JP2019137103A - Electric vehicle - Google Patents

Abstract

To achieve, without imparting discomfort to a user as much as possible, high-rate deterioration restriction control in which high-rate deterioration of a secondary battery is restricted in an electric vehicle in which a secondary battery is mounted.SOLUTION: An ECU 26 executes high-rate deterioration restriction control in which, in a case where it is evaluated by a high-rate deterioration evaluation value ΣD that a battery 16 is deteriorating, a target for an SOC is increased to thereby increase the SOC. In a case where determination of extraction of power from the battery 16 during execution of the high-rate deterioration restriction control is established, the ECU 26 can increase the target for the SOC. The power extraction determination is established when the battery 16 is outputting power or when accelerator opening or vehicle drive force is larger than a predetermined amount. When the SOC is equal to higher than the target by a predetermined value, the ECU 26 selects an EV mode.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an electric vehicle, and more particularly, to a control technique for suppressing high-rate deterioration that occurs in a secondary battery mounted on the electric vehicle.

  When the concentration of the salt concentration in the electrolyte solution of the secondary battery is increased due to charging / discharging of the secondary battery, the internal resistance of the secondary battery increases. The increase in internal resistance due to the uneven salt concentration is referred to as “high-rate degradation” or the like, as distinguished from the aging degradation of the material constituting the secondary battery.

  High-rate degradation has characteristics that are promoted when the secondary battery is used in a region where the SOC (State Of Charge) of the secondary battery is low. This is presumably because in the region where the SOC is low, the expansion and contraction of the negative electrode of the battery is increased, and the electrolyte in the battery cell is easily pushed out, so that a difference in salt concentration in the battery cell surface is likely to occur.

  Japanese Patent Laying-Open No. 2006-182022 (Patent Document 1) discloses a technique capable of suppressing high-rate deterioration. In the electric vehicle described in this publication, an evaluation value ΣD indicating the degree of high-rate deterioration is calculated. When the evaluation value ΣD exceeds a threshold value, the SOC is raised by raising the SOC control target. According to this electric vehicle, when the evaluation value ΣD exceeds the threshold value, use of the secondary battery in the low SOC region is avoided, so that high-rate deterioration can be suppressed (see Patent Document 1).

JP, 2006-182022, A

  When the SOC of the secondary battery is higher than the control target (SOC target), basically, motor driving using the electric power stored in the secondary battery (hereinafter referred to as “EV driving”) until the SOC decreases to the control target. Is performed). When the SOC decreases to the control target, a hybrid traveling (hereinafter also referred to as “HV traveling”) is performed in which the power generation mechanism using an engine or the like is appropriately operated to control the SOC to the control target.

  The technique described in the above publication is useful in that high rate deterioration can be suppressed by raising the SOC target. However, for example, even if the secondary battery is sufficiently charged by continuous regenerative power generation associated with traveling on a long downhill road or a power source outside the vehicle, the EV target increases and the subsequent EV is increased. There is a possibility that the user may feel uncomfortable in the travel distance, the SOC display, and the like.

  The present disclosure has been made in order to solve such a problem, and an object of the present disclosure is to perform high rate deterioration suppression control for suppressing high rate deterioration of the secondary battery in an electric vehicle equipped with the secondary battery as much as possible. It is to realize without giving a sense of incongruity.

  An electric vehicle according to the present disclosure includes a vehicle driving device configured to receive electric power to generate a vehicle driving force and generate power, a secondary battery that exchanges electric power with the vehicle driving device, and a control device. . The control device is configured to switch between an EV mode that consumes the SOC of the secondary battery and a mode that controls the SOC to a predetermined target. The control device is further evaluated that the secondary battery is deteriorated by an evaluation value (ΣD) indicating the degree of deterioration (high-rate deterioration) of the secondary battery due to the uneven salt concentration in the secondary battery. In this case, the deterioration suppression control (high-rate deterioration suppression control) for increasing the SOC by increasing the SOC target is configured to be executed. Here, the control device can increase the SOC target when the carry-out determination of the power from the secondary battery is established during the execution of the deterioration suppression control. The power carry-out determination is established when the secondary battery is outputting power, or when the accelerator opening or the vehicle driving force is larger than a predetermined amount. Then, the control device selects the EV mode when the SOC is higher than the target by a predetermined value or more.

  In this electric vehicle, the SOC target can be raised when the determination of carrying out power from the secondary battery is established during the execution of the deterioration suppression control. The power carry-out determination is established when the secondary battery is outputting power, or when the accelerator opening or the vehicle driving force is larger than a predetermined amount. If the power take-out determination is not established, the SOC target is not raised. As a result, the EV travel distance is shortened because the SOC target has increased despite the situation where the secondary battery is sufficiently charged (for example, when traveling on a long downhill road or when charging with a power supply outside the vehicle). It is possible to prevent the user from feeling uncomfortable as much as possible. Further, for example, when the deviation between the SOC and the SOC target is displayed to the user, the SOC target has risen despite the above situation in which the secondary battery is sufficiently charged. It is possible to prevent the user from feeling uncomfortable that the SOC does not increase.

  In this electric vehicle, the EV mode is selected when the SOC is higher than the target by a predetermined value or more. Thereby, even if the SOC target is increased by the high-rate deterioration suppression control, it is possible to suppress the EV travel distance from decreasing as much as possible.

