharge current amount when the battery voltage rises from the lowest voltage to the predetermined voltage can be calculated from the difference between the voltage and the predetermined voltage. For this reason, it is possible to estimate the maximum discharge current amount by setting the predetermined voltage to a value that enables detection of the discharge current.

(First embodiment)
Hereinafter, a first embodiment in which an in-vehicle battery state estimation device according to the present invention is applied to a vehicle battery state estimation device using a gasoline engine as a power generation device will be described with reference to the drawings.

  FIG. 1 shows an overall configuration of a system according to the present embodiment.

  The internal combustion engine 10 is a port injection type gasoline engine. The internal combustion engine 10 is a power generation device for a vehicle, and its output shaft (crankshaft 12) is mechanically connected to drive wheels. On the other hand, the power generation apparatus 20 includes an alternator 22 as a generator and a regulator 24 as a control circuit that controls the output of the alternator 22. Here, the rotor of the alternator 22 is mechanically connected to the crankshaft 12 of the internal combustion engine 10 and is rotated by the rotational force of the crankshaft 12.

  A battery 30 as a lead storage battery is connected to the battery terminal TB of the power generation device 20. An electric load 44 is connected to the battery 30 via the switch 42 in parallel. Furthermore, a starter 40 that applies initial rotation to the crankshaft 12 of the internal combustion engine 10 is connected to the battery 30 as an electrical load. On the other hand, the power supply line between the battery terminal TB and the battery 30 and the ignition terminal TIG of the power generation apparatus 20 are connected via an ignition switch 46.

  The electronic control unit (ECU 50) as one of the electric loads of the battery 30 is mainly composed of a microcomputer and includes a storage device such as a constant storage holding device 51. Here, the constant memory holding device 51 is a memory device that always holds the memory regardless of the state of the start switch of the engine control system (main power source of the control device (ECU 50): ex. Ignition switch 46). . Specifically, there are, for example, a backup RAM in which the power supply state is always maintained regardless of the state of the start switch, and a non-volatile memory such as an EEPROM that always holds a memory regardless of whether power is supplied.

  The ECU 50 controls the internal combustion engine 10 and the power generation device 20. In particular, in the ECU 50, the detection value of the current sensor 52 that detects the current discharged from the battery 30 and the current charged to the battery 30, the detection value of the temperature sensor 54 that detects the temperature of the battery 30, and further the battery 30. The voltage applied to the battery terminal TB of the power generation device 20 (the output voltage of the power generation device 20) is controlled based on the detection value of the voltage sensor 56 that detects the voltage of. Specifically, the ECU 50 outputs a command value (command voltage) of the output voltage to the command terminal TR of the power generation device 20. Thereby, the regulator 24 controls the output voltage to the command voltage. Further, the ECU 50 takes in a power generation state signal indicating the power generation capability of the power generation device 20 via the monitor terminal TF of the power generation device 20. Here, the power generation capacity is quantified by the ON / OFF time ratio of the switching element in the regulator 24 (specifically, the ratio of the ON time to the ON / OFF cycle: Duty).

  The control of the output voltage is performed so as to reduce the increase in the fuel consumption of the internal combustion engine 10 by the power generation by the power generation device 20 as much as possible while keeping the state of charge (SOC) of the battery 30 within an allowable range. Is called. Here, the SOC is a physical quantity obtained by quantifying the discharge capacity of the battery 30. Specifically, the ratio of the current charge amount to the full charge of the battery 30 is quantified. The SOC is usually quantified by “5 hour rate capacity”, “10 hour rate capacity” or the like. It is known that the open end voltage, which is the voltage when the terminal of the battery 30 is open, depends on the SOC. Specifically, the open end voltage increases as the SOC increases. Specifically, for example, the open circuit voltage when the SOC is “100%” is “12.8 V”, and the open circuit voltage when the SOC is “0%” is “11.8 V”.

  Further, the ECU 50 stops the idle rotation speed control of the internal combustion engine 10 and stops the internal combustion engine 10 automatically when the vehicle is stopped, so-called idle stop control (automatic stop processing), or the internal combustion engine 10 from the idle stop control. An automatic start process for automatically starting is performed. Here, the automatic start process is executed by performing combustion control after applying the initial rotation to the crankshaft 12 of the internal combustion engine 10 by starting the starter 40. However, when starting the starter 40, it is known that a large amount of discharge current flows from the battery 30 to the starter 40 in a very short time until the starter 40 starts rotating. At this time, the voltage of the battery 30 drops greatly. On the other hand, the ECU 50 using the battery 30 as a power supply means defines a minimum value of the power supply voltage that can maintain the reliability of the operation. For this reason, when the voltage of the battery 30 decreases excessively during the automatic start process of the internal combustion engine 10, the reliability of the operation of the ECU 50 may decrease. For this reason, it is desirable to perform the idle stop control under the condition that the voltage drop of the battery 30 due to the automatic start process does not fall below the minimum value of the operation guarantee voltage of the ECU 40.

  Therefore, in the present embodiment, prior to performing the idle stop process, the minimum voltage value of the battery 30 associated with the automatic start process after the idle stop is predicted, and it is determined that this does not fall below the minimum value of the operation guarantee voltage. Allow idle stop as a condition. This will be described in detail below.

