OVERRUNNING CLUTCH DAMPENER

RELATED APPLICATION

[0001] Priority is claimed under Indian Provisional application number 3332/CHE/2011 filed on 26 September, 2011, titled 'Overrunning clutch dampener', which is incorporated herein by its reference.

TECHNICAL FIELD OF THE INVENTION

[0002] Embodiments of the invention generally relate to the field of clutch pulleys, and more particularly to a dampener in an overrunning clutch pulley.

BACKGROUND OF THE INVENTION

[0003] Overrunning clutch pulley (OCP) or free wheel pulley is used in automotive application for alternators. The OCP work on the principle of overrunning clutch mechanism which is based on differential circumferential speed between races. The free wheel pulley overruns when there is a differential speed between an engine shaft (driver) and an alternator shaft (driven). The OCP decouples inertial force of an alternator during speed variation of an engine which in turn leads to elimination of vibration, belt slip and belt squeal noise in the engine. Thus, with improvement in noise and vibration harshness (NVH), life of the belt, life of the OCP and life of entire drive system improve.

[0004] However, each time when a cylinder fires, crankshaft speeds up and slows down. These firing pulses are known as torsional vibration. The lower the rotations per minute (RPM) of the engine, higher is the torsional vibration. These firing pulses that act on alternator rotor, try to speed it up and slow it down several times during every revolution of the engine. These firing pulses create vibration for the driver and cause the belt tensioner to exhibit increased movement. Increased tensioner movement affects life of the tensioner and the belt, as well as other components within the belt drive system, including the alternator.

[0005] The use of sprag type clutches for higher torque in the OCP system is known. However, requiring large number of sprags in turn increases friction of the free wheel pulley during overrunning mode, and thus the noise. The limitation of the sprag clutch system is overcome by using a roller one way clutch or free wheel clutch in the pulley system. However, manufacturing components for such a system is not easy as well as cost effective.

[0006] Though the clutch mechanism in free wheel pulleys disengages the alternator shaft (free-wheel) from the belt drive system during engine deceleration, such an arrangement may not remove the torsional vibration completely.

SUMMARY OF THE INVENTION

[0007] An overrunning clutch dampener is disclosed. According to one aspect of the present invention, an overrunning clutch pulley includes a pulley having an outer surface and an inner surface. The outer surface is adapted to engage a belt. The overrunning clutch pulley also includes a one way clutch having an outer ring. Further, the overrunning clutch pulley includes a dampening element having a first attachment and a second attachment. According to the present invention, the dampening element is adapted to absorb torsional vibrations between the first attachment and the second attachment. The first attachment is coupled to the pulley and the second attachment is coupled to the outer ring of the one way clutch.

[0008] The pulley has an eccentric cut on the inner surface to self lock with the first attachment of the dampening element. Also, the outer ring of the one way clutch has an eccentric cut to self lock with the second attachment of the dampening element. The dampening element includes a torsion spring, a rubber bush or a compression spring. The one way clutch is a roller type one way clutch. During engine deceleration, the one way clutch disengages from the pulley to reduce force on the pulley.

[0009] According to another aspect of the present invention, a method of dampening vibrations in an overrunning clutch pulley used in a vehicle is disclosed. Other features of the embodiments will be apparent from the accompanying drawings and from the detailed description that follows.

BRIEF DESCRIPTION OF THE INVENTION

[0010] Example embodiments of the present invention are illustrated by accompanying drawings, wherein:

[0011] Fig. 1 illustrates an overrunning clutch pulley with a dampening system, according to one embodiment;

[0012] Fig. 2 illustrates an exploded view of the overrunning clutch pulley of Fig. 1;

[0013] Fig. 3 illustrates eccentric cuts and that self locks with a torsion spring of the overrunning clutch pulley of Fig. 1;

[0014] Fig. 4 is an example of the dampening element of the overrunning clutch pulley of Fig. 1.

[0015] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present invention in any way.

DETAILED DESCRIPTION

[0016] An overrunning clutch dampener is disclosed. The following description is merely exemplary in nature and is not intended to limit the present invention, applications, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0017] Fig. 1 illustrates an overrunning clutch pulley 100 with a dampening system, according to one embodiment. The overrunning clutch pulley 100 includes a pulley 102, a one way clutch 106 and a dampening element. In one example, the dampening element is a torsional vibration dampener such as a torsion spring 104. The one way clutch 106, for example, is a roller type one way clutch. The roller type one way clutch has optimized torque capacity and provides low overrunning friction in the overrunning clutch pulley 100. According to an embodiment of the present invention, the torsion spring 102 includes a first attachment that is coupled to the pulley 102 and a second attachment that is coupled to the roller type one way clutch.

[0018] The torsion spring 104 acts as a dampener by absorbing torsional vibrations between the first attachment and the second attachment. Thus, vibrations from the pulley 102 are absorbed by the torsion spring 104, thereby reducing force transmitted to the one way clutch 106 and also to an alternator shaft. Further, the one way clutch 106 is designed to disengage belt running on the pulley 102 from the alternator shaft during engine deceleration to avoid vibrations on the belt. The overrunning clutch pulley 100 as shown in Fig. 1 and explained in detailed in the following description results in improved belt life, reduced noise and vibrations, as well as improved engine life.