  According to the electric vehicle in the present disclosure, it is possible to realize the high-rate deterioration suppression control that suppresses the high-rate deterioration of the secondary battery as much as possible without making the user feel uncomfortable. Moreover, even if the SOC target is increased by the high-rate deterioration suppression control, it is possible to suppress the EV travel distance from decreasing as much as possible.

It is a block diagram explaining the whole hybrid vehicle composition shown as an example of an electric vehicle according to Embodiment 1 of the present disclosure. It is the figure which showed an example of the SOC display screen displayed on the display part shown in FIG. It is the figure which showed an example of transition of SOC of a battery. It is the figure which showed the relationship between SOC and charge request | requirement power. It is the figure which showed an example of the relationship between the evaluation value of high rate degradation, and a SOC target. It is a functional block diagram of ECU shown in FIG. It is the flowchart which showed an example of the process sequence of the high rate deterioration suppression control performed by ECU. FIG. 6 is a diagram showing an example of SOC and its target transition when high-rate deterioration suppression control is executed in the first embodiment. 6 is a flowchart illustrating an example of a processing procedure of high rate deterioration suppression control executed by an ECU according to a second embodiment. It is the figure which showed an example of transition of SOC when the high-rate deterioration suppression control is performed in Embodiment 2, and its target.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Hereinafter, a plurality of embodiments will be described. However, it is planned from the beginning of the application to appropriately combine the configurations described in the embodiments. In the drawings, the same or corresponding portions are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a block diagram illustrating an overall configuration of a hybrid vehicle shown as an example of an electric vehicle according to the first embodiment of the present disclosure. Referring to FIG. 1, hybrid vehicle 100 includes a vehicle drive device 22, a transmission gear 8, a drive shaft 12, wheels 14, a battery 16, and an ECU (Electronic Control Unit) 26. Hybrid vehicle 100 further includes a charger 28, a connection unit 30, and a display unit 32.

  The vehicle drive device 22 is configured to generate a vehicle drive force and to generate electric power. Specifically, vehicle drive device 22 includes an engine 2, a power split device 4, motor generators 6, 10, and power converters 18, 20.

  The engine 2 is an internal combustion engine that outputs power by converting thermal energy from combustion of fuel into kinetic energy of a moving element such as a piston or a rotor. As the fuel for the engine 2, hydrocarbon fuels such as gasoline, light oil, ethanol, liquid hydrogen, and natural gas, or liquid or gaseous hydrogen fuel are suitable.

  Motor generators 6 and 10 are AC rotating electric machines, for example, three-phase AC synchronous motors in which permanent magnets are embedded in a rotor. The motor generator 6 is used as a generator driven by the engine 2 via the power split device 4 and also as an electric motor for starting the engine 2. The motor generator 10 mainly operates as an electric motor and drives the drive shaft 12. On the other hand, when the vehicle is braking or traveling downhill, the motor generator 10 operates as a generator to perform regenerative power generation.

  The power split device 4 includes, for example, a planetary gear mechanism having three rotation shafts of a sun gear, a carrier, and a ring gear. Power split device 4 divides the driving force of engine 2 into power transmitted to the rotation shaft of motor generator 6 and power transmitted to transmission gear 8. The transmission gear 8 is connected to a drive shaft 12 for driving the wheels 14. Transmission gear 8 is also coupled to the rotating shaft of motor generator 10.

  The battery 16 is a rechargeable secondary battery, for example, a secondary battery such as a nickel metal hydride battery or a lithium ion battery. The battery 16 supplies power to the power converters 18 and 20. The battery 16 is charged by receiving the generated power when the motor generator 6 and / or 10 generates power. Further, the battery 16 can be charged by receiving electric power supplied from a power source (not shown) outside the vehicle through the connection unit 30. The current sensor 24 detects the current I input to and output from the battery 16 (detects the output (discharge) from the battery 16 as a positive value and the input (charge) to the battery 16 as a negative value), and the detected value. Is output to the ECU 26.

  Note that the remaining capacity of the battery 16 is indicated by, for example, an SOC in which the current charged amount with respect to the fully charged state of the battery 16 is expressed as a percentage. The SOC is calculated based on, for example, detection values of the current sensor 24 and / or a voltage sensor (not shown). The SOC may be calculated by the ECU 26 or may be calculated by an ECU provided separately in the battery 16.

  The power converter 18 performs bidirectional DC / AC power conversion between the motor generator 6 and the battery 16 based on a control signal received from the ECU 26. Similarly, power converter 20 performs bidirectional DC / AC power conversion between motor generator 10 and battery 16 based on a control signal received from ECU 26. Thereby, motor generators 6 and 10 can output a positive torque for operating as an electric motor or a negative torque for operating as a generator, with the transfer of electric power to and from battery 16. Power converters 18 and 20 are constituted by inverters, for example. A step-up converter for DC voltage conversion may be disposed between the battery 16 and the power converters 18 and 20.

  The charger 28 converts electric power from a power source external to the vehicle electrically connected to the connection unit 30 into a voltage level of the battery 16 and outputs the voltage to the battery 16 (hereinafter, the power source outside the vehicle is also referred to as “external power source”) The charging of the battery 16 by an external power source is also referred to as “external charging”). The charger 28 includes, for example, a rectifier and an inverter. Note that the method of receiving power from the external power source is not limited to contact power reception using the connection unit 30, and may receive power from the external power source in a contactless manner using a power receiving coil or the like instead of the connection unit 30.

  The display unit 32 is a display for providing various information to the user of the vehicle. The display unit 32 may be capable of accepting user operations, and may be a display including a touch panel, for example. Typical information displayed on the display unit 32 includes the SOC of the battery 16.