FIG. 2 shows the transition of the voltage of the battery 30 after the idle stop process. As shown in the figure, the voltage of the battery 30 is reduced by the stop process of the internal combustion engine 10 and further greatly reduced by the automatic start process. Therefore, after the automatic stop, the minimum voltage Vmin of the battery 30 accompanying the automatic start is predicted by predicting the voltage Vbr of the battery immediately before the automatic start process and the voltage drop amount ΔVst of the battery 30 accompanying the automatic start. Can do. If this exceeds the threshold voltage Vth set based on the minimum value of the operation compensation voltage, the idle stop can be permitted. Hereinafter, “a. Processing related to prediction of voltage drop amount ΔVst”, “b. Prediction processing of voltage of battery 30 immediately before automatic start”, and “c. Determination processing of whether or not to perform idle stop” will be described in this order.
<A. Processing related to prediction of voltage drop amount ΔVst>
The voltage drop amount ΔVst can be predicted by predicting the maximum discharge current amount of the battery 30 accompanying the automatic start and the internal resistance Rin of the battery 30 at that time. Here, in the present embodiment, the maximum discharge current amount is predicted based on the maximum discharge current amount of the battery 30 when the internal combustion engine 10 is started by turning on the ignition switch 46.

  FIG. 3A shows the behavior of the current of the battery 30 as the starter 40 is activated. When the starter 40 and the battery 30 are electrically connected, the discharge current amount of the battery 30 rapidly increases and reaches the maximum value Imax at time t1. The maximum value Imax is determined by the resistance of the starter 40, the internal resistance of the battery 30, the wiring resistance between the starter 40 and the battery 30, and the like. When the starter 40 starts rotating, the current flowing through the starter 40 decreases. In other words, the discharge current of the battery 30 decreases. Here, the current sensor 52 does not set the maximum value Imax of the discharge current of the battery 30 when the starter 40 is activated within the detectable range. Therefore, in the present embodiment, the maximum discharge current amount of the battery 30 is estimated when the internal combustion engine 10 is started by operating the ignition switch 46.

  FIG. 3B shows changes in the current and voltage of the battery 30 when the starter 40 is activated. As shown in the figure, when the discharge current of the battery 30 increases with the starter 40 and reaches the maximum value Imax, the voltage of the battery 30 decreases to the minimum voltage Vbtm. At this time, since the influence of the polarization of the battery 30 is very small, the internal resistance of the battery 30 estimated from the voltage change with respect to the current change of the battery 30 is very close to the true value. However, since this period is very short, it is difficult to calculate the internal resistance by sampling current and voltage during this period.

  On the other hand, after the discharge current reaches the peak (maximum value Imax), the voltage of the battery 30 also increases as the discharge current decreases. Here, after the discharge current of the battery 30 reaches the maximum value Imax, the period during which the discharge current decreases is relatively long. Sampling is possible. For this reason, the internal resistance of the battery 30 can be calculated relatively easily during this period. On the other hand, it is generally considered that the internal resistance Rin of the battery 30 during the period until the discharge current of the battery 30 reaches the maximum value Imax is different from the internal resistance after the maximum value Imax. Therefore, it is difficult to estimate the maximum value Imax based on the minimum voltage Vbtm of the battery 30 using the internal resistance of the battery 30 calculated based on the detected value of the current after the discharge current reaches the maximum value Imax. .

  Therefore, in this embodiment, the difference between the internal resistance Rc after reaching the maximum value Imax and the internal resistance Rin before reaching the maximum value Imax has a correlation with the open-circuit voltage difference ΔVo before and after starting the starter 40. Focus on the nature. FIG. 4 shows measurement data that supports this property. In FIG. 4, the vertical axis represents the difference in internal resistance Rc (internal resistance after reaching the maximum value Imax) at the time of cranking with respect to the internal resistance Rin (internal resistance before reaching the maximum value Imax) at the time of sudden increase in the discharge current. The horizontal axis indicates the difference ΔVo between the open end voltages before and after starting the starter. As shown in the figure, the larger the difference ΔVo, the smaller the difference of the internal resistance Rc relative to the internal resistance Rin. For this reason, it is possible to estimate the internal resistance Rin when the discharge current suddenly increases from the difference ΔVo and the internal resistance Rc.

  That is, first, based on the voltage trajectory of the battery 30 shown by a solid line in FIG. 5, the voltage Vt of the battery 30 before starting the starter 40 and the minimum voltage Vbtm of the battery 30 accompanying the starter 40 startup are detected. The voltage drop amount ΔV of the battery 30 due to the starter 40 being activated is calculated. On the other hand, the internal resistance Rc indicated by the one-dot chain line in the figure can be calculated from the behavior of the current and voltage after the discharge current reaches the maximum value. Then, by using this and the difference ΔVo between the open end voltages before and after the starter 40 is started, the internal resistance Rin at the time of sudden increase of the discharge current indicated by a two-dot chain line in the figure can be estimated. Then, the maximum discharge current amount ΔImax of the battery 30 due to the starter 40 being activated can be estimated and calculated from the internal resistance Rin and the drop amount ΔV.

  FIG. 6 shows a procedure for estimating the maximum discharge current amount ΔImax according to the present embodiment. This process is executed by the ECU 50 as a trigger when the ignition switch 46 is turned on.

  In this series of processing, first, in step S10, the voltage Vt and current It of the battery 30 which are detection values of the voltage sensor 56 and the current sensor 52 are acquired. Since it remains in step S10 until it is determined in the subsequent step S12 that the starter 40 has been activated, the voltage Vt and the current It may be average values of a plurality of detection values during this period. If it is determined in the subsequent step S12 that the starter 40 has been activated, the current and voltage of the battery 30 after the starter 40 is activated are detected a plurality of times in step S14. In the subsequent step S16, the voltage drop amount ΔV of the battery 30 is calculated by subtracting the minimum voltage Vbtm of the battery 30 detected in step S14 from the voltage Vt acquired in step S10.

