Battery abnormality diagnosis device

Abstract

The invention relates to a battery abnormality diagnosis device. A battery abnormality diagnosis device is provided with an acquisition unit for acquiring a plurality of current values and a plurality of voltage values in a predetermined period of a battery, and an abnormality diagnosis unit for diagnosing the abnormality of the battery on the basis of the variance value of the plurality of current values in the predetermined period. A calculation unit that calculates an internal resistance value of the battery on the basis of the amount of change in the charging rate of the battery, the plurality of current values, and the plurality of voltage values; and a diagnosis unit that performs an abnormality diagnosis process on the basis of the internal resistance value. The diagnosis unit performs the abnormality diagnosis process on the basis of the internal resistance value calculated when the variance value is equal to or greater than a predetermined value and the variation amount is equal to or less than a first threshold value or when the variance value is less than the predetermined value and the variation amount is equal to or less than a second threshold value.

Description

Technical Field

[0001] The invention relates to a battery abnormality diagnosis device. Background Art

[0002] There is a technology for diagnosing abnormality of a battery based on the internal resistance value of a battery that exchanges power with a motor that is a driving power source of a vehicle. The internal resistance value is calculated based on multiple current values ​​and multiple voltage values ​​of the battery within a predetermined period. Here, if the variance of the multiple current values ​​is small, there is a risk that the calculation accuracy of the internal resistance value decreases and the accuracy of abnormality diagnosis decreases. Therefore, the power consumption of auxiliary equipment of a vehicle that uses a battery as a power source is increased to ensure the variance of the multiple current values ​​(see Japanese Patent Laid-Open No. 2013-125016). Summary of the invention

[0003] If the power consumption of the auxiliary equipment increases as described above, the battery charging rate decreases, which may affect the driving of the vehicle. In addition, while the multiple current values ​​and multiple voltage values ​​used to calculate the internal resistance value are being acquired, the battery is repeatedly charged and discharged, and the battery charging rate fluctuates. If the charging rate fluctuates greatly, there is a risk that the calculation accuracy of the internal resistance value will decrease, and the accuracy of abnormality diagnosis will decrease.

[0004] Therefore, an object of the present invention is to provide a battery abnormality diagnosis device that ensures accuracy in battery abnormality diagnosis while suppressing influence on vehicle travel.

[0005] The above-mentioned purpose can be achieved by a battery abnormality diagnosis device, which includes an acquisition unit, which acquires multiple current values ​​and multiple voltage values ​​within a predetermined period of a battery that exchanges electric power with a motor serving as a driving power source of a vehicle; a calculation unit, which calculates the internal resistance value of the battery based on the variance value of the multiple current values ​​within the predetermined period, the change in the charging rate of the battery within the predetermined period, and the multiple current values ​​and the multiple voltage values ​​within the predetermined period; and a diagnosis unit, which performs abnormality diagnosis processing of the battery based on the internal resistance value, and the diagnosis unit performs the abnormality diagnosis processing based on the internal resistance value calculated when the variance value is greater than a predetermined value and the change is less than a first threshold value or when the variance value is less than the predetermined value and the change is less than a second threshold value that is less than the first threshold value.

[0006] The calculation unit may calculate the variance value, the variation amount, and the internal resistance value for each of the predetermined periods.

[0007] The calculation unit may calculate, as the variation amount, a difference between a maximum value and a minimum value of the charging rate within the predetermined period.

[0008] The calculation unit may calculate the variation amount based on an integrated value of the plurality of current values ​​within the predetermined period.

[0009] According to the present invention, it is possible to provide a battery abnormality diagnosis device that ensures the accuracy of battery abnormality diagnosis while suppressing the influence on the running of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals designate like elements, and in which:

[0011] Figure 1 It is a schematic structural diagram of the vehicle;

[0012] Figure 2 is an IV characteristic diagram showing the relationship between the current value and the voltage value of the battery;

[0013] Figure 3A is a diagram for explaining the influence of the variance value on the calculation accuracy of the internal resistance value;

[0014] Figure 3B is a diagram for explaining the influence of the variance value on the calculation accuracy of the internal resistance value;

[0015] Figure 4A This is a diagram for explaining the influence of the change in charging rate on the calculation accuracy of the internal resistance value;

