EP4684146A2

EP4684146A2 - Axial damping tensioner

Info

Publication number: EP4684146A2
Application number: EP24775713.1A
Authority: EP
Inventors: Sangkyu Kim; Michael John KOPPESER; Nishanth Laxman KARKERA
Original assignee: Gates Corp
Current assignee: Gates Corp
Priority date: 2023-03-21
Filing date: 2024-03-21
Publication date: 2026-01-28
Also published as: WO2024197145A2; CN121079520A; WO2024197145A3

Abstract

A tensioner for a belt is provided that has independently adjustable forces that press a pulley into the belt and that provide a damping effect for the tensioner. The tensioner comprises a base bracket secured to, for example, an engine block, an arm rotatably engaged with the base bracket, and a pulley rotatably engaged with the arm. A bias member such as a spring is positioned between the arm and the base bracket, and the bias member generates a torsion force in response to an angular displacement where the torsion force presses the pulley into the belt. Then, the bias member generates an axis force in response to axial displacement where the axial force presses the arm into a damping bushing unit to generate a damping effect. Thus, these forces are independently adjustable, and the arrangement of components also reduces tilt between the arm and the base bracket.

Description

AXIAL DAMPING TENSIONER

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Serial No. 63/491,421 filed March 21, 2023, which is incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

The disclosure relates to a tensioner for a belt and pulley system that keeps the belt taut against the pulleys and also provides a damping function to reduce oscillations of components of the tensioner and reduce vibrations in the belt.

BACKGROUND OF THE INVENTION

Belt and pulley systems are used to transmit power from one pulley to one or more other pulleys via the belt. Moreover, belt and pulley systems are particularly useful for transmitting power among rotating components. Thus, a belt and pulley system is commonly incorporated in an internal combustion engine to transmit power from an output shaft of the engine to other components such as a compressor, a water pump, an alternator, etc. A tensioner is a component that presses a freely-rotating pulley into the belt to keep the belt taut against the other pulleys and to ensure an effective transmission of power. In addition, the tensioner can be selectively disengaged to allow the quick replacement of the belt. Tensioners can also provide a damping function to reduce oscillations of components of the tensioner and absorb vibrations in the belt caused by changes in the transmission and reception of power through the belt, movements among the components, and other sources of vibration.

In some prior art tensioners, a spring is used to drive the pulley into the belt, and the same spring is used to drive a friction plate into a housing of the tensioner to provide a damping function. An example of such a prior art device is shown in U.S. Patent No. 5,632,697, which is incorporated herein in its entirety by reference. In this arrangement, the force generated by the spring to drive the pulley and the force generated by the spring to press the friction plate are both dependent on the angular displacement of the spring. This arrangement of components inhibits the functionality of the tensioner as any choice that impacts the ability of the spring to drive the pulley necessarily changes the damping function, and vice versa. In addition, the use of a friction plate in this manner causes uneven wear on the friction plate and the housing of the tensioner, which causes some components to tilt out of alignment. This tilt causes further uneven wear. To address the wear, some components of the tensioner may be replaced or the entire tensioner may be replaced, otherwise a user risks a catastrophic failure of the ability of the belt and pulley system to transmit power. Thus, the arrangement of components in prior art devices results in functionality that is difficult to adjust as well as an uneven wear and tilt that create an additional expense and risk for a user.

SUMMARY OF THE INVENTION

Embodiments of the present disclosure address these and other shortcomings of prior art tensioners. In particular, the tensioner of the present disclosure provides a torsion force that presses a pulley into a belt and an axial force that dampers movement of the tensioner, and these forces are independently adjustable to easily control the performance of the tensioner. Moreover, the tensioner of the present disclosure better resists any tilting between an arm and a base bracket of the tensioner to improve the performance and longevity of the tensioner.

It is one aspect of the present disclosure to provide a tensioner that generates a torsion force and an axial force that are independently adjustable. In some embodiments, the tensioner has a base bracket secured to, for example, an engine block, an arm that articulates about the base bracket, and a pulley at a distal end of the arm that presses into a belt to keep the belt taut. A spring is operably engaged with the base bracket and the arm to control the movement between the base bracket and the arm. Specifically, the spring coils, or uncoils, to generate a torsion force, which rotates the arm and presses the pulley into a belt. The torsion force is a function of a torsion spring constant and the angular displacement of the spring. Then, the spring is compressed in an axial direction to generate an axial force, which presses the arm into a damping bushing unit for a damping effect. The axial force is a function of an axial spring constant and the axial displacement of the spring. Since the torsion force depends on angular displacement and the axial force depends on axial displacement, which is distinct from angular displacement, the torsion force and the axial force are independently adjustable to easily control the performance of the tensioner. For instance, in some embodiments, an increase in the axial force of a spring is desired to change the damping effect of the tensioner without changing the torsion force, which dictates the force and the torque that the pulley of the tensioner imposes on the belt. Accordingly, a spring is selected with a longer, uncompressed axial length but with no other changes that would affect other aspects of the spring. Thus, when the spring is compressed and installed with other components, the spring generates a larger axial force to change the damping effect of the tensioner, however, the torsion spring constant and the angular displacement of the spring remain unchanged. Therefore, the torsion force generated by the spring remains unaffected by the change in length of the spring, or affected by only an unsubstantial amount.

