Drive unit for a seat belt pretensioner

The invention relates to a drive unit for a safety belt tightener, which has a drive that can be triggered upon activation of an acceleration sensor and can be rigidly coupled to the belt take-up roller. The drive is located in a drive chamber (10) which is formed by two plates (12) running parallel to each other and provided with a coating material (16) and which has a drive band (20), at least one end of which is fastened to a drive shaft (18).