4. SIMULTANEOUS MEASUREMENT OF TORSIONAL ANGULAR DISPLACEMENT WAVEFORM
The test engine was equipped with the torsional viscous-friction damper. An eddy-current dynamometer was connected to the crankshaft of the engine via an intermediate shaft and a universal joint. The torsional vibration waveforms were simultaneously measured at the outsides of the inertia ring and the casing. Transparent acrylate resin suitable for penetrating light was adopted as the material of the casing part. The tapes, in which white and black parts were arranged alternately for generating signal pulses, were stuck in the outsides of the casing and the inertia ring. The floodlight from the light emission division of the photo sensor, and the reflected light was detected by the light-receiver. The electric frequency signals proportional to engine speed were obtained from the photo pickup. The measured signals were transmitted to the phase-shift torsiograph equipment via the adapter which calculated the average of angular velocity (the center frequency). The torsional vibration waveforms could be obtained from the torsional angles, which were calculated using the relationship between the measured and center frequencies. The signals were recorded by the data logger via the amplifier. The measured torsional waveforms of the damper inertia ring and the casing were harmonically analyzed using the F.F.T. analyzer. The schematic drawings of the experimental system are shown in Fig. 2. The torsional vibration waveforms were measured under full load from 1000 r/min to 3000 r/min. The temperature of the circulating water and the lubricating oil of the engine kept constant, and also the surface temperature of the viscous damper was retained at the approximately fixed 333 K in the experiments.
5. MEASUREMENT RESULTS OF AMPLITUDE OF TORSIONAL ANGULAR DISPLACEMENT
Fig. 3 illustrates the measured amplitude curves of torsional angular displacement at the pulley end of the engine crankshaft system without a damper. The 4.5th and 6th orders of the 2nd node resonant torsional vibrations appear mainly within running engine speed. These orders are major critical orders of a 6 cylinders, in-line engine. Fig. 4 illustrates the measured torsional vibration waveforms in the vicinity of the 6th order resonant engine speed of 2170 r/min as an example of the results of simultaneous measurement at the damper casing and the inertia ring of the crankshaft system with the standard viscous-friction damper. Figs. 5 and 6 show the measured amplitude curves of angular displacements at the damper casing and the inertia ring of the crankshaft system with the standard viscous damper, respectively. The torsional vibration amplitudes of angular displacements at the damper casing are drastically reduced in comparison with those without a damper.
Fig. 5 Amplitude Curves of Torsional Angular Displacement at Damper Casing (Inertia Ring No. 02)
6. FORMULA FOR COMPUTATION OF DYNAMIC CHARACTERISTICS VALUE IN SILICONE OIL PART OF VISCOUS DAMPER
The viscous damper consists of an annular seismic mass enclosed in a casing filled with silicone oil. And, the equation of the complex damping coefficient is derived as in the following, in order to investigate the dynamic characteristics of the silicone oil parts of the viscous damper on the basis of the measured data obtained from the experiment. Complex coefficient of torsional viscosity of silicone oil μ* is defined by the following equation [28]*-[32]*.
