Abstract
As the silicone fluid inside of torsional viscous-shear dampers (hereafter called “viscous dampers”) is non-Newtonian fluid, the effective viscosity in the actuation is different in the operation conditions and the dynamic characteristics are complex. The authors refer to the dynamic characteristics of torsional damping and spring of viscous dampers are experimentally investigation in the this paper by adopting simultaneous vibration measurement method at two points. The vibration displacement of the damper inertia ring and the damper casing, and the phases between these two masses can be simultaneously measured in this method. Then, this method is very effective for a good grasp of the torsional behaviors of the damper inertia ring and the damper casing in order to clarify the effect of the silicone fluid on the torsional vibration of the diesel engine crankshaft system. In this paper, the dynamic characteristics of the torsional damping and spring of the silicone fluid filled inside of the viscous dampers were first investigated by changing the inertia moment of the inertia ring, the viscosity of the silicone fluid and the clearance between the damper inertia ring and the damper casing. By judging from the relationship between the kinematic viscosity of the silicone fluid filled inside of the viscous damper and the resonant frequency obtained by the experiments, the authors may conclude that the spring effect of the silicone fluid must be considered in the torsional vibration calculation of the crankshafting with the viscous fluid damper. In the estimation of the torsional damping coefficient and spring constant of the viscous damper from the experimental results, the damper part is treated as one degree of freedom equivalent vibration system and its viscous-shear part can be assumed to be replaced approximately with concentrated equivalent linear damper and spring between the concentrated equivalent masses consisted of the damper inertia ring and casing including the pulley part. The values of the torsional damping coefficient: Cd and spring constant : Kd of viscous-shear part can be obtained by substituting the harmonically analyzed results of the waveforms measured at the damper inertia ring and casing into the expressions of Cd and Kd . If it is assumed that the crankshafting with the viscous damper retains a sufficient linearity in inertia and rigidity of the shafting as to have an engineering significance and that the dampings of the shafting and the viscous damper do not have so high a degree of nonlinearity, the shafting with the viscous damper may be linearized by replacing nonlinear dampings with linear dampings by the equivalence of dissipation of energy during one period. Torsional vibration calculations can be made by replacing the crankshaftings with equivalent vibration system. And the calculation results were compared with the experimental results. The following conclusions are obtained from the above-mentioned experiments and calculations; [1] The torsional vibration angular displacement amplitude decreases with increase of the kinematic viscosity of the filled silicone fluid. [2] The torsional spring constant and the torsional damping coefficient of the viscous dampings has approximately the tendency to increase with the increase of the kinematic viscosity of the filled silicone fluid. [3] The calculation method for obtaining the values of the torsional damping coefficient and spring constant of the viscous damper from the experimental results by the simultaneous vibration displacement measurement at two points is proposed. [4] Appropriateness of the above-mentioned values of the torsional damping coefficient and spring constant are proved by the comparison of the torsional vibration calculation results by adopting the equivalent vibration system of the crankshafting including the viscous damper with the experimental results.
Keywords: Damper, Dynamic Characteristics, Viscous-Shear Damper, Torsional Angular Displacement, Toirsional Damping Coefficient, Torsional Spring Constant, Simultaneous Measurement, Diesel Engine, Crankshaft System, Calculation