WO2001092745A1

WO2001092745A1 - Over-running clutch pulley with floating spring member

Info

Publication number: WO2001092745A1
Application number: PCT/US2001/017514
Authority: WO
Inventors: Russell Monahan; Randall King; John Miller
Original assignee: Ntn Corporation
Priority date: 2000-05-31
Filing date: 2001-05-28
Publication date: 2001-12-06
Also published as: WO2001091938A1; JP2003535281A; EP1208312A1; WO2001091939A1; JP2003535287A; WO2001092742A1; WO2001092743A1; EP1285177A1; EP1208318A1; EP1208310A1; EP1208316A1; JP2003535283A; EP1284832A1; JP2003535278A; EP1284831A1; JP2003535282A; WO2001092740A1; EP1208315A1; EP1208310A4; EP1208315A4

Abstract

An over-running clutch pulley (10) includes a sheave member (20), a hub member (22) located substantially concentrically within the sheave member, and a spring (24). The sheave member preferably includes a sheave input section (26) adapted to engage an input device (12) and a sheave collar section (32) defining a sheave collar surface (34). The hub member preferably includes a hub output section (36) adapted to engage an output device (14) and a hub clutch section (38) defining a hub flange surface (42). The sheave collar surface and the hub flange surface preferably cooperate to substantially define a spring cavity (44) with a cavity axial length (Lc) greater than a static axial length (Ls) of the spring member plus a first predetermined length to avoid substantial contact between the spring member, the sheave member, and the hub member, and less than the static axial length (Ls) of the spring member plus a second predetermined length to avoid substantial buckling of the spring member.

Description

OVER-RUNNING CLUTCH PULLEY WITH FLOATING SPRING MEMBER

TECHNICAL FIELD This invention relates generally to devices in the over-running clutch field, and more specifically to an improved over-running clutch pulley for use with an accessory device driven by an automotive engine with a belt drive.

BACKGROUND

During the operation of an automotive engine, a drive belt is typically used to power and operate various accessory devices. One of these accessory devices is typically an automotive alternator, which provides electrical power to the automobile. While several arrangements of drive belts are in use, the serpentine arrangement, which drives several accessory devices, is currently most favored. Serpentine arrangements typically include a drive pulley connected to the crankshaft of the engine (the "output device") and a drive belt trained about the drive pulley. The drive belt is also trained about one or more conventional driven pulleys, which are connected to the input shafts of various accessories devices (the "input device").

Most conventional driven pulleys are made from a one-piece design with no overrunning capabilities. In other words, the conventional driven pulleys are rigidly mounted to the input shaft and are incapable of allowing relative rotational movement between any section of the driven pulley and the input shaft. As a result of the lack of any over-running capabilities and of the generation of significant inertia by the accessory, relative slippage between the drive belt and the driven pulley may occur if the drive belt suddenly decelerates relative to the input shaft. The relative slippage may cause an audible squeal, which is annoying from an auditory standpoint, and an undue wear on the drive belt, which is undesirable from a mechanical standpoint.

In a typical driving situation, the drive belt may experience many instances of sudden deceleration relative to the input shaft. This situation may occur, for example, during a typical shift from first gear to second gear under wide open throttle acceleration. This situation is worsened if the throttle is closed or "back off immediately after the shift. In these situations, the drive belt decelerates very quickly while the driven pulley, with the high inertia from the accessory device, maintains a high rotational speed, despite the friction between the drive belt and the driven pulley.

In addition to the instances of sudden deceleration, the drive belt may experiences other situations that cause audible vibration and undue wear. As an example, a serpentine arrangement with conventional driven pulleys may be used with an automobile engine that has an extremely low idle engine speed (which may increase fuel economy). In these situations, the arrangement typically experiences "belt flap" of the drive belt as the periodic cylinder firing of the automotive engine causes the arrangement to resonate within a natural frequency and cause an audible vibration and an undue wear on the drive belt.

