JP2014074588A - Secondary battery state detection device and secondary battery state detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery state detection device that can detect the state of a secondary battery accurately without consuming power of the secondary battery.SOLUTION: A secondary battery state detection device 1 for detecting a state of a secondary battery installed in a vehicle comprises: discharging means (discharge circuit 15) for discharging the power stored in the secondary battery by switching switches 15a, 15b connected to a terminal of a secondary battery 14; detection means (control section 10) for detecting the state of the secondary battery on the basis of a voltage and current in discharge by the discharging means; and control means (control section 10) for controlling the detection of the state of the secondary battery by controlling the discharging means and the detection means in a period from approach of a user to the vehicle to the start of a motor of the vehicle.

Description

  The present invention relates to a secondary battery state detection device and a secondary battery state detection method.

  Patent Document 1 discloses a technique for detecting the state (life) of a secondary battery by causing the secondary battery to output an alternating current of a predetermined frequency and measuring the impedance of the secondary battery at that time. Yes.

Japanese Patent Laid-Open No. 04-198783

  By the way, in the technique disclosed in Patent Document 1, if the time elapses after the impedance is measured, the state of the secondary battery changes during that time, and the measurement result has an error. Therefore, in the past, measurement is performed at short intervals (for example, 1 hour) to detect the most recent state with few errors, but in such a method, the secondary battery is frequently discharged. Therefore, there is a problem that the accumulated power is consumed. Therefore, it is possible to suppress power consumption by measuring at a long interval (for example, 6 hours), but in that case, as described above, when the time has passed since the measurement, the detection result has an error. There is a point.

  Accordingly, an object of the present invention is to provide a secondary battery state detection device and a secondary battery state detection method capable of accurately detecting the state of the secondary battery without consuming the power of the secondary battery. It is said.

In order to solve the above problems, the present invention provides a secondary battery state detection device for detecting a state of a secondary battery mounted on a vehicle, by switching a switch connected to a terminal of the secondary battery. A discharging means for discharging the electric power stored in the secondary battery, a detecting means for detecting the state of the secondary battery based on a voltage and current when the discharging means is discharging, and a user on the vehicle Control means for controlling to detect the state of the secondary battery by controlling the discharge means and the detection means during a period from the time of approach until the prime mover of the vehicle is started. And
According to such a configuration, the state of the secondary battery can be accurately detected without consuming the power of the secondary battery.

Further, according to one aspect of the present invention, when the charging rate of the secondary battery is outside a predetermined range, the control unit is configured to start the prime mover of the vehicle after the user approaches the vehicle. In this period, the state of the secondary battery is not detected.
According to such a configuration, it is possible to accurately detect the state by excluding a range having a large error.

According to another aspect of the present invention, the control unit detects the state of the secondary battery by controlling the discharge unit and the detection unit when a current flowing from the secondary battery to the load increases by a predetermined amount. It is characterized by performing control.
According to such a configuration, when the user approaches and a current flows through the load, the state of the secondary battery can be detected.

Further, according to one aspect of the present invention, the control unit determines that the current increases by a predetermined amount when a current flows through an actuator for locking or unlocking the door of the vehicle. Control is performed to detect the state of the secondary battery.
According to such a configuration, it is possible to detect the state of the secondary battery by detecting that the user has approached and the door has been unlocked.

In addition, according to one aspect of the present invention, when the control unit receives a signal transmitted from a key for unlocking or locking the vehicle door of the user and succeeds in authentication, the discharge unit And controlling the detection means to detect the state of the secondary battery.
According to such a configuration, the state of the secondary battery can be detected when a legitimate user approaches the vehicle.

In addition, one aspect of the present invention is characterized by having a correction unit that corrects the state of the secondary battery detected by the detection unit according to the state of the secondary battery.
According to such a configuration, the state of the secondary battery can be detected more accurately by correction.

According to another aspect of the present invention, there is provided a secondary battery state detection method for detecting a state of a secondary battery mounted on a vehicle, wherein the secondary battery is stored in the secondary battery by switching a switch connected to a terminal of the secondary battery. A discharge step for discharging the generated power, a detection step for detecting a state of the secondary battery based on a voltage and a current when the discharge is performed in the discharge step, and a user approaching the vehicle, And a control step of performing control to detect the state of the secondary battery by controlling the discharge step and the detection step during a period until the prime mover of the vehicle is started.
According to such a method, the state of the secondary battery can be accurately detected without consuming the power of the secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, the secondary battery state detection apparatus and secondary battery state detection method which can detect the state of a secondary battery correctly, without consuming the electric power of a secondary battery can be provided. .