  In the subsequent step S18, the internal resistance Rc of the battery 30 during cranking is calculated. Here, a plurality of sets of voltages and currents detected at the same time in step S14 are used. The plurality of sets are set of detection values during a period in which the discharge current of the battery 30 has risen to the lower limit value of the detectable range of the current sensor 52. This can be performed, for example, by detecting that the current of the battery 30 once decreases and then increases beyond the lower limit value of the detectable range. Using these plural sets, the internal resistance Rc can be estimated by a known regression analysis or the like. That is, a linear equation model with current as an explanatory variable and voltage as an objective variable is calculated by the method of least squares, and a coefficient of the linear equation model is set as an internal resistance Rc. In addition, it is good also considering the said several group as a predetermined number of groups selected from these instead of making it all the groups of applicable detection value.

  In the subsequent step S20, the difference ΔVo between the open-end voltage of the battery 30 before and after the starter 40 is started is calculated. Here, the open circuit voltage Voaf after the starter 40 is started can be an intercept of the primary model calculated by the regression analysis. On the other hand, the open-circuit voltage Vove before starting the starter 40 assumes that the internal resistance does not change before the starter 40 starts and when the discharge current suddenly increases, and approximates this with the internal resistance Rc. By using Vt, it can be simply estimated by the equation “Vobe = Vt−Rc · It”. Therefore, the open-circuit voltage difference ΔVo can be calculated as “Vobe−Voaf”.

In the subsequent step S22, the internal resistance Rin at the time when the discharge current suddenly increases is estimated. Here, based on the correlation shown in FIG. 3, the internal resistance Rin is estimated by correcting the internal resistance Rc calculated in step S18 with the difference ΔVo calculated in step S20. . In the subsequent step S24, the voltage drop amount ΔV calculated in step S16 is divided by the internal resistance Rin estimated in step S22, whereby the maximum discharge current amount ΔImax of the battery 30 due to the starter 40 being started. Is calculated. In step S26, the maximum discharge current amount ΔImax and the internal resistance Rin are always stored in the memory holding device 51, and the detected values of the internal resistance Rc, current and voltage are erased. In addition, when the process of step S26 is completed, this series of processes is once complete | finished.
<B. Prediction process of battery 30 voltage immediately before automatic start>
FIG. 7 illustrates the transition of the voltage of the battery 30 before and after the idle stop. As shown in the figure, the voltage of the battery 30 is not stable and fluctuates due to the control of the output voltage of the power generator 20 before the idle stop. On the other hand, after the idle stop process is performed, the voltage of the battery 30 rapidly decreases in the process in which the control of the output voltage is stopped, but thereafter, the voltage of the battery 30 does not fluctuate up and down. It will gradually decrease gradually.

  Here, assuming that the stop period of the internal combustion engine 10 due to idle stop is the predetermined time T, the voltage Vbr at that time is defined as the voltage immediately before the automatic start. Here, the predetermined time T is set based on a time desired as a stop time of the internal combustion engine 10 when performing idle stop. The voltage Vbr can also be learned as a value when the stop period of the internal combustion engine 10 accompanying the idle stop process reaches a predetermined time T. However, in this case, when the automatic start process of the internal combustion engine 10 is performed before the elapse of the predetermined time T after the idle stop process, the above learning cannot be performed. For this reason, it may take time to learn the voltage Vbr in the above-described manner.

  Therefore, in the present embodiment, processing for predicting the voltage Vbr when the predetermined time T has elapsed is performed based on the voltage behavior during the stop period of the internal combustion engine 10 due to idle stop. In particular, in the present embodiment, as shown in FIG. 8, the prediction is performed based on the sampling value of the voltage after the absolute value of the voltage change rate ΔVs becomes equal to or less than the threshold value ΔVth. This is because it is considered that the voltage Vbr can be predicted easily and accurately after the change rate of the voltage of the battery 30 becomes equal to or lower than a predetermined value.

  FIG. 9 shows a procedure for creating a prediction formula used for prediction of the voltage Vbr according to the present embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle, for example.

  In this series of processing, first, in step S10, it is determined whether or not the internal combustion engine 10 is in a stopped state by idle stop processing. If it is determined that the vehicle is in the stopped state, it is determined in step S12 whether or not a voltage sampling permission condition for predicting the voltage Vbr is satisfied. Specifically, as shown in FIG. 8, it is determined whether or not the absolute value of the voltage change rate ΔVs is equal to or less than a threshold value ΔVth. If it is determined that the permission condition is satisfied, the voltage is sampled at predetermined time intervals in step S14.

  In a succeeding step S16, it is determined whether or not an automatic start condition is satisfied. This condition is obtained by subtracting the multiplication value of the maximum discharge current amount ΔImax and the internal resistance Rin from the condition that the user intends to drive the vehicle and the measured value of the voltage of the battery 30 during the stop period of the internal combustion engine 10. This is a logical sum condition with the condition that the obtained value is equal to or lower than a predetermined value higher than the threshold voltage Vth. If it is determined that the automatic start condition is satisfied, it is determined in step S18 whether or not the number of samples of the voltage sampled in step S14 is greater than a predetermined number N. This process is for determining whether or not it is possible to calculate a prediction formula that can accurately predict the voltage Vbr when the predetermined time T has elapsed from the automatic stop process. If an affirmative determination is made in step S18, a prediction formula is calculated in step S20. Here, for example, a prediction formula may be calculated using regression analysis based on a voltage sampling value. Here, as the prediction expression, a linear expression “at + b” of time t, an exponential function “a · exp (−bt) + c”, or the like may be assumed.

When the process of step S20 is completed or when a negative determination is made in steps S10, S12, S16, and S18, the series of processes is temporarily terminated.
<C. Processing for determining whether or not to execute idle stop>
FIG. 10 shows a procedure for determining whether or not to perform idle stop. This process is repeatedly executed by the ECU 50, for example, at a predetermined cycle.

