摘要:
Piston (1) and piston-rod guide (2) unit for hydraulic shock absorbers, the guide comprising an annular piece (3) provided with a central orifice (5) and an elastic seal ring (4). The piston (1) is made up of a single piece (7) formed by a convexly curved generatrix revolution body (8). The external surface of the piston and the internal wall of the central orifice (5) of the annular piece (3) are provided, at least partially, with respective coatings (6, 9) of uniform thickness, of a material which reduces friction and improves wear resistance, such as polytetrafluoroethylene (PTFE) with a charge of ceramic particles and a pigment. The said charge of ceramic particles and of pigment preferably includes mullite and titanium oxide. The aforesaid coatings (6, 9) of the wall of the central orifice (5) of the annular piece (3) and the external surface of the piston (1) have a uniform thickness of between 20 and 60 micrometres.