JP6981286B2 - Electric vehicle - Google Patents

Description

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

When the salt concentration of the electrolytic solution of the secondary battery is uneven due to the charging and discharging of the secondary battery, the internal resistance of the secondary battery increases. The increase in internal resistance due to this uneven salt concentration is referred to as "high rate deterioration" or the like to distinguish it from the aged deterioration of the material constituting the secondary battery.

High-rate deterioration has a characteristic that it is promoted when the secondary battery is used in the region where the SOC (State Of Charge) of the secondary battery is low. It is considered that this is because the expansion / contraction of the negative electrode of the battery becomes large in the region where the SOC is low, and the electrolytic solution in the battery cell is easily extruded, so that the salt concentration difference in the battery cell surface is likely to occur.

Japanese Unexamined Patent Publication No. 2016-182022 (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, and when the evaluation value ΣD exceeds the threshold value, the SOC is increased by increasing the SOC control target. According to this electric vehicle, when the evaluation value ΣD exceeds the threshold value, the use of the secondary battery in the low SOC region is avoided, so that high rate deterioration can be suppressed (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-182022

When the SOC of the secondary battery is higher than the control target (SOC target), the motor is basically driven using the electric power stored in the secondary battery until the SOC drops to the control target (hereinafter referred to as "EV driving"). ) Is performed. Then, when the SOC drops to the control target, 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 increasing the SOC target. However, for example, even though the secondary battery is sufficiently charged by continuous regenerative power generation accompanying long downhill road driving or a power source outside the vehicle, the SOC target rises, and the subsequent EV There is a possibility that the user may feel uncomfortable in terms of mileage, 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 control the high rate deterioration of an electric vehicle equipped with a secondary battery to suppress the high rate deterioration of the secondary battery as much as possible. It is to be realized without giving a sense of discomfort.

The electric vehicle in the present disclosure includes a vehicle drive device configured to receive electric power to generate electric power and generate electric power, a secondary battery for exchanging electric power between the vehicle drive devices, 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 as having deteriorated by the evaluation value (ΣD) indicating the degree of deterioration (high rate deterioration) of the secondary battery due to the bias of the salt concentration in the secondary battery. In some cases, it is configured to execute deterioration suppression control (high rate deterioration suppression control) that raises the SOC by increasing the SOC target. Here, the control device can raise the SOC target when the determination of power removal 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 power removal determination 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 carry-out judgment is not established, the SOC target is not raised. As a result, the EV mileage will be shortened due to the increase in the SOC target, even though the secondary battery is fully charged (for example, when driving on a long downhill road or when charging with a power source 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 display is displayed because the SOC target has increased despite the above-mentioned 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 as much as possible.

Then, in this electric vehicle, the EV mode is selected when the SOC is higher than the target by a predetermined value or more. As a result, even if the SOC target is increased by the high rate deterioration suppression control, it is possible to suppress the decrease in the EV mileage as much as possible.

According to the electric vehicle in the present disclosure, the high rate deterioration suppression control for suppressing the high rate deterioration of the secondary battery can be realized without giving a sense of discomfort to the user as much as possible. Further, even if the SOC target is increased by the high rate deterioration suppression control, it is possible to suppress the decrease in the EV mileage as much as possible.

FIG. 3 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. It is a figure which showed an example of the SOC display screen displayed in the display part shown in FIG. It is a figure which showed an example of the transition of SOC of a battery. It is a figure which showed the relationship between SOC and charge request power. It is a figure which showed an example of the relationship between the evaluation value of high rate deterioration and the SOC target. It is a functional block diagram of the ECU shown in FIG. It is a flowchart which showed an example of the processing procedure of the high rate deterioration suppression control executed by the ECU. It is a figure which showed an example of the transition of SOC and the target when high rate deterioration suppression control is executed in Embodiment 1. FIG. It is a flowchart which showed an example of the processing procedure of the high rate deterioration suppression control executed by the ECU in Embodiment 2. It is a figure which showed an example of the transition of SOC and the target when high rate deterioration suppression control is executed in Embodiment 2. FIG.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Hereinafter, a plurality of embodiments will be described, but it is planned from the beginning of the application to appropriately combine the configurations described in the respective embodiments. The same or corresponding parts in the drawings are designated by the same reference numerals and the 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. With reference to FIG. 1, the 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. Further, the hybrid vehicle 100 further includes a charger 28, a connection unit 30, and a display unit 32.