The disadvantage of the conventional driven pulleys, namely the audible squeal, the undue wear, and the vibration of the drive belt, may be avoided by the use of an over-running clutch pulley instead of the conventional driven pulley. An over-running clutch pulley allows the pulley to continue to rotate at the same rotational speed and in a same rotational direction after a sudden deceleration of the drive belt. In a way, the over-running clutch pulley functions like the rear hub of a typical bicycle; the rear hub and rear wheel of a conventional bicycle continue to rotate at the same rotational speed and in the same rotational direction even after a sudden deceleration of the pedals and crankshaft of the bicycle. An example of an over-running clutch pulley is described in U.S. Patent No. 5,598,913 issued to the same assignee of this invention and hereby incorporated in its entirety by this reference.

Since many customers of new automobiles are demanding longer lives, with relatively fewer repairs, for their new automobiles, there is a need in the automotive field, if not in other fields, to create an over-running clutch pulley with increased wear resistance. This invention provides an over-running clutch pulley with features intended to increase wear resistance, while minimizing cost and weight of the over-running clutch pulley.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an over-running clutch pulley of the invention, shown with a drive belt as the input device and a cylindrical shaft as the output device;

FIG. 2 is a partial cross-section view, taken along the line 2-2 of FIG. 1 , of the overrunning clutch pulley of a preferred embodiment; and

FIG. 3 is a perspective view of the spring member of the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The following description of the preferred embodiment of the invention is not intended to limit the scope of this invention to this preferred embodiment, but rather to enable any person skilled in the art of over-running clutches to make and use this invention.

As shown in FIG. 1 , the invention includes an over-running clutch pulley 10 for rotationally engaging an input device 12 and an output device 14. The over-running clutch pulley 10 has been designed for use with a drive belt 16 as the input device 12, and with a cylindrical shaft 18 as the output device 14. More specifically, the over-running clutch pulley 10 has been particularly designed for use with a drive belt 16 with a grooved surface and a cylindrical shaft 18 of an automotive alternator. The over-running clutch pulley 10 may be used, however, in other environments, with other suitable input devices, such as smooth belt, a toothed belt, a V- shaped belt, or even a toothed gear, and with other suitable output devices, such as a polygonal shaft. Furthermore, the over-running clutch pulley 10 may be used in an environment with two devices that alternate their rotational input responsibilities, and in an environment with an "output device" that actually provides rotational input and with an "input device" that actually receives rotational input. In these alternative embodiments, the terms "input device" and "output device" are interchangeable.

As shown in FIG. 2, the over-running clutch pulley 10 of the preferred embodiment includes a sheave member 20, a hub member 22 located substantially concentrically within the sheave member 20, and a spring member 24, which cooperate to rotationally engage the drive belt and the cylindrical shaft. The sheave member 20 preferably includes a sheave input section 26 adapted to the engage the input device, a sheave clutch section 28 defining a sheave clutch surface 30, and a sheave collar section 32 defining a sheave collar surface 34. Similarly, the hub member 22 preferably includes a hub output section 36 adapted to engage the output device, and a hub clutch section 38 defining a hub clutch surface 40 and a hub flange surface 42 substantially opposite the sheave collar surface 34. The sheave collar surface 34, the sheave clutch surface 30, the hub clutch surface 40, and the hub flange surface 42 preferably cooperate to substantially define a spring cavity 44. Preferably, the spring cavity 44 defines a cavity axial length L_c greater than a static axial length L_s of the spring member 24 plus a first predetermined length to avoid substantial contact between the spring member 24 and the sheave member 20 and the hub member 22. Also preferably, the spring cavity 44 defines the cavity axial length L_c less than the static axial length L_s of the spring member 24 plus a second predetermined length to avoid substantial buckling of the spring member 24. Avoiding substantial contact increases wear resistance for the over-running clutch pulley 10 and avoiding buckling improves torque capacity, while minimizing cost and weight.

The over-running clutch pulley 10 of alternative embodiments may include other elements, such as a sealing member to substantially prevent passage of dirt into and grease out of the over-running clutch pulley 10, or any other suitable elements that do not substantially interfere with the functions of the sheave member 20, the hub member, and the spring member 24.

