Electric vehicle

Abstract

The present application relates to an electric vehicle including an electric power storage device, a drive device, a relay, a voltage sensor that measures a voltage of the electric power storage device, a current sensor that measures a charge / discharge current of the electric power storage device, and a control portion. The control portion acquires a first OCV at the time when the relay is turned off. The control portion acquires a second OCV if the relay is turned off after the relay is turned on at least once. The control portion calculates a current cumulative value of the electric power storage device from the time when the first OCV is acquired to the time when the second OCV is acquired, based on a measured value from the current sensor. The control portion calculates a full charge capacity of the electric power storage device based on the current cumulative value, the first OCV, and the second OCV.

Description

Technical Field

[0001] This disclosure relates to electric vehicles. Background Technology

[0002] Previously, various methods have been proposed to estimate the full-charge capacity of batteries installed in vehicles. Japanese Patent Application Publication No. 2008-261669 discloses a method for calculating the full-charge capacity of a battery based on a first open-circuit voltage (hereinafter referred to as the first OCV) before plug-in charging begins, a second open-circuit voltage (hereinafter referred to as the second OCV) after plug-in charging ends, and the difference in battery capacity between the first OCV and the second OCV, i.e., the cumulative current value.

[0003] Here, when a user begins plug-in charging immediately after driving, the full charge capacity is calculated based on a first OCV that includes the effect of voltage drop caused by polarization. As a result, the estimation accuracy of the full charge capacity calculated based on the first OCV including the effect of voltage drop caused by polarization is worse than the estimation accuracy based on the first OCV without the effect of voltage drop caused by polarization. A method for estimating the first OCV by considering polarization immediately after driving is disclosed, for example, in Japanese Patent Application Publication No. 2022-150523. However, when the standby time from immediately after driving to plug-in charging is short, the estimation accuracy of the first OCV considering polarization is poor, making it impossible to estimate the full charge capacity with high accuracy.

[0004] Here, the inventors confirm the existence of electric vehicles that do not require plugging in for charging after driving, even when parked. Furthermore, the inventors consider calculating the full charge capacity based on the OCV (On-Cost Volume) measured before and after vehicle operation. Summary of the Invention

[0005] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide an electric vehicle that can suppress the deterioration of the estimation accuracy of the full charge capacity by estimating the full charge capacity based on the OCV before and after vehicle driving.

[0006] The electric vehicle according to the first aspect of this disclosure includes: an energy storage device mounted on the electric vehicle; a drive unit that generates driving force using electricity supplied from the energy storage device; a relay disposed between the energy storage device and the drive unit; a voltage sensor for measuring the voltage of the energy storage device; a current sensor for measuring the charging and discharging current of the energy storage device; and a control unit. The control unit acquires a first OCV when the relay is open. After the relay is turned on at least once, if the relay is turned off, the control unit acquires a second OCV. The control unit calculates the cumulative current of the energy storage device from the acquisition of the first OCV to the acquisition of the second OCV based on the measurement value from the current sensor. The control unit calculates the full charge capacity of the energy storage device based on the cumulative current, the first OCV, and the second OCV.

[0007] The control unit of the electric vehicle involved in the first aspect of this disclosure can acquire a second OCV after a first period following the disconnection of the relay.

[0008] The control unit of the electric vehicle involved in the first aspect of this disclosure can acquire the first OCV again after a second period following the acquisition of the first OCV.

[0009] The control unit of the electric vehicle involved in the first aspect of this disclosure can acquire a first OCV after the electric vehicle has finished plugging in the charger.

[0010] The control unit of the electric vehicle involved in the first aspect of this disclosure can acquire the first OCV after a third period following the termination of the electric vehicle's plugging in for charging.

[0011] The current sensor in the electric vehicle according to the second aspect of this disclosure can be located externally to the energy storage device. The energy storage device may include an energy storage module. The control unit may store information about the internal current flowing within the energy storage module. The control unit may calculate the full-charge capacity of the energy storage device based on the internal current, the accumulated current value, a first OCV, and a second OCV. Attached Figure Description

[0012] Hereinafter, the features, advantages, technical and industrial importance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which the same reference numerals denote the same constituent elements, wherein:

[0013] Figure 1 This is a schematic diagram of the configuration of an electric vehicle according to an embodiment of the present disclosure.

