storage chamber 30 through a spool 21 as further described later in the other end thereof a fluid passage is formed by the fluid outlet passage 17 the fluid storage chamber 30 and the fluid inlet passage 16 the spool 21 is slidably inserted in an opening provided through the end cover 5 which is communicated with the fluid outlet passage 17 and is pushed in the direction of the axis of the driving shaft 2 by means of a spring 24 the spool 21 is provided with a groove 22 in the outer periphery thereof which is communicated with a spring chamber 25 through a control port 23 the spring chamber 25 is communicated with the fluid storage chamber 30 through a passage 26 which is provided in the side cover 5 a governor weight 18 is attached to a foot portion 20 which is provided in the end plate 6 by a pin 19 so as to be turned thereabout the governor weight 18 is contacted with an end portion of the spool 21 and the governor weight 18 constitutes a discharged fluid control device which operates due to a centrifugal force generated by the rotation of the casing 4 hereinafter operation of the power transmission device of the first embodiment of the present invention having the above described structure will be explained when the internal combustion engine a is operated the power transmission device is operated due to the rotation of the crank shaft 1 then a compressor c for use in a cooler and a fan d which are connected with the power transmission device through a belt means e are rotated at this time even if the crank shaft 1.