Compact tensioner with sustainable damping

摘要

A tensioner assembly that includes a base, an arm, an opening spring (i.e., a torsion spring that opens or radially expands with increasing torque applied thereto), a spring reaction member, and a pivot bushing. The tensioner assembly is configured to orient various loads in predetermined directions. For example, a spring load can be oriented to counteract a hub load to reduce a bushing load that acts on the pivot bushing. As another example, a spring reaction force exerted by the spring reaction member can be employed by a damping mechanism to generate a grounding force that is parallel to the spring reaction force and is directed to intersect an axis about which the arm pivots relative to the base. A tensioner assembly having improved assembly characteristics is also provided.

主权项

1. A tensioner assembly comprising:
a base having a brake drum and a first bushing surface that defines a bushing aperture; an arm having a stem, an arm member, and a spring reaction member that are fixedly coupled together, the arm being pivotally coupled to the base about a first axis, the stem defining a second bushing surface that is received in the bushing aperture such that the second bushing surface is disposed radially within the first bushing surface; a helical coil spring disposed about the stem and a portion of the base that defines the bushing aperture, the helical coil spring having a plurality of coils that are disposed between a first end and a second end, the first end being engaged to the base, the second end being engaged to the spring reaction member, the helical coil spring biasing the arm member in a first rotational direction relative to the base, wherein rotation of the arm member in a second rotational direction opposite the first rotational direction applies a torque to the helical coil spring that causes at least a portion of the plurality of coils to expand in a radial direction; a pivot bushing received in the bushing aperture and engaging the first and second bushing surfaces; a wheel mounted to the arm member for rotation about a second axis that is parallel to and radially offset from the first axis; and a damping mechanism comprising a damping element that is frictionally engaged with the brake drum, the damping element being received between the helical coil spring and the brake drum, the damping element being arranged along the first axis between the pivot bushing and the wheel and being urged radially outwardly into contact with a surface of the brake drum by at least one of the plurality of coils, the damping mechanism being configured to damp motion of the arm about the first axis relative to the base; wherein the arm member is positionable relative to the base in a predetermined range of operating positions, wherein in each of the operating positions a hub load is applied to the arm member by the wheel when the tensioner assembly is tensioning a belt, wherein a pivot bushing load is transmitted between the pivot bushing and the stem when the tensioner assembly is tensioning a belt, wherein a spring reaction force is exerted by the spring reaction member on the second end of the helical coil spring and wherein in at least one of the operating positions the spring reaction member is positioned relative to the arm member such that the hub load and bushing load are directed generally opposite to the spring reaction force.