Form measurement inside fuel injector nozzle spray holes

Form and roughness measurement inside spray holes of Diesel direct injection (DI) nozzles could be demonstrated for the first time without the necessity of sectioning the hole or making a mold of it. A slender tactile sensor was used with dimensions which were tailored to enable access into millimeter-deep and 100 mu m in diameter holes. it offered nanometer vertical and sub-micrometer lateral resolution at a hundreds of microns vertical deflection range and a millimeter-per-second scanning velocity. Nozzles comprising spray holes of 170 and 110 mu m in diameter were characterized at different scanning speed and probing force. Characteristic signatures and roughness of the hole wall caused by the machining process could be detected at very good reproducibility during surface profiling at different scanning speeds of 1, 10 and 100 mu m/s. Thus, our results prove the potential of the novel sensor for in-process metrology during the manufacturing of injector nozzles. (C) 2008 Elsevier B.V. All rights reserved.