JP6674139B2 - Vehicle and its battery state detection system - Google Patents

Description

  The present invention relates to a vehicle and a battery state detection system thereof, and more particularly to a vehicle and a battery state detection system capable of accurately detecting a state of charge based on battery parameters regardless of individual differences due to manufacturing variations of a vehicle-mounted battery. .

  In recent years, vehicles equipped with an automatic stop and restart (ISS: idle stop / start) function of the engine have become widespread in order to cope with the reduction of exhaust gas from engine vehicles, and lead-acid batteries on vehicles are kept in an idle-stoppable state. Technology is desired.

  That is, in an automobile (vehicle) equipped with the ISS, loads such as an air conditioner and a car stereo while the engine is stopped are all covered by the electric power from the lead battery. For this reason, the deep discharge of the lead battery increases as compared with the related art, and the state of charge of the lead battery tends to decrease.

  Since the output of a lead battery depends on its state of charge, if the state of charge of the lead battery drops while the engine is stopped, it may not be possible to obtain sufficient output to start the engine and restart after the engine is stopped. There is.

  Therefore, in order to maintain a state in which the engine can be restarted, the state of charge of the lead battery (for example, SOC: State Of Charge) is calculated (estimated), and the presence or absence of an output necessary for starting the engine is monitored. If there is an output necessary for starting, the idle stop is permitted.If there is no output necessary for starting the engine, the idle stop is prohibited and a signal such as charging a lead battery is transmitted to the computer on the vehicle side. There is a need.

  Patent Literatures 1 and 2 disclose techniques for determining the state of charge of a lead battery by measuring its open circuit voltage (OCV). In this prior art, the charging state is calculated by substituting the OCV measured when the vehicle is stopped into the linear expression, utilizing the fact that the relationship between the charging state and the OCV is expressed by a linear expression.

  Patent Literature 3 discloses a technique for estimating a state of charge of a lead battery by measuring an internal resistance R of the lead battery. In this prior art, the relationship between the state of charge and the internal resistance R is represented by an approximate expression, and the state of charge is calculated by substituting R measured when the vehicle is stopped into the approximate expression.

JP-A-4-264371 JP 2009-241633 A Patent No. 3687628

  FIG. 7 is a diagram showing the relationship between the measured values of OCV and SOC for a plurality of batteries of the same specifications. Even for batteries of the same specifications, due to variations in manufacturing conditions and storage conditions, etc. It is known that there is an individual difference in the relationship between OCV and SOC.

  Therefore, it is difficult to accurately estimate the SOC from the OCV with one approximation formula. In particular, if the state of charge is estimated to be higher than the actual state, the engine cannot be started by the battery power at the time of the idle stop / start. May fall into that situation. Such a phenomenon applies to the relationship between the internal resistance R and the SOC.

  An object of the present invention is to solve the above technical problem and provide a vehicle capable of accurately detecting its charge state based on battery parameters such as an open circuit voltage OCV and an internal resistance R and a charge state detection system thereof. is there.

  In order to achieve the above object, the present invention is characterized in that a battery state detection system for detecting a state of charge of a vehicle-mounted battery has the following configuration.

  (1) Means for measuring the open-circuit voltage of the vehicle-mounted battery, means for storing the standard correspondence between the open-circuit voltage and the state of charge, and Means for calculating a correction coefficient for correcting the relationship between the state of charge and the open circuit voltage; means for correcting the measurement result of the open circuit voltage of the vehicle-mounted battery based on the correction coefficient; Means for determining the state of charge by applying to

  (2) further comprising means for detecting the state of deterioration of the vehicle-mounted battery, the means for storing the correspondence, storing a standard correspondence between the open circuit voltage and the state of charge of the vehicle-mounted battery for each deterioration state, The means for determining the state of charge determines the state of charge by applying the corrected open circuit voltage to the correspondence corresponding to the state of deterioration.

  According to the present invention, the following effects are achieved.

