Page 27 - Commercial Vehicle Engineer - September 2021
P. 27

    How component stresses were neutralised after a series of simulations
higher pressure demands, engineers must ensure that hydraulic components are robust and reliable enough to offer extended life, protect against dust or dirt penetrating the system, and are easy to maintain and service in case of any malfunction in the field. Furthermore, for devices like Multiplate couplings, which are designed to improve operator comfort, human ergonomics and safe operation are of prime importance.
Danfoss Power Solutions' Multi-FF coupling caters to the pressure-resistance requirements of wide-ranging applications in the commercial vehicle arena, where high working pressures prevail. Despite these high pressures, Multi-FF offers a safety factor of 4:1 before fracture occurs.
Featuring a centralised locking system based on a rack and pinion mechanism, Multi-FF is extremely robust in the face of high pressure. The coupling is also qualified for one million impulse cycles, at a safety factor of 1.33 for pulsating pressure, to ensure resistance against fatigue failure when subjected to hydraulic shocks in commercial vehicle applications. Reliability is a further inherent design feature, providing extended service life for users.
Danfoss Power Solutions uses finite element analysis to simulate and optimise each system component, which helps establish the Multi-FF’s robust characteristics, while simultaneously maintaining a compact dimensional envelope. Danfoss Power Solutions undertakes virtual simulations of all possible load combinations acting on the Multi-FF due to spool position changes on the equipment, ensuring system safety.
The images above illustrate how component stresses were neutralised after a series
of simulations, which improved product reliability.
As is the expectation from OEMs serving the commercial vehicle market, the design of Multi-FF is such that it occupies less space on trucks and trailers. An internally mounted optimised guiding and locking mechanism, smartly arranged QDCs and astutely designed system components help to keep Multi-FF compact. In addition, the rack and pinion-based guiding mechanism facilitates the effortless connection of QDCs, which in turn helps minimise the length
of the handle system, again serving the compact package ambition.
The basis of Multi-FF’s core functionality is rack and pinion kinematics. Here, the pinion in a fixed plate rotates via the handle to translate rotary motion into linear motion (highlighted by blue arrows in the image below), subsequently making the required connections. In contrast to cam- and follower-based Multiplates, the rack and pinion design provides purely linear motion, without tilting the movable plate assembly, which makes it easy for the connection of two sub-systems.
Multi-FF's rack and pinion kinematics
In most commercial vehicles, different attachments come with two or three double-acting hydraulic cylinders to carry out various functions. In turn, four or six hydraulic lines are required to transmit power from machine to attachment. The connection of so many lines one-by-one using standalone QDCs is not only cumbersome for the operator but requires significant time and is prone to cross-connection. Such situations are where the easy and quick connection of all couplings in one go, without any special tools, adds value
for commercial vehicle OEMs and end users.
Over the past few years, the trend in the commercial vehicle sector has been to offer compact machines, but with the same power and operating capabilities of larger counterparts. This trend subsequently demands higher pressure resistance capability from hydraulic system components, while keeping the size and weight of parts in check.
For almost all commercial vehicles
it is becoming necessary to make all sub-systems lighter and more compact. For hydraulic components deployed on trucks and tippers, for example, rugged and dirty environments pose different challenges. In addition to satisfying

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