  FIG. 2 is a diagram illustrating an example of the SOC display screen displayed on the display unit 32. Referring to FIG. 2, this SOC display screen 34 includes an SOC display unit 36 and a target instruction unit 38. The SOC display unit 36 displays the SOC deviation (ΔSOC) with respect to the SOC control target instructed by the target instruction unit 38. Although the SOC target indicated by the target instruction unit 38 can change as will be described later, the position of the target instruction unit 38 on the SOC display screen 34 remains unchanged.

  As illustrated in the figure, that the display level of the SOC display unit 36 is higher than the level of the target instruction unit 38 indicates that the SOC exceeds the control target. On the other hand, the display level of the SOC display unit 36 being lower than the level of the target instruction unit 38 indicates that the SOC is below the control target.

  Referring to FIG. 1 again, ECU 26 includes a CPU (Central Processing Unit), a storage device, an input / output buffer, and the like (all not shown), and controls each device in hybrid vehicle 100. Note that these controls are not limited to processing by software, and can be processed by dedicated hardware (electronic circuit).

  As the main control of the ECU 26, the ECU 26 calculates a vehicle driving torque (required value) based on the vehicle speed and the accelerator opening corresponding to the operation amount of the accelerator pedal, and the vehicle driving power based on the calculated vehicle driving torque. (Required value) is calculated. Further, the ECU 26 further calculates the required charging power of the battery 16 based on the SOC of the battery 16 and generates a power (hereinafter referred to as “vehicle power”) obtained by adding the required charging power to the vehicle driving power. The drive device 22 is controlled.

  When the vehicle power is low, the ECU 26 controls the vehicle drive device 22 so that the engine 2 is stopped and the motor generator 10 travels only (EV travel). Thereby, the battery 16 is discharged, and the SOC of the battery 16 is reduced. When the vehicle power increases, the ECU 26 controls the vehicle drive device 22 so that the engine 2 operates to travel (HV traveling). At this time, the battery 16 is charged if the output of the engine 2 is greater than the vehicle power, and the battery 16 is discharged if the vehicle power is greater than the engine output.

  Then, the ECU 26 switches the SOC of the battery 16 by appropriately switching between the mode (EV mode) in which the SOC of the battery 16 is actively consumed by actively performing the EV travel while allowing the HV travel, and the SOC travel. The vehicle is controlled by selectively applying a mode for maintaining the vehicle. The latter mode includes a mode that maintains the SOC at the lower limit when the SOC drops to a predetermined lower limit (HV mode) and a mode that maintains the SOC higher than the lower limit according to the user's request (HVS mode). Each mode will be described in detail later.

  Further, the ECU 26 controls the charger 28 so that the electric power supplied from the external power source electrically connected to the connection unit 30 is converted into the voltage level of the battery 16 and output to the battery 16 during execution of the external charging. To do.

  Further, the ECU 26 calculates an evaluation value (ΣD) indicating the degree of deterioration (high-rate deterioration) of the battery 16 due to the continuous bias of the salt concentration of the battery 16 due to charging / discharging of the battery 16. The calculation method of the evaluation value (ΣD) will be described in detail later. This evaluation value indicates a negative value when the battery 16 is overcharged and the salt concentration is biased. When the battery 16 is used in an excessively discharged manner, a positive value is shown when the salt concentration is biased.

  As described above, high-rate degradation has characteristics that are promoted when a battery is used in a region where the SOC is low. Therefore, when it is evaluated that the high-rate deterioration is progressing based on the evaluation value (ΣD), it is conceivable to increase the SOC by increasing the SOC control target (hereinafter, such SOC control is referred to as “high-rate deterioration”). Referred to as “inhibition control”).

  However, for example, although the continuous regenerative power generation and external charging associated with traveling on a long downhill road are performed, the control target of the SOC is increased, so that the subsequent EV traveling distance and display unit There is a possibility that the user feels uncomfortable in the 32 SOC display or the like.

  Therefore, in the first embodiment, the ECU 26 can raise the SOC target when power is output from the battery 16 (during discharging) with respect to raising the SOC target by the high-rate deterioration suppression control. That is, when power is input to the battery 16 (during charging), the SOC target is not increased. As a result, the user feels as uncomfortable as possible that the EV travel distance is shortened because the SOC target has increased, regardless of the situation in which power is input to the battery 16 (for example, when traveling on a long downhill road or during external charging). You can avoid giving. Further, when the deviation between the SOC and the SOC target (ΔSOC) is displayed on the display unit 32, the SOC target has risen despite the above situation in which the battery 16 is sufficiently charged. An uncomfortable feeling that the SOC does not increase (because the SOC target increases) can be prevented from being given to the user as much as possible.

  Then, the ECU 26 selects the EV mode when the SOC is higher than the target by a predetermined value or more. Thereby, even if the SOC target is increased by the high-rate deterioration suppression control, it is possible to suppress the EV travel distance from decreasing as much as possible.

  FIG. 3 is a diagram showing an example of the transition of the SOC of the battery 16. Referring to FIG. 3, it is assumed that after battery 16 is fully charged (SOC = MAX) by external charging, traveling is started in EV mode at time t0.

