Abstract
In automatic transmissions for cars, a damper is installed in the lock-up clutch to absorb torsional vibrations caused by combustion in the engine. Although a damper with low stiffness reduces the torsional vibration, low-stiffness springs are difficult to use because of space limitations. To address this problem, dampers have been designed using a piecewise-linear spring having three different stages of stiffness. However, a nonlinear subharmonic vibration of order 1/2 occurs because of the nonlinearity of the piecewise-linear spring in the damper. In this study, we experimentally and analytically examined a countermeasure against the subharmonic vibration by increasing the stages of the piecewise-linear spring using the one-degree-of-freedom system model. We found that the gap between the switching points of the piecewise-linear spring was the key to vibration reduction. The experimental results agreed with results of the numerical analyses.
Highlights
Engines used in automobiles generate strong torsional vibrations in the powertrain
We performed experiments to evaluate the countermeasure for suppressing the subharmonic vibration by increasing the number of stages at the switching point of the spring
In the numerical integration used in the shooting method, the time when the displacement is at the switching point of the piecewise-linear spring was calculated precisely using the Newton-Raphson method
Summary
Engines used in automobiles generate strong torsional vibrations in the powertrain. To address this problem, a torsional damper is installed in the automatic transmission lock-up clutch. Dampers with piecewise-linear spring characteristics having three different stages of stiffness are used to overcome this problem. This type of spring can realize a wide range of restoring torque characteristics in a small space. A nonlinear subharmonic vibration of order 1/2 (referred to hereafter as the subharmonic vibration) occurs because of the nonlinearity of the piecewise-linear damper spring. A number of studies [4,5,6] have examined nonlinear vibrations in mechanical systems having piecewise-linear spring properties, countermeasures against the subharmonic vibration have not yet been studied. We experimentally and analytically examined a countermeasure against the subharmonic vibration by increasing the stages of the piecewise-linear spring using the one-degree-of-freedom system model. The results of the experiments and the numerical analyses were found to be in good agreement
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