[0014] Figure 2 This is a control flowchart of an electric vehicle according to an embodiment of the present invention.

[0015] Figure 3 This is an example of a method for estimating the full charge capacity of an electric vehicle according to an embodiment of this disclosure. Detailed Implementation

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same or equivalent parts are labeled with the same reference numerals and their descriptions are not repeated.

[0017] Schematic composition of electric vehicles

[0018] Figure 1 This is a diagram illustrating the schematic configuration of an electric vehicle according to an embodiment of the present disclosure.

[0019] For example, electric vehicle 1 is a battery electric vehicle. Electric vehicle 1 includes a drive unit 10, a system main relay (SMR) 14, an ECU 20, an energy storage device 40, a voltage sensor 51, a current sensor 52, and a temperature sensor 53. ECU 20 is configured to communicate with PCU 13, SMR 14, voltage sensor 51, current sensor 52, and temperature sensor 53, which will be described later.

[0020] The drive unit 10 is configured to generate driving force by electricity supplied from the energy storage device 40. The drive unit 10 includes an electric generator (MG) 11 as a rotary motor, drive wheels 12, and a power control unit (PCU) 13.

[0021] MG11 is, for example, an embedded permanent magnet synchronous motor (IPM motor), which functions as both a motor and a generator. The output torque of MG11 is transmitted to the drive wheel 12 via a power transmission device configured to include a reducer and a differential.

[0022] When the electric vehicle 1 brakes, MG11 is driven by the drive wheel 12, and MG11 functions as a generator. Thus, MG11 also functions as a braking device that performs regenerative braking, converting the kinetic energy of the electric vehicle 1 into electrical energy. The regenerative electricity generated by the regenerative braking force in MG11 is stored in the energy storage device 40.

[0023] PCU13 is a power conversion device that bidirectionally converts power between MG11 and the energy storage device 40. PCU13 includes, for example, an inverter and a converter that operate based on control signals from ECU20. When the energy storage device 40 discharges, the converter boosts the voltage supplied from the energy storage device 40 and supplies it to the inverter. The inverter converts the DC power supplied from the converter into AC power to drive MG11. Alternatively, PCU13 may be a structure that omits the converter.

[0024] SMR14 is disposed between the energy storage device 40 and the drive unit 10. SMR14 is electrically connected to the power line connecting the energy storage device 40 and the drive unit 10. When SMR14 is closed (on) (i.e., in a conducting state) according to a control signal from ECU20, power can be transferred between the energy storage device 40 and PCU13. On the other hand, when SMR14 is opened (off) (i.e., in a disconnected state) according to a control signal from ECU20, the electrical connection between the energy storage device 40 and PCU13 is disconnected. For example, when the ignition power of the electric vehicle 1 is turned on, SMR14 is closed (on). SMR14 functions as a protection device during the operation of the electric vehicle 1. Furthermore, SMR14 is an example of a "relay" of this disclosure.

[0025] ECU 20 includes a processor 21, a memory 22, and a storage unit 23. The processor 21 is a processing unit such as a CPU (Central Processing Unit) or an MPU (Micro-Process Unit). The memory 22 is volatile memory (working memory) such as RAM (Random Access Memory). The storage unit 23 is rewritable non-volatile memory such as flash memory. The storage unit 23 stores system programs containing an OS (Operating System) and control programs containing computer-readable code required for control operations. The processor 21 reads the system program and the control program, expands them in the memory 22, and executes them to perform various processes. ECU 20 stores voltage information obtained from the voltage sensor 51 (described later), current information obtained from the current sensor 52, and timing information together. ECU 20 can also be divided into multiple ECUs according to function. Furthermore, ECU 20 is an example of the "control unit" of this disclosure.

