State estimation system, state estimation device, and state estimation method

Abstract

To suppress the influence of voltage changes due to loads and detect electrical discharges by an appropriate current value when detecting an internal resistance of a rechargeable battery.SOLUTION: A state estimation system comprises: an acquisition unit for acquiring a voltage value of a battery and a current value of a current flowing from the battery; a discharge circuit for discharging the battery; an identification unit for identifying a no-change period in which a discharge current flowing to a load that is supplied with electric power from the battery does not change, on the basis of at least a voltage value acquired by the acquisition unit and a time when the voltage value is acquired; a discharge control unit for controlling the discharge circuit to discharge the battery so that a current of a prescribed current value flows from the battery in the no-change period identified by the identification unit; and an internal resistance estimation unit for estimating the internal resistance value of the battery on the basis of the voltage and current values acquired by the acquisition unit when a discharge from the battery is being carried out with the prescribed current value by the discharge control unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a state estimation system, a state estimation device, and a state estimation method.

Background Art

[0002] As inventions related to technologies for estimating the state of a rechargeable battery, there are, for example, the inventions disclosed in Patent Documents 1 and 2. The system disclosed in Patent Document 1 is a system that determines the degree of battery deterioration or discharge capacity using the impedance of the battery estimated from the current value and the response voltage when the battery is discharged in a predetermined discharge pattern, and forms a discharge pattern such that the response voltage at each discharge when the discharge is performed two or more times becomes substantially constant. The method disclosed in Patent Document 2 determines whether the battery is in a state of receiving either a charging polarization or a discharging polarization, and when it is determined that the battery is receiving a charging polarization, applies a discharge current pulse with a variable period to the battery, while when it is determined that the battery is receiving a discharging polarization, applies a charging current pulse with a variable period to the battery. Then, the input current and the response voltage of the battery after a predetermined number of cycles have elapsed from the application start timing of the charging current pulse or the discharging current pulse are measured, and the internal impedance of the battery is calculated using the measured input current and response voltage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vehicle equipped with a battery, various electrical components are installed, and these electrical components operate at their respective timings, causing currents associated with their operations to flow. When a discharge due to a load is performed at a timing for performing a predetermined discharge for estimating the state of the battery mounted on the vehicle, variations due to the discharge of the load are superimposed on the measured voltage and current, resulting in a decrease in the accuracy of the calculated internal resistance (impedance). In order to accurately calculate the internal resistance, even in a vehicle with large voltage and current variations due to the load, the current value of a predetermined discharge current may be set so as to obtain a sufficient voltage drop amount. However, this discharge consumes the power of the battery, and an excessive discharge current causes excessive power consumption, accelerating battery wear and battery deterioration. The inventions disclosed in Patent Documents 1 and 2 are only directed to estimating the internal impedance of the battery from the response when the battery is discharged, and do not solve such problems.

[0005] The present invention has been made in view of the above, and an object thereof is to provide a technique for suppressing the influence of voltage variations due to a load and detecting by discharging with an appropriate current value when detecting the internal resistance of a rechargeable battery.

Means for Solving the Problems

[0006] In order to solve the above-described problems and achieve the object, a state estimation system according to one aspect of the present invention is a state estimation system for estimating the state of a rechargeable battery, including an acquisition unit that acquires a voltage value of the battery and a current value of a current flowing from the battery, a discharge circuit that discharges the battery, and a specifying unit that specifies a non-varying period during which a discharge current flowing to a load supplied with power from the battery does not vary based on at least the voltage value acquired by the acquisition unit and the time at which the voltage value is acquired, a discharge control unit that controls the discharge circuit to discharge the battery such that a current having a predetermined current value flows from the battery during the non-varying period specified by the specifying unit, and an internal resistance estimation unit that estimates an internal resistance value of the battery based on the voltage value and the current value acquired by the acquisition unit when the discharge from the battery by the discharge control unit is performed at the predetermined current value.

[0007] In the state estimation system according to one aspect of the present invention, when the non-varying period is specified, the acquisition unit may shorten a period for acquiring a voltage value and a current value during the non-varying period.

[0008] Further, in the state estimation system according to one aspect of the present invention, when the non-varying period is specified, the acquisition unit may shorten a period for acquiring a voltage value and a current value before and after the start and end of the non-varying period.

[0009] Further, in the state estimation system according to one aspect of the present invention, when the non-varying period is specified, the acquisition unit may lengthen a period for acquiring a voltage value and a current value during the non-varying period.

[0010] Further, the state estimation device according to the present invention is a state estimation device that estimates the state of a rechargeable battery, and includes an acquisition unit that acquires a voltage value of the battery and a current value of a current flowing from the battery, a discharge circuit that discharges the battery, a specifying unit that specifies a non-varying period during which a discharge current flowing to a load powered by the battery does not vary based on at least the voltage value acquired by the acquisition unit and the time when the voltage value was acquired, a discharge control unit that controls the discharge circuit to discharge the battery so that a current having a predetermined current value flows from the battery during the non-varying period specified by the specifying unit, and an internal resistance estimation unit that estimates an internal resistance value of the battery based on the voltage value and the current value acquired by the acquisition unit when the discharge from the battery is being performed at the predetermined current value by the discharge control unit.

