To prevent the increase of an occupying space at mounting of a casing by restricting a mounting posture or a mounting position of the casing without increasing a number of parts and complicating a shape, even if an insertion direction of a bracket is different.

At a free end portion 22 of a bracket 25, a fitting recessed place 23 having a first fitting recessed plate 42 and a second fitting recessed place 43, and locking protrusions 24a, 24b are provided. The casing 26 is integrally provided with a strut portion 29 having fitting parts 40a-40d at axial symmetry or surface symmetry, and a flange portion 31 formed with engaging holes 30a, 30b. The free end portion 22 of the bracket 25 is inserted from multi-directions of upper, lower, right, and left sides, thereby coupling the casing 26 to the free end portion 22 of the bracket 25.