The vehicle driving device 22 is configured to generate a vehicle driving force and to generate electricity. Specifically, the vehicle driving device 22 includes an engine 2, a power dividing device 4, motor generators 6 and 10, and power converters 18 and 20.

The engine 2 is an internal combustion engine that outputs power by converting the thermal energy generated by burning fuel into the kinetic energy of movers such as pistons and rotors. 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 fuels are suitable.

Motor generators 6 and 10 are AC rotary 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 dividing device 4, and is also used 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 generate regenerative power generation.

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

The battery 16 is a rechargeable secondary battery, for example, a secondary battery such as a nickel hydrogen battery or a lithium ion battery. The battery 16 supplies electric power to the power converters 18 and 20. Further, the battery 16 is charged by receiving the generated power at the time of power generation of the motor generator 6 and / or 10. Further, the battery 16 can be charged by receiving electric power supplied from a power source (not shown) outside the vehicle through the connection portion 30. The current sensor 24 detects the current I input / output to / 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.

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

The power converter 18 executes bidirectional DC / AC power conversion between the motor generator 6 and the battery 16 based on the control signal received from the ECU 26. Similarly, the power converter 20 executes bidirectional DC / AC power conversion between the motor generator 10 and the battery 16 based on the control signal received from the ECU 26. As a result, the motor generators 6 and 10 can output positive torque for operating as an electric motor or negative torque for operating as a generator, accompanied by transfer of electric power to and from the battery 16. The power converters 18 and 20 are configured by, for example, an inverter. A boost converter for DC voltage conversion may be arranged between the battery 16 and the power converters 18 and 20.

The charger 28 converts the electric power from the power source outside the vehicle electrically connected to the connection portion 30 into the voltage level of the battery 16 and outputs the power to the battery 16 (hereinafter, the power source outside the vehicle is also referred to as an "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. The method of receiving power from the external power source is not limited to contact power reception using the connection unit 30, and power may be received from the external power source in a non-contact 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 able to accept user operations, and may be, for example, a display provided with a touch panel. Typical information displayed on the display unit 32 is the SOC of the battery 16.

FIG. 2 is a diagram showing an example of an SOC display screen displayed on the display unit 32. With reference to FIG. 2, the SOC display screen 34 includes an SOC display unit 36 and a target designator unit 38. The SOC display unit 36 displays the deviation (ΔSOC) of the SOC with respect to the SOC control target indicated by the target designator 38. Although the target of the SOC indicated by the target indicating unit 38 may change as described later, the position of the target indicating unit 38 on the SOC display screen 34 does not change.

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

With reference to FIG. 1 again, the ECU 26 includes a CPU (Central Processing Unit), a storage device, an input / output buffer, and the like (none of them are shown), and controls each device in the hybrid vehicle 100. Note that these controls are not limited to software processing, but can also be processed by dedicated hardware (electronic circuits).

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

When the vehicle power is small, the ECU 26 controls the vehicle drive device 22 so that the engine 2 is stopped and the vehicle is driven only by the motor generator 10 (EV traveling). As a result, 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 as to operate the engine 2 to travel (HV travel). At this time, if the output of the engine 2 is larger than the vehicle power, the battery 16 is charged, and if the vehicle power is larger than the engine output, the battery 16 is discharged.

Then, the ECU 26 appropriately switches between a mode (EV mode) in which the SOC of the battery 16 is positively consumed by proactively performing EV running while allowing HV running, and SOC by appropriately switching between HV running and EV running. The mode to maintain is selectively applied to control the running of the vehicle. The latter mode includes a mode in which the SOC is maintained at the lower limit when the SOC drops to a predetermined lower limit (HV mode) and a mode in which the SOC is maintained at a state 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 as to convert the electric power supplied from the external power source electrically connected to the connection portion 30 into the voltage level of the battery 16 and output the electric power to the battery 16 during the execution of the external charging. 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 deviation of the salt concentration of the battery 16 due to the charging / discharging of the battery 16. The calculation method of the evaluation value (ΣD) will be described in detail later, but this evaluation value shows a negative value when the salt concentration is biased due to the overcharged usage of the battery 16. When the battery 16 is used with excessive discharge and the salt concentration is biased, a positive value is shown.

As mentioned above, high rate degradation has the property of being accelerated when the battery is used in the low SOC region. Therefore, when it is evaluated that high-rate deterioration is progressing based on the evaluation value (ΣD), it is conceivable to raise the SOC by increasing the SOC control target (hereinafter, such SOC control is referred to as “high-rate deterioration”. It is called "suppression control").

