PURPOSE: To improve the precision of tension detection by fixing the outer circumferential part and center part of a flat plate type joint made of elastic metal to a metallic support and an elastic displacing member, and providing a beltlike part which extends almost in a circumferential direction between both points of fixation.

CONSTITUTION: The elastic displacing member 34 constituted by coupling a pedestal 31 and a support base 32 by a couple of beams 33 is arranged in an internal recessed part 30 of the case 29 of a transducer (not shown in a figure) and fixed to the case 29 with a screw 35, and the projection part 44 of the annular part 40 of the metallic support 39 at a terminal of a nonrotary shaft 3 supported on the transducer at both terminals is inserted into a recessed part 45 of the case 29 so that the interval 46 is nearly equal to the interval 36 between the base 32 and case 29. Further, the outer circumferential and center parts 51 and 53 of the plate type elastic joint 47 are fixed to the projection 44 and 32 with screws 48 and 49; and stop holes 52 and 54 for the screws 48 and 49 are arrayed radially and the beltlike part 56 is provided along an arcuate hole 55 at both sides of each radius to obtain flexibility to axial displacement.