It is a further aspect of the present disclosure to provide a tensioner that better resists tilting of an arm relative to a damping bushing unit and a base bracket of the tensioner. Tilting is typically caused by a belt force, and several aspects of the present disclosure contribute to the resistance of tilting, including the manner in which the arm engages a damping bushing unit, which is joined to the base bracket. Specifically, a shoulder of the arm engages a flange of the damping bushing unit in a damping engagement area, and a bore of the arm engages a body of the damping bushing unit in a rotational engagement area. The damping engagement area has a planar shape like a washer that is oriented perpendicular to axes of the damping bushing unit and the base bracket. The rotational engagement area has a cylindrical shape that is centered about these axes and extends along these axes. Having a damping engagement area that is separate from the rotational engagement area with a different shape resists tilting of the arm.

In particular, the relative locations of the engagement areas help resist tilt. A force from the belt is, in some embodiments, directed through the rotational engagement area, and the arm is urged to tilt about this force relative to the damping bushing unit and the base bracket. With the damping engagement area separate from the rotational engagement area and extending farther in a lateral direction, the damping engagement area resists the force and the tilting of the arm. In various embodiments, the damping engagement area is located proximate to an upper end of the rotational engagement area. This arrangement is supported by a bias member that drives the shoulder of the arm into the flange of the damping bushing unit with an axial force that promotes the alignment of the arm and further resists tilting of the arm relative to the damping bushing unit and the base bracket. In some embodiments, the axial force can be selected to be larger than any belt force that would tilt the arm to better resist tilting of the arm. This arrangement also results in more even wear between the arm and the damping bushing unit, and the more even wear preserves the alignment of the arm relative to the damping bushing unit and the base bracket. In addition, with the damping engagement area separate from the rotational engagement area, any wear between contact surfaces in the damping engagement area has less of an effect on the tilting of the arm.

The rotational engagement area also serves many functions. The rotational engagement area can include a small gap between the inner surface of the bore of the arm and the outer surface of the body of the damping bushing unit. The smaller the gap, the less freedom of the arm, in particular the bore, has to tilt relative to the damping bushing unit and the base bracket. Further still, with the belt force directed through the rotational engagement area, the rotational engagement area can better resist tilting than if the belt force were directed in another direction, for instance, above the upper end of the rotational engagement area or below the lower end of the engagement area.

The rotational engagement area can also provide some damping effect on the oscillations of the arm relative to the damping bushing unit and the base bracket. With a smaller gap in the rotational engagement area between the bore of the arm and the body of the damping bushing unit and/or the material selections of the bore and the body, there may be some engagement and frictional forces in the rotational engagement area. Thus, as the arm moves relative to the damping bushing unit and the base bracket, the rotational engagement area may contribute to the resistance of this movement and the damping effect described herein.

It is another aspect of the present disclosure to provide a tensioner with fewer parts compared to prior art tensioners to improve the performance and longevity of the tensioner while reducing the cost of manufacturing the tensioner. With prior art tensioners, a friction plate, a backing plate, and other components are required to provide the damping effect due to the arrangement of components in prior art tensioners. With the change in arrangement of components in the present disclosure, the friction plate and the backing plate are eliminated. Further, other plates and bushings are combined into a damping bushing unit, which can be one or two components as described herein. A reduction in the number of parts simplifies the tensioner and reduces the number of potential points of failure to improve the performance and longevity of the tensioner. A first aspect of the present disclosure is to provide a tensioner for a belt, comprising an arm configured to rotate about an axis of a base bracket, the arm having a bore and a shoulder; a bias member extending from a first end to a second end, wherein the first end is engaged with the arm, and the second end is engaged with the base bracket; and a damping bushing unit joined with the base bracket and at least partially positioned in the bore of the arm, wherein the shoulder of the arm and a flange of the damping bushing unit are configured to engage each other in a damping engagement area, and the bias member is configured to drive the shoulder of the arm into the flange of the damping bushing unit in a direction parallel to the axis of the base bracket to generate a damping torque in the damping engagement area.

The tensioner of the first aspect may include, optionally, a body of the damping bushing unit that is configured to engage the bore of the arm in a rotational engagement area to allow the arm to rotate about the base bracket.

The tensioner of the first aspect may include one or more of the previous embodiments and, optionally, that the damping engagement area has a planar shape that is substantially perpendicular to the axis of the base bracket, and the rotational engagement area has a cylindrical shape that is substantially centered about the axis of the base bracket.

The tensioner of the first aspect may include one or more of the previous embodiments and, optionally, that the damping bushing unit comprises a shaft made of a first material; and a ring disposed around at least part of an outer surface of the shaft, wherein the ring is made of a second material that is distinct from the first material.

The tensioner of the first aspect may include one or more of the previous embodiments and, optionally, that the damping bushing unit is a single, continuous structure made of a plastic material.

The tensioner of the first aspect may include one or more of the previous embodiments and, optionally, that a lower end of the damping bushing unit comprises an annular-shaped recess, and the base bracket comprises a cylindrical-shaped protrusion, wherein the protrusion is configured to press fit into the recess to join the damping bushing unit with the base bracket.

The tensioner of the first aspect may include one or more of the previous embodiments and, optionally, a mount fastener extends through a threaded aperture of the damping bushing unit and into a threaded portion of the base bracket to join the damping bushing unit with the base bracket.

A second aspect of the present disclosure is to provide a tensioner for a belt, comprising an arm configured to rotate about an axis of a base bracket, the arm having a bore and a shoulder; a damping bushing unit joined with the base bracket and at least partially positioned in the bore of the arm, wherein the shoulder of the arm and a flange of the damping bushing unit are configured to engage each other in a damping engagement area, and a body of the damping bushing unit is configured to engage the bore of the arm in a rotational engagement area to allow the arm to rotate about the axis of the base bracket; and wherein the damping engagement area has a planar shape that is substantially perpendicular to the axis of the base bracket, and the rotational engagement area has a cylindrical shape that is substantially centered about the axis of the base bracket.