  In this series of processes, first, in step S30, it is determined whether or not a basic condition for the idle stop process is satisfied. Here, the basic condition includes a condition that the vehicle is in a stopped state, a condition that the user does not display the intention to travel (the accelerator pedal is released, etc.), and the like. If it is determined that the basic condition is satisfied, it is determined in step S32 whether or not a prediction formula has been created. This is for determining whether or not the voltage Vbr can be predicted based on the prediction formula created by the process of step S20 of FIG. If it is determined that the prediction formula has been created, the created prediction formula is read in step S34.

  On the other hand, if it is determined in step S32 that the prediction formula has not yet been created, the reference curve is read in step S36. Here, the reference curve is a function for predicting the voltage Vbr instead of the prediction formula, and is a function having the time t as an independent variable and the voltage value as a dependent variable. This is pre-adapted and stored in the ECU 50 before product shipment.

  When the processes in steps S34 and S36 are completed, the voltage Vbr immediately before the automatic start is predicted in step S38. This can be calculated by substituting the predetermined time T as the time t in the prediction formula or the reference curve.

  In the subsequent step S40, the internal resistance Rin of the battery 30 and the maximum discharge current amount ΔImax are read out. In step S42, a voltage drop amount ΔVst due to automatic start is calculated as a product of the maximum discharge current amount ΔImax and the internal resistance Rin. In the subsequent step S44, the minimum voltage Vmin of the battery 30 accompanying the automatic start process is predicted. This can be calculated by subtracting the voltage drop amount ΔVst calculated in step S42 from the voltage Vbr predicted in step S38. In the subsequent step S46, it is determined whether or not a logical product condition of a condition that the predicted minimum voltage Vmin is larger than the threshold voltage Vth and a condition that the SOC is larger than the predetermined amount α is satisfied. This process is for determining whether to execute the idle stop process. If it is determined that the logical product condition is satisfied, idle stop is permitted in step S48.

  When the process of step S48 is completed or when a negative determination is made in steps S30 and S46, this series of processes is temporarily terminated.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When the basic condition for permitting the idle stop process is satisfied (step S30), the voltage Vbr of the battery 30 immediately before the automatic start process when the idle stop process is assumed is used as the internal combustion engine by the idle stop process before that. Prediction was made based on the detected value of the voltage of the battery 30 at the time of 10 stops, and whether or not the idle stop was executed was determined based on a value obtained by subtracting the voltage drop amount ΔVst of the battery 30 accompanying the automatic start process. Thereby, the stop period of the internal combustion engine 10 associated with the idle stop process can be set to an appropriate time, and a decrease in drivability can be avoided. In addition, since the automatic start is not performed unnecessarily, it is possible to suitably suppress the shortening of the life of the battery 30.

  (2) Based on a plurality of sampling values of the voltage of the battery 30 during the stop period of the internal combustion engine 10 due to automatic stop, a prediction formula for predicting the time change of the voltage of the battery 30 was calculated. Thereby, it is possible to predict the voltage immediately before the automatic start in the case where the stop period of the internal combustion engine 10 due to the automatic stop is longer than the sampling period of the sampling value.

  (3) The detection value used for the calculation of the prediction formula is assumed to be after the time point when the voltage drop speed of the battery 30 becomes a predetermined value or less in accordance with the automatic stop process. Thereby, a prediction formula can be calculated with high accuracy.

  (4) When the prediction formula is not calculated, the voltage Vbr is predicted using a predetermined function regardless of the detected value. Thereby, even if the prediction formula is not calculated, the minimum voltage Vmin of the battery 30 at the time of automatic start can be predicted.

  (5) Based on the detected voltage and current values over a predetermined period after the battery 30 reaches the minimum voltage Vbtm as the starter 40 is started in order to calculate the voltage drop amount ΔVst of the battery 30 associated with the automatic start process. The maximum discharge current amount ΔImax was calculated. Thereby, even when the current at the time when the voltage of the battery 30 becomes the minimum voltage Vbtm cannot be detected, the maximum discharge current amount ΔImax can be estimated and calculated.

  (6) The maximum discharge current amount ΔImax is defined as a difference in the discharge current amount of the battery 30 when the detected value of the voltage of the battery 30 becomes the minimum value by starting with respect to the discharge current amount before starting. Thereby, the voltage drop amount ΔVst of the battery 30 associated with the automatic start process can be suitably predicted.

  (7) The internal resistance Rin of the battery 30 during the period until the voltage of the battery 30 decreases to the minimum voltage due to the start is estimated, and the maximum discharge current amount ΔImax is estimated according to the estimated internal resistance Rin. Thereby, the maximum discharge current amount ΔImax can be suitably estimated.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 11 shows a procedure for determining whether or not to execute idle stop according to the present embodiment. This process is repeatedly executed by the ECU 50, for example, at a predetermined cycle. In FIG. 11, processes corresponding to the processes shown in FIG. 10 are given the same step numbers for convenience.

  As shown in the figure, in the present embodiment, when the processes of steps S34 and S36 are completed, the temperature of the prediction formula or the reference curve is corrected in step S50 before the process proceeds to step S38. This process is based on the fact that the voltage drop speed of the battery 30 depends on the temperature of the battery 30. Specifically, the voltage drop rate of the battery 30 increases as the temperature of the battery 30 decreases. For this reason, for example, when the current temperature is lower than the temperature of the battery 30 during the voltage sampling period used in the calculation of the prediction formula, a correction is performed to increase the voltage drop rate according to the prediction formula, and When the current temperature is higher than the temperature of the battery 30 during the sampling period, correction is performed such that the voltage drop rate according to the prediction formula is reduced.