  The EV mode is a mode in which the SOC of the battery 16 is actively consumed. Basically, the electric power stored in the battery 16 (mainly electric energy by external charging) is consumed. When traveling in the EV mode, the engine 2 does not operate in order to maintain the SOC. Specifically, for example, during the EV mode, the required charging power of the battery 16 is set to zero. As a result, the SOC may temporarily increase due to the regenerative power collected when the vehicle decelerates or the power generated by the operation of the engine 2, but as a result, the rate of discharge rather than charging As a whole, the SOC decreases as the travel distance increases.

  Even in the EV mode, the engine 2 operates if the vehicle power (vehicle drive power) exceeds the engine start threshold value. Even if the vehicle power does not exceed the engine start threshold value, the operation of the engine 2 may be permitted, such as when the engine 2 or the exhaust catalyst is warmed up. That is, EV travel and HV travel are possible even in the EV mode. Such an EV mode may be referred to as a “CD (Charge Depleting) mode”.

  When the SOC decreases to the lower limit SL at time t3, the control mode is switched from the EV mode to the HV mode (the HVS mode from time t1 to t2 will be described later). The HV mode is a mode for controlling (maintaining) the SOC at the lower limit SL. Specifically, when the SOC is lower than the lower limit SL, the engine 2 is operated (HV traveling), and when the SOC is increased, the engine 2 is stopped (EV traveling). Thus, in the HV mode, the engine 2 operates to maintain the SOC.

  Even in the HV mode, the engine 2 stops when the SOC increases. That is, the HV mode is not limited to the HV traveling that always operates with the engine 2 operated, and EV traveling and HV traveling are possible even in the HV mode.

  The HVS mode is a mode that maintains the SOC higher than the lower limit SL according to the user's request. In this example, there is a user request at time t1, and the SOC is controlled (maintained) to the value SC1 at the time of the user request (SC1> SL) until time t2 when the request is canceled. Note that the transition request to the HVS mode and the cancellation are input by the user from the display unit 32 that can be operated by the user, for example.

  In the HVS mode, the engine 2 operates when the SOC decreases below the value SC1 (HV traveling), and the engine 2 stops when the SOC increases (EV traveling). Thus, the engine 2 operates in order to maintain the SOC even in the HVS mode. The HV mode and the HVS mode in which the SOC is maintained may be collectively referred to as “CS (Charge Sustain) mode”.

  In the HVS mode, as in the HV mode, the engine 2 stops when the SOC increases. In other words, the HVS mode is not limited to the HV traveling in which the engine 2 is always operated, and EV traveling and HV traveling are possible even in the HVS mode.

  The engine start threshold value in the EV mode is preferably larger than the engine start threshold values in the HV mode and the HVS mode. That is, it is preferable that the region where hybrid vehicle 100 travels EV in the EV mode is larger than the region where hybrid vehicle 100 travels EV in HV mode and HVS mode. As a result, in the EV mode, the frequency at which the engine 2 is started is further suppressed, and opportunities for EV traveling can be further expanded.

  In the HV mode and the HVS mode in which the SOC is maintained, the required charging power of the battery 16 is calculated based on the SOC of the battery 16. For example, as shown in FIG. 4, the charge / discharge required power of the battery 16 is determined based on the deviation between the SOC (calculated value) and the control target SC (the lower limit SL in the HV mode and the value SC1 in the HVS mode). Is done. Then, the vehicle drive device 22 is controlled so as to generate a power (vehicle power) obtained by adding the charging request power to the vehicle drive power. Thus, in the HV mode, the SOC is controlled near the lower limit SL, and in the HVS mode, the SOC is controlled near the value SC1.

  At time t4, when the HV mode is selected, if it is evaluated that the high rate deterioration is progressing according to the evaluation value (ΣD) of the high rate deterioration, the high rate deterioration suppression control is executed, and the SOC control target is The lower limit SL is increased to a predetermined value SC2 (SC2> SL). As an example, the lower limit SL is set to about SOC 20%, while the predetermined value SC2 is set to about SOC 50%.

  FIG. 5 is a diagram showing an example of the relationship between the evaluation value (ΣD) of the high rate deterioration and the SOC target. Referring to FIG. 5, the high rate deterioration is promoted when the battery is used in the region where the SOC is low as described above, and in particular, has a characteristic that is promoted when a current in the charging direction flows in the low SOC region.

  Therefore, when the evaluation value (ΣD) increases as a negative value and the evaluation value (ΣD) reaches the threshold value SDth (negative value) at time t11, the SOC control target (target SC in FIG. 4) increases by a predetermined amount. With the rate it is increased to the value SC2. Thereby, the increase tendency (increase in the negative direction) of the evaluation value (ΣD) is suppressed. Although not specifically shown, the SOC target may be increased stepwise in accordance with an increase in evaluation value (ΣD) (increase in the negative direction).

  Referring to FIG. 3 again, while high-rate deterioration suppression control is being executed, external charging is started at time t5, and the SOC increases. Then, at time t6, external charging ends, and in this example, the battery 16 is charged to a fully charged state (SOC = MAX). When the battery 16 is charged to the fully charged state, the SOC is higher than the target (SC2) by a predetermined amount ΔSth or more, and the EV mode is selected after the external charging is finished.

  FIG. 6 is a functional block diagram of ECU 26 shown in FIG. Referring to FIG. 6, ECU 26 includes SOC calculation unit 52, damage amount calculation unit 54, evaluation value calculation unit 56, storage unit 58, determination unit 60, SOC control unit 62, and mode control unit 64. And a travel control unit 66 and an external charge control unit 68.

