Ensuring Reliable Operation of Machine Parts with a New System of Variable Tolerances

Abstract

Introduction. The article describes an algorithm for determining the system of tolerances for ensuring reliable operation of parts on the section. The block diagram of the program for determining the variable tolerances is demonstrated. There determined blocks of initial information − broken and smooth curves of the controlled parameter, histogram and graph of resource distribution and definition of active area of control, and blocks of building graphs of “marginal fan curves of wear” and systems of admissions for objects of study of two types: for universal fuel pump (UTN-5) and four-section small-sized fuel pump with mechanical regulator. Two ways of determining the system of tolerances are suggested. Variant 1 is a graphical way through constructing “limit fan curves of wear” and determining tolerances by the value of ordinates in the control points. Variant 2 is an analytical way. There is created a formula to replace the graphical method for determining system tolerances. Materials and Methods. Two models of high-pressure pump were selected as objects of the study. Nominal and limit values of parameters were known for the pumps. Schedules for checking and equation of wear curves are determined. Dependencies describing the pump plunger pair wear curves are determined. A histogram and graph for determining pump life cycles are drawn. The active area of control is determined with a given failure probability coefficient. Results. As a result of the study the values for the tolerances system of two types of high pressure fuel pumps are obtained. Reliability values for one pump type are determined. Graphic and analytical algorithms for determining the system of tolerances by the formula are developed. Discussion and Conclusion. The study approves the possibility of using the variable tolerance as a basis for determining the system of tolerances and reliability indicators of the diagnostic object.