The Effects of Gravity on the Response of Centrifugal Pendulum Vibration Absorbers

This paper describes the effects of gravity on the response of systems of identical, cyclically arranged, centrifugal pendulum vibration absorbers (CPVAs). CPVAs are passive devices composed of movable masses suspended on a rotor, suspended such that they reduce torsional vibrations at a given engine order. These absorbers are becoming prevalent in automotive powertrain components in order to expand fuel-efficient engine operating conditions. Gravitational effects acting on the absorbers can be important for a horizontal rotor/CPVA system spinning at relatively low rotation speeds, for example, during engine idle conditions. The main goal of this investigation is to predict the response of a CPVA/rotor system in the presence of gravity. A linearized model which includes the effects of gravity and an order n torque acting on the rotor is analyzed by exploiting the cyclic symmetry of the system. The results show that the N absorbers respond in one or more groups, where the absorbers in each group respond with identical waveforms but shifted phases. The number of groups depends on the engine order n and the ratio Nn. It is shown that there are special resonant effects if the engine order is n = 1 or n = 2, the latter of which is particularly important in applications. In addition, it is shown that for N > 1 the rotor response is not affected by gravity, due to the symmetry of the gravity effects. The analytical predictions are verified by direct simulations of the equations of motion.

Evaluation of Relationship Between Shape of a Rigid Body Unifilar Centrifugal Pendulum Vibration Absorber and Vibration Suppression Performance

The torsional vibration hinders the reduction of automobile exhaust gas emitted by using engines with a reduced number of cylinders. Centrifugal pendulum vibration absorbers (CPVA) have been used in engines to suppress torsional vibration. To clarify the dynamics of CPVAs, much analysis has been conducted using the point mass CPVA as the model of rigid body bifilar CPVA. However, few attempts have been made to analyze the rigid body unifilar CPVA on vibration suppression performance in frequency response. In this study, the authors have analyzed the dynamics of the rigid body unifilar CPVA, focusing on the influence of shape parameters. The results verified that the shape parameters, which relating to moment of inertia or radius of gyration of rigid body unifilar CPVA, influence the vibration suppression performance in frequency response. Moreover, the numerical simulation results were confirmed experimentally and showed in good agreement with the experimental results, and both indicated the dependence of the vibration suppression performance on the shape parameters of the rigid body unifilar CPVA.

Developments in the Design of Centrifugal Pendulum Vibration Absorbers

For over 60 years, the torsional vibration of reciprocating aircraft engines has been controlled by centrifugal pendulum vibration absorbers. Loose weights attached to an engine's crankshaft act as tuned-mass absorbers by oscillating at a frequency in proportion to rotational speed. More recently, similar loose masses have been attached to the flywheels of automobile engines. The need to achieve increased power from fewer cylinders, while reducing weight and improving economy, has exacerbated torsional vibration of the drive train. The dynamics of a wheel carrying many centrifugal pendulums of bifilar design has been the subject of a growing literature, but much less has been written about roller-type pendulums and about overall system performance. This paper is a new analysis of bifilar and roller systems and their design requirements. The current state of knowledge about practical design limitations is explained and the need for further research discussed.