Up to a certain time, a continuously variable kinetic transmission was very difficult to implement. The main reasons for this were the high structural complexity and low reliability of the unit, but this problem became easily solved with the advent of the first variators.
The standard transmission of rotary motion is carried out by means of a flexible friction element mounted on two movable shafts. The ratio of revolutions of the driven shaft to the driving shaft, called the gear ratio, in such a transmission is always fixed and cannot be changed without completely stopping the mechanism. At the same time, in some cases, it is required to smoothly change the number of revolutions as the rotation speed increases, when the potential energy of the moving working body becomes so high that the maximum power of the power unit is no longer required to maintain movement, but there is a need for high torque.
If in standard V-belt and chain drives the shafts are made in the form of pulleys or gear stars with a fixed size, then in the variator the movement is transmitted between two conical shafts. When the implement is stationary, the variator belt is located in the narrow part of the drive and in the wide part of the driven cones, thereby achieving the highest gear ratio with low torque, which allows the working element to be moved while at rest. With an increase in the speed of movement, the belt or shafts are displaced, due to which the gear ratio drops, and the rotational speed of the driven shaft increases. The reverse process occurs when the speed of the working body decreases. Modern variators are distinguished by their design perfection, which allows for excellent dynamics of the gear ratio change, in which switching between the minimum and maximum speed thresholds is carried out in tenths of a second.
The mechanism that changes the gear ratio in the variator can be based on different principles of operation. The simplest and most reliable is a device that uses a centrifugal brake located inside the cone of the driven shaft. In this case, the flexible friction element is fixed by means of damping rollers, which allows it not to move after the movable shaft. Also actively used are systems of adjustable hinges, driven by an actuator that displaces either the belt or one or both movable shafts. The degree of displacement depends on the current readings of the tachometer, while the operating mode remains fully automatic. This design of the variator provides it with the best performance. In stationary installations, the operating mode of the variator is often regulated by a mechanism with a complex system of servo drives under program control.