Tensioner, optionally with asymmetric high-damping-ratio

Abstract

A tensioner is provided and includes a base and a pivot shaft, a tensioner arm pivotally mounted to the pivot shaft, a pulley assembly, a helical torsion spring positioned to urge the tensioner arm into a belt, and a radial damping mechanism. The spring has a first helical end to transfer force with the base, and a second helical spring end to transfer force with the tensioner arm. The damping mechanism includes a damping member in a surrounding relationship with the spring, and a push block. The push block has a first end face and a second end face and is positioned between a spring end and the base or the tensioner arm, and is moveable. The forces on the two end faces are applied at different radii, causing the push block to pivot radially outwardly to press the damping member to increase a friction force generated thereby.

Description

TENSIONER, OPTIONALLY WITH ASYMMETRIC HIGH-DAMPING-RATIOCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Chinese patent application No. 202311728554.9, filed on December 15, 2023, the contents of which are incorporated herein in their entirety.TECHNICAL FIELD

[0002] The present disclosure belongs to the technical field of tensioners for engine accessory systems, and in particular to an asymmetric high-damping-ratio tensioner.BACKGROUND

[0003] Currently, symmetric damping tensioners available on the market are commonly used, and such tensioners have the same damping in both loading and unloading directions. Asymmetric damping tensioners feature high damping during loading and low damping during unloading. Due to violent engine vibrations and high accessory loads of commercial vehicles, high-damping and high-tension symmetric damping tensioners are usually required without application of engine accessory vibration isolation products, thereby leading to high costs. Asymmetric damping tensioners can be used to overcome the above defect. Moreover, during acceleration and deceleration, a symmetric damping tensioner may cause belt jumping or slipping, while asymmetric damping can achieve quick unloading with low damping during acceleration and smooth loading with high damping during deceleration. Therefore, within a certain range, a higher damping ratio contributes greater improvement to an engine FEAD system (NVH).

[0004] A Chinese patent with the application No. CN201310344488.5 discloses a tension pulley with an asymmetric damping mechanism. A damping principle of the tension pulley is as follows: a first force is a spring contact force generated by contact between a bent part of an end portion of a spring and a contact column on a swing arm in a process of twisting the spring, a second force is an acting force generated by contact between the end portion of the spring and a receiving groove of a damping element, a third force is a normal reaction force acting on a first friction surface of the damping element, a fourth force is a tangential friction force acting on the first friction surface, and a fifth force is an orthogonal reaction force acting on the damping element that isgenerated by contact between a damping bracket inclined surface and a contact inclined surface of a third support of the swing arm and transmitted to the damping element. The damping characteristics of the tension pulley 10 are achieved by forming a resultant force which is the third force, of the second and fifth forces at an angle and then generating a friction damping force that is the fourth force. An asymmetric damping coefficient depends on specific friction forces generated during loading and unloading the swing arm in different rotation directions.

[0005] At least some prior art tensioners have one or more of the following defects: 1) A torsional spring primarily bears a positive force in a torsional direction, and in addition to the positive force in the torsional direction, a tangential force generated by contact between a damping block and the swing arm is generated, which may reduce the lifespan and durability of the spring; 2) a friction surface of the damping element may be too small, thereby adversely affecting durability; 3) since the friction force is not fully converted by a torsional force of the spring, variation in the friction force may be small, thereby resulting in a small damping ratio during loading and unloading; and 4) the damping block and a damping ring may not be conducive to molding and assembly. As a result, at least some tensioners of the prior art do not meet high-damping-ratio and durability requirements for the asymmetric damping tensioners or durability requirements for some symmetric damping tensioners.SUMMARY

[0006] In view of the above problems and technical needs, the present disclosure provides tensioner that is optionally an asymmetric high-damping-ratio tensioner. The tensioner is capable of meeting asymmetric damping requirements for both loading and unloading directions, and on this basis, a damping ratio can be adjusted to achieve operation at a high damping ratio.

