FR2842576A1 - FREE WHEEL BEARING DEVICE AND FREE WHEEL PULLEY - Google Patents

Abstract

Freewheel bearing device 1 comprising a bearing 2 provided with a plurality of rolling elements 9 and a cage 10 for holding the rolling elements 9, and a free wheel 3 provided with a freewheel spring 14, the spring 14 comprising a first portion 17 cooperating with the cage 10 and a second portion 15 cooperating with an exterior and / or interior element, said element being secured directly or indirectly to a body on which the rolling elements 9 roll.

Description

Freewheel bearing device and freewheel pulley The present

  invention relates to the field of freewheel bearings,

  in particular freewheel spring bearings.

  Such devices include two elements that can rotate concentrically with respect to each other in freewheeling mode and between which it must be possible to pass a torque without relative movement between the two elements when the device operates in torque-taking mode. In spring-loaded freewheel devices, a helical spring generally performs the freewheeling function. The spring is secured by one of its ends to one of the two elements of the device and, in a direction of relative rotation between the two elements, rubs without clamping on a cylindrical surface of the other element. In the event of a reversal of the relative movement between the two elements, the friction portion of the spring tightens on the cylindrical seat, this tightening being caused by the diametrical expansion of the spring by the effect of unwinding in a cylindrical seat of a housing or by winding effect on the

cylindrical bearing of a shaft.

  Such freewheeling devices are used in particular in alternator pulleys in order to avoid transmitting acyclisms from the

  engine to the alternator, in particular by means of a belt.

  By being able to temporarily decouple the alternator from the engine, it is avoided, for example in the event of a sudden fall in engine speed, that the alternator becomes engine and causes a reversal of belt tension. This saves the transmission belt which

  can significantly increase its lifespan.

  Reference may be made to document WO A 98/50 709 or also to document US A 5 598 913. The bearing function is provided by one or more bearings and the freewheeling function is provided by a helical spring, one end of which is secured to 'A part linked to an internal rotating part and a number of turns of which cooperate with the cylindrical bore of an external part to transmit or not a torque between the internal and external parts according to the relative direction of rotation between these two parts. Such devices are satisfactory but nevertheless have certain drawbacks. When the device operates in freewheel, a certain number of coils of the spring rub in the external part with a significant relative speed equal to the differential angular speed between the two parts, for example between the pulley and the hub. This can lead to rapid wear of the spring and

  unwanted device failures.

  The invention seeks to increase the service life of freewheel bearings.

  The invention seeks to reduce the wear of freewheel bearings.

  The invention provides a freewheel bearing device comprising a bearing provided with a plurality of rolling elements and a cage for holding the rolling elements, and a freewheel provided with a freewheel spring. Said spring comprises a first portion cooperating with the cage and a second portion cooperating with an exterior and / or interior element, said element being secured directly or indirectly to a body on which the

rolling elements.

  The sliding speed of the spring relative to the cage or to said element is limited to substantially half the speed of rotation of the bearing. This results in a considerable reduction in the wear of the spring and of the part on which said spring rubs when it does not transmit torque. In a relative direction of rotation, the spring is sliding and the freewheel is said to be disengaged. In the opposite direction, the spring is engaged and the freewheel is said to be engaged. A couple can then be

  transmitted between the external and internal elements of the bearing.

  It is understood by direct connection that said element is either in one piece with said body, or in contact with and fixed on said body and by indirect connection that said element is fixed with said body

  through one or more interposed parts.

  In one embodiment of the invention, said spring comprises a portion integral in rotation with the cage. The spring can

  be in frictional contact with the external and / or internal element.

  Said spring may include turns cooperating with a bearing

cylindrical of said element.

  In another embodiment of the invention, said spring comprises a portion integral in rotation with said element. The spring may be in frictional contact with the cage. Said spring may

  include turns cooperating with a cylindrical bearing surface of the cage.

  In one embodiment of the invention, the freewheel

includes only one spring.

  In another embodiment of the invention, the freewheel comprises two springs, for example one mounted between the cage and

  the outer element and the other mounted between the cage and the inner element.

  In one embodiment of the invention, the bearing comprises an outer ring and an inner ring. The rolling elements are then placed between the outer and inner rings. At least one of the rings may include an axial extension able to cooperate with the spring. The axial extension can be provided with a bearing surface capable of rubbing with the spring or with a bearing surface on which a

end of the spring is fixed.

  Advantageously, the cage includes an axial extension in

  contact with the first portion of the spring.