However, for example, despite the continuous regenerative power generation and external charging that accompanies driving on a long downhill road, the SOC control target has been raised, and as a result, the EV mileage and display unit thereafter. There is a possibility that the user may feel uncomfortable in the SOC display of 32 or the like.

Therefore, in the first embodiment, the ECU 26 makes it possible to raise the SOC target when the electric power is output from the battery 16 (during discharge) for 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, despite the situation where power is input to the battery 16 (for example, when traveling on a long downhill road or when externally charging), the user feels as much as possible that the EV mileage is shortened due to the increase in the SOC target. You can avoid giving it. Further, when the deviation (ΔSOC) between the SOC and the SOC target is displayed on the display unit 32, the SOC target has risen despite the above-mentioned situation in which the battery 16 is sufficiently charged, so that the display is displayed. It is possible to prevent the user from feeling uncomfortable, such as the SOC not increasing (because the SOC target increases).

Then, the ECU 26 selects the EV mode when the SOC is higher than the target by a predetermined value or more. As a result, even if the SOC target is increased by the high rate deterioration suppression control, it is possible to suppress the decrease in the EV mileage as much as possible.

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

The EV mode is a mode in which the SOC of the battery 16 is positively consumed, and 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, the charge request power of the battery 16 is set to zero during the EV mode. As a result, the SOC may temporarily increase due to the regenerative power recovered when the vehicle decelerates or the power generated by the operation of the engine 2, but as a result, the discharge rate is higher than the charge. Is relatively large, and as a whole, the SOC decreases as the mileage increases.

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

When the SOC drops 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 in which the SOC is controlled (maintained) to the lower limit SL. Specifically, when the SOC falls below the lower limit SL, the engine 2 operates (HV running), and when the SOC rises, the engine 2 stops (EV running). Thus, in the HV mode, the engine 2 operates to maintain the SOC.

Even in the HV mode, if the SOC becomes high, the engine 2 will stop. That is, the HV mode is not limited to the HV running in which the engine 2 is constantly operated, and the EV running and the HV running are possible even in the HV mode.

The HVS mode is a mode for maintaining 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 (SC1> SL) at the time of the user request until the time t2 when the request is canceled. The request and cancellation of the transition to the HVS mode are input by the user, for example, from the display unit 32 that can be operated by the user.

In the HVS mode, the engine 2 operates when the SOC drops below the value SC1 (HV running), and the engine 2 stops when the SOC rises (EV running). In this way, even in the HVS mode, the engine 2 operates in order to maintain the SOC. The HV mode and HVS mode in which SOC is maintained may be collectively referred to as "CS (Charge Sustain) mode".

In the HVS mode as well, as in the HV mode, the engine 2 stops when the SOC becomes high. That is, the HVS mode is not limited to the HV running in which the engine 2 is constantly operated, and the EV running and the HV running are also possible in the HVS mode.

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

In the HV mode and the HVS mode in which the SOC is maintained, the charge request 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 (lower limit SL in HV mode, value SC1 in HVS mode). Will be done. Then, the vehicle drive device 22 is controlled so as to generate a power (vehicle power) obtained by adding the charge request power to the vehicle drive power. As a result, in the HV mode, the SOC is controlled in the vicinity of the lower limit SL, and in the HVS mode, the SOC is controlled in the vicinity of the value SC1.

When the HV mode is selected at time t4 and it is evaluated that the high rate deterioration is progressing by the evaluation value (ΣD) of the high rate deterioration, the high rate deterioration suppression control is executed and the SOC control target is set. It is increased from the lower limit SL 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 high rate deterioration and the SOC target. With reference to FIG. 5, high rate degradation has the property of being promoted when the battery is used in the low SOC region as described above, and in particular when 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) rises by a predetermined value. The rate is increased to the value SC2. As a result, the increasing tendency (increase in the negative direction) of the evaluation value (ΣD) is suppressed. Although not shown in particular, the SOC target may be gradually increased according to the increase in the evaluation value (ΣD) (increase in the negative direction).

With reference to FIG. 3 again, while the high rate deterioration suppression control is being executed, external charging is started at time t5, and the SOC rises. Then, the external charging ends at time t6, and in this example, the battery 16 is charged to the fully charged state (SOC = MAX). By charging the battery 16 to a 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 end of external charging.

