engleski

Design Proposal of a Hydrostatic City Bus Transmission

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 propeller shaft and rigid rear axle, effectively ruling out any completely level floor design. An improvement is offered by hydrostatic transmission, using high pressure fluid for power transmisison. The fluid flows from pump to motor via relatively small diameter pipes, enabling the design of a completely level floor. Hydrostatic transmission enables continuous variation of transmission ratios, and hydraulic motors can be placed very close to the wheels, enabling all wheel drive together with increased passenger space. Finally, hydraulic accumulators can be added to a hydrostatic transmission in order to enable the recovery and reuse of kinetic energy which would be otherwise lost by braking.

hydrostatic power transmission; vehicle kinetic energy recovery system; city bus

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