[0016] Figure 4B This is a diagram for explaining the influence of the change in charging rate on the calculation accuracy of the internal resistance value;

[0017] Figure 5 is a flowchart illustrating abnormality diagnosis control; and

[0018] Figure 6 This is a diagram for explaining calculation of the variance value, the variation amount, and the internal resistance value for each predetermined period. DETAILED DESCRIPTION

[0019] [Schematic structure of vehicle]

[0020] Figure 1 1 is a schematic diagram of a vehicle 1. The vehicle 1 is a battery electric vehicle equipped with a motor 2 as a driving power source. The vehicle 1 includes the motor 2, a propeller shaft 3, a differential gear 4, a drive shaft 5, drive wheels 6, a power control unit (PCU) 7, a battery 8, and an electronic control unit (ECU) 10.

[0021] The motor 2 functions as an electric motor that outputs torque by supplying electric power. The motor 2 also functions as a generator that generates electric power when the vehicle 1 is braked. The stored electric power of the battery 8 is supplied to the motor 2 via the PCU 7. The generated electric power of the motor 2 is supplied to the battery 8 via the PCU 7. The ECU 10 adjusts the electric power exchanged between the motor 2 and the battery 8 by controlling the PCU 7.

[0022] The motor 2 is connected to the drive wheels 6 via the propeller shaft 3, the differential gear 4, and the drive shaft 5. The vehicle 1 travels by transmitting the torque of the motor 2 to the drive wheels 6.

[0023] The ECU 10 includes a central processing unit (CPU), a random access memory (RAM), a read-only memory (ROM), and a storage device, and performs various controls by executing programs stored in the ROM and the storage device. The ECU 10 is an example of a battery abnormality diagnosis device, and functionally implements an acquisition unit, a calculation unit, and a diagnosis unit described in detail later.

[0024] The ignition switch 20 , the current sensor 21 , and the voltage sensor 22 are electrically connected to the ECU 10 . The ignition switch 20 detects the on / off state of the ignition device. The current sensor 21 detects the current of the battery 8 . The voltage sensor 22 detects the voltage of the battery 8 .

[0025] [Calculation of Internal Resistance Value of Battery 8]

[0026] The ECU 10 performs abnormality diagnosis of the battery 8 based on the internal resistance value of the battery 8. The internal resistance value of the battery 8 is calculated based on a plurality of current values ​​and a plurality of voltage values ​​of the battery 8. Figure 2 1 is an IV characteristic diagram showing the relationship between the current value and the voltage value of the battery 8. The horizontal axis represents the current value, and the vertical axis represents the voltage value. The ECU 10 obtains the current value and the voltage value of the battery 8 at predetermined time intervals based on the current sensor 21 and the voltage sensor 22. Next, the ECU 10 plots the multiple current values ​​and the multiple voltage values ​​on the Figure 2 Next, the ECU 10 calculates a regression line representing the relationship between the plurality of current values ​​and the plurality of voltage values ​​by regression analysis using the least square method. The ECU 10 calculates the slope of the calculated regression line as the internal resistance value of the battery 8.

[0027] The influence of the variance of a plurality of current values ​​on the calculation accuracy of the internal resistance value will be described. Figure 3A and Figure 3B This is a diagram for explaining the influence of the variance value on the calculation accuracy of the internal resistance value. Figure 3A The variance of the current value in is greater than Figure 3B The variance of the current value in . Figure 3A In, with Figure 3BIn contrast, multiple current values ​​are widely dispersed from charge to discharge. Figure 3B When the variance value is small as shown in FIG. 1 , for example, when there is a current value that deviates greatly from other current values, the influence of this current value on the slope of the regression line is large. Therefore, there is a risk that the calculation accuracy of the internal resistance value will decrease. Figure 3A As shown in FIG. 1 , if the variance value is large, even if there is a current value that deviates greatly from other current values, the influence of the current value on the slope of the regression line is small. Therefore, the calculation accuracy of the internal resistance value can be ensured. In this way, the variance value is preferably large.

