JP2013161693A - Device and method of estimating battery liquid temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method of estimating a battery liquid temperature capable of estimating a liquid temperature of a battery with high accuracy even in the case that a peripheral temperature of the battery is not detected during the stop of an internal combustion engine.SOLUTION: On the basis of a peripheral temperature of a battery 11 at a time point when an engine 10 was stopped, the peripheral temperature of the battery 11 at a time point when the engine 10 was started up, and a battery peripheral temperature interpolation type, the peripheral temperature of the battery 11 during the stop of the engine 10 is interpolated. On the basis of the interpolated peripheral temperature of the battery 11, an estimated liquid temperature of the battery 11 at the time point when the engine 10 was stopped, and a battery liquid temperature estimation type, a liquid temperature initial value of the battery 11 at the time when the engine 10 was started up is estimated.

Description

  The present invention relates to an estimation device and an estimation method for estimating a battery fluid temperature.

  As the temperature of the battery, the temperature of the battery solution (electrolyte) filling the inside of the battery is important. However, since the battery liquid is a strongly acidic liquid, it is difficult to detect the liquid temperature by directly putting a temperature sensor into the liquid. For this reason, as disclosed in Patent Document 1, the ambient temperature of the battery is alternatively detected by a temperature sensor disposed around the battery, and the battery liquid temperature is calculated based on the detected battery ambient temperature and the battery fluid temperature estimation formula. The temperature is estimated. Specifically, the battery liquid temperature at a certain time is calculated by weighted averaging of the battery ambient temperature at a certain time and the battery liquid temperature estimated at the previous time.

  In order to accurately estimate the battery fluid temperature during operation of the internal combustion engine based on the battery fluid temperature estimation formula as described above, it is necessary to accurately set the initial value of the battery fluid temperature at the time when the internal combustion engine is started. There is. In Patent Document 1, an electronic control unit (ECU) is periodically activated while the internal combustion engine is stopped to detect the ambient temperature of the battery. Based on the periodically detected ambient temperature of the battery, the battery liquid temperature estimated when the internal combustion engine was stopped, and the battery liquid temperature estimation formula, the battery at the time when the internal combustion engine was started The liquid temperature initial value is estimated.

JP 2009-146754 A

  However, when the electronic control unit (ECU) is activated to acquire the ambient temperature of the battery while the internal combustion engine is stopped, there is a problem that the remaining capacity of the battery decreases.

  The present invention has been made in view of the above circumstances. The present invention relates to a battery liquid temperature estimation device and an estimation method capable of accurately estimating the battery liquid temperature during operation of the internal combustion engine even when the ambient temperature of the battery is not detected while the internal combustion engine is stopped. The main purpose is to provide

  The present invention employs the following means in order to solve the above problems.

  The invention according to claim 1 is a battery fluid temperature estimation device that is applied to a vehicle including an internal combustion engine, a battery, and a temperature sensor that detects an ambient temperature of the battery, and that estimates a fluid temperature of the battery. The ambient temperature detected or interpolated by the temperature sensor at the first time point, the liquid temperature estimated at the second time point before the first time point, and the battery liquid temperature estimation formula And a battery liquid temperature estimating means for sequentially estimating the liquid temperature at the first time point, and the ambient temperature and the battery liquid temperature estimating means detected by the temperature sensor when the engine is stopped. Storage means for storing the liquid temperature estimated by the above, and the surroundings detected by the temperature sensor when the engine is started after the engine is stopped Battery ambient temperature interpolation means for interpolating the ambient temperature during stoppage of the engine based on the ambient temperature stored in the storage means and the battery ambient temperature interpolation formula, and the battery liquid The temperature estimation means starts the engine based on the ambient temperature interpolated by the battery ambient temperature interpolation means, the liquid temperature stored by the storage means, and the battery liquid temperature estimation formula. The initial liquid temperature of the battery at the time is estimated.