The tensioner of the second aspect may include, optionally, a pulley rotatably engaged with the arm and configured to press into a belt, wherein the pulley comprises a plurality of bearings oriented in a plane that is substantially parallel to the damping engagement area.

The tensioner of the second aspect may include one or more of the previous embodiments and, optionally, that the plane extends through the rotational engagement area.

The tensioner of the second aspect may include one or more of the previous embodiments and, optionally, that the plane is offset from the damping engagement area by a predetermined distance.

The tensioner of the second aspect may include one or more of the previous embodiments and, optionally, a bias member extending from a first end to a second end, wherein the first end is engaged with the arm, and the second end is engaged with the base bracket, wherein the bias member is configured to drive the shoulder of the arm into the flange of the damping bushing unit in a direction parallel to the axis to generate a damping torque in the damping engagement area, and wherein a diameter of the bias member is less than an outer diameter of the damping engagement area and greater than an inner diameter of the damping engagement area.

The tensioner of the second aspect may include one or more of the previous embodiments and, optionally, that the body of the damping bushing unit descends from the flange such that the damping engagement area is located proximate to an upper end of the rotational engagement area.

The tensioner of the second aspect may include one or more of the previous embodiments and, optionally, that the bias member is a helical spring disposed about the bore of the arm and the body of the damping bushing unit.

A third aspect of the present disclosure is to provide a tensioner for a belt, comprising an arm configured to rotate about an axis of a base bracket; a damping bushing unit joined with the base bracket, wherein the damping bushing unit secures the arm to the base bracket; and a spring extending between a first end engaged with the arm and a second end engaged with the base bracket, wherein the spring is configured to exert a torsion force in response to an angular displacement of the spring between the arm and the base bracket, and the spring is configured to exert an axial force in response to an axial displacement of the spring between the arm and the damping bushing unit, wherein the torsion force and the axial force are independently adjustable.

The tensioner of the third aspect may include, optionally, a pulley rotatably engaged with the arm and configured to press into a belt, wherein the pulley comprises a plurality of bearings oriented in a plane that is substantially parallel to a damping engagement area where a shoulder of the arm and a flange of the damping bushing unit are configured to engage each other, wherein the axial force generates a damping torque in the damping engagement area.

The tensioner of the third aspect may include one or more of the previous embodiments and, optionally, that the plane extends through a rotational engagement area where a bore of the arm and a body of the damping bushing unit are configured to engage each other to allow the arm to rotate about the base bracket.

The tensioner of the third aspect may include one or more of the previous embodiments and, optionally, that the damping engagement area has a planar shape that is substantially perpendicular to the axis of the base bracket, and the rotational engagement area has a cylindrical shape that is substantially centered about the axis of the base bracket.

The tensioner of the third aspect may include one or more of the previous embodiments and, optionally, that the body of the damping bushing unit descends from the flange such that the damping engagement area is located proximate to an upper end of the rotational engagement area. The tensioner of the third aspect may include one or more of the previous embodiments and, optionally, that a diameter of the spring is less than an outer diameter of the damping engagement area and greater than an inner diameter of the damping engagement area.

The phrases "at least one", "one or more", and "and/or", as used herein, are open- ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B, or C", "one or more of A, B, and C", "one or more of A, B, or C" and "A, B, and/or C" means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

Unless otherwise indicated, all numbers expressing quantities, dimensions, conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about."

The term "a" or "an" entity, as used herein, refers to one or more of that entity. As such, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein.

The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Accordingly, the terms "including," "comprising," or "having" and variations thereof can be used interchangeably herein. The use of “engaged with” and variations thereof herein is meant to encompass any direct or indirect connections between components.

It shall be understood that the term "means" as used herein shall be given its broadest possible interpretation in accordance with 35 U.S.C. § 112(f). Accordingly, a claim incorporating the term "means" shall cover all structures, materials, or acts set forth herein, and all of the equivalents thereof. Further, the structures, materials, or acts and the equivalents thereof shall include all those described in the summary of the invention, brief description of the drawings, detailed description, abstract, and claims themselves.

These and other advantages will be apparent from the disclosure of the invention(s) contained herein. The above-described embodiments, objectives, and configurations are neither complete nor exhaustive. The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present disclosure. Moreover, references made herein to "the present invention", or aspects thereof should be understood to mean certain embodiments of the present invention/disclosure and should not necessarily be construed as limiting all embodiments to a particular description. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detailed Description, particularly when taken together with the drawings.

It is to be appreciated that any feature or aspect described herein can be claimed in combination with any other feature(s) or aspect(s) as described herein, regardless of whether the features or aspects come from the same described embodiment.

Any one or more aspects described herein can be combined with any other one or more aspects described herein. Any one or more features described herein can be combined with any other one or more features described herein. Any one or more embodiments described herein can be combined with any other one or more embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Those of skill in the art will recognize that the following description is merely illustrative of the principles of the disclosure, which may be applied in various ways to provide many different alternative embodiments. This description is made for illustrating the general principles of the teachings of this disclosure and is not meant to limit the inventive concepts disclosed herein.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of the invention.

