Bearing surface in e.g. engine connecting rod, includes lubrication micro-pockets in closely-spaced pattern of rows formed by picosecond-pulsed laser beam around bearing surface

摘要

The micro-pockets (10) have an extent of less than 0.5 mm, preferably less than 0.1 mm in the direction of the surface normal, when seen in cross section. The pockets have an approximately elliptical, lengthy or circular cross section. They have an inward conical form in the workpiece, with a depth less than 20 mu m, preferably less than 10 mu m. Their depth is a multiple of the surface roughness R. They are arranged in adjacent rows close to each other, or on a helix. Less than 20%, preferably less than 12% of the entire bearing surface (8) is formed by micro-pockets. The bearing surface is an internal cylindrical surface, an external cylindrical surface or an annular surface. The surface is on a connecting rod or crankshaft. It is an internal cylindrical- or annular surface and the micro-pockets are elongated in the circumferential direction. They are formed by overlapping smaller pockets. The pockets are laser-formed, the workpiece being moved relative to the laser. The laser pulse width is measured in picoseconds and its energy is less than 300 mu J. The pulse frequency exceeds 100 kHz, being preferably 400 kHz. The beam is inclined and the micro-pocket is formed by a sequence of pulses, maintaining relative movement. Preferably 5 pulses are used, i.e. more than 3 and less than 10. The frequency of pulse succession is less than 20 kHz. The laser-processing unit includes a picosecond laser with optics directed onto the bearing surface and equipment causing relative movement. The laser optics rotate about an axis. A scanner or deflection unit is included. The workpiece rotates about the axis of a spindle and is guided adjustably along the axis of rotation. The laser beam is positioned by the scanner to lead, lag or equal the rotary speed of the workpiece. Independent claims are included for the following: (A) the method of forming the micro-pockets; (B) and the processing equipment required.