JP2018170263A - Secondary battery internal temperature estimation device and secondary battery internal temperature estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate an internal temperature even when a secondary battery is in use or when thermal characteristics change. In a secondary battery internal temperature estimation device for estimating the internal temperature of a secondary battery, a detection unit (current sensor 12) for detecting the external temperature of the secondary battery and an external temperature detected by the detection unit are provided. Estimating means (control unit 10) for applying the thermal equivalent circuit of the secondary battery to estimate the internal temperature, detecting means (control unit 10) for detecting the presence or absence of change in the thermal characteristics of the secondary battery, and detecting When a change in the thermal characteristics of the secondary battery is detected by the means, there is an adjusting means (control unit 10) for adjusting the parameters of the thermal equivalent circuit of the estimating means. [Selection diagram] Figure 1

Description

  The present invention relates to a secondary battery internal temperature estimation device and a secondary battery internal temperature estimation method.

  In Patent Document 1, based on a relational expression showing the relationship between the external temperature and the internal temperature of the secondary battery, the estimation means for estimating the internal temperature of the secondary battery and the element value of the equivalent circuit of the secondary battery are calculated. A calculating unit; a calculating unit that calculates a coefficient of the relational expression based on the element value of the equivalent circuit calculated by the calculating unit; and an applying unit that applies the coefficient obtained by the calculating unit to the relational expression; And a technique for estimating the internal temperature of the secondary battery based on the relational expression to which the coefficient is applied by the applying means.

Japanese Patent Laying-Open No. 2015-185284

  By the way, in the technique disclosed in Patent Document 1, an electrical equivalent circuit of a secondary battery (hereinafter referred to as “electrical equivalent circuit”) is used. The electrical equivalent circuit can calculate an accurate element value in a state where the secondary battery is not charged / discharged and no polarization or stratification occurs. The element value cannot be obtained. For this reason, when charging / discharging a secondary battery, there exists a problem that estimation of an accurate internal temperature is difficult.

  On the other hand, a method for estimating the internal temperature of the secondary battery using a thermal equivalent circuit of the secondary battery (hereinafter referred to as “thermal equivalent circuit”) has also been proposed. When such a thermal equivalent circuit is used, the internal temperature can be estimated regardless of the charge / discharge state of the secondary battery.

  However, when a thermal equivalent circuit is used, for example, when an insulator as a heat insulating material is attached, there is a problem that the internal temperature cannot be accurately estimated because the thermal characteristics change.

  The present invention has been made in view of the situation as described above, and estimates the internal temperature of the secondary battery that can accurately estimate the internal temperature even when the secondary battery is in use or when the thermal characteristics change. An object of the present invention is to provide a device and a method for estimating the internal temperature of a secondary battery.

In order to solve the above-described problems, the present invention provides a secondary battery internal temperature estimation device that estimates an internal temperature of a secondary battery, a detection unit that detects an external temperature of the secondary battery, and a detection unit that detects the external temperature of the secondary battery. The external temperature is applied to the thermal equivalent circuit of the secondary battery to estimate the internal temperature, the detection means for detecting the presence or absence of a change in the thermal characteristics of the secondary battery, and the detection Adjusting means for adjusting a parameter of the thermal equivalent circuit of the estimating means when a change in the thermal characteristics of the secondary battery is detected by the means.
According to such a configuration, it is possible to estimate an accurate internal temperature even when the secondary battery is in use or when the thermal characteristics change.

In the present invention, the detection means detects whether or not an insulator as a heat insulating material is attached to the secondary battery as a change in the thermal characteristics, and the adjustment means The thermal equivalent circuit is adjusted based on the thermal characteristics of the insulator.
According to such a configuration, an accurate internal temperature can be estimated even when an insulator is newly attached or removed.

Further, according to the present invention, the adjustment means stores the parameters of the thermal equivalent circuit when the insulator is not attached and when the insulator is attached, and the detection result of the detection means The parameter is selected according to the setting and set in the estimation means.
According to such a configuration, it is possible to reliably cope with the presence or absence of an insulator by selecting a parameter.