[0011] Further, the state estimation method according to the present invention is a state estimation method for estimating the state of a rechargeable battery, and includes an acquisition step of acquiring a voltage value of the battery and a current value of a current flowing from the battery, a specifying step of specifying a non-varying period during which a discharge current flowing to a load powered by the battery does not vary based on at least the voltage value acquired in the acquisition step and the time when the voltage value was acquired, a discharge control step of controlling a discharge circuit that discharges the battery so that a current having a predetermined current value flows from the battery during the non-varying period specified in the specifying step, and an internal resistance estimation step of estimating an internal resistance value of the battery based on the voltage value and the current value acquired in the acquisition step when the discharge from the battery is being performed at the predetermined current value in the discharge control step.

Advantages of the Invention

[0012] According to the present invention, when detecting the internal resistance of a rechargeable battery, it is possible to suppress the influence of voltage fluctuations due to the load and perform detection by discharging with an appropriate current value.

Brief Description of the Drawings

[0013]

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DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below. Also, in the description of the drawings, the same or corresponding elements are appropriately denoted by the same reference numerals.

[0015] [Embodiment] (Configuration of Embodiment) FIG. 1 is a diagram showing a power supply system of a vehicle V according to an embodiment of the present invention. The battery 20 is a rechargeable battery having an electrolytic solution, and is constituted by, for example, a lead-acid battery, a lithium-ion battery, a nickel-cadmium battery, a nickel-metal hydride battery, or the like. The battery 20 is charged by the alternator 25, drives the starter motor 27, and supplies electric power to the load 28. The starter motor 27 is constituted by, for example, a DC motor, generates a rotational force by the electric power supplied from the battery 20, and starts the engine 26. The engine 26 is constituted by, for example, a reciprocating engine such as a gasoline engine and a diesel engine, or a rotary engine. The engine 26 is started by the starter motor 27, drives the drive wheels via the transmission, gives a driving force to the vehicle VA, and drives the alternator 25. The alternator 25 is driven by the engine 26 to generate AC power, and the generated AC power is converted into DC power by a rectifier circuit to charge the battery 20. The load 28 is, for example, various electrical components mounted on the vehicle V, and operates by the electric power supplied from the battery 20.

[0016] Further, the vehicle V includes an ECU (Electronic Control Unit) 3 which is a higher-level device that controls the main control of the drive system of the vehicle V, a state estimation device 1 as a state estimation system for detecting the state of the battery 20, a voltage sensor 21, a current sensor 22, a temperature sensor 23, and a discharge circuit 24.

[0017] The voltage sensor 21, the current sensor 22, and the temperature sensor 23 are sensors used to detect the state of the battery 20. The voltage sensor 21 measures the terminal voltage of the battery 20 and outputs a signal indicating the measured voltage to the state estimation device 1. The current sensor 22 measures the charging current and the discharging current of the battery 20 and outputs a signal indicating the measured current to the state estimation device 1. The temperature sensor 23 measures the temperature of the electrolyte of the battery 20 or the temperature around the battery 20 and outputs a signal indicating the measured temperature to the control unit 10.

[0018] The discharge circuit 24 is a circuit used to detect the state of the battery 20. Here, the discharge circuit 24 is a circuit different from the load 28 and is controlled independently of the load 28. The discharge circuit 24 is, for example, a circuit configured by connecting a semiconductor element and a resistor element, and discharges the battery 20 at a predetermined current value in response to the control from the state estimation device 1. Preferably, the battery 20 is discharged in a predetermined (for example, rectangular wave-like) pattern. The predetermined pattern includes, for example, a pattern in which the discharge is performed a predetermined number of times. Also, the predetermined pattern is not limited to being rectangular wave-like and may be triangular wave-like or trapezoidal wave-like.

[0019] FIG. 2 is a diagram showing the circuit configuration of the discharge circuit 24. The discharge circuit 24 has a transistor TR1 and a resistor R11. The resistor R11 is a fixed resistor, one end of which is connected to the positive electrode of the battery 20 and the other end of which is connected to the collector of the transistor TR1. The transistor TR1 is an NPN-type transistor, the base of which is connected to the control unit 10, and the emitter of which is connected to one end of the shunt resistor SR. The shunt resistor SR is an example of the current sensor 22. The shunt resistor SR has one end connected to the control unit 10 and the emitter of the transistor TR1, and the other end connected to the negative electrode of the battery 20. In the discharge circuit 24, by changing the current value of the signal supplied by the control unit 10 to the base of the transistor TR1, the current value when the battery 20 is discharged in a predetermined pattern can be changed.

[0020] The state estimation device 1 acquires signals output from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 when the battery 20 discharges in a predetermined pattern by the discharge circuit 24, and detects the state of the battery 20 based on the acquired signals. Note that the state estimation device 1, the voltage sensor 21, the current sensor 22, the temperature sensor 23, and the discharge circuit 24 may not be separate configurations, and a configuration in which some or all of these are combined may be used as the state estimation device.

[0021] FIG. 3 is a block diagram showing an example of the configuration of the state estimation device 1. The state estimation device 1 includes a control unit 10 including a CPU (Central Processing Unit) 10a, a ROM (Read Only Memory) 10b, and a RAM (Random Access Memory) 10c, a storage unit 11, a communication unit 12, an interface 13, and a bus 14. Note that the control unit 10 may be configured by a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a GPU (Graphics Processing Unit), etc. instead of the CPU 10a. Here, all the elements (control unit 10, storage unit 11, communication unit 12, interface 13) of the state estimation device 1 do not have to be integrated, and for example, each element may be distributed inside the vehicle V as a state estimation system.

