INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2019-161403 filed on Sep. 4, 2019 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The disclosure relates to a vehicle control device that controls charge and discharge of a battery mounted on the vehicle.

2. Description of Related Art

In recent years, electric power consumed by in-vehicle devices has been increased due to increased functionality and higher added value of vehicles. Thus, for a battery that is a power supply source for the in-vehicle devices, charge-discharge control is required for optimally maintaining a state of charge (SOC) of the battery to suppress the battery from running down.

Japanese Unexamined Patent Application Publication No. 2017-093070 (JP 2017-093070 A) describes control in which, when the state of charge of a battery for in-vehicle devices decreases while the vehicle is parked, the battery for the in-vehicle devices is charged with electric power of a high-voltage battery that is a power supply source for a traction motor. However, the control described in JP 2017-093070 A is not performed when the state of charge of the high-voltage battery is less than a predetermined value. Also, the control in JP 2017-093070 A is difficult to be applied to a vehicle on which the high-voltage battery is not mounted (for example, engine vehicle).

Thus, Japanese Unexamined Patent Application Publication No. 2007-221970 (JP 2007-221970 A) describes control for charging a battery in an early stage based on a state of a vehicle during use of the vehicle, in which a power supply system is operating.

SUMMARY

However, the control described in JP 2007-221970 A does not consider how the vehicle is used, that is, repeated short-time traveling (short trips), long-time parking, and the like. Short trips cannot secure sufficient charge time, and long-time parking may significantly decrease the state of charge due to discharge. Thus, even if the control described in JP 2007-221970 A is performed, the state of charge may be unable to become a predetermined target value during the use of the vehicle.

If the battery cannot be sufficiently charged during the use of the vehicle, the state of charge of the battery gradually decreases due to further repeated short trips or long-time parking, which may cause the battery to run down in the future. Thus, there is room for studying suitable charge control for the battery in order to suppress insufficient charge during the use of the vehicle.

The disclosure provides a vehicle control device that can suitably suppress decrease in a state of charge of a battery due to insufficient charge during use of a vehicle.

A first aspect of the disclosure relates to a vehicle control device configured to control charge and discharge of a battery mounted on a vehicle. The vehicle control device includes an obtaining unit configured to obtain a parking time of the vehicle, a setting unit configured to derive a charge voltage of the battery based on at least the parking time obtained by the obtaining unit, and a voltage control unit configured to control charge of the battery based on the charge voltage of the battery derived by the setting unit when the vehicle is traveling.

In the above first aspect, the setting unit may be configured to estimate a charge-discharge balance of the battery based on a state of use of the vehicle including at least the parking time, and configured to derive an evaluation value obtained by evaluating the charge-discharge balance according to a predetermined rule. The voltage control unit may be configured to control the charge voltage of the battery based on the evaluation value.

In the above first aspect, the parking time may be a duration of time for which a power supply of the vehicle was OFF most recently.

In the above first aspect, the vehicle may be a shared vehicle shared by a plurality of users, and the parking time may be a time period from a time when use of the vehicle is ended by a previous user to a time when use of the vehicle is started by a current user.

In the above first aspect, the vehicle may be a shared vehicle shared by a plurality of users, and the parking time may be a time period from a time when use of the vehicle is scheduled to be ended by a current user to a time when use of the vehicle is scheduled to be started by a next user.

The vehicle control device according to the above first aspect may further include a communication unit configured to communicate with a management center that manages usage of the shared vehicle. The obtaining unit may be configured to obtain, from the management center, the time when the use of the vehicle is ended by the previous user and the time when the use of the vehicle is started by the current user.

The vehicle control device according to the above first aspect may further include a communication unit configured to communicate with a management center that manages usage of the shared vehicle. The obtaining unit may be configured to obtain, from the management center, the time when the use of the vehicle is scheduled to be ended by the current user and the time when the use of the vehicle is scheduled to be started by the next user.

In the above first aspect, the obtaining unit may be configured to obtain vehicle information regarding the charge-discharge balance of the battery; and the setting unit may be configured to derive the evaluation value based on the parking time and the vehicle information.

In the above first aspect, the vehicle information may include a state of a discharge element related to discharge of the battery and a state of a charge element related to charge of the battery.

In the above first aspect, the discharge element may include a plurality of in-vehicle devices that consume electric power of the battery, and the state of the discharge element may include whether the in-vehicle devices are ON or OFF.

In the above first aspect, the charge element may include a generated current flowing toward the battery, an internal resistance of the battery, and a traveling time of the vehicle; and the state of the charge element may include whether the generated current, the internal resistance, and the traveling time are each equal to or greater than a predetermined threshold.

In the above first aspect, the obtaining unit may be configured to obtain, as the vehicle information, the traveling time of the vehicle from a departure point to a destination point. The traveling time of the vehicle may be set for the vehicle.

In the above first aspect, the parking time may be provided with a score in advance such that the score has a higher value as a duration of the parking time becomes longer and the score has a higher value when the state of the charge element is a state where an amount of charge to the battery is estimated to be small. Each of a plurality of the discharge elements may be provided with a score in advance such that the score has a higher value as an amount of discharge from the battery is larger and the score has a higher value when the state of the charge element is the state where the amount of charge to the battery is estimated to be small. The setting unit may be configured to calculate a total score by adding all of the score of the parking time and the score of each of the discharge elements, and configured to determine the evaluation value based on the total score. The score of each of the discharge elements may be a score provided in accordance with a current state of each of a plurality of the charge elements.

In the above first aspect, the obtaining unit may be configured to obtain vehicle environment information regarding an environment around the vehicle including at least one of a season, daytime or nighttime, weather, a temperature, a road condition, and a traveling time. The setting unit may be configured to assign a predetermined weight to the score of each of the discharge elements and the score of the parking time based on the vehicle environment information.

According to the first aspect, it is possible to suitably suppress decrease in the state of charge of the battery due to insufficient charge during the use of the vehicle.