[0019] Fig. 2 illustrates an exploded view 200 of the overrunning clutch pulley 100 of Fig. 1. As shown, the overrunning clutch pulley 100 includes an inner race way 202, a cage 204 (a polymer cage, for example), the torsion spring 104, the pulley 102, a clutch outer ring 206 of the one way clutch 106, and a bearing 208. The pulley 102 has a belt running on its outer surface. The pulley 102 also has an inner surface that has an eccentric cut 210. The torsion spring 104 is self locked at its first attachment to the pulley 102 at the eccentric cut 210. The clutch outer ring 206 also has an eccentric cut 212 to which the second attachment of the torsion spring 104 is self locked. This arrangement enables the torsion spring 104 to absorb all the vibrations transmitted from the pulley 102 to inner parts of the overrunning clutch pulley 100. Thus, fewer vibrations pass on to the clutch outer ring 206 and also to an inner shaft which connects to the alternator shaft.

[0020] Further, during engine deceleration, when the engine RPM (rotations per minute) goes down, and the alternator RPM is higher, the one way clutch 106 disengages from the pulley 102. This avoids force from the alternator, for example, inertial rotating force being transmitted to the belt running on the pulley 102.

[0021] The cage 204 may be made of any suitable material as may be envisaged by a person skilled in the art. The cage 204 includes rollers which are supported by compression springs. The rollers are also called needles depending upon what L/D ratio (Length by Diameter) they adhere to, based on varying requirements to suit specific designs. The compression springs used in the cage 204 could be of any suitable material and design, for example, a solid rubber, a flat spring, a coiled spring, etc. The bearing 208 provides relative rotation between the inner race way 202 and the pulley 102.

[0022] Fig. 3 illustrates the eccentric cuts 210 and 212 that self locks with the torsion spring 104 of the overrunning clutch pulley of Fig. 1. The eccentric cuts 210 and 212 enables coupling of the torsion spring 104 in the overrunning clutch pulley 100. The eccentric cuts 210 and 212 also prevent independent movement of the clutch outer ring 206 within the pulley 102.

[0023] Fig. 4 is an example of the dampening element 402 of the overrunning clutch pulley of Fig. 1. The dampening element according to the present invention is a torsion spring (the torsion spring 104 of Fig. 1). Other examples of the dampening element include a rubber bush, a compression spring, and the like. When the pulley 102 is driven by the belt which runs over it, force is transmitted to the clutch outer ring 206 through the torsion spring 104. Such an arrangement reduces, or dampens the torsional vibration and prevents transmission of the vibrations to the inner shaft which in turn connects to the alternator shaft.

[0024] In various embodiments, the overrunning clutch pulley 100 includes a high sensitive clutch mechanism with low overrunning friction. The dampening system in the overrunning clutch pulley 100 effectively reduces vibrations and is a robust system without affecting any primary functions. The noise and vibration harshness is reduced, thereby improving belt life. Further, fewer components are involved which attributes to lighter weight of the overrunning clutch pulley 100. Even though the invention is described with respect to applications in vehicles, embodiments of the present invention are useful in other applications that would involve a drive mechanism with or without involving a heavier mass to be driven.

[0025] It will be recognized that the above described subject matter may be embodied in other specific forms without departing from the spirit or essential characteristics of the disclosure. Thus, it is understood that, the subject matter is not to be limited by the foregoing illustrative details, but it is rather to be defined by the appended claims.

REFERENCE NUMERALS

100 overrunning clutch pulley
102 pulley
104 torsion spring
106 one way clutch
202 inner race way
204 cage
206 clutch outer ring
208 bearing
210 eccentric cut
212 eccentric cut
402 dampening element

CLAIMS

We claim:

1. An overrunning clutch pulley comprising:
a pulley having an outer surface and an inner surface, wherein the outer surface is adapted to engage a belt;

a one way clutch comprising an outer ring; and

a dampening element having a first attachment and a second attachment, wherein the dampening element is adapted to absorb torsional vibrations between the first attachment and the second attachment, and wherein the first attachment is coupled to the pulley and the second attachment is coupled to the outer ring of the one way clutch.

2. The overrunning clutch pulley of claim 1, wherein the pulley has an eccentric cut on the inner surface to self lock with the first attachment of the dampening element.

3. The overrunning clutch pulley of claim 1, wherein the outer ring of the one way clutch has an eccentric cut to self lock with the second attachment of the dampening element.

4. The overrunning clutch pulley of claim 1, wherein the dampening element comprises at least one of a torsion spring, a rubber bush and a compression spring.

5. The overrunning clutch pulley of claim 1, wherein the one way clutch is a roller type one way clutch.

6. The overrunning clutch pulley of claim 1, wherein the one way clutch disengages from the pulley during engine deceleration to reduce force on the pulley.

7. Method of dampening vibrations in an overrunning clutch pulley used in a vehicle, wherein the overrunning clutch pulley comprises a pulley having an outer surface and an inner surface, wherein the outer surface is adapted to engage a belt, a one way clutch comprising an outer ring, and a dampening element having a first attachment and a second attachment, wherein the dampening element is adapted to absorb torsional vibrations between the first attachment and the second attachment, and wherein the first attachment is coupled to the pulley and the second attachment is coupled to the outer ring of the one way clutch.