It is hard to meet the performance requirements of little vibration

impact and light weight for high-speed and heavy-duty gear transmissions based on the traditional design method which using the cutting tool for gear parameters selection.Based on basic performance parameter requirements of gear transmissions

a direct gear design method of high-speed and heavy-duty gear transmissions is built.Dynamic load coefficient

maximum contact stress and sliding rate are used together to conduct performance indexes of gear transmissions description.The effect of addendum coefficient

pressure angle

spiral angle

gear ratio and displacements coefficients on basic performance parameters of gear transmissions is investigated and a theoretical foundation of direct gear design and optimization parameters are provided.It is found that

the dynamic load coefficient can be decreased

so as to noise and impact of gear drives are reduced by increment of addendum coefficient and spiral angle

decrement of pressure angle.It is also found that

the slip rate can be decreased by increment of addendum coefficient

pressure angle and spiral angle can decrease the tooth surface contact stress

decrement of gear ratio

and the glue of tooth face and transmission failure can be avoided by optimum displacements coefficients.