Hydraulic damping mechanism and use for belt tensioning

A hydraulic damper for providing fluid damping to a tensioner in a drive system that includes a damper cup, which is mounted to the tensioner and configured to rotate about a central axle in tandem with the tensioner, an end plate having an outer face and an inner face, which is attached to the damper cup forming a fluid chamber, a peg attached to the end plate and extending away from the inner face and toward the damping cup, a damping fluid, which is contained within the fluid chamber, a plurality of shear plates housed within the fluid chamber comprising alternating fixed plates engaged with a fixed component of the tensioner and rotatable plates engaged with a rotatable component of the tensioner where the peg extends through openings in each of the shear plates allowing for rotation of the rotatable plate with the rotation of the peg.

TECHNICAL FIELD

The present invention relates generally to a damping mechanism for tensioners for a drive belt system and more particularly to a hydraulic damped tensioner utilizing a damping mechanism utilizing shear forces generated from rotating plates through a viscous fluid.

BACKGROUND

Belt tensioners use a system or mechanism to dampen tensioner movement which minimizes steady state vibrations or transient events that cause belt slip. The required magnitude of this damping depends on many drive factors including geometry, accessory loads, accessory inertia, engine duty cycle and others. For instance, drive systems that have higher torsional input or certain transient dynamic conditions may require higher damping to sufficiently control tensioner movement. Although higher damping is very effective at controlling arm movement, it can also be detrimental to other critical tensioner functions (e.g. slow or no response to slack belt conditions). In addition, variation or change in damping that occurs as a result of manufacturing variation, operating temperature and component break-in or wear can also result in undesirable tensioner responsiveness.

Damping derived by utilizing shear forces generated by rotating plates through a viscous fluid has been used with belt tensioners. One particular method involves a rotating plate and a fixed plate surrounded by a viscous fluid as in U.S. Pat. No. 4,838,839 to Watanabe. To achieve the fluid damping in Watanabe, the fixed plates are fixed directly to the fixed shaft, and the displaceable plates are fixed directly to an oscillation sleeve.

Other solutions using plates for hydraulic damping are found in U.S. Pat. Nos. 4,601,683 and 5,391,119 to Foster and Kondo respectively. These designs specifically manufacture the plates to attach directly to the rotating and fixed parts of the tensioner. This approach requires more complex manufacturing and assembly processes.

The aforementioned hydraulic damping mechanisms are not ideal. Accordingly, a new damping mechanism and tensioner design is desired.

SUMMARY

One aspect disclosed herein is a hydraulic damper for providing fluid damping to a tensioner in a drive system that includes a damper cup, which is mounted to the tensioner and configured to rotate about a central axle in tandem with the tensioner, an end plate having an outer face and an inner face, which is attached to the damper cup forming a fluid chamber, a pin attached to the end plate and extending away from the inner face and toward the damping cup, a damping fluid, which is contained within the fluid chamber, a rotatable plate having an opening configured to accept the pin through the rotatable plate and rotate about the central axle, and a fixed plate having an opening configured to accept the pin through the fixed plate, which is fixed to and does not rotate about the central axle. During wind-up and tensioning of the tensioner, a shear force is applied to the rotatable plate moving through the damping fluid to provide damping to the tensioner.

In another embodiment, the hydraulic damper includes a damper cup, which is mounted to the tensioner and configured to rotate about a central axle in tandem with the tensioner, an end plate having an outer face and an inner face, which has a central opening and is configured to accept the central axle and rotate about the central axle, and wherein the end plate is attached to the damper cup forming a fluid chamber, a ring configured to be mounted on the central axle and fit within the central opening of the end plate forming a fluid tight seal between the end plate and the central axle, a pin attached to the end plate and extending away from the inner face and toward the damping cup, a damping fluid, which is contained within the fluid chamber, a rotatable plate, which is mounted on a hub configured to be mounted on and rotate about the central axle, and the rotatable plate has an opening configured to accept the pin through the rotatable plate, and a fixed plate having an opening configured to accept the pin through the fixed plate, wherein the fixed plate is fixed to and does not rotate about the central axle.

The features, functions, and advantages discussed can be achieved independently in various embodiments of the present invention or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the invention or the application and uses of such embodiments. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.

The hydraulic damper disclosed herein provides a tensioner with hydraulic damping. The tensioner is typically part of a power system, known as a Front End Accessory Drive (“FEAD”) system where the tensioner provides tension to an endless power transmitting element such as a belt, chain, or other continuous loop in a system driven by at least one source and that also drives at least one accessory. The endless power transmitting element and the tensioner operate in concert with the tensioner providing tension to the power transmitting element as needed and responding to dynamic conditions thereof.

