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楼主 |
发表于 2010-7-2 09:26
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【转帖】http://geardesigner.blog.sohu.com/82606782.html
下面这个是塑料蜗轮蜗杆设计的精髓:
There are many applications where the gear must be designed to withstand stall torque loading significantly higher than the normal running torque, and in some cases this stall torque may govern the gear design. To determine the stall torque a given gear design is capable of handling, use the yield strength of the material at expected operating temperature under stall conditions. Only a small safety factor (S = 1,3 – 1,5) needs to be applied if the material to be used is either ZYTEL® nylon resin or DELRIN® 100, as the resiliency of these materials allows the stall load to be distributed over several teeth.
Some applications, like window lift gears for cars, use a steel worm and a plastic helical gear (= worm gear),where the tooth thickness of the steel worm has been reduced in favour of the tooth thickness of the plastic gear.
In this case the gear strength may be limited by the shear strength of the loaded teeth, as given by the equation:
Fmax = n f t τ (N)
n = number of teeth in (full) contact
f = tooth width (mm)
t = tooth thickness (mm)
τ = shear strength = σy / (1,7 S) (MPa)
σy = yield strength at design temperature (MPa)
Again, adequate testing of the moulded prototype is necessary. |
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