Further, the present invention is characterized in that the adjusting means adjusts the parameter of the thermal equivalent circuit based on a fitting process when a change in the thermal characteristic of the secondary battery is detected. To do.
According to such a configuration, an accurate internal temperature can be estimated even when an insulator with unclear thermal characteristics is attached.

According to the present invention, the detecting means is estimated based on the internal temperature of the secondary battery estimated based on an element value constituting an electrical equivalent circuit of the secondary battery and the thermal equivalent circuit. When the difference value with respect to the internal temperature of the secondary battery is equal to or greater than a predetermined threshold value, it is determined that the thermal characteristics of the secondary battery have changed.
According to such a configuration, it is possible to reliably detect a change in thermal characteristics.

Further, the present invention provides a secondary battery internal temperature estimation method for estimating an internal temperature of a secondary battery, a detection step of detecting an external temperature of the secondary battery, and the external temperature detected in the detection step, An estimation step for estimating the internal temperature by applying to a thermal equivalent circuit of the secondary battery; a detection step for detecting presence or absence of a change in thermal characteristics of the secondary battery; and the secondary battery in the detection step An adjustment step of adjusting a parameter of the thermal equivalent circuit in the estimation step when a change in the thermal characteristic is detected.
According to such a method, an accurate internal temperature can be estimated even when the secondary battery is in use or when the thermal characteristics change.

  According to the present invention, there are provided a secondary battery internal temperature estimation device and a secondary battery internal temperature estimation method capable of estimating an accurate internal temperature even when the secondary battery is in use or thermal characteristics change. It becomes possible.

It is a figure which shows the structural example of the secondary battery internal temperature estimation apparatus which concerns on embodiment of this invention. It is a block diagram which shows the detailed structural example of the control part of FIG. It is a figure which shows an example of the thermal equivalent circuit of the secondary battery shown in FIG. It is a figure which shows an example of the electrical equivalent circuit of the secondary battery shown in FIG. It is a figure which shows the change by the internal temperature of Corr_Rct1 for every SOC. It is a figure which shows the change by the internal temperature of Corr_C1 for every SOC. It is a figure which shows the time change of the internal temperature by the presence or absence of the insulator at the time of engine starting. It is a figure which shows the time change of internal temperature by the presence or absence of an insulator at the time of an engine stop. It is an example of the flowchart explaining the flow of the process performed in embodiment shown in FIG. It is an example of the flowchart explaining the flow of the process performed in embodiment shown in FIG. It is a figure which shows an example of a fitting process.

  Next, an embodiment of the present invention will be described.

(A) Description of Configuration of Embodiment of the Present Invention FIG. 1 is a diagram showing a power supply system of a vehicle having a secondary battery internal temperature estimation device according to an embodiment of the present invention. In this figure, the secondary battery internal temperature estimation device 1 includes a control unit 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, and a discharge circuit 15 as main components, and the charge state of the secondary battery 14. To control. Here, the control unit 10 refers to the outputs from the voltage sensor 11, the current sensor 12, and the temperature sensor 13, detects the state of the secondary battery 14, and controls the power generation voltage of the alternator 16 to control the power generation voltage. The charging state of the secondary battery 14 is controlled. The voltage sensor 11 detects the terminal voltage of the secondary battery 14 and notifies the control unit 10 of it. The current sensor 12 detects the current flowing through the secondary battery 14 and notifies the control unit 10 of the current. The temperature sensor 13 detects the secondary battery 14 itself or the surrounding environmental temperature, and notifies the control unit 10 of it. The discharge circuit 15 is configured by, for example, a semiconductor switch and a resistance element connected in series, and the secondary battery 14 is intermittently discharged when the control unit 10 performs on / off control of the semiconductor switch. The control of the alternator may be executed by another device (for example, an ECU (Electric Control Unit) not shown).

