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REM Surface Engineering

The Reduction of Parasitic Friction in Automotive Gearbox and Drive Train Components by the Isotropic Superfinish

By: William P. Nebiolo, REM Chemicals, Inc

Technical Papers and White Papers

Microscopic examination of the traditionally ground tooth surfaces of automotive transmission gears reveals a micro-roughness, and unidirectional pattern corresponding to the direction of the gear tooth grinding operation. This unidirectional grind pattern degrades the performance of the gear by acting as a parasitic, friction-inducing surface. Engine horsepower is lost in the inefficient transfer of power through the drive train caused by this friction. This loss of power can most easily be monitored as heat generation; however, other gearbox characteristics are indicators of reduced performance. These include, but are not limited to, high Hertzian contact stresses on the complementary gear tooth flanks; gear tooth flank metal loss through wearing, pitting, spalling or breakage as well as increased torque requirements for complementary gear meshing.

By refining the surfaces of the teeth of a transmission’s gears to achieve the Isotropic Superfinish (ISF), the gears require no break-in period, produce a cooler gearbox operational temperature, almost completely eliminate gear tooth wear, pitting, spalling or breakage, diffuses Hertzian contact stresses during gear meshing, and reduces rotational torque requirements. These improvements synergistically combine to reduce parasitic loss of engine horsepower through the gearbox, resulting in a more efficient transfer of power from the engine to the wheels.

This paper will review the chemically accelerated vibratory technique used to generate the ISF surface on automotive gearbox, and drive train components. Additionally, before and after testing results of traditionally ground and ISF components will be presented describing the aforementioned benefits.


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