Variator development boosts supercharging and aux drives14 December 2015

Torotrak last week unveiled developments of its variator traction drive technology aimed at delivering low-cost, high-efficiency drive systems.

Shown at the Berlin CTI symposium, the equipment is designed to boost the appeal of variable-speed supercharging and auxiliary drives, according to design engineer Chris Gaskell (pictured).

These developments, he says, will allow Torotrak’s V-Charge variable supercharging technology to compete with the latest boosting solutions, and without their integration challenges.

Gaskell says it’s all about two new proprietary technologies, dubbed PitchSteer and DriveDisconnect.

PitchSteer is a low-cost, low weight method of control that reduces actuation power required (to 10W) for Torotrak’s variable drive, which is designed for devices such as superchargers.

DriveDisconnect provides a zero output speed capability within the variator – providing the functionality of a clutch without the cost or weight penalty.

“In a main-drive transmission application we typically control variator torque by modulating hydraulic pressure,” explains Gaskell

“Most likely there are other devices requiring hydraulics in the transmission, such as clutches, and so this is no problem,” he continues.

“However, for a small auxiliary drive this is not the case and we need to strip out all the cost we can,” he adds.

Torotrak has validated PitchSteer in one of its V-Charge supercharger units with a variator ratio range of 10, and it achieved a full sweep ratio change in just 300 msec.

Gaskell also points out that, in addition to minimising actuation power, the wide ratio range capability allows the driven device to be reduced to a very low speed relative to the input if the function is not required, meaning parasitic losses are minimised.

Meanwhile, DriveDisconnect further reduces parasitic losses by disconnecting the variator output when a driven device is not required, he continues.

Since it is an integral function of the variator, DriveDisconnect does not add weight or cost – unlike conventional electromagnetic clutches, which can add 3kg and around eur 30 to the cost of an auxiliary drive, even in high volume automotive production.

“DriveDisconnect provides an extra function for free,” enthuses Gaskell.

“Our development work for both technologies has proven that we can offer unique CVT functionality that addresses the needs of our customers, for example in the variable supercharging space.”

Brian Tinham

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Torotrak (Development) Ltd

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