  The secondary battery 14 is composed of, for example, a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, or a lithium ion battery, and is charged by the alternator 16 to drive the starter motor 18 to start the engine and load 19 To supply power. The alternator 16 is driven by the engine 17 to generate AC power, convert it into DC power by a rectifier circuit, and charge the secondary battery 14. The alternator 16 is controlled by the control unit 10 and can adjust the generated voltage.

  The engine 17 is constituted by, for example, a reciprocating engine such as a gasoline engine and a diesel engine, a rotary engine, or the like, and is started by a starter motor 18 to drive driving wheels through a transmission to provide propulsive force to the vehicle. To generate electric power. The starter motor 18 is constituted by, for example, a DC motor, generates a rotational force by the electric power supplied from the secondary battery 14, and starts the engine 17. The load 19 is constituted by, for example, an electric steering motor, a defogger, a seat heater, an ignition coil, a car audio, a car navigation, and the like, and operates with electric power from the secondary battery 14.

  FIG. 2 is a diagram illustrating a detailed configuration example of the control unit 10 illustrated in FIG. 1. As shown in this figure, the control unit 10 includes a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a communication unit 10d, and an I / F (Interface) 10e. ing. Here, the CPU 10a controls each unit based on the program 10ba stored in the ROM 10b. The ROM 10b is configured by a semiconductor memory or the like, and stores a program 10ba or the like. The RAM 10c is configured by a semiconductor memory or the like, and stores data generated when the program 10ba is executed, and parameters 10ca such as mathematical formulas or tables described later. The communication unit 10d communicates with an upper device such as an ECU (Electronic Control Unit) and notifies the detected information or control information to the upper device. The I / F 10e converts the signals supplied from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 into digital signals and takes them in, and supplies drive current to the discharge circuit 15, the alternator 16, the starter motor 18, and the like. Supply them to control them.

(B) Description of Operation of the Embodiment of the Present Invention Next, the operation of the embodiment of the present invention will be described. In the following, after describing the operation principle of the embodiment of the present invention, the detailed operation will be described.

  As a method for estimating the internal temperature (electrolyte temperature) of the secondary battery 14, the following two methods are used in the present embodiment.

  The first is a method using a thermal equivalent circuit. FIG. 3 is a diagram illustrating an example of a thermal equivalent circuit of the secondary battery 14. In the thermal equivalent circuit, the temperature difference corresponds to the voltage, and the heat flow corresponds to the current. As shown in FIG. 3, the external temperature of the secondary battery 14 is Te, and the internal temperature (electrolyte temperature) is Ti. The thermal equivalent circuit of the secondary battery 14 is represented by a thermal resistance R and a thermal capacity C. At this time, when there is a temperature difference ΔT (= Te−Ti) between the external temperature and the internal temperature, heat is conducted from the higher temperature to the lower temperature. For example, when the engine 17 is stopped for a long time and the internal temperature and the external temperature are equal, when the engine 17 is started, the external temperature Te is increased by the heat generated by the engine 17 and Te> Ti is satisfied. . In this case, heat corresponding to the temperature difference ΔT (= Te−Ti) moves through the thermal resistance R and is accumulated in the heat capacity C. As a result, the internal temperature Ti rises. The heat transfer continues until the external temperature Te and the internal temperature Ti become equal, but the heat transfer speed is determined by the thermal resistance R and the heat capacity C. However, since the thermal resistance R and the heat capacity C are generally fixed values, if these values are known, the internal temperature Ti can be uniquely estimated from the external temperature Te.

  Next, the second is a method using an electrical equivalent circuit of the secondary battery 14. FIG. 4A is a diagram illustrating an example of an electrical equivalent circuit of the secondary battery 14. In the example of FIG. 4A, the electrical equivalent circuit includes Rohm, which is a resistance component corresponding to the conductor element and electrolyte resistance in the secondary battery 14, and a resistance component corresponding to the reaction resistance of the active material reaction of the electrode. Rct1 and C1 which is a capacitance component corresponding to the electric double layer at the interface between the electrode and the electrolyte.