FIG. 6 is a functional block diagram of the ECU 26 shown in FIG. With reference to FIG. 6, the ECU 26 includes an SOC calculation unit 52, a damage amount calculation unit 54, an evaluation value calculation unit 56, a storage unit 58, a determination unit 60, an SOC control unit 62, and a mode control unit 64. And a traveling 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 the voltage of the battery 16 detected by the current sensor 24 (FIG. 1) and / or a voltage sensor (not shown). As for the specific calculation method of SOC, a method using an integrated value of current I, a method using an OCV-SOC curve showing the relationship between the open circuit voltage (OCV (Open Circuit Voltage)) 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 bias of the salt concentration in the battery 16 based on the current I input / output to / from the battery 16 and the energization time thereof. The damage amount D is calculated in a predetermined period Δt based on, for example, the following equation (1).

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 previously calculated value of the damage amount D calculated before the cycle Δt. D (N-1) is stored in the storage unit 58 at the time of the previous calculation, and is read out from the storage unit 58 at the time of the current calculation.

Α × Δt × D (N-1) of the second term on the right side in the formula (1) is a reduction term of the damage amount D, and indicates a component when the bias of the salt concentration is alleviated. α is a forgetting coefficient, which is a coefficient corresponding to the diffusion rate of ions in the electrolytic solution of the battery 16. The higher the diffusion rate, the larger the forgetting coefficient 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 coefficient α is larger (that is, the higher the ion diffusion rate is) and the longer the period Δt is.

The forgetting coefficient α depends on the SOC and temperature of the battery 16. The correspondence between the forgetting coefficient α and the SOC and temperature of the battery 16 is obtained in advance by an experiment or the like and stored in the storage unit 58, and the forgetting coefficient 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 coefficient α can be set to a larger value as the SOC is higher, and if the SOC is the same, the value can be set to a larger value as the temperature of the battery 16 is higher.

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

The current coefficient β and the limit threshold value C depend on the SOC and temperature of the battery 16. The correspondence between each of the current coefficient β and the limit threshold value 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, based on the SOC and temperature of the battery 16 at the time of calculation. Therefore, the current coefficient β and the limit threshold value C are set. For example, if the temperature of the battery 16 is the same, the limit threshold value C is set to a larger value as the SOC is higher, and if the SOC is the same, the value is set to a larger value as the temperature of the battery 16 is higher.

In this way, by expressing the occurrence and mitigation of the salt concentration bias by the above increase and decrease terms and calculating the current damage amount D, the change (increase / decrease) in the salt concentration bias considered to be the cause of the high rate deterioration. ) Can be properly grasped.

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 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, for example, the following equation (2).

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

The attenuation coefficient γ is set to a value smaller than 1. Since the bias of the salt concentration is alleviated by the diffusion of ions with the passage of time, the previous evaluation value ΣD (N-1) decreases when calculating the current evaluation value ΣD (N). It is something to consider. The correction coefficient η is set as appropriate.

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

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, the high rate deterioration has a characteristic that it is promoted especially when a current in the charging direction flows in the low SOC region. Specifically, in the determination unit 60, the evaluation value ΣD increases in the negative direction. It is determined whether or not the threshold value is below SDth (negative value).

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, the mode control unit 64 selects the EV mode. When the SOC drops to the lower limit SL due to 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 the user's request. If the above request is made during the EV mode, the SOC is maintained at the value at that time. 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. The control to increase to (SC2> SL) is executed (high rate deterioration suppression control).

Here, the SOC control unit 62 makes it possible to raise the SOC target when the battery 16 is outputting electric power when executing the high-rate deterioration suppression control. When the battery 16 is outputting power, the SOC target may be raised at all times (up to the value SC2), or the SOC target may be raised only when the SOC is equal to or higher than the SOC target (up to the value SC2). When the SOC is lower than the SOC target, the SOC target is not raised.) When the SOC target is raised step by step, the SOC display of the display unit 32 suddenly changes. Therefore, the SOC control unit 62 raises the SOC target with a predetermined rate limit.

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

The travel control unit 66 calculates the vehicle drive power (required value) based on the vehicle speed and the accelerator opening degree. Further, the traveling control unit 66 receives mode selection information from the mode control unit 64, and when the HV mode or the HVS mode is selected, further calculates the charge request power of the battery 16 based on the SOC (FIG. FIG. 4) Calculate the vehicle power by adding the charge request power to the vehicle drive power. When the EV mode is selected, the travel control unit 66 uses the vehicle drive power as the vehicle power.

