PURPOSE: To provide a coupling capable of automatically locking the connection of a coupling sleeve and a coupling journal when the coupling sleeve is fitted to the coupling journal or the coupling journal is pressed into the coupling sleeve.

CONSTITUTION: To axially fix a coupling sleeve 7 on a coupling journal 8, the coupling journal 8 comprises a locking recess 15, and the recess comprises a locking face 16. A bolt member 25 is displaceable in the direction of locking face 16 in the coupling sleeve 7 by means of the spring force. The bolt member comprises a bolt face 26 complementary to the locking face 16. The bolt face 26 of the bolt member is inwardly projected into the locking recess 14 from a wall of a reception bore 23 of the coupling sleeve 7 receiving the coupling journal 8. The bolt member 25 is fixed by a locking element 35, and the locking element is moved to a release position by the external load.