  The SOC calculation unit 52 calculates the SOC of the battery 16 based on the current I and / or voltage of the battery 16 detected by the current sensor 24 (FIG. 1) and / or a voltage sensor (not shown). As for a specific calculation method of the SOC, a method using the integrated value of the current I, a method using an OCV-SOC curve indicating the relationship between the open circuit voltage (OCV) of the battery 16 and the SOC, etc. Various known techniques can be used.

  The damage amount calculation unit 54 calculates the damage amount D of the battery 16 due to the uneven salt concentration in the battery 16 based on the current I input to and output from the battery 16 and the energization time thereof. The damage amount D is calculated with a predetermined period Δt based on the following equation (1), for example.

D (N) = D (N−1) −α × Δt × D (N−1) + (β / C) × I × Δt (1)
Here, D (N) indicates the current calculated value of the damage amount D, and D (N−1) indicates the previous calculated value of the damage amount D calculated before the period Δt. D (N−1) is stored in the storage unit 58 at the time of the previous calculation, and is read from the storage unit 58 at the time of the current calculation.

  Α × Δt × D (N−1) in the second term on the right side in Expression (1) is a decrease term of the damage amount D, and indicates a component when the bias in salt concentration is alleviated. α is a forgetting factor, which corresponds to the diffusion rate of ions in the electrolyte solution of the battery 16. The higher the diffusion rate, the greater the forgetting factor α. The value of α × Δt is set to be a value from 0 to 1. The decrease term of the damage amount D becomes larger as the forgetting factor α is larger (that is, as the ion diffusion rate is higher) and as the period Δt is longer.

  The forgetting factor α depends on the SOC and temperature of the battery 16. A correspondence relationship between the forgetting factor α and the SOC and temperature of the battery 16 is obtained in advance by experiments or the like and stored in the storage unit 58, and the forgetting factor α is set based on the SOC and temperature of the battery 16 at the time of calculation. . For example, if the temperature of the battery 16 is the same, the forgetting factor α can be set to a larger value as the SOC is higher. If the SOC is the same, the forgetting factor α can be set to a larger value as the temperature of the battery 16 is higher.

  (Β / C) × I × Δt in the third term on the right side in Equation (1) is an increasing term of the amount of damage D, and indicates a component when a salt concentration bias occurs. β is a current coefficient, and C represents a limit threshold value. The increase term of the damage amount D becomes larger as the current I is larger and as the period Δt is longer.

  The current coefficient β and the limit threshold C depend on the SOC and temperature of the battery 16. A correspondence relationship between each of the current coefficient β and the limit threshold C and the SOC and temperature of the battery 16 is obtained in advance by experiments or the like and stored in the storage unit 58, and is based on the SOC and temperature of the battery 16 at the time of calculation. Current coefficient β and limit threshold C are set. For example, the limit threshold C is set to a larger value as the SOC is higher if the temperature of the battery 16 is the same, and is set to a larger value as the temperature of the battery 16 is higher if the SOC is the same.

  Thus, by calculating the current damage amount D by expressing the occurrence and relaxation of the salt concentration bias by the increase term and the decrease term, respectively, the change (increase / decrease) in the salt concentration bias considered to be the cause of the high rate deterioration. ).

  The evaluation value calculation unit 56 calculates an evaluation value ΣD indicating the degree of high rate deterioration of the battery 16. The progress state of the high rate deterioration is evaluated using the integrated value of the damage amount D calculated by the damage amount calculation unit 54. The evaluation value ΣD is calculated based on the following formula (2), for example.

ΣD (N) = γ × ΣD (N−1) + η × D (N) (2)
Here, ΣD (N) indicates the current calculated value of the evaluation value, and ΣD (N−1) indicates the previous calculated value of the evaluation value calculated before the period Δt. γ is an attenuation coefficient, and η is a correction coefficient. ΣD (N−1) is stored in the storage unit 58 during the previous calculation, and is read from the storage unit 58 during the current calculation. γ and η are also stored in advance in the storage unit 58, and read from the storage unit 58 during the current calculation.

  The attenuation coefficient γ is set to a value smaller than 1. Since the unevenness of the salt concentration is alleviated by the diffusion of ions over time, the previous evaluation value ΣD (N−1) is reduced when calculating the current evaluation value ΣD (N). Is to be considered. The correction coefficient η is set as appropriate.

  The evaluation value ΣD calculated in this way increases in the negative direction (negative value) when the battery 16 is used in an excessively charged state due to an increase in the bias of the salt concentration corresponding to the excessively charged state. When the battery 16 is used in an excessive discharge manner, the evaluation value ΣD increases in the positive direction (positive value) due to an increase in the salt concentration bias corresponding to the excessive discharge.

  The determination unit 60 determines whether or not the evaluation value ΣD calculated by the evaluation value calculation unit 56 has reached the threshold value SDth (FIG. 5). As described above, high rate degradation has a characteristic that is promoted when a current in the charging direction flows particularly in a low SOC region. Specifically, the determination unit 60 determines that the evaluation value ΣD increases in the negative direction. It is determined whether or not the threshold value SDth (negative value) is below.

  The mode control unit 64 controls switching between the EV mode, the HV mode, and the HVS mode. Specifically, when the SOC becomes higher than the SOC target by a predetermined value or more, mode control unit 64 selects the EV mode. When the SOC decreases to the lower limit SL by traveling in the EV mode, the mode control unit 64 switches from the EV mode to the HV mode. Further, the mode control unit 64 selects the HVS mode according to a user request. If the above request is made during the EV mode, the SOC is maintained at the current value. When the above request is made during the HV mode, for example, the SOC may be maintained at a value higher than the lower limit SL by a predetermined amount, or switching to the HVS mode may be disabled.