  According to the present embodiment described above, the following effects can be obtained in addition to the above-described effects of the first embodiment.

  (8) The prediction formula was corrected based on the difference in temperature of the battery 30 between the sampling period of the voltage used for calculation of the prediction formula and the current time. Thereby, even when the temperature of the battery fluctuates, the prediction accuracy of the voltage Vbr can be maintained high.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the first embodiment, the voltage drop amount ΔVst is calculated by directly using the maximum discharge current amount ΔImax and the internal resistance Rin that are calculated when the ignition switch 46 is turned on. Here, when the change in the SOC is a high capacity, the internal resistance Rin is small in the change due to the capacity change. Further, the maximum discharge current amount ΔImax depends on the internal resistance Rin. Therefore, when the predetermined amount α shown in step S46 of FIG. 10 is set large from the viewpoint of extending the life of the battery 30, no correction is made to the maximum discharge current amount ΔImax or the internal resistance Rin. In both cases, the voltage drop amount ΔVst can be predicted with high accuracy. However, when the SOC threshold value is lowered in order to improve the frequency of idle stop, it is considered that the change in the internal resistance Rin with respect to the change in capacity increases, and the change in the maximum discharge current amount ΔImax also increases. Therefore, in the present embodiment, the maximum discharge current amount ΔImax and the internal resistance Rin are corrected based on the SOC.

  FIG. 12 shows a procedure for determining whether or not to execute idle stop according to the present embodiment. This process is repeatedly executed by the ECU 50, for example, at a predetermined cycle. In FIG. 12, processes corresponding to the processes shown in FIG. 10 are given the same step numbers for convenience.

  As shown in the figure, in the present embodiment, when the processes of steps S34 and S36 are completed, the prediction formula or the reference curve is corrected based on the SOC and the temperature in step S52 prior to proceeding to the process of step S38. . Here, the reason why the prediction formula or the reference curve is corrected based on the SOC is that the voltage drop speed of the battery 30 increases as the SOC decreases. For this reason, for example, when the current SOC is smaller than the SOC in the voltage sampling period used in calculating the prediction formula, correction is performed so that the voltage drop rate is increased according to the prediction formula, and the sampling is performed. When the current SOC is larger than the SOC in the period, correction is performed such that the voltage drop speed is reduced according to the prediction formula.

  When the process of step S40 is completed, prior to the process of step S42, the maximum discharge current amount ΔImax and the internal resistance Rin are corrected based on the SOC and the temperature. Here, when the current SOC is larger than the SOC in the current or voltage detection period used to calculate the maximum discharge current amount ΔImax, the maximum discharge current amount ΔImax is corrected to be increased, and the current SOC is greater. If it is smaller, the maximum discharge current amount ΔImax is corrected to decrease. In addition, when the current SOC is larger than the SOC in the current or voltage detection period used to calculate the internal resistance Rin, the internal resistance Rin is corrected to decrease, and when the current SOC is smaller, The internal resistance Rin is increased and corrected. Further, when the current temperature is higher than the temperature of the battery 30 during the current or voltage detection period used to calculate the internal resistance Rin, the internal resistance Rin is increased and corrected, and the current temperature is lower. In this case, the internal resistance Rin is corrected to decrease. In addition, when the current temperature is higher than the temperature of the battery 30 during the current and voltage detection period used to calculate the maximum discharge current amount ΔImax, the maximum discharge current amount ΔImax is corrected to decrease, If it is lower, the maximum discharge current amount ΔImax is corrected to be increased. This is because the internal resistance of the battery 30 and the starter 40 and the internal resistance of the electrical path (harness) between them increase as the temperature increases.

  In step S46a, it is determined whether or not a logical product condition of a condition that the minimum voltage Vmin is larger than the threshold voltage Vth and a condition that the SOC is larger than the predetermined amount β is satisfied. Here, the predetermined amount β is set to a value smaller than the predetermined amount α in the first embodiment.

  According to the present embodiment described above, the following effects can be obtained in addition to the effects of the first embodiment and the effects of the second embodiment.

  (9) The prediction formula was corrected based on the difference in SOC between the sampling period of the voltage used for calculation of the prediction formula and the current time. Thereby, even if the SOC varies, the prediction accuracy of the voltage Vbr can be maintained high.

  (10) The maximum discharge current amount ΔImax and the internal resistance Rin are corrected based on the difference in the temperature of the battery 30 between the detection period of the voltage and current used to calculate the maximum discharge current amount ΔImax and the internal resistance Rin and the current time. Thereby, the voltage drop amount ΔVst can be predicted with high accuracy.

  (11) The maximum discharge current amount ΔImax and the internal resistance Rin are corrected based on the difference in SOC between the detection period of the voltage and current used to calculate the maximum discharge current amount ΔImax and the internal resistance Rin and the current time. Thereby, the voltage drop amount ΔVst can be predicted with high accuracy.

(Fourth embodiment)
Hereinafter, the fourth embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 13 shows a procedure for determining whether or not to execute idle stop according to the present embodiment. This process is repeatedly executed by the ECU 50, for example, at a predetermined cycle. In FIG. 13, processes corresponding to the processes shown in FIG. 10 are given the same step numbers for convenience.

  As shown in the figure, in this embodiment, when it is determined in step S32 that the prediction formula has not yet been calculated, it is determined in step S56 whether or not the SOC is larger than a predetermined amount α. Allow idle stop. Here, since the situation where the prediction formula has not been calculated yet is considered to be immediately after product shipment, it is considered that there is no problem even if the battery 30 is new and the idle stop is executed. In this case, it is considered better to secure an opportunity to create a prediction formula by executing idle stop. For this reason, in this embodiment, idle stop is permitted when the SOC is larger than the predetermined amount α in a situation where the prediction formula has not yet been calculated.