[0022] The bus 14 is a group of signal lines that mutually connect the CPU 10a, the ROM 10b, the RAM 10c, the storage unit 11, the communication unit 12, and the interface 13, and enables the exchange of information between them. The communication unit 12 communicates with the ECU 3 and exchanges various information. The interface 13 converts the signals supplied from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 into digital signals and acquires them, and outputs a control signal for controlling the discharge circuit 24.

[0023] The memory unit 11 is composed of a non-volatile memory and stores, for example, the threshold values described later. The ROM 10b is composed of a non-volatile semiconductor memory or the like and stores programs 10ba and the like. The RAM 10c is composed of a semiconductor memory or the like and stores data generated when the CPU 10a executes the program 10ba, the measurement results of the voltage sensor 21, the current sensor 22, and the temperature sensor 23, and various values calculated by the CPU 10a using these measurement results.

[0024] The CPU 10a controls each unit based on the program 10ba stored in the ROM 10b. The functions of the control unit 10 are realized as functional units by the CPU 10a reading and executing the program 10ba from the ROM 10b.

[0025] FIG. 4 is a functional block diagram showing the configuration of the functions realized in the control unit 10 when the CPU 10a executes the program 10ba. In the control unit 10, an acquisition unit 101, an internal resistance estimation unit 102, a specification unit 103, a discharge control unit 104, and a state estimation unit 105 are realized.

[0026] The acquisition unit 101 acquires the voltage value of the battery 20, the current value of the current flowing from the battery 20, and the temperature of the battery 20 indicated by the signals output from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 and acquired by the interface 13.

[0027] The internal resistance estimation unit 102 estimates the internal resistance of the battery 20 based on the voltage value and the current value acquired by the acquisition unit 101. Specifically, the internal resistance estimation unit 102 estimates the internal resistance value of the battery 20 using the voltage value of the battery 20 and the current value of the current flowing from the battery 20 acquired by the acquisition unit 101 when the battery 20 discharges in a predetermined pattern by the discharge circuit 24. The internal resistance value of the battery 20 is obtained, for example, by measuring the changes in the voltage and current of the battery 20 when the control unit 10 controls the discharge circuit 24 to discharge the battery 20 in a predetermined pattern by the voltage sensor 21 and the current sensor 22 and calculating the internal resistance from the measurement results.

[0028] The internal resistance value can be estimated, for example, by "the amount of voltage change when the battery 20 is discharged in a predetermined pattern / the current value when the battery 20 is discharged in a predetermined pattern". This amount of voltage change can be calculated from the difference between the voltage sampled by the acquisition unit 101 when no discharge in a predetermined pattern is performed and the voltage sampled by the acquisition unit 101 when discharge in a predetermined pattern is performed. As the current value when the battery 20 is discharged in a predetermined pattern, a preset set value of the current value may be used. Also, the current value when the battery 20 is discharged in a predetermined pattern can be calculated from the difference between the current value sampled by the acquisition unit 101 when no discharge in a predetermined pattern is performed and the current value sampled by the acquisition unit 101 when discharge in a predetermined pattern is performed. Note that the voltage value and the current value for estimating the internal resistance value may be values in one sampling, or when multiple samplings are performed, they may be average values of the results of multiple samplings. Also, as a method of discharging the battery 20 in a predetermined pattern to estimate the internal resistance value, for example, there are methods disclosed in Japanese Patent No. 3960998, Japanese Patent No. 4494904, Japanese Patent No. 5342160, etc., but it may be calculated by other known methods.

[0029] Based on the voltage value and the current value acquired by the acquisition unit 101, the specifying unit 103 specifies a non-operation period during which the battery 20 does not discharge to the load 28 and is equal to or longer than the discharge period in a predetermined pattern. This non-operation period is an example of a non-fluctuation period during which the discharge current flowing to the load 28 supplied with power from the battery 20 does not fluctuate.

[0030] During the non-operation period of the load 28 specified by the specifying unit 103, the discharge control unit 104 outputs a control signal to the base of the transistor TR1 to control the discharge circuit 24 so that discharge is performed in a predetermined pattern by the battery 20 and a current of a predetermined current value flows from the battery 20.

[0031] Based on the voltage value and current value acquired by the acquisition unit 101, the internal resistance value estimated by the internal resistance estimation unit 102, etc., the state estimation unit 105 calculates or estimates the OCV (Open Circuit Voltage), SOC (State Of Charge), SOH (State Of Health), SOF (State of Function), etc. as the state of the battery 20. Regarding the calculation or estimation of OCV, SOC, SOH, and SOF, for example, as disclosed in Japanese Patent Application Laid-Open No. 2021-196174, it can be calculated or estimated using an equivalent circuit model of the battery 20. For example, regarding OCV, the control unit 10 sets the terminal voltage of the battery 20 measured immediately before the start of the battery 20 or the voltage value estimated from the charge / discharge state of the battery 20 as the OCV. Regarding SOC, the control unit 10 estimates it based on, for example, the internal resistance value calculated from the measured current value and voltage value, or a combination of OCV and the current integration value. Regarding SOH and SOF, the control unit 10 performs estimation based on the estimation based on OCV or using constants and relational expressions of the equivalent circuit model.

[0032] (Operation example of the embodiment) Next, the operation example of this embodiment will be described. FIG. 5 is a flowchart showing the flow of the process in which the control unit 10 estimates the internal resistance value and state of the battery 20. The control unit 10 executes the process shown in FIG. 5 at, for example, a predetermined period or a predetermined timing.