[0007] In an embodiment, a tensioner for tensioning an endless drive member on an engine, comprising a base and a pivot shaft that is mountable to a stationary member; a tensioner arm pivotally mounted to the pivot shaft for pivoting movement about a tensioner arm pivot axis; a pulley assembly rotatably mounted to the tensioner arm and positioned for engagement with the endless drive member; a tensioner spring that is a helical torsion spring, positioned to urge the tensioner arm into the endless drive member, wherein the spring has a first helical end and a second helical end, wherein the first helical spring end is positioned to transfer force with a first spring end force transfer surface onthe base and the second helical spring end is positioned to transfer force with a second spring end force transfer surface on the tensioner arm; and a radial damping mechanism that includes a damping member positioned in a surrounding relationship with the tensioner spring, and a push block, wherein the push block has a first end face and a second end face spaced from the first end face by a selected angular spacing, wherein the push block is positioned between one of the first and second helical spring ends and one of the first and second spring end force transfer surfaces on one of the base and the tensioner arm, and wherein the damping member is frictionally engaged with a friction surface on the other of the base and the tensioner arm during pivotal movement of the tensioner arm relative to the base, wherein the push block is moveable relative to the damping member, and wherein a first radial center of engagement between the first end face of the push block and the tensioner spring is at a first radius relative to the tensioner arm pivot axis, resulting, in use, in a first force at the first radius, and wherein a second radial center of engagement between the second end face of the push block and the one of the first and second spring end force transfer surfaces is at a second radius relative to the tensioner arm pivot axis, resulting, in use, in a second force at the second radius, wherein the second radius is smaller than the first radius so as to induce a pivoting movement of the push block radially outward into engagement with the damping member, thereby driving the damping member into engagement with the friction surface so as to generate a push block generated frictional damping force.

[0008] In some embodiments, a technical solution of the present disclosure is as follows: An asymmetric high-damping-ratio tensioner, including a rocker arm, a base, a pivot shaft, a pulley assembly, a radial damping mechanism and an axial damping mechanism, wherein a pulley seat and a rotating support are respectively arranged at both ends of the rocker arm, a shaft hole at a core of the rotating support is configured for mounting the pivot shaft, a multi-circle annular stepped groove is formed on a front face of the rotating support, the radial damping mechanism is arranged in the annular stepped groove, the axial damping mechanism is arranged on a back face of the rotating support, the base is connected to the front face of the rotating support through the pivot shaft, and the cylindrical base encloses the radial damping mechanism; when the base is mounted and fixed, the rocker arm rotates around the pivot shaft clockwise for loading or counterclockwise for unloading, and a damping force is generated due to friction between the radial damping mechanism and an inner side of the base as the rocker arm rotates, where the damping force during loading is greater than that during unloading; and thepulley assembly is rotatably mounted on the pulley seat, an outer side of the pulley assembly is pressed on a belt to tighten the belt, the pulley assembly rotates with movement of the belt, and changes in tightness of the belt drive the rocker arm to rotate clockwise or counterclockwise.

[0009] In the above solution, an acting force between the belt and the pulley assembly is a force that drives the rocker arm to rotate, and the damping force of rotation of the rocker arm comes from the radial damping mechanism and the axial damping mechanism, where the damping force of the axial damping mechanism remains constant regardless of whether the rocker arm rotates clockwise or counterclockwise. The damping force during loading when the rocker arm rotates clockwise is significantly greater than the damping force during unloading when the rocker arm rotates counterclockwise, and therefore quick unloading with low damping during acceleration and smooth loading with high damping during deceleration can be achieved.

[0010] Further, the radial damping mechanism includes a torsional spring, a damping ring, a damping sleeve, a push block and an accommodating groove, the annular stepped groove is coaxially arranged with the pivot shaft and includes a first step, a second step and a third step that descend from inside to outside, the torsional spring is arranged on the second step, a downwardly recessed fan-shaped accommodating groove is formed on a step plane between the first step and the second step, the push block is correspondingly embedded in the accommodating groove, both end faces of the push block point radially, the torsional spring is mounted on the second step, an upper end of the torsional spring is fixedly connected to an inner bottom surface of the base, the other end of the torsional spring is pressed tightly against an end face of the push block, under the action of a torque of the torsional spring, the other end face of the push block is pressed tightly against an end face of the accommodating groove, the damping ring is arranged on an outer side of the torsional spring, the damping sleeve is arranged on an outer side of the damping ring, both the damping ring and the damping sleeve are arranged on the third step, a thrust of the torsional spring on the push block is FA, a pressing force of the push block against the end face of the accommodating groove is FR, and when the rocker arm drives the torsional spring to load, a resultant force of FA and FR drives the push block to press against the damping ring and the damping sleeve radially outward to increase the damping force. When an end portion of the torsional spring continues to tightly press against the push block, and the push block remains stationary in a circumferential direction, since the push block is also fan-shaped, theextrusion forces FA and FR acting on both end faces of the push block can form the resultant force to push the fan-shaped push block radially outward, and the push block then applies the resultant force to the damping ring and the damping sleeve.

