車載用バッテリーケースのインパクト加工における欠陥発生メカニズムとその改善

抄録

The cases of the Li-ion batteries mouthed in EV (Electric Vehicles) and FCV (Fuel Cell Vehicles) are conventionally produced by multistage deep drawing. This forming process requires a large number of stages and is expensive. In this study, cold backward (impact extrusion) was adopted since it has very high productivity comparing to conventional process. However, the defects, such as cracks, distortion and uneven thickness will arise in produced cases. The generation mechanism and how to deal with those defects were investigated in this paper. From the experimental results, it was assumed that bending and twisting elastic deformation of dies are cause of the defects. It was found that the case of the deformation is in the heterogeneity state of the lubrication. The punch bottom geometry which can minimize the influence the heterogeneity of the lubrication in the last phase of forming was investigated. In order to reduce the wear of lubricant at high reduction of area, lubricant and surface treatment were also investigated.