Variable rod length articulated arm type coordinate measuring machine

The invention discloses a variable rod length articulated arm type coordinate measuring machine which comprises a base, three rotary joints, three swing joints, a base measuring arm, two measuring arms and a measuring head, wherein the two measuring arms are telescopic measuring arms with the same structure, and each telescopic measuring arm comprises a core shaft, a fixing screw, a sleeve and a guide key; for each telescopic measuring arm, the core shaft is mounted in the sleeve, the two are in clearance fit, a section of guide slot is arranged on the inner wall of the sleeve, the guide key is arranged on the core shaft, the relative circumferential fixation of the core shaft and the sleeve can be realized through the guide key, two thread holes are arranged on the sleeve, the fixing screw is screwed in the sleeve through the thread holes, a section of V-shaped slot is arranged on the core shaft, and the fixing screw is screwed for leading an circular arc-shaped head of the fixing screw to tightly push the V-shaped slot of the core shaft, thereby realizing the relative fixation of the sleeve and the core shaft. The variable rod length articulated arm type coordinate measuring machine can reduce the size of measurement space by regulating the rod length of the measuring arms, reduce the measurement error, improve the measurement resolution, achieve the best measurement efficiency, and still have higher repeated positioning precision after the length change of the telescopic measuring arms.