[0011] Further, the end face of the accommodating groove is only partially pressed against the end face of the push block, part of the first step corresponding to the accommodating groove is tightly pressed against the push block, and a clearance notch is formed between the second step and the push block, indicating that the second step and the end face of the push block are not in contact with each other. The end face of the accommodating groove is arranged to tightly press against part of the push block, such that a contact surface between the accommodating groove and the push block is reduced and a friction force is reduced, thereby preventing the push block from being obstructed during radial expansion outward. A distance L from an axis to a force bearing point of tightly pressing against the end face of the accommodating groove is actually a force arm of FR, and when the force arm L is smaller, FR increases accordingly.

[0012] Further, an inner side surface of the push block is of a circular arc shape coaxial with the pivot shaft, an outer side surface of the push block is of an arc shape, a width of the push block gradually decreases from one end to the other end, and a spacing between the push block and the damping ring continuously widens from a wide end to a narrow end of the push block. The push block is arranged to be approximately wedge-shaped, when the push block expands outward, a force bearing point on an outer side of the push block can be optimized, and compared with a uniform circular arc-shaped force bearing surface, a force bearing range is reduced, and a pressure at the force bearing point increases, such that the damping force is adjusted more flexibly.

[0013] Further, the base and the rotating support are rotatably connected by means of the pivot shaft, the pivot shaft and the base are integrally formed, two limiting blocks are arranged on an outer housing of the base, an outer edge of the rotating support is vertically tilted outward and provided with a limiting handle, the limiting handle can only move between the two limiting blocks, and the limiting handle limits a rotation angle of the rocker arm.

[0014] Further, the damping sleeve is nested on the outer side of the damping ring, a plurality of positioning holes are formed in the damping ring, a plurality of positioning protrusions in one-to-one correspondence with the positioning holes are arranged on an inner side of the damping sleeve, a push block holder is arranged inwardly at a bottom ofthe damping sleeve, a recess is formed in a middle of the push block, and the push block holder is correspondingly embedded in the recess.

[0015] Further, a groove is formed in a bottom end face of the damping ring, a clamping block is arranged on a peripheral surface of the second step, the groove and the clamping block are clamped by means of concave and convex limiting, and the damping ring rotates synchronously with rotation of the rotating support.

[0016] Further, the damping ring is made of a rigid material, the damping sleeve is made of a flexible elastic material, and an outer side of the damping sleeve is attached to an inner wall of the base.

[0017] Further, the axial damping mechanism includes a thrust washer and a fixed washer, a bushing is arranged on an outer side of the pivot shaft, the thrust washer is sleeved on an outer side of the bushing, an inner end face of the thrust washer abuts against the back face of the rotating support, the fixed washer is arranged on an outer end face of the thrust washer, the fixed washer tightly presses the thrust washer and the rotating support, and the torsional spring tightly presses against the thrust washer axially.

[0018] Further, the pulley assembly includes a dust cover, a pulley bolt and a pulley, a bearing positioning seat is arranged on the pulley seat, the pulley is rotatably mounted on the bearing positioning seat, the pulley bolt penetrates through a core of the pulley from outside and is connected to the bearing positioning seat, and the dust cover is mounted outside the pulley bolt by means of press fitting.

[0019] Beneficial effects of the present disclosure include a push block embedded in the rotating support of the tensioner, both end faces of the push block point radially, one end face of the push block receives an acting force FA applied by an end portion of the torsional spring, the other end face of the push block presses against the end face of the accommodating groove to generate the reaction force FR, and under the combined action of FA and FR, the push block can press outward radially, and the outer side surface of the push block tightly presses against the damping ring, the damping sleeve and the inner wall of the base to generate a damping force; and the tensioner of the present disclosure achieves its use purpose through only one movable push block, and the tensioner has a simple structure, without need to increase manufacturing costs, thereby being highly economical.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is an overall external view of a tensioner of the present disclosure.

[0021] Figure 2 illustrates a positional relationship between a torsional spring and a push block in a tensioner of the present disclosure.

[0022] Figure 3 is a mounting diagram of a damping ring and a damping sleeve in a tensioner of the present disclosure.

[0023] Figure 4 is a positioning diagram of a damping ring and an annular stepped groove in a tensioner of the present disclosure.

[0024] Figure 5 is an assembly diagram of an annular stepped groove and a push block in a tensioner of the present disclosure.

[0025] Figure 6 is a diagram of an internal structure of a base.

[0026] Figure 7 is an exploded diagram of an overall structure of a tensioner of the present disclosure.

[0027] Figure 8 is a sectional view of an overall structure of a tensioner of the present disclosure.

[0028] Figure 9 is a structural diagram of internal components of a tensioner of the present disclosure.

[0029] Figure 10 is a force bearing diagram of a push block of the present disclosure.

[0030] Figure 11 is a plan view of the tensioner when moving in a loading direction.

