PI 088-14 Elchingen, 2014-11-18

New landmark for concrete machinery

DHC from Rexroth increases energy efficiency and reduces exhaust-gas and noise emissions by aligning the power that is requested by the hydraulics with the power that is generated by the diesel engine

  • More efficiency with Rexroth A4VG series 40 high pressure pump
  • Diesel Hydraulic Control DHC from Rexroth for optimum coordination between hydraulics and diesel engine to save energy and reduce noise
  • New series 34 of A4VTG axial piston variable pump specifically designed for local demand

As China is one of the leading markets for concrete machinery, requirements in terms of energy efficiency and cost control are gaining momentum. At this year’s bauma China, Rexroth presents a number of answers, including the state-of-the-art series 40 of the A4VG axial piston variable pump for a higher pressure level up to 450 bar in concrete pumps. The Rexroth DHC Diesel Hydraulic Control for concrete mixers offers gains in energy efficiency as well as noise reductions. DHC for concrete mixers relies on reliable and cost-effective components such as the new series 34 of the proven Rexroth A4VTG pump for drum drives, which the company also introduces at the fair in Shanghai.

Higher, stronger, faster: high pressure axial piston pump A4VG series 40 for concrete pumps
The Rexroth series 40 axial piston variable pump A4VG raises the conventional working pressure level above 450 bar. This straightforward solution improves both the energy and the thermal balance of the hydraulic system of concrete pumps and reduces pressure losses and heat generation. The resulting absence of overheating problems improves the reliability of the overall system.

Since the series 40 A4VG allows for high as well as low pressure pumping, a dedicated switching module is no longer needed. A further benefit is the possibility to use smaller hydraulic cylinders, which need less valuable installation space. Additional features such as the integrated pressure cut-off, electric proportional control, and the swash plate angle sensor contribute to a simplification of the hydraulic system and improve its responsiveness.

Currently, the new concrete pump design with A4VG/40 axial piston units from Rexroth has successfully completed the commissioning and testing period in cooperation with a well-known Chinese OEM.

Energy-saving pioneer: DHC Diesel Hydraulic Control for concrete mixers
In traditional concrete mixers manufactured in China, the hydraulic pump is generally adjusted by a mechanical gear lever. The same is true for the diesel engine when the operator unloads the concrete at the building site. This manual approach often leads to a non-optimal coordination between the diesel engine and the hydraulic drive, i.e. more power than necessary is provided for the job.

DHC Diesel Hydraulic Control from Rexroth stops this waste of energy and reduces exhaust-gas and noise emissions by aligning the power that is requested by the hydraulics with the power that is generated by the diesel engine. DHC uses the CAN bus communication between the electrically controlled hydraulic pump and the diesel engine in order to run the latter at optimum speed and efficiency. At the same time, lower diesel speeds mean an audible reduction in noise.

In traditional concrete mixers with mechanically controlled hydraulics, the rotational speed of the mixing drum is affected by the travelling speed of the vehicle. Higher drum speeds increase energy consumption as well as the wear of the drum, and can lead to safety risks. Excessive drum speeds, for instance, can make the concrete within the drum rise too high. The resulting elevation of the vehicle’s center of gravity can lead to critical driving conditions and even vehicle rollovers.

In comparison to mechanically controlled hydraulics, the Rexoth DHC controls the drum speed during transportation because it adjusts the diesel engine speed and pump output flow based on the measured drum speed signal. The established and well proven Rexroth Constant Speed Drum functionality CSD easily integrates into the Diesel Hydraulic Control in order to increase driving safety. Fuel consumption is reduced and service life of the drum and its drive system extended.

Design-to-region: new size 115 of the A4VTG axial piston pump for drum drives
At bauma China Rexroth premieres the new size 115 of the proven and tested axial piston variable pump A4VTG for drum drives of concrete mixers. The large displacement of 115 cm3 per revolution is especially suited for large mixers of 15 to 24 m3 load capacity.

Rexroth engineers in China further developed the design to meet the specific market requirements in Asia and achieve an optimum price-performance ratio. The result is a new series 34 of the Rexroth A4VTG pumps of which the size 115 is the first representative. Part of the development is the integration of the shaft seal into a new clamp collar, which makes the unit even more durable and resistant against the tough conditions. Taking into account these conditions, the pump is designed to withstand pressure peaks of up to 420 bar.

The new series 34 A4VTG/115 is designed to harmonize perfectly with the new series 70 bent-axis hydraulic motor A2FM from Rexroth, which offers higher power density and compactness. This combination opens new potentials for OEMs to design efficient and cost-effective drum drives for concrete mixers.

Economical, precise, safe, and energy efficient: drive and control technology from Bosch Rexroth moves machines and systems of any size. The company bundles global application experience in the market segments of Mobile Applications, Machinery Applications and Engineering, Factory Automation, and Renewable Energies to develop innovative components as well as tailored system solutions and services. Bosch Rexroth offers its customers hydraulics, electric drives and controls, gear technology, and linear motion and assembly technology all from one source. With locations in over 80 countries, roughly 36,700 associates generated sales revenue of approximately 5.7 billion euros in 2013.

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The Bosch Group is a leading global supplier of technology and services. In 2013, its roughly 281,000 associates generated sales of 46.1 billion euros. (NB: Due to a change in accounting policies, the 2013 figures can only be compared to a limited extent with the 2012 figures). Its operations are divided into four business sectors: Automotive Technology, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 360 subsidiaries and regional companies in some 50 countries. If its sales and service partners are included, then Bosch is represented in roughly 150 countries. This worldwide development, manufacturing, and sales network is the foundation for further growth. In 2013, the Bosch Group invested some 4.5 billion euros in research and development and applied for some 5,000 patents. This is an average of 20 patents per day. The Bosch Group’s products and services are designed to fascinate, and to improve the quality of life by providing solutions which are both innovative and beneficial. In this way, the company offers technology worldwide that is “Invented for life.”

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