  In one embodiment of the invention, the spring is helical. In one embodiment of the invention, the spring is

  rectangular section. The spring can thus be compact radially.

  Said element can be in one piece with said body. The invention also provides a pulley comprising a freewheel bearing device and a pulley body integral with an external element of the bearing. The freewheel bearing comprises a bearing provided with a plurality of rolling elements and a cage for holding the rolling elements, and a freewheel provided with a spring. The spring comprises a first portion cooperating with the cage and a second portion cooperating with an exterior and / or interior element, said element being integral with a body on which the rolling elements roll. As can be seen in Figures 1 to 3, a freewheel bearing 1 comprises a bearing 2 and a freewheel 3 mounted between a shaft 4 of cylindrical outer surface of revolution and a support

  outside 5 having a cylindrical bore 6.

  The bearing 2 comprises an outer ring 7, an inner ring 8, a row of rolling elements 9 and a cage 10 for holding the rolling elements 9. The outer ring 7 has an outer surface 7a mounted, for example fitted, in the cylindrical bore 6 of the outer support 5, a rolling track 7b formed on its bore, and two opposite radial front surfaces 7c and 7d. The inner ring 8 has a bore 8a mounted, for example fitted, on the outer surface of the shaft 4, a rolling track 8b formed on its outer surface, and two opposite radial front surfaces 8c and 8d. The rolling elements 9, here balls, are arranged between the rolling tracks 7b and 8b. The cage 10 comprises cells regularly distributed in the circumferential direction in which the rolling elements 9 are mounted, portions II between the cells and a circular portion 12 continues on one side of the rolling elements 9 radially between the rings 7 and 8. The cage 10 is made of molded synthetic material, for example polyamide reinforced with fibers

of glass.

  The cage 10 further comprises an axial extension 13 extending beyond the radial plane defined by the radial front surfaces 7c and 8c of the rings 7 and 8. The axial extension 13 is of generally circular shape and has an outer surface cylindrical 13a of diameter greater than that of the bore of the outer ring 7, and a cylindrical bore 13b of diameter smaller than that of the outer surface of the inner ring 8. The axial length of the extension 13 is close to that of bearing 2. The cage 10 is in one piece. The freewheel 3 further comprises the axial extension 13 of the cage 10, a spring 14 of generally helical shape. The spring 14 comprises an end 15 formed of several turns, here three, in contact with the cylindrical bore 6 of the external support 5, another end 16 formed of several turns, here three, in contact with the external surface of the shaft 4, and a central radial portion 17 passing through a radial notch formed in the extension 13 or embedded in the axial extension 13, for example by overmolding. The radial central portion 17 of the spring 14

  is thus integral in rotation with the extension 13 and the cage 10.

  The device operates as a torque, when the relative movement of the external support 5 with respect to the shaft 4 takes place in the direction of the arrow indicated in FIG. 2, for example when the shaft 4 is stationary and when the outer support 5 is driven in the direction of the arrow. Indeed, the cage 10 of the bearing rotating at an angular speed equal to the half-difference of the angular speeds of the outer 7 and inner 8 rings, if the outer ring 7 of the bearing has a relative movement relative to the inner ring 8 in the direction of the arrow, the cage 10 rotating slower than the outer ring 7, it follows that the outer turns of the spring 14 which is linked to the cage 10 by its radial portion 17, tend by friction on the cylindrical bore 6 of the external support 5 to be clamped therein. Simultaneously, the inner end 16 of the spring 14, driven by the cage 10 comes to wind and tighten on the shaft 4. The spring 14 ensures

  thus the transmission of the torque between the external support 5 and the shaft 4.

  If the radial load on the rolling elements 9 is sufficient and the torque to be transmitted relatively low, the torque can be transmitted between the outer end 15 of the spring 14 and the shaft 4 via the cage 10 and the rolling elements 9 before the inner turns of the end 16 have not tightened on the shaft 4. In this case, the inner turns of the end 16 will intervene to transmit the torque if the latter increases above a certain value and causes a

  sliding of the rolling elements 9 in their raceway 8b.

  Of course, the stiffness of the spring 14 can be chosen so that

  the torque is not transmitted by the rolling elements 9.

  If the direction of relative movement between the external support 5 and the shaft 4 is reversed, the internal turns of the end 16 of the spring 14 become loose, which allows relative angular movement with friction between the spring 14 and the shaft. 4. The outer turns of the end 15 of the spring 14 also loosen, which allows relative angular movement with friction between the spring 14 and the cylindrical bore 6 of the outer support 5. The device operates

then in freewheeling mode.

