Three Dimensional Vibration Characteristics of High-Speed Automobile Diesel Engine Crankshaft System with a Viscous Fluid Damper

The torsional vibration of diesel engines has become severer with the increase of exciting force by higher pressure. Therefore, the running crankshaft is highly stressed owing to the large torsional vibration. Then, torsional viscous fluid dampers of high performance have been employed in high mean effective pressure diesel engines as a measure for vibration reduction. As the dynamic characteristics of the dampers have such a great influence on the vibration of the engine crankshaft system that they cannot be ignored, the viscosity of the silicone oil and the peripheral and lateral gaps of the dampers are diversely varied in the experiment. As the equipment for the measurement of torsional vibration displacement, a phase-shaft type torsiograph equipment was adopted so as to make it easy to measure simultaneously angular displacements of the casing and the inertia ring. And the waveforms of axial and lateral vibrations were measured by non-contact maicro-displacement vibrographs and laser displacement vibragraphs. In the experiment, the 6 litters, 6 cylinders, in-line high-speed diesel engine whose vibration characteristics are known quite well was regarded as a vibration oscillator of the dampers. The dynamic characteristics of the high viscosity silicone oil damper and the optimum clearance between the casing and the inertia ring were investigated from a quantitative standpoint under full-load conditions, and the useful data in the design stage were gathered. As the result of the experimental study on the three-dimensional dynamic properties of torsional viscous fluid damper filled with silicone oil, the following conclusions are obtained;

1. (1)
   The clearance value determined from BICERA's empirical formula is not always optimum on every viscosity of the filled silicone oil of the viscous fluid damper.
2. (2)
   The optimum viscosity is different, due to the dimensions of the peripheral and lateral gaps between the outside of the inertia ring and the inside of the casing.
3. (3)
   The effect of the amplitude reduction on the axial vibration of the crankshaft system with the typical torsional viscous fluid damper is small.
4. (4)
   The lateral vibration are coupled with the torsional vibration of the crankshaft system.