  The element values of the elements constituting the electrical equivalent circuit vary according to the internal temperature of the secondary battery 14 and the SOC (State of Charge). For this reason, in order to reduce the influence of the SOC and the internal temperature, the reference state of the secondary battery 14 (for example, the internal temperature is 25 ° C., the SOC is 100%, etc.) is determined, and the calculated element value at that time is Using the correction coefficients shown in the following formulas (1) to (3), correction is made to the element values in the reference state. Cr_Rohm is a correction coefficient related to Rohm, Cr_Rct1 is a correction coefficient related to Rct1, and Cr_C1 is a correction coefficient related to C1. Further, f1 (Ti, SOC) to f3 (Ti, SOC) are functions having Ti and SOC as variables.

Cr_Rohm = f1 (Ti, SOC) (1)
Cr_Rct1 = f2 (Ti, SOC) (2)
Cr_C1 = f3 (Ti, SOC) (3)

  In addition, as a method of calculating | requiring f1 (Ti, SOC) -f3 (Ti, SOC), it can derive | lead-out from the measured value shown, for example in FIG. 5 and FIG. Here, FIG. 5 is a diagram showing a change in Cr_Rct1 depending on the internal temperature for each SOC. Moreover, FIG. 6 is a figure which shows the change by the internal temperature of Cr_C1 for every SOC. As shown in these figures, Cr_Rct1 and Cr_C1 vary depending on the internal temperature and the SOC.

  Here, the inverse functions of Expressions (1) to (3) are expressed by Expressions (4) to (6), and the internal temperatures obtained by these inverse functions are Ti_est_Rohm, Ti_est_Rct1, and Ti_est_C1.

Ti_est_Rohm = f1 ⁻¹ (Cr_Rohm, SOC) (4)
Ti_est_Rct1 = f2 ⁻¹ (Cr_Rct1, SOC) (5)
Ti_est_C1 = f3 ⁻¹ (Cr_C1, SOC) (6)

  While substituting the calculated SOC at that time for the right side of these formulas (4) to (6), Cr_Rohm, Cr_Rct1, and Cr_C1 obtained by the following formulas (7) to (9) are used as the right side. substitute. Note that the Rohm value in the reference state, the Rct1 value in the reference state, and the C1 value in the reference state are measured at each past time point, and an average value of these element values corrected to the reference state is used. Can do.

Cr_Rohm = Rohm value in the reference state / Rohm value at that time (7)
Cr_Rct1 = value of Rct1 in the reference state / value of Rct1 at that time (8)
Cr_C1 = value of C1 in the reference state / value of C1 at that time (9)

  Then, the internal temperature Ti can be estimated by substituting Ti_est_Rohm, Ti_est_Rct1, and Ti_est_C1 obtained by the equations (4) to (6) into the following equation (10).

  Ti = α × Ti_est_Rohm + β × Ti_est_Rct1 + γ × Ti_est_C1 (10)

  Α, β, and γ are predetermined coefficients, and are set such that α + β + γ = 1.

  By the way, in the method using the first thermal equivalent circuit, the internal temperature cannot be accurately estimated when the thermal characteristics of the secondary battery 14 change. For example, in order to slow down the change in the internal temperature of the secondary battery 14, the thermal characteristics change when an insulator is installed as a heat insulating material attached to cover the outer periphery of the secondary battery 14. To do. That is, in such a case, in the thermal equivalent circuit shown in FIG. 3, since the value of the thermal resistance R becomes large, the thermal characteristics change.

  FIG. 7 is a diagram showing a temporal change in the internal temperature of the secondary battery 14 when the engine 17 is started. In FIG. 7, the solid line indicates the temporal change of the internal temperature when the insulator is not attached, and the broken line indicates the temporal change of the internal temperature when the insulator is attached. The broken line shows a slower change than the solid line. For this reason, when the internal temperature is estimated using a thermal equivalent circuit in the case where the insulator is not mounted even though the insulator is mounted, errors indicated by a solid line and a broken line occur.