[0033] First, the control unit 10 determines whether the battery 20 is in a standby state (step S101). Here, when the engine 26 is stopped, the control unit 10 determines that it is in a standby state (YES in step S101). When the engine 26 is not stopped, the control unit 10 determines that it is not in a standby state (NO in step S101). Regarding the determination of whether the engine 26 is stopped, the control unit 10 communicates with the ECU 3 to make the determination. For example, the control unit 10 inquires the ECU 3 about the state of the engine 26 via the communication unit 12. When it obtains a response from the ECU 3 indicating engine stop during ignition off or idling stop, it determines that it is in a standby state and proceeds to step S102. When it obtains a response from the ECU 3 indicating that the engine is operating, it determines that it is not in a standby state and ends the process of FIG. 5. Note that when the vehicle V is a hybrid vehicle, the ECU 3 may set the state where neither the engine 26 nor the electric motor is operating as the standby state. When the vehicle V is an electric vehicle, the ECU 3 may set the state where the electric motor is not operating as the standby state.

[0034] When the control unit 10 determines in step S101 that it is in a standby state, it determines whether it is a non-operation period (step S102). Note that the non-operation period is specified by a process described later. The process for specifying this non-operation period will be described later. When the control unit 10 determines that it is a non-operation period (No in step S102), it ends the process of FIG. 5. When the control unit 10 (discharge control unit 104) determines that it is a non-operation period (Yes in step S102), the battery 20 discharges in a predetermined pattern, and the discharge circuit 24 is controlled so that a current of a predetermined current value flows from the battery 20. The acquisition unit 101 samples and acquires the voltage value and the current value at a predetermined period (step S103). The control of the discharge circuit 24 performed here is an example of a discharge control step. Also, step S103 is an example of an acquisition step.

[0035] FIG. 6 is a diagram showing an example of a control signal output from the control unit 10 to the discharge circuit 24 when controlling the discharge circuit 24. In the present embodiment, the control signal is a signal that outputs a rectangular wave a predetermined number of times at a predetermined period. A period TE1 shown in FIG. 6 is a period during which the transistor TR1 is turned on and the battery 20 discharges. A period TE2 shown in FIG. 6 is a period during which the acquisition unit 101 samples a voltage value and a current value at a predetermined period in order to estimate the internal resistance value. A period T1 shown in FIG. 6 is a period of the rectangular wave. A period TE3 shown in FIG. 6 is a period for controlling the discharge circuit 24.

[0036] FIG. 7 is a diagram showing an example of a voltage waveform when the battery 20 discharges by the rectangular wave of the control signal. The acquisition unit 101 samples the voltage value measured by the voltage sensor 21 and the current value measured by the current sensor 22 at a predetermined period as indicated by the arrow during a period TE2 shown in FIG. 7.

[0037] The control unit 10 (internal resistance estimation unit 102) estimates the internal resistance value of the battery 20 when the period TE3 ends (step S104). Step S104 is an example of an internal resistance estimation step. Since the control unit 10 estimates the internal resistance value based on the voltage value and the current value sampled during the non-operation period when the battery 20 is not discharging to the load 28, the influence of the voltage fluctuation by the load 28 can be suppressed, and the internal resistance value can be estimated by the discharge with an appropriate current value.

[0038] Next, the control unit 10 (state estimation unit 105) estimates the state of the battery 20 based on the internal resistance value estimated in step S104 (step S105). Here, since the control unit 10 estimates the state of the battery 20 based on the internal resistance value estimated by the discharge with an appropriate current value, the state of the battery 20 can be estimated with high accuracy.

[0039] Next, the control unit 10 notifies the ECU 3 of the estimation result of step S105 (step S106). The ECU 3 that has obtained the estimation result of the state of the battery 20 notifies, for example, the state of the battery 20 on the instrument panel. Note that the notification of the state of the battery 20 is not limited to the notification on the instrument panel, and may be, for example, an alarm sound or voice. Further, these notifications may be performed at the timing when the accessory power supply is turned on in the vehicle V or at the timing of ignition on.

[0040] Next, an operation example for specifying a period during which the battery 20 is not discharging with respect to the load 28 will be described. FIG. 8 is a diagram showing a period TE3 during which the discharge circuit 24 is controlled in the process of FIG. 5 and a period TE4 during which the discharge circuit 24 is not controlled. The control unit 10 controls the discharge circuit 24 at a predetermined period T2 until a period during which the battery 20 does not discharge with respect to the load 28 is specified. The control unit 10 (acquisition unit 101) samples the voltage value and the current value at a predetermined period during the period TE4 when the discharge circuit 24 is not controlled. The period at which the acquisition unit 101 performs sampling during the period TE4 is longer than the period at which sampling is performed during the period TE2. The voltage value and the current value sampled during the period TE4 are stored in the storage unit 11 in time series.

[0041] FIG. 9 is a flowchart showing the flow of processing when the control unit 10 specifies a non-operation period during which the battery 20 is not discharging with respect to the load 28 during the period TE4. The control unit 10 determines whether or not the load 28 has operated based on the voltage value sampled and obtained during the period TE4 (step S201). Here, the step in which the control unit 10 obtains the voltage value is an example of an acquisition step. Here, when the difference between the newly stored voltage value and the previously stored voltage value exceeds a predetermined threshold value stored in the storage unit 11, the control unit 10 determines that the load 28 has operated (Yes in step S201). When the difference between the newly stored voltage value and the previously stored voltage value does not exceed the predetermined threshold value stored in the storage unit 11, the control unit 10 determines that the load 28 is not operating (No in step S201).

