Original scientific paper
Design proposal for a hydrostatic city bus transmission
Željko Vrcan
orcid.org/0000-0002-7005-4130
; Faculty of engineering, University of Rijeka, Rijeka, Croatia
Dubravka Siminiati
; Faculty of engineering, University of Rijeka, Rijeka, Croatia
Neven Lovrin
; Faculty of engineering, University of Rijeka, Rijeka, Croatia
Abstract
A city bus is probably one of the harshest operating environments for a vehicle transmission. The
average operating speed is low, while frequent stops require swift acceleration from standstill. The options
for the placement of transmission and suspension components are highly restricted as the passenger space
must be as large as possible, with a completely flat vehicle floor for ease of passenger movement, and
ground clearance is kept as low as possible to facilitate the entry and exit of passengers. Therefore, it is
common to place the engine and gearbox at the rear end, and power is transmitted to the wheels via a
propeller shaft and a rigid rear axle, effectively ruling out any completely level floor design. An
improvement is offered by the hydrostatic transmission, using high pressure fluid for the power
transmisison. The fluid flows from a pump to a motor via relatively small diameter pipes, enabling the design
of a completely level floor. The hydrostatic transmission offers continuous variation of transmission ratios
and the possibility that hydraulic motors can be placed very close to the wheels, thus enabling all- wheel
drive and increased passenger space. Finally, hydraulic accumulators can be added to a hydrostatic
transmission in order to recover and reuse kinetic energy which would otherwise be lost by braking.
Keywords
hydrostatic power transmission; vehicle kinetic energy recovery system; city bus
Hrčak ID:
74924
URI
Publication date:
12.12.2011.
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