The present invention relates to a continuously variable transmission, and more particularly to a continuously variable transmission using a V-belt as a power transmission belt.
A so-called V-belt type continuously variable transmission is known and one example is disclosed in JP No. 58-174754. This known transmission comprises an electromagnetic clutch, a V-belt power transmission mechanism, a forward/reverse selector mechanism, and a differential mechanism. Torque from an engine is transmitted to the forward/reverse selector mechanism, V-belt power transmission mechanism, and differential mechanism in this order. The component parts other than the electromagnetic clutch are arranged within a single chamber defined by a casing. The V-belt type continuously variable transmission uses a V-belt. The V-belt is composed of a number of blocks, each having a frictional surface, assembled on the endless belt.
However, the V-belt type continuously variable transmission mentioned as above has a potential problem that the blocks separated from the V-belt might come into engagement with the differential mechanism should the V-belt be broken. If the differential mechanism locks owing to the blocks, the road wheels drivingly connected thereto will lock. The V-belt may be broken owing to inconvenience caused during its production or an excessively large stress which it is subject to although it is designed to possess a sufficiently long endurability. When the endless band of the V-belt is broken, the blocks are thrown away from the band. If the blocks separated from the band come into engagement with the differential mechanism, the differential mechanism locks. This causes the wheels to lock, causing the vehicle to spin. Therefore, if the V-belt is broken, not only can the vehicle not continue running, but also the vehicle becomes out of control.
An object of the present invention is to solve these problems.
More particularly, an object of the present invention is to improve the V-belt type continuously variable transmission such that even if the V-belt is broken, the differential mechanism will not lock.