NL1043881B1 - Transverse segment for a drive belt with a carrier ring and multiple transverse segments - Google Patents

Abstract

The invention relates to a transverse segment (32) made from steel for a metal drive belt (3) and provided with two cut-outs (33) that are each bounded in one direction by a 5 radially outwardly facing saddle surface (42) of the transverse segment (32) for supporting a carrier ring (31) of the metal drive belt (3). According to the invention, the saddle surfaces (42) each extend in radial outward direction from a middle part (35) of the transverse segment (32) towards a respective side surface (37) thereof with a highest, most radially outward located peak of a respective the saddle surface (42) located at the 10 end of that saddle surface (42) on the side of the respective side surface (37). 1043881

Description

TRANSVERSE SEGMENT FOR A DRIVE BELT WITH A CARRIER RING AND

MULTIPLE TRANSVERSE SEGMENTS The present disclosure relates to a transverse segment for a metal drive belt for a continuously variable transmission for motor vehicles, as defined in the preamble of the claim 1 hereinafter.

Such a transverse segment and the drive belt incorporating it are well-known and are, for instance, described in the European patent applications EP-A-0 626 526. The known drive belt is composed of a plurality of steel transverse segments and two endless, i.e. ring-shaped carriers, each extending through a recess provided on either lateral side of the segments such that these segments are supported and guided by the carrier rings. The carrier rings are also made of steel and are each composed of a number of individual continuous bands that are narrowly fitted, one around the other. The transverse segments are neither fixed to one another nor to the carrier rings, such that they can move relative to the carrier rings at least along the circumference, i.e. the length thereof. In the drive belt, adjacent transverse segments abut one another through their respective front and back main surfaces, which main surfaces face, at least predominantly, in the said circumferential direction. The known drive belt is operated in a lubricated or oiled environment, both to reduce belt-internal friction losses and to cool the belt and the pulleys of the transmission.

The known transverse segment is provided with a friction surface on either lateral, i.e. axial side thereof. By means of these friction surfaces the transverse segment arrives in (frictional) contact with a driving pulley and a driven pulley of the transmission such that a rotation of the driving pulley can be transferred to the driven pulley via the likewise rotating drive belt. The known transverse segment is further provided with a stud on its front main surface and a hole on its back main surface. In the drive belt the stud of a first transverse segment is inserted in the hole of a second, adjacent transverse segment. As a result, the consecutive transverse segments in the drive belt mutually align each other in a plane that is oriented parallel with the said main surfaces thereof, i.e. perpendicular to the said circumferential direction.

During operation of the drive belt, a relative movement may exist between the transverse segments and the carrier rings the said circumferential direction thereof. Furthermore, the transverse segments that are forced radially outwards by the pulleys during operation are contained in that direction by the carrier rings. Thus a transverse segment arrives into contact with the carrier rings via the radial inner surfaces of the recesses thereof that contain the carrier rings. These latter surfaces are referred to in the art as the saddle surfaces of the transverse segments. An axial, i.e. width-wise shape or contour of the saddle surfaces is known to be shaped slightly convex to promote the preferred alignment of a respective carrier ring relative to (the axial width of) a respective saddle surface. In this latter respect it is known that the carrier ring is urged to centre itself on the peak, i.e. the most radially outward located, highest point of the saddle surface during operation, which phenomenon is also denoted carrier ring tracking. However, this peak of the saddle surface does not necessarily lie in the middle thereof. In particular, it is generally considered favourable to minimise a contact between the carrier rings and the transverse segments in the axial direction, in which case the peak of the saddle surfaces is located somewhat off-centre (relative to the geometric midpoint of the respective saddle surface) towards the respective axial side of the transverse segment, i.e. is located more towards the pulley than towards the said middle portion, as taught by EP-A-1 267 091 and EP-A-1 566 567.