Then, when the vehicle power is smaller than the engine start threshold value, the travel control unit 66 controls the vehicle drive device 22 so as to perform EV travel. On the other hand, when the vehicle power is equal to or higher than the engine start threshold value, the travel control unit 66 controls the vehicle drive device 22 so as to operate the engine 2 to perform HV travel. At this time, if the output of the engine 2 is larger than the vehicle power, the battery 16 is charged, and if the vehicle power is larger than the engine output, the battery 16 is discharged.

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

FIG. 7 is a flowchart showing an example of the 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 cycle Δt.

In general, the ECU 26 outputs power from the battery 16 when the calculated evaluation value ΣD of high rate deterioration is below the threshold value (YES in step S50) with reference to FIG. 7 (in step S52). YES), and when the SOC is equal to or higher than the SOC target (YES in step S54), high-rate deterioration suppression control for raising the SOC target SC is executed (step S60). During charging of the battery 16 (NO in step S52) or when the SOC is lower than the SOC target (NO in step S54), the ECU 26 does not raise the target SC. Then, when the SOC becomes a predetermined value ΔSth or more than the target SC (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 giving a sense of discomfort to the user as much as possible.

Hereinafter, the details will be described with reference to the 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 to calculate 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 equation (2) (step S40). Then, the ECU 26 determines whether or not the evaluation value ΣD is below the threshold value SDth (negative value) (step S50).

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

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

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

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

Next, the ECU 26 determines whether or not the deviation ΔSOC (= SOC-target SC) is equal to or greater than the predetermined amount ΔSth (step S70). Then, if ΔSOC is a predetermined amount ΔSth or more (YES in step S70), the ECU 26 selects the EV mode (step S80). On the other hand, when ΔSOC is smaller than the predetermined amount ΔSth (NO in step S70), the process of step S70 is not executed and the process is shifted to the return.

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. Note that FIG. 8 also shows the SOC display of the SOC display screen 34 (FIG. 2) at some timings.

With reference to FIG. 8, the line k11 shows the transition of the SOC, and the thick line k12 shows the transition of the target SC which is the control target of the SOC. In this example, electric power is taken out from the battery 16 in each period of time t11 to t12, t13 to t14, and t15 to t16 (electric power output), and the battery 16 is charged in other periods.

In the power take-out period, the target SC is raised when the SOC is equal to or higher than the target SC (ΔSOC ≧ 0) (immediately after the time t11, t13, t15). If 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 performed, it becomes difficult to return to the EV mode, and the user does not increase SOC on the SOC display screen 34. This is because there is a possibility that the person may feel uncomfortable.

In this example, continuous regenerative charging is performed by traveling on a continuous downhill road during the charging period from time t16 to t18, and the deviation ΔSOC between the SOC and the target SC becomes a predetermined amount ΔSth at time t17. 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, regarding the raising of the SOC target by the high rate deterioration suppression control, the target SC can be raised while the battery 16 is outputting electric power. When power is input to the battery 16, the target SC is not raised. As a result, despite the situation where power is input to the battery 16 (during driving on a long downhill road, external charging, etc.), the EV mileage is shortened due to the increase in the target SC, or the SOC is displayed on the SOC display screen 34. It is possible to prevent the user from feeling uncomfortable, such as not rising.

[Embodiment 2]
In the first embodiment described above, regarding the raising of the SOC target by the high rate deterioration suppression control, the SOC target can be raised when the battery 16 is outputting electric power, but the accelerator opening (accelerator pedal operation amount) is a factor. The SOC target may be elevated when it is greater than the quantification. When the accelerator opening is less than or equal to a predetermined amount, the SOC target is not raised. As a result, the user should not feel a sense of discomfort such as the EV mileage being shortened or the SOC not increasing on the SOC display screen 34 even though sufficient regenerative charging has been 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 a processing procedure of high rate deterioration suppression control executed by the ECU 26 in the second embodiment. The process shown in this flowchart is also called from the main routine and executed every predetermined cycle Δt.

Referring to FIG. 9, in this flowchart, schematically, when the calculated evaluation value ΣD of high rate deterioration is below the threshold value (YES in step S150), the accelerator opening degree is Ac (for example, a predetermined amount Ac). When it is larger 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 less than or equal to the predetermined amount Ac (NO in step S152) or when the SOC is lower than the SOC target (NO in step S154), the ECU 26 does not raise the target SC. Then, when the SOC becomes a predetermined value ΔSth or more than the target SC (YES in step S170), the ECU 26 selects the EV mode (step S180).

Hereinafter, a detailed description will be given according to a flowchart. Each process of steps S110 to S150 is the same as each process of steps S10 to S50 shown in FIG. 7, respectively. Further, each process of steps S170 and S180 is the same as each process of steps S70 and S80 shown in FIG. 7, respectively.

