Variable speed engine accessory flat belt drive system

Abstract

Variable speed operation for the accessories of a prime mover (such as an engine) is obtained by a flat belt coupling a variable diameter flat belt driving pulley to flat belt pulleys attached to each of the accessories. The variable diameter pulley assembly includes a shaft and a pair of pulley sheaves each having a pair of relatively movable guideway disks lying alongside each other. Inner and outer guideway disks of each pair include, respectively, first and second series of spiral guideways extending in opposite directions such that the guideway intersections locate bearing ends of a circumferential array of belt engaging elements extending between the pulley sheaves. Thus, mutual angular change between the guideway disks causes corresponding change in the effective diameter of the pulley assembly. In one embodiment, an integral speed responsive actuator assembly is incorporated into the pulley assembly and includes a housing with two pairs of variable volume fluid chambers and a pair of mirror image speed responsive valves which direct hydraulic fluid under pressure into one or the other of the chambers of each pair to obtain relative movement of a wall separating the chambers, which relative movement can be coupled to the guideway disk sets to change the effective diameter of the pulley assembly.