Although the known drive belt design has been successfully applied in practice for many years now, recently a new type of failure was unexpectedly observed in a specific transmission application thereof. Although this new failure type is clearly related to the transmission development trend of increasing torque to be transmitted and a continually extending of the ratio coverage (defined as the quotient of a smallest and a largest speed ratios provided thereby), the underlying mechanism was not understood. In particular, breakage of one of the radially outermost continuous bands of the carrier ring occurred, whereas it is well-known that the radially innermost continuous band of the carrier ring receives the highest tension and bending stresses amongst all bands thereof during operation, According to an insight underlying the present invention, it must, however, also be taken into consideration that the driving pulley and the driven pulley of the transmission are generally offset relative to one another in their axial direction. In particular, such axial pulley offset varies between a first extreme value in a smallest speed ratio provided by the transmission, which smallest speed ratio is defined as the quotient of the rotation speed of the output pulley divided by the rotation speed of the input pulley, and second extreme value, when the said rotation speeds are equal, i.e. when the transmission provides a speed ratio equal to 1. In between these two extreme axial pulley offset values, a zero offset value occurs in two specific speed ratios of the transmission between speed ratio 1 and the said smallest speed ratio and a largest speed ratio of the transmission respectively. Only in these two specific speed ratios, the axial positions of the transverse segments at the two transmission pulleys coincide, such that each carrier ring can centre itself on the peak of the saddle surfaces at both pulleys. In other speed ratios the axial pulley offset causes that the axial position of the carrier rings relative to the transverse segments at both pulleys will only be partly determined by the said carrier ring tracking phenomenon. Moreover, the continuous bands of the carrier rings can slide relative to one another in the axial direction and are thus even less influenced by carrier ring tracking phenomenon.

Based on the observed breakage of a radially outer continuous band of the carrier rings together with the above considerations, it appears that specifically in the smallest speed ratio this radially outer continuous band still arrives in adverse contact with the said middle portion of the transverse segments, at least dynamically during operation of the transmission. To reduce the intensity and/or frequency of such dynamic contact, the present invention proposes avoid that the carrier ring is urged towards the middle portion of the transverse segment. In particular according to the present invention, the saddle surface is hereto provided with a convex curvature only between such middle portion of the transverse segment and the peak of the saddle surface, i.e. of the convex curvature thereof. Hereto, either such peak substantially coincides with, i.e. is located at or close to the respective axial side of the transverse segment, or the saddle surface extends in a straight line from such respective axial side to the convexly curved part thereof.

The novel transverse segment will now be elucidated further with reference to the attached drawing figures, whereof: Fig. 1 provides a schematic perspective view of the continuously variable transmission with a drive belt running over two pulleys, which drive belt includes an endless carrier and a number of transverse segments; Fig. 2 shows a cross section of the known drive belt, which cross-section is oriented in the circumference direction of the belt; Fig. 3 provides a width-wise oriented view of a transverse segment of the known drive belt; Fig. 4A provides a close-up of a detail of the known transverse segment, schematically illustrating a convexly curved saddle surface thereof; Fig. 4B is a schematic representation of the saddle surface contour similar to Fig. 4A, however, depicting a first embodiment of the saddle surface shaped in accordance with the present invention; and Fig. 4C is a schematic representation of the saddle surface contour similar to Fig. 4A and 4B, however, depicting a second embodiment of the saddle surface shaped in accordance with the present invention.

In the drawing figures equal reference signs indicate equal or similar structures and/or parts.

The schematic view of a continuously variable transmission in figure 1 shows a drive belt 3 that runs over two pulleys 1, 2 and that includes a flexible endless carrier, i.e.

carrier ring 31 and an essentially contiguous row of transverse segments 32 that are mounted on and arranged along the circumference of the carrier ring 31. In the illustrated configuration of the transmission, the upper pulley 1 will rotate more quickly than the lower pulley 2. By changing the distance between the two conical sheaves 4, 5 of the pulleys 1, 2, the so-called running radius R of the drive belt 3 on each pulley 1, 2 can be changed in a mutually coordinated manner and, as a result, the (transmission) ratio between the rotational speeds of the two pulleys 1, 2 can be varied.

In figure 2, the drive belt 3 is shown in a cross section thereof facing in the circumference or length direction L (see Fig. 3) of the belt 3, i.e. facing in a direction perpendicular to the axial or width direction W and the radial or height direction H thereof.

This figure 2 shows the presence of two carrier rings 31, shown in cross-section, that carry and guide the transverse segments 32 of the drive belt 3, whereof one transverse segment 32 is shown in front elevation.

The transverse segments 32 and the carrier rings 31 of the drive belt 3 are typically made of different metals, in particular steel alloys. The transverse segments 32 take-up a clamping force exerted between the sheaves 4, 5 of each pulley 1, 2 via respective side surfaces 37 thereof, one such side surface 37 being provided at either axial side of the transverse segment 32. These side surfaces 37 are mutually diverging in radial outward direction such that an acute angle is defined there between that is denoted the contact angle Oc of the drive belt 3, which contact angle essentially matches a V-angle defined between the two sheaves 4, 5 of each pulley 1, 2, which latter angle is denoted the pulley angle Oe.

