Tensioner

Abstract

A tensioner comprising a base, a pivot arm pivotally mounted to the base, a spring disposed between the pivot arm and the base, an arcuate damping member engaged on one end of the spring, the arcuate damping member frictionally engaged with the base, a pulley journalled to the pivot arm on a shaft, the pivot arm comprising stamped metal and a rolled edge and one or more reinforcing ribs, and the spring and the shaft being laser welded to the pivot arm.

Claims

1. A tensioner comprising: a base; a pivot arm pivotally mounted to the base; a spring disposed between the pivot arm and the base; an arcuate damping member engaged on one end of the spring, the arcuate damping member frictionally engaged with the base; a pulley journalled to the pivot arm on a shaft; the pivot arm comprising stamped metal and a rolled edge and one or more reinforcing ribs; and the spring and the shaft being laser welded to the pivot arm.

2. The tensioner as in claim 1, wherein the spring is a torsion spring.

3. The tensioner as in claim 1, wherein the pivot arm further comprises protrusions for locating the spring and the shaft thereupon.

4. The tensioner as in claim 1, wherein the reinforcing ribs extend in a longitudinal direction on the pivot arm aligned on an axis A-A between the pulley and the base.

5. A tensioner comprising: a base; a pivot arm pivotally mounted to the base; a spring disposed between the pivot arm and the base; a damping member engaged on one end of the spring, the damping member frictionally engaged with the base; a pulley journalled to the pivot arm on a shaft; the pivot arm comprising stamped metal, and one or more reinforcing ribs, each reinforcing rib extends in a longitudinal direction on the pivot arm aligned on an axis between the pulley and the base; and the spring is laser welded to the pivot arm.

6. The tensioner as in claim 5, wherein the shaft is laser welded to the pivot arm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.

(2) FIG. 1 is a cross-section of the tensioner.

(3) FIG. 2 is a plan view of the pivot arm.

(4) FIG. 3 is a plan view of the pivot arm.

(5) FIG. 4 is a top perspective view of the pivot arm.

(6) FIG. 5 is a bottom perspective view of the pivot arm.

(7) FIG. 6 is a top perspective view of the tensioner.

(8) FIG. 7 is a top perspective view of the pivot arm.

(9) FIG. 8 is an exploded view.

(10) FIG. 9 is a perspective view of the damping member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(11) FIG. 1 is a cross-section of the tensioner. The inventive tensioner 100 comprises sheet metal for construct components and utilizes laser welding to bond certain components to reduce weight and cost while delivering good performance.

(12) Tensioner 100 comprises a base 10, pivot arm 20, spring 30 and pulley 40. Pivot arm 20 is pivotally attached to base 10 by shaft 21. Low friction bushing 27 is disposed between shaft 21 and base 10. Shaft 42 is preferably laser welded to pivot arm 20. Pulley 40 is mounted to shaft 42 on bearing 41. Dust covers 43, 44 prevent debris from entering bearing 41. Spring 30 is a torsion spring. Spring 30 urges pulley 40 toward a belt (not shown) to impart a load on the belt. The belt may be part of an engine accessory drive system (not shown) known in the art.

(13) An end 31 of spring 30 is connected to pivot arm 20. The other end 32 of spring 30 is connected to a damping member 50. Damping member 50 frictionally engages an inner surface 11 of base 10. Damping member 50 damps oscillatory movements of pivot arm 20 during operation of the tensioner.

(14) Pivot arm 20 for the tensioner is made from sheet steel plate using known stamping processes. To reduce the weight of the pivot arm, embossments or ribs are used to strengthen the pivot arm and to minimize the thickness of the sheet metal. The inventive stamped pivot arm replaces prior art cast pivot arms that are widely used in the tensioner arts.

(15) FIG. 2 is a plan view of the pivot arm. Ribs 22, 23, are stamped into pivot arm 20. Ribs 22, 23, may extend in a longitudinal direction of the pivot arm 20, roughly aligned on an axis A-A between pulley 40 and base 10. The depth or relief of each reinforcing rib is determined by the design requirements of the user. The number of ribs is also dependent on the operational requirements. The number of ribs may comprise one or more depending upon the design requirements.

(16) Dimples or protrusions 24 are stamped into pivot arm 20. Spring 30 is located on the pivot arm by dimples 24. Three dimples are shown in FIG. 2, but the number of dimples may vary depending on the operational requirements. Dimples 24 facilitate properly locating spring 30 on pivot arm 20 during the assembly process.

