Engineering News
Page 17
If you've noticed an error in this article please click here to report it so we can fix it.
Renault research
RVI's electronically controlled mechanical transmission (CM June 30) is now at an advanced development stage, but there are no plans yet for putting it into production.
RVI's current research and development projects also include a microprocessor controlled power-shift twin-layshaft gearbox; composite leaf springs made from glass fibres and epoxy resin, developed jointly with GKN; and thermal insulation of engines.
At a preview of its exhibits the Paris Show, which include a 6x2 R310 with trailing axle and a high-roof cab for the G260, and which will be described in CM next week, Renault Vehicules Industriels had R310 tractive units fitted with the development transmissions on display.
The OPT (optimised power train) gearbox, as RVI calls its microprocessor controlled mechanical gearbox, is based on the 89, nine-speed rangechange unit but without its usual synchromesh. Like Eaton's AMT (automated mechanical transmission), described in CM July 21, the OPT has no manual clutch control. A selector panel with two levers, mounted on top of the conventional gear lever on the development vehicles, allows the driver to choose between automatic and semi-automatic mode.
In semi-automatic mode the new RVI transmission is similar to Scania's CAG (computer aided gears shifting) system in that a short toggle switch is used to shift gear while the microprocessor always protects the engine and transmission by preventing too low a gear from being engaged.
In full automatic mode the microprocessor does all the work, selecting the appropriate gear and signalling the air valves mounted on top of the gearbox to make the appropriate shift.
A novelty of the RVI control is that it allows the driver to select "maxi regime" or "maxi couple". The first position gives upshifts at maximum engine power, for hill climbing or good acceleration, for example, while in the second position the microprocessor will signal gearshifts at the engine's maximum torque speed and thus achieve good fuel economy.