CA2587052C

CA2587052C - Installation shaft assembly

Info

Publication number: CA2587052C
Application number: CA2587052A
Authority: CA
Inventors: Marek Frankowski; Miroslaw Gefrerer
Original assignee: Litens Automotive Partnership
Current assignee: Litens Automotive Partnership
Priority date: 2004-11-18
Filing date: 2005-11-18
Publication date: 2013-08-13
Anticipated expiration: 2025-11-18
Also published as: CA2587052A1; WO2006053432A3; DE112005002788T5; CN101057090A; WO2006053432A2; CN100549466C

Abstract

A tensioner for a synchronous or non-synchronous drive system of a motor vehicle engine. The tensioner has an installation shaft with an aperture for receiving a bolt for affixing the tensioner to a motor vehicle engine. The aperture has a center that is offset from the first axis of rotation of a tensioner arm. The stamped installation shaft has a guide portion and an integrally formed plate portion. The plate portion extends transversely from the guide portion. The guide portion extends into the pivot shaft on which the tensioner arm is pivotally mounted. A distal end of the guide portion engages the pivot shaft in a manner which enables rotational movement and which prevents axial movement therebetween. The guide portion is configured to maintain offsetness of a distal end of the guide portion as the offsetness of the center of the aperture when the tensioner is installed on an engine.

Description

2 INSTALLATION SHAFT ASSEMBLY
Field of the Invention [0001] The present invention relates generally to tensioners, and more particularly, to an installation shaft assembly for a tensioner.
Background of the Invention [0002] Belt tensioners are known in the art for use in automotive applications and are utilized to apply a load to the belt or chain to maintain a desired amount of tension on the belt drive to drive various components attached to the belt system.
Additionally, belt tensioners are utilized in a non-synchronized belt drive system to prevent belt slippage and power transmission loss. Tensioners are commonly utilized in accessory drive systems, and timing belt or timing chain systems of an automobile.

[0003] Typical belt tensioners include a tensioner arm, which is fitted with an idler pulley that is mounted on a ball bearing assembly. The tensioner arm if pivotally mounted on a pivot shaft. A coil spring is wrapped coaxially around the pivot shaft for pre-tensioning the tensioner arm enabling the idler pulley to exert a force on the belt. In this manner, the force of the coil spring applies a load to the belt while the idler pulley deflects and takes up slack in the length of the belt or chain.

[0004] In certain applications, there is a limited amount of space that is available for mounting the tensioner on the engine. This is particularly true for timing belt applications where volume on the engine is at a premium. In these applications, a double eccentric type of tensioner is commonly used. A first eccentric has the same function as the tensioner arm. A second eccentric or installation shaft adjusts the tensioner during installation to pre-apply the desired load on the belt.

[0005] When the tensioner is installed on an engine, the position of the tensioner needs to be adjusted to correspond with a nominal installation. The tensioner is fixedly mounted to an engine surface after proper orientation and positioning of the tensioner. An adjusting or installation shaft assembly is utilized to position the tensioner, as well as to maintain a proper belt tension. Examples of belt tensioners for motor vehicles and methods for installing the belt tensioner to the engine include:
United States Patent Nos. 5,919,107; 6,149,542; 6,364,795; 6,375,588; and

6,464,604.

[0006] At present, installation shafts can be manufactured as a one piece construction, although most are of two piece construction, utilizing known methods such as injection molded sintered metal, die cast aluminum, and die cast zinc. While these parts seem simple enough, die casting and pressing shapes such as the installation shaft, which have a very long length to diameter ratio, are difficult to make, require expensive tooling, and have extremely high tooling capital and maintenance costs associated with them.

[0007] Alternatively, installation shafts can made employing a two piece stamped steel design. An installation plate and a cylindrical guide tube are staked together to form the installation shaft. The staking tools, required to join or stake the upper installation plate to the lower guide tube, are again relatively expensive, and require detailed set-up costs, as well as constant maintenance order to maintain joint integrity.

[0008] Further, staked installation shafts may have inconsistencies with respect to engagement of the multiple pieces due to variations in part size, and variations introduced from the staking operation. Such variations may result in differing forces needed when installing the tensioner onto an engine, resulting in improper installation or damage to the tensioner.

