Size distribution of the degraded injection pumps elements for the restoration of their operational state

Abstract

Because of machining precision by pairing and running in (lapping) of the conjugated parts (piston and cylinder), the manufacturers, in order to not reject several parts assembled have recourse to execution of several diameters for these parts so that to be respected the conditions of ovality, conicity and the clearance between the conjugated components (max. 0.5÷2μm). To highlight the size and shape of the injection pump elements (piston and cylinder) worn-out after the completion of an operating cycle on the engine, were taken randomly from a sample of 141 injection pump elements, studying the distribution of these dimensions. The study of sizes distribution or of the effective deviations from shape of pistons and cylinders (bushings) of the worn off injection pumps elements, had as scope the knowledge of dimensions range of these, in order to check the possibilities to re-establish the opperational state of these by lepping and re-pairing, pursuing and the determination of the number of measuring pneumatic complets, required in the resettlement process of the opperational state of these. The statistical and mathematical processing aimed to: - determination of average diameters on two directions and in each of the three plans of measurement (both for pistons and for the cylinders of elements); - the determination of pistons ovality and cylinders respectively in the three plans of measurement; - the determination of averages for the piston conicity (cmed)) and for cylinders (CMED); - the determination of averages of the clearances in the three measurement plans for the conjugated parts; - sorting in ascending order of the pistons and cylinders; - highlighting the possibilities to restore the operating status of injection pump elements.