[0026] An energy storage device 40 is mounted on an electric vehicle 1. The energy storage device 40 has a battery pack 41. The battery pack 41 has multiple energy storage modules 42. The multiple energy storage modules 42 are connected in series. Each energy storage module 42 has multiple energy storage units 43. The multiple energy storage units 43 are connected in series. The energy storage unit 43 is a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. A secondary battery, for example, is a battery with a liquid electrolyte between its positive and negative terminals. The energy storage device 40 has an equalization circuit 44 disposed in each of the multiple energy storage units 43 and a monitoring IC 45 disposed in each of the multiple energy storage units 43. The equalization circuit 44 has a discharge resistor. The equalization circuit 44 is used, for example, to equalize the energy storage capacity of each of the multiple energy storage units 43. The monitoring IC 45 has a voltage sensor 51 and a temperature sensor 53. The monitoring IC 45 is connected in parallel with each of the multiple energy storage units 43, forming a configuration capable of measuring the voltage and temperature of each of the energy storage units 43 and outputting the measurement results to an ECU 20.

[0027] The voltage sensor 51 is configured to measure the voltage between the terminals of the battery pack 41 and output the measurement result to the ECU 20. Additionally, the voltage sensor 51 is configured to measure the voltage of each of the multiple energy storage units 43 and output the measurement result to the ECU 20.

[0028] A current sensor 52 is disposed externally on the energy storage device 40. The current sensor 52 is configured to measure the charging and discharging current of the battery pack 41 during charging and discharging, and output the measurement result to the ECU 20. For example, when the battery pack 41 is discharging, the current sensor 52 can use a positive value as the current value measured by the current sensor 52. Conversely, for example, when the battery pack 41 is charging, the current sensor 52 can use a negative value as the current value measured by the current sensor 52.

[0029] Temperature sensor 53 is configured to measure the temperature of multiple energy storage units 43 and output the measurement results to ECU 20.

[0030] Control process of electric vehicles

[0031] Next, we will refer to Figure 2 The control process for calculating the full charging capacity of electric vehicle 1.

[0032] exist Figure 2 In step S10, ECU20 checks whether SMR14 is open (disconnected). If SMR14 is disconnected ("Yes" in step S10), ECU20 proceeds to step S15. If it is not disconnected ("No" in step S10), ECU20 processes step S10 again.

[0033] In step S15, ECU 20 acquires the first OCV. More specifically, ECU 20 stores the voltage information acquired from voltage sensor 51 as the first OCV. Then, the processing of ECU 20 proceeds to step S20.

[0034] In step S20, ECU20 checks whether SMR14 is closed (on). If SMR14 is on ("Yes" in step S20), ECU20 proceeds to step S25. If SMR14 is not on ("No" in step S20), ECU20 proceeds to step S45.

[0035] In step S25, ECU20 checks whether SMR14 is disconnected. If SMR14 is disconnected ("Yes" in step S25), ECU20 proceeds to step S30. If SMR14 is not disconnected ("No" in step S25), ECU20 processes step S25 again.

[0036] In step S30, ECU20 checks whether the first period P1 has elapsed. Here, the first period P1 refers to the period from when ECU20 confirms that SMR14 is disconnected in step S25. If the first period P1 has elapsed after the processing in step S25 ("Yes" in step S30), ECU20 proceeds to step S35. If the first period P1 has not elapsed after the processing in step S25 ("No" in step S30), ECU20 processes step S30 again.

[0037] In step S35, ECU 20 acquires the second OCV. More specifically, ECU 20 stores the voltage information acquired from voltage sensor 51 as the second OCV. Then, the processing of ECU 20 proceeds to step S40.

[0038] In step S40, ECU 20 calculates the full charge capacity. More specifically, ECU 20 calculates the full charge capacity of battery pack 41 based on the first OCV, the second OCV, and the accumulated current value. Here, the accumulated current value refers to the cumulative value of the charging and discharging current of battery pack 41 from when the first OCV is obtained to when the second OCV is obtained. ECU 20 calculates the accumulated current value based on the measured value output from current sensor 52. Then, the processing of ECU 20 proceeds to step S20.