[0009] While the process and theory of staking seems simple enough, it ultimately requires that the material to be joined be struck (impacted) and deformed just enough, but not too much, in order to hold a part together, and to maintain the required clamping force without fracturing or jamming surrounding components. The clamping force of a stake can vary wildly with minor variations in material properties (carbon content, hardness, grain structure, flow characteristics), tolerance stack-up of each component within the joint, which determines ultimate striking force, compression depth, and material flow characteristics, as well as other factors such as staking tool condition, press condition and deflection, initial press set-up, and a myriad of other factors.

[0010] If an eccentric installation shaft is staked too hard within the pivot shaft, too much material will be displaced by the staking die, or punch, and the eccentric shaft will become fused to the pivot shaft. The eccentric will now either stick when rotated, or not rotate at all when turned with a reasonable amount of force, ultimately failing to rotate freely. When installed onto the engine, an operator or installation machine (i.e. an automated torque wrench) will apply a force to the eccentric installation shaft via an installation tool, in order to try to push or rotate the tensioner into the belt, and to align the tensioner arm pointer to the nominal belt mark indicated on the stamped steel base plate. If the installation eccentric does not rotate (i.e. is fully seized) within the pivot shaft due to too high a staking force, either the installation operation will cease when the torque limit is exceeded, or if no such limits exist, the installation plate can be plastically deformed, or worst, sheared off from the vertical tube portion.
If the tensioner partially binds (i.e. is partially seized) within the pivot shaft, the installation procedure will overshoot and undershoot the nominal belt mark, as the majority of torque applied to the installation eccentric will be directed to overcoming sporadic friction between the eccentric and pivot shaft interface, and not be employed in forcing the tensioner into the belt.

[0011] If the eccentric installation shaft is staked too lightly, too little material will be displaced by the staking die, or punch, and the eccentric installation shaft will slide freely from the pivot shaft, and allow the tensioner to fall apart either during shipping, during handling, or during actual installation onto the engine. A tensioner "explosion"
during installation may shut the engine assembly line down, as each part would them have to be located and identified, to insure that it has not become trapped within the timing drive system where belt tooth skip or chain skip would result if a part were to be ingested by the timing drive..

[0012] Therefore, it remains desirable to provide a tensioner installation shaft that is economical to manufacture, as well as provides a reliable and efficient means for installing and positioning a tensioner onto an internal combustion engine.
Summary of the Invention

[0013] The disadvantages of the prior art may be overcome by providing a tensioner assembly with a one piece stamped installation shaft assembly.

[0014] It is desirable to provide an installation shaft assembly that is stamped from a single sheet of metal and formed to incorporate both the guide tube and the installation plate.

[0015] According to one aspect of the invention there is provided a tensioner for a synchronous or non-synchronous drive system of a motor vehicle engine. The tensioner has a mounting plate with a cylindrical pivot shaft and an anchor spaced from the pivot shaft. A tensioner arm is rotatable mounted on the pivot shaft.
The tensioner arm has a first axis of rotation. A pulley is rotatably supported on the tensioner arm. The pulley has a second axis of rotation spaced from and extending generally parallel to the first axis of rotation. A coil spring operably extends between the mounting plate and the tensioner arm to bias the tensioner arm in a take up direction. An installation shaft is rotatably mounted within the pivot shaft and rotatable about the first axis of rotation. The installation shaft has an aperture for receiving a bolt for affixing the tensioner to a motor vehicle engine. The aperture has a center that is offset from the first axis of rotation. The installation shaft has a guide portion and an integrally formed plate portion. The plate portion extends transversely from the guide portion. The guide portion extends into the pivot shaft. A
distal end of the guide portion engages the pivot shaft in a manner enabling rotational movement and which prevents axial movement therebetween. The guide portion is configured to maintain offsetness of a distal end of the guide portion as the offsetness of the center of the aperture when the tensioner is installed on an engine.
Brief Description of the Drawings

[0016] Exemplary embodiments of the invention will now be described in conjunction with the following drawings wherein like numeral represent like elements, and wherein:

[0017] Figure 1 is a perspective view of a tensioner assembly incorporating the installation shaft assembly according to one embodiment of the invention;

[0018] Figure 2 is a plan view of the tensioner assembly of Figure 1;

[0019] Figure 3 is a partially exploded view of the tensioner assembly and installation shaft assembly according to one embodiment of the invention;

[0020] Figure 4 is a partial fragmentary, exploded perspective view of the installation shaft assembly according to one embodiment of the invention;

[0021] Figure 5 is a perspective view of the installation shaft prior to forming; and

[0022] Figure 6 is a perspective view of another alternative embodiment of the installation shaft of the present invention;

