PURPOSE: To make a variable speed pulley turn into an unlubricated system, by covering a free end of a sleeve with a sliding surface side cylinder for sealing, and sealing lubricating oil in the space formed between the cylinder and the sleeve, in case of the variable speed pulley for a belt continuously variable transmission.

CONSTITUTION: An outer circumferential sliding surface of a sleeve 11 where a fixed pulley 14 is tightly installed is surrounded and sealed by a cylinder 16 of a sliding pulley 18, while lubricating oil 30 is sealed in first and second spaces 40, 15, a cylindrical keyway 16b, a spiral groove 16c and a ring groove 16d to be formed between both, and the space 15 is interconnected to the outside air. And, when rotation of a variable speed pulley is started, the lubricating oil 30 is dispersed over the keyway 16c, lubricating sliding surfaces 11a and 16a all the time. And, with slide motion of the sliding pulley 18, these spaces 15 and 40 formed of the sleeve 11 and the cylinder 16 expand or contract, but since the space 15 is interconnected to the outside air, large pressure is not added to the lubricating oil so that a leakage of the lubricating oil comes to zero owing to a seal of the cylinder 16. Thus, the reliability in the variable speed pulley is improved and, what is more, it comes to an unlubricated system.