Fig. l is a side elevation view of a pulley system in accordance with an embodiment of the present disclosure;

Fig. 2 is a perspective view of the tensioner in accordance with an embodiment of the present disclosure;

Fig. 3 is a cross-sectional view of the tensioner in Fig. 2 taken along line A-A in accordance with an embodiment of the present disclosure; Fig. 4 is a perspective, exploded view of a tensioner in accordance with an embodiment of the present disclosure;

Fig. 5 is a perspective view of a damping bushing unit in accordance with an embodiment of the present disclosure;

Fig. 6A is a perspective view of a spring in an uncompressed state in accordance with an embodiment of the present disclosure;

Fig. 6B is a perspective view of the spring in Fig. 6A in a compressed state in accordance with an embodiment of the present disclosure;

Fig. 7 is a cross-sectional view of the tensioner in Fig. 2 taken along line B-B in accordance with an embodiment of the present disclosure;

Fig. 8 is another cross-sectional view of the tensioner in Fig. 2 taken along lien B- B in accordance with an embodiment of the present disclosure;

Fig. 9 is a cross-sectional view of another tensioner in accordance with an embodiment of the present disclosure; and

Fig. 10 is a cross-sectional view of a further tensioner in accordance with an embodiment of the present disclosure.

It should be understood that the drawings are not necessarily to scale, and various dimensions may be altered. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein.

2 Belt System

4 Main Crank Pulley

6a, 6b, 6c Pulley

8 Belt

10 Tensioner

12 Base Bracket

14 Center (Base Bracket)

16 Pulley

18 Center (Pulley)

20 Length (Center to Center)

22 Axis (Center to Center)

24a Tensioner Force 24b Belt Force

25a Tensioner Torque

25b Belt Torque

26 Angle (Force to Axis) 28 Arm

30 Spring

32 First End

34 Radius

35 Protrusion 36 Torsion Force

37 Recess

38 Cap

40 Fastener

42 Damping Bushing Unit 44 Shaft

46 Ring

48 Bore

49 Axis (Bore)

50 Flange 51 Axis (Base Bracket)

52 Contact Surface (Flange)

54 Body

56 Contact Surface (Body)

58 Axis (Damping Bushing Unit) 60 Diameter (Body)

62 Second End

64 Initial Length

66 Installed Length

68 Shoulder 70 Contact Surface (Shoulder)

71 Damping Engagement Area

72 Contact Surface (Bore)

73 Rotational Engagement Area 74 Axial Force

75a Upper End

75b Lower End

76 Belt Force

78 Inner Diameter

80 Inner Collar

82 Space

84 Protrusion

86 Inner Diameter

88 Outer Diameter

90 Bearing

92 Plane

94 Hub Load Distance

96 Mount Fastener

DETAILED DESCRIPTION

Although the following text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of the description is defined by the words of the claims set forth at the end of this disclosure. The Detailed Description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment of the tensioner would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. Additionally, any combination of features shown in the various figures can be used to create additional embodiments of the present disclosure. Thus, dimensions, aspects, and features of one embodiment of the tensioner can be combined with dimensions, aspects, and features of another embodiment of the tensioner to create the claimed embodiment.

Fig. 1 shows a pulley system 2 that transmits power from an internal combustion engine to other components. Specifically, a main crank pulley 4 is connected to an output shaft of the internal combustion engine, and the main crank pulley 4 turns a belt 8. Then, the belt 8 drives other pulleys 6a-6c to power other components such as a compressor, a water pump, an alternator, etc. The belt 8 is generally sized to fit along the path around these pulleys 4, 6a-6c. However, to ensure the effective transmission of power through the belt 8, a tensioner 10 is provided to press a pulley 16 into the belt 8 to keep the belt 8 taut against the other pulleys 4, 6a-6c. Another benefit of a tensioner 10 is that it can be selectively disengaged to loosen the belt 8 and allow the easy removal and replacement of the belt 8. Once the new belt 8 is in place, the tensioner 10 is reengaged to keep the belt 8 taut. The tensioner 10 keeps the belt 8 taut as the various pulleys 4, 6a-6c change speeds, when there is slight movement among the pulleys 4, 6a-6c, and even if the belt 8 stretches and increases in size over time.

The tensioner 10 comprises a base bracket 12 that is secured to, for example, an engine block of a vehicle. One end of an arm 28 is rotatably engaged with the base bracket 12, and the pulley 16 is rotatably engaged at an opposing end of the arm 28. Thus, the pulley 16 freely rotates against the belt 8, and the pulley 16 and the arm 28 are rotatable about the base bracket 12. As described herein, the operable engagement between the arm 28 and the base bracket 12 presses the pulley 16 against the belt 8 to keep the belt 8 taut and also provides a damping function to absorb any oscillations in the arm 28 or vibrations in the belt 8.

A spring (30 in Fig. 3) that forms part of the operable engagement between the arm 28 and the base bracket 12 generates a torsion force (36 in Fig. 3), which produces a tensioner torque 25a to rotate the arm 28 and press the pulley 16 into the belt 8 with a tensioner force 24a. The belt 8 resists the tensioner force 24a with an opposing belt force 24b, which imposes a belt torque 25b on the operable engagement between the arm 28 and the base bracket 12. During operation, these forces and torques are in balance, and to the extent the forces and torques are out of balance, the tensioner 10 functions to provide the necessary responsive forces and torques as well as a damping function.

The geometry of the tensioner 10 and the pulley system 2 dictates these forces and torques. A center 14 of the base bracket 12 and a center 18 of the pulley 16 are oriented along an axis 22, and these centers 14, 18 are offset by a length 20. The belt force 24b forms an angle 26 with the axis 22. The belt torque 25b caused by the belt force 24b can be expressed as:

Tb = (Fb)(L)(Sin(A)) (1) where Fb is the belt force 24b, L is the center-to-center length 20, and A is the angle 26 of the belt force 24b.

