Mechanical Technology January 2015

Mechanical Technology — January 2015

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Hydraulic and pneumatic systems

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osch Rexroth, distributed

in southern Africa by the

Hytec Group of Companies,

has optimised its EHC-8

electro-hydraulic hitch control in order

to replicate the same precise regulation

of power and positioning for the lifting

and lowering of towed agricultural

ploughs in Asia as has been delivered

to European and North American

markets.

In the transatlantic environments

for which it was principally designed,

the EHC-8 enhances agricultural ap-

plications through a greater control of

implement depth, which increases the

accuracy of tillage, turning soils gently

and uniformly for improved yields. The

same levels of project satisfaction were

not, however, originally replicated out-

side of these regions due to the vastly

different climactic and terrain condi-

tions and yields, necessitating Bosch

Rexroth to modify and re-engineer

certain core components and mechani-

cal designs that comprised the EHC-8

control to meet the specific needs of

Asia’s agricultural markets.

The first step of tailoring such a

solution, was a detailed analysis of the

operating conditions. Many regions are

affected by monsoon climates, high

rainfall and high humidity conditions

in which excessively saturated land

poses unique challenges to the use of

mechanically-propelled implements.

The winter months endured by these

regions, conversely, present hot, dry and

This article reports on the customisation by Bosch Rexroth of its

Eurocentric EHC-8 electro-hydraulic hitch control solution to suit

the Indian agricultural market with its rugged and more variable

ground conditions.

Optimised hitch control for Indian ploughs

The saturated, muddy sludge that can characterise Asia’s arable land presents unique

performance challenges for electrical and mechanical components.

The modified components used in the EHC-8 electro-hydraulic hitch control, including the angular

sensor and redesigned control panel.

dusty conditions, extending the loading

demands on equipment components.

Designed for extremes

In optimising the hitch control for

operation in these conditions, two com-

ponents in particular required modifica-

tions: the angular sensor and the control

panel. The control panel was optimised

for enhanced rough terrain capability

through the application of a protective

film, while increased brightness offered

greater visibility under intense sunlight.

The control panel was installed into the

operator armrest to provide maximum

ergonomic operability for improved

productivity and operator safety.

Another modification required to

enhance the hitch’s viability in these

conditions was resistance to leaks. The

IP 67 protection code adhered to in

European environments was not suited

to the dusty conditions experienced in

Asia, requiring a modified sensor and

the separation of electrical components

from the mechanical space.

The controller software also had to

be adapted, shifting from the European

lower linkage to upper linkage control.

Because this configuration only requires

one power regulation sensor instead of

two, Bosch Rexroth was also able to

reduce production costs.

The company reduced costs in

several other areas as well. Because

the plastics used in the construction

are sourced locally, sourcing them is

cheaper, in addition to being more tol-

erant of the local conditions, offering a

slightly more durable service life. Local

manufacturers are also producing the

EHR5 hydraulic valve, which regulates

the flow of hydraulic fluid to the cylin-

ders for greater precision of movement

control for the lifting unit.

Further research and development is

planned for the hitch control beyond the

commencement of mass production in

the first quarter of 2015, including the

implementation of a power measure-

ment sensor tailored to local power

ranges.