Patent ID: 7963852
Filing Date: 2011-06-21
Classification: B60K,F16D

Abstract:
1. A spline shaft for transmitting torque while making it possible to move relatively to each other in axial-line direction, the spline shaft comprising: a first shaft being provided with an outer-peripheral spline, which is formed on its outer peripheral surface; and a second shaft being provided with an inner-peripheral spline, which is formed on its inner peripheral surface, which engages with said outer-peripheral spline peripherally, and which is made slidable axially; at least either one of said outer-peripheral spline and said inner-peripheral spline being equipped with: a substrate whose surface is formed to a predetermined surface roughness; and an amorphous carbon-system hard thin film, which coats and forms the surface of said substrate, wherein said predetermined surface roughness is from Rz (10-point average roughness based on JIS B 0601: 1994) 0.1 μm or more to 5.0 μm or less.