  The SOC control unit 62 receives the determination result in the determination unit 60 from the determination unit 60. Then, when the determination unit 60 determines that the evaluation value ΣD has reached the threshold value SDth, the SOC control unit 62 sets the SOC control target from the lower limit SL, which is the target in the HV mode, to the value SC2. Control to increase to (SC2> SL) is executed (high-rate deterioration suppression control).

  Here, the SOC control unit 62 makes it possible to increase the SOC target when the battery 16 is outputting power when executing the high rate deterioration suppression control. When the battery 16 is outputting power, the SOC target may be always increased (up to the value SC2), or the SOC target may be increased only when the SOC is equal to or higher than the SOC target ( (If the SOC is lower than the SOC target, the SOC target is not increased.) Note that when the SOC target is increased stepwise, the SOC display on the display unit 32 changes suddenly, so the SOC control unit 62 increases the SOC target with a predetermined rate limit.

  Further, the SOC control unit 62 outputs an instruction to the mode control unit 64 to select the EV mode when the SOC is higher than the SOC target by a predetermined value or more. The predetermined value is set to an arbitrary value that can secure a desired EV travel distance after selection of the EV mode. Note that the SOC control unit 62 may end the control if the high-rate deterioration suppression control is executed when external charging is executed. Thereby, EV travel is possible up to the lower limit SL of the SOC, and a sufficient EV travel distance using electric power from external charging can be secured.

  The travel control unit 66 calculates vehicle drive power (required value) based on the vehicle speed and the accelerator opening. Further, the traveling control unit 66 receives the mode selection information from the mode control unit 64, and further calculates the required charging power of the battery 16 based on the SOC when the HV mode or the HVS mode is selected (see FIG. 4) The vehicle power obtained by adding the required charging power to the vehicle driving power is calculated. Note that when the EV mode is selected, the traveling control unit 66 sets the vehicle driving power as the vehicle power.

  And when vehicle power is smaller than an engine starting threshold value, the traveling control part 66 controls the vehicle drive device 22 to perform EV traveling. On the other hand, when the vehicle power is equal to or higher than the engine start threshold value, traveling control unit 66 controls vehicle drive device 22 to operate engine 2 and perform HV traveling. At this time, the battery 16 is charged if the output of the engine 2 is greater than the vehicle power, and the battery 16 is discharged if the vehicle power is greater than the engine output.

  The external charging control unit 68 executes external charging when a predetermined charging execution condition is satisfied when an external power source is connected to the connection unit 30. Specifically, the external charging control unit 68 controls the charger 28 so as to convert electric power from an external power source electrically connected to the connection unit 30 into a voltage level of the battery 16 and output it to the battery 16. .

  FIG. 7 is a flowchart showing an example of a processing procedure of the high rate deterioration suppression control executed by the ECU 26. The process shown in this flowchart is called from the main routine and executed every predetermined period Δt.

  Referring to FIG. 7, roughly, ECU 26 outputs power from battery 16 (YES in step S52) when calculated high rate deterioration evaluation value ΣD is lower than the threshold value (YES in step S50). If the SOC is equal to or higher than the SOC target (YES in step S54), high rate deterioration suppression control for increasing the SOC target SC is executed (step S60). During charging of battery 16 (NO in step S52) or when the SOC is lower than the SOC target (NO in step S54), ECU 26 does not raise target SC. When the SOC becomes equal to or greater than the target SC by a predetermined value ΔSth (YES in step S70), the ECU 26 selects the EV mode (step S80). By such processing, high-rate deterioration suppression control can be realized without making the user feel as uncomfortable as possible.

  Hereinafter, it demonstrates in detail along a flowchart. The ECU 26 detects the current I input / output to / from the battery 16 by the current sensor 24 (step S10). Next, the ECU 26 calculates the SOC of the battery 16 (step S20). Various known methods can be used for calculating the SOC.

  Subsequently, the ECU 26 calculates the damage amount D of the battery 16 using the above equation (1) based on the current I detected in step S10 and the SOC calculated in step S20 (step S30). Further, the ECU 26 calculates an evaluation value ΣD indicating the degree of high rate deterioration of the battery 16 based on the damage amount D calculated in step S30 using the above-described equation (2) (step S40). Then, the ECU 26 determines whether or not the evaluation value ΣD is below a threshold value SDth (negative value) (step S50).

  If it is determined that evaluation value ΣD is below the threshold value (YES in step S50), ECU 26 determines whether or not current I of battery 16 is greater than 0 (during power output) ( Step S52). When current I of battery 16 is greater than 0 (YES in step S52), ECU 26 determines whether or not deviation ΔSOC between SOC and SOC target (SC) is 0 or more (that is, SOC is greater than or equal to target SC). (Step S54).

  If ΔSOC is equal to or greater than 0 (YES in step S54), ECU 26 further determines whether or not target SC is smaller than value SC2 (FIG. 3) (step S56). If target SC is smaller than value SC2 (YES in step S56), ECU 26 raises target SC by a predetermined amount α (step S60). When the ECU 26 increases the target SC by a predetermined amount α, the ECU 26 increases the target SC by applying a predetermined rate limit in order to avoid a sudden change in the SOC display on the SOC display screen 34 (FIG. 2) (rate processing). ).

  When it is determined in step S50 that evaluation value ΣD is not below the threshold value (NO in step S50), ECU 26 proceeds to step S70 (described later) without executing step S60.