  According to the above configuration, the battery ambient temperature detected by the temperature sensor at the first time point, the battery liquid temperature estimated at the second time point before the first time point, and the battery liquid temperature estimation formula are used. Thus, the battery liquid temperature at the first time point is sequentially estimated.

  Further, when the internal combustion engine is started after the internal combustion engine is stopped, the ambient temperature of the battery detected by the temperature sensor, and the ambient temperature of the battery detected by the temperature sensor when the internal combustion engine is stopped, Based on the battery ambient temperature interpolation formula, the ambient temperature of the battery while the internal combustion engine is stopped is interpolated. That is, even when the ambient temperature of the battery is not measured while the internal combustion engine is stopped, the ambient temperature of the battery while the internal combustion engine is stopped can be obtained with high accuracy by interpolation when the internal combustion engine is started.

  Further, based on the interpolated battery ambient temperature, the battery liquid temperature estimated when the internal combustion engine is stopped, and the battery liquid temperature estimation formula, the battery liquid temperature during the stop of the internal combustion engine is successively determined. Estimated. As a result, even if the ambient temperature of the battery is not detected while the internal combustion engine is stopped, the initial liquid temperature of the battery can be estimated with high accuracy when the internal combustion engine is started. Then, by using the liquid temperature initial value estimated with high accuracy, the liquid temperature during operation of the internal combustion engine can also be estimated with high accuracy.

  The invention according to claim 5 is a battery fluid temperature estimation method that is applied to a vehicle including an internal combustion engine, a battery, and a temperature sensor that detects the ambient temperature of the battery, and that estimates the fluid temperature of the battery. The ambient temperature detected or interpolated by the temperature sensor at the first time point, the liquid temperature estimated at the second time point before the first time point, and the battery liquid temperature estimation formula Based on the battery temperature estimation step for sequentially estimating the liquid temperature at the first time point, and the ambient temperature and the battery fluid temperature estimation step detected by the temperature sensor when the engine is stopped A storage step for storing the liquid temperature estimated in step (b), and the ambient temperature detected by the temperature sensor when the engine is started after the engine is stopped. A battery ambient temperature interpolation step of interpolating the ambient temperature while the engine is stopped based on the ambient temperature stored in the storage step and a battery ambient temperature interpolation formula, and the battery fluid temperature estimation In the process, at the time when the engine is started based on the ambient temperature interpolated in the battery ambient temperature interpolation process, the liquid temperature stored in the storage process, and the battery liquid temperature estimation formula The liquid temperature initial value of the battery is estimated.

  According to the said process, there can exist an effect similar to the invention described in Claim 1.

The schematic diagram which shows schematic structure of the vehicle system which concerns on this embodiment. The time chart which shows the relationship between liquid temperature and ambient temperature. A time chart showing the liquid temperature and ambient temperature when the engine is stopped. The flowchart which shows the process sequence which estimates liquid temperature. The flowchart which shows the interpolation processing subroutine of ambient temperature in case of an engine stop. The flowchart which shows the estimation process subroutine of the liquid temperature initial value at the time of engine starting. The flowchart which shows the liquid temperature estimation processing subroutine during engine operation.

  Hereinafter, an embodiment embodied in an estimation device that estimates a liquid temperature of a battery mounted on a vehicle will be described with reference to the drawings. This vehicle is a vehicle using an internal combustion engine as a travel drive source. The vehicle performs idle stop control that automatically stops and restarts the internal combustion engine when a predetermined condition is satisfied. First, a schematic configuration of a vehicle system in which a battery and a battery liquid temperature estimation device are mounted will be described with reference to FIG.

  As shown in the figure, the vehicle is opened and closed by an engine (internal combustion engine) 10, a starter (motor) 12, an alternator (generator) 13, an auxiliary device 14 such as a car stereo or an air conditioner, and an ignition key operation by a driver. An ignition switch 16 and a relay 22 are mounted.

  A starter 12 is connected to the crankshaft of the engine 10, and an alternator 13 is connected via connecting means such as a belt. The engine 10 performs fuel injection and ignites the fuel / air mixture in the combustion chamber to burn the mixture. The operation of the engine 10 is performed by an engine ECU 15 described later.

