WO2001057416A2

WO2001057416A2 - Linear belt tensioner with two degrees of freedom

Info

Publication number: WO2001057416A2
Application number: PCT/CA2001/000098
Authority: WO
Inventors: Christian Jansen; Terry P. Cleland
Original assignee: Litens Automotive Partnership
Priority date: 2000-02-04
Filing date: 2001-01-31
Publication date: 2001-08-09
Also published as: AU2001228244A1; WO2001057416A3

Abstract

A tensioner (10) has a fixed structure (12) and a movable structure (30). The movable structure (30) is mounted for movement with respect to the fixed structure (12). A pulley (36) is mounted on the movable structure (30) and rotatable about a first axis (52). A spring (26) is disposed between the fixed structure (12) and the movable structure (30) biasing the movable structure (30) away from the fixed structure (12) into a tensioning engagement. The movable structure (30) is slidably mounted on the fixed structure (12) for reciprocating movement along and pivotally about a second axis (33) generally perpendicular with respect to the first axis accommodate changes in alignment of the pulley (36) in maintaining the tensioning engagement.

Description

LINEAR BELT TENSIONER WITH TWO DEGREES OF FREEDOM

Field Of The Invention

The present invention relates to tensioners and more particularly to a belt tensioner having a pulley and which is adapted to accommodate misalignment of pulleys in the belt system.

Background Of The Invention

Belt or chain drive systems are known to have many applications in the mechanical arts. For example, such systems are well known in motor vehicle engines. In another application, a power sliding door for a minivan or other vehicle is driven by a belt or chain, which can be driven by a motor to pull the door open or closed.

Such drive systems conventionally include rollers or pulleys over which the belt or chain passes. If the pulleys in the system are misaligned with respect to the general plane along which the belt is positioned, the entire system may operate inefficiently and cause unnecessary wear on the belt or chain. In the case where the belt system is in an enclosed area, it may be difficult to access for repair, requiring removal of body panels or other parts of the vehicle. Such a misalignment may result from problems with installation of the pulleys or slight displacement of the pulleys in an axial direction over time due to wear or flexing of structure on which the pulleys are mounted.

A belt system used to power a sliding door is generally positioned along the lower portions of the vehicle's frame. When the frame of the vehicle or other mounting structure of the belt system is strained or when pulleys within the belt system are misaligned for other reasons, the belt may be subject to a slight twisting action. It is therefore an object of the present mvention to provide a belt tensioner which is capable of accommodating movement or misalignment of pulleys within a belt system.

It is a further object of the present invention to provide a belt tensioner which is adapted to use in a power door module for a vehicle having a power sliding door. It is yet another object of the present invention to provide a belt tensioner which is not sensitive to contamination and does not require external lubrication. Summary Of The Invention

To achieve the foregoing objects, a tensioner is provided which is adapted to use with a driven, endless, elongated member such as a belt or chain. The tensioner includes a fixed structure and a movable structure. The movable structure is mounted for movement with respect to the fixed structure. A pulley is mounted on the movable structure and rotatable about a first axis. A spring is disposed between the fixed structure and the movable structure biasing the movable structure away from the fixed structure into a tensioning engagement. The movable structure is slidably mounted on the fixed structure for reciprocating movement along and pivotally about a second axis generally perpendicular with respect to the first axis to accommodate changes in alignment of the pulley in maintaining the tensioning engagement.

According to one aspect of the invention, there is provided a drive system including an elongated support member, a tensioner mounted on opposite ends of the support member, an endless belt entrained about the tensioners, and a drive motor operatively engaging the endless belt to effect driving movement thereof. Each of the tensioners has a fixed structure mounted on the support member and a movable structure mounted for movement with respect to the fixed structure. A pulley is mounted on the movable structure and rotatable about a first axis. A spring is disposed between the fixed structure and the movable structure biasing the movable structure away from the fixed structure into a tensioning engagement with the endless belt. The movable structure is slidably mounted on the fixed structure for reciprocating movement along and pivotally about a second axis generally perpendicular with respect to the first axis to accommodate changes in alignment of the pulley in maintaining the tensioning engagement.

Brief Description Of The Drawings

FIG. 1 is an exploded, isometric view of the tensioner according to the present invention; FIG. 2 is an isometric view of the tensioner according to the present invention; FIG. 3 is a sectional view of the tensioner according to the present invention, taken along a plane in which both the first axis of pulley rotation and second axis of pivotal pulley movement exist; and

FIG. 4 is a sectional view of the tensioner according to the present invention, taken perpendicular to the section of FIG. 3.

FIG. 5 is a plan view of a power sliding door opening/closing system which employs two tensioners.

Detailed Description Of The Preferred Embodiments Referring now to FIG. 1, which is an exploded view of the belt tensioner 10 of the present invention, it becomes apparent that the tensioner 10 has at one end a fixed structure 12, or shaft base, which is preferably fastened to a fixed member of the vehicle's frame. The tensioner 10 further includes a spring 26 and a movable structure 30 which is movable relative to the fixed structure 12. The tensioner 10 also includes a pulley 36 that is mounted for rotation on the movable structure 30 by a spindle 42.