  FIG. 8 is a diagram showing a temporal change in the internal temperature of the secondary battery 14 when the engine 17 is stopped. In FIG. 8, the solid line shows the temporal change of the internal temperature when the insulator is not attached, and the broken line shows the temporal change of the internal temperature when the insulator is attached. The broken line shows a slower change than the solid line. For this reason, when the internal temperature is estimated using a thermal equivalent circuit in the case where the insulator is not attached even when the engine 17 is stopped, even though the insulator is attached, the error shown by the solid line and the broken line Occurs.

  Further, in the method using the second electrical equivalent circuit, it is necessary to perform measurement while the secondary battery 14 is stable. That is, in the electrical equivalent circuit, the secondary battery 14 is not charged / discharged, and an accurate element value can be obtained in a state where polarization or stratification does not occur. Therefore, an accurate element value cannot be obtained. For this reason, when using the secondary battery 14 (when charging / discharging), it is difficult to accurately estimate the internal temperature. Further, in order to obtain an electrical equivalent circuit, since the secondary battery 14 needs to be discharged by the discharge circuit 15 shown in FIG. 1, the power of the secondary battery 14 is used. Have difficulty.

  Therefore, in the present invention, normally, the internal temperature Tit of the secondary battery 14 is estimated using a thermal equivalent circuit, and the internal temperature Tie of the secondary battery 14 is estimated periodically using an electrical equivalent circuit. . And when the difference value of these two types of internal temperature Tit and Tie becomes larger than predetermined threshold value Th, it determines with the thermal characteristic of the secondary battery 14 having changed, and it is in the thermal characteristic after a change. A corresponding thermal equivalent circuit is newly adopted, and thereafter, the internal temperature Tit is estimated based on the new thermal equivalent circuit. More specifically, when the difference value between the internal temperatures Tit and Tie is larger than a predetermined threshold Th (| Tit−Tie |> Th), for example, it is determined that an insulator is attached to the secondary battery 14. The internal temperature Tit is estimated using a thermal equivalent circuit including an insulator (for example, a thermal equivalent circuit including the thermal resistance R including the thermal resistance of the insulator). Thereby, while being able to always estimate the internal temperature of the secondary battery 14, even when the thermal characteristic of the secondary battery 14 changes, it can respond.

  Next, a detailed operation will be described with reference to FIGS. FIG. 9 is a flowchart for explaining the flow of processing executed in the embodiment shown in FIG. The flowchart shown in FIG. 9 is executed, for example, when the engine 17 is stopped and a predetermined time (for example, several hours) elapses and the state of the secondary battery 14 is stabilized. When the flowchart shown in FIG. 9 is started, the following steps are executed.

  In step S <b> 10, the control unit 10 controls the discharge circuit 15 and starts pulse discharge of the secondary battery 14.

  In step S <b> 11, the control unit 10 refers to the output of the voltage sensor 11 and detects the terminal voltage of the secondary battery 14.

  In step S <b> 12, the control unit 10 refers to the output of the current sensor 12 and detects the current flowing through the secondary battery 14.

  In step S13, the control unit 10 determines whether or not to end the discharge. If it is determined that the discharge is to be ended (step S13: Y), the control unit 10 proceeds to step S14, and otherwise (step S13: N). Returning to step S11, the same processing is repeated.

  In step S14, the control unit 10 executes a process of learning element values of elements constituting the electrical equivalent circuit shown in FIG. 4A based on the measurement results in steps S11 and S12.

  In step S15, the control unit 10 acquires the element value of the electrical equivalent circuit calculated in step S14 as the element value at that time. As a result, the values of Rohm, Rct1, and C1 at that time are obtained.