[0031] Figure 12 is a plan view of the tensioner when moving in an unloading direction.DETAILED DESCRIPTIONS OF THE EMBODIMENTS

[0032] The present disclosure is further described below with reference to accompanying drawings and examples.

[0033] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiment or embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to theexemplary implementations and techniques illustrated in the drawings and described below.

[0034] The terms ‘comprising’ and ‘including’ and their various conjugations (e.g. ‘comprises’) will be understood to be inclusive and open-ended, and not exclusive. This means that if an element A includes or comprises an element B, it will be understood that element A could include or comprise other elements in addition to including or comprising element B. The term ‘having’ and its various conjugations are also to be understood as being open-ended in the same way as ‘comprising’ and ‘including’. These terms are not to be interpreted to exclude the presence of other features, steps or components.

[0035] As used herein, the terms “about” and “approximately” are meant to cover variations that may exist in the upper and lower limits of the ranges of values, such as variations in properties, parameters, and dimensions.

[0036] Various terms used throughout the present description may be read and understood as follows, unless the context indicates otherwise: "or" as used throughout is inclusive, as though written "and / or"; singular articles and pronouns as used throughout include their plural forms, and vice versa; similarly, gendered pronouns include their counterpart pronouns such that pronouns should not be understood as limiting anything described herein to use, implementation, performance, etc. by a single gender; "exemplary" should be understood as "illustrative" or "exemplifying" and not necessarily as "preferred" over other embodiments. Further definitions for terms may be set out herein; these may apply to prior and subsequent instances of those terms, as will be understood from a reading of the present description. It will also be noted that the use of the term "a" or "an" will be understood to denote "at least one" in all instances unless explicitly stated otherwise or unless it would be understood to be obvious that it must mean "one".

[0037] Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, "each" refers to each member of a set or each member of a subset of a set.

[0038] As used in this document, "attached" in describing the relationship between two connected parts includes the case in which the two connected parts are "directlyattached" with the two connected parts being in contact with each other, and the case in which the connected parts are "indirectly attached" and not in contact with each other, but connected by one or more intervening other part(s) between.

[0039] As used in this document, terms describing relative positions of elements such as ‘top’, ‘upper’, ‘bottom’, ‘lower’, or other analogous terms will be understood to refer to the placement of the described element during use of the apparatus of which it is a part unless the context would make it clear that it is otherwise. It will be understood that the aforementioned placement of an element, for example, can still be considered its placement even when the object that it is a part of is lying in some position other than the position in which it will be used. As an example, if reference is made to a device having an upper member, it will be understood that the upper member is being described as having an upper position when the device that it is a part of is in use or is in position for use, unless the context would make it clear that it is otherwise. Further to this example, it will be understood that the aforementioned upper member of the object can still be considered its upper member even when the object is lying on its side, for storage, or for transport, or for some other reason.

[0040] The embodiments of the disclosures described herein are exemplary (e.g., in terms of materials, shapes, dimensions, and constructional details) and do not limit by the claims appended hereto and any amendments made thereto. Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the following examples are only illustrations of one or more implementations. The scope of the disclosure, therefore, is only to be limited by the claims appended hereto and any amendments made thereto.

[0041] As illustrated in the figures, an asymmetric high-damping-ratio tensioner 10 of the present disclosure includes a base 2 and a pivot shaft 22, a rocker arm 1 (also referred to as a tensioner arm 1) pivotally mounted to the pivot shaft 22, a pulley assembly 5 rotatably mounted to the tensioner arm 1 , a tensioner spring 31 , which may be helical torsion spring, a radial damping mechanism 3, and an optionally provided axial damping mechanism 4 (that may be omitted). A pulley seat 11 and a pivot support 12 are respectively arranged at both ends of the rocker arm 1 . A shaft hole 13 at a core of the pivot support 12 is configured for pivotally mounting the pivot support 12 (and therefore the rocker arm 1 ) to the pivot shaft 22. A multi-circle annular stepped groove 14 may be formed on a front face of the pivot support 12. The radial damping mechanism 3 may be arranged in the annular stepped groove 14, and the axial damping mechanism 4 maybe arranged on a back face of the pivot support 12. The pivot shaft 22 and the base 2 may be two separate elements that are fixedly joined together, or alternatively may be monolithically formed. Two limiting blocks 21 are arranged on an outer housing of the base 2 to limit movement of the tensioner arm 1 in an unloading direction (i.e. a direction of decreased loading on the tensioner spring 31 , shown at DU in Figure 12), and in a loading direction (i.e. a direction of increased loading on the tensioner spring 31 , shown at DL in Figure 11 ). The tensioner arm 1 moves in the unloading direction when the tension in the belt 99 decreases. The tensioner arm 1 moves in the loading direction when the tension in the belt 99 increases. An outer edge of the pivot support 12 may be vertically tilted outward and provided with a limiting handle 15. The limiting handle 15 can only move between the two limiting blocks 21 , and so the limiting handle 15 limits a rotation angle of the rocker arm 1 .

