Leyland at ahead
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LEYLAND is forging ahead in the fuel economy race to produce the first — viable — continuously variable transmission (cvt) specifically for commercial vehicles.
The Leyland cvt project, which began in 1979, is now almost ready to move into the fleet trial stage.
A paper describing the company's work to date on a flywheel-based regenerative braking system combined with the cvt will be presented in Paris at the end of September. The venue is a conference organised by the SIA (Societedes des Ingenieurs de Automobiles), The French equivalent of the Institution of Mechanical Engineers' Automobile Division.
Fleet trials of Leyland National single-deck buses equipped with the system are expected to begin in Britain soon afterwards.
Several other commercial vehicle and car manufacturers are currently engaged in development work on continuously variable transmissions of various types.
The concept of a gearbox with no discrete ratios but a continuously variable input/ output ratio improves fuel economy by allowing the engine to operate constantly in a very narrow speed range.
Leyland's work with a prototype National bus fitted with its cvt combined with regenerative braking has shown fuel consumption gains of as much as 30 per cent over a conventional National.
The Leyland oft is of the traction variator type which employs discs and rollers separated by an oil film through which the drive is transmitted. There is no physical contact between the discs and rollers and the specially formulated oil which separates them is subjected to exceptionally high pressure.
The cvt's microprocessorbased controller is housed in the standard Leyland automatic transmission control box but is a lot more complex than any conventional automatic transmission control.
Whereas a standard controller has to decide only whether to change up, change down or do nothing, the eves microprocessor has the job of providing continuous control of the driveline.