Agritechnica Gold Medal for new Traction System
An Agritechnica Innovation Gold medal is conferred on an innovation demonstrating a new concept in which the functionality has changed decisively and gives rise to a new process or marks a substantial improvement to an existing process.
Key criteria:
- Practical significance at farm level
- Operating profitability and efficiency benefits
- Improvement on the environment and energy consumption.
- Work load reduction and improved health and safety
In order to avoid tension in the drivetrain of all-wheel-drive vehicles when cornering, the differences in speed between the front and rear axles or between the two wheels on an axle must be balanced. Differentials are most widespread today, whereas hydrostatic or electric individual wheel drives are only used in isolated cases as alternatives in self-propelled agricultural machinery or are still in the prototype stage. If slip occurs, the wheel speeds have to be reduced or even synchronised completely. Differential locks, in particular, therefore effectively compel the vehicle to drive straight ahead. Consequently, they do not support the driver on difficult terrain or in complicated driving situations and are also often difficult to operate.
With ‘Line Traction’, Müller Landmaschinen is presenting a completely new drive concept for the Aebi Terratrac slope tractor. This has been developed together with Müller Landmaschinen and evolved to series production maturity. Line Traction not only enables the longitudinal differential that is commonly found on such vehicles for equalising the speed between the two drive axles to be forgone, but also the transverse differentials, which ensure speed equalisation between the wheels on one axle.
The drive shafts of all four wheels are therefore always at the same speed. The wheel speed is only adjusted in the downstream planetary final drives. This is where the power flows from the sun gear to the wheel hub via the planet carrier. Unlike conventional final drives, however, the ring gear in the Line Traction drive is not permanently connected to the axle housing, but is supported hydrostatically by an outboard cam plate and radial pistons. If the Aebi Terratrac travels through a curve, the proportional valves integrated into the hydrostatic circuits (one per wheel) can be specifically opened, resulting in the controlled counter-rotation of the ring gears. This in turn results in a reduction in the speed of the planet carrier and therefore the wheel speeds. The outer wheel always assumes the role of the ‘master’ in this case, which means that the hydrostatic system completely fixes the ring gear in position. At the other wheels (‘slaves’), which travel shorter distances, the proportional valves are opened until the respective nominal speeds are achieved depending on the steering angle and speed. Practical advantages: each wheel is always driven at the correct speed, even during cornering.
The Line Traction drive system therefore not only improves traction and reduces damage to the turf, but also and in particular increases safety during turning manoeuvres on slopes, in which the locks would have to be disengaged in classic drive concepts with differentials.
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