[0042] The pivot shaft 22 is fixedly mounted to the base 2. The cylindrical base 2 encloses the radial damping mechanism 3. The base 2 is mounted to a fixed element of a vehicle such as an engine block (not shown) and thus, the base 2 and the pivot shaft 22 may be said to be mountable to a stationary member. A shaft bolt 1018 may extend through the base 2 and the pivot shaft 22 and may enter a threaded aperture (not shown) in the engine block (not shown). A locating projection 1016 on the base 2 may engage an locating aperture (not shown) in the engine block (not shown) to ensure that the base 2 does not pivot as a result of force applied by the tensioner spring 31 thereon during operation.

[0043] The pivot support 12 is pivotally connected to the pivot shaft 22 for pivoting movement about a tensioner arm pivot axis A. The rocker arm 1 may pivot in any suitable rotational direction during loading and unloading (i.e. when being moved as a result of increasing tension in an endless drive member 99 (an example of which is shown as a belt in Figure 8) or when moving the endless drive member 99 as a result of decreasing tension in the endless drive member 99). In the example shown, the rocker arm 1 pivots around the pivot shaft 22 clockwise for loading and counterclockwise for unloading (from the viewpoint of a person facing the tensioner 10 mounted to the stationary member), and a damping force is generated due to friction between the radial damping mechanism 3 and an inner face (shown at 60) of the base 2 as the rocker arm 1 pivots. The inner surface 60 may be referred to as a friction surface 60 as the radial damping mechanism employs a damping member 1001 that is in frictional engagement with the friction surface 60 to generate a damping force. The damping force generatedthereby may be referred to as a frictional damping force. The damping force during loading may be greater than that during unloading.

[0044] For convenience the endless drive member 99 will be referred to as a belt 99 but it will be understood that it could be any other suitable type of endless drive member.

[0045] The tensioner spring 31 acts between the base 2 and the tensioner arm 1 and biases the tensioner arm 1 in the unloading direction so as to counteract the load applied by the belt 12 on the pulley assembly 5. The tensioner spring 31 is positioned to urge the tensioner arm 1 into the endless drive member 99. The tensioner spring 31 has a first helical end 1002 and a second helical end 1004. The first helical spring end 1002 is positioned to transfer force with a first spring end force transfer surface 1006 (Figure 2) on the base 2 and the second helical spring end 1004 is positioned to transfer force with a second spring end force transfer surface 1008 on the tensioner arm 1 . The first spring end force transfer surface 1006 is shown in isolation in Figure 2, however it will be understood that is may be a surface that is formed directly into the base 2.

[0046] The radial damping mechanism 3 includes a damping member 1001 , which may optionally include a damping ring 32 and a damping sleeve 33, and a push block 34.

[0047] The push block 34 fits in an accommodating groove 144, which contains the second spring end force transfer surface 1008. The annular stepped groove 14 is coaxially arranged with the pivot shaft 22 and includes a first step 141 , a second step 142 and a third step 143 that step progressively radially. The torsional spring 31 may be arranged on the second step 142. The accommodating groove 144 may be formed on a step plane between the first step 141 and the second step 142 and may be recessed fan-shaped. The push block 34 has first and second end faces 1010 and 1012 which may extend radially. Broadly worded, the push block 34 is positioned between one of the first and second helical spring ends 1002 and 1004 and one of the first and second spring end force transfer surfaces 1006 and 1008 on one of the base 2 and the tensioner arm 1. The push block 34 may be made from any suitable material, such as a suitable metal, via a powdered metal forming process.

[0048] The first helical spring end 1002 of the torsional spring 31 may be engaged with a bottom inner surface of the base 2 (the first spring end force transfer surface 1006). The second helical spring end 1004 may be engaged with the first end face 1010 of the push block 34, under the action of a torque of the torsional spring 31 . The second end face 1012 of the push block 34 may be pressed tightly against an end face of the accommodating groove 144 (the second spring end force transfer surface 1008).