  If it is determined in step S52 that current I is 0 or less (during charging) (NO in step S52), it is determined in step S54 that ΔSOC is smaller than 0 (SOC is lower than target SC). If (NO in step S54), or if it is determined in step S56 that target SC has reached value SC2 (NO in step S56), ECU 26 proceeds to step S70 without executing step S60. .

  Next, the ECU 26 determines whether or not the deviation ΔSOC (= SOC−target SC) is greater than or equal to a predetermined amount ΔSth (step S70). If ΔSOC is equal to or greater than predetermined amount ΔSth (YES in step S70), ECU 26 selects the EV mode (step S80). On the other hand, when ΔSOC is smaller than predetermined amount ΔSth (NO in step S70), the process proceeds to return without executing the process of step S70.

  FIG. 8 is a diagram showing an example of the transition of the SOC and its target SC when the high-rate deterioration suppression control is executed in the first embodiment. FIG. 8 also shows the SOC display of the SOC display screen 34 (FIG. 2) at several timings.

  Referring to FIG. 8, line k11 indicates the transition of the SOC, and thick line k12 indicates the transition of the target SC that is the control target of the SOC. In this example, power is taken out from the battery 16 during each period of times t11 to t12, t13 to t14, and t15 to t16 (power output), and the battery 16 is charged during other periods.

  In the power take-out period, when the SOC is equal to or higher than the target SC (ΔSOC ≧ 0), the target SC is raised (immediately after times t11, t13, t15). When the SOC is lower than the target SC (ΔSOC <0), the target SC is not raised.

  Even during the charging period, the target SC is not raised. When the target SC is raised during the charging period, ΔSOC does not increase even though charging is being performed, and it is difficult to return to the EV mode, and the SOC does not increase on the SOC display screen 34. This is because there is a possibility of feeling uncomfortable.

  In this example, during the charging period from time t16 to t18, continuous regenerative charging is performed by traveling on a continuous downhill road, and at time t17, the deviation ΔSOC between the SOC and the target SC becomes a predetermined amount ΔSth. Has reached. That is, since the SOC is higher than the target SC by a predetermined amount ΔSth or more, the EV mode is selected at time t17.

  As described above, in the first embodiment, the target SC can be raised when the battery 16 is outputting electric power for raising the SOC target by the high-rate deterioration suppression control. When power is input to the battery 16, the target SC is not increased. As a result, regardless of the situation in which power is input to the battery 16 (during traveling on a long downhill road, external charging, etc.), the EV travel distance is shortened because the target SC has increased, or the SOC is displayed on the SOC display screen 34. It is possible to prevent the user from feeling as uncomfortable as not rising.

[Embodiment 2]
In the first embodiment, the SOC target can be raised when the battery 16 is outputting power for raising the SOC target by the high-rate deterioration suppression control. However, the accelerator opening (accelerator pedal operation amount) is limited. When larger than the fixed amount, the SOC target may be increased. When the accelerator opening is equal to or smaller than a predetermined amount, the SOC target is not increased. This prevents the user from feeling as uncomfortable as possible that the EV travel distance is shortened and the SOC does not increase on the SOC display screen 34 even when sufficient regenerative charging is performed, for example, when traveling on a long downhill road. can do.

  The overall configuration of the electric vehicle according to the second embodiment is the same as that of the electric vehicle according to the first embodiment shown in FIG.

  FIG. 9 is a flowchart showing an example of the processing procedure of the high rate deterioration suppression control executed by the ECU 26 in the second embodiment. The processing shown in this flowchart is also called from the main routine and executed every predetermined period Δt.

  Referring to FIG. 9, in this flowchart, roughly, ECU 26 determines that accelerator opening is a predetermined amount Ac (for example, if YES in step S150) when calculated high-rate deterioration evaluation value ΣD is lower than a threshold value. If the SOC is greater than 0 (YES in step S152) and the SOC is equal to or higher than the SOC target (YES in step S154), high rate deterioration suppression control for raising the SOC target SC is executed (step S160). When the accelerator opening is equal to or smaller than predetermined amount Ac (NO in step S152) or when the SOC is lower than the SOC target (NO in step S154), ECU 26 does not raise target SC. When the SOC becomes equal to or greater than the target SC by a predetermined value ΔSth (YES in step S170), the ECU 26 selects the EV mode (step S180).

  Hereinafter, it demonstrates in detail along a flowchart. Each process of steps S110 to S150 is the same as each process of steps S10 to S50 shown in FIG. Also, the processes in steps S170 and S180 are the same as the processes in steps S70 and S80 shown in FIG. 7, respectively.

  If it is determined in step S150 that evaluation value ΣD is below the threshold value (YES in step S150), ECU 26 determines whether or not the accelerator opening is larger than a predetermined amount Ac (step S152). The predetermined amount Ac is, for example, 0, but may be a value larger than 0. When accelerator opening is larger than predetermined amount Ac (YES in step S152), ECU 26 determines whether or not deviation ΔSOC between SOC and SOC target (SC) is 0 or more (that is, SOC is greater than or equal to target SC). (Step S154).

  If ΔSOC is equal to or greater than 0 (YES in step S154), ECU 26 further determines whether or not target SC is smaller than value SC2 (FIG. 3) (step S156). If target SC is smaller than value SC2 (YES in step S156), ECU 26 raises target SC to the actual SOC (step S160). Note that the ECU 26 increases the target SC by applying a predetermined rate limit in order to avoid a sudden change in the SOC display on the SOC display screen 34 (FIG. 2) when raising the target SC to the actual SOC (rate processing). .