Fig. 2 is a perspective view of the tensioner 10. The base bracket 12 is secured to an engine block or other structure, and the pulley 16 freely rotates against the belt. An arm 28 spans the base bracket 12 and the pulley 16, and the arm 28 is operably engaged with the base bracket 12 and the pulley 16. Lines A-A and B-B are also depicted in Fig. 2.

Fig. 3 is a cross-sectional view of the tensioner 10 taken along line A-A in Fig. 2. The spring 30 is part of the operable engagement between the arm 28 and the base bracket 12 where a first end 32 of the spring 30 engages the arm 28, a second end (62 in Figs. 6A- 6B) engages the base bracket 12, and the one or more coils of the spring 30 are spaced apart from the center 14 of the base bracket 12 by a radius 34. The spring 30 has an initial angular displacement before installation in the tensioner 10, and the spring 30 is installed and applied to a belt with a different angular displacement, either coiled or uncoiled, to produce a torsion force 36. The tensioner torque Tt (25a in Fig. 1) generated by the spring 30 is:

Tt = (Ft)(R) (2) where Ft is the torsion force 36, and R is the radius 34. Thus, where the tensioner torque Tt (25a in Fig. 1) and the belt torque Tb (25b in Fig. 1) are in balance and Tt = Tb, Equations 1 and 2 can be written as:

(F_b)(L)(Sin(A)) = (Ft)(R) (3)

The tensioner torque Tt (25a in Fig. 1) generated by the spring 30 according to Equation 2 can also be written as:

Tt = (kt)(O) (4) where 0 is the angular displacement, in the form of coiling or uncoiling, of the spring 30, and kt is a torsion spring constant that depends on physical characteristics of the spring 30. As the pulley 16 and the arm 28 articulate about the base bracket 12, the angular displacement 9 changes, and thus, the tensioner torque Tt (25a in Fig. 1) generated by the spring 30 changes. Combining Equations 2 and 4 and solving for the torsion force Ft, 36 yields:

Ft = ((kt)(0))/R (5)

Thus, the torsion force Ft, 36 is a function of angular displacement 0. As described herein, this aspect of the spring 30 is independent from an axial force generated by the spring 30, which depends on the axial displacement of the spring 30 rather than angular displacement. In this way, the overall functionality of the tensioner 10 can be easily adjusted among a wider range of possibilities and with more accuracy and precision.

Finally, Fig. 3 shows a protrusion 35 of the base bracket 12 that extends into a recess 37 of the arm 28. The protrusion 35 is configured to contact the arm 28 at each end of the recess 37 to define the limits of rotational motion between the base bracket 12 and the arm 28.

Fig. 4 is a perspective, exploded view of the various components of the tensioner 10. A fastener 40 and a cap 38 join the pulley 16 to one end of the arm 28 where the pulley 16 freely rotates relative to the arm 28. An opposing end of the arm 28 comprises a bore 48, which has a cylindrical shape and extends along an axis 49, and the bore 48 is part of the operable engagement between the arm 28, a damping bushing unit 42, and the base bracket 12. Generally, the spring 30 is disposed around the bore 48. Then, the damping bushing unit 42 joins the arm 28 and the base bracket 12, and the arm 28 is rotatable about an axis 51 of the base bracket 12. In addition, the spring 30 is compressed between the arm 28 and the base bracket 12 as the damping bushing unit 42 is joined to the base bracket 12. In this embodiment, the damping bushing unit 42 comprises a joint shaft 44 and a ring 46 that is positioned around the joint shaft 44. As described herein, this tensioner 10 has fewer components, and the components work together to provide a torsion force and an axial force that are independently adjustable.

Fig. 5 is a perspective view of a damping bushing unit 42. As set forth above, the damping bushing unit 42 has a pivot shaft 44 with a ring 46 disposed around the pivot shaft 44. With this arrangement, the pivot shaft 44 can be made of a material that is sufficiently strong, dense, or have other characteristics that make the pivot shaft 44 suitable to provide structure to the damping bushing unit 42. Then, the ring 46 can be made of a material that is optionally distinct from the material of the pivot shaft 44 to be more suitable for a frictional engagement with other components to serve the various functions described herein. In some embodiments, the ring 46 can be a plastic material that is overmolded onto a metal pivot shaft 44. However, it will be appreciated that the present disclosure encompasses embodiments where the damping bushing unit 42 is a single structure made of a single material such as plastic. Optionally, the components 44, 46 may be aluminum, another metal, carbon fiber, another composite material, Teflon®, etc.

Generally, the damping bushing unit 42 comprises a flange 50 and a body 54 where the outer diameter of the flange 50 is greater than the outer diameter of the body 54, and the length of the flange 50 along an axis 58 is less than the length of the body 54, though the damping bushing unit 42 is not necessarily limited to these relationships. The flange 50 has one contact surface 52 that engages a shoulder of the arm, and the body 54 has another contact surface 56 that engages a bore of the arm. These contact surfaces 52, 56 have different orientations. In this embodiment, the contact surface 52 on the underside of the flange 50 has a planar shape that is oriented substantially perpendicular to the axis 58 of the damping bushing unit 42, and the contact surface 56 has a cylindrical shape that is centered about the axis 58 and can be described as oriented parallel to the axis 58.