It is a figure which shows the structural example of the secondary battery state detection apparatus which concerns on embodiment of this invention. It is a figure which shows the detailed structural example of the discharge circuit shown in FIG. It is a figure which shows the relationship between SOC of a secondary battery, and internal impedance. It is a flowchart for demonstrating an example of the process performed in embodiment of this invention.

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

(A) Description of Configuration of Embodiment FIG. 1 is a diagram showing a power supply system of a vehicle having a secondary battery state detection device according to an embodiment of the present invention. In this figure, the secondary battery state detection 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 detects the state of the secondary battery 14. To do. Here, the control unit 10 controls the discharge circuit 15 and refers to outputs from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 to detect the state of the secondary battery 14. Moreover, the control part 10 inputs an IG (Ignition) signal, a door signal, and a communication signal, and performs the state detection process of the secondary battery 14 based on these signals.

  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 ambient environmental temperature, and notifies the control unit 10 of it. As will be described later, the discharge circuit 15 is configured by connecting two switches and a resistance element in series, and the control unit 10 controls the on / off of these switches to intermittently discharge the secondary battery 14. Let The control unit 10 obtains the internal impedance of the secondary battery 14 from the voltage and current when intermittent discharge is performed, and detects the state of the secondary battery 14 based on the obtained internal impedance.

  The secondary battery 14 is composed of, for example, a liquid lead acid battery using lead dioxide as the positive electrode (anode plate), spongy lead as the negative electrode (cathode plate), and dilute sulfuric acid as the electrolyte, and is charged by the alternator 16. The starter motor 18 is driven to start the engine 17 and supply power to the load 19. In addition, you may use secondary batteries (a nickel cadmium battery, a nickel metal hydride battery, a lithium ion battery etc.) other than lead acid battery. 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 engine 17 is constituted by, for example, a reciprocating engine such as a gasoline engine and a diesel engine as a prime mover, a rotary engine, or the like. The engine 17 is started by a starter motor 18 and drives a driving wheel via a transmission to give a propulsive force to the vehicle. The alternator 16 is driven 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 configured by, for example, an electric steering motor, a defogger, 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 showing a configuration example of the discharge circuit shown in FIG. As shown in this figure, the discharge circuit 15 is configured by connecting two switches 15a and 15b and a resistance element 15c in series. Here, the switches 15a and 15b are constituted by, for example, semiconductor switches such as FET (Field Effect Transistor) or IGBT (Insulated Gate Bipolar Transistor) or electromagnetic switches such as relays, and are supplied from terminals B and C of the control unit 10. Depending on the control signal to be turned on or off. The resistance element 15c allows a predetermined discharge current to flow from the secondary battery 14 when both the switches 15a and 15b are turned on. The resistance element 12 a constitutes the current sensor 12, generates a voltage corresponding to the flowing current, and supplies the voltage to the terminals D and E of the control unit 10. One end of the resistance element 12a and the terminal E are grounded. By detecting the voltage generated in the resistance element 12a, the current flowing through the resistance element 12a can be known. The control unit 10 operates as the voltage sensor 11 that detects the voltage of the secondary battery 14 by detecting the voltage applied to the terminals A and D.

(B) Description of Operation of Embodiment Next, the operation of this embodiment will be described. In the following, the outline of the operation of the present embodiment will be described, and then the details of the operation will be described with reference to FIGS.

  In the present embodiment, the vehicle is stopped and, for example, the user approaches the vehicle in a state in which the load 19 is shifted to a sleep mode (an operation mode in which the current flowing through the load 19 is reduced and consumption of the secondary battery 14 is suppressed). After that, during the period until the engine 17 is started by the starter motor 18, the discharge circuit 15 performs pulse discharge to detect the state of the secondary battery 14.