[0023] Figure 7 is a second embodiment of a tensioner incorporating installation shaft of the present invention, wherein the tensioner has the distal end of the coil spring anchored to the engine;

[0024] Figure 8 is schematic view of an initial step of assembly of a tensioner of incorporating installation shaft of Figure 6;

[0025] Figure 9 is a schematic view of a subsequent step of assembly following Figure 8; and

[0026] Figure 10 is a schematic view of a finished assembly.
Detailed Description of the Preferred Embodiments

[0027] Referring to Figures 1-3, a tensioner is shown at 10 for tensioning a belt driven by a motor vehicle engine. The tensioner 10 includes a base plate 20, a pivot shaft 34, a tensioner arm 16, a pulley 12 and a bearing 14. The pulley 12 is rotatably supported by ball bearing race assembly 14. The bearing 14 and pulley 12 are rotatably mounted on cast aluminum tensioner arm 16 having an eccentric bore enabling translation of the pulley 12 to tension the belt. Tensioner arm 16 rotates about a first axis of rotation defined by the center of the eccentric bore 18.
The pulley 12 rotates about a second axis of rotation that is spaced from and extends parallel to the first axis of rotation.

[0028] Base plate 20 is seated adjacent a base of the tensioner arm 16 for mounting and aligning the tensioner 10 on the engine. Base plate 20 is formed to incorporate a tab 11 having features representing the free arm stop position, the load stop position, and optionally various belt marking positions, namely nominal belt mark, change belt mark, as well as a tang 21 for fixing the end of coil spring 15. In addition, the mounting plate 20 has an anchor 23 extending generally perpendicular to the plane of the mounting plate 20 and configured to engage a recess in the engine block to maintain orientation of the tensioner 10. Other forms of anchors are well known in the art and include a two prong structure that engages a bolt or post on the engine.

[0029] Coil spring 15 acts between the mounting plate 20 and the tensioner arm 16 to bias the tensioner arm 16 and pulley 12 in a take up direction into engagement with the belt. The tensioner arm 16 includes a pointer 22 that moves pivotally relative to the base plate 20 for alignment with a nominal position indicator on the base plate 20 =
during installation of the tensioner 10 on the engine.

[0030] Referring to Figure 4, the pivot shaft 34 includes an elongated cylindrical shank portion 36 defining a center bore 38 extending between a proximal end 40 and a distal end 42. A collar 44 projects radially from the proximal end 40 of the shank portion 36. A counter bore 46 is formed in the proximal end 40 of the shank portion 36 to define a radial shoulder 48. The tensioner arm 16 has an inner sleeve or pivot bushing 45 that is made from an organic polymeric material, such as Nylon, which is then is mounted on the shank portion 36. In this manner, tensioner arm 16 is able to rotate relative to the base 20.

[0031] The tensioner 10 has an installation shaft 32 for assembling the tensioner 10 and for facilitating installation of the tensioner 10 onto the engine and tensioning of the belt. The installation shaft 32 of the present invention is preferably formed as a one piece stamped steel member and includes a generally planar plate portion connected to a generally C-shaped guide portion 52 by a bent neck portion 54 extending therebetween. The plate portion 50 includes a key hole 56, preferably hexagonally shaped, and a bolt hole 58 for receiving a mounting bolt 59 therethrough.
The key hole 56 is spaced from the bolt hole 58, providing leverage to more easily rotate installation shaft 32 during installation. Bolt hole 58 has a diameter that is less than the inside diameter of center bore 38 of pivot shaft 34. Plate portion 50 has two tabs 51, 53 which maintains the orientation of plate portion 50 during operation.

[0032] The guide portion 52 extends generally perpendicular to the plate portion 50 and extends arcuately about the first axis of rotation defined by the bolt hole 58. The axis of rotation of the guide portion 52 defined by the center of center bore 38, the first axis of rotation which is offset from the axis of the center of the bolt hole 58.
The outside diameter of the guide portion is slightly less than the inside diameter of the center bore 38 of the pivot shaft 36, enabling the installation shaft 32 to fit within and frictionally engage the center bore 38 and rotate therein.

[0033] A pair of diagonally opposed flexible locking fingers 60 extend longitudinally from the end of the guide portion 52 to a distal end 62. The distal end 62 of each locking finger 60 includes a radially projecting hook portion 64 for engaging with the shoulder 48 on the pivot shaft 34. The locking fingers 60 are biased to engage with the shoulder in a snap fit and lock the installation shaft 32 to the pivot shaft 34. The locking fingers 60 thus hold the installation shaft 32 to the tensioner assembly 10 during transport and assembly onto the vehicle engine.