The axis 58 of the damping bushing unit 42, the axis of the bore of the arm (49 in Fig. 4), and the axis of the base bracket (51 in Fig. 4) are generally co-linear. However, over time components can wear and then the axis of the arm (49 in Fig. 4) may be urged to tilt out of alignment with the axis of the base bracket (51) and the axis 58 of the damping bushing unit 42. The arrangement of components of the tensioner of the present disclosure to resist this tilt is described in further detail herein.

Figs. 6A and 6B show a spring 30 in an uncompressed state and a compressed state, respectively. The spring 30 extends from a first end 32 to a second end 62. In Fig. 6A, the spring 30 is uncompressed and has an initial length 64. In Fig. 6B, the spring 30 is compressed to an installed length 66, or the length of the spring 30 once installed with the first end 32 engaged with the arm (28 in Fig. 1) and the second end 62 engaged with the base bracket (12 in Fig. 1). The engagement, in some embodiments, is the first end 32 contacting a stop or other similar structure of the arm and the second end 62 contacting a stop or other similar structure of the base bracket. In the compressed state, the spring 30 generates an axial force F_a according to the equation:

Fa = (k_a)(AL) (6) where k_a is an axial spring constant that depends on physical characteristics of the spring 30, and AL is the change in length of the spring 30 or the difference between the uncompressed length 64 and the compressed length 66. As described herein, the change in axial force F_a depends on the change in length of the spring 30, which is independent from the change in torsion force Ft that depends on the change in angular displacement 0.

The spring 30 can be more broadly described as a bias member, which may include, but is not limited to, other solid structures, air bags, leaf springs, helical springs, hydraulic systems, pneumatic systems, etc. Moreover, while the spring 30 has a helical shape from the first end 32 to the second end 62, the present disclosure encompasses embodiments with other shapes. For example, the spring 30 may terminate with a ring or loop at either end 32, 62 where the ring or loop is oriented perpendicular to one or more axes described herein (49, 51 in Fig. 4; 58 in Fig. 5) to more evenly transmit forces to the arm (28 in Fig. 1) and/or the base bracket (12 in Fig. 1). Further still, in various embodiments, the spring 30 has a linear response to displacement in the axial and/or angular directions, and/or the spring 30 has a non-linear response to displacement in the axial and/or angular directions.

Fig. 7 is a cross-sectional view of the operable engagement between the arm 28, the damping bushing unit 42, and the base bracket 12 taken along line B-B of Fig. 2 that provides a torque and force to keep the belt taut and dampen vibrations. The spring 30 is disposed between the base bracket 12 and the arm 28. Then, the damping bushing unit 42 is joined to the base bracket 12 to hold the components in the arrangement shown in Fig. 7. Due to the axial compression of the spring 30, the spring 30 generates an axial force 74 that drives a shoulder 68 of the arm 28 into the flange 50 of the damping bushing unit 42. Therefore, a contact surface 70 of the shoulder 68 engages the contact surface 52 of the flange 50 in a damping engagement area 71, and this engagement creates the damping function for the tensioner.

The damping engagement area 71 is centered on the axes 49, 51, 58 of the bore 48, the base bracket 12, and the damping bushing unit 42 and has a planar, annular shape like a washer. Further, the planar shape of the damping engagement area 71 is oriented substantially perpendicular to the axes 49, 51, 58 to provide several benefits of the present disclosure including resisting tilt of the arm 28. During operation, the friction between contact surfaces 52, 70 in the damping engagement area 71 is enhanced by the axial force 74 to resist the motion of the arm 28 relative to the base bracket 12 and to absorb vibrations in the belt. In various embodiments, the axial force 74 is between approximately 500N and 3,000N. In some embodiments, the axial force 74 is approximately l,000N.

Next, a contact surface 56 of the body 54 of the damping bushing unit 42 and a contact surface 72 of a bore 48 of the arm 28 selectively engage each other in a rotational engagement area 73 to help limit the motion of the arm 28 relative to the base bracket 12 to a rotational motion. This rotational engagement area 73 has a cylindrical shape that is centered on the axes 49, 51, 58, and, therefore, can be described as parallel to the axes 49, 51, 58. These contact surfaces 56, 72 can be sized to have a relatively small gap therebetween that allows the arm 28 to rotate about the base bracket 12 while minimizing the amount of tilt that the arm 28 will have relative to the base bracket 12 in the presence of forces that drive the arm 28 out of alignment with the base bracket 12. This gap can be defined as the difference between an inner diameter 78 defined by the contact surface 72 of the bore 48 of the arm 28 and the outer diameter (60 in Fig. 5) of the body (54 in Fig. 5) of the damping bushing unit 42.

With separate damping and rotational engagement areas 71, 73, the tensioner 10 can have independently adjustable axial and torsion forces to make adjusting the functionality of the tensioner 10 far easier than in prior art designs. In addition, the rotational engagement area 73 may optionally contribute to the damping effect of the tensioner depending on the size of the gap between the damping bushing unit 42 and the bore 48. With a small or even no gap, and with materials that have a high coefficient of friction, engagement between the contact surfaces 56, 72 in the rotational engagement area 73 can resist rotational movement of the arm 28 relative to the base bracket 12 and contribute to the damping effect.