The transverse segments 32 are able to move, i.e. to slide along the carrier rings 31 in the circumference direction L, so that a torque can be transmitted between the transmission pulleys 1, 2 by the transverse segments 32 pressing against one another and pushing each other forward along the carrier rings 31 in a direction of rotation of the drive belt 3 and the pulleys 1, 2. In the exemplary embodiment of this figure 2, the carrier rings 31 are composed of five individual endless bands each, which endless bands are mutually concentrically nested to form the carrier ring 31. In practice, the carrier rings 31 often comprise more than five endless bands, e.g. nine or twelve or possible even more.

The transverse segment 32 of the drive belt 3, which is also shown in a side elevation in figure 3, is provided with two cut-outs 33 located opposite one another, which cut-outs 33 each open towards a respective axial side of the transverse segment 32 and each accommodate (a small section of) a respective carrier ring 31. A first or base portion 34 of the transverse segment 32 thus extends radially inwards from the carrier rings 31, a second or middle portion 35 of the transverse segment 32 is situated in between the 5 carrier rings 31 and a third or top portion 36 of the transverse segment 32 extends radially outwards from the carrier rings 31. The radially inner side of each cut-out 33 is delimited by a so-called saddle surface 42 of the base portion 34 of the transverse segment 32, which saddle surface 42 faces radially outwards, generally in the direction of the top portion 36 of the transverse segment 32, and contacts the inside of an carrier ring 31. A first or rear surface 38 of the two main body surfaces 38, 39 of transverse segment 32 that face in mutually opposite circumference directions L, is essentially flat. The other or front main body surface 39 of the transverse segment 32 is provided with a so-called rocking edge 18 that forms, in the radial direction H, the transition between an upper part of the front surface 39, extending essentially in parallel with its rear surface 38, and a lower part thereof that is slanted such that it extends towards the rear surface 38. In figure 2 the rocking edge 18 is indicated only schematically by way of a single line, however, in practice the rocking edge 18 is mostly provided in the shape of a convexly curved transition surface. The said upper part of the transverse segment 32 is thus provided with an essentially constant dimension between the main body surfaces 38, 39, i.e. as seen in the circumference direction L, which dimension is typically referred to as the thickness of the transverse segment 32. It is noted that in order to realise a favourable contact between the transverse segments 32 and the carrier rings 31, in particular to promote the preferred alignment of a respective carrier ring 31 relative to the (width of) respective saddle surfaces 42 of the transverse segments 32, these saddle surfaces 42 are typically curved at least slightly convexly and at least in the axial direction. In this respect, it is known that during operation of the drive belt 3 the carrier rings 31 are urged to centre themselves on a most radially outward located, highest point, i.e. peak of the convexly curved saddle surfaces

42. The convexity of the saddle surfaces 42 that is applied in practice is, however, so small that it cannot be discerned on the scale of figure 2.

Figure 4A provides a schematically drawn enlargement of a detail of the transverse segment 32, including the saddle surface 42 thereof. Even at the scale of figure 4A, the radius of curvature Rs of the saddle surface 42 has been exaggerated by about 5 times to be able to illustrate this design feature. To give a numeric example: In a practical design of the drive belt 3, the saddle surface 42 may extend for about 10 mm in the width direction W and is convexly curved at a radius Rs of 200 mm or more. This means that the peak P1 of the saddle surface 42 lies about 62 micron above (i.e. radially outward from) a left side endpoint LE and/or a right side endpoint RE of the saddle surface 42. It is noted that in practice the saddle surface 42 is often shaped marginally elliptical rather than perfectly arc-shaped.

However, in most cases, the convex curvature of the saddle surface 42 can be approximated by a virtual circular arc with a high degree of accuracy. lt is further noted that the left and right side endpoints LE, RE of the saddle surface 42 correspond to locations were a local radius of curvature of the contour of the transverse segment 32 changes sharply between the relatively large radius of curvature Rs of the saddle surface 42 to a much smaller radius of curvature that defines the transition between the saddle surface 42 and the middle portion 35 of the transverse segment 32 or between the saddle surface 42 and a respective side surface 37 of the transverse segment 32. Typically, such change of the local radius of curvature at the endpoints LE, RE of the saddle surface 42 is by two orders of magnitude, for example from the said 200 mm radius Rs to a value close to 1 mm.

Thus, the saddle surface 42 of the transverse segment 32 is well-defined and the size and shape thereof, including the location of the said endpoints LE, RE thereof that are clearly defined.

