Stability analysis and simulation of the vibration behavior of worm gears in drive systems

Self-locking worm gears have the advantage, that they can position loads, blocking any further movements. This feature exploits the physical effect of self-locking. This provides an efficient solution, since any further locking devices, such as brakes, can be omitted. A load of arbitrary dimension is safely held in position even if the motor is turned off. In practical applications the exploitation of self-locking is not free of problems. Under certain circumstances chatter vibrations can arise, which have a negative impact on comfort and noise generation, increase wear, and can lead to instabilities, which render impossible the operation of the equipment. The paper examines the influence of various parameters on the occurrence of chatter phenomena analytically for systems with few degrees of freedom as well as numerically for complex vibratory systems. The results are summarized in stability charts as functions of similarity indicators and are discussed. Known charts are extended by the additional condition of damping influence. The developed physical vibratory model for the worm gear considers its relevant geometry, mass, and stiffness parameters. The model permits the simulation of arbitrary worm gears under considering the interactions with the surrounding vibratory components of drive, output side, and bearings. Complex drive systems with manifold nonlinearities are hardly accessible via analytic solutions. Using simulation, additional driveline factors influencing the dynamic behavior (and the chatter in particular) are identified, which exceed the conclusions from analytical solutions found in hitherto existing directives. The paper provides the design engineer with utilities and tools for preventing chatter vibrations in worm gears. Examples from practice demonstrate the effectiveness of various measures which can be taken in order to avoid chatter. Physical and mathematic interrelationships are explained and tools are provided with which the design engineer can forecast or avoid chatter vibration in drive trains with worm gears. Practical examples demonstrate the effect of different methods.