[0034] The installation shaft 32 further includes a tab 66 positioned between the locking fingers 60 and similarly extending longitudinally from the end of the guide portion 52. An embossment 68 projects radially inwardly from the tab 66 into the axis defined by the bolt hole 58. The height of the embossment 68 is of the order of the amount of offsetness between the center of the bolt hole 58 and the center bore 38.
The embossment 68 engages the bolt 59 to ensure that the perpendicularity of the installation shaft 32 as the installation shaft 32 is rotated during the installation process.

[0035] The one piece installation shaft 32 of the present invention is formed from a single unitary member, preferably made of steel, as shown in Figure 5, which is stamped and bent, or formed, into the installation shaft 32 as shown in Figure 4. The stamping and forming processes of the one piece installation shaft are cost effective and eliminate the potential for failure in the joining of the plate portion 50 to the guide portion 52. Furthermore, the critical distance between the bottom of the=
plate portion 50 and the hook structure 64 of the fingers 60 can be readily controlled in the stamping and forming process to ensure proper alignment and engagement with the ledge 48 of the pivot shaft 34 during assembly.

[0036] Referring again to Figure 3, the installation shaft 32 is inserted into the bore 18 in the tensioner 10 from the side opposite the pivot shaft 34. The guide portion 52 is inserted through the center bore 38 of the pivot shaft 34 until the hook structure 64 of the flexible locking fingers 60 engage the shoulder 48 of the pivot shaft 34 locking the shafts 32, 34 together. The flexible locking fingers 60 project slightly radially outwardly and are flexed inwardly by engagement with the inside surface of the center bore 38 during assembly, providing a "push and click" assembly procedure.
The counter bore 46 allows the fingers 60 to spring radially outwardly for engagement with the shoulder 48 to automatically interlock the installation shaft 32 and pivot shaft 34.

[0037] The stamped one piece installation shaft 32 provides controlled tolerances, in particular, providing a consistent predetermined distance between the underside of the plate portion 50 and the hook structure 64 for proper engagement with the shoulder 48 on the pivot shaft 34. It is desirable to provide this predetermined distance slightly greater than the distance between the underside of the collar 44 and the distal end 42 of the pivot shaft 34 in order to allow the installation shaft 32 to rotate relative to= the pivot shaft 34 for proper installation of the tensioner 10 onto the engine.

[0038] To assemble a tensioner 10 of the present invention, the steel mounting plate 20 is stamped. The pivot shaft 34 and the base plate 20 are staked together to form a permanent, fixed joint. A plastic spring support 13 and coil spring 15 are then inserted loosely over the pivot shaft 34. The spring support 13 cradles the end of the coil spring 15 and provides frictional damping. The lowermost end of the coil spring 15 is hooked into the tang 21 of the base plate. The tensioner arm 16, pivot bushing 45, bearing 14 and pulley 12 are then installed over the pivot shaft. The tensioner arm 16 is rotated to locate the upper spring tang of the coil spring 15 until the coil spring 15 engages a hookup feature in the tensioner arm 16. The coil spring 15 is wound in the coil direction (i.e. winds the spring "up"), to the point at which the tensioner arm = pointer 22 corresponds to the NOMINAL BELT MARK on the base plate. The tensioner arm 16 is then pushed down, so that the tensioner arm 16 rests on the spring support 13. A plastic thrust washer 25 is positioned over the top of the pivot shaft 34.
The eccentric installation shaft 32 is inserted into the central bore 38 of the pivot shaft 34. The installation plate 50 is pressed against the thrust washer 25 to hold the tensioner assembly 10 together axially. Optionally, a staking tool or mandrel is inserted into the base of the pivot shaft 34 to deform the fingers 60 and/or tab 66 to permanently retain the eccentric shaft 32 within the pivot shaft 32 and hold the tensioner assembly 10 together axially while allowing relative rotational movement between the installation shaft 32 and the pivot shaft 34. The coil spring 15 urges the tensioner arm 16 to unwind and abut against the FREE ARM belt stop.

[0039] Referring to Figure 7, a second embodiment of a tensioner incorporating the installation shaft 32 of the present invention. In this embodiment, the pivot shaft is mounted directly onto the engine block without the aid of a mounting plate.
The remote end of the coil spring 15' is anchored to the engine. In this view, the embossment 68 clearly illustrates the support that is provided to the bolt 59 to properly maintain vertical alignment of the tensioner.

