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Bosch Rexroth Launches Hydraulic Flywheel, Start-Stop Technology

Posted on April 18, 2013

Bosch Rexroth has introduced a hydraulic start-stop technology that is designed to significantly improve fuel economy in construction machinery at bauma 2013.

Engine start-stop systems have become  widespread in automotive applications and Bosch Rexroth is seeking to apply it to hydraulics. The hydraulic flywheel system (HFW) builds up the required power reserve. The HFW system comprises a Bosch Rexroth axial piston pump, control block, hydraulic accumulator and control unit. The system briefly gathers energy and makes it available to the machine as needed -, to provide a boost for the diesel engine in the event of a power peak or to power a start-stop function.

The axial piston unit picks up torque at the combustion engine shaft. The hydraulic oil flow generated is fed to an accumulator, where pressure and thus the amount of stored energy increase accordingly. If the accumulator is unloaded, the axial piston unit serves as a hydraulic motor – a special characteristic of several mooring-capable Rexroth components – and converts the oil flow back into energy for the combustion engine shaft.

This is the force behind the new start-stop solution, the company said. The electronics assess whether enough pressure is available to restart the diesel aggregate once it has been switched off. If the internal combustion engine is off, the electronics evaluate the consumer’s potential energy needs. If the travel drive or work hydraulics require energy, the start-stop system immediately restarts the diesel engine with energy stored earlier on. The engine speed needed for travel and working functions is reached practically instantaneously with no time lag.

The start-stop function is also possible without the additional pump/motor unit required for the HFW approach. Here, the only prerequisite is a mooring version of the working hydraulics pump already available. This mooring pump can also serve as a hydraulic motor that can restart the diesel engine if needed.

Atlas Weyhausen has implemented the technology on its 4.4 tonne AR 60 wheel loader, which is on display at bauma 2013.