[0042] Note that when the control unit 10 determines whether the load 28 has operated, it not only determines whether the difference between the newly memorized current value and the previously memorized current value of the current value exceeds the threshold value in addition to the voltage value, and if the current value also exceeds the threshold value, it may be determined that the load 28 is operating. Further, the control unit 10 may determine whether the load 28 has operated based on whether the difference between the newly memorized voltage value and the average value of the voltage values of a plurality of times in the past from the previous time exceeds the threshold value, instead of the difference between the newly memorized voltage value and the previously memorized voltage value. Further, the threshold value is not limited to a fixed threshold value in advance, and it is determined by a statistical significance test method whether there is a significant change with respect to the variation that also occurs in a state where there is no current / voltage variation due to the operation of the load 28, and if there is a significant change, it may be determined that the load 28 has operated.

[0043] FIG. 10 is a diagram showing an example of a voltage waveform measured by the voltage sensor 21 when the load 28 operates. Since the difference between the voltage sampled at the time point t1 shown in FIG. 10 and the voltage value sampled at the time point t2 does not exceed the threshold value, the control unit 10 determines that the load 28 is not operating at the time point t2. Since the difference between the voltage sampled at the time point t2 shown in FIG. 10 and the voltage value sampled at the time point t3 exceeds the threshold value, the control unit 10 determines that the load 28 has operated at the time point t3. The control unit 10 causes the storage unit 11 to store the time at the time point t3 when the load 28 starts operating (step S202).

[0044] Next, the control unit 10 acquires the sampled voltage value and determines whether the load has stopped (step S203). Since the difference between the voltage sampled at time point t2 shown in FIG. 10 and the voltage value sampled at time point t4 exceeds the threshold value, the control unit 10 determines that the load 28 has not stopped at time point t4 (No in step S203). Since the difference between the voltage sampled at time point t2 shown in FIG. 10 and the voltage value sampled at time point t5 does not exceed the threshold value, the control unit 10 determines that the load 28 has stopped at time point t5 (Yes in step S203). When the control unit 10 determines Yes in step S203, it specifies the operation period TE5 of the load 28 from the time difference between the time point when it is determined that the load 28 has operated and the time point when it is determined that the load 28 has stopped (step S204). Further, the control unit 10 stores the time of time point t5 in the storage unit 11 as the time when the load 28 has stopped operating (step S205).

[0045] The control unit 10 repeatedly executes the process of FIG. 9, and specifies the non-operation period TE6 and the period during which the load 28 stops operating for a period of TE2 or more from the plurality of times stored in the storage unit 11. For example, among a plurality of microcomputers mounted on the vehicle V, there are some that operate periodically when the engine 26 is stopped. Also, for example, when the wiper is intermittently driven during idling stop, the motor that drives the wiper operates at a predetermined period. When such a load operates, since the time interval of the stored times becomes constant, the control unit 10 specifies the period T3 during which these loads 28 stop operating from the time interval of the times when the load 28 stops operating. Further, the control unit 10 specifies the non-operation period TE6 during which the load 28 stops for a period of TE2 or more as the non-operation period from the time interval between the time when the load 28 stops operating and the time when it starts operating, which are stored in the storage unit 11. The step of specifying this non-operation period TE6 and the period T3 is an example of a specifying step.

[0046] When the control unit 10 identifies a period in which the load 28 does not operate and a non - operating period in which the load 28 does not operate for a period TE2 or longer, at the time of step S102 described above, if it is not the non - operating period TE6 (if it is the period TE5) (No in step S102), since it is a period in which the battery 20 discharges to the load 28, the process of FIG. 5 is terminated. Further, when the control unit 10 is in the non - operating period TE6 at the time of step S102 described above (not the period TE5) (No in step S102), since it is not a period in which the battery 20 discharges to the load 28, the process flow moves to step S103.

[0047] FIG. 11 is a diagram showing an example of a voltage waveform measured by the voltage sensor 21 when the load 28 operates when the battery 20 discharges in a predetermined pattern during the period TE1. For example, if, after determining Yes in step S101 at this timing, the control unit 10 executes the process of step S103 without performing the process of step S102, as shown in FIG. 11, due to the voltage change due to the discharge in a predetermined pattern and the discharge due to the operation of the load being added, the measured voltage is a voltage in which the voltage drop due to the discharge in a predetermined pattern and the voltage drop due to the operation of the load are superimposed. When sampling the voltage value and the current value in the period TE2 in such a state and estimating the internal resistance value, since the variation due to the operation of the load is superimposed on the sampled voltage value and current value, the accuracy of the estimated internal resistance value will decrease. On the other hand, in the present embodiment, during the period TE5 in which the load 28 operates, since the process of step S103 is not performed, the variation due to the operation of the load is not superimposed on the voltage value and the current value sampled for estimating the internal resistance value, and the internal resistance value can be accurately estimated by discharging with an appropriate current value.

[0048] When the engine is stopped, for example, non-periodic loads such as the lighting of the headlights and the operation of the power window may operate. If the period TE2 overlaps when such a load 28 is operating, the discharge due to the operation of the load is added to the voltage change due to the discharge of a predetermined pattern, and the internal resistance value cannot be accurately estimated. In order to prevent the internal resistance value from being unable to be accurately estimated due to the operation of such a load 28, the control unit 10, for example, inquires the ECU 3 about the operating state of the load 28, and when a response that the load 28 driven by the driver's operation is operating is obtained, it may be determined as No in step S102, and the sampling of the voltage value and the current value for estimating the internal resistance value may not be performed.

