A belt tensioner for a belt drive

The invention discloses a belt tensioner for a belt drive of a motor vehicle engine. The belt tensioner comprises: a fixed part (2) configured to be fixed with respect to the engine and provided with a pivot (7) defining a rotation axis (A); an arm (3) having a connection portion (10) hinged to the pivot (7) and rotatable about the rotation axis (A) and an opposite portion (42) rotatably supporting a pulley (4) configured to cooperate with a belt of the drive; a main spring (5) interposed between the fixed part (2) and the arm (3) to exert thrust on the arm (3) such as to rotate said arm towards the belt; and at least one rolling bearing (14, 15) interposed between the arm (3) and the pivot (7) to support the arm (3) and ensure the alignment thereof. 种用于机动车辆发动机的带驱动装置的带张紧器，其包括：固定件(2)，被配置为相对于发动机固定，并且设有限定旋转轴线(A)的枢轴(7)；臂(3)，具有连接部(10)和相反部(42)，连接部(10)铰接到枢轴(7)并且可围绕旋转轴线旋转，相反部(42)可旋转地支撑被配置为与驱动装置的带配合的带轮(4)；主弹簧(5)，插在固定件(2)与臂(3)之间，以对所述臂(3)施加推力，以便使所述臂朝带旋转；以及至少个滚动轴承(14,15)，插在臂(3)与枢轴(7)之间，以支撑臂(3)并且确保其对准。