[0049] The damping member 1001 is positioned in a surrounding relationship with the tensioner spring 31 . The damping ring 32 is arranged on an outer side of the torsional spring 31 , the damping sleeve 33 is arranged on an outer side of the damping ring 32. Both the damping ring 32 and the damping sleeve 33 may be arranged on the third step 143. A first force of the torsional spring 31 on the push block 34 is shown at FA, and a corresponding second force FR is applied by the second spring end force transfer surface 1008 on the push block 34. The first force FA is applied at a first radial center of engagement CFA between the first end face 1010 of the push block 34 and the tensioner spring 31 . The second force FR is applied at a second radial center of engagement CFR between the second end face 1012 of the push block 34 and the aforementioned one of the first and second spring end force transfer surfaces 1006 and 1008.

[0050] As can be seen in Figure 11 , the first force FA and the second force FR which are circumferentially directed, result in a net force that urges the push block 34 radially outward thereby pushing the push block 34 radially outward. Additionally, as can be seen in Figure 11 , it will be noted that the first radial center of engagement is at a first radius R1 relative to the tensioner arm pivot axis A, resulting in the first force FA being applied at the first radius. Similarly, the second radial center of engage is positioned at a second radius R2 relative to the tensioner arm pivot axis A, resulting in the second force FR being applied at the second radius R2. The second radius R2 is smaller than the first radius R1 . The first and second forces FA and FR apply first and second torques to the push block 34. Because the second radius R2 is smaller than the first radius R1 , the first and second torques result in a net torque TN on the push block 34 driving the push block 34 to pivot outwardly about a push block pivot point 1020 that is a radially outer corner of the second spring end force transfer surface 1008. The urging of the push block 34 radially outward as a result of the forces FA and FR and as a result of the torques, results in a normal force applied by the damping member 1001 on the friction surface 60, and thus a push block generated frictional damping force FFPB.

[0051] As shown in Figure 11 , during movement of the tensioner arm 1 in the loading direction, a pivoting spring torque is applied to the tensioner spring 31 as a result of the circumferentially directed forces applied to it on its first and second helical spring ends 1002 and 1004 by the base 2 and the push block 34. This pivoting spring torque drives the tensioner spring 31 into engagement with the damping member 1001 thereby driving the damping member 1001 into engagement with the friction surface 60 so as to generate a tensioner spring torque generated frictional damping force FFTS. Worded differently,the first and second helical spring ends 1002 and 1004 of the tensioner spring 31 are positioned such that the circumferentially directed forces applied to the first and second helical ends 1002 and 1004 through the push block 34 and through the other of the base 2 and the tensioner arm 1 (in the example shown, through the push block 34 and through the base 2) generate a pivoting spring torque on the tensioner spring, so as to drive the tensioner spring into engagement with the damping member thereby driving the damping member into engagement with the friction surface 60 so as to generate a tensioner spring torque generated frictional damping force FFTS.

[0052] As shown in Figure 12, during movement of the tensioner arm 1 in the unloading direction, the first and second helical spring ends 1002 and 1004 of the tensioner spring 31 are again positioned such that forces applied to the first and second helical ends 1002 and 1004 through the push block 34 and through the other of the base 2 and the tensioner arm 1 (in the example shown, through the push block 34 and through the base 2) generate the pivoting spring torque on the tensioner spring, so as to drive the tensioner spring 31 into engagement with the damping member 1001 thereby driving the damping member 1001 into engagement with the friction surface 60 so as to generate the tensioner spring torque generated frictional damping force FFTS

[0053] Because of the relative difference in the forces FR and FA when the tensioner arm 1 moves in the unloading direction as compared to the forces FR and FA when the tensioner arm 1 moves in the loading direction (the second force FR grows and the first force FA is reduced as compared to when the tensioner arm 1 is moving in the loading direction, the first and second torques result in a relatively smaller net torque TN on the push block 34 driving the push block 34 to rotate outwardly, as compared to the net torque when the tensioner arm 1 moves in the loading direction. As a result, the smaller net torque TN on the push block 34 results in a smaller normal force applied by the damping member 1001 on the friction surface 60 than is applied when moving in the loading direction, and thus a smaller push block generated frictional damping force FFPB, than is applied when moving in the loading direction. As a result, the frictional damping force that is applied to the tensioner arm 1 during movement in the loading direction is higher than the frictional damping force that is applied during movement in the unloading direction. Accordingly, the damping of the tensioner 10 is asymmetric. In tests of a tensioner constructed in accordance with the present disclosure, the damping ratio has been found to be improved.

[0054] In a specific example shown in Figure 9, the second spring end force transfer surface 1008 in the accommodating groove 144 extends radially only partway along the second end face 1012 of the push block 34, and a clearance notch 1422 is formed between the second spring end force transfer surface 1008 and the second end face 1012 of the push block 34.

