003-13 Lohr am Main, 2013-01-29

Low consumption, high performance

A24VG high-pressure double pump with on-board electronics

Bosch Rexroth increases the effectiveness of the mobile excavator’s travel drive with, among other things, the A24VG high-pressure double pump with on-board electronics

Bosch Rexroth offers a fuel-efficient powerhouse

  • Higher performance and more comfort for mobile excavators
  • A combination of open and closed circuits

No compromises: At BAUMA 2013 in Munich, Bosch Rexroth aims to prove that manufacturers and users of construction machinery do not have to forsake performance to reduce emissions and meet new environmental standards. The company has developed a range of solutions for mobile excavators that provides manufacturers with new options for machine design. These solutions also enable users to operate their machinery at a far lower cost without sacrificing performance.

Today, two issues are gaining ever more importance for construction machinery manufacturers and operators: emissions standards and skyrocketing fuel prices. The U.S. TIER 4 norm and Europe’s off-highway Stage IV are setting new standards for major markets in Europe, North America, and Japan. Without doubt, the new norms will have an impact on global markets. In recent years, regions around the world have tended to adopt new emissions standards in the years following legislation in the industrialized nations. Once TIER 4 goes into effect in 2014, standards for soot and NOx emissions will be far stricter than they are today. For manufacturers, this will give rise to the need to implement full exhaust gas treatment systems. In turn, this will require more space for the greater number of components needed. Additional cooling requirements and the changing dynamics of diesel engines will also need to be taken into account. Given all of these changes, equipment and operating costs could rise considerably. And yet users around the world are keeping an ever closer eye on operating costs. Against the backdrop of skyrocketing fuel prices, manufacturers face the challenge of significantly increasing the fuel efficiency of their machines. At the same time, they must see to it that performance is maintained or even further improved. At first glance, these may seem like irreconcilable contradictions.

As a leading provider of hydraulics solutions for mobile work machines, Bosch Rexroth has tackled this challenge with a mobile excavator in the 15 to 17 metric-ton category. With this specific excavator, the travel drive determines which size the diesel engine needs to be.

With a package comprising the A24VG high-pressure double pump with onboard electronics, the shift-on-fly gearshift as well as software-based controls, Rexroth has increased the travel drive’s effectiveness by at least ten percent. The slewing drive’s effectiveness has also been improved. This has given rise to new sources of performance potential that can be used to downsize the diesel with the aim of reducing emissions and meeting stricter standards. At the same time, the machine’s comfort and ease of operation have been heightened, which makes it more attractive in the user’s daily operations.

Experts at the Rexroth development center have focused on combining open and closed circuits. One pump continues to support the hydraulic work functions of the boom, stick, and bucket in the open circuit. A second unit, namely the compact A24VG high-pressure double variable pump – provides the flow for the travel and slew drive. Located directly on the double pump, the onboard electronics (OBE) control the travel and slew drive, both of which are operated in a closed circuit. The oil flows unhindered from the pump to the motor without passing the control block, as it would in an open circuit. Since pressure levels in the individual circuits are separate from one another, throttling losses can be avoided.

The shift-on-fly solution, a technology patented by Bosch Rexroth, contributes to increasing effectiveness, as it features lighter, smaller components than a powershift transmission. Moreover, it minimizes mechanical friction in the transmission. This is accomplished by adding a synchro component to a two-gear standstill transmission. In so doing, the usual high tractive force is maintained when the engine is started, as is the high efficiency of the hydrostatic travel drive. At the same time, maximum speed can be achieved by shifting into second gear. As with the travel drive, the onboard electronics with the help of sensors translate the driver’s request to rotate the cab. A newly developed software makes it possible to use the slewing function intuitively. At the same time, the driver can change the performance characteristics via a display in the cab. The machine can be adapted to the work situation and features a dynamic mode for high-output excavation. It can also be adapted to perform the softer, more precise maneuvers required of delicate crane work, for instance. Drivers select the appropriate performance spectrum and continue to work as they normally would. Compared with conventional systems, the advantages of open and closed circuits in the slew drive can be combined to one another. This makes operating the machine far more comfortable. As with the travel drive, the diesel can support deceleration via the closed circuit and return the resulting energy to consumers, which are actuated at the same time.

Bosch Rexroth AG is one of the world’s leading specialists in the field of drive and control technologies. Under the brand name of Rexroth, the company supplies more than 500,000 customers with tailored solutions for driving, controlling, and moving. Bosch Rexroth is a partner for mobile and machinery applications, engineering, factory automation as well as renewable energies. The company covers the requirements and special needs of each of these markets. As The Drive & Control Company, Bosch Rexroth develops, produces and sells components and systems in more than 80 countries. In 2011, Bosch Rexroth, part of the Bosch Group, achieved sales of around 6.4 billion euros with 38,400 employees.

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The Bosch Group is a leading global supplier of technology and services. In the areas of automotive and industrial technology, consumer goods, and building technology, over 300,000 associates generated sales of 51.5 billion euros in fiscal 2011. The Bosch Group comprises Robert Bosch GmbH and its around 350 subsidiaries and regional companies in over 60 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 2011, Bosch spent approximately 4.2 billion euros on research and development and applied for over 4,100 patents. With all its products and services, Bosch enhances the quality of life by providing solutions which are both innovative and beneficial.

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Susanne Herzlieb
Maria-Theresien-Straße 23
97816 Lohr am Main
Phone: +49 9352 18-1573