  Many variations and applications of the device can

be considered.

  FIG. 4 shows a variant in which the reference numbers of similar elements are kept. Wheel

  free 3 includes two independent internal 19 and external 20 springs.

  The spring 19 is disposed between the bore 13b of the axial extension 13 of the cage 10 and the cylindrical outer surface of the shaft 4 with a plurality of turns, here three, in contact with the bore of the extension

  axial 13 and one end 21 angularly secured to the shaft 4.

  The outer spring 20 comprises a plurality of turns, here three, in contact with the outer cylindrical surface 13a of the axial extension 13 of the cage 10 and one end 22 fixed angularly in the bore 6 of the outer support 5, for example at by means of a notch 23 formed in said bore 6 and in which the end 22 of the spring 20

protrudes.

  In a direction of relative rotation between the external support 5 and the shaft 4, the turns of the springs 19 and 20 rub on the axial extension 13 of the cage 10 and thus allow rotation without significant transmission of torque. In the other direction of relative rotation, the springs 19 and 20 come to tighten on the axial extension 13 of the cage 10 and transmit a torque while ensuring the angular fixing

  unidirectional of the external support 5 and of the shaft 4.

  In the embodiment illustrated in Figure 5, the freewheel bearing device 1 is mounted in a pulley. The external support 5 which then forms the pulley body has an external surface 24 in

  form of trapezoidal slots adapted to a poly-V type pulley.

  The cylindrical bore 6 is limited by a shoulder 25 formed at an axial end of the external support 5 and in contact with the surface

  front 7d of the outer ring 7.

  The shaft is replaced by a hub 26 also having a shoulder 27 delimiting its outer cylindrical surface and allowing axial positioning of the inner ring 8 of the bearing 2. The

hub 26 has a bore 28.

  The embodiment illustrated in Figure 6 is intended for applications where the torque to be transmitted is relatively low. This embodiment is to be compared to that of FIG. 4 except that it has no external spring. The bore 6 of the outer support 5 is therefore also devoid of a notch. The freewheel 3 has a single spring, namely the inner spring 19, the free end 21 of which is integral in rotation with the shaft 4 and the turns of which rub against the bore 13b of the axial extension 13 of the cage 10. In blocking mode, the turns in radial extension come to block in the bore 13b of the radial extension 13 and therefore secure the cage 10 with the shaft 4. The rolling elements 9 are therefore also secured to the shaft 4 and the outer ring 7 secured to the outer support 5 remains stationary with respect to the shaft 4 insofar as the torque to be transmitted is not too great and the radial load of the bearing 2 is sufficient. This is a particularly economical embodiment. The embodiment of FIG. 7 is also of the economic type with a single spring, namely the outer spring 20. For the rest, this embodiment is similar to that of FIG. 4. It is like for the mode of embodiment of FIG. 6 of an economic variant equipped with a single spring arranged here between the extension

  radial 13 of the cage 10 and the external support 5.

  The embodiment of Figure 8 is similar to the embodiment of Figure 1 except that the spring has no outer part. The spring which bears the reference 29 comprises an inner part 15 similar to that of FIG. 1 and a radial portion 17 directed towards the outside and interfering with the axial extension 13 of the cage 10. More precisely, said axial extension 13 is provided a notch 18 extending radially from its bore towards the outside over part of its radial height and disposed at its free axial end opposite to the rolling elements 9. The radial portion 17 of the spring 29 is in protruding into said notch 18 and secures in rotation the radial portion 17 which forms a

  end of the spring 29 and of the cage 10.

  This embodiment is therefore also of the economic type.

  with a single spring arranged on one side of the cage, here inside.

  In torque transmission mode the inner portion 15 of the spring 29 is engaged with the shaft 4 while in disengaged mode, the turns of the inner portion 15 are in contact with the shaft 4 with a slight

  friction. The cage 10 then rotates freely by adding to the shaft 4.

  The embodiment illustrated in FIG. 9 is similar to that of FIG. 1. The freewheel comprises a single spring 30 disposed between the axial extension 13 of the cage 10 and the external support 5. The spring 30 comprises turns forming an outer portion 16 similar to that illustrated in FIG. 1 and a radial portion 17 projecting into a notch 18 extending radially inward from the outer cylindrical surface 13a of the axial extension 13 of the cage 10 and formed at the free axial end of the extension 13 opposite the rolling elements 9. The radial portion 17 disposed in the notch 18 is secured in rotation with the cage 10 while the turns forming the outer portion 16 are tightened in the cylindrical bore 6 of the external support 5 thus ensuring a transmission of torque, or, in the case of a reverse relative rotation, rotate at the same angular speed as the cage 10 with a slight fr silly by

  report to said bore 6 of the external support 5.

