Development Of The New Type Digital Crankshaft Deflection Gauge

The crankshaft of marine diesel engine is the power hub of ship, its operation states have great impact on the safety of navigation. As one of the important characteristic parameters, crankshaft deflection could reflect the state of the marine diesel engine crankshaft. In order to ensure the ship’s navigation safety, the crankshaft deflection need to be measured regularly for understanding the working state of the crankshaft easily and avoiding safety accidents so as to reduce economic losses.This article has made in-depth study in the traditional machinery type crankshaft deflection measurement, the results showed that it has some defects, such as complicated installation, insecurity and reading error. So, it was very necessary to develop a new digital display crankshaft deflection which has high measuring accuracy, simple operation, high reliability and cost-effective.Firstly, based on the analysis of the present research situation of the crankshaft deflection measuring instrument at home and abroad, the general scheme for the design of a new digital display crankshaft deflection was provided, a comparative study of varies inductive displacement sensor was carried out, and the structure and material were also discussed, then the mechanical structure and material of the displacement sensor were determined.On this basis, in order to improve the measuring accuracy of the measuring instrument, the finite element software Ansys was used to analyze the magnetic field distributing around the magnetic steel of the designed displacement sensor, and the impactions on the measuring accuracy of the measuring instrument caused by the size of the magnetic steels, the gap between symmetric magnetic steels and the moving interval of Hall element in the magnetic field were obtained.Secondly,the measuring system of the new digital display crankshaft deflection were introduced from hardware and software points of view, and the working theory and function realization were described in detail including the signal processing module, A\D data acquisition module, OLED module, wireless remote control module and the drivers of these module. After that, according to the function sequence, the subroutines and main program were combined to form a whole measuring system, which can realize overall operation of the digital display crankshaft deflection.Finally, the calibrated data of the new digital display crankshaft deflection were given, and the performance index of the measuring instrument were got. An real time experiment was conducted to compare the new digital display crankshaft deflection with the traditional machinery type of crankshaft deflection measurement, the results showed that the new digital display crankshaft deflection was able to satisfy the requirements of the measurement due to high measuring precision, high reliability and convenient measuring operation.