Flow sharing: efficiency for compact excavators

Bosch Rexroth has further developed the single components of the flow-sharing LUDV system, both to enhance the efficiency of compact excavators and to reduce consumptions.BOSCH REXROTH

Over the last few years, the demand for small and medium power excavators has grown on a world scale. At the same time, also the requisites imposed by customers have become more and more demanding: they expect from those vehicles manoeuvrability precision, application versatility and the lowest possible operation costs, all that with motor performances exploited in optimal way. In times characterized by high energy costs, to obtain advantageous machine tools from the economic point of view, the high efficiencies of hydraulics, coupled with long service life and high reliability of components and systems, become essential. Bosch Rexroth has further developed the single components of the flow-sharing LUDV system, both to enhance the efficiency of compact excavators and to reduce consumptions. The new LUDV flow-sharing load system couples the new RS12 valve block with a renewed version of the tested variable-displacement A7VO pump, notably increasing the productivity of compact excavators and offering a simpler and more comfortable control.

In LUDV technology, speed and direction that can be different are assigned to the single movement, solution that optimizes machining cycles. Besides, the circuit with a single variable-displacement pump reduces the number of components and then the machine production costs, all that without affecting performances. On the contrary, during the tests, one of the first 6.5 t excavators equipped with the A7VO pump has reached an output power exceeding by over 10% a similar machine without this equipment; at the same time, the fuel consumptions have decreased by 8%.

This axial-piston pump is suitable for pressures up to 350 bars. The excavator faces then easily work situations like the excavation of ditches or rotations.

The new RS12 distributor block contributes in its turn in improving performances: the internal pipes have been redesigned to reduce further the possibility of pressure drop. The four-way control system, based on a closed system, can be adapted faster to the requisites of each single application in comparison with standard six-way valves. All that reduces the development times of the new models, simplifying also notably the coordination of single components.

In the daily operation of compact excavators, it is essential that rotation and transmission drives are very compact. To satisfy that need, it is very suitable the radial piston motor MCR-X, expressly developed for the requisites of small excavators ranging from 3 to 8 tons. This motor stands out for the notable performances at low speeds and for the silent operation. MCR-X is an optimal integration for the re-processed LUDV Rexroth system and a very interesting alternative to drives for the rotation groups currently available on the market.

A complete range

The range of Bosch Rexroth products is completed by control levers, joysticks and pedals that allow the exploitation of the full potentialities of excavators up to 12 t. The further improvement of the LUDV system is an example of how Bosch Rexroth can optimize machines to obtain their maximum productivity, without more energy consumption than what is strictly necessary.

The unitary Rexroth 4EE approach (Rexroth for Energy Efficiency), thanks to flexible solutions, helps manufacturers both in optimizing series of already existing vehicles and in conceiving new models compliant, for instance, with the TIER 4 Regulation.