  According to this embodiment described above, in addition to the effects (1) to (3) and (5) to (7) of the first embodiment, the following effects can be obtained. Become.

  (12) In a situation where the prediction formula has not yet been calculated, when the SOC is larger than the predetermined amount α, the idle stop process is executed. As a result, an opportunity to calculate the prediction formula can be quickly secured.

(Fifth embodiment)
Hereinafter, a fifth embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

  In the present embodiment, as shown in FIG. 14, when the absolute value of the change rate of the polarization correlation amount P (polarization change rate ΔP) is equal to or less than the threshold value ΔPth, voltage sampling for calculating the prediction formula is permitted. . Here, the polarization change rate ΔP is a parameter having a correlation with the voltage change rate.

  FIG. 15 shows a procedure for calculating the polarization correlation amount P. This process is repeatedly executed by the ECU 50 at a predetermined cycle, for example.

  In this series of processing, first, in step S60, the current I (n) of the battery 30 is acquired. Here, “n” is a parameter indicating a sampling number. In a succeeding step S62, it is determined whether or not the previous polarization correlation amount P (n-1) is zero or more. This process is for determining whether the influence of charging remains in the battery 30 or whether the influence of discharging remains stronger. This is provided in view of the fact that the rate of elimination of the polarization state differs between the case where the effect of charging remains strong in the battery 30 and the case where the effect of discharge remains strong.

  If the previous polarization correlation amount P (n-1) is greater than or equal to zero in step S62, it is determined that the effect of charging remains stronger. In step S64, the diffusion time constant τ is set to the charging time constant. Let it be a constant τc. On the other hand, when a negative determination is made in step S62, it is determined that the influence of the discharge remains stronger, and in step S66, the diffusion time constant τ is set as the discharge time constant τd. Here, the discharge time constant τd is set to a value smaller than the charge time constant τc. This is a result that quantitatively represents that the charge history is more easily resolved.

  When the processes of steps S64 and S66 are completed, the process proceeds to step S68. In step S68, a polarization correlation amount P (n) is calculated. Here, the polarization correlation amount P (n) is calculated by adding two terms to the previous polarization correlation amount P (n−1). Here, the first term “γ · I (n) · dt” is for quantifying the charge / discharge history. Specifically, a term for calculating a time integral value of the amount “γ · I (n)” corresponding to the current I (n) of the battery 30 based on the cycle dt of this series of processing and the charging efficiency γ. is there. Here, since the current I (n) is positive at the time of charging and negative at the time of discharging, the charge / discharge history can be quantified by a time integral value corresponding to the current I (n). Note that the charging efficiency γ may have a different value depending on the sign of the current I (n), but in the present embodiment, it is simply a fixed value that does not change regardless of the sign of the current I (n). .

  The other term “−P (n−1) · dt / τ” is for quantifying the attenuation effect of the polarization state (the diffusion phenomenon of sulfuric acid near the electrode of the battery 30). Here, attenuation of the current polarization state is expressed by using the amount of the opposite sign to the previous polarization correlation amount P (n−1).

  In addition, when the process of step S68 is completed, this series of processes is once complete | finished.

(Sixth embodiment)
Hereinafter, the sixth embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, as shown in FIG. 16, a period in which the internal resistance Rc of the battery 30 in the sampling period is assumed to approximate the internal resistance Rin is used as the current sampling period for estimating the maximum discharge current amount ΔImax. . According to this, the maximum discharge current amount ΔImax can be estimated by “(Vt−Vbtm) / Rc”. Thereby, the maximum discharge current amount ΔImax and the internal resistance Rin can be easily calculated by adapting the sampling period.

(Seventh embodiment)
Hereinafter, the seventh embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, as shown in FIG. 17, the discharge current amount of the battery 30 decreases to zero after reaching the maximum value Imax. At this time, if the slope Ra of the straight line connecting the time point when the discharge current becomes maximum (Imax, Vbtm) and the time point when the discharge current becomes zero (0, Vo) can be found, it is based on the minimum voltage Vbtm and the open-circuit voltage Vo. The maximum discharge current amount ΔImax can be estimated. Here, the slope of the straight line (internal resistance Rc) approximating the change in voltage with respect to the change in current in the region surrounded by the two-dot chain line in the figure approximates the slope Ra. That is, depending on the specifications of the starter 40, the internal combustion engine 10, and the current sensor 52, the internal resistance Rc calculated from the current and voltage sampling values in a specific region within the region detectable by the current sensor 52 can be approximated to the slope Ra. . Therefore, in this case, the maximum discharge current amount ΔImax can be easily calculated by adapting the specific region (the region surrounded by the two-dot chain line in the figure).

  In this case, the processing related to the calculation of the voltage drop amount ΔVst in step S42 of FIG. 10 is set as a value estimated by a known method as the internal resistance Rin, or set in advance before product shipment. What is necessary is just to use a value (default value).

(Other embodiments)
Each of the above embodiments may be modified as follows.

  -You may change 2nd, 3rd embodiment by the change of 4th Embodiment with respect to the said 1st Embodiment.

  -You may change 2nd-4th embodiment by the change of 5th Embodiment with respect to the said 1st Embodiment.

  In the third embodiment, the maximum discharge current amount ΔImax may be corrected according to the internal resistance Rin instead of the temperature correction. This is based on the fact that the internal resistance Rin is a parameter having a correlation with temperature.

  In the third embodiment, the maximum discharge current amount ΔImax may be corrected by only one of SOC and temperature.

