Machine element or mechanism – Gearing – With fluid drive
Patent
1997-02-21
1998-10-20
Wright, Dirk
Machine element or mechanism
Gearing
With fluid drive
F16H 4702
Patent
active
058230726
DESCRIPTION:
BRIEF SUMMARY
Vehicle drive systems having a hydrostatic power transmission and a multi-speed change-speed gear have been used for mobile construction and working machinery such as wheel loaders, excavator loaders, stacker trucks, forest tractors, graders, mobile cranes, garbage vehicles, sweepers, airport service machines, etc. They are distinguished by a high power density, a freely mobile arrangement of input and output, the capacity to move oscillating and rotating actuators and the economic solution of complex driving problems.
BACKGROUND OF THE INVENTION
Compared to hydrostatic drive systems with stationary insert associated with the industry of hydraulics, far higher requirements are placed on drive systems of the mobile hydraulics, since they always have to perform outdoors and also very often in pathless grounds and, in part, have to carry out heavy work while moving. To the special requirements belong insensitivity: to shocks and vibrations; to torsional vibrations of the internal combustion engine; to weather changes, humidity, rain, water, dust and dirt and sun radiation; to electrostatic and electromagnetic influences and a broad operating temperature range between -25.degree. C. and +90.degree. C.
This is taken care of by additional coolers and as a rule with a beta 20.gtoreq.75 bypass filtration or, in special cases, by a 5 .mu.m pressure filtration using servo valves. To this are added safety requirements against breakage and failure of structural parts and functions, the same as measures used to ensure operation in emergency. Used for this purpose are hermetically sealed check valves designed as seat valves which are placed on the cylinder connection also having the function of pipe breakage security. For reasons of safety, in the pressure filtration optical acoustic-electronic clogging notices and warning devices are further provided. There have been used for said purposes electrical or electronic control and regulation components which, in addition, offer securities against cable breakage, short circuit, computer failure and failure of electric and electronic parts, together with mechanical safety components, pipe breakage securities, anti-vibration high-pressure bolt connections, interlocking of movable units, mechanical emergency operations. For important parts and functions, a redundancy is provided which is designed in different manners depending on possibility. In an emergency, a drive home must be possible even with limited functions. (LIMB-HOME-Technik).
These mobile working machines operate at a relatively low driving speed substantially below 50 km/h. High traction is often needed here. In order to simplify the work, to adapt the drive system to changing operating conditions and to maximum performance or to partial load from economic and ecologic points of view, these and the maximum load must, to a great extent, be automatically controlled. Finally, the working machines must be easy to operate.
In mobile drive systems one hydraulic pump supplies, as a rule, several sinks. Variable displacement pumps, that is, pumps with variable displacement volume, allow dosing of the sink currents and adaptation of the sink power to the available driving power of the internal combustion engine.
For sinks working independently of each other, pumps are used having an open-circuit operation which without cavitation suck, even at maximum speeds of a diesel engine. They can be easily coordinated with several sinks and can move both linear and rotary actuators. Consequently, they are used in almost all cylindrical drive systems and rotary drive systems whose reversal of direction of rotation or working problems are of secondary importance.
Closed circuits are selected as a rule for drive systems and other rotary sinks. They are easy to reverse on the output and can support themselves on the driving machine when braking whereby the cooling efficiency is reduced and the brakes wear less quickly. If several pumps are used, the energy flowing back can be relayed to other drive systems. In addition, the volume of
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patent: 5605515 (1997-02-01), Fredrikson
patent: 5678463 (1997-10-01), Brambilla et al.
Henry W. Nikolaus, "Oilhydraulik and Pneumatic" 37 (1993, pp. 836 to 845).
Wright Dirk
ZF Friedrichshafen AG
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