1. Field of the Invention
The present invention relates to a technique to protect a plurality of cells included in a battery module, at the time of a vehicle collision.
2. Description of Related Art
A hybrid vehicle and an electric vehicle are provided with a battery module for accumulating electric power to be supplied to a vehicle drive motor. The battery module is provided with a protection structure for protecting a battery from an impact at the time of a vehicle collision. Japanese Patent Application Publication No. 2003-45392 (JP 2003-45392 A) describes a holder configured to radially sandwich and hold a plurality of cylindrical cells of which electrode terminals are placed on the same plane.
However, when the holder is fixed in a state where one side surface of the holder entirely makes contact with a wall surface of a vehicle structure, the cylindrical batteries might be deformed at the time of a vehicle collision. This point will be described below with reference to FIG. 7. FIG. 7 is a schematic sectional view of a battery module, and illustrates a behavior of the battery module at the time of a vehicle collision. Note that an arrow F indicates a direction where a load is applied.
When a load F is applied to a holder 201, the holder 201 is pushed toward a wall surface P. Since no gap is formed between the holder 201 and the wall surface P, the holder 201 is crushed by the load F and an excessive compressive load may be applied to cells 202. Further, if the holder 201 breaks due to the load F right above the cell 202, a protruding portion formed in a broken part may make point contact with the cell 202. This may cause an excessive compressive to be applied to the cell 202.