  (1) While a standard correspondence between the battery parameters and the state of charge is obtained and registered in advance, a correction coefficient K for the correspondence is obtained based on the battery parameter at the time of full charge specific to each battery, and this correction coefficient Since the measurement result of the battery parameter is calibrated by K, the state of charge can be accurately estimated based on the typical correspondence between the previously obtained battery parameter and the state of charge regardless of the individual difference of each battery. become.

  (2) An approximate expression or map representing the correspondence between the battery parameters and the state of charge is constructed and registered for each state of deterioration of the battery, and the state of charge is estimated based on the correspondence according to the state of deterioration. Thus, the state of charge of the battery can be accurately estimated based on the battery parameters regardless of the state of deterioration of the battery.

1 is a functional block diagram illustrating a configuration of a battery state detection system 1 according to an embodiment of the present invention. FIG. 3 is a block diagram showing a function of estimating a state of charge SOC. 4 is a flowchart showing a procedure for estimating a state of charge SOC according to an embodiment of the present invention. FIG. 10 is a diagram illustrating errors between SOC estimated values calculated using a correction coefficient Kocv and SOC true values calculated without using the five sample batteries with respect to true values. FIG. 4 is a diagram showing a relationship between an internal resistance R of a lead battery and a state of charge SOC. FIG. 9 is a diagram showing errors between SOC estimated values calculated using a correction coefficient K _R and true values of SOC estimated values not used for five sample batteries. FIG. 4 is a diagram showing that there is an individual difference in the relationship between the open circuit voltage OCV and the state of charge SOC of a lead battery.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing a configuration of a main part of a battery state detection system 1 according to an embodiment of the present invention. Here, the present invention is applied to a gasoline engine vehicle equipped with a lead battery 12 having an ISS function. The application will be described as an example.

  The battery state detection system 1 includes a temperature sensor 2 such as a thermistor for measuring the temperature of the lead battery 12, a voltage measurement unit 3 having a differential amplifier circuit and the like and connected to an external terminal of the lead battery 12, a Hall element and the like. A main component is a microcomputer (hereinafter referred to as a microcomputer) 10 for detecting the battery state of the current sensor 4 and the lead battery 12.

  The lead battery 12 has a substantially rectangular battery case serving as a battery container, and a total of six sets of electrode plates are accommodated in the battery case. As the material of the battery case, for example, a polymer resin such as polyethylene (PE) can be used. In each electrode plate group, a plurality of negative electrode plates and positive electrode plates are stacked with a separator interposed therebetween, and the cell voltage is 2.0 V. For this reason, the nominal voltage of the lead battery 12 is set to 12V. The upper part of the battery case is adhered or welded to an upper lid made of a polymer resin such as PE which seals the upper opening of the battery case. A rod-shaped positive electrode terminal and a negative electrode terminal for supplying electric power to the outside using the lead battery 12 as a power supply are provided upright on the upper lid. Note that the above-described temperature sensor is fixed to the side surface or the bottom surface of the battery case.

  The positive terminal of the lead battery 12 is connected to the center terminal of an ignition switch (hereinafter, IGN) 5 via the current sensor 4. The IGN5 has an OFF terminal, an ON / ACC terminal, and a START terminal separately from the center terminal, and the center terminal and any one of the OFF, ON / ACC, and START terminals can be switched and connected in a rotary manner. .

  The START terminal is connected to an engine start cell motor (starter) 9. The starter motor 9 can transmit a rotational driving force to the rotation shaft of the engine 8 via a clutch mechanism (not shown). The ON / ACC terminal is connected to one end of a generator 7 that generates electric power by rotation of the engine 8 via an auxiliary device 6 such as an air conditioner, a radio, a lamp, and a regulator including a rectifying element that allows a current to flow in one direction. ing. That is, the anode side of the regulator is connected to one end of the generator 7, and the cathode side is connected to the ON / ACC terminal.

