Automatic fixture for clamping thin-wall ring gear part through internal expansion positioning and end surface compression

The invention discloses an automatic fixture for clamping a thin-wall ring gear part through internal expansion positioning and end surface compression. The automatic fixture is characterized in that a connecting disc is mounted on a spindle flange of a lathe, a gear internal expansion elastic part is mounted on the end surface of the connecting disc through a spigot, an axial positioning sleeve is mounted outside the gear internal expansion elastic part in a sleeving manner, the gear internal expansion elastic part is provided with an inner cone hole, an open slot is formed in the inner cone hole section and forms a conical surface expansion structure with an expansion core, and the thin wall ring gear part is mounted on outer teeth of the gear internal expansion elastic part and is tightly close to the end surface of the axial positioning sleeve; the thick end of a tension screw is connected with a lathe pull rod and locked by a pull rod round nut, and the expansion core, a belleville spring and an end surface press ring are mounted at the thin end of the tension screw and tightly pressed by adjusting nuts; the end surface press ring provides axial thrust for the expansion core through the belleville spring, so that the gear internal expansion elastic part expands to eliminate mounting clearance between the gear internal expansion elastic part and a part, and an open press plate tightly presses the end surface of the thin-wall ring gear part to realize clamping. With the adoption of the automatic fixture, the thin-wall ring gear part can be positioned accurately.