  For example, when a user returns home from a company, parks a vehicle in a parking lot at home, and goes to work the next morning, the user possesses a key having a wireless communication function for unlocking (or locking) the door key of the vehicle. When the vehicle approaches the vehicle, the radio wave transmitted from the key is received on the vehicle side, and when it is authenticated as a valid user (for example, the ID (Identification) transmitted from the key is stored on the vehicle side). The door ID is unlocked).

  The control unit 10 detects any of various state changes that occur on the vehicle side, triggered by the approach of the user holding the key. State changes include, for example, successful authentication with the key, generation of a signal indicating unlocking due to successful authentication, operation of the actuator based on the signal indicating unlocking, change in current due to operation of the actuator, lighting of the indoor lamp It is possible to detect that the door has been opened by the user after unlocking, that the user has been seated on the seat, that the ignition key has been turned on, and the like as state changes. Of course, a plurality of combinations may be used instead of any of these for the sake of accuracy. Note that when the ignition key is rotated to the starting position and the starter motor 18 starts rotating, a very large current flows from the secondary battery 14 to the starter motor 18. Impedance cannot be measured accurately. For this reason, the measurement of the internal impedance is executed during a period until the starter motor 18 is rotated.

  When the control unit 10 detects any of the above-described state changes of the vehicle, the control unit 10 first determines whether or not the state of charge (SOC) of the secondary battery 14 is within a predetermined range. If it is not within the predetermined range, the internal impedance is not measured.

  FIG. 3 is a diagram showing the relationship between the SOC and the internal impedance. A black circle indicates an internal impedance value at each SOC value. As shown in this figure, the value of the internal impedance changes abruptly in the region surrounded by the solid-line ellipse. More specifically, the internal impedance changes abruptly when the SOC is less than 20% and when the SOC is close to 100% (a state near full charge). For this reason, if the internal impedance is measured in such a region, an accurate value cannot be obtained, and thus the state of the secondary battery 14 cannot be accurately detected. The characteristics shown in FIG. 3 are different from those of the graph itself, although the offset value of the graph (position where the black circle is plotted on the vertical axis) varies depending on the size, capacity, aging, and environmental temperature of the secondary battery. The shape is substantially the same. Therefore, the determination can be made based on the same reference regardless of the size of the secondary battery. Therefore, in this embodiment, measurement of internal impedance is not executed when the SOC is less than 20% and when the SOC is close to 100%. Of course, for accuracy, for example, the case of less than 30% or 25% may be excluded.

  When the SOC is neither less than 20% nor near 100%, the control unit 10 turns on the switch 15b of the discharge circuit 15 and then turns the switch 15b on and off intermittently. The secondary battery 14 is discharged intermittently. At this time, the discharge current can be detected by a voltage drop at both ends of the resistance element 12a. Further, the voltage of the secondary battery 14 can be detected by the voltage sensor 11.

  The control unit 10 detects the voltage and current of the secondary battery 14 during the pulse discharge, and obtains the internal impedance of the secondary battery 14. Then, with respect to the obtained internal impedance, the correction considering the stratification of the secondary battery 14 (stratification correction), the correction considering the polarization of the secondary battery 14 (polarization correction), and the dark current of the load 19 Correction in consideration (dark current correction) and correction based on the temperature detected by the temperature sensor 13 are performed. Based on the corrected internal impedance, the state of the secondary battery 14 (for example, SOC (State of Charge) or SOH (State of Health)) is calculated.

  The state of the secondary battery 14 detected in this way is transmitted to, for example, an upper control ECU (Electronic Control Unit) not shown. The control ECU controls the power generation voltage of the alternator 16 based on the SOC detected in this way, and controls charging of the secondary battery 14 so that the SOC falls within a predetermined range. In addition, based on the detected SOH, the control ECU performs a display for prompting the user to replace the secondary battery 14 when the replacement time is approaching.

  As described above, in the present embodiment, the state of the secondary battery 14 is detected during the period from when the user approaches the vehicle until the engine 17 is started. For this reason, since the state of the secondary battery 14 is detected immediately before the user uses the vehicle, the alternator 16 is controlled based on the latest information, the SOH is estimated based on the latest information, and the replacement time is determined. Can be notified accurately. In addition, since the detection is performed only immediately before starting the engine 17, it is possible to prevent the secondary battery 14 from being consumed.