  In step S16, the control unit 10 acquires, from the RAM 10c, the element value measured at each past time point and corrected to a value in a reference state (for example, a state where the SOC is 100% and the temperature is 25 ° C.). More specifically, the values of Rohm, Rct1, and C1 measured at each past time point are respectively multiplied by the values of Cr_Rohm, Cr_Rct1, and Cr_C1 obtained by the above formulas (1) to (3). A plurality of element values obtained in this way are acquired.

  In step S17, the control unit 10 calculates an average value of the element values acquired in step S16. More specifically, an average value of element values measured at each past time point and corrected to a value in the reference state is calculated. Instead of calculating the average value each time, the average value calculated in advance may be stored in the RAM 10c.

  In step S18, the control unit 10 calculates a ratio between the element value acquired in step S15 and the element value calculated in step S17. More specifically, the values of Cr_Rohm, Cr_Rct1, and Cr_C1 are calculated using the equations (7) to (9) described above.

  In step S19, the control unit 10 calculates the SOC. For example, the controller 10 detects an open circuit voltage OCV (Open Circuit Voltage) when the secondary battery 14 is in a stable state, and calculates the SOC based on a relational expression indicating the relationship between the OCV and the SOC. Of course, the SOC may be obtained by other methods.

  In step S20, the control unit 10 substitutes the ratio of the element values obtained in step S18 and the SOC obtained in step S19 for the inverse function to obtain Ti_est_Rohm, Ti_est_Rct1, and Ti_est_C1. More specifically, the control unit 10 substitutes the ratio of the element values obtained in step S18 as Cr_Rohm, Cr_Rct1, Cr_C1 for the above-described formulas (4) to (6), and obtained in step S19. By substituting the SOC, Ti_est_Rohm, Ti_est_Rct1, and Ti_est_C1 are obtained.

  In step S21, the control unit 10 substitutes Ti_est_Rohm, Ti_est_Rct1, Ti_est_C1 calculated by the calculation in step S20 into the equation (10), and estimates the internal temperature Tie based on the electrical equivalent circuit.

  Next, a process for estimating the internal temperature Tit using a thermal equivalent circuit will be described with reference to FIG. Note that the processing in FIG. 10 is executed periodically (for example, every few minutes) when the engine 17 is operating, for example.

  In step S <b> 50, the control unit 10 refers to the output of the temperature sensor 13 and detects the external temperature Te of the secondary battery 14.

  In step S51, the control unit 10 estimates the internal temperature Tit based on the thermal equivalent circuit. More specifically, the internal temperature Tit is estimated by the following process.

  That is, assume that the external temperature is Te, the time interval of one step in the case of discrete time operation is Δt, the estimated value of the internal temperature at the present time is Tit (n × Δt), and the estimated value of the internal temperature one step before is Let Tit ((n−1) × Δt). Further, the internal temperature Tit is estimated based on the following equation (11), where the proportional gain is Kp, the integral gain is Ki, the integral time is τi, and the integral operation amount is Intg (n × Δt).

  Tit (n × Δt) = Kp × (Te (n × Δt) −Tit ((n−1) × Δt)) + Intg (n × Δt) (11)

  Intg (n × Δt) is expressed by the following formula (12), and Ki is expressed by the following formula (13).

  Intg (n × Δt) = Intg ((n−1) × Δt) + Ki × (Te (n × Δt)) − Tit ((n−1) × Δt) (12)

  Ki = Kp / τi (13)

  In step S52, the control unit 10 determines whether or not the internal temperature Tie based on the electrical equivalent circuit has been obtained most recently. If it is determined that the internal temperature Tie has been obtained (step S52: Y), the process proceeds to step S53. Otherwise (step S52: N), the process ends. For example, if the internal temperature based on the electrical equivalent circuit is obtained most recently (for example, within 1 minute) by the process shown in FIG. 9, the determination is Y and the process proceeds to step S53.