  In the third embodiment, the internal resistance Rin may be corrected by only one of SOC and temperature.

  In the third embodiment, the prediction formula may be corrected only by the SOC.

  -You may change the said 2nd-5th embodiment by the change of the 6th, 7th embodiment with respect to the said 1st Embodiment.

  The predicting means for predicting the voltage of the battery 30 immediately before the automatic start process assuming an idle stop is not limited to using a prediction formula. For example, when the idle stop continues for a predetermined time T, the voltage of the battery 30 at that time may be stored as a predicted value. In this case, it is desirable to correct the predicted value according to at least one of the temperature of the battery 30 and the SOC.

  In each of the above embodiments, the maximum discharge current amount ΔImax is calculated using the ignition switch 46 as a trigger, but the present invention is not limited to this. For example, it may be calculated during the automatic start process. Further, for example, the maximum discharge current amount ΔImax is not limited to the difference between the discharge current amount when the voltage of the battery 30 becomes the minimum value with the start and the discharge current amount before the start process, and the battery 30 with the start. The amount of discharge current itself when the voltage becomes the minimum value may be used. Further, for example, the maximum discharge current amount ΔImax may be a value that is predetermined and stored before product shipment. However, in this case, it is particularly desirable to correct the discharge current amount ΔImax based on the temperature of the battery 30 and the SOC.

  In the first to sixth embodiments, the internal resistance Rin is calculated using the ignition switch 46 as a trigger, but the present invention is not limited to this. For example, it may be calculated during the automatic start process. Further, for example, the internal resistance Rin may be a value that is predetermined and stored before product shipment. However, in this case, it is particularly desirable to correct the internal resistance Rin based on the temperature of the battery 30 and the SOC.

  Instead of storing the maximum discharge current amount ΔImax and the value of the internal resistance Rin, the voltage drop amount ΔVst itself accompanying the automatic start may be stored. Here, the voltage drop amount ΔVst may be the voltage drop amount ΔV in step S16 of FIG. 6, or may be corrected according to the temperature and the SOC.

  The detection value of the voltage used for calculating the prediction formula for predicting the voltage Vbr immediately before the automatic start process is not limited to that in the stop period of the internal combustion engine 10 associated with the automatic stop process before that. For example, it may be during a stop period when the internal combustion engine 10 is stopped by turning off the ignition switch. Even in this case, it is considered that the voltage of the battery 30 decreases because the current consumption of the battery 30 does not become zero during the post-processing of the ECU 50. Therefore, a phenomenon that is very similar to a decrease in voltage during the stop period of the internal combustion engine 10 due to the automatic stop process has occurred. Therefore, it is also possible to calculate a prediction formula based on the detected value of the voltage during this period. .

  -The acquisition method of the open end voltage Vo before starter starting is not restricted to what was illustrated in said each embodiment. For example, the open end voltage before startup may be estimated by regression analysis based on the detected values of the voltage and current of the battery 30 when the internal combustion engine 10 is stopped.

  In the automatic starting process of the internal combustion engine 10 after the idle stop control, the starting means for applying the initial rotation to the crankshaft 12 of the internal combustion engine 10 is not limited to the starter 40. For example, a motor generator dedicated to automatic start may be provided separately from the starter 40. In this case, it is desirable to calculate the maximum discharge current amount ΔImax based on the current and voltage of the battery 30 when the internal combustion engine 10 is automatically started by the motor generator.

  The internal combustion engine is not limited to the port injection type spark ignition type internal combustion engine, and may be, for example, a cylinder injection type spark ignition type internal combustion engine. Further, it may be a compression ignition type internal combustion engine such as a diesel engine.

1 is a system configuration diagram according to a first embodiment. FIG. The figure which shows the prediction method of the battery minimum voltage accompanying the automatic start concerning the embodiment. The figure which shows transition of the battery discharge current at the time of starting. The figure explaining the estimation principle of the internal resistance at the time of the maximum discharge current concerning the said embodiment. The figure explaining the presumed principle of the maximum discharge current concerning the embodiment. The flowchart which shows the procedure of the estimation process of the maximum discharge current concerning the embodiment. The figure explaining the estimation method of the battery voltage just before the automatic start concerning the embodiment. The figure which shows the sampling start condition of the voltage used for calculation of the prediction formula of the battery voltage concerning the embodiment. The flowchart which shows the procedure of the calculation process of the prediction formula concerning the embodiment. The flowchart which shows the procedure of the idle stop process concerning the embodiment. The flowchart which shows the procedure of the idle stop process concerning 2nd Embodiment. The flowchart which shows the procedure of the idle stop process concerning 3rd Embodiment. The flowchart which shows the procedure of the idle stop process concerning 4th Embodiment. The figure which shows the sampling start conditions of the voltage used for calculation of the prediction formula of the battery voltage concerning 5th Embodiment. 6 is a flowchart showing a procedure of a polarization correlation amount calculation process according to the embodiment. The figure explaining the estimation principle of the maximum discharge current concerning 6th Embodiment. The figure explaining the estimation principle of the maximum discharge current concerning 7th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Electric power generation apparatus, 30 ... Battery, 40 ... Starter (one embodiment of a starting means), 50 ... ECU (one embodiment of the automatic stop start device of an internal combustion engine).