  Next, the detailed operation of the present embodiment will be described with reference to FIG. FIG. 4 is a diagram for explaining the flow of processing executed in the control unit 10 shown in FIG. When the processing of this flowchart is started, the following steps are executed.

  In step S1, the control unit 10 determines whether or not the authentication is successful with the key having the communication function. If the authentication is successful (step S1: Yes), the control unit 10 proceeds to step S2, and otherwise In the case (step S1: No), the same processing is repeated. For example, when a user who possesses a key having a communication function approaches a parked vehicle and enters a communicable area, an authentication process is executed between the key and the communication unit of the vehicle. If the user is authenticated, it is determined that the authentication is successful (Yes), and the process proceeds to step S2.

  In addition, it is possible to use the case where communication is established between the key and the vehicle instead of the case where the authentication is successful, but in this case, other users who have the same type of vehicle key. Since communication is established even when the two approach each other, it is more preferable that the determination criterion is that authentication is established.

  In step S2, the control unit 10 determines whether or not the charging rate (SOC) is within a predetermined range. If the charging rate (SOC) is within the predetermined range (step S2: Yes), the control unit 10 proceeds to step S3. In (Step S2: No), the process ends. For example, when the SOC is 20% or more and is not fully charged (approximately 100%), the process proceeds to step S3 assuming that the SOC is within a predetermined range, and when the SOC is less than 20% or fully charged (approximately 100%). Ends the process.

  In step S3, the control unit 10 turns on the switch 15a, intermittently turns on / off the switch 15b, detects a change in current at that time based on a voltage drop of the resistance element 12a, and detects a voltage sensor. 11 detects the voltage.

  In step S4, the control unit 10 determines whether or not to continue the measurement process. When the measurement is continued (step S4: Yes), the control unit 10 returns to step S3 and repeats the same process, otherwise ( In step S4: No), the process proceeds to step S5.

  In step S5, the control unit 10 calculates the internal impedance of the secondary battery 14 based on the current value and voltage value of the secondary battery 14 measured in step S3.

  In step S6, the control unit 10 performs the stratification correction, which is a correction considering the stratification of the secondary battery 14, and the correction considering the polarization of the secondary battery 14 with respect to the internal impedance value obtained in step S5. A certain polarization correction, a dark current correction that is a correction considering the dark current of the load 19, and a temperature correction that is a correction based on the temperature detected by the temperature sensor 13 are executed. By these corrections, an internal impedance value that is not affected by stratification or the like can be obtained.

  In step S7, the control unit 10 detects the SOC and SOH that are the states of the secondary battery 14 based on the internal impedance value corrected in step S6.

  In step S8, the control unit 10 notifies each unit of the state of the secondary battery 14 obtained in step S7. Specifically, the control unit 10 notifies the ECU, which is a higher-level device, of the SOC and SOH values detected in step S7. The ECU controls the voltage generated by the alternator 16 based on the notified SOC so as to control the charge so that the SOC falls within a desired range. If the SOH is equal to or lower than a predetermined value, the ECU performs secondary control. The user is notified that the battery 14 needs to be replaced.

  According to the above process, when the user who has the key having the communication function approaches the vehicle and succeeds in authentication between the key and the vehicle, the measurement process of the internal impedance of the secondary battery 14 is executed. For this reason, since the latest state of the secondary battery 14 can be detected by one measurement immediately before the user uses the vehicle, the power consumption of the secondary battery 14 is reduced and the state is accurately determined. Can be detected. Thereby, since the alternator 16 is controlled based on an accurate SOC value, fuel consumption can be improved by reducing unnecessary charging opportunities. In addition, since replacement of the secondary battery 14 can be prompted based on an accurate SOH value, it is possible to reliably prevent the engine 17 from starting due to deterioration of the secondary battery 14.

(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, in the above embodiment, the discharge circuit 15 is configured independently of the control unit 10, but these may be integrated.

  In the above embodiment, the two switches 15a and 15b are provided. However, the discharge may be performed by one switch.

  In the above embodiment, the detection is not performed when the SOC is less than 20%. For example, the detection is not performed when the SOC is less than 30%. If it is 20% or less, it may not be executed.