[0039] In step S45, ECU 20 checks whether the second period P2 has elapsed. Here, the second period P2 refers to the period from when ECU 20 obtains the first OCV in step S15. The second period P2 is, for example, a period between two days and one week. If the second period P2 has elapsed since obtaining the first OCV in step S45 ("Yes" in step S45), the processing of ECU 20 proceeds to step S50. If the second period P2 has not elapsed since obtaining the first OCV in step S45 ("No" in step S45), the processing of ECU 20 proceeds to step S60.

[0040] In step S50, ECU20 checks whether SMR14 is disconnected. If SMR14 is disconnected ("Yes" in step S50), ECU20 proceeds to step S55. If SMR14 is not disconnected ("No" in step S50), ECU20 processes step S50 again.

[0041] In step S55, ECU20 checks whether the first period P1 has elapsed. Here, the first period P1 refers to the period from when ECU20 confirms that SMR14 is disconnected in step S50. If the first period P1 has elapsed after the processing in step S50 ("Yes" in step S55), ECU20 proceeds to step S80. If the first period P1 has not elapsed after the processing in step S50 ("No" in step S55), ECU20 processes step S55 again.

[0042] In step S60, ECU20 confirms whether electric vehicle 1 has started plug-in charging. If electric vehicle 1 has started plug-in charging ("Yes" in step S60), ECU20 proceeds to step S65. If electric vehicle 1 has not started plug-in charging ("No" in step S60), ECU20 processes step S20 again.

[0043] In step S65, ECU20 confirms whether plug-in charging of electric vehicle 1 has ended. If plug-in charging of electric vehicle 1 has ended ("Yes" in step S65), ECU20 proceeds to step S70. If plug-in charging of electric vehicle 1 has not ended ("No" in step S65), ECU20 processes step S65 again.

[0044] In step S70, ECU 20 checks whether the third period P3 has elapsed. Here, the third period P3 is the period from when the end of plug-in charging of the electric vehicle 1 was confirmed in step S65. If the third period P3 has elapsed since the end of plug-in charging of the electric vehicle 1 was confirmed in step S65 ("Yes" in step S70), ECU 20 proceeds to step S75. If the third period P3 has not elapsed since the end of plug-in charging of the electric vehicle 1 was confirmed in step S70 ("No" in step S70), ECU 20 processes step S70 again.

[0045] In step S75, ECU20 checks whether SMR14 is disconnected. If SMR14 is disconnected ("Yes" in step S75), ECU20 proceeds to step S80. If SMR14 is not disconnected ("No" in step S75), ECU20 processes step S75 again.

[0046] In step S80, ECU 20 acquires the first OCV. More specifically, ECU 20 stores the voltage information acquired from voltage sensor 51 as the first OCV. If ECU 20 already has the first OCV stored, ECU 20 overwrites the existing first OCV information with the first OCV information acquired in step S80. Then, the processing of ECU 20 proceeds to step S20.

[0047] according to Figure 2 The control flow shown, according to an embodiment of the present disclosure, allows the ECU 20 of the electric vehicle 1 to estimate the full charge capacity of the battery pack 41. More specifically, in step S15, the ECU 20 acquires the first OCV when the SMR 14 is disconnected. Then, after at least one on-off cycle of the SMR 14, i.e., after the ECU 20 processes steps S20 and S25, it acquires the second OCV. The ECU 20 then estimates the full charge capacity of the battery pack 41 based on the first OCV, the second OCV, and the accumulated current value. This estimation method allows the full charge capacity of the battery pack 41 to be estimated based on the OCV acquired before and after vehicle operation.

[0048] In this method for estimating full charge capacity, after the SMR14 is disconnected and a first period P1 has elapsed (after step S30), the ECU20 obtains the second OCV. Thus, the ECU20 can obtain the OCV after polarization elimination caused by the discharge current due to driving. As a result, the full charge capacity can be estimated based on the OCV that eliminates the influence of polarization, thereby suppressing the deterioration of the estimation accuracy of the full charge capacity.

[0049] Here, the first period P1 is, for example, 30 minutes or 1 hour. ECU20 may also store a mapping representing the relationship between the temperature of the energy storage unit 43 and the polarization elimination time, and select the first period P1 based on the temperature information of the energy storage unit 43 measured by the temperature sensor 53.