  The starter 12 is connected to the battery 11 via a relay 22. The starter 12 is driven at the time of start by the driver's ignition key operation and at the time of automatic restart by execution of idle stop control. In the case of starting by the driver's ignition key operation, when the ignition key reaches the start position, the start switch of the ignition switch 16 is closed and the relay 22 is energized. As a result, the relay circuit between the battery 11 and the starter 12 is closed, and power is supplied from the battery 11 to the starter 12. The starter 12 is driven by power supply and starts the engine 10. In the case of automatic restart by execution of idle stop control, the relay 22 is controlled by an idle stop ECU 18 described later when a predetermined condition is satisfied. As a result, the relay circuit between the battery 11 and the starter 12 is closed, and the starter 12 starts the engine 10.

  The alternator 13 is connected to the crankshaft of the engine 10 via connecting means such as a belt, and is driven to generate electric power as the engine 10 rotates. The generated electric power is supplied to the battery 11 and the auxiliary machine 14.

  The auxiliary machine 14 receives power supply from the alternator 13 and the battery 11. Specifically, when the ignition key is moved to the accessory position by the driver's operation, the accessory switch of the ignition switch 16 is closed. Accordingly, the relay circuit between the battery 11 and the auxiliary machine 14 is closed, and electric power is supplied from the battery 11 to the auxiliary machine 14. Further, when the engine is stopped due to the execution of the idle stop control, the relay 22 is controlled by the idle stop ECU 18, and the relay circuit between the battery 11 and the auxiliary machine 14 is closed. Then, electric power is supplied from the battery 11 to the auxiliary machine 14.

  As the battery 11, for example, a 12V lead storage battery is employed. The battery 11 supplies power to the starter 12 and the auxiliary machine 14 as described above, and also supplies power to the engine ECU 15 and the idle stop ECU 18. Further, the battery 11 includes a temperature sensor 17 that measures the ambient temperature of the battery 11. The ambient temperature measured by the temperature sensor 17 is taken into the idle stop ECU 18. The battery 11 and the temperature sensor 17 are disposed in the engine compartment.

  The vehicle system also includes both an ECU (electronic control unit) of the engine ECU 15 and the idle stop ECU 18, a vehicle speed sensor 19 that detects the vehicle speed, a shift position sensor 20 that detects the position of the shift lever, and a brake that detects the depression of the brake. Various sensors of the sensor 21 are provided. Each ECU is composed mainly of a microcomputer including a central processing unit (CPU), a storage device (ROM and RAM), and a timer counter, and executes various control programs stored in the ROM. Each ECU receives and activates a signal when the ignition key is in the ignition (IG) position by the driver's operation. Each ECU is operated by electric power supplied from the battery 11. The engine ECU 15 and the idle stop ECU 18 can communicate with each other bidirectionally.

  When the engine ECU 15 is activated, the engine ECU 15 transmits a signal for driving the fuel injection system and the ignition system to the engine 10. Further, even when the engine ECU 15 receives an engine restart signal from the idle stop ECU 18, it similarly transmits a signal to the engine 10. Further, the engine ECU 15 determines the operating state of the engine 10 and controls the fuel injection amount, the fuel injection timing, and the like according to the operating state.

  The idle stop ECU 18 receives the detection values of the vehicle speed sensor 19, the shift position sensor 20, and the brake sensor 21 that are taken into the engine ECU 15 from the engine ECU 15. Then, it is determined whether the automatic stop condition and the automatic restart condition of the engine 10 are satisfied. When it is determined that the automatic stop condition is satisfied, a stop signal is transmitted to the engine ECU 15. When it is determined that the automatic restart condition is satisfied, a restart signal is transmitted to the engine ECU 15.

  In the present embodiment, the idle stop ECU 18 corresponds to a battery fluid temperature estimation device including battery fluid temperature estimation means, battery ambient temperature interpolation means, and storage means.