  The rotating shaft of the engine 8 can transmit power to the generator 7 via a clutch mechanism (not shown). For this reason, when the engine 8 is in a rotating state, the generator 7 operates via the clutch mechanism, and the generated power is supplied (charged) to the auxiliary machine 6 and the lead battery 12. The OFF terminal is not connected to any of them.

  The output of the voltage measuring unit 3 is connected to an A / D converter built in the microcomputer 10. The outputs of the temperature sensor 2 and the current sensor 4 are connected to A / D converters built in the microcomputer 10, respectively. For this reason, the microcomputer 10 can take in the digital value of the voltage and temperature of the lead battery 12 and the current flowing through the lead battery 12 at predetermined time intervals. The microcomputer 10 can communicate with the host vehicle control system 11 via I / O.

  The microcomputer 10 functions as a CPU that functions as a central processing unit, a ROM in which a basic control program of the battery state detection system 12 and program data such as maps and mathematical expressions described later are stored, and serves as a work area of the CPU and temporarily stores data. It is configured to include a storage RAM, a nonvolatile EEPROM, and the like.

  The other end of the generator 7, the starter 9 and the auxiliary machine 6, the negative terminal of the lead battery 12, and the microcomputer 10 are connected to the ground (the same potential as the chassis of the automobile). Note that the microcomputer 10 of the present embodiment samples the voltage, current, and temperature at predetermined time intervals (for example, the voltage and current are each at 2 ms intervals and the temperature is at 1 second intervals), and stores the sampling results in the RAM. . The current is divided into a discharge current and a charge current, and the respective integrated values are calculated.

  The CPU mounted on the microcomputer 10 determines the terminal position based on the voltage of the IGN 5, and further detects the engine state. If the IGN 5 outputs a signal representing the terminal position, the engine state may be detected based on the signal or a signal from the vehicle control system 11. Generally, in a vehicle having an internal combustion engine such as a gasoline engine vehicle or a diesel engine vehicle, electric power is supplied from a lead battery and a cell motor is turned to start the engine.

  After a predetermined time during which the polarization reaction of the lead battery 12 is eliminated after the engine is stopped, the CPU takes in the terminal voltage of the lead battery 12 measured via the voltage measuring unit 3 as the open circuit voltage OCV, and thereafter, the predetermined OCV fetching is repeated by a timer interrupt at regular intervals, and at other times, only the timer is activated and the system enters a power saving mode in which no control operation is performed.

  FIG. 2 is a block diagram showing a function of the microcomputer 10 estimating the state of charge SOC of the battery 12 based on the OCV of the battery 12, wherein the CPU of the microcomputer 10 stores programs and various data stored in ROM or EEPROM in advance. It is realized by operating based on.

  In the present embodiment, the relationship between the OCV and the SOC is determined for a number of lead batteries having the same specifications as the vehicle-mounted battery 12 while changing the environmental temperature, and these are statistically processed to obtain a reference temperature (for example, 25 ° C.). A typical or standard correspondence between the OCV and the SOC in C) is obtained, and this is registered in the correspondence storage unit 101 in advance in an approximate expression or a map format.

  The SOH calculation unit 103 periodically calculates a battery health state SOH (State Of Health). For SOH of lead batteries, apply the measurement result of internal resistance R to SOH map 102 showing the relationship between internal resistance R and SOH, which was measured in advance in a number of deteriorated states for many lead batteries with the same specifications as on-board batteries It is required by doing. The SOH of a lead battery is generally defined as the deteriorated product full charge capacity / new product full charge capacity x 100%, and is expressed as a function of internal resistance R, temperature T, and open circuit voltage OCV as shown in the following equation (1). You.

  The new battery determining unit 104 determines whether the lead battery 12 mounted on the vehicle has been replaced with a new battery. In the present embodiment, the updated value of the SOH calculated by the SOH calculating unit 103 is compared with the previous SOH, and when the SOH is rejuvenated, it is determined that the onboard battery has been replaced with a new one.