  Further, in the above embodiment, in the process of FIG. 4, when the key authentication is successful, the state detection process of the secondary battery 14 is executed. However, with the approach of the user holding the key as a trigger, Detection processing can be executed by detecting any of various state changes that occur on the vehicle side. As described above, the state change includes the successful authentication with the key, the generation of a signal indicating unlocking due to the successful authentication, the operation of the actuator based on the signal indicating the unlocking, and the change in current due to the operation of the actuator. Detecting as a change in state such as lighting of a room light, opening of a door by a user after unlocking, sitting of a user on a seat, turning on of an ignition key based on an IG signal, etc. it can. Further, the state detection process may be executed based on a communication signal from the host unit that notifies that these state changes have been detected. Of course, the detection process may be executed not only when any of these is detected, but also with a plurality of combinations.

  In the present specification, the “period from when the user approaches the vehicle until the prime mover of the vehicle is started” refers to a key that automatically authenticates the approach of the key as described above. The period from when the user holding the key approaches the vehicle until the engine 17 is started. In addition, the key is not automatically authenticated when approaching, but is a key that is locked or unlocked when a signal is transmitted by operating the operating unit to lock or unlock the door. This is the period from when the engine 17 is started. Furthermore, in the case of a key that does not have a communication function and is manually unlocked by inserting the key into the keyhole, it means a period from when the key is inserted into the keyhole until the engine 17 is started.

  In the above embodiment, as shown in FIG. 2, the resistance element 12 a is arranged on the ground side, but may be arranged on the positive electrode terminal side of the secondary battery 14, for example. Further, regarding the connection of the switches 15a and 15b and the resistance element 15c, a connection method other than that shown in FIG. 2, for example, the switches 15a and 15b may be directly connected, and the resistance element 15c may be connected in series thereto.

DESCRIPTION OF SYMBOLS 1 Secondary battery state detection apparatus 10 Control part (detection means, determination means, correction means)
DESCRIPTION OF SYMBOLS 11 Voltage sensor 12 Current sensor 13 Temperature sensor 14 Secondary battery 15 Discharge circuit (discharge means)
16 Alternator 17 Engine 18 Starter motor 19 Load

Claims (7)

In the secondary battery state detection device that detects the state of the secondary battery mounted on the vehicle,
Discharging means for discharging power stored in the secondary battery by switching a switch connected to a terminal of the secondary battery;
Detecting means for detecting the state of the secondary battery based on the voltage and current when the discharging means is discharging;
Control means for controlling the discharge means and the detection means to detect the state of the secondary battery during a period from when the user approaches the vehicle until the prime mover of the vehicle is started;
A secondary battery state detection device comprising:   When the charging rate of the secondary battery is out of a predetermined range, the control means is configured to operate the second battery even if it is a period from when the user approaches the vehicle until the prime mover of the vehicle is started. The secondary battery state detection device according to claim 1, wherein detection of the state of the secondary battery is not executed.   The control means performs control for detecting the state of the secondary battery by controlling the discharge means and the detection means when a current flowing from the secondary battery to the load increases by a predetermined amount. The secondary battery state detection device according to claim 1 or 2.   The control means controls the discharging means and the detecting means to control the state of the secondary battery, assuming that the current increases by a predetermined amount when an electric current flows through an actuator for locking or unlocking the door of the vehicle. The secondary battery state detection device according to claim 3, wherein control for detecting the battery is performed.   The control means controls the discharge means and the detection means when receiving a signal transmitted from a key for unlocking or locking the vehicle door of the user and succeeding in authentication. The secondary battery state detection device according to claim 1, wherein control for detecting a state of the secondary battery is performed.   The secondary battery according to claim 1, further comprising a correcting unit that corrects the state of the secondary battery detected by the detecting unit according to the state of the secondary battery. Battery state detection device. In a secondary battery state detection method for detecting the state of a secondary battery mounted on a vehicle,
A discharging step of discharging power stored in the secondary battery by switching a switch connected to a terminal of the secondary battery;
A detecting step for detecting a state of the secondary battery based on a voltage and a current when the discharging is performed by the discharging step;
A control step for controlling the discharge step and the detection step to detect the state of the secondary battery during a period from when the user approaches the vehicle until the prime mover of the vehicle is started;
A secondary battery state detection method comprising:

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