Continuously Variable Transmission - History

History

Leonardo da Vinci, in 1490, conceptualized a stepless continuously variable transmission. Milton Reeves invented a variable speed transmission for saw milling in 1879, which he applied to his first car in 1896. The first patent for a friction-based belt CVT for a car was filed in Europe by Daimler and Benz in 1886, and a US Patent for a toroidal CVT was granted in 1935.

In 1910, Zenith Motorcycles built a V-twin engined motorcycle with the Gradua-Gear, which was a CVT. In 1912, the British motorcycle manufacturer Rudge-Whitworth built the Rudge Multigear. The Multi was a much improved version of Zenith’s Gradua-Gear.

An early application of CVT was in the British Clyno car, introduced in 1923.

A CVT, called Variomatic, was designed and built by Hub van Doorne, co-founder of Van Doorne's Automobiel Fabriek (DAF), in the late 1950s, specifically to produce an automatic transmission for a small, affordable car. The first DAF car using van Doorne's CVT, the DAF 600, was produced in 1958. Van Doorne's patents were later transferred to a company called VDT (Van Doorne Transmissie B.V.) when the passenger car division was sold to Volvo in 1975; its CVT was used in the Volvo 340. In 1995, VDT was acquired by Robert Bosch GmbH.

Many snowmobiles use a rubber belt CVT. In 1974, Rokon offered a motorcycle with a rubber belt CVT.

CVTs are used in some all terrain vehicles. The first ATV equipped with CVT was Polaris's Trail Boss in 1985.

In early 1987, Subaru launched the Justy in Tokyo with an electronically controlled continuously variable transmission (ECVT) developed by Fuji Heavy Industries, which owns Subaru. In 1989 the Justy became the first production car in the U.S. to offer CVT technology. While the Justy saw only limited success, Subaru continues to use CVT in its kei cars to this day, while also supplying it to other manufacturers. Subaru offers CVT on the 2010 Legacy and 2010 Outback (Lineartronic).

In the summer of 1987 the Ford Fiesta and Fiat Uno became the first mainstream European cars to be equipped with steel-belted CVT (as opposed to the less robust rubber-belted DAF design). This CVT, the Ford CTX was developed by Ford, Van Doorne, and Fiat, with work on the transmission starting in 1976.

The 1992 Nissan March contained Nissan's N-CVT based on the Fuji Heavy Industries ECVT. In the late 1990s, Nissan designed its own CVT that allowed for higher torque and included a torque converter. This gearbox was used in a number of Japanese-market models. Nissan is also the only car maker to bring a roller-based CVT to the market in recent years. Their toroidal CVT, named the Extroid, was available in the Japanese market Y34 Nissan Gloria and V35 Skyline GT-8. However, the gearbox was not carried over when the Cedric/Gloria was replaced by the Nissan Fuga in 2004. The Nissan Murano, introduced in 2003, and the Nissan Rogue, introduced in 2007, also use CVT in their automatic transmission models. In a Nissan Press Release, 12 July 2006, Nissan announced a huge shift to CVT transmissions when they selected their XTronic CVT technology for all automatic versions of the Versa, Cube, Sentra, Altima and Maxima vehicles in North America, making the CVT a mainstream transmission system. One major motivator for Nissan to make a switch to CVTs was as a part of their 'Green Program 2010' aimed at reducing CO2 emissions by 2010. The CVT found in Nissan’s Maxima, Murano and the V6 version of the Altima is considered to be the worlds first "3.5L class" belt CVT and can hold much higher torque loads than other belt CVTs.

After studying pulley-based CVT for years, Honda also introduced their own version on the 1995 Honda Civic VTi. Dubbed Honda Multi Matic, this CVT gearbox accepted higher torque than traditional pulley CVTs, and also includes a torque converter for "creep" action. The CVT is also currently employed in the Honda City ZX that is manufactured in India and Honda City Vario manufactured in Pakistan.

In 1996, Fendt, a Germany-based tractor manufacturer, released the first ever heavy duty tractor to be equipped with a hydrostatic type CVT with the Fendt Vario 926. A year later Fendt was acquired by AGCO Corporation which expanded the use of the transmission to the Challenger Tractor, Massey Ferguson, and TerraGator brands of machinery, which are also owned by AGCO. Well over 100,000 agricultural tractors have been manufactured with this transmission design.

Toyota used a Power Split Transmission (PST) in the 1997 Prius, and all subsequent Toyota and Lexus hybrids sold internationally continue to use the system (marketed under the Hybrid Synergy Drive name). The HSD is also referred to as an Electronically controlled Continuously variable Transmission. The PST allows either the electric motor or the internal combustion engine (ICE) or both to propel the vehicle. In ICE-only mode, part of the engine's power is mechanically coupled to the drivetrain, with the other part going through a generator and a motor. The amount of power being channeled through the electrical path determine the effective gear ratio. Toyota also offers a non-hybrid CVT called Multidrive for models such as Avensis.

Audi has, since 2000, offered a chain-type CVT (multitronic) as an option on some of its larger-engine models, for example the A4 3.0 L V6.

Fiat in 2000 offered a Cone-type CVT as an option on its hit model Fiat Punto (16v 80 PS ELX,Sporting) and Lancia Y (1.2 16V).

BMW used a belt-drive CVT (manufactured by ZF Friedrichshafen) as an option for the low- and middle-range MINI in 2001, forsaking it only on the supercharged version of the car where the increased torque levels demanded a conventional automatic gearbox. The CVT could also be manually "shifted" if desired with software-simulated shift points.

MG-Rover used an identical ZF CVT transmission on its Rover 45 and MG ZS models.

GM introduced its version of CVT known as VTi in 2002. It was used in the Saturn Vue and Saturn Ion models.

Ford introduced a chain-driven CVT known as the CFT30 in their 2005 Ford Freestyle, Ford Five Hundred and Mercury Montego. The transmission was designed in cooperation with German automotive supplier ZF Friedrichshafen and was produced in Batavia, Ohio at Batavia Transmissions LLC (a subsidiary of Ford Motor Company) until 22 March 2007. The Batavia plant also produced the belt-driven CFT23 CVT which went in the Ford Focus C-MAX. Ford also sold Escort and Orion models in Europe with CVTs in the 1980s and 1990s.

Contract agreements were established in 2005 between MTD Products and Torotrak for the first full toroidal system to be manufactured for outdoor power equipment such as jet skis, ski-mobiles and ride-on mowers.

The 2007 Dodge Caliber and the related Jeep Compass and Jeep Patriot employ a CVT using a variable pulley system as their optional automatic transmission.

The 2008 Mitsubishi Lancer model is available with CVT transmission as the automatic transmission. DE and ES models receive a standard CVT with Drive and Low gears; the GTS model is equipped with a standard Drive and also a Sportronic mode that allows the driver to use 6 different preset gear ratios (either with the shifter or steering wheel-mounted paddle shifters).

The 2009 SEAT Exeo is available with a CVT automatic transmission (multitronic) as an option for the 2.0 TSI 200 hp (149 kW) petrol engine, with selectable 'six-speeds'.

In 2010, the US Patent Office issued patent number 7,647,768 B1 for a series of hydraulic Torque Converters that use hydraulic friction rather than mechanical friction as a CVT.

Suzuki has used CVT since 2010 on their SX4 and Kizashi models.

Read more about this topic:  Continuously Variable Transmission

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