  In the embodiment illustrated in FIG. 10, the free wheel 3 is integrated in the bearing 2. More specifically, the outer ring 7 comprises an axial extension 31 on the side of the free wheel 3 which has radial dimensions identical to the rest of the outer ring 7. Similarly, the inner ring 8 comprises an axial extension 32 which has the same bore as the inner ring 8 and an outer cylindrical surface of smaller diameter, for example substantially equal to that of the bottom of the raceway 8b. The cage comprises an axial extension 33 of the same internal and external diameters as the circular portion 12 and that the portions II formed

  between the cells in which the rolling elements are arranged 9.

  A spring 29 similar to that mounted in the embodiment illustrated in FIG. 8 but of smaller dimension comprises an inner portion 15 provided with a plurality of turns in contact with the cylindrical outer surface of the axial extension 32 of the inner ring 8, and a radial portion 17 projecting into the axial extension 33 of the cage 10, more specifically projecting into a radial blind hole, not shown, formed from the bore of the axial extension 33 and oriented towards the outside, or embedded in the material constituting the extension

axial 33.

  Thus, the spring 29 has one end, namely the radial portion 17, integral in rotation with the cage 10 and another end formed by the turns of the inner portion 15 and which is capable either of being integral in rotation with the ring inner 8 in torque transmission mode, or to move with a slight friction with respect to said outer surface of the axial extension 32 of the inner ring 8 in freewheeling mode where the outer 7 and inner 8 rings move at different angular speeds. This embodiment is very compact and combines the bearing functions with

bearing and freewheel.

  In general, one can also consider providing the device illustrated in Figure 1 with two springs such as the springs 28 and 29 of the embodiments of Figures 8 and 9 thus replacing the spring 14. The embodiment illustrated in the figure 10 could perfectly be fitted with springs of the types illustrated in the other embodiments, in particular the spring 14 in FIG. 1 or be

provided with two springs 29 and 30.

  Generally, during freewheeling operation, the friction between the coils of the spring and the corresponding friction surface occurs at a reduced relative speed resulting directly from the differential angular speed between the bearing cage and the bearing ring at which is related the friction range. The wear of the spring by friction is therefore considerably reduced since the bearing cage rotates at an angular speed equal to the half-difference of the angular speeds of the rings. If N is the differential angular speed between the outer ring and the inner ring of the bearing in freewheeling operation, the differential angular speed between the spring and its friction surface will be equal to N / 2 according to the invention instead of N in the case of the prior art. We understand that this results in a significant increase in the duration of

life of the system according to the invention.

Claims (10)

  1 - Bearing device (1) with free wheel comprising a bearing (2) provided with a plurality of rolling elements (9) and a cage (10) for holding the rolling elements, and a free wheel (3) provided with a freewheel spring (14), characterized in that said spring comprises a first portion (17) cooperating with the cage (10) and a second portion (15) cooperating with an external and / or internal element, said element being secured directly or indirectly to a body on   which roll the rolling elements.   2 - Device according to claim 1, characterized in that   said spring comprises a portion (17) integral in rotation with the cage.   3 - Device according to claim 2, characterized in that said spring comprises turns (14) cooperating with a bearing cylindrical of said element.   4 - Device according to claim 1, characterized in that said spring comprises a portion (21) integral in rotation with said element. Device according to Claim 4, characterized in that the said spring comprises turns co-operating with a cylindrical surface of the cage (10).   6 - Device according to any one of claims   previous, characterized in that the freewheel comprises only one spring (14).   7 - Device according to any one of claims 1 to 5,   characterized by the fact that the freewheel comprises two springs.   8 - Device according to any one of claims   previous, characterized in that the bearing comprises a ring   outer (7) and an inner ring (8).   9 -A device according to any one of claims   above, characterized in that the cage (10) comprises a   axial extension (13) in contact with the first portion of the spring.   - Device according to any one of the claims   above, characterized in that the spring is helical.   II - Device according to any one of the claims   above, characterized in that the spring is of rectangular section.   12 - Device according to any one of claims   above, characterized in that said element is in one piece with said body.   13 - Pulley comprising a device according to any one of   previous claims and a pulley body (5) integral with the outer ring (7) of the bearing.