  The OVC measurement unit 105 calculates an average value OCVave0 based on a plurality of OCVs measured at a timing when the polarization reaction of the battery is eliminated and the OVC is stable. The correction coefficient calculation unit 106 applies the open circuit voltage OCVmap in the fully charged state determined from the standard correspondence relationship and the average value OCVave0 of the open circuit voltage OCV measured by the OCV measurement unit 105 to the following equation (2). To calculate the correction coefficient Kocv.

  The OCV calibrating unit 107 calculates the calibrated OCV'0 by applying the current open circuit voltage OCV0 and the correction coefficient Kocv to the following equation (3).

  The SOC calculation unit 108 calculates the state of charge SOC of the lead battery 12 by applying the calibrated OCV'0 to the approximate expression or map of the correspondence, and outputs the result.

  FIG. 3 is a flowchart showing a procedure for estimating the state of charge SOC according to an embodiment of the present invention. In step S1, a new lead-acid battery 12 is mounted on the vehicle based on the SOH calculated by the SOH calculation unit 103. The new battery determination unit 104 determines whether or not the battery has been replaced.

  If the battery has been replaced with a new battery, the process proceeds to step S2, and the elapsed time after the engine is stopped is referred to. As a result, if it is determined that the time required for the polarization reaction of the battery to be eliminated (for example, 2 hours or more) has elapsed, the process proceeds to step S3, where the OCV measuring unit 105 measures the current open circuit voltage OCV0. Is done.

  In step S4, the counter of the number of measurements n is incremented. In step S5, it is determined whether the number of measurements n has reached five. If less than five times, the process returns to step S3, and the OCV measurement is repeated at a predetermined cycle (for example, one second). Thereafter, when the number of measurements n reaches five, the process proceeds to step S6, and the average value OCVave0 of the remaining OCV0 excluding the minimum value OCVmin and the maximum value OCVmax from the five measurement results is calculated.

  In step S7, the correction coefficient Kocv is calculated by substituting the average value OCVave0 into the above equation (2). In step S8, the calibrated OCV'0 is calculated by applying the open circuit voltage OCV0 and the correction coefficient Kocv to the above equation (3). In step S9, by applying the calibrated OCV'0 to the approximate expression or map of the correspondence, the state of charge SOC in which the individual difference of the battery is compensated is calculated.

  FIG. 4 shows an error (estimated value) of each of the SOC estimated values (upper row) calculated without using the correction coefficient Kocv and the SOC estimated values (lower row) calculated without using the correction coefficient Kocv for the five sample batteries. FIG. 4 shows true values), and it can be seen that the error of the estimated SOC value is reduced by applying the present invention.

  As described above, according to the present embodiment, the correction coefficient Kocv is determined based on the open circuit voltage OCV at the time of full charge specific to each battery, and the OCV measurement result is calibrated by the correction coefficient Kocv. Regardless of the individual difference, the charging state of the vehicle-mounted battery can be accurately estimated based on the OCV with one approximation formula or map.

  In the above embodiment, the description has been made assuming that the OCV is used as the battery parameter for estimating the state of charge of the battery. However, the present invention is not limited to this, and as shown in FIG. Similarly, the internal resistance R of the battery that shows a predetermined correlation with the state of charge SOC for each environmental temperature may be employed instead of the open circuit voltage OCV.

In this case, the relationship between the internal resistance R and the state of charge SOC is determined for a number of batteries having the same specifications as the vehicle-mounted battery while changing the environmental temperature T, and these are statistically processed to obtain the internal temperature at the reference temperature. An approximate expression or map representing a standard correspondence between the resistance R and the state of charge SOC may be registered in the correspondence storage unit 101. Then, a correction factor K _R relating to the internal resistance R in the same procedure as described above, may be calibrated internal resistance R based on the most recent value of the internal resistance R and the correction coefficient K _R.

6, with respect to five samples the battery, an error between the true value of the correction coefficient K _R SOC estimation value calculated using (top) and the correction coefficient SOC estimation value calculated without using K _R (bottom) ( estimate - a view showing a true value), it can be seen that error in SOC estimation value is decreased by using the correction coefficient K _R.

