Analysis of the dynamic characteristics of gas chamber in rotary hammer

Abstract

Rotary hammer is a high-frequency impact machine with a complicated gas chamber. The design parameters of the gas chamber are dominating to impact energy output and impact efficiency of a rotary hammer. In this paper, the mathematical dynamic analysis and fluid dynamic simulations were presented to analyze the influences of the sensitive design parameters on impact energy output and impact efficiency. The dynamic model of the gas chamber consists of kinematic model of impacting piston, status parameter equations of mass-variable gas volume, flow rate equation of compensation orifices, and the gas leakage equation of rubber sealing rings. A testing frame for measuring the impact energy output was designed, and the results of dynamic analysis were in good agreement with the experimental results by the testing frame. Also a successful drilling efficiency improvement of a mass production hammer was completed by adopting the valuable suggestions from this dynamic analysis. The dynamic characteristics analysis of gas chamber in this paper can provide technical supports for hammer design and parameter optimization.