Fig. 7 also depicts a belt force 76 caused by the engagement between the pulley and the belt. This belt force 76 is typically the source of wear and tilt of the arm 28 with respect to the base bracket 12, and the arm 28 is urged to tilt about the belt force 76. In some embodiments, the belt force 76 depicted in Fig. 7 may be the same belt force (24b in Fig. 1) described elsewhere herein. In various embodiments, the belt force 76 depicted in Fig. 7 may be a component of the belt force (24b in Fig. 1) described elsewhere herein alone or in combination with other forces. In some embodiments, the belt force 76 is less than approximately 500N. The relative locations of the engagement areas 71, 73 help resist tilt of the arm 28. Specifically, having a separate damping engagement area 71 with a different shape that extends farther in a lateral direction than the rotational engagement area 73 helps constraint movement of the arm 28 and resist tilt of the arm 28. Moreover, since the axial force 74 drives the shoulder 68 into the flange 50, the axial force 74 and the damping engagement area 71 hold the arm 28 in alignment with the damping bushing unit 42 and the base bracket 12 to reduce the tilt and uneven wear of the components of the tensioner. Further still, the axial force 74 can be larger than the belt force 76 to resist tilt and hold the arm 28 in alignment with the damping bushing unit 42 and the base bracket 12. In some embodiments, the axial force 74 is approximately three times larger than the belt force 76.

In addition, with the damping engagement area 71 that produces the damping effect located away from the rotational engagement area 73, the contact surface 56 of the body 54 of the damping bushing unit 42 and the contact surface 72 of the bore 48 of the arm 28 are less prone to wear overall, and less prone to uneven wear as well. Thus, the tensioner of the present disclosure has less tilt and improved longevity.

Fig. 8 is also a cross-sectional view of the operable engagement between the arm 28 and the base bracket 12 taken along line B-B of Fig. 2. Here, the damping bushing unit 42 is joined to the base bracket 12 to compress the spring 30 and hold the other components as shown. The damping bushing unit 42 has a body 48 as well as a collar 80 extending downwardly to define an annular-shaped space 82 therebetween. The base bracket 12 comprises a cylindrical-shaped protrusion 84 that extends upward and is configured to press into the space 82 in an interference fit that is strong enough to resist any axial forces generated by the spring 30 or any other forces that the tensioner might experience during operation. In some embodiments, the protrusion 84 tapers to a smaller diameter as the protrusion 84 extends upward, and the annular space 82 has a corresponding taper to help center the damping bushing unit 42 on the base bracket 12.

Fig. 9 shows a cross-sectional view of an embodiment of a tensioner 10. The damping engagement area 71 between the contact surface (52 in Fig. 7) of the flange (50 in Fig. 7) of the damping bushing unit 42 and the contact surface (70 in Fig. 7) of the shoulder (68 in Fig. 7) of the arm 28 extends between an inner diameter 86 and an outer diameter 88 about the axes 49, 51, 58 of the bore 48, the base bracket 12, and the damping bushing unit 42. With these diameters 86, 88, a damping torque to resist movement of the arm 28 can be calculated as: Td = (Fa)(Di + D₀)(p)/2 (7) where F_a is the axial force 74 generated by the spring 30, Di is the inner diameter 86 of the damping engagement area 71, D_o is the outer diameter 88 of the damping engagement area 71, and p is a friction coefficient that depends on the materials of the contact surfaces (52, 70 in Fig. 7) in the damping engagement area 71. Further, the radius 34 of the spring 30 is a predetermined distance from the axes 49, 51, 58 and dictates where the axial force 74 presses the arm 28 into the damping bushing unit 42. In some embodiments, the axial force 74 is directed through the damping engagement area 71 of the contact surfaces (52, 70 in Fig. 7) to keep any wear in the damping engagement area 71 evenly distributed. In other words, the radius 34 is less than half of the outer diameter 88 and greater than half of the inner diameter 86. Further alternatively, the diameter of the spring 30 (twice the radius 34) is less than the outer diameter 88 and greater than the inner diameter 86.

Fig. 9 also shows the pulley 16 that is rotatable about a set of bearings 90 that are aligned in a plane 92, which dictates the where the belt force 76 causes the arm 28 to tilt. This plane 92 is offset from the damping engagement area 71 in an axial direction by an offset distance 94. Thus, the damping engagement area 71 as buttressed by the axial force 74 can help constraint movement of the arm 28 and resist tilt of the arm 28.

The arrangement of the belt force 76 and the rotational engagement area 73 also helps resist tilt of the arm 28. The plane 92 and belt force 76 extend through the rotational engagement area 73 between the contact surface (56 in Fig. 7) of the body of the damping bushing unit 42 and the contact surface (72 in Fig. 7) of the bore of the arm 28, specifically, between an upper end 75a and a lower end 75b of the rotational engagement area 73. This aspect keeps the contact surfaces (56, 72 in Fig. 7) in balance to reduce wear, to help make any wear even in nature, and to reduce the tilt of the arm 28 relative to the base bracket 12 as both the portion of the rotational engagement area 73 above the belt force 76 and the portion of the rotational engagement area 73 below the belt force 76 can resist tilt. With these aspects defined, the anti-tilting effect of the arrangement according to the present disclosure can be expressed as a dimensionless ratio:

Anti-Tilting Effect = ((F_a)( Di + D₀))/(4(Fb)(L₀)) (8) where F_a is the axial force 74 generated by the spring 30, Di is the inner diameter 86, Do is the outer diameter 88, Fb is the belt force 76, and L_o is the offset 94 between the bearing plane 92 and the damping engagement area 71. A prior art tensioner would have smaller diameters 86, 88 and no axial force 74, and thus, a smaller anti-tilting effect.