The sheave input section 26 of the sheave member 20 of the preferred embodiment functions to engage the drive belt. To substantially prevent rotational and axial slippage of the sheave member 20 and the drive belt, the sheave input section 26 preferably defines a sheave input surface 46 with two sheave input shoulders 48 and at least one sheave input groove 50. The sheave input section 26 may alternatively define other suitable surfaces, such as toothed surfaces or ribbed surfaces, to engage the input device. The sheave input surface 46 is preferably outwardly directed (away from the rotational axis of the over-running clutch pulley 10) and is preferably substantially cylindrically shaped. The sheave input section 26 is preferably made from conventional structural materials, such as steel, and with conventional methods, but may alternatively be made from other suitable materials (as described below) and from other suitable methods.

The hub output section 36 of the hub member 22 of the preferred embodiment functions to engage the cylindrical shaft. The hub output section 36 preferably defines a hub output surface 52 with a smooth section 54 (which functions to ease and center the assembly of the over-running clutch pulley 10 onto the cylindrical shaft), a threaded section 56 (which functions to substantially prevent rotation and to axially retain the hub member 22 to the cylindrical shaft), and a hexagonal section 58 (which functions to mate with an alien wrench for easy tightening and loosening of the over-running clutch pulley 10 onto and off of the cylindrical shaft). Of course, the hub output section 36 may include other suitable devices or define other surfaces to prevent rotational and axial slippage, to engage the cylindrical shaft, and to engage a tool for tightening or loosening the over-running clutch pulley 10 onto and off of the cylindrical shaft. The hub output surface 52 is preferably inwardly directed (toward the rotational axis of the overrunning clutch pulley 10) and is preferably substantially cylindrically shaped. The hub output section 36 is preferably made from conventional structural materials, such as steel, and with conventional methods, but may alternatively be made from other suitable materials (as described below) and from other suitable methods.

The over-running clutch pulley 10 of the preferred embodiment also includes a bearing member 60, which functions to allow relative rotational movement of the sheave member 20 and the hub member 22. The bearing member 60, which is preferably a rolling element type, preferably includes an outer race element 62 preferably press-fit mounted on the sheave member 20, an inner race element 64 preferably press-fit mounted on the hub member 22, ball bearing elements 66 preferably located between the outer race element 62 and the inner race element 64, and bearing seals 68 preferably extending between the outer race element 62 and the inner race element 64 on either side of the ball bearing elements 66. The bearing member 60 may alternatively be of other suitable types, such as a journal bearing or a roller bearing, may alternatively include other suitable elements, and may alternatively be mounted in other suitable manners. The bearing member 60 is a conventional device and, as such, is preferably made from conventional materials and with conventional methods, but may alternatively be made from other suitable materials and with other suitable methods.

The sheave clutch section 28 and the hub clutch section 38 of the preferred embodiment function to provide the sheave clutch surface 30 and the hub clutch surface 40, respectively, for the engagement with the spring member 24. The sheave clutch section 28 preferably extends radially inward from the sheave member 20. In this manner, the sheave clutch section 28 is preferably made from the same material and with the same methods as the sheave input section 26, but may alternatively be made from other suitable materials and with other suitable methods. The hub clutch section 38 preferably extends radially outward from and axially over the hub output section 36. In this manner, the hub clutch section 38 is preferably made from the same material and with the same methods as the hub output section 36, but may alternatively be made from other suitable materials and with other suitable methods. The hub clutch section 38 preferably partially defines a spring cavity 44 to contain the spring member 24.

In the preferred embodiment, the sheave clutch surface 30 and the hub clutch surface 40 are located substantially adjacent with an axial gap 70 between each other. The sheave clutch surface 30 and the hub clutch surface 40 are preferably inwardly directed (toward the rotational axis of the over-running clutch pulley 10) and are preferably substantially cylindrically shaped. Furthermore, the sheave clutch surface 30 and the hub clutch surface 40 preferably have a similar radial diameter, a similar axial length, and a similar smooth finish. These features allow optimum performance of the spring member 24. The sheave clutch surface 30 and the hub clutch surface 40 may alternatively have differences with each other on these, or other, design specifications.