  Next, the relationship between the liquid temperature of the battery 11 and the ambient temperature of the battery 11 (hereinafter, abbreviated as liquid temperature and ambient temperature) will be described with reference to FIG. The ambient temperature is the ambient temperature around the battery 11. The heat capacity of the battery fluid is greater than the heat capacity of the atmosphere. Therefore, there is a delay in heat transfer between the battery fluid and the atmosphere around the battery. As shown in the figure, when the engine 10 is in operation, the battery fluid absorbs heat from the surrounding atmosphere whose temperature has been increased by the heat of the engine 10 or the like. On the other hand, when the engine 10 is stopped, the battery fluid radiates heat to the surrounding atmosphere where the temperature lowers faster than the battery fluid. If the stop time of the engine 10 is long, both the liquid temperature and the ambient temperature converge to the outside temperature.

In general, since it is difficult to directly measure the liquid temperature, the ambient temperature is measured instead. Then, the liquid temperature is estimated on the basis of the ambient temperature and the battery liquid temperature estimation formula considering the heat transfer delay. The battery fluid temperature estimation formula used at that time is generally
U (n) = {T (n) + (X-1) U (n-1)} / X
It is represented by Here, n: sampling number, U (n): liquid temperature, T (n): ambient temperature, X: estimated constant. The liquid temperature U (n) at the first time point (n) is the liquid temperature estimated at the ambient temperature T (n) at the first time point (n) and at the second time point (n-1) before the first time point. Calculated by weighted average of U (n-1).

  In order to estimate the liquid temperature during operation of the engine 10, it is necessary to set the liquid temperature initial value U (0) of the battery 11 at the time when the engine 10 is started. The liquid temperature initial value U (0) is calculated based on the battery liquid temperature estimation formula and the ambient temperature when the engine 10 is stopped. However, when the engine 10 is manually stopped, the idle stop ECU 18 cannot acquire the ambient temperature because it is in the sleep state. When the idle stop ECU 18 is activated to acquire the ambient temperature, the remaining capacity of the battery 11 decreases. Note that when the engine 10 is stopped by automatic stop, the stop time is short, so that the remaining capacity of the battery 11 does not decrease even if the ambient temperature is detected by the temperature sensor 17 while the engine 10 is stopped.

  Therefore, when the engine 10 is started, the ambient temperature when the engine 10 is stopped is interpolated by the battery ambient temperature interpolation formula. Then, based on the interpolated ambient temperature and the battery liquid temperature estimation formula, an initial liquid temperature value of the battery 11 at the time of starting the engine 10 is estimated. Further, the liquid temperature during operation of the engine 10 is estimated based on the estimated initial liquid temperature value, the ambient temperature detected by the temperature sensor 17 and the battery liquid temperature estimation formula.

  Next, an outline of a processing procedure for estimating the liquid temperature (liquid temperature initial value U) when the engine 10 is started will be described with reference to FIG. First, the ambient temperature when the engine 10 is stopped is interpolated by the battery ambient temperature interpolation formula. Here, the elapsed time from the time when the engine 10 is stopped is t, the ambient temperature detected when the engine 10 is stopped is Toff, the ambient temperature detected when the engine 10 is started is Ton, the engine Let tp be the elapsed time when 10 is started. The battery ambient temperature interpolation equation is an equation that approximates the ambient temperature between the start point and the end point with Toff (t = 0) as the start point and Ton (t = tp) as the end point.

As the battery ambient temperature interpolation formula, when Tb: ambient temperature to be interpolated, t: elapsed time since the time when the engine 10 was stopped, β: predetermined coefficient, α: coefficient, γ: coefficient,
Tb = αexp (−βt) + γ
The following formula can be adopted. The predetermined coefficient β is statistically obtained, and the coefficient α and the coefficient γ are calculated based on an equation obtained by substituting the ambient temperature and elapsed time at the start point and the end point into the above formula. The curve indicated by the dotted line in FIG. 3 indicates the ambient temperature that is interpolated using the above mathematical formula.