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

When ΔSOC is 0 or more (YES in step S154), the ECU 26 further determines whether or not the target SC is smaller than the value SC2 (FIG. 3) (step S156). Then, when the target SC is smaller than the value SC2 (YES in step S156), the ECU 26 raises the target SC to the actual SOC (step S160). When raising the target SC to the actual SOC, the ECU 26 raises the target SC by applying a predetermined rate limit in order to prevent the SOC display on the SOC display screen 34 (FIG. 2) from suddenly changing (rate processing). ..

If "NO" is determined in each of the processes of steps S150, S152, S154, and S156, the ECU 26 shifts the process to step S170 without executing step S160, and the deviation ΔSOC (= SOC-target SC). Is determined to be equal to or greater than a predetermined amount ΔSth. Then, if ΔSOC is a predetermined amount ΔSth or more (YES in step S170), the ECU 26 selects the EV mode (step S180).

FIG. 10 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 second embodiment. Note that FIG. 10 also shows the accelerator opening degree and the SOC display of the SOC display screen 34 (FIG. 2) at some timings.

With reference to FIG. 10, the line k21 shows the transition of the SOC, and the thick line k22 shows the transition of the target SC. In this example, the accelerator opening is larger than the predetermined amount Ac (referred to as 0) in each period of time t21 to t22 and t23 to t24 (hereinafter, also referred to as "accelerator ON period"), and in other periods. The accelerator opening is less than or equal to the 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 raised (immediately after time t23, immediately before time t24, etc.). If the SOC is lower than the target SC (ΔSOC <0), the target SC is not raised.

Even during the accelerator OFF period, the target SC is not raised. When the target SC is raised during the accelerator OFF period, the ΔSOC does not increase even though the accelerator is turned off and regenerative charging is performed when driving on a downhill road, and it becomes difficult to return to the EV mode. This is because the SOC may not increase on the SOC display screen 34 and the user may feel a sense of discomfort.

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 the 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, it is determined in step S152 of FIG. 9 whether or not the accelerator opening degree is larger than the predetermined amount Ac, but the vehicle driving power may be used instead of the accelerator opening degree. That is, in step S152, it may be determined whether or not the vehicle driving power is larger 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 the predetermined amount for raising the SOC target by the high rate deterioration suppression control. When the accelerator opening (or vehicle drive power) is less than or equal to a predetermined amount, the target SC is not raised. As a result, even though sufficient regenerative charging has been performed, for example, when traveling on a long downhill road, the EV mileage is shortened due to the increase in the target SC, and the SOC does not increase on the SOC display screen 34. It can be avoided as much as possible from the user.

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

Further, in each of the above embodiments, a charger 28 for converting the electric power supplied from the external power source into the voltage level of the battery 16 is provided, but without providing such a charger 28, a direct current can be provided. The battery 16 may be charged directly (without power conversion) by an external power source.

It is also planned that the embodiments disclosed this time will be appropriately combined and implemented within a technically consistent range. And it should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

2 engine, 4 power splitting device, 6,10 motor generator, 8 transmission gear, 12 drive shaft, 14 wheels, 16 battery, 18,20 power converter, 22 vehicle drive device 24 current sensor, 28 charger, 30 connection , 32 display unit, 34 SOC display screen, 36 SOC display unit, 38 target indicator unit, 52 SOC calculation unit, 54 damage amount calculation unit, 56 evaluation value calculation unit, 58 storage unit, 60 judgment unit, 62 SOC control unit, 64 mode control unit, 66 driving control unit, 68 external charge control unit, 100 hybrid vehicle.

Claims (1)

A vehicle drive device that receives electric power to generate vehicle drive force and is configured to generate electricity,
A secondary battery that exchanges electric 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 is provided.
When the control device is further evaluated as having deteriorated by the evaluation value indicating the degree of deterioration of the secondary battery due to the bias of the salt concentration in the secondary battery, the control device is evaluated as having deteriorated. It is configured to execute deterioration suppression control that raises the SOC by raising the target of the SOC.
The control device is
During the execution of the deterioration suppression control, if the determination of power output from the secondary battery is established, the SOC target can be increased.
Even if it is evaluated that the secondary battery is deteriorated by the evaluation value, if the carry-out determination is not established, the target is not raised.
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 is outputting electric power, or when the accelerator opening degree or the vehicle driving force is larger than a predetermined amount, the electric vehicle.

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