Scania changes automatically
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EXCLUSIVE by Toby Clark • Scania has launched Opticruise, an electronically controlled automatic gearchange system. Like alternatives from Volvo and ZF, it marries computerised engine control to a conventional gearbox, but it retains a pedal-operated clutch for starting and stopping.
The system is intended to make driving easier and to reduce gearbox wear and fuel consumption, and it links the operation of the engine and gearbox with that of the exhaust brake and retarder. Field tests of over a hundred vehicles are being carried out, which will shape the final configuration of the system when it reaches the market.
The Opticruise system is based on a standard synchromesh gearbox and clutch, but gear actuation is performed by a pair of pneumatic cylinders, and in most circumstances gear changes take place without using the clutch at all. Opticruise uses Scania's EDC control system to synchronise the engine's speed with that of the gearbox, overriding the throttle setting—this minimises shift force, reducing gearbox wear and obviating the need for a shift damper.
The conventional clutch is used only for starting from rest, when coming to a stop and shunting—a display on the dashboard indicates when it is required. Scania has decided that a manual system provides more precision in lowspeed manoeuvring, though it has not discounted an automated clutch for future versions.
Normal driving is accomplished in Manual (M) or Automatic (A) mode, controlled by a "gear lever" which also has Neutral (N) and Reverse (R) positions. In Manual mode, single or block changes are possible without using the clutch; in Automatic mode a left or right movement of the lever moves the truck down or up a gear, or can be used to set the starting gear.
Automatic upshifts are set to maximise fuel consumption and minimise noise, usually occurring at around 1,700rpm, but kickdown—flooring the throttle—moves the shift point up to about 1,900rpm. Alternatively, engaging the Hill switch has the same effect, and allows extra fuel to be injected when a particularly rapid upshift is required.
The most notable feature of the Scania system could be the
way in which it integrates gearbox operation with cruise control, engine and exhaust braking and the retarder: in retarder mode, for example, a light touch on the footbrake at the desired downhill speed brings the exhaust brake and retarder into play. Meanwhile, downshift points are
adjusted to avoid overheating the engine or retarder coolant.
Alternatively, a button on the floor activates the exhaust brake and sets downshifts to occur at around 2,300rpm,
See CM next week for our Opticruise driving impressions.