To ensure the effective contact area between the carbon brush and the rotor and reduce the occurrence of electric sparks，a new type of carbon brush grinding and polishing device was proposed. Based on the dynamic modeling principle of the clearance mechanism，a method for characterizing the internal clearance between the rotating pairs by using the massless virtual rod method was adopted to establish the continuous contact dynamic equation of the connecting rod with clearance. MATLAB was used to solve the equation，and the influence of the clearance between the rotating pairs and the speed of the crankshaft on the dynamic stability of the connecting rod mechanism with clearance was studied. In order to reduce the influence of fitting clearance and speed on its dynamic performance，a low speed of 10 r/min was used for attitude adjustment，and the fitting clearance between the rotating pairs should be controlled within ± 0.2 mm. By adjusting the posture of the carbon brush，the dynamic stability of the carbon brush mechanism was improved. The results show that under the same speed of the crankshaft and structural parameter conditions，smaller clearance between the rotating pairs indicates better dynamic stability of the attitude adjustment mechanism. Under the condition of constant clearance，a slower speed of the crankshaft indicates better dynamic stability of the attitude adjustment mechanism.