  The degree of approximation between the ambient temperature calculated from such a mathematical expression and the actual ambient temperature while the engine 10 is stopped is high. Therefore, when the above equation is adopted as the battery ambient temperature interpolation equation, the ambient temperature while the engine 10 is stopped can be accurately interpolated.

  Next, the initial value of the liquid temperature when the engine 10 is started, that is, the initial value of the liquid temperature during the operation of the engine 10 is estimated. The liquid temperature Uoff estimated at the time when the engine 10 is stopped is set to an initial value Ub (0), and the liquid during the stop of the engine 10 is sequentially determined based on the interpolated Tb and the battery liquid temperature estimation formula described above. The temperature Ub (m) (m (0 ≦ m ≦ me): sampling number) is estimated. Then, the liquid temperature Ub (me) estimated at the time when the engine 10 is started is set as the liquid temperature initial value U (0) at the time when the engine 10 is started. Note that me is a sampling number when the engine 10 is started.

  Hereinafter, a processing procedure for estimating the liquid temperature during operation of the engine 10 will be specifically described with reference to FIGS. FIG. 4 is a main routine for estimating the liquid temperature. First, in S1, the ambient temperature Toff detected by the temperature sensor 17 and the estimated liquid temperature Uoff are stored in the storage device when the engine 10 is stopped. Moreover, the measurement of the elapsed time t from the time when the engine 10 is stopped is started using the timer counter. Next, in S2, it is determined whether the engine 10 has been started. If it is not determined that the engine has been started (NO), the system waits until it is determined that the engine has been started. If it is determined that the engine has been started (YES), the process proceeds to S3.

  In S3, a subroutine for interpolating the ambient temperature Tb when the engine 10 shown in FIG. 5 is stopped is executed. In this subroutine, first, an elapsed time tp from when the engine 10 is stopped to when it is started is read and acquired (S31). Further, the ambient temperature Ton detected by the temperature sensor 17 at the time when the engine 10 is started is acquired (S32).

  Next, Toff stored in the storage device is read. Then, the ambient temperature Tb = Toff and the elapsed time t = 0 (information when the engine 10 is stopped) are substituted into the battery ambient temperature interpolation formula (S33). Further, the ambient temperature Tb = Ton and the elapsed time t = tp (information when the engine 10 is started) are substituted into the battery ambient temperature interpolation formula (S34). Then, solve the coupled equation of the formula that substitutes the information at the time when the engine 10 is stopped into the battery ambient temperature interpolation formula and the formula that substitutes the information at the time when the engine 10 is started into the battery ambient temperature interpolation formula, The coefficients α and γ of the battery ambient temperature interpolation formula are calculated (S35). Thereby, the battery ambient temperature interpolation formula is determined.

  Subsequently, in S36, the ambient temperature Tb (m) when the engine 10 is stopped is calculated at a predetermined sampling interval using the determined battery ambient temperature interpolation formula. Thereafter, the process of this subroutine is completed, the process returns to the main routine, and the process proceeds to S4.

  In S4, a subroutine for estimating the liquid temperature initial value U (0) when the engine 10 shown in FIG. 6 is started is executed. First, Uoff stored in the storage device is read. Then, the initial value Ub (0) of the liquid temperature Ub while the engine 10 is stopped is set as Ub (0) = Uoff (S41).

  Subsequently, the time immediately after the engine 10 is stopped is the first time point, the time point when the engine 10 is stopped is the second time point, Tb (1) is the ambient temperature interpolated at the first time point, and Ub (0) is the second time point. Used as the liquid temperature estimated at the time. Then, the liquid temperature Ub (1) at the first time point is estimated based on Tb (1), Ub (0) and the battery liquid temperature estimation formula described above. Next, using Tb (2) as the ambient temperature interpolated at the first time point and the estimated Ub (1) as the liquid temperature estimated at the second time point, the liquid temperature Ub ( 2) is estimated. This process is repeated until m = me, and the liquid temperature while the engine is stopped is sequentially calculated (S42).