[0049] In the present embodiment, the period T3 during which the load 28 does not operate and the non-operation period TE6 during which the load 28 does not operate may be initialized when the engine 26 stops and may be in an unspecified state until they are specified.

[0050] Further, in the present embodiment, when the period during which the difference between the voltage values sampled after the time point t5 does not exceed the threshold value exceeds a predetermined period, the control unit 10 may shorten the sampling period from the time point tx when the load 28 next stops operating. In this case, since the sampling period when the load 28 stops operating becomes shorter, it is possible to more reliably confirm whether or not the load 28 has operated.

[0051] Further, in the present embodiment, when the control unit 10 specifies the non-operation period TE6 and the period T3, the control unit 10 may shorten the sampling period before and after the timing when the next non-operation period TE6 starts and before and after the end of the non-operation period TE6. In this case, since the sampling period becomes shorter before and after the timing when the load 28 stops operating, it is possible to surely know the timing when the load 28 stops operating.

[0052] Further, in the present embodiment, when the control unit 10 specifies the non-operation period TE6 and the period T3, the control unit 10 may increase the sampling period after the timing when the next non-operation period TE6 starts.

[0053] [Other Embodiments] In the above-described embodiment, the state estimation device 1 provided in the vehicle V estimates the internal resistance value and state of the battery 20, but these processes may be performed by the ECU 3. FIG. 12 is a block diagram showing the configuration of another embodiment of the state estimation system.

[0054] The ECU 3 as an example of the state estimation device has a control unit 30, a storage unit 31, an interface 33, and a bus (not shown). The control unit 30 has a CPU, a ROM, and a RAM, similar to the control unit 10. The CPU, ROM, RAM, storage unit 31, and interface 33 are interconnected by a bus and exchange information therebetween. The storage unit 31 is composed of a non-volatile memory and stores, for example, the aforementioned threshold values.

[0055] The functions of the control unit 30 are realized as functional units by the CPU reading a program from the ROM and executing it. By the CPU executing the program stored in the ROM, in the control unit 30, an acquisition unit 301, an internal resistance estimation unit 302, a specification unit 303, a discharge control unit 304, and a state estimation unit 305 are realized.

[0056] The acquisition unit 301 acquires the voltage value of the battery 20 indicated by the signals output from the voltage sensor 21, the current sensor 22, and the temperature sensor 23 and acquired by the interface 33, the current value of the current flowing from the battery 20, and the temperature of the battery 20. The internal resistance estimation unit 302 estimates the internal resistance value of the battery 20 in the same manner as the internal resistance estimation unit 102. The specifying unit 303 specifies a non-operation period that is a period during which the battery 20 does not discharge to the load 28 and is longer than the discharge period in a predetermined pattern, based on the voltage value and the current value acquired by the acquisition unit 301. The discharge control unit 304 outputs a control signal to the base of the transistor TR1 to control the discharge circuit 24 so that the battery 20 discharges in a predetermined pattern and a current having a predetermined current value flows from the battery 20 outside the period specified by the specifying unit 303. The state estimation unit 305 calculates or estimates OCV, SOC, SOH, SOF, etc. as the state of the battery 20 based on the voltage value and the current value acquired by the acquisition unit 301, the internal resistance value estimated by the internal resistance estimation unit 302, etc., in the same manner as the state estimation unit 105.

[0057] The control unit 30 executes the process of FIG. 5 in the same manner as the control unit 10 to estimate the internal resistance value of the battery 20. Further, the control unit 30 executes the process of FIG. 9 in the same manner as the control unit 10 to specify the non-operation period. Also in this configuration, during the period TE5 in which the load 28 operates, since the process of step S103 is not performed, fluctuations due to the operation of the load are not superimposed on the voltage value and the current value sampled for estimating the internal resistance value, and the internal resistance value can be accurately estimated by discharging with an appropriate current value.

[0058] Also, in the present invention, the non-operation period may be specified by a server device connected to the communication network. FIG. 13 is a block diagram showing the configuration of another embodiment of the state estimation system.

[0059] The communication interface 5 is an interface that performs wireless communication via the communication network 1000 and is connected to the state estimation device 1. The state estimation device 1 is connected to the communication network 1000 via the communication interface 5 and exchanges information with the server device 4.

[0060] The server device 4 includes a control unit 40, a storage unit 41, a communication unit 42, a user interface 43, and a bus (not shown). The control unit 40 has a CPU, a ROM, and a RAM, similar to the control unit 10. The CPU, ROM, RAM, storage unit 41, communication unit 42, and user interface 43 are interconnected by a bus and exchange information therebetween. The communication unit 42 communicates with the state estimation device 1 via the communication network 1000 and exchanges information with the state estimation device 1. The storage unit 41 stores the above-described threshold value. The user interface 43 includes a mouse, a keyboard for inputting information, and a display device for displaying information. Note that the server device 4 may be configured not to have the user interface 43.

[0061] The functions of the control unit 40 are realized as functional units when the CPU reads and executes a program from the ROM. By executing the program stored in the ROM by the CPU, an acquisition unit 401, an internal resistance estimation unit 402, a specifying unit 403, a discharge control unit 404, and a state estimation unit 405 are realized in the control unit 40.