[0028] The influence of the change in the charging rate of the battery 8 on the calculation accuracy of the internal resistance value will be described. Figure 4A and Figure 4B This is a diagram to explain the effect of changes in the charging rate on the calculation accuracy of the internal resistance value. Figure 4A In the calculation, many current values ​​are biased toward the discharge side. This indicates that the charging rate has dropped significantly. If the current value is biased toward the discharge side, the influence of the current value on the slope of the regression line will be too large, and there is a risk that the calculation accuracy of the internal resistance value will drop. Figure 4B In the figure, multiple current values ​​are biased toward the charging side. This indicates that the charging rate has increased significantly. If the current value is biased toward the charging side, the influence of the current value on the slope of the regression line is too small, and there is a risk that the calculation accuracy of the internal resistance value will decrease. Therefore, multiple current values ​​are preferably not biased toward the charging side or the discharging side. In other words, the variation of the charging rate is preferably small. In this embodiment, in order to ensure the calculation accuracy of the internal resistance value and ensure the accuracy of the abnormal diagnosis, ECU10 performs abnormal diagnosis control by considering the variance value of the current value and the variation of the charging rate as described below.

[0029] [Abnormal diagnosis control]

[0030] Figure 5 1 is a flowchart illustrating an abnormality diagnosis control. This control is repeatedly executed while the ignition device is turned on. ECU 10 acquires multiple current values ​​and multiple voltage values ​​of battery 8 within a predetermined period as described above (S1). In detail, ECU 10 acquires the current value and the voltage value at every predetermined sampling interval, and acquires a total of n current values ​​and n voltage values ​​within a predetermined period. S1 is an example of the processing performed by the acquisition unit.

[0031] Next, the ECU 10 calculates a variance value of the n current values ​​acquired within a predetermined period ( S2 ). Specifically, the ECU 10 calculates the variance value based on the following equation (1).

[0032]

[0033] σ 2is the variance value. n is the total number of current values ​​obtained within the above predetermined period. A k is the kth current value acquired in a predetermined period. μ is the average value of n current values ​​acquired in a predetermined period. S2 is an example of a process executed by the calculation unit.

[0034] Next, the ECU 10 calculates the change in the charging rate of the battery 8 within a predetermined period (S3). The change in the charging rate is the difference between the maximum value and the minimum value of the charging rate within the predetermined period. The change in the charging rate within the predetermined period is calculated as follows. Based on the current value obtained at each predetermined sampling interval, the small change in the charging rate for each sampling interval is calculated. The small change is calculated by integrating the current value over time. Next, the small changes within the predetermined period are accumulated sequentially. The current value used in the calculation of the small change is a positive value during charging and a negative value during discharging.

[0035] For example, assuming that the capacity of the battery 8 is 1 [Ah], the cumulative value of the current value when the battery 8 is charged for 1 second at a current value of 36 [A] is +0.01 [Ah]. The small change in this case is +1 [%]. The cumulative value of the current value when the battery 8 is discharged for 1 second at a current value of 36 [A] is -0.01 [Ah]. The small change in this case is -10 [%]. By accumulating the small changes calculated sequentially within the predetermined period, the change in the charging rate relative to the charging rate at the start of the predetermined period can be calculated at any time.

[0036] Based on the variation of the charging rate calculated in this way, the maximum value and the minimum value of the charging rate in the predetermined period are determined. Next, the variation is calculated by subtracting the minimum value from the maximum value. S3 is an example of the processing executed by the calculation unit.

[0037] Next, the ECU 10 calculates the internal resistance value of the battery 8 based on the n current values ​​and the n voltage values ​​as described above ( S4 ). S4 is an example of a process executed by the calculation unit.

[0038] Next, ECU10 determines whether the variance value is greater than or equal to a predetermined value D (S5). When the answer is "yes" in S5, ECU10 determines whether the variation is less than or equal to the first threshold value E1 (S6). When the answer is "no" in S6, this control ends. When the answer is "yes" in S6, ECU10 performs abnormality diagnosis processing of battery 8 based on the calculated internal resistance value (S8). In addition, in the abnormality diagnosis processing, when the internal resistance value is within the normal range, battery 8 is diagnosed as normal, and when the internal resistance value is outside the normal range, battery 8 is diagnosed as abnormal.

[0039] When the answer is "No" in S5, ECU10 determines whether the change amount is less than the second threshold value E2 (S7). The second threshold value E2 is a value less than the first threshold value E1. When the answer is "No" in S7, this control ends. When the answer is "Yes" in S7, ECU10 performs abnormality diagnosis processing of battery 8 based on the calculated internal resistance value (S8). S8 is an example of processing performed by the diagnosis unit.