  Further, the liquid temperature initial value U (0) at the time when the engine 10 is started is set as U (0) = Ub (me) (S43). The liquid temperature initial value U (0) is used for estimating the liquid temperature after the engine 10 is started (during operation of the engine 10). Thereafter, the processing of this subroutine is completed, the process returns to the main routine, and the process proceeds to S5.

  In S5, a subroutine for estimating the liquid temperature U (n) (n ≧ 1) during operation of the engine 10 shown in FIG. 7 is executed. First, immediately after the engine 10 is started (n = 1), the ambient temperature T (1) is measured by the temperature sensor 17 (S51).

  Subsequently, the time immediately after the engine 10 is started is the first time point (n = 1), the time point when the engine 10 is started is the second time point (n = 0), and T (1) is detected at the first time point. The ambient temperature, U (0) set as described above, is used as the liquid temperature estimated at the second time point. Then, U (1) at the first time point is estimated based on T (1), U (0), and the battery liquid temperature estimation formula described above (S52). S51 and S52 are repeatedly executed at a predetermined sampling interval, and the liquid temperature U (n) during the operation of the engine 10 is estimated.

  Thereafter, the processing of this subroutine is finished, and the process returns to S5 of the main routine. Then, in S5, the engine 10 is stopped and the main routine process is ended.

  Note that the processing of S42 and S52 corresponds to the battery liquid temperature estimation step, the processing of S1 corresponds to the storage step, and S3 corresponds to the battery ambient temperature interpolation step.

  When the battery liquid temperature estimation device is used, the liquid temperature initial value at the time when the engine 10 is started can be accurately estimated. As a result, when the estimated liquid temperature initial value is used as the liquid temperature estimated at the second time point at the first time point immediately after the engine 10 is started, the liquid temperature during operation of the engine 10 is estimated with high accuracy. can do. Therefore, even when the ambient temperature of the battery 11 is not measured while the engine 10 is stopped, the liquid temperature of the battery 11 during the operation of the engine 10 can be estimated with high accuracy.

  Next, another example according to this embodiment will be described.

  In other embodiments, the processing up to S32 is performed in the same manner as in the above embodiment. Subsequently, the time tp from when the engine 10 is stopped to when the engine 10 is started is compared with a predetermined time. If tp is longer than the predetermined time, U (0) = Ton is set in S43. That is, the ambient temperature detected by the temperature sensor 17 at the time when the engine 10 is started is regarded as the liquid temperature initial value at the time when the engine 10 is started.

  In another embodiment, if the first time point (n = 1) is immediately after the engine 10 is started and the second time point (n = 0) is the time point when the engine 10 is started, the temperature sensor 17 at the second time point The detected ambient temperature is used as the liquid temperature estimated at the second time point.

  Then, U (1) at the first time point is estimated based on T (1) detected at the first time point, U (0) estimated at the second time point, and the battery fluid temperature estimation formula described above. . Thereafter, U (n) is estimated sequentially.

  As the time from when the engine 10 is stopped to when it is started becomes longer, both the liquid temperature and the ambient temperature converge to the outside air temperature. When the time from when the engine 10 is stopped to when the engine 10 is started is longer than a predetermined time (for example, 12 hours), the liquid temperature and the ambient temperature can be considered equal. Therefore, in such a case, when the engine 10 is started, the ambient temperature detected by the temperature sensor 17 becomes substantially equal to the actual liquid temperature. Therefore, according to another embodiment, when the stop time of the engine 10 is long, a more accurate liquid temperature initial value can be used. As a result, the liquid temperature during operation of the engine 10 can be estimated with higher accuracy.

  The battery liquid temperature estimation device is not limited to the above-described embodiment.

  For example, the battery liquid temperature estimation device may be realized by the engine ECU 15 or may be realized by another ECU.

Other formulas such as Tb = α (βt−1) ² + γ can also be used as the battery ambient temperature interpolation formula.

  Further, the vehicle on which the battery liquid temperature estimation device is mounted may be a vehicle that does not execute the idle stop control.