[0062] The acquisition unit 401 acquires the voltage value, current value, and temperature acquired by the acquisition unit 101 and transmitted from the state estimation device 1 via the communication unit 42. The internal resistance estimation unit 402 estimates the internal resistance value of the battery 20. Specifically, the internal resistance estimation unit 402 estimates the internal resistance value of the battery 20 in the same manner as the internal resistance estimation unit 102 based on the voltage value and current value acquired by the acquisition unit 401. The specifying unit 403 specifies, in the same manner as the specifying unit 103, a non-operation period that is a period during which the battery 20 does not discharge with respect to the load 28 and is longer than the discharge period in a predetermined pattern, based on the voltage value and current value acquired by the acquisition unit 401. The discharge control unit 404 transmits the information on the non-operation period specified by the specifying unit 403 to the state estimation device 1 via the communication unit 42. The discharge control unit 104 of the state estimation device 1 controls the discharge circuit 24 so that the battery 20 discharges in a predetermined pattern during the non-operation period. The state estimation unit 405 acquires, via the communication unit 42, the voltage value and current value of the battery 20 acquired by the acquisition unit 101 when the battery 20 is discharging in a predetermined pattern by the discharge circuit 24, from the state estimation device 1, and estimates the state of the battery 20 in the same manner as the state estimation unit 105 based on the acquired voltage value, current value, the internal resistance value estimated by the internal resistance estimation unit 402, and the like.

[0063] FIG. 14 is a sequence diagram for explaining the operation of the state detection system having the configuration shown in FIG. 13. When the battery 20 is in the standby state, the state estimation device 1 transmits the voltage value and current value acquired by the acquisition unit 101 to the server device 4 via the communication interface 5 (step S11).

[0064] The control unit 40 acquires the voltage value and current value transmitted from the state estimation device 1 (step S12). The control unit 40 specifies the non-operation period in the same manner as in the above-described embodiment based on the acquired voltage value and current value (step S13). The control unit 40 transmits the information indicating the specified non-operation period to the state estimation device 1 (step S14).

[0065] The state estimation device 1 acquires information on the non-operation period transmitted from the server device 4, and controls the discharge circuit 24 so that discharge is performed by the battery 20 in a predetermined pattern and a current of a predetermined current value flows from the battery 20 during the non-operation period (step S15). The state estimation device 1 acquires the voltage value measured by the voltage sensor 21 and the current value measured by the current sensor 22 when the battery 20 is discharging in a predetermined pattern by the discharge circuit 24 (step S16), and transmits the acquired voltage value and current value to the server device 4 (step S17).

[0066] The control unit 40 acquires the voltage value and the current value transmitted from the state estimation device 1, estimates the internal resistance value of the battery 20 using the acquired voltage value and current value (step S18), and estimates the state of the battery 20 (step S19). The control unit 40 transmits the estimation results of the internal resistance value and the state of the battery 20 to the ECU 3 (step S20).

[0067] Also in this configuration, during the period TE5 when the load 28 operates, since the process of step S103 is not performed, fluctuations due to the operation of the load are not superimposed on the voltage value and current value sampled for estimating the internal resistance value, and the internal resistance value can be accurately estimated by discharging with an appropriate current value. Note that the processing performed by the server device 4 may be executed by a terminal device such as a personal computer connected to the communication network 1000.

[0068] [Modification Example] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments and can be implemented in various other forms. For example, the present invention may be implemented by modifying the above-described embodiments as follows. Note that the above-described embodiments and the following modification examples may be combined with each other. The present invention also includes those configured by appropriately combining the components of the above-described embodiments and each modification example. Further, additional effects and modification examples can be easily derived by those skilled in the art. Therefore, a broader aspect of the present invention is not limited to the above-described embodiments and modification examples, and various changes are possible.

[0069] In the above-described embodiment, the vehicle V is configured such that only the engine 26 outputs driving force. However, the vehicle V may be, for example, a hybrid vehicle equipped with an electric motor that assists the engine 26 or an electric vehicle driven by an electric motor. In the case of an electric vehicle such as a hybrid vehicle or an electric vehicle, the battery 20 activates a high-voltage system (a system that drives the electric motor) configured by a lithium-ion battery or the like, and the high-voltage system starts the engine 26.

[0070] In the case of an electric vehicle, during running, a voltage stepped down from the drive battery is continuously applied to the auxiliary battery via a DCDC converter. Since this voltage is more stable compared to the voltage of the alternator in an engine vehicle, in a situation where there are no fluctuations in current or voltage due to the operation of the load, it is possible to estimate the internal resistance of the battery by discharging in a predetermined pattern. The situation at this time is basically the same as when the engine of an engine vehicle is in idle stop.

[0071] Also, when the electric vehicle is at rest, it is basically in the same situation as when the engine of an engine vehicle is stopped. However, the electric vehicle may be charged from the outside while at rest. In this case, depending on the vehicle design, a voltage stepped down from the drive battery may be applied in the same state as during running. In that case, although it is the same as during running, since the vehicle is at rest, no discharge of the load 28 occurs due to the driver's operation, so it is considered to be a state suitable for estimating the internal resistance value of the battery 20 by discharging in a predetermined pattern compared to during running. On the other hand, also during charging, various sensors and a microcomputer that communicates with the outside are periodically activated, and fluctuations in current and voltage occur accordingly. Also, it is assumed that this timing is different from the timing when not being charged. Therefore, it is preferable to separately specify a timing convenient for estimating the internal resistance value of the battery 20 by discharging in a predetermined pattern independently of the case when not being charged and use them appropriately according to the situation.