The fixed structure 12 has an elongated, generally cylindrical or sleeve portion 14 comprising most of its length. At one end it has a flattened bracket portion 16 which has holes 18 therethrough to accept fasteners such as bolts or rivets for fastening it to the frame member. In general, the portion used to connect the fixed structure 12 to a vehicle's frame need not be of the type shown as flattened bracket portion 16, but may be any shape appropriate to be used to fasten the fixed structure 12 to the frame.

As shown in FIGS. 3 and 4, the cylindrical sleeve portion 14 has a hollow interior 20. As best seen in FIGS. 1 and 2, the exterior surface of sleeve portion 14 preferably has a series of splines defined by longitudinally extending recessed portions 22 circumferentially alternating with longitudinally extending raised portions 24 presenting bearing surfaces.

The fixed structure 12 is preferably made from an injection molded thermoplastic material having fiber reinforcement and solid lubricants. In order to ensure proper balancing of the tensioner, a material with a low coefficient of static friction is required as well as a low coefficient of sliding friction. Further, the use of a plastic-plastic interface between the fixed and movable structures provides inherent damping which reduces wear on the tensioner. The material for the fixed structure 12 preferably has dry self-lubricating properties.

Housed in the hollow interior 20 of the cylindrical portion 14 of the fixed structure 12 is one end of the coil compression spring 26 (see FIG. 3). The coil compression spring 26 may be made from any appropriate material but is preferably a chrome-silicone spring. The coil compression spring 26 extends outside the cylindrical portion 14 of the fixed member and the other end of the spring engages the inside of a cylindrical hollow portion 28 of the movable structure 30 which acts as a tensioner slider.

The hollow sleeve portion 28 of the movable structure 30 preferably has a sufficiently large diameter to allow at least a portion of the cylindrical portion 14 of the fixed structure 12 to fit therein, preferably with minimal clearance but enabling free sliding movement of the raised portions 24 against an inner bearing surface 29. The hollow sleeve portion 28 of the movable structure 30 further preferably has structure, such as a recess 32, at its closed end which is constructed and arranged to engage and receive the end of the spring 26 in a fixed manner. The movable structure 30 maintains the ability to move axially along an axis 33 parallel to the longitudinal direction of the spring. The spring 26 is constructed and arranged to bias the movable structure 30 and hence pulley 36 mounted thereon away from the fixed structure 12 and into tensioning engagement with a belt. In addition, the movable structure is also able to pivot or rotate freely about the axis 33 to accommodate changes in alignment of a belt engaged with the pulley 36. As with the fixed structure 12, the movable structure 30 is preferably made from a plastic material, and is preferably 6/6 nylon. The movable structure 30 additionally has a mounting structure 34 at the opposite end from the hollow sleeve portion 28 which is constructed and arranged to provide a mount for a pulley 36. In a preferred construction, two opposed side walls 38 of mounting structure 34 each has a hole 40 therethrough to accept one end of a spindle 42 which is preferably made from steel. The pulley 36 is mounted for rotation about the spindle 42. Also mounted on the spindle 42 is a hub 46 immediately surrounding the spindle 42 and a bearing 44 mounted on the hub as shown in FIG. 3. While the bearing is preferably a single row ball bearing, such as a 608 bearing, it may be of any suitable type. The pulley 36 and hub 46 are preferably synchronously overmolded on the bearing 44. The bearing 44 enables rotation of the pulley 36 about the spindle 42. A surface 50 of the pulley 36 engages a surface of an elongated drive member, not shown, such as a drive belt or chain.

The side walls 38 are preferably configured to provide the additional function of protecting the pulley 36 from damage if the tensioner 10 is dropped, or is interfered with by a foreign object. This helps to reduce the possibility of damage to the pulley 36 which could result in increased belt wear. In operation, the belt is driven by a driving pulley connected with a drive motor, not shown. The belt, in turn, engages the pulley 36 which acts as an idler and is rotatable about a first axis 52 defined by the spindle 42. The spring 26 provides a ^■ biasing force which forces the movable structure 30 towards the belt so as to maintain the pulley 36 in tensioning engagement with the belt to provide substantially constant tension to the belt during operation. The movable structure 30 is free to rotate about a second axis 33 which is generally perpendicular with respect to the first axis to automatically accommodate any twisting of the belt and ensure full contact and evenly distribute engagement forces at the portion of contact with the belt (or chain).

As will be appreciated from FIG. 4, when the spring 26 is compressed, the inside surface 29 of the movable structure 30 will act as a bearing surface in contact with the raised surface portions 24 of the fixed structure 12 such that the fixed structure 12 acts as a shaft about which the movable structure 30 may rotate. The movable structure 30 is also constructed and arranged to slide along the raised portions 24 of the fixed structure 12 during movement of the moveable structure 30 towards and away from the belt in a linear fashion. The surfaces provided by the surface 29 on movable structure 30 and the raised surface portions 24 on the fixed structure 12 may be considered first and second bearing surfaces, respectively. These bearing surfaces permit both the movement of the movable member 30 longitudinally toward and away from the belt along the second axis 33 and also the pivotal movement of the movable member 30 about the second axis 33. Use of recessed portions 22 reduces the total contact area between the two parts 12, 30 thereby reducing the total friction between them as well as allowing contamination to escape the system.