[0050] Battery pack 41 also consumes power during standby due to self-discharge and dark current. As time elapses from the acquisition of the first OCV, the power consumption caused by self-discharge and dark current increases. This power consumption due to self-discharge and dark current is a consumption that cannot be calculated based on voltage sensor 51 and current sensor 52. As a result, the accuracy of the estimated full-charge capacity deteriorates as time elapses from the acquisition of the first OCV. Figure 2 In the control flow shown, ECU20 obtains the first OCV after a second period P2, and then obtains the first OCV again. This suppresses the deterioration in estimation accuracy caused by increased power consumption due to self-discharge and dark current each time the second period P2 passes. The second period P2 is, for example, from day 2 to day 10.

[0051] Previously, the full charge capacity was estimated based on the OCV (Optical Characteristic Value) and charging current before and after plug-in charging. However, when plug-in charging begins immediately after driving, the polarization of the OCV generated during driving is not eliminated, making it difficult to estimate the full charge capacity with high accuracy. Therefore, in Figure 2 In the control flow shown, when the electric vehicle 1 starts plug-in charging, the ECU 20 acquires the first OCV again after plug-in charging ends (step S80), and then acquires the second OCV (step S35). Thus, even when plug-in charging starts immediately after driving, the deterioration of the estimated full charge capacity can be suppressed.

[0052] Simultaneously, after the third period P3 following the completion of plug-in charging (after step S70), ECU20 obtains the first OCV. Thus, ECU20 can obtain the OCV after polarization elimination caused by the charging current during plug-in charging. As a result, the full charge capacity can be estimated based on the OCV with the polarization removed, thereby suppressing the degradation of the full charge capacity estimation accuracy.

[0053] Here, the third period P3 is, for example, 30 minutes or 1 hour. The ECU20 may also have a mapping representing the relationship between the temperature of the energy storage unit 43 and the polarization elimination time, and the third period P3 is selected based on the temperature information of the energy storage unit 43 measured by the temperature sensor 53.

[0054] The full charge capacity estimation disclosed herein is calculated based on the first OCV, the second OCV, and the accumulated current value, but the disclosure is not limited thereto. The full charge capacity estimation may also be based on, for example, the first OCV, the second OCV, the accumulated current value, and the internal current. The internal current refers to the internal current flowing within the energy storage module 42. More specifically, the internal current includes the self-discharge current of the plurality of energy storage units 43, the discharge current flowing in the discharge resistor of the equalization circuit 44 for equalization of the plurality of energy storage units 43, and the current supplied from each of the plurality of energy storage units 43 to the monitoring IC 45. The ECU 20 may also pre-store information on the internal current and calculate the power consumption based on the internal current between the first OCV and the second OCV. The ECU 20 estimates the full charge capacity based on the first OCV, the second OCV, and the total power consumption as the sum of the power consumption based on the internal current and the accumulated current value, thereby suppressing the deterioration of the full charge capacity estimation accuracy.

[0055] Information based on internal current refers to the power consumed by the battery pack 41 due to its internal current. This power consumption includes, for example, information on the power consumption based on the relationship between the SOC and self-discharge current of each of the multiple energy storage cells 43, information on the power consumption based on the relationship between the SOH and self-discharge current of each of the multiple energy storage cells 43, and information on the power consumption based on the relationship between the temperature and self-discharge current of each of the multiple energy storage cells 43. Furthermore, it also includes information on the power consumption consumed by the monitoring IC 45 in the energy storage device 40, and information on the power consumption based on the relationship between the deviation of the SOC of each of the multiple energy storage cells 43 and the discharge current flowing through the discharge resistor to equalize the SOC of each of the multiple energy storage cells 43.

[0056] Estimated full charge capacity

[0057] Figure 3 The OCV and current values ​​of the energy storage device 40 at various times are shown, as well as the on / off state of SMR14. Based on Figure 3 The example shown illustrates a specific instance of a full-charge capacity calculation performed by electric vehicle 1.