Claims (14)

  1. In an automatic stop / start apparatus for an internal combustion engine that performs an automatic stop process of an internal combustion engine to which an initial rotation is applied by a starter that uses a vehicle-mounted battery as a power source, and an automatic start process after the automatic stop process,
    Voltage acquisition means for acquiring a detected value of the voltage of the battery in a stop period of the internal combustion engine;
    After the acquisition by the voltage acquisition means, the battery immediately before the automatic start process when the automatic stop process is assumed on the condition that it is determined that the condition that the user does not display the intention to travel is satisfied Predicting means for predicting the voltage based on the detection value acquired by the voltage acquiring means;
    Determination means for determining whether or not to execute the automatic stop process based on a value obtained by subtracting a predicted value of the voltage drop amount of the battery accompanying the automatic start process from the predicted voltage;
    An automatic stop / start apparatus for an internal combustion engine, wherein the voltage of the battery immediately before the automatic start process is a voltage assuming that the stop period of the internal combustion engine is a time having a predetermined length .
  2.   The prediction means includes means for calculating a prediction formula for predicting a temporal change in the battery voltage based on a plurality of sampling values of the battery voltage during the stop period, and performs the prediction based on the prediction formula. The automatic stop and start device for an internal combustion engine according to claim 1.
  3.   3. The automatic internal combustion engine according to claim 2, wherein the detection value used for calculation of the prediction formula is a value after the time when the voltage drop speed of the battery becomes a predetermined value or less as the internal combustion engine is stopped. Stop starter.
  4.   3. The determination unit according to claim 2, wherein when the prediction formula is not calculated, the determination unit performs the determination by performing the prediction using a predetermined function regardless of the detection value. 3. An automatic stop and start device for an internal combustion engine according to 3.
  5.   The determination means determines that the automatic stop process is to be executed on the condition that a value obtained by subtracting a predicted value of the battery voltage drop associated with the automatic start process from the predicted voltage is equal to or greater than a predetermined value. If the prediction formula is not calculated, the state of charge of the battery is a predetermined state regardless of whether or not the condition that the subtracted value is equal to or greater than a predetermined value is satisfied. 4. The automatic stop and start device for an internal combustion engine according to claim 2, wherein it is determined that the automatic stop process is executed on the condition of
  6.   6. The internal combustion engine automatic according to claim 1, wherein the predicting unit takes into account the temperature of the battery at the time of acquisition of the detected value and at the present time in the prediction. Stop starter.
  7.   The internal combustion engine according to any one of claims 1 to 6, wherein the predicting unit takes into account the state of charge of the battery at the time of acquisition of the detected value and at the present time in the prediction. Automatic stop start device.
  8.   The automatic stop / start apparatus for an internal combustion engine according to any one of claims 1 to 7, wherein the predicted value of the voltage drop amount of the battery is variably set according to the temperature of the battery.
  9.   The automatic stop / start apparatus for an internal combustion engine according to any one of claims 1 to 8, wherein a predicted value of the voltage drop amount of the battery is variably set according to a state of charge of the battery.
  10. Based on the detected value of the battery voltage and the detected value of the discharge current of the battery in a predetermined period after the detected value of the battery voltage reaches the minimum value due to the starting of the internal combustion engine, the voltage of the battery by the starting is determined. A discharge current acquisition means for acquiring information related to the amount of discharge current of the battery when the detected value of
    The said determination means calculates the predicted value of the voltage drop amount of the said battery accompanying the said automatic start process based on the information acquired by the said discharge current acquisition means, The any one of Claims 1-9 characterized by the above-mentioned. An automatic stop and start device for an internal combustion engine according to the item.
  11.   The discharge current acquisition means is a discharge current of the battery when the detected value of the voltage of the battery becomes a minimum value due to the start with respect to the discharge current amount before the start as the maximum discharge current amount of the battery for the start 11. The automatic stop and start device for an internal combustion engine according to claim 10, wherein the difference in amount is estimated.
  12.   The discharge current acquisition means estimates the maximum discharge current amount according to the estimated internal resistance while estimating the internal resistance of the battery during a period until the voltage of the battery decreases to the minimum voltage due to the start-up. The automatic stop and start device for an internal combustion engine according to claim 11.
  13. The discharge current acquisition means calculates the internal resistance of the battery based on a plurality of sets of detected values related to the battery voltage and the battery discharge current in a predetermined period after the battery voltage is reduced to the minimum voltage by the start-up. A means for estimating, a maximum decrease amount of the battery voltage based on a difference between a value before the start by the start means and a minimum value by the start of the detected value of the battery voltage, and the estimated internal resistance Based on the above, the maximum discharge current amount is estimated,
    The predetermined period is set to a period in which the internal resistance of the battery is assumed to approximate the internal resistance of the battery in a period until the voltage of the battery is reduced to the minimum voltage by the start. An automatic stop and start device for an internal combustion engine according to claim 12.
  14. The discharge current acquisition means calculates the internal resistance of the battery based on a plurality of sets of detected values related to the battery voltage and the battery discharge current in a predetermined period after the battery voltage is reduced to the minimum voltage by the start-up. A means for estimating, based on a difference between a minimum voltage due to starting by the starting means and a predetermined voltage after reaching the minimum voltage with respect to a detected value of the voltage of the battery, and the estimated internal resistance, To estimate the maximum discharge current,
    The predetermined period is a period in which the internal resistance of the battery is assumed to approximate a slope of a straight line connecting a time point when the voltage of the battery decreases to the minimum voltage with the start and a time point when the voltage of the battery increases to the predetermined voltage. 12. The automatic stop and start device for an internal combustion engine according to claim 11, wherein the automatic stop and start device is set.
JP2008185577A 2008-07-17 2008-07-17 Automatic stop and start device for internal combustion engine Active JP5026362B2 (en)

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CN102725499B (en) * 2010-09-22 2014-01-15 丰田自动车株式会社 Control device for internal combustion engine and control method for internal combustion engine
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US9534574B2 (en) 2012-12-27 2017-01-03 Toyota Jidosha Kabushiki Kaisha Vehicle, control apparatus and control method
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