Development of pneumatic measurement and device for servo valve orifice edge axial dimension error

Spool valve is the power stage of servo valve. The axial dimension error of spool valve orifice edge is one of the most important influencing factors to servo valve flow characteristic. Spool valve is composed of spool and sleeve, and an orifice is formed by square orifice edge of valve sleeve and shoulder edge of valve spool. Due to the cylindrical structure, the axial runout could be called as the axial dimension error. Because of lacking in precision detective method in actual production process, the axial runout is usually neglected. In this paper, a method based on differential pressure pneumatic measurement is proposed and utilized in the measurement of orifice edge axial runout. Based on this non-contact method an automotive measure device is developed. The method is of high accuracy and resolution. It is a new automatic process detective method for servo valve.