New components technology

12 December 2013

Bosch Rexroth’s high-efficiency traction control (HET) is an all-hydraulic system that automatically

Bosch Rexroth’s high-efficiency traction control (HET) is an all-hydraulic system that automatically switches between two- and four-wheel drive, as required by ground conditions.

It would be easy to see the construction equipment industry as conservative and unsophisticated, with the design of machines rooted firmly with steel structures, diesel engines and hydraulic power. But it is an industry that is increasingly embracing new materials, new technologies and more sophisticated components, not to mention a more sophisticated approach to design.

Why? The drivers of greater fuel efficiency, greater productivity of the finished machines, greater reliability and preferably lower cost mean manufacturers and their component suppliers have to look at new approaches to design.

One example of this is the development of hybrid hydro-mechanical variable transmissions (HVTs), such as the R2 system jointly developed by Dana and Rexroth, and unveiled at this year’s Bauma exhibition.

Combining a hydrostatic drive (Bosch’s speciality) and mechanical drive (Dana’s forte) into a single unit means it is possible to reap the advantages of both technologies. The hydrostatic drive is good at low speeds, where mechanical systems are inefficient, while the mechanical system is better at delivering high speeds.

The R2 is designed for loaders, graders, industrial lift trucks, reach stackers, forestry skidders and other off-highway applications with a 135 to 195 kW engine. Dana Rexroth said it achieved fuel savings in the drivetrain of up to -25% when compared with the same loader fitted with a conventional torque converter transmission.

Jeroen Decleer, managing director of Dana Rexroth Transmission Systems, said, “The R2 is a truly innovative transmission platform that combines Dana’s and Bosch Rexroth’s deep knowledge of powertrain.”
Another advantage is that the R2 provides step-less acceleration (i.e. no gear changes), while physically it is more or less the same size as a conventional torque converter.

One way of looking at what devices like the R2 do, is that they break the link between engine speed and vehicle speed. This means the engine can be run at a steady speed at its most efficient point in terms of revs, torque, fuel efficiency and so on, without having to stray into the low speeds where diesel engines do not perform well.

Dana itself has been working on the Spicer PowerBoost System, a new line of integrated hydraulic-hybrid powertrain concepts which capture energy that would normally be wasted in the drivetrain and hydraulic systems. The company says this could reduce fuel consumption by -20% to -40% depending on the application and duty cycle.

It added that Spicer PowerBoost could also reduce total owning and operating costs by increasing productivity, reducing maintenance, and allowing for the use of a downsized engine.

Aziz Aghili, president of Dana Off-Highway Driveline Technologies, said, “In an era when equipment manufacturers are finding it difficult to identify incremental gains in efficiency, Spicer PowerBoost offers a tremendous leap forward in productivity and reduced costs that easily fits into existing design envelopes.”

The heart of the system is a hydraulic accumulator, which captures waste energy. This can then be access as required, for parts of the cycle such as accelerating from a full stop, lifting a load, or driving into a stockpile and so on.

It can also be configured to minimise idling by shutting off the diesel engine and accessing power captured in the accumulator for vehicle operations that consume low amounts of energy, such as inching, light working conditions, and low travel speeds.

Oil as required

Bosch Rexroth meanwhile used Bauma to unveil some innovations of its own. It launched a new component and software package it said could reduce the fuel consumption in excavators by up to -20% without compromising performance. The company’s new Virtual Bleed Off (VBO) system works by determining the volume of hydraulic oil needed for a particular function using sensors and using this information to control the pump.

Rexroth said this led to better response and greater efficiency, as well as safeguarding against high pressures.

Doosan has already adopted VBO for its DX340LC-3 and DX380LC-3 Stage IIIB compliant crawler excavators, where it is branded as D-Ecopower technology. A +26% improvement in productivity and up to 12% in fuel savings is being claimed for the electronic pressure-controlled pump and closed centre hydraulic system, depending on the mode selected.

Rexroth has also launched an automatic stop-start system for construction machinery, which it says is an industry first. This concept, which is common in the automotive industry, works on the principle that fuel is saved by turning off the engine in idle periods. It uses a hydraulic flywheel in its system, which allows hydraulic functions to start up immediately, before the engine comes back on. This system can also provide a boost function during normal work.

Another innovation is the company’s high-efficiency traction control (HET) for wheeled machines, switches automatically from two-wheel to all-wheel drive. It is a compact design and can be installed without any electronics, which should make it relatively easy for designers to incorporate.

The heart of the system is a valve block, which feeds power to the second axle, should sensors indicate the main drive axle is starting to slip. In fact, the action of a wheel slipping frees up oil in the system due to the reduced load on the hydraulics, so this is a way of taking advantage of energy that would otherwise be wasted.

One of the potential knock-on effects of more efficient transmissions and hydraulics is that engines on machines would not have to be as big or powerful. A smaller engine or lower power output translates to less fuel being consumed, so this move towards engine downsizing is a big trend in the industry today.

Cummins Turbo Technologies is working on systems that could contribute to this, such as its next generation of Holset variable-geometry turbochargers (VGT). The company has unveiled a prototype which it says can improve engine efficiency and therefore reduce fuel consumption. However, Adrian Tipling, the company’s account executive for global OEMs, said that it would not be available commercially until 2016.

He said it would be 2018 before another of its prototypes, the waste heat recovery turbine expander, was available. He explained this used waste heat from the engine to deliver energy to the drivetrain, or electrical energy to a grid, network or battery.

Value engineering

Another trend in the components sector is to design parts that are suitable for the various large, high-growth emerging markets around the world. An example of this is the joint venture set up between ZF and Liugong in September 2012, to make axles and transmissions for the enormous wheeled loader sector in China.

July saw ZF Liuzhou Axle unveil its first prototype, the AP3000 axle, which can be assembled with dry or wet brakes, and is designed for 5 and 6 tonne capacity wheeled loaders.

An unusual point about the joint venture is that it is not a case of ZF pouring in the technology and Liugong supplying cheap labour. The technology and R&D aspects are split 50:50 between the two parties.

“Our co-operation with Liugong strongly shows the ‘Design to market’ strategy which has been consistently followed by ZF, especially in the field of off-highway systems. Together with our partner Liugong, we have developed a product which exactly matches the requirements of the Chinese market,” said ZF Board member Wilhelm Rehm.

A team of Liugong and ZF engineers started work on the axle design in October 2011. This led to the development of a modular design allowing dry disc brake (Basic Line) and wet multi-disc (High Line) versions to be produced from a large number of common parts.
This all goes to show that while new technologies and design approaches could help unlock fuel savings, innovative machine design is also about doing more with less.

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