(17) Dimples or protrusions 25 are used to locate the position of shaft 42 on pivot arm 20. Dimples 25 are stamped into pivot arm 20. Three dimples are shown in FIG. 2, but the number of dimples may vary depending on the operational requirements. Dimples 25 facilitate properly locating shaft 42 on pivot arm 20 during the assembly process.

(18) FIG. 3 is a plan view of the pivot arm. Embossment or coining both may be used to create the dimples 24, 25, ribs 22, 23 and other aspects of this tensioner.

(19) Embossment is forming of sheet metal where the opposite side shows an opposite forming effect, for example, such as license plate numbers. Coining refers to sheet metal that is formed on one side without having any visible effects on the other side, for example, like currency coins. Both practices can be used for manufacture of this tensioner.

(20) FIG. 4 is a top perspective view of the pivot arm. Depending on the system requirements, spring 30 and shaft 42 may be on the same side or on opposite sides of pivot arm 20. Once spring 30 and shaft 42 are located on the pivot arm by the respective dimples, they are clamped and laser welded to pivot arm 20 at weld bead 450 and weld bead respectively. Laser welding provides for an accurate and strong bond at a reduced cost over the prior art. Spring 30 has a relatively high hardness while the sheet metal pivot arm 20 has a relatively low hardness. Even so, laser welding joins them without the adverse effect of large heat affected zones common for conventional stick type welding such as SMAW. Although laser welding is preferred, other embodiments using other welding processes, such as TIG, or mechanical joining may also be used. In alternate embodiments one or the other of shaft 42 or spring 30 is laser welded to pivot arm 20.

(21) A stamping process is used to roll edge 28 of pivot arm 20. Rolled edge 28 imparts additional stiffness to resist bending moments applied to the cantilever pivot arm 20. Edge 28 also imparts a finished edge to the pivot arm which contributes to the aesthetics of the tensioner. Rolled edge 28 may extend about the entire perimeter of pivot arm 20, or it can be limited to selected portions of pivot arm 20 as may be required by a user. Rolled edge 28 may be oriented toward either side of pivot arm 20 depending on the design requirements of a user.

(22) FIG. 5 is a bottom perspective view of the pivot arm. Ribs 22, 23 are embossed in pivot arm 20. Dimples or protrusions 24, 25 are also embossed. Coining may also be used to apply the ribs and dimples.

(23) FIG. 6 is a top perspective view of the tensioner. Base 10 can be stamped or die cast using aluminum or other known materials. For assembly, spring 30 with damping member 50 is assembled into base 10. Spring 30 is welded to pivot arm 20. Bearing 41 is pressed on to shaft 42. Pulley 40 is pressed on to bearing 41. Shaft 42 is welded to pivot arm 20.

(24) Pin 29 protruding from base 10 engages a hole in a mounting surface (not shown). Pin 29 prevents rotation of base 10 during operation, therefore acting as a reaction point for the spring force of spring 30.

(25) FIG. 7 is a top perspective view of the pivot arm. As an alternative to welding, clips 250 and 260 may be used to mechanically attach spring 30 and shaft 42 respectively to pivot arm 20. Clips 250 and 260 also serve to locate spring 30 and shaft 42.

(26) FIG. 8 is an exploded view. Damping member 50 comprises a frictional material 51 that frictionally engages inner surface 11. Damping member 50 further comprises an arcuate shoe 52 which is connected to end 32 of spring 30. Arcuate shoe 52 has a length of approximately 180 degrees about spring 30. Spring surface is ground flat for proper fitment and welding of the spring to pivot arm 20. Shaft 21 is press fit into pivot arm 20. Pulley 40 engages a belt in a belt driven accessory system (not shown).

(27) A fastener such as a bolt (not shown) extends through hole 210 in shaft 21 to mount the tensioner to a mounting surface (not shown).

(28) FIG. 9 is a perspective view of the damping member. Torsion spring 30 comprises flat surface 31. Surface 31 engages pivot arm 20. Damping member 50 engages end 32. Arcuate shoe 52 connected to end 32 of spring 30. Frictional material 51 is molded to shoe 52.

(29) Although forms of the invention have been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein. Unless otherwise specifically noted, components depicted in the drawings are not drawn to scale. Further, it is not intended that any of the appended claims or claim elements invoke 35 U.S.C. § 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim. The present disclosure should in no way be limited to the exemplary embodiments or numerical dimensions illustrated in the drawings and described herein.