[0040] Referring to Figure 6, there is shown another alternative embodiment of the installation shaft 32 of the present invention, wherein like numerals represent the same or similar parts. The installation shaft 32 remains a one piece stamped member having an integrally formed plate portion 50 and guide portion 52 interconnected by a bent neck portion 54. The guide portion 52 is bent to into a C-shape forming an arcuate guide sleeve. An embossment 68 projects radially from the guide portion 52 into the axis defined by the bolt hole 58. However, the installation shaft 32 of the =
alternative embodiment does not include the locking fingers 60 extending from the guide portion 52.

[0041] Referring to Figures 8 to 10, a staking tool 61 is required to deform the distal end of the guide portion 52 to form a circumferentially extending hook structure 64' or structures 64' to interconnect the installation shaft 32 and the pivot shaft 34. The interconnection allows relative rotational movement between installation shaft 32 and the pivot shaft 34 while ensuring that the installation shaft is axially locked onto the pivot shaft 34, preventing accidental disassembly.

[0042] In each of the embodiments, the tensioner 10 is now fully assembled and held together by the interlocking connection between the installation shaft 32 and pivot shaft 34 for shipping and installation onto the engine of the vehicle.
Finally, a fully detailed explanation of the installation and adjustment of the tensioner 10 is set forth by way of example in United States Patent No. 5,919,107.

Claims

What is claimed is:

1. A tensioner for drive system of a motor vehicle engine, said tensioner comprising:
a cylindrical pivot shaft, a tensioner arm rotatable mounted on said pivot shaft, said tensioner arm having a first axis of rotation, a pulley rotatably supported on said tensioner arm, said pulley having a second axis of rotation spaced from and extending generally parallel to said first axis of rotation, a coil spring operably engaging the tensioner arm to bias the tensioner arm in a take up direction, an installation shaft rotatably mounted within said pivot shaft and rotatable about said first axis of rotation, said installation shaft having an aperture for receiving a bolt for affixing the tensioner to a motor vehicle engine, said aperture having a center that is offset from said first axis of rotation, said installation shaft comprising a guide portion and an integrally formed plate portion, said plate portion extending transversely from said guide portion, and said guide portion extending into said pivot shaft, said guide portion engaging said pivot shaft enabling rotational movement and preventing axial movement therebetween, said guide portion configured to maintain offsetness of a distal end of said guide portion as said offsetness of said center of said aperture, wherein said installation shaft is stamped from sheet steel to provide said guide portion and said integrally formed plate portion.

2. A tensioner as set forth in claim 1 wherein said guide portion is generally C-shaped and a bent neck portion interconnects said guide portion and said plate portion.

3. A tensioner as set forth in claim 2, wherein said plate portion has an aperture for receiving a tool enabling rotation of said installation shaft.

4. A tensioner as set forth in claim 3, further comprising a thrust washer axially mounted between said plate portion and said tensioner arm.

5. A tensioner as set forth in claim 4, further comprising a spring support collar axially mounted on said pivot shaft and engaging said and cradling said spring.

6. A tensioner as set forth in claim 5, further comprising a pivot bushing disposed between said pivot shaft and said tensioner arm.

7. A tensioner as set forth in claim 1, wherein said guide portion has an embossment positioned to maintain said offsetness.

8. A one piece stamped installation shaft for assembling and installing a tensioner to a motor vehicle engine, comprising:
an elongated and generally C-shaped guide portion defining a first axis;
a generally planar plate portion extending transverse from said guide portion;
and a bent neck portion extending between and interconnecting said guide portion and said plate portion, said plate portion having a bolt hole offset from said first axis.

9. A one piece stamped installation shaft as set forth in claim 8 wherein said guide portion has a radially extending embossment.

10. A one piece stamped installation shaft as set forth in claim 9, wherein a distal end of said guide portion is deformable to form a hook structure.

11. A one piece stamped installation shaft as set forth in claim 8 wherein said guide portion includes a plurality of spaced apart flexible locking fingers extending axially from a distal end of said guide portion.

12. A one piece stamped installation shaft as set forth in claim 11 wherein each of said locking fingers are deformable to form a hook structure at a distal end thereof.

13. A one piece stamped installation shaft as set forth in claim 11 wherein each of said locking fingers has a hook structure at a distal end thereof.