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Allison Transmission Takes Stake in Torotrak, Licenses Full-Toroidal Traction-Drive Transmission Technology

The Torotrak variator, which affects the speed of rotation of the sun gear and is responsible for the smooth variation of ratios. Click to enlarge.

Allison Transmission, Inc., a leading designer, manufacturer and supplier of medium- and heavy-duty automatic gearboxes for the commercial vehicle sector, has entered a global licensing agreement with Torotrak plc, a full-toroidal traction-drive transmission company.

The new partnership gives Allison access to Torotrak’s specialist design and development skills covering Infinitely Variable Transmissions (IVTs) and Continuously Variable Transmissions (CVTs). The UK company’s technology offers significant opportunities for efficiency gains, fuel savings and emission reductions, together with a seamless, refined drive experience. Development work on a new medium-duty truck transmission will commence immediately with Torotrak supporting Allison in the program under a separate engineering agreement.

Allison has purchased initial licence rights valued at approximately £8.44 million (US$11.8 million) of which approximately £4.69 million (US$6.56 million) has already been paid, coincident with signing the agreement, and a further £3.75 million will be paid in 2010. Additionally, Allison has secured options to purchase, at a future date, a non-exclusive licence of Torotrak’s technology for applications in large commercial vehicles and a further option to secure worldwide exclusivity (except for Torotrak’s existing licensees in this field) across the commercial vehicle market.

Under the agreement, Allison will also take an approximate 10% equity stake in UK-based Torotrak for £2.4 million (US$3.35 million). Torotrak’s Chief Executive, Dick Elsy, described it as a landmark deal for the company and said the news would help to lift some of the gloom surrounding the British automotive industry, currently deep in recession.

Allison’s equity stake, coupled with initial licence payments, involves an immediate cash injection of £7.1m (US$9.93 million). Allison has gained licence rights to Torotrak’s transmission technology as well as options over global manufacturing and sales exclusivity in the small to medium truck and bus market, with similar options relating to large trucks and buses at a later date. The total value of the licence fees to be paid to Torotrak under the agreement, should Allison take up all of the licensing and exclusivity options on offer, will be in the region of £18 million to £28 million (US$25.17 million to $39.16 million); additionally, royalty payments will be made to Torotrak for every Allison transmission sold under the new arrangement.

The total deal, the largest yet secured by Torotrak, opens up major new markets for the company’s technology in the truck and bus sectors—currently experiencing a clear upturn in demand for gear shift automation—and builds on agreements already concluded with Tata Motors Ltd and a major unnamed European truck manufacturer.

Generic simplified layshaft layout of the Torotrak IVT. A coaxial layout is also possible. Click to enlarge.

A Torotrak transmission provides the ratio range not through a system of gears, as found in a conventional automatic transmission, but by a full-toroidal variator which consists of a set of discs and rollers. The IVT is torque-controlled rather than ratio controlled. The software determines the torque required at the road wheels and then requests torque from the transmission rather than setting a specific ratio. The engine can then be used to deliver the power at its most efficient operating point. In conventional automatics where the gear ratios are fixed the engine only runs at its most efficient operating points for short periods of time.

Cross-section of a pre-production IVT for a light-duty RWD vehicle. Click to enlarge.

In a conventional Torotrak full toroidal variator consisting of two cavities, each of the six rollers (three for each cavity) is connected via a mechanical linkage to its own hydraulically controlled piston. The six mechanical linkages comprise a carriage to support the roller, a spherical joint to allow the necessary degrees of freedom to articulate the roller, a pivoted lever to alter the applied force direction and a piston and stem to apply the force.

The fulcrum pins for each pivoted lever are housed in a fulcrum plate above the hydraulic block. In turn, this block houses the six pistons that are subjected to hydraulic pressure used to apply force to the rollers.

As each roller is independently controlled, each one shares the load equally since the geometrical differences and tolerances between roller mechanisms simply result in a different piston position that the hydraulic system is insensitive to.

The Torotrak ERC. Click to enlarge.

Torotrak more recently developed an Epicycloidal Roller Control (ERC) for its IVT. The ERC concept simplifies the conventional arrangement by linking the six traction rollers together with a single mechanism and hydraulic piston. The basic structure of the mechanism takes the form of an epicyclic gear-train comprising of a sun gear, an annulus gear and planet roller assemblies. Each roller is mounted on and steered by a planet roller; the teeth of the sun and annulus gears mesh with the teeth of each planet roller to position them around the toroid.

Use of the ERC improves efficiency while improving the overall cost, weight and package of the transmission, according to Torotrak. The ERC concept reduces the parts count within the variator by 30%, resulting in an approximate variator cost reduction of around 20%. Replacement of the individual hydraulic roller control system produces significant package and weight savings. In a rear wheel drive IVT, use of the ERC can reduce transmission length by 5%, package volume by 20% and increase overall efficiency by around 10%, according to the company.

Torotrak’s strategy remains focused on the four key markets of: Commercial Vehicles; Outdoor Power Equipment (“OPE”); Off-Highway; and Automotive. The Company has now entered into substantial exclusivity arrangements in two of its markets which provide access to significant volume potential—in OPE through the joint venture with MTD Holdings (earlier post) and in Commercial Vehicles (truck and bus and now including most military vehicles) through the new agreement with Allison and the existing agreement with a European Truck and Bus manufacturer, the identity of which remains undisclosed (earlier post).

Torotrak can now focus its business development strategy on maximizing potential in its other two markets—Off-Highway and Automotive as well as looking at ways to access new markets and to realize further potential through new developments such as auxiliary drives and Kinetic Energy Recovery Systems (earlier post).

Allison, formerly a division of General Motors Corporation, was acquired by affiliates of The Carlyle Group and Onex Corporation in August, 2007.




If this can find application in a front wheel drive transmission, it would have to be a big thing for electric/hybrid and any combustion engine.

Potential to optimising fuel economy and solve electric motor /transmission incomatibility issues. Very good to see some smart money finding the mark.

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