Asymetric damping belt tensioner
A tensioner for a belt drive, comprising: a base carrying a pin defining an axis; a tensioning arm, which can rotate about the pin and supports an idle pulley; and a damping element, which is constrained to a hinge point eccentric with respect to the axis and is carried by one between the base and the tensioning arm so as to co-operate with a friction surface carried by the other between the base and the tensioning arm. The belt tensioner further comprises a resilient element having a first end portion connected in a single point to the damping element and a second end portion connected to the other between the base and the tensioning arm to cause a rotation of the damping element about the hinge point against the friction surface.
1. A tensioner for a belt drive, comprising:
a base carrying a pin defining an axis;
a tensioning arm rotatable about said pin;
an idle pulley supported by said tensioning arm;
a damping element constrained to a hinge point positioned eccentric with respect to said axis and carried by one between said base and said tensioning arm to co-operate with a first friction surface carried by the other between said base and said tensioning arm;
a resilient element having a first end portion connected in a single point to said damping element via a hook, and a second end portion connected to the other between said base and said tensioning arm to cause a rotation of said damping element about said hinge point against said first friction surface;
a second friction surface defined by the other between said base and said tensioning arm, and said second friction surface oriented transverse with respect to said first friction surface and cooperating with said damping element, wherein a turning over moment compresses the damping element against said second friction surface in a direction substantially parallel to said axis;
and wherein said damping element houses said pin with radial play.
2. The belt tensioner according to claim 1 , wherein said single point and said hinge point are axially set apart for generating the turning over moment about a direction substantially perpendicular to said axis.
3. The belt tensioner according to claim 1 , wherein said tensioning comprises a cup-shaped body defining a cavity housing said damping element and said resilient element.
4. The belt tensioner according to claim 3 , wherein the belt tensioner further comprises a fixing element, rigidly connected to said pin for axially constraining an actuation arm, said element comprising labyrinth-seal means cooperating with said arm for preventing any contamination of said cavity.
5. The belt tensioner according to claim 1 , wherein said resilient element is a spiral spring.
6. The belt tensioner according to claim 1 , wherein said hinge point is defined by a single stop element.
7. The belt tensioner according to claim 1 , wherein said damping element is constrained to said hinge point on said base and in that said friction surface is carried by said tensioning arm.
8. The belt tensioner according to claim 7 , wherein said hinge point is defined by a stop element, which comes out radially from said pin and is housed in a seat of said damping element.