AUTOMATIC TENSIONER FOR V-RIBBED BELT

PURPOSE:To improve reliability for a long time use by disposing a first plate spring and a second plate spring alternately, providing projecting portions engaged with the adjacent plate springs in the circumferential direction, and sealing silicone oil in chambers of the first and second housings. CONSTITUTION:When the first and second plate springs 5, 6 are superimposed alternately, the projecting portions are projected out in the respective slits of the counterpart plate springs 6, 5, and engaged with the sides of the slits of the counterpart plate springs to obtain the spring force in the rotating direction. The spring force is transmitted to an idler pulley 3 to apply designated pressing force to the V-ribbed belt. At this time, if the V-ribbed belt is slowly displaced due to a temperature change or the like, it follows up the displacement as an ordinary plate spring, and a damping effect is obtained by silicone oil 11 filled between the plate springs 5, 6 in the sealed chamber 15 for high-frequency vibration such as resonance of the V-ribbed belt. In this case, as a plate spring hard to wear away is used, long-term reliability can be obtained.