[0055] Optionally, an inner side surface of the push block 34 is of a circular arc shape coaxial with the pivot shaft 22, and an outer side surface of the push block 34 is of an arc shape. A thickness of the push block 34 optionally gradually decreases from one end to the other end, and a spacing between the push block 34 and the damping ring 32 thereby optionally widens from a wide end to a narrow end of the push block 34.

[0056] In the above example, the end face of the accommodating groove 144 is arranged to tightly press against part of the push block 34, such that a contact surface between the accommodating groove 144 and the push block 34 is reduced and a friction force is reduced, thereby reducing the likelihood of the push block 34 from being obstructed during radial movement outward.

[0057] The pulley assembly 5 is rotatably mounted on the pulley seat 11 , an outer side of the pulley assembly 5 is pressed on the belt 99 (Figure 9) to tighten the belt 99. As is known in the art, the pulley assembly 5 rotates with movement of the belt 99. The tension in the belt 99 drives the rocker arm 1 to rotate in the loading or unloading directions. The pulley assembly 5 includes a dust cover 51 , a pulley bolt 52 and a pulley 53, a bearing positioning seat 54 is arranged on the pulley seat 11 , the pulley 53 is rotatably mounted on the bearing positioning seat 54, the pulley bolt 52 penetrates through a core of the pulley 53 from outside and is connected to the bearing positioning seat 54, and the dust cover 51 covers the pulley bolt 52. While the pulley assembly 5 is shown in more detail in many figures, only an outer ring of the pulley 53 is shown in Figures 11 and 12, for visual simplicity.

[0058] The damping ring 32 may be made of a first material such as a suitable metal, while the damping sleeve 33 may be made of a second material that is softer than the first material, and may be any material such as a polymeric material. An outer side of the damping sleeve 33 is engaged with the inner wall 60 of the base 2. A plurality of positioning holes 321 are formed in the damping ring 32, a plurality of positioning protrusions in one-to-one correspondence with the positioning holes 321 are arranged on an inner side of the damping sleeve 33. In an embodiment, the damping sleeve 33 is overmolded on the damping ring 32. A push block holder 331 may be positionedinwardly on the damping sleeve 33 for projecting into a recess 341 in the push block 34. The push block holder 331 may include a boss that engages a boss receiving groove 322 a radial / circumferential face of the damping ring 32, so as to loosely hold the push block 34 to the damping ring 1001 during assembly of the tensioner 10. One or more tabs 1014 that extend inwardly from the damping ring 32 may support a face 1015 of the push block 34 that is opposite the recess 341 so as to hold the push block 34 movably to the damping member 1001 . Clearance is provided between the push block holder 331 and the surrounding walls 1017 of the recess 341 (Figure 6) to ensure that the push block 34 is movable relative to the damping member 1001. A locating projection block 1421 may be positioned on a peripheral surface of the second step 142. The boss receiving groove 322 and the clamping block 1421 are clamped by means of concave and convex limiting, and the damping ring 32 rotates synchronously with rotation of the pivot support 12.

[0059] The axial damping mechanism 4 includes a thrust washer 42 and a fixed washer 43, a bushing 41 is arranged on an axial end of the pivot shaft 22, the thrust washer 42 is sleeved on a radially outer side of the bushing 41. An inner end face of the thrust washer 42 abuts against a back face of the pivot support 12. The fixed washer 43 is arranged on an outer end face of the thrust washer 42, the fixed washer 43 tightly presses the thrust washer 42 and the pivot support 12, and the torsional spring 31 urges the pivot support 12 against the thrust washer 42 axially.

[0060] The present disclosure, when incorporating the optional axial damping mechanism 4, includes a ‘double’ damping structure, since a damping force of rotation of the rocker arm 1 comes from both the radial damping mechanism 3 and the axial damping mechanism 4. The damping force of the axial damping mechanism 4 remains constant regardless of whether the rocker arm 1 rotates clockwise or counterclockwise. Asymmetric damping characteristics are achieved by the radial damping mechanism 3.

