Abstract
In order to reduce windage loss 0f a helical gear unit under high speed condition, vacuumization by self pumping feature of the unit had been proposed. This paper introduces some experimental results concerning power losses due to implementation of the concept and its contribution. The method can vacuum the gearbox to a minimum of -0.085 MPa (Gage pressure) at 4000 r/min with the spacing of 0.2mm between the gear outline and shrouding parts. Based on experiments, loss was classified into four types, mechanical loss L_m, windage loss L_w pressure difference loss L_p, and turning flow loss If. It is induced by the reaction between atmospheric air and axial sweep of tooth movement that make circulating flow in the exhaust port, and is dependent on the configuration of exhaust port. Furthermore L_p proved to be the most prominent part in place of L_w which is due to the work done by the gears rotating against the pressure difference between the tooth surfaces 0f high pressure region and low pressure region.
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