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Dana Rexroth introduces HVT R3 powersplit transmission; up to 20% fuel savings in off-road applications

Hvt
Combustion engine driving the input shaft of the HVT. The upper hydrostatic and lower mechanical path can be seen inside the HVT, which transmit power separately or in combination. The power is combined on the output side in a summation gear train and made available to the drive shaft. Click to enlarge.

At INTERMAT 2012, Dana Rexroth Transmission Systems unveiled the R3 hydromechanical variable transmission (HVT), the first powersplit system resulting from the 50-50 joint venture between Dana and Bosch Rexroth AG announced in 2010 and completed last year.

The HVT combines the advantages of the mechanical travel drive with torque converter—high efficiency at high speeds, maximum torque at standstill—with those of the hydrostatic travel drive: wearless reversing, high tractive force at low engine speed, good response, and a high degree of freedom regarding power management. The HVT allows drive characteristics to be adjusted over the entire speed range, enabling optimal handling and the highest possible throughput with maximum fuel savings, according to the company.

Initial tests on front end loaders with the new HVT powersplit systems demonstrate fuel savings in the drivetrain of up to 20% when compared with the same vehicle outfitted with a conventional torque converter transmission.

At low vehicle speeds, only the hydrostatic circuit of the HVT is used, allowing for quick acceleration and braking, precise low-speed maneuvering, and reverse without the need of an additional clutch.

As the speed of the vehicle increases, the HVT still employs the hydrostatic path, but a power splitter begins to route engine power through a parallel path that uses the mechanical elements of the HVT. This configuration enables vehicle acceleration with no interruption in tractive force.

Components and operation of the HVT R3.

The HVT optimizes the operating point of the diesel engine by decoupling engine speed from drive speed, and maintenance costs are reduced by utilizing hydrostatic braking and wear-free directional reversals.

The HVT system helps reduce complexity for equipment manufacturers, since the entire system of gears and hydrostatics is managed by an advanced electronic control unit (ECU) and optimized for efficiency by a single supplier.

The Dana Rexroth HVT R3 occupies the same space within the design envelope as conventional torque converter transmissions while allowing for engine downsizing.

The first in a series of HVTs, the R3 is currently undergoing field testing in numerous OEM prototype vehicles. HVTs are designed for front end loaders, graders, forestry skidders, and other off-highway applications requiring up to 265 kW (360 hp).

Dana Rexroth develops and manufactures hydromechanical variable transmission (HVT) systems that combine Dana’s expertise in off-highway transmission engineering and manufacturing with Bosch Rexroth’s deep experience in hydraulics and systems.

Dana Rexroth Transmission Systems is based in Arco, Italy.

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