Importance

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Abstract

A belt-type continuously variable transfer system (15) includes a driving pulley assembly (20), a driven pulley assembly (22) and a V-shaped belt (24) engaged to transfer rotary power therebetween. The driven pulley assembly (22) can include a ratio adjustment mechanism (46) that adjusts the position of a rear sheave (40) relative to a forward sheave (42). The adjustment mechanism (46) includes a motor (170) and a worm gear mechanism (171, 172) that rotates an actuation screw (154). Rotation of the actuation screw (154) is reacted by a split nut (158) so that as the screw (154) rotates is translated along the axis (B) of the driven pulley assembly (22). Translation of the actuation screw (154) exerts pressure against the rear sheave (40) to push it toward the forward sheave (42), thereby altering the drive ratio of the pulley assembly. In one feature, the driven pulley assembly (22) includes a fail-safe mechanism (48) that operates when power is supplied to the motor (170) to hold the split nut (158) together. Once power is disrupted, the fail-safe mechanism (48) allows the components (158a-c) of the split nut (158) to be separated, disrupting the threaded engagement with the actuation screw (154). At this point, the actuation screw (154) is driven forward by a compression spring (190), thereby driving the rear sheave (40) forward to a predetermined drive ratio position. In another aspect of the invention, the driving pulley assembly (20) includes an idler pulley portion (65) radially inboard from the normal driving sheave surface (29, 31).

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First Claim