  In step S53, the control unit 10 calculates the absolute value of the difference between the internal temperature Tit estimated based on the thermal equivalent circuit in step S51 and the internal temperature Tie estimated based on the electrical equivalent circuit in step S21 of FIG. (= | Tit−Tie |) is determined, and it is determined whether or not the absolute value of the difference is larger than a predetermined threshold Th. If | Tit−Tie |> Th is satisfied (step S53: Y), step S54 is performed. In other cases (step S53: N), the process ends. For example, when an insulator is attached to the secondary battery 14 and the thermal characteristics of the secondary battery 14 change, the internal temperature Tit estimated based on the thermal equivalent circuit is an error as shown in FIGS. However, since the internal temperature Tie estimated based on the electrical equivalent circuit has no error, it is determined as Y in this case, and the process proceeds to step S54.

  In step S <b> 54, the control unit 10 determines that the insulator is attached to the secondary battery 14. The determination result may be displayed on an indicator or the like, for example, and notified to the user. Thereby, the user can know whether the control part 10 has determined the presence or absence of mounting | wearing of an insulator correctly.

  In step S55, the control unit 10 acquires a coefficient (parameter) when the insulator is mounted from the parameter 10ca of the RAM 10c. More specifically, the RAM 10c stores the proportional gain Kp and the integration time τi for each of the insulators mounted and not mounted, and selects and acquires the corresponding coefficients based on the determination result of step S54. You just have to do it.

  In step S56, the control unit 10 applies the coefficient acquired in step S55 to the above-described equations (11) to (13).

  In step S57, the control unit 10 estimates the internal temperature Tit using a thermal equivalent circuit. More specifically, the internal temperature Tit is estimated using the equations (11) to (13) to which the coefficients are applied in step S56, and is adopted as a more accurate value than the value estimated in step S51.

  As described above, according to the embodiment of the present invention, since the internal temperature of the secondary battery 14 is estimated using a thermal equivalent circuit, the secondary battery 14 is not stable. Even the internal temperature can be known.

  Further, in the embodiment of the present invention, the thermal characteristics of the secondary battery 14 change when the difference value between these is large as compared with the estimation result of the internal temperature by the electrical equivalent circuit (the insulator is attached). ), And the coefficient is changed to the coefficient at the time of installing the insulator, so that the accurate internal temperature can be known even when the thermal characteristics change.

(C) Description of Modified Embodiment It goes without saying that the above embodiment is merely an example, and the present invention is not limited to the case described above. For example, although the circuit shown in FIG. 4A is used as the electrical equivalent circuit in the above embodiment, for example, the equivalent circuit shown in FIG. 4B may be used. In the circuit shown in FIG. 4B, a reaction resistor Rct2 and an electric double layer capacitor C2 connected in parallel are newly added to the equivalent circuit shown in FIG. According to such an electrical equivalent circuit, the internal temperature of the secondary battery 14 can be estimated more accurately.

  In the above embodiment, the coefficient (proportional gain Kp and integration time τi) of the thermal equivalent circuit stored in advance is changed according to whether or not the insulator is attached. However, the coefficient may be obtained by fitting processing.

  More specifically, the internal temperature is estimated at a plurality of timings by an electric equivalent circuit to be Tie1, Tie2, Tie3,..., Tiem (m> 1). Tit1, Tit2, Tit3,..., Titm, and stored together with the estimated times (t1, t2, t3,..., Tm). Then, the error sum of squares RSS between Tie1, Tie2, Tie3,..., Tem and Tit1, Tit2, Tit3,..., Titm is obtained based on the following equation, and the obtained RSS is minimized. By learning such τi and Kp by the least square method or the like, the liquid temperature estimation error can be reduced.