[0040] In the case where the variance value is lower than the predetermined value D, the abnormality diagnosis process is performed under the condition that the variation is less than the second threshold value E2 which is smaller than the first threshold value E1. The decrease in the calculation accuracy of the internal resistance value due to the low variance value can be suppressed by setting the variation to less than the second threshold value E2. Thus, the accuracy of abnormality diagnosis can be ensured. In addition, in order to ensure the variance value, the power consumption of the auxiliary equipment does not need to be increased. Therefore, the decrease in the charging rate of the battery 8 can be suppressed, and the influence on the driving of the vehicle 1, such as the decrease in the driving distance, can be suppressed.

[0041] Figure 6 It is an explanatory diagram of the calculation of the variance value, the variation and the internal resistance value for each predetermined period. For example, the period from time t1 to t2, the period from time t2 to t3 and the period from time t3 to t4 are each equivalent to the predetermined period T mentioned above. When the variance value during the period from time t1 to t2 is greater than the predetermined value D and the variation is less than the first threshold value E1, it is considered that the calculation accuracy of the internal resistance value during this period is good, and the abnormal diagnosis process is performed based on the internal resistance value. When the variance value during the period from time t2 to t3 is less than the predetermined value D and the variation is greater than the second threshold value E2, it is considered that the calculation accuracy of the internal resistance value during this period is poor, and the abnormal diagnosis process based on the internal resistance value is not performed. When the variance value during the period from time t3 to t4 is less than the predetermined value D and the variation is less than the second threshold value E2, it is considered that the calculation accuracy of the internal resistance value during this period is good, and the abnormal diagnosis process is performed based on the internal resistance value.

[0042] In this way, the variance value, the variation, and the internal resistance value are calculated for each predetermined period. In addition, the internal resistance value calculated based on the multiple current values ​​and multiple voltage values ​​acquired when the variance value and the variation satisfy the above conditions is used for abnormality diagnosis processing. For example, compared with the case where only the variance value and the variation are calculated and the internal resistance value is calculated only when the variance value and the variation satisfy the above conditions, the complication of control is avoided.

[0043] In the above embodiment, the vehicle 1 is described as an electric vehicle, but the present invention is not limited thereto. For example, the vehicle may be a hybrid electric vehicle having an engine and a motor as a driving power source. In the case of a hybrid electric vehicle, it is also possible to suppress a decrease in the charging rate of the battery due to an increase in the power consumption of auxiliary equipment, and to suppress the influence on the driving of the vehicle, such as the deterioration of fuel efficiency.

[0044] As mentioned above, although the embodiment of the present invention is described in detail, the present invention is not limited to the above-mentioned specific embodiment, and various deformation|transformation and changes are possible within the scope of the gist of the present invention described in the claims.

Claims

1. A battery abnormality diagnosis device, comprising: an acquisition unit that acquires a plurality of current values ​​and a plurality of voltage values ​​within a predetermined period of a battery that exchanges electric power with a motor that is a driving power source of the vehicle; a calculation unit that calculates an internal resistance value of the battery based on a variance value of the plurality of current values ​​within the predetermined period, a variation amount of a charging rate of the battery within the predetermined period, and the plurality of current values ​​and the plurality of voltage values ​​within the predetermined period; as well as a diagnosis unit that performs abnormality diagnosis processing of the battery based on the internal resistance value, The diagnosis unit performs the abnormality diagnosis process based on the internal resistance value calculated when the variance value is greater than or equal to a predetermined value and the variation is less than or equal to a first threshold value, or when the variance value is less than the predetermined value and the variation is less than or equal to a second threshold value that is smaller than the first threshold value.

2. The battery abnormality diagnosis device according to claim 1, wherein: The calculation unit calculates the variance value, the variation amount, and the internal resistance value for each of the predetermined periods.

3. The battery abnormality diagnosis device according to claim 1 or 2, wherein: The calculation unit calculates a difference between a maximum value and a minimum value of the charging rate within the predetermined period as the variation amount.

4. The battery abnormality diagnosis device according to claim 1 or 2, wherein: The calculation unit calculates the amount of change based on an integrated value of the plurality of current values ​​within the predetermined period.

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