PURPOSE: To obtain gradual locking characteristics by arranging two axially movable discs between three axially fixed discs, forming two pairs of continued chamber zones, and forming two pairs of tips on the surfaces of respective discs.

CONSTITUTION: At least two axially movable discs 7, 8, 9 are arranged between discs 3 to 6 which are axially fixed. At least two pairs of chamber zones 23 to 28 communicated with each other are provided. Axial tips on the surfaces of the movable discs 7 to 9 and fixed discs 3 to 6 are relatively dislocated from one another in at least one group of discs such that volmetric change between the chamber zones connected to each other is reversed in the relatively dislocated state, when a housing 1 and hub 2 are relatively rotated. At least two pairs of tips are formed on the surfaces of the discs 3 to 9. It is thus possible to easily manufacture a coupling, provide small measurement and even power, and gradual locking characteristics.