Engines that utilize an endless power transmitting element for driving a plurality of driven accessories is well known in the art. Additionally belt tensioners utilized to provide a tensioning force on the endless power transmitting element are also well known in the art.

Referring now toFIGS. 1 and 2, in an embodiment, the hydraulic damper100of this invention is utilized to provide damping to a tensioner124utilized in continuous belt or chain drive systems in the manner described below. The tensioner124is configured to be fixed to an engine200using a mounting bracket128. The mounting bracket128is configured with a mounting peg126which is configured to be disposed within a designated opening in the engine200. The mounting peg126allows the mounting bracket128to be correctly aligned and oriented during operation of the engine200. The mounting bracket is secured to the engine with a bolt (not shown) passing through a pivot member102. The combination of the mounting bracket128and the pivot member102serve as the support structure for the tensioner124. Additionally, the pivot member102is configured to serve as a central axle about which the tensioner124rotates. Other methods may be used to secure the mounting bracket128to the engine, such as bolts, screws, welds, or any other suitable fastener known in the art that will hold the mounting bracket128in place during operation of the engine. Additionally, the mounting bracket128may be of any configuration and include any number of openings for receiving the fasteners to mount to the engine.

In an embodiment, the pivot member102extends axially away from the engine200, through and beyond the tensioner124providing support for the hydraulic damper100. The pivot member102is stationary and fixed to the engine200and the tensioner124rotates about the pivot member102. A damper cup106, having a closed end120and an open end122is mounted on the pivot member102through a central opening in the closed end120so that the closed end122abuts the tensioner124. The open end122has an inner wall132with a notch134. Once mounted on the pivot member102, the damper cup106is configured to rotate, in tandem with the tensioner124, about the pivot member102. An end cap104is secured to the pivot member102and configured to prevent the damper cup106/tensioner124combination from sliding off the end of the pivot member102.

Fixed plates108having a diameter less than the inner diameter of the open end122is mounted on a hub118though central opening108a. The fixed plate is secured to the hub118using lobes108dand any means known in the art such that the fixed plates108remain stationary with respect to and does not rotate with the damper cup106and the tensioner124. The fixed plates108contain one or more curved openings108blocated between the central opening108aand the outer edge of the plates108. Additionally, the fixed plates108contain one or more openings108clocated between the central opening108aand the outer edge of the fixed plates108. The openings108callow a damping fluid136(FIG. 3) to completely surround and immerse the fixed plates108. In another embodiment, the fixed plates108do not contain openings108c, and have a diameter less than the inner diameter of the open end122such that a gap exists between the diameter of the fixed plates108and the inner wall132to allow the damping fluid136to completely surround and immerse the fixed plates108. Openings108bare elongated and at least one receives connecting peg130of end plate112and allows for the rotation of end plate112relative to the fixed plates108.

The hub118is mounted on pivot member102and configured to be fixed with pivot member102. Rotatable plates110having a diameter less than the inner diameter of the open end122are mounted on the hub118though central opening110a. The rotatable plates110are configured to rotate about the pivot member102. The rotatable plates110contain one or more circular openings110blocated between the central opening110aand the outer edge of the rotatable plates110. Additionally, the rotatable plates110contain one or more openings110clocated between the central opening110aand the outer edge of the rotatable plates110. The openings110callow the damping fluid136(FIG. 3) to completely surround and immerse the rotatable plates110. In another embodiment, the rotatable plates110do not contain openings110c, and have a diameter less than the inner diameter of the open end122such that a gap exists between the diameter of the rotatable plates110and the inner wall132to allow the damping fluid136to completely surround and immerse the rotatable plates110. The rotatable plates110are driven by a connecting peg130