In figure 4A the width wise contour of the saddle surface 42 is indicated by the solid line 42. The saddle surface 42 is convexly curved and extends symmetrically between the respective left side and right side endpoints LE, RE thereof, such that a geometric midpoint MP i.e. the middle of the saddle surface 42, also represents the peak P1 thereof.

With such a symmetric contour of the saddle surface 42, the carrier ring 31, which tends to centre itself on the peak P1 during operation of the drive belt 3, will thus be aligned with the said geometric midpoint MP.

Alternatively, the saddle surface is shaped according to an asymmetric contour that is also illustrated in figure 4A by the dashed line 42-A.

A peak P2 of this latter saddle surface 42-A is offset towards the right side of the geometric midpoint MP of the saddle surface 42-A, i.e. away from the middle portion 35 of the transverse segment 32 towards the respective lateral, i.e. axial side thereof, i.e. towards a respective side surface 37 of the transverse segment 32. In this case, the (self- )alignment of the carrier ring 31 that centres on the peak P2 of the saddle surface 42 is biased away from the middle portion 35 of the transverse segment 32 towards the respective side surface 37 thereof.

According to the present invention, the above known designs of the saddle surface 42, in particular of the said contour thereof, can be improved upon in order to favourably reduce a dynamic contact between the outer continuous bands of the carrier ring 31 during operation of the transmission.

This dynamic contact was found to occur specifically when the transmission load is high and the transmission speed ratio is smallest, in which conditions the said centring of the carrier ring 31 on the peak P1, P2 of the respective saddle surface 42, 42-A appears to be insufficient for preventing such dynamic contact.

A first embodiment of the saddle surface 42-B according to the present invention is illustrated in figure 4B. In this first embodiment of the invention, the peak P3 of the saddle surface contour coincides with the endpoint of the saddle surface 42-B on the side of the respective side surface 37, i.e. the right side endpoint RE in figure 4B. By applying this specific saddle surface contour, the carrier ring 31 is in principle not urged towards the middle portion 35 of the transverse segment 32 at all.

Preferably, in this first embodiment, a convex contour of the saddle surface 42-B is defined or at least approximated by a relatively large radius of curvature Rs in comparison with the known transverse segment 32, in particular a radius of at least 250 mm and preferably of 300 mm or more. In extremis, saddle surface 42 extends, at least partly, in a straight line that is angled slightly upward, i.e. radially outward in a direction away from the middle portion 35 of the transverse segment 32 towards a respective side surface 37 thereof. More in particular, the peak P3 of the saddle surface 42-B preferably lies no more than 100 micron and preferably between 25 micron and 75 micron radially outward from the endpoint of the saddle surface 42-B on the side of the middle portion 35 of the transverse segment 32, i.e. the left side endpoint LE in figure 4B. By these latter shape restrictions of the saddle shape contour, an asymmetric loading, i.e. tensioning of the carrier ring 31 during operation of the transmission is kept within the customary, functionally acceptable limits. Moreover, a force with which the carrier ring 31 is urged towards the respective side surface 37 of the transverse segment 32 is favorably limited : thereby, in particular in view of the absence of a counter force urging it towards the middle portion 35 of the transverse segment 32.

A second embodiment of the saddle surface 42-C according to the present invention is illustrated in figure 4C. In this second embodiment of the invention, the saddle surface 42-C includes both a convexly curved section on the side of the middle portion 35 of the transverse segment 32 and an axially oriented, straight section P4 on side of a respective side surface 37 of the transverse segment 32. Thus, the entire straight section P4 represents the peak, i.e. most radially outward located, highest point of the saddle surface 42-C. Also by applying this specific saddle surface contour, the carrier ring 31 31 is in principle not urged towards the middle portion 35 of the transverse segment 32 at all.

A transition point TP between the said convexly curved section and the straight section P4 of the saddle surface 42-C does not necessarily coincide with the geometric midpoint of the saddle surface 42-C, as illustrated in figure 4C. Rather, the (axial/

widthwise) location of the said transition point TP can be chosen to control the tendency of the carrier ring 31 to move towards the respective side surface 37 of the transverse segment 32. In fact, the said transition point TP is preferably located between the middle portion 35 of the transverse segment 32 and the geometric midpoint of the respective saddle surface 42-C. In this way, a force with which the carrier ring 31 is urged towards the respective side surface 37 of the transverse segment 32 is favorably limited, in particular in view of the absence of a counter force urging it towards the middle portion 35 of the transverse segment 32. For the same reason, the said convexly curved section of the saddle surface 42-C is preferably defined or at least approximated by a relatively large radius of curvature Rs in comparison with the known transverse segment 32, in particular a radius of at least 250 mm and preferably of 300 mm or more. More in particular, the peak P4 of the saddle surface 42-C preferably lies no more than 100 micron and preferably between 25 micron and 75 micron radially outward from the endpoint of the saddle surface 42-C on the side of the middle portion 35 of the transverse segment 32, i.e. the left side endpoint LE in figure 4C.

