Patent ID: 7037225

Claim:
An automatic V-belt transmission comprising: a drive pulley; a driven pulley; and a V-belt extending between the drive pulley and the driven pulley, wherein the drive pulley has: a fixed sheave which is rigidly fixed to a drive shaft of the drive pulley; and a movable sheave which is movable on the drive shaft in a direction of an axis of the drive shaft, wherein each of the fixed sheave and the movable sheave includes a conical pressure surface having an inclined angle with respect to a surface perpendicular to the axis of the drive shaft, respectively, and the conical pressure surface of the fixed sheave and the conical pressure surface of the movable sheave form a V-shaped groove of the drive pulley, which opens radially outwardly, in which the movable sheave is moved toward the fixed sheave by a propulsion generating mechanism for the drive pulley as rotational speed of the drive shaft increases, so that radius of contact of the drive pulley with the V-belt increases, wherein the conical pressure surface of one of the fixed sheave and the movable sheave is formed to have the inclined angle being constant from a radially inner part of the conical pressure surface to a radially outer part of the conical pressure surface, and wherein the conical pressure surface of the other of the fixed sheave and the movable sheave is formed to have an angular turning boundary that the inclined angle varies thereon, in which the inclined angle of a radially inner part inside the angular turning boundary of the conical pressure surface is smaller than the inclined angle of a radially outer part outside the angular turning boundary of the conical pressure surface, and in which an angular difference between the radially inner part of the conical pressure surface and a side edge surface of the V-belt is greater than an angular difference between the radially outer part of the conical pressure surface and the side edge surface of the V-belt.