An end plate112having an inner face112a, an outer face112b, an outer edge112c, and a notch112dlocated on the outer edge112c. The connecting peg130is fixed to the inner face112aand extends out away from the inner face112atowards the tensioner124. The end plate112is disposed within the open end122. When placing the end plate112into the open end122, the assembler aligns notch112dwith notch134forming a small opening138. The end plate112is fixed to the inner wall132forming a fluid tight seal between the end plate112and the inner wall132except for the small opening138. In another aspect, the end plate112may be properly aligned with open122using a key located on end plate112that fits within a keyway located on the inner wall132. Additionally, any other method for aligning objects which is known in the art may also be used to properly align notch112dwith notch134. Once the end plate112is fixed to the inner wall132, a fluid chamber140is created between the closed end120, the inner face112a, and the inner wall132. Additionally, the end plate112, which is fixed to the inner wall132is configured to rotate in tandem with the damper cup106and the tensioner124. The end plate112, the rotatable plate110, and the fixed plate108are aligned such that connecting peg130passes through the circular opening110band the curved slot opening108b. In another embodiment, end plate112has a central opening114. A ring116having an inner diameter equal to the outer diameter of the hub118is mounted on the hub118forming a fluid tight seal between the ring116and the hub118. The ring116has an outer diameter equal to the diameter of the central opening114. The end plate112is mounted to the ring116via the central opening114such that a fluid tight seal is formed between the end plate112and the ring116.

In an embodiment, the fluid chamber140is filled with the damping fluid136through the small opening138. After filling the fluid chamber140with the damping fluid136, the small opening138is sealed using a plug, ball bearing, or any other method known in the art that would create a fluid tight seal.

Referring toFIG. 3, in an embodiment, protrusions302protrude from the surface of the fixed plates108. The protrusions302are configured to provide a space between the fixed plates108and the closed end120of the damper cup106. Additionally, protrusions302are configured to provide a space between the fixed plates108and the rotatable plates110. Protrusions304protrude from the surface of the rotatable plates110and are configured to provide a space between the rotatable plates110and adjacent fixed plates108. In an embodiment, a plurality of fixed plates108and rotatable plates110are mounted about hub118in an alternating manner.

In an embodiment, tensioning a slack power transmitting element is an unwinding of a wound-up tensioner which will be referred to herein as the tensioning direction T. In the opposite direction, referred to herein as the winding direction W, a winding up of the tensioner occurs in response to a prevailing force of the power transmitting element which is tightening in the span where the tensioner resides. The winding of the tensioner may have some potentially deleterious effects, so to mitigate these effects it is desirable to have a damper, for example a hydraulic damper, incorporated in the tensioner to resist the movement of the power transmitting element without adversely affecting movement of the tensioner, in particular its arm to tension the power transmitting element. This kind of damping is generally known as hydraulic damping.

Referring toFIGS. 3 and 4, in an embodiment, the hydraulic damper100achieves damping when the end plate112rotates in tandem with the damper cup106and tensioner124in either the tensioning direction T or winding direction W. There are limit stops402,404, and406, which limit the travel of the tensioner124. When in a resting position, the tensioner124rests against limit stop406. As the tensioner124rotates in the winding direction W, the tensioner travels in that direction until either the belt force acting on the tensioner stops, or limit stop402meets limit stop404. When limit stops402and404come together, the tensioner124is prevented from moving further in the winding direction W. After winding, the tensioner124is biased to rotate in the tensioning direction T. When rotating in the tensioning direction T, the tensioner124continues to rotate in the tensioning direction until either the tensioner124is prevented from further rotation by the belt force or limit stop406. When the tensioner124reaches limit stop406, the tensioner124is prevented from rotating any further in the tensioning direction T.

As the rotatable plate110rotates through the surrounding damping fluid136a shear force is created between the rotatable plate110and the fixed plate108. This shear force acts in the opposite direction to the rotation of the rotatable plate110. This resistance by the shear force acts to dampen the movement of the tensioner124in either the tensioning direction T or winding direction W depending on the direction of rotation of the tensioner124. The shear force is generated each time the rotatable plate110rotates through the damping fluid136regardless of whether the rotation is in the tensioning direction T or winding direction W. Therefore, the hydraulic damper100provides damping to the tensioner124in both the tensioning direction T and the winding direction W.

In an embodiment, the hydraulic damper100may be assembled as a stand-alone unit, including all components and damping fluid136. The hydraulic damper100can then be inserted into the main body of tensioner124.

The components of the hydraulic damper100can be fabricated using a variety of techniques including forging, casting, die-casting, injection molding, sintering, or machining or fabricated in different components, or other techniques known to one of ordinary skill in the art and then joined together using a variety of methods such as sintering, welding, bonding, bolting, and even interference fits or other methods known to one of ordinary skill in the art.

The embodiments of this invention shown in the drawing and described above are exemplary of numerous embodiments that may be made within the scope of the appended claims. It is understood that numerous other configurations of the hydraulic damper100may be created taking advantage of the disclosed approach. In short, it is the applicant's intention that the scope of the patent issuing herefrom will be limited only by the scope of the appended claims.