Figs. 9 and 10 show alternative embodiments for mounting the damping bushing unit 42 to the base bracket 12. In Fig. 9, a mount fastener 96 extends through the damping bushing unit 42 and into the base bracket 12. In Fig. 10, the damping bushing unit 42 is press fit into the base bracket 12, and the shaft 44 of the damping bushing unit 42 extends to a bottom surface of the base bracket 12.

While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. However, it is to be understood that such modifications and alterations are within the scope and spirit of the present disclosure, as set forth in the following claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various ways. It is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

Claims

CLAIMS What is claimed is:

1. A tensioner for a belt, comprising: an arm configured to rotate about an axis of a base bracket, the arm having a bore and a shoulder; a bias member extending from a first end to a second end, wherein the first end is engaged with the arm, and the second end is engaged with the base bracket; and a damping bushing unit joined with the base bracket and at least partially positioned in the bore of the arm, wherein the shoulder of the arm and a flange of the damping bushing unit are configured to engage each other in a damping engagement area, and the bias member is configured to drive the shoulder of the arm into the flange of the damping bushing unit in a direction parallel to the axis of the base bracket to generate a damping torque in the damping engagement area.

2. The tensioner of claim 1, further comprising: a body of the damping bushing unit that is configured to engage the bore of the arm in a rotational engagement area to allow the arm to rotate about the base bracket.

3. The tensioner of claim 2, wherein the damping engagement area has a planar shape that is substantially perpendicular to the axis of the base bracket, and the rotational engagement area has a cylindrical shape that is substantially centered about the axis of the base bracket.

4. The tensioner of claim 1, wherein the damping bushing unit comprises: a shaft made of a first material; and a ring disposed around at least part of an outer surface of the shaft, wherein the ring is made of a second material that is distinct from the first material.

5. The tensioner of claim 1, wherein the damping bushing unit is a single, continuous structure made of a plastic material.

6. The tensioner of claim 1, wherein a lower end of the damping bushing unit comprises an annular-shaped recess, and the base bracket comprises a cylindrical-shaped protrusion, wherein the protrusion is configured to press fit into the recess to join the damping bushing unit with the base bracket.

7. The tensioner of claim 1, wherein a mount fastener extends through a threaded aperture of the damping bushing unit and into a threaded portion of the base bracket to join the damping bushing unit with the base bracket.

8. A tensioner for a belt, comprising: an arm configured to rotate about an axis of a base bracket, the arm having a bore and a shoulder; a damping bushing unit joined with the base bracket and at least partially positioned in the bore of the arm, wherein the shoulder of the arm and a flange of the damping bushing unit are configured to engage each other in a damping engagement area, and a body of the damping bushing unit is configured to engage the bore of the arm in a rotational engagement area to allow the arm to rotate about the axis of the base bracket; and wherein the damping engagement area has a planar shape that is substantially perpendicular to the axis of the base bracket, and the rotational engagement area has a cylindrical shape that is substantially centered about the axis of the base bracket.

9. The tensioner of claim 8, further comprising: a pulley rotatably engaged with the arm and configured to press into a belt, wherein the pulley comprises a plurality of bearings oriented in a plane that is substantially parallel to the damping engagement area.

10. The tensioner of claim 9, wherein the plane extends through the rotational engagement area.

11. The tensioner of claim 9, wherein the plane is offset from the damping engagement area by a predetermined distance.

12. The tensioner of claim 8, further comprising: a bias member extending from a first end to a second end, wherein the first end is engaged with the arm, and the second end is engaged with the base bracket, wherein the bias member is configured to drive the shoulder of the arm into the flange of the damping bushing unit in a direction parallel to the axis to generate a damping torque in the damping engagement area, and wherein a diameter of the bias member is less than an outer diameter of the damping engagement area and greater than an inner diameter of the damping engagement area.

13. The tensioner of claim 8, wherein the body of the damping bushing unit descends from the flange such that the damping engagement area is located proximate to an upper end of the rotational engagement area.

14. The tensioner of claim 8, wherein the bias member is a helical spring disposed about the bore of the arm and the body of the damping bushing unit.

15. A tensioner for a belt, comprising: an arm configured to rotate about an axis of a base bracket; a damping bushing unit joined with the base bracket, wherein the damping bushing unit secures the arm to the base bracket; and a spring extending between a first end engaged with the arm and a second end engaged with the base bracket, wherein the spring is configured to exert a torsion force in response to an angular displacement of the spring between the arm and the base bracket, and the spring is configured to exert an axial force in response to an axial displacement of the spring between the arm and the damping bushing unit, wherein the torsion force and the axial force are independently adjustable.

16. The tensioner of claim 15, further comprising: a pulley rotatably engaged with the arm and configured to press into a belt, wherein the pulley comprises a plurality of bearings oriented in a plane that is substantially parallel to a damping engagement area where a shoulder of the arm and a flange of the damping bushing unit are configured to engage each other, wherein the axial force generates a damping torque in the damping engagement area.

17. The tensioner of claim 16, wherein the plane extends through a rotational engagement area where a bore of the arm and a body of the damping bushing unit are configured to engage each other to allow the arm to rotate about the base bracket.

18. The tensioner of claim 17, wherein the damping engagement area has a planar shape that is substantially perpendicular to the axis of the base bracket, and the rotational engagement area has a cylindrical shape that is substantially centered about the axis of the base bracket.

19. The tensioner of claim 17, wherein the body of the damping bushing unit descends from the flange such that the damping engagement area is located proximate to an upper end of the rotational engagement area.

20. The tensioner of claim 16, wherein a diameter of the spring is less than an outer diameter of the damping engagement area and greater than an inner diameter of the damping engagement area.