at its root end portion on the case 2 1 that the armature 9 2 of the valve member may be positioned in the vicinity of the rotary shaft member or the drive shaft 1 on the drive unit side of the sealed housing 2 the ring shaped electromagnet 11 is supported on the ring shaped electromagnet support 12 which is not only borne on the rotary shaft member 1 through the bearing 14 and but also fixed on an external member although not shown such as an engine block the disc shaped magnetic loop element or the magnetic member 10 having the ring portion assembled in the case 2 1 is mounted to confront the armature 9 2 of the valve member the support 12 is fitted at its portion in the magnetic loop element 10 this magnetic loop element 10 has an integral structure having three arcuate holes 10 1 formed in one donut shaped disc as shown in a front elevation in fig2 numeral 10 2 designates three reinforcing bridges joining the inner sides and the outer sides of the arcuate holes 10 1 here the arcuate holes 10 1 are sealed with a sealant 10 1 u2032 in short in order to transmit the magnetic flux of the electromagnet 11 may be efficiently transmitted in the invention to the armature 9 2 of the valve member an activation mechanism for the oil feeding valve member 9 is constructed by using the disc shaped magnetic loop element 10 having the ring portion in the fan coupling device thus constructed when the electromagnet 11 is off or demagnetized the armature 9 2 is made to leave the magnetic loop element 10 by the action of the leaf spring 9.