The spring member 24 of the preferred embodiment functions to engage the sheave clutch surface 30 and the hub clutch surface 40 upon the acceleration of the sheave member 20 in a first rotational direction relative to the hub member 22, and to disengage the sheave clutch surface 30 and the hub clutch surface 40 upon the deceleration of the sheave member 20 in the first rotational direction relative to the hub member 22. In the preferred embodiment, the spring member 24 includes several coils 72. The spring member 24, which is made from conventional materials and with conventional methods, accomplishes the above features by the particular size and orientation of the spring member 24 within the spring cavity 44. In alternative embodiments, the spring member 24 may include other suitable devices that accomplish the above features.

The spring member 24 is preferably designed with a relaxed spring radial diameter that is sized slightly greater than an inner diameter of the sheave clutch surface 30 and the hub clutch surface 40. Thus, when inserted into the spring cavity 44 and when experiencing no rotational movement of the sheave member 20 or the hub member 22, the spring member 24 frictionally engages with and exerts an outward force on both the sheave clutch surface 30 and the hub clutch surface 40. Further, the spring member 24 is preferably oriented within the spring cavity 44 such that the coils extend axially in the first rotational direction from the sheave clutch surface 30 to the hub clutch surface 40. With this orientation, relative rotational movement of the sheave member 20 and the hub member 22 will result in an unwinding or winding of the spring member 24. In other words, acceleration of the sheave member 20 in the first rotational direction relative to the hub member 22 will bias an unwinding of the spring member 24 and deceleration of the sheave member 20 in the first rotational direction relative to the hub member 22 will bias a winding of the spring member 24.

The unwinding of the spring member 24 tends to increase the outward force of the spring member 24 on the sheave clutch surface 30 and the hub clutch surface 40, thereby providing engagement, or "lock", of the sheave member 20 and the hub member 22. This engagement condition preferably occurs upon the acceleration of the sheave member 20 in the first rotational direction relative to the hub member 22. On the other hand, the winding of the spring member 24 tends to decrease the outward force of the spring member 24 on the sheave clutch surface 30 and the hub clutch surface 40, thereby allowing disengagement, or "slip", of the sheave member 20 and the hub member 22. This disengagement condition preferably occurs upon the deceleration of the sheave member 20 in the first rotational direction relative to the hub member 22.

The sheave collar surface 34 and the hub flange surface 42 function to define the spring cavity 44 and to insure the proper placement of the spring member 24 within the spring cavity 44. The sheave collar surface 34 is preferably defined by the sheave collar section 32, which preferably extends radially inward from the sheave input section 26 and adjacent the sheave clutch section 28. In this manner, the sheave collar section 32 is preferably made from the same material and with the same methods as the sheave input section 26, but may alternatively be made form other suitable materials and with other suitable methods. The hub flange surface 42 is preferably defined by the hub clutch section 38, which preferably extends radially outward from the hub output section 36. The sheave collar surface 34 and the hub flange surface 42 may alternatively be defined by other sections of the over-running clutch pulley 10 or by other suitable devices.

Because substantial contact between the spring member 24 and the sheave collar surface 34 or the hub flange surface 42 may cause undue wear of the over-running clutch pulley 10, the spring cavity 44 preferably defines the cavity axial length L_c greater than the static axial length L_s of the spring member 24 plus a first predetermined length. The term "static axial length" preferably refers to a length from one end of the spring member 24 to the other end of the spring member 24 while the spring member 24 is located within the spring cavity 44 and during a condition of no rotational movement of the sheave member 20 and no rotational movement of the hub member 22. The first predetermined length preferably equals 0.25 times the spring coil thickness of the spring member 24. The term "spring coil thickness" preferably refers to a length from one side of an individual spring coil to the other side of the individual spring coil. A spring member 24 with cylindrical spring coils will have a spring coil thickness equal to the diameter of the cylindrical spring coil.

