Battery control system for hybrid vehicle and method for controlling a hybrid vehicle battery

US7489101 (Eaton Corporation)

Abstract
A battery control system for hybrid vehicle includes a hybrid powertrain battery, a vehicle accessory（付属品、装備）battery, and a prime mover（原動機）driven generator adapted to（構成、適合）charge the vehicle accessory battery. A detecting arrangement is configured to（構成）monitor the vehicle accessory battery's state of charge. A controller is configured to activate the prime mover to drive the generator and recharge the vehicle accessory battery in response to the vehicle accessory battery's state of charge falling below（分詞）a first predetermined（所定）level, or transfer electrical power from the hybrid powertrain battery to the vehicle accessory battery in response to the vehicle accessory battery's state of charge falling below a second predetermined level. The invention further includes a method for controlling a hybrid vehicle powertrain system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to hybrid motor vehicles and, more particularly, to a battery control system for controlling the state of charge of a hybrid vehicle battery.

2. Background of the Invention

Motor vehicle manufacturers are actively working to develop（開発、努力、日夜、積み重ね） alternative powertrain systems in an effort to（するため、目指し）reduce the level of pollutants exhausted into the air（空気中に排出される）by conventional powertrains equipped with internal combustion engines. Significant development efforts（開発の努力）have been directed to electric and fuel-cell vehicles. Unfortunately, these alternative powertrain systems suffer from several disadvantages（欠点）and, for all practical purposes（実際、実用上）, are still under development（開発途上）. However, "hybrid" vehicles, which are equipped with an internal combustion engine and an electric traction（走行用）motor that can be operated independently or in combination with the internal combustion engine to provide motive power（原動力）for the vehicle, offer a compromise between traditional internal combustion engine powered vehicles and full electric powered vehicles.

A hybrid vehicle is typically equipped with a relatively high voltage hybrid powertrain battery, for example a 340 V battery, which provides electrical power（電力）to the electric traction motor. Many hybrid vehicles are also equipped with a lower voltage battery, for example a 12 V battery, which provides power to various vehicle accessories, such as the vehicle radio, lights and other electrically operated equipment not powered by the hybrid powertrain battery. The charge level（充電状態）of the vehicle batteries is monitored（検出、監視、把握）according to an index known as the battery State of Charge, or SOC. The SOC is defined by a ratio of the amount of residual charge（残量）remaining in a battery relative to its full charge capacity. Presently（現在）, a battery's SOC may be measured using a combination of a measurement method utilizing a correlation between SOC and a battery's voltage-current characteristics at the time of（時）charging (or discharging) and a measurement method utilizing an accumulation of charged and discharged amounts.

In many hybrid vehicles, a battery control system controls charging (and discharging) of a battery based on the SOC. A limitation（欠点）of many hybrid battery control systems is that they fail to（できない）manage the lower voltage battery's charge level as（する時、しつつ、しながら）it supplies power to the vehicle accessories, particularly when the internal combustion engine is turned off. Failure to manage the lower voltage battery may result in the battery becoming depleted（消耗、劣化）. Accordingly, a need exists for（必要）an improved battery control system for a hybrid vehicle that monitors and controls a charged state of the lower voltage vehicle accessory battery to prevent the battery from becoming depleted.