  By the way, in the above embodiment, the standard and typical correspondence between the open circuit voltage OCV or the internal resistance R and the state of charge SOC has been described as the only one. Alternatively, it is known that the relationship between the internal resistance R and the state of charge SOC differs depending on the state of deterioration of the battery.

  Therefore, the relationship between the open circuit voltage OCV or the internal resistance R and the state of charge SOC is determined for a large number of batteries having the same specifications as the vehicle-mounted batteries and having different deterioration states while changing the environmental temperature T, and these are statistically processed. Accordingly, an approximate expression or a map representing the correspondence between the open circuit voltage OCV or the internal resistance R at the reference temperature and the state of charge SOC is constructed for each deterioration state of the battery, registered in the correspondence storage unit 101, and The state of charge SOC may be estimated based on the correspondence relationship according to the state. The above-mentioned health condition SOH can be adopted as an index representing the deterioration state of the lead battery.

  In this way, the state of charge SOC can be accurately estimated based on the open circuit voltage OCV or the internal resistance R regardless of the state of deterioration of the battery.

  DESCRIPTION OF SYMBOLS 1 ... Battery state detection system, 2 ... Temperature sensor, 3 ... Voltage measurement part, 4 ... Current sensor, 5 ... IGN, 6 ... Auxiliary equipment, 7 ... Generator, 8 ... Engine, 9 ... Engine start cell motor, 10 ... Microcomputer, 12 lead battery, 101 correspondence storage unit, 102 SOH map, 103 SOH calculation unit, 104 new battery discrimination unit, 105 OVC measurement unit, 106 correction coefficient calculation unit, O107 CV calibration unit , 108 ... SOC calculation unit

Claims (7)

In a battery state detection system that detects the state of charge of the vehicle battery,
Means for measuring the open circuit voltage of the vehicle battery;
Means for storing a standard correspondence between the open circuit voltage of the vehicle battery and the state of charge;
Means for determining whether the in-vehicle battery has been replaced with a new one,
When the vehicle-mounted battery is replaced with a new one, the open-circuit voltage of the new vehicle-mounted battery is measured, and a correction coefficient for correcting the relationship between the result of the measurement and the open-circuit voltage in the fully charged state in the correspondence relationship is calculated. Means for calculating;
Means for correcting the measurement result of the open circuit voltage of the vehicle-mounted battery, based on the correction coefficient,
Means for calculating a state of charge by applying the corrected open circuit voltage to the correspondence. The correspondence represents the relationship between the open circuit voltage and the state of charge at the reference temperature,
The correction coefficient is a converted value of the reference temperature,
The battery state detection system according to claim 1, wherein the means for determining the state of charge determines a state of charge at the reference temperature. Further comprising means for detecting the state of deterioration of the vehicle-mounted battery,
The means for storing the correspondence relationship stores a standard correspondence relationship between the open circuit voltage of the vehicle-mounted battery and the state of charge for each deterioration state,
3. The battery state detection system according to claim 1, wherein the means for obtaining the state of charge obtains the state of charge by applying the corrected open circuit voltage to a correspondence relationship corresponding to the state of deterioration. 4. . 2. The method according to claim 1, wherein the means for calculating the correction coefficient measures the open circuit voltage of the vehicle-mounted battery a plurality of times, and obtains the open circuit voltage based on a plurality of remaining values excluding the maximum value and the minimum value. 4. The battery state detection system according to any one of claims 3 to 3 . The battery state detection system according to any one of claims 1 to 4 , wherein the correspondence is an approximate expression indicating a relation between an open circuit voltage and a state of charge. The battery state detection system according to any one of claims 1 to 4 , wherein the correspondence is a map indicating a relation between an open circuit voltage and a state of charge. A vehicle that detects the state of a vehicle-mounted battery using the battery state detection system according to any one of claims 1 to 6 .