The cheap and compact rubber dampers of shear-type have been widely employed as the torsional vibration control of the crankshaft system of high-speed, automobile diesel engines. The conventional rubber dampers have various rubber forms owing to the thorough investigation of optimum dampers in the design stage. Their rubber forms can be generally grouped into three classes such as the disk type, the bush type and the composite type. The disk type and the bush type rubber dampers are called “the basic-pattern rubber dampers” hereafter. The composite type rubber part is supposed to consist of the disk type and the bush type parts, regarded respectively as the basic patterns of the rubber part, at large.
The dynamic characteristics of the vibration isolator rubber depend generally on temperature, frequency, strain amplitude, shape and size effects, so it is difficult to estimate accurately their characteristics. With the present technical level, it is also difficult to determine the suitable rubber geometry which optimizes the vibration control effect.
The study refers to the calculation method of the torsional vibration of a crankshaft system with a shear-type rubber damper having various rubber forms in order to offer the useful method for optimum design. In this method, the rheological formula of the three-element Maxwell model, from which the torsional stiffness and the damping coefficient of the damper rubber part in the equivalent vibration system are obtained, are adopted in order to decide the dynamic characteristics of the damper rubber part.
At first, the basic-pattern rubber dampers in addition to the composite rubber damper have been fabricated on an experimental basis. The dynamic characteristics of these rubber dampers have been examined through static and dynamic experiments. The experimental data and results are pigeonholed by replacing the rubber part with the three-element Maxwell model. And it is shown that the dynamic characteristic values of the composite rubber damper can be estimated by those of the basic-pattern rubber dampers.
Secondly, the vibration system of a crankshafting with the composite rubber damper is replaced with a linear lumped model, in which the torsional stiffness and the damping coefficient of the damper rubber part are estimated by the experimental results of the basic-pattern rubber dampers. The calculated results of the torsional angular displacements by the transition matrix method which is a kind of step by step numerical calculation method, making indirect use of Taylor series, are compared with the corresponding experimental ones and it is shown that the calculated results approximately agree with the measured ones.