Residual air discharging device of braking system

A residual air discharging device of a braking system comprises an upper body and a lower body. The upper part of the lower body is provided with a bushing and is connected with the upper body through the bushing; an air passage is arranged in the lower body, an air inlet is formed in the lower part of the lower body, and the air passage and the air inlet are perpendicular to each other and communicated with each other; a steel ball capable of freely moving is arranged in the air passage; the inner diameter of the air passage is slightly greater than the diameter of the steel ball; a blind hole is formed in the upper body, an air outlet is formed in the upper portion of the upper body, and the blind hole and the air outlet are perpendicular to each other and communicated with each other; a through hole is formed in the middle of the bushing; the upper end and the lower end of the through hole are communicated with the blind hole and the air channel respectively. A cambered surface is arranged at the lower end