The invention is an improved tensioner for tensioning a power transmission belt. It is of the type having a pulley adapted to communicate with a surface of a power transmission belt, an arm supporting the pulley upon which the pulley is rotatably mounted via a pulley bearing, and having a shaft supporting the arm. The shaft is rotatably supported by a pivot bearing. Further, it is of the type having an attachment point for a strut with the strut attached to the attachment point. It is improved by the pulley and the attachment point being laterally offset in relation to the pivot bearing and substantially balanced in terms of parasitic torque across the pivot bearing.
1. An improved power transmission belt tensioner having a pulley adapted to communicate with a surface of a power transmission belt, an arm supporting said pulley upon which said pulley is rotatably mounted via a pulley bearing, a shaft supporting said arm, said shaft rotatably supported by a pivot bearing, an attachment point for a strut, and said strut attached to said attachment point, the improvement comprising:
said strut attachment point is laterally opposite of said pivot bearing in relation to the plane of rotation of said pulley;
said strut attachment point forming part of a shield extending from a support for said pulley bearing; and
said pulley and said attachment point laterally offset in relation to said pivot bearing such that a balance line passing through an axis of said attachment point and a center of said pulley intersects said shaft within a lateral limit of said pivot bearing, thereby substantially balancing said tensioner in terms of parasitic torque across said pivot bearing.
2. The improvement of claim 1 wherein, said strut attachment point is laterally opposite of said pulley in relation to the plane of rotation of said pivot bearing.
3. The improvement of claim 2 wherein, said strut attachment point is beyond the lateral limits of said pivot bearing.
4. The improvement of claim 2 wherein, said strut attachment point forms part of a member extending from said shaft.
5. The improvement of claim 4 wherein, said member is a lever arm.
6. The improvement of claim 2 wherein, the plane of rotation of said pulley is beyond the lateral limits of said pivot bearing.
7. The improvement of claim 2 wherein, said pulley is radially opposite of said attachment point in relation to said pivot bearing.
8. The improvement of claim 1 wherein said tensioner includes a base adapted to support an accessory.
9. A power transmission drive comprising:
a crankshaft pulley;
an accessory pulley;
a power transmission belt;
a power transmission belt tensioner having a tensioner pulley adapted to communicate with a surface of said power transmission belt, en arm supporting said tensioner pulley upon which said tensioner pulley is rotatably mounted via a pulley bearing, a shaft supporting said arm, said shaft rotatably supported by a pivot bearing, an attachment point for a strut, and said strut attached to said attachment point, said strut attachment point being laterally opposite of said pivot bearing in relation to the plane of rotation of said tensioner pulley, said strut attachment point forms part of a shield extending from a support for said pulley bearing, and said pulley and said attachment point laterally offset in relation to said pivot bearing such that a balance line passing through an axis of said attachment point and a center of said pulley intersects said shaft within a lateral limit of said pivot bearing, thereby substantially balancing said tensioner in terms of parasitic torque across said pivot bearing; and,
said power transmission belt trained about said crankshaft pulley, said accessory pulley and said tensioner pulley.
10. The power transmission drive of claim 9 further comprising, said strut attachment point being laterally opposite of said pulley in relation to the plane of rotation of said pivot bearing.
11. The power transmission drive of claim 10 further comprising said strut attachment point being beyond the lateral limits of said pivot bearing.
12. The power transmission drive of claim 10 further comprising, said strut attachment point forms part of a member extending from said shaft.
13. The power transmission drive of claim 12 further comprising, said member being a lever arm.
14. The power transmission drive of claim 10 further comprising the plane of rotation of said pulley being beyond the lateral limits of said pivot bearing.
15. The power transmission drive of claim 9 wherein said power transmission tensioner includes a base adapted to support an accessory.
16. A method of tensioning a power transmission belt comprising:
providing said power transmission belt,
providing a pivot bearing
providing a tensioner having a pulley adapted to communicate with a surface of said power transmission belt a supporting structure including a supporting shaft rotatably supported by said pivot bearing for supporting a supporting arm, said supporting arm for supporting said pulley, said pulley being rotatably mounted upon said supporting arm via a pulley bearing, said pulley being laterally offset in relation to said pivot bearing, and an attachment point for a strut, said attachment point for said strut forming part of a shield extending from a support for said pulley bearing, and said attachment point being laterally offset in relation to said pivot bearing, such that a balance line passing through an axis of said attachment point and a center of said pulley intersects said shaft within a lateral limit of said pivot bearing,
communicating a biasing force from said strut to said attachment point,
said supporting structure communicating said biasing force to said pulley through rotation about said pivot bearing, and
substantially balancing said biasing force at said pivot bearing in terms of parasitic torque.