RSS = Σ (Tiej−Titj) ² (14)
Where j = 1, 2, 3,..., M

  In addition, FIG. 11 is a figure which shows the result of a fitting process. In FIG. 11, the solid line indicates the actually measured internal temperature, the rhombus indicates the internal temperature estimation result based on the electrical equivalent circuit every hour, and the broken line indicates the polynomial fitting result. As shown in FIG. 11, the actually measured value and the estimation result by the electrical equivalent circuit agree very well, and the fitting result using the polynomial agrees well with the actually measured result. From FIG. 11, it can be seen that the internal temperature can be estimated with high accuracy when fitting is used.

  Further, in the above embodiment, the coefficient of the thermal equivalent circuit is changed when the insulator is changed from the not attached state to the attached state, but it is not attached from the attached state. The present invention can also be applied when the state changes.

  In the above embodiment, as an example in which the thermal characteristics of the secondary battery 14 change, the attachment and detachment of the insulator has been described as an example. However, in addition to this, for example, the thermal characteristics change, for example, When the electrolyte solution is replaced or reduced (when the heat capacity C changes), when the case that houses the secondary battery 14 is replaced (when the thermal resistance R changes), or when the secondary battery 14 itself is When they are exchanged (when both the heat capacity C and the thermal resistance R change), the above-described processing may be executed.

  The flowcharts shown in FIGS. 9 and 10 are examples, and processes other than those in FIGS. 9 and 10 may be executed.

DESCRIPTION OF SYMBOLS 1 Secondary battery internal temperature estimation apparatus 10 Control part (estimation means, detection means, adjustment means)
10a CPU
10b ROM
10c RAM
10d Communication unit 10e I / F
11 Voltage sensor 12 Current sensor 13 Temperature sensor (detection means)
14 Secondary battery 15 Discharge circuit 16 Alternator 17 Engine 18 Starter motor 19 Load

Claims (6)

In the secondary battery internal temperature estimation device for estimating the internal temperature of the secondary battery,
Detecting means for detecting an external temperature of the secondary battery;
Estimating means for estimating the internal temperature by applying the external temperature detected by the detecting means to a thermal equivalent circuit of the secondary battery;
Detecting means for detecting the presence or absence of a change in thermal characteristics of the secondary battery;
An adjustment unit that adjusts a parameter of the thermal equivalent circuit of the estimation unit when a change in the thermal characteristic of the secondary battery is detected by the detection unit;
A secondary battery internal temperature estimation device characterized by comprising: The detection means detects the presence or absence of an insulator as a heat insulating material on the secondary battery as a change in the thermal characteristics,
The adjusting means adjusts the thermal equivalent circuit based on the thermal characteristics of the insulator when the insulator is attached and detached.
The secondary battery internal temperature estimation device according to claim 1.   The adjustment means stores the parameter of the thermal equivalent circuit when the insulator is not attached and when the insulator is attached, and the parameter is set according to the detection result of the detection means. The secondary battery internal temperature estimation device according to claim 2, which is selected and set in the estimation means.   The adjustment unit adjusts the parameter of the thermal equivalent circuit based on a fitting process when a change in the thermal characteristic of the secondary battery is detected. Secondary battery internal temperature estimation device.   The detection means includes the internal temperature of the secondary battery estimated based on element values constituting an electrical equivalent circuit of the secondary battery, and the secondary battery estimated based on the thermal equivalent circuit. 5. The device according to claim 1, wherein when the difference value from the internal temperature is equal to or greater than a predetermined threshold value, it is determined that the thermal characteristic of the secondary battery has changed. 6. Secondary battery internal temperature estimation device. In the secondary battery internal temperature estimation method for estimating the internal temperature of the secondary battery,
A detection step of detecting an external temperature of the secondary battery;
An estimation step of estimating the internal temperature by applying the external temperature detected in the detection step to a thermal equivalent circuit of the secondary battery;
A detection step of detecting the presence or absence of a change in the thermal characteristics of the secondary battery;
When the change in the thermal characteristics of the secondary battery is detected in the detection step, an adjustment step for adjusting the parameters of the thermal equivalent circuit in the estimation step;
A method for estimating the temperature inside the secondary battery.

Images