A Procedure to Isolate the Electrical Capacitance of Tooth Contacts From Charging Curve Measurements of a Gear Stage

This article describes a procedure to partition electrical capacitance measurements of a single-stage gearbox into its individual components: the capacitances of contact zone, inlet/outlet zone of the contact, trailing tooth flank, oil sump, and surrounding components, such as the housing. It is shown via a comparison of bearinx simulations with experimental measurements that the capacitance of a gear stage can be calculated sufficiently accurate by using experimentally determined correction factors. For the presented test rig, the correction factor k_C amounted to 4.8, with a relative permittivity ε_r of 2.3. Furthermore, it is shown why both a high temporal resolution and the recording of at least one gear revolution are necessary to capture the capacitive behavior of a gearbox in an experimental investigation. It is also shown how speed, load, temperature, and a variation of the tooth width from 3 mm to 12 mm affect the capacitance and how the capacitance varies along the line of action.