iCVT Operation
In simplified terms the iCVT can be compared to a sprocket and chain set. The ratio changing happens when the sprocket gets an extra tooth or loses a tooth thus changing the circumference of the chain around the centre of the conical disc. See picture and description below.

The Positive Drive
The positive drive is achieved (Referring to the picture below) by the chain as it leaves the lower idler,bends the chain in the opposite direction and hooks onto and locks (due to the type and design of the chain links) onto the drive bars in the slots on the conical discs.These drive bars are designed to slide in the slots of the conical discs which are positioned exactly to allow the following:

• The chain to be in a perfect circle (due to the angle of the face of the conical discs) around the centre of the conical discs.
• The drive bars are positively locked onto by the chain.

This locking of the chain onto the drive bars is always positive as even when the drive bars traverse the chain throat (when no ratio changes can occur) there are still drive bars that are locked onto the chain as the distance between the first and last slots that the drive bars slide in, is greater than the distance between the two idler gears at the entrance and the exit of the chain throat.

The Ratio Changing
Ratio changes can only be made when the last drive bar has left the chain throat between the idlers. When the conditions for ratio changes are correct (last drive bar has left the last idler in the chain throat) the conical discs are brought together (this increasing the chain radius around the centre of the conical discs) or increasing the distance between the conical discs (thus reducing the chain radius around the centre of the conical discs). This allows the slowing down or speeding up of the conical discs.
The timing of this ratio changing is controlled by the Naudic iCVT shifter which is based on the Geneva Wheel indexing mechanism.

The image below presents a stripped view of the heart of the iCVT variator. Two opposite faced Conical disks, of which the second one is hidden in the image, provides a surface with which the Extended pins of the Chain can engage to ONLY position the Chain on a specific radius and NOT to provide any drive or power transmission.

The Chain enters and exits its loop, around the Conical disks, via two Idlers that creates a Chain Throat between them.

A Partial Drive section on each Conical disk includes radial slots that maintain the chain pitch distance between them as they radiate outwards.

A Drive Bar, with a ball end at both ends engages each slot in both Conical disks to slide in the Slots in a radial direction together with the Chain, sliding with its Extended Pins in contact with the Conical disks surface, when the Conical disks are moved closer or further away from each other in an axial direction.

Shifting the iCVT can only be done in the time duration when the Drive Bars do not traverse the Chain Throat which results in about 3/4 of a revolution of the Conical disks. During this time duration the Conical disks are moved together or away from each other in an axial direction, a distance that would result in the addition or subtraction of an integer number of chain link pitches around the circumference at which the Chain Pins are in contact with the Conical disks surfaces.

Click here to view an animation of the iCVT variator

Click here to view iCVT chain video

Below are two links to YouTube, featuring an iCVT promotional video as well as an iCVT presentation.

iCVT promotional video

iCVT presentation

A DVD containing the below iCVT promotional video as well as iCVT presentation in Powerpoint format can be obtained by sending an e-mail request on our Contact form.

A paper presented at the International CTI-Symposium – Innovative automotive Transmissions, 3 – 7 December 2007, Maritim Hotel Berlin, Germany by the company MD, Dr. Jan Naude is available for download below.