[0061] An operating principle of the tensioner 10 of the present disclosure is described as follows:

[0062] The foregoing descriptions are merely preferred implementations of the present disclosure, and are not intended to limit the protection scope of the present disclosure. Any equivalent substitutions and changes made by a person skilled in the art easily within the technical scope disclosed in the present disclosure shall fall within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

[0063] Reference numerals in the figures: Tensioner 10, rocker arm 1 , pulley seat 11 , pivot support 12, shaft hole 13, annular stepped groove 14, first step 141 , second step 142, clamping block 1421 , clearance notch 1422, third step 143, accommodating groove 144, limiting handle 15, base 2, limiting block 21 , pivot shaft 22, radial damping mechanism 3, torsional spring 31 , damping ring 32, positioning hole 321 , groove 322, damping sleeve 33, push block holder 331 , push block 34, recess 341 , axial damping mechanism 4, bushing 41 , thrust washer 42, fixed washer 43, pulley assembly 5, dust cover 51 , pulley bolt 52, pulley 53, and bearing positioning seat 54, endless drive member / belt 99, inner face 60 of base 2, damping member 1001 , first helical end 1002, second helical end 1004, first spring end force transfer surface 1006, second spring end force transfer surface 1008, first end face 1010 of the push block 34, second end face 1012 of the push block 34, face of push block 34, locating projection 1016 on base 2, surrounding walls 1017 of recess 341 , shaft bolt 1018, push block pivot point 1020.

Claims

CLAIMSWhat is claimed is:1 . A tensioner for tensioning an endless drive member on an engine, comprising a base and a pivot shaft that is mountable to a stationary member; a tensioner arm pivotally mounted to the pivot shaft for pivoting movement about a tensioner arm pivot axis; a pulley assembly rotatably mounted to the tensioner arm and positioned for engagement with the endless drive member; a tensioner spring that is a helical torsion spring, positioned to urge the tensioner arm into the endless drive member, wherein the spring has a first helical end and a second helical end, wherein the first helical spring end is positioned to transfer force with a first spring end force transfer surface on the base and the second helical spring end is positioned to transfer force with a second spring end force transfer surface on the tensioner arm; and a radial damping mechanism that includes a damping member positioned in a surrounding relationship with the tensioner spring, and a push block, wherein the push block has a first end face and a second end face spaced from the first end face by a selected angular spacing, wherein the push block is positioned between one of the first and second helical spring ends and one of the first and second spring end force transfer surfaces on one of the base and the tensioner arm, and wherein the damping member is frictionally engaged with a friction surface on the other of the base and the tensioner arm during pivotal movement of the tensioner arm relative to the base, wherein the push block is moveable relative to the damping member, and wherein a first radial center of engagement between the first end face of the push block and the tensioner spring is at a first radius relative to the tensioner arm pivot axis, resulting, in use, in a first force at the first radius, and wherein a second radial center of engagement between the second end face of the push block and the one of the first and second spring end force transfer surfaces is at a second radius relative to the tensioner arm pivot axis, resulting, in use, in a second force at the second radius, wherein the second radius is smaller than the first radius so as to induce a pivoting movement of the push block radially outward into engagement with thedamping member, thereby driving the damping member into engagement with the friction surface so as to generate a push block generated frictional damping force.

2. A tensioner according to claim 1 , wherein the first and second helical spring ends of the tensioner spring are positioned such that forces applied to the first and second helical ends through the push block and through the other of the base and the tensioner arm generate a pivoting spring torque on the tensioner spring, so as to drive the tensioner spring into engagement with the damping member thereby driving the damping member into engagement with the friction surface so as to generate a tensioner spring torque generated frictional damping force.

3. The tensioner according to claim 1 , wherein the one of the first and second spring end force transfer surfaces on the one of the base and the tensioner arm is the second spring end force transfer surface on the tensioner arm.

4. The tensioner according to claim 1 , wherein the radial damping member includes a damping ring made from a first material, and a damping sleeve mounted outside on the damping ring and made from a second material that is softer than the first material, and wherein the damping sleeve includes a push block holder that engages a recess in the push block, the recess having a plurality of surrounding walls and wherein there is clearance between the push block holder and surrounding walls of the recess, and wherein the damping ring includes at least one tab that extends radially inwardly to hold a face of the push block that is opposite to the recess so as to hold the push block movably to the damping member.

5. The tensioner according to claim 4, wherein the damping sleeve is nested on the outer side of the damping ring, a plurality of positioning holes are formed in the damping ring, a plurality of positioning protrusions in one-to-one correspondence with the positioning holes are arranged on an inner side of the damping sleeve, a push block holder is arranged inwardly at a bottom of the damping sleeve, a recess is formed in a middle of the push block, and the push block holder is correspondingly embedded in the recess.

6. The tensioner according to claim 1 , further comprising an axial damping mechanismthat includes a thrust washer and a fixed washer mounted to a bushing on the pivot shaft, wherein the thrust washer is sleeved on an outer side of the bushing, wherein an inner end face of the thrust washer abuts against a back face of the pivot support, wherein the fixed washer is arranged on an outer end face of the thrust washer, wherein the fixed washer tightly presses the thrust washer against the pivot support, and the torsional spring tightly urges the pivot support against the thrust washer axially.

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