Variable-speed V-belt drive for vehicle

摘要

A variable-speed V-belt drive includes: a drive pulley; a driven pulley including a fixed sheave with a cylindrical shaft and a movable sheave mounted on the cylindrical shaft so that the movable sheave can rotate and axially move; a V belt extended between the drive and driven pulleys; and a pressure mechanism of applying pressure to the movable sheave of the driven pulley. The pressure mechanism includes a helical cam groove formed in one of the cylindrical shaft and the movable sheave of the driven pulley, and a roller mounted on other of the cylindrical shaft and the movable sheave of the driven pulley so that the roller engages with the cam groove. The cam groove has opposite first and second working surfaces. The second working surface has a retaining surface of retaining the roller thereon when the vehicle travels in the engine-braking mode. The variable-speed V-belt drive can maintain the effect of engine brake at a high level even when traveling down a steep hill.