To ensure a long contact area along a chain span by constantly applying appropriate tensile force to a chain.

A system comprising a tensioner 20 and an arm 16 is constructed. The tensioner 20 is provided with a piston 26 slidably inserted in a hole of a housing 40 to partition a chamber in the hole, a spring for energizing the piston 26 outward from the hole, and a check valve allowing the flow of a fluid from an external pressure fluid source into the chamber and limiting the flow of the fluid in the reverse direction. The arm 16 has a shoe with a blade spring 17 built therein. The upper end of the piston 26 is energized onto the lower face 36 side of the shoe. The shoe is pivotally fitted to a support part 22, and the upper face 32 of the shoe applies tensile force to a chain 10.