  If it is determined as “NO” in the processes of steps S150, S152, S154, and S156, the ECU 26 proceeds to step S170 without executing step S160, and the deviation ΔSOC (= SOC−target SC). Is greater than or equal to a predetermined amount ΔSth. If ΔSOC is equal to or greater than predetermined amount ΔSth (YES in step S170), ECU 26 selects the EV mode (step S180).

  FIG. 10 is a diagram illustrating an example of the transition of the SOC and its target SC when the high-rate deterioration suppression control is being executed in the second embodiment. Note that FIG. 10 also shows the accelerator opening and the SOC display of the SOC display screen 34 (FIG. 2) at several timings.

  Referring to FIG. 10, line k21 indicates the transition of the SOC, and thick line k22 indicates the transition of the target SC. In this example, the accelerator opening is larger than a predetermined amount Ac (referred to as “0”) in each of the times t21 to t22 and t23 to t24 (hereinafter also referred to as “accelerator ON period”), and in other periods. The accelerator opening is equal to or less than a predetermined amount Ac (hereinafter also referred to as “accelerator OFF period”).

  In the accelerator ON period, when the SOC is equal to or higher than the target SC (ΔSOC ≧ 0), the target SC is increased (immediately after time t23, immediately before time t24, etc.). When the SOC is lower than the target SC (ΔSOC <0), the target SC is not raised.

  The target SC is not raised even during the accelerator OFF period. If the target SC is raised during the accelerator-off period, ΔSOC will not increase despite the fact that the accelerator is off and regenerative charging is being performed when traveling on a downhill road, etc., making it difficult to return to the EV mode. This is because the SOC does not increase on the SOC display screen 34 and the user may feel uncomfortable.

  In this example, during the accelerator OFF period from time t24 to t26, continuous regenerative charging is performed by traveling on a continuous downhill road, and deviation ΔSOC reaches a predetermined amount ΔSth at time t25. That is, since the SOC is higher than the target SC by a predetermined amount ΔSth or more, the EV mode is selected at time t25.

  In the above description, it is determined in step S152 in FIG. 9 whether or not the accelerator opening is larger than the predetermined amount Ac. However, vehicle driving power may be used instead of the accelerator opening. That is, in step S152, it may be determined whether or not the vehicle driving power is greater than a predetermined amount (for example, 0).

  As described above, in the second embodiment, the target SC can be raised when the accelerator opening (or vehicle drive power) is larger than a predetermined amount for raising the SOC target by the high-rate deterioration suppression control. When the accelerator opening (or vehicle drive power) is equal to or less than a predetermined amount, the target SC is not increased. As a result, for example, when a sufficient regenerative charge is performed, for example, when traveling on a long downhill road, the target SC is increased, so that the EV travel distance is shortened, or the SOC does not increase on the SOC display screen 34. It is possible to avoid giving to the user as much as possible.

  In each of the above embodiments, in high-rate deterioration suppression control that suppresses high-rate deterioration by increasing the SOC, when raising the SOC target, when the power carry-out determination from the battery 16 is established ( In the first embodiment, when the battery 16 is outputting power, in the second embodiment, when the accelerator opening (or the vehicle driving force) is larger than a predetermined amount), the SOC target can be increased. However, such a method for raising the SOC target itself can be applied not only to high-rate deterioration suppression control but also to other control for raising the SOC target. For example, even when forced charging is performed due to a decrease in SOC and the SOC is raised by raising the SOC target, the method for raising the SOC target described in each of the above embodiments is applied. Can do.

  Further, in each of the embodiments described above, the charger 28 that converts the power supplied from the external power source into the voltage level of the battery 16 is provided. The battery 16 may be directly charged (without power conversion) by an external power source.

  The embodiments disclosed this time are also scheduled to be combined as appropriate within a technically consistent range. The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

2 Engine, 4 Power split device, 6, 10 Motor generator, 8 Transmission gear, 12 Drive shaft, 14 Wheel, 16 Battery, 18, 20 Power converter, 22 Vehicle drive device 24 Current sensor, 28 Charger, 30 Connection part 32 display unit, 34 SOC display screen, 36 SOC display unit, 38 target instruction unit, 52 SOC calculation unit, 54 damage amount calculation unit, 56 evaluation value calculation unit, 58 storage unit, 60 determination unit, 62 SOC control unit, 64 mode control unit, 66 travel control unit, 68 external charge control unit, 100 hybrid vehicle.

Claims (1)

A vehicle driving device configured to receive electric power to generate vehicle driving force and to generate power;
A secondary battery that exchanges power with the vehicle drive device;
A control device configured to switch between an EV mode that consumes the SOC of the secondary battery and a mode that controls the SOC to a predetermined target;
In the case where the control device is further evaluated that the secondary battery is deteriorated by an evaluation value indicating the degree of deterioration of the secondary battery due to a deviation in salt concentration in the secondary battery, It is configured to execute deterioration suppression control for increasing the SOC by increasing the SOC target,
The controller is
During the execution of the deterioration suppression control, when the carry-out determination of power from the secondary battery is established, the SOC target can be increased,
When the SOC is higher than the target by a predetermined value or more, the EV mode is selected,
The carry-out determination is established when the secondary battery outputs power, or when the accelerator opening or the vehicle driving force is greater than a predetermined amount.

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