[0058] At time t1, electric vehicle 1 finishes plug-in charging. During the third period P3 from time t1, ECU 20 acquires the first OCVa. At time t2, electric vehicle 1 engages SMR 14 and begins driving. At time t3, electric vehicle 1 disengages SMR 14 and stops driving. During the first period P1 from time t3, ECU 20 acquires the second OCVa. Then, ECU 20 calculates the full charge capacity of battery pack 41 based on the first OCVa, the second OCVa, and the cumulative current value from when the first OCVa is acquired to when the second OCVa is acquired.

[0059] At time t4, electric vehicle 1 re-engages SMR14 and begins driving. At time t5, electronically controlled electric vehicle 1 deactivates SMR14 and stops driving. During the first period P1 from time t5, ECU20 acquires the second OCVb. Then, ECU20 calculates the full charge capacity of battery pack 41 based on the first OCVa, the second OCVb, and the cumulative current value from when the first OCVa was acquired to when the second OCVb was acquired.

[0060] At time t6, electric vehicle 1 re-engages SMR14 and begins driving. At time t8, electric vehicle 1 deactivates SMR14 and stops driving. During the first period P1 from time t8, ECU20 acquires the second OCVc. Then, ECU20 calculates the full charge capacity of battery pack 41 based on the first OCVa, the second OCVc, and the cumulative current value from when the first OCVa was acquired to when the second OCVc was acquired.

[0061] At time t9, immediately after calculating the full charge capacity, ECU20 confirms that the second period P2 has elapsed since the acquisition of the first OCVa. ECU20 confirms that SMR14 is disconnected and that the first period P1 has elapsed since time t8 at time t9, and stores the OCV from time t8 during the first period P1 as the first OCVb.

[0062] At time t10, electric vehicle 1 re-energizes SMR14 and begins driving. Then, as electric vehicle 1 finishes driving, ECU20 acquires the second OCV again. ECU20 calculates the full charge capacity of battery pack 41 based on the first OCVb, the acquired second OCV, and the cumulative current value from the acquisition of the first OCVb to the acquisition of the second OCV.

[0063] Whenever the electric vehicle 1 finishes driving, the ECU 20 according to the embodiment of this disclosure obtains a second OCV. This widens the difference between the first OCV and the second OCV, which forms the basis for calculating the full charge capacity, thereby suppressing the effects of polarization and other factors on the estimation accuracy. As a result, it is possible to suppress the deterioration of the estimation accuracy of the full charge capacity.

[0064] It should be considered that the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of this disclosure is not a description of the above embodiments but is indicated by the scope of protection claimed in this application, and is intended to include all modifications within the scope of the claims.

Claims

1. An electric vehicle, wherein, have: Energy storage devices, mounted on electric vehicles; The drive unit uses the electricity supplied from the energy storage device to generate driving force. A relay is disposed between the energy storage device and the drive device; A voltage sensor measures the voltage of the energy storage device; A current sensor is used to measure the charging and discharging current of the energy storage device; as well as Control Department The control unit obtains the first OCV when the relay is disconnected. After the control unit activates the relay at least once, if the relay deactivates, the control unit acquires a second OCV. The control unit calculates the cumulative current of the energy storage device from the time the first OCV is acquired to the time the second OCV is acquired, based on the measured value from the current sensor. The control unit calculates the full charge capacity of the energy storage device based on the accumulated current value, the first OCV, and the second OCV.

2. The electric vehicle according to claim 1, wherein, After a first period following the disconnection of the relay, the control unit acquires the second OCV.

3. The electric vehicle according to claim 1, wherein, If a second period has elapsed since the first OCV was acquired, the control unit acquires the first OCV again.

4. The electric vehicle according to claim 1, wherein, After the electric vehicle finishes plugging in the charging process, the control unit acquires the first OCV.

5. The electric vehicle according to claim 4, wherein, After a third period following the completion of plug-in charging of the electric vehicle, the control unit acquires the first OCV.

6. The electric vehicle according to claim 1, wherein, The current sensor is located outside the energy storage device. The energy storage device includes an energy storage module. The control unit stores information about the internal current flowing within the energy storage module. The control unit calculates the full charge capacity of the energy storage device based on the internal current, the cumulative current value, the first OCV, and the second OCV.

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