Assembly and instrumentation of a didactic bench for testing of starters of internal combustion engines

Abstract

The instantaneous measurement of angular speed in flywheels has been used, among other applications, in experimental tests of internal combustion engines to diagnose their working conditions; particularly it has been implemented to evaluate the performance curves of starter motors and the battery conditions. This article focuses on the development of a flywheel-based didactic test bench to diagnose performance of starters of up to 3 kW power, installed in internal combustion engines of up to 3 liters of displacement, typical of commercial cars. The main features of the designed bench are described: mechanical elements, structural elements and accessories; angular displacement, current and starting voltage sensors and systems for reading, processing and presentation of information. An inductive sensor is used for the detection of the angular position of a flywheel equipped with a toothed crown; the analog signal is converted to digital and digitally processed in a code written in Matlab®. During the test of the testing starter motor, the variation of the electric power delivered by it and the variation of the angular speed of the charging system (flywheel) from its initial state to stabilization are determined. The acquired experimental information is used to construct and analyze the behavior profiles of instantaneous angular speed, current intensity, voltage and electrical power. Confronting the forms of characteristics of commercial starters provided by the starter manufacturers, with those of the voltage, current and consumed power signals of the starter tested in the built bench, allows us to conclude on the suitability of the designed test bench and the conceived methodology to carry out didactic characterization and diagnosis tests of starter motors in the Laboratory of Internal Combustion Engines of the Technological University of Pereira.