The movable structure 30 is able to accommodate misalignment of changes in pulleys in the belt system by rotating about the second axis 33 to take into account twisting of the belt as a result of such alignment variations. The belt primarily engages cylindrical surface 50 of the pulley 36. As the belt may twist or pulled sideways, it may engage walls 54 of the sheave 48. It is contemplated that the directional force of a twisting belt upon the surface 50 alone is sufficient to cause the movable structure to pivot or rotate about axis 33 to maintain proper flush engagement with the belt. In any event, if the belt imparts a force to the pulley 36 which has a component transverse to the main belt load force along the second axis 33, rotation of the movable structure 30 about the second axis 33 will occur to balance such off axis forces to the extent possible. The movable structure 30 is also able to simultaneously linearly extend or contract under the force of spring 26 to accommodate for tension variations in the belt. Though the tensioner shown in the FIGS, is substantially straight from end to end, this is not necessary to its operation and a tensioner according to the present invention may be constructed in any shape appropriate to the desired application.

While the tensioner described herein can be used in other belt or chain driven systems, a preferred application for this tensioner is in a power sliding door opening/closing system which employs two tensioners and a Niobrara belt, as disclosed in Canadian Patent Application No. 2,268,642 (see tensioners identified by reference numeral 11 in that application). FIG. 5 shows a plan view of such a system. A tensioner 10 is at either end of an elongated support member 58. A belt 60 passes over the pulley 36 of each tensioner, and is actuated by at least one motor which is disposed below the plate 62.

It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention.

Claims

WHAT IS CLAIMED:

1. A tensioner comprising: a fixed structure; a movable structure mounted for movement with respect to said fixed structure; a pulley mounted on said movable structure, said pulley being rotatable about a first axis; a spring disposed between said fixed structure and said movable structure biasing said movable structure away from said fixed structure into a tensiomng engagement; said movable structure being slidably mounted on said fixed structure for reciprocating movement along and pivotally about a second axis generally perpendicular with respect to said first axis to accommodate changes in alignment of said pulley in maintaining said tensioning engagement.

2. A tensioner according to claim 1, wherein said movable structure comprises a first bearing surface and wherein said fixed structure comprises a second bearing surface, said first bearing surface slidably engaging said second bearing surface damping movement of the movable structure relative to the fixed structure.

3. A tensioner according to claim 2, wherein said second bearing surface is a spline.

4. A tensioner according to claim 3, wherein said first bearing surface is an inside surface of a first sleeve and said second bearing Surface is an outside surface of a second sleeve.

5. A tensioner according to claim 4, wherein said second sleeve receives said spring and said spring extends beyond said second sleeve to engage a recess in an end of said first sleeve.

6. A tensioner according to claim 1, wherein one of said movable structure and said fixed structure has a first sleeve and the other of said moveable structure and said fixed structure has a second sleeve, said second sleeve being slidably received within said first sleeve.

7. A tensioner according to claim 6, wherein said second sleeve has a splined end in frictional engagement with an inner surface of said first sleeve.

8. A tensioner according to claim 7, wherein said second sleeve receives said spring and said spring extends beyond said second sleeve to engage a recess in said first sleeve.

9. A drive system comprising an elongated support member, a tensioner mounted on opposite ends of said support member, an endless belt entrained about said tensioners, a drive motor operatively engaging said endless belt to effect driving movement of said endless belt, each of said tensioners comprising: a fixed structure mounted on said support member; a movable structure mounted for movement with respect to said fixed structure; a pulley mounted on said movable structure, said pulley being rotatable about a first axis; a spring disposed between said fixed structure and said movable structure biasing said movable structure away from said fixed structure into a tensioning engagement with said endless belt; said movable structure being slidably mounted on said fixed structure for reciprocating movement along and pivotally about a second axis generally perpendicular with respect to said first axis to accommodate changes in alignment of said pulley in maintaining said tensioning engagement.

10. A drive system according to claim 9, wherein said movable structure comprises a first bearing surface and wherein said fixed structure comprises a second bearing surface, said first bearing surface slidably engaging said second bearing surface damping movement of the movable structure relative to the fixed structure.

11. A drive system according to claim 10, wherein said second bearing surface is a spline.

12. A drive system according to claim 11, wherein said first bearing surface is an inside surface of a first sleeve and said second bearing surface is an outside surface of a second sleeve.

13. A drive system according to claim 12, wherein said second sleeve receives said spring and said spring extends beyond said second sleeve to engage a recess in an end of said first sleeve.

14. A drive system according to claim 9, wherein one of said movable structure and said fixed structure has a first sleeve and the other of said moveable structure and said fixed structure has a second sleeve, said second sleeve being slidably received within said first sleeve.

15. A drive system according to claim 14, wherein said second sleeve has a splined end in frictional engagement with an inner surface of said first sleeve.

16. A drive system according to claim 15, wherein said second sleeve receives said spring and said spring extends beyond said second sleeve to engage a recess in said first sleeve.