[0072] In the above-described embodiment, when it is not the non-operation period, the processing after step S103 is not performed. However, the present invention is not limited to this configuration. For example, the control unit 10 samples the voltage by the acquisition unit 101, and from the acquired voltage, the time when the load 28 starts operating, and the time when the load 28 stops operating, the control unit 10 identifies the period of the load operation period, which is the period during which the load 28 is operating, and the length of this load operation period. If the length of the load operation period is longer than the period TE3 and the period TE3 does not overlap with the start or end timing of the load operation period, within this load operation period, the discharge circuit 24 may be controlled for the period TE3 so that discharge is performed in a predetermined pattern by the battery 20 and a current of a predetermined current value flows from the battery 20. This load operation period is an example of a non-varying period during which the load 28 operates with power from the battery 20 and the discharge current flowing to the load 28 supplied with power from the battery 20 does not vary.

[0073] FIG. 15 is a diagram showing an example of a voltage waveform measured by the voltage sensor 21 when the discharge circuit 24 is controlled so that discharge is performed in a predetermined pattern by the battery 20 and a current of a predetermined current value flows from the battery 20 within the load operation period TE7, which is a non-varying period. As shown in FIG. 15, when the period TE3 is within the load operation period TE7, within the period TE3, since voltage fluctuations due to discharge to the load 28 do not occur for the discharge in the predetermined pattern, the influence of voltage fluctuations due to the load 28 can be suppressed, and the internal resistance value can be estimated by discharge with an appropriate current value.

[0074] FIG. 16 is a diagram showing an example of a voltage waveform measured by the voltage sensor 21 when the load operation period TE7 starts within the period TE3. When the period TE3 does not fit within the load operation period TE7 in this way, voltage fluctuations due to discharging to the load 28 occur with respect to the discharging of a predetermined pattern during the period TE3. Further, FIG. 17 is a diagram showing an example of a voltage waveform measured by the voltage sensor 21 when the load operation period TE7 ends within the period TE3. When the period TE3 does not fit within the load operation period TE7 in this way, voltage fluctuations due to discharging to the load 28 occur with respect to the discharging of a predetermined pattern during the period TE3.

[0075] Therefore, even when the load operation period TE7 is longer than the period TE3, if the cycle of the load operation period TE7 and the cycle of the period TE3 are such that the period TE3 does not fit within the load operation period TE7, the control unit 10 controls the discharge circuit 24 so that discharging by the battery 20 does not occur in a predetermined pattern within the load operation period TE7.

Description of Reference Numerals

[0076] 1 State estimation device 3 ECU 10 Control unit 11 Storage unit 12 Communication unit 13 Interface 14 Bus 20 Battery 21 Voltage sensor 22 Current sensor 23 Temperature sensor 24 Discharge circuit 28 Load 101, 301, 401 Acquisition unit 102, 302, 402 Internal resistance estimation unit 103, 303, 403 Identification unit 104, 304, 404 Discharge control unit 105, 305, 405 State estimation unit V Vehicle

Claims

1. A state estimation system for estimating the state of a rechargeable battery, comprising: an acquisition unit that acquires a voltage value of the battery and a current value of a current flowing from the battery; a discharge circuit that discharges the battery; a specifying unit that specifies a non-varying period during which a discharge current flowing to a load supplied with power from the battery does not vary, based on at least the voltage value acquired by the acquisition unit and the time at which the voltage value was acquired; a discharge control unit that controls the discharge circuit to discharge the battery such that a current having a predetermined current value flows from the battery during the non-varying period specified by the specifying unit; an internal resistance estimation unit that estimates an internal resistance value of the battery based on the voltage value and the current value acquired by the acquisition unit when the discharge from the battery is being performed at the predetermined current value by the discharge control unit; A state estimation system comprising the above.

2. When the non-varying period is specified, the acquisition unit shortens a period for acquiring the voltage value and the current value during the non-varying period. The state estimation system according to claim 1.

3. When the non-varying period is specified, the acquisition unit shortens a period for acquiring the voltage value and the current value before and after the start and end of the non-varying period. The state estimation system according to claim 1.

4. When the non-varying period is specified, the acquisition unit lengthens a period for acquiring the voltage value and the current value during the non-varying period. The state estimation system according to claim 1.

5. A state estimation device for estimating the state of a rechargeable battery, comprising: an acquisition unit that acquires a voltage value of the battery and a current value of a current flowing from the battery; a discharge circuit that discharges the battery; a specifying unit that specifies a non-varying period during which a discharge current flowing to a load supplied with power from the battery does not vary, based on at least the voltage value acquired by the acquisition unit and the time at which the voltage value was acquired; a discharge control unit that controls the discharge circuit to discharge the battery such that a current having a predetermined current value flows from the battery during the non-varying period specified by the specifying unit; an internal resistance estimation unit that estimates an internal resistance value of the battery based on the voltage value and the current value acquired by the acquisition unit when the discharge from the battery is being performed at the predetermined current value by the discharge control unit; A state estimation device comprising the above.

6. A state estimation method for estimating the state of a rechargeable battery, comprising: An acquisition step of acquiring a voltage value of the battery and a current value of a current flowing from the battery; A specifying step of specifying a non-varying period during which a discharge current flowing to a load supplied with power from the battery does not vary, based on at least the voltage value acquired in the acquisition step and the time at which the voltage value was acquired; A discharge control step of discharging the battery by controlling a discharge circuit that discharges the battery so that a current having a predetermined current value flows from the battery during the non-varying period specified in the specifying step; An internal resistance estimation step of estimating an internal resistance value of the battery based on the voltage value and the current value acquired in the acquisition step when the discharge from the battery is being performed at the predetermined current value in the discharge control step; A state estimation method comprising the above.

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