In the other extreme, an excessive gap between the spring member 24 and the sheave collar surface 34 or the hub flange surface 42 may allow cocking of the individual spring coils during the engagement condition resulting in substantial buckling of the spring member 24 within the spring cavity 44. For this reason, the spring cavity 44 preferably defines the cavity axial length L_c less than the static axial length U of the spring member 24 plus a second predetermined length. The second predetermined length preferably equals 0.75 times the spring coil thickness of the spring member 24. Avoiding substantial contact and buckling increases wear resistance for the over-running clutch pulley 10, while minimizing cost and weight.

As shown in FIG. 3, the spring member 24 of the preferred embodiment preferably includes two squared ends 74. This feature, which is less expensive to manufacture than a spring member 24 with flush ground ends, is available because of the "floating" nature of the spring member 24 (the small axial gap on either side of the spring member 24 within the spring cavity). In alternative embodiments, the spring member 24 may include only one squared end or no squared ends 74.

As any person skilled in the art of over-running clutches will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiment of the invention without departing from the scope of this invention defined in the following claims.

Claims

CLAIMS We Claim:

1. An over-running clutch pulley for rotationally engaging an input device and an output device, comprising: a sheave member including a sheave input section adapted to engage the input device, a sheave clutch section extending axially inward from said sheave input section and defining a sheave clutch surface, and a sheave collar section extending radially inwardly from said sheave input section and adjacent said sheave clutch section and defining a sheave collar surface; a hub member located substantially concentrically within said sheave member and including a hub output section adapted to engage the output device, a hub clutch section extending radially outward from said hub output section, defining a hub clutch surface substantially adjacent said sheave clutch surface, and defining a hub flange surface substantially opposite said sheave collar surface; wherein said sheave collar surface, said sheave clutch surface, said hub clutch surface, said hub flange surface cooperate to substantially define a spring cavity; and a spring member located substantially within said spring cavity adapted to engage said sheave clutch surface and said hub clutch surface upon the acceleration of said sheave member in a first rotational direction relative said hub member, and to disengage said sheave clutch surface and said hub clutch surface upon the deceleration of said sheave member in the first rotational direction relative said hub member, wherein said spring member defines a static spring axial length while located substantially within said spring cavity and during a condition of no rotational movement of said sheave member and no rotational movement of said hub member; wherein said spring cavity defines a cavity axial length greater than said static spring axial length plus a first predetermined length to avoid substantial contact between said spring member and said sheave member and said hub member, and less than said static spring axial length plus a second predetermined length to avoid substantial buckling of said spring member.

2. The over-running clutch pulley of Claim 1 wherein said sheave input section defines a sheave input surface with two sheave shoulders and at least one sheave input groove that cooperate to engage a grooved belt as the input device and to substantially prevent rotational and axial slippage between said sheave input surface and the grooved belt.

3. The over-running clutch pulley of Claim 1 wherein said sheave clutch surface is inwardly directed and substantially cylindrically shaped.

4. The over-running clutch pulley of Claim 1 wherein said spring member includes several coils, said coils individually defining a spring coil thickness.

5. The over-running clutch pulley of Claim 4 wherein said first predetermined length equals 0.25 times said spring coil thickness.

6. The over-running clutch pulley of Claim 5 wherein said second predetermined length equals 0.75 times said spring coil thickness.

7. The over-running clutch pulley of Claim 1 wherein said spring member includes a squared end.

8. The over-running clutch pulley of Claim 7 wherein said spring member includes two squared ends.

9. The over-running clutch pulley of Claim 1 further comprising a bearing member located between said sheave member and said hub member, and adapted to allow relative rotational movement of said sheave member and said hub member.

10. The over-running clutch pulley of Claim 1 wherein said hub output section defines a hub output surface adapted to engage a cylindrical shaft as the output device.

11. The over-running clutch pulley of Claim 1 wherein said hub clutch surface is inwardly directed and substantially cylindrically shaped.