  Further, a push-type start switch may be provided instead of the ignition key. Alternatively, instead of the ignition key, the driver may carry a driver transceiver that transmits and receives weak radio waves, and the vehicle may include a vehicle transceiver that can communicate with the driver transceiver.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Battery, 12 ... Starter, 13 ... Alternator, 14 ... Auxiliary machine, 15 ... Engine ECU, 17 ... Temperature sensor, 18 ... Idle stop ECU

Claims (5)

A battery fluid temperature estimation device (10) that is applied to a vehicle including an internal combustion engine (10), a battery (11), and a temperature sensor (17) that detects the ambient temperature of the battery, and that estimates the fluid temperature of the battery. 18)
Based on the ambient temperature detected or interpolated at the first time point by the temperature sensor, the liquid temperature estimated at the second time point before the first time point, and the battery liquid temperature estimation formula, Battery liquid temperature estimating means for sequentially estimating the liquid temperature at the first time point;
Storage means for storing the ambient temperature detected by the temperature sensor and the liquid temperature estimated by the battery liquid temperature estimation means when the engine is stopped;
Based on the ambient temperature detected by the temperature sensor, the ambient temperature stored by the storage means, and the battery ambient temperature interpolation formula when the engine is started after the engine is stopped Battery ambient temperature interpolation means for interpolating the ambient temperature when the engine is stopped,
The battery fluid temperature estimation means is configured to execute the engine based on the ambient temperature interpolated by the battery ambient temperature interpolation means, the fluid temperature stored by the storage means, and the battery fluid temperature estimation formula. A battery liquid temperature estimation device for estimating an initial value of the battery liquid temperature at the time of starting. The battery ambient temperature interpolation formula is
Tb: the ambient temperature interpolated by the battery ambient temperature interpolation means, t: elapsed time from when the engine was stopped, β: a predetermined coefficient, α: coefficient, γ: coefficient,
Tb = αexp (−βt) + γ
Represented by the formula
The coefficient α and the coefficient γ are stored by the storage unit and an expression in which the ambient temperature detected by the temperature sensor when the engine is started is substituted for the ambient temperature Tb of the expression. The battery liquid temperature estimation device according to claim 1, wherein the battery liquid temperature estimation device is calculated based on an equation in which the ambient temperature is substituted into the ambient temperature Tb of the mathematical formula.   The said battery liquid temperature estimation means uses the said liquid temperature initial value as the said liquid temperature estimated at the said 2nd time in the said 1st time immediately after starting the said engine. Battery liquid temperature estimation device.   The battery fluid temperature estimation means is configured to perform the first time point immediately after the engine is started on the condition that the time from when the engine is stopped until the engine is started is longer than a predetermined time. The battery liquid temperature estimation device according to claim 1 or 2, wherein the ambient temperature detected by the temperature sensor when the engine is started is used as the liquid temperature estimated at the second time point. A battery fluid temperature estimation method applied to a vehicle comprising an internal combustion engine, a battery, and a temperature sensor that detects the ambient temperature of the battery, wherein the fluid temperature of the battery is estimated,
Based on the ambient temperature detected or interpolated at the first time point by the temperature sensor, the liquid temperature estimated at the second time point before the first time point, and the battery liquid temperature estimation formula, A battery fluid temperature estimation step for sequentially estimating the fluid temperature at the first time point;
A storage step of storing the ambient temperature detected by the temperature sensor and the liquid temperature estimated in the battery liquid temperature estimation step when the engine is stopped;
Based on the ambient temperature detected by the temperature sensor, the ambient temperature stored in the storing step, and the battery ambient temperature interpolation formula when the engine is started after the engine is stopped. A battery ambient temperature interpolation step for interpolating the ambient temperature while the engine is stopped,
In the battery fluid temperature estimation step, the engine is based on the ambient temperature interpolated in the battery ambient temperature interpolation step, the fluid temperature stored in the storage step, and the battery fluid temperature estimation formula. A battery liquid temperature estimation method, wherein an initial value of the battery liquid temperature at the time of starting is estimated.

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