The present disclosure, in addition to the entirety of the preceding description and all details of the accompanying figures, also concerns and includes all the features of the appended set of claims. Bracketed references in the claims do not limit the scope thereof, but are provided as non-binding examples of the respective features. The claimed features can be applied separately in a given product or a given process, as the case may be, but it is also possible to apply any combination of two or more of such features therein.

The invention(s) represented by the present disclosure is (are) not limited to the embodiments and/or the examples that are explicitly mentioned herein, but also encompasses amendments, modifications and practical applications thereof that lie within reach of the person skilled in the relevant art.

Claims (7)

CONCLUSIESCONCLUSIONS 1. Een dwarssegment (32) gemaakt van staal en bestemd voor een metalen drijfriem (3) voor een continu variabele overbrenging, welke drijfriem (3) tenminste twee draagringen (31) en een aantal, althans in onderlinge samenhang, verschuifbaar op de draagringen (31) aangebrachte van dergelijke dwarssegmenten (32) omvat, in welk dwarssegment (32) tenminste twee uitsparingen (33) zijn voorzien voor het opnemen van telkens één van de draagringen (31), welke uitsparingen (33) zich tussen een voorvlak (39) en een achtervlak (38) van het dwarssegment (32) over de dikte daarvan uitstrekken en in één richting, te weten in de drijfriem (3) radiaal naar binnen, worden begrensd door twee, radiaal naar buiten georiënteerde zadelvlakken (42) van het dwarssegment (32), die de binnenzijden van de draagringen (31) ondersteunen en die zich ieder in breedterichting tussen een middendeel (35) van het dwarssegment (32) en een respectievelijk zijvlak (37) daarvan uitstrekken, met het kenmerk, dat de zadelvlakken (42) zich ieder tevens in radiale richting naar buiten uitstrekken, waarbij een in die radiale richting meest naar buiten gelegen deel van de zadelvlakken (42) althans nagenoeg samenvalt met een uiterste punt daarvan aan de zijde van het respectievelijk zijvlak (37) van het dwarssegment (32).1. A transverse segment (32) made of steel and intended for a metal drive belt (3) for a continuously variable transmission, which drive belt (3) has at least two support rings (31) and a number of them, at least in mutual relationship, slidable on the support rings ( 31) comprises such transverse segments (32), in which transverse segment (32) at least two recesses (33) are provided for receiving in each case one of the support rings (31), which recesses (33) are located between a front surface (39) and a rear surface (38) of the transverse segment (32) extending over its thickness and bounded in one direction, i.e. radially inwardly in the drive belt (3), by two radially outwardly oriented saddle surfaces (42) of the transverse segment (32), which support the inner sides of the support rings (31) and which each extend in width direction between a central part (35) of the transverse segment (32) and a respective side surface (37) thereof, characterized in that the saddle surfaces and (42) each also extend outwardly in a radial direction, wherein a part of the saddle surfaces (42) located most outwardly in that radial direction at least substantially coincides with an extreme point thereof on the side of the respective side surface (37) of the transverse segment (32). 2. Het dwarssegment (32) volgens de conclusie 1, met het kenmerk, dat de zadelvlakken (42) ieder van een vlakke contour zijn voorzien.The transverse segment (32) according to claim 1, characterized in that the saddle surfaces (42) are each provided with a flat contour. 3. Het dwarssegment (32) volgens de conclusie 1, met het kenmerk, dat de zadelvlakken (42) ieder van een convex gekromde contour zijn voorzien.The transverse segment (32) according to claim 1, characterized in that the saddle surfaces (42) each have a convex curved contour. 4. Het dwarssegment (32) volgens de conclusie 1, met het kenmerk, dat de zadelvlakken (42) ieder zowel een eerste deel aan de zijde van het middendeel (35) van het dwarssegment (32) met een convex gekromde contour, als een tweede deel aan de zijde van het respectievelijk zijvlak (37) van het dwarssegment (32) met een vlakke contour omvatten.The transverse segment (32) according to claim 1, characterized in that the saddle surfaces (42) each have a first part on the side of the middle part (35) of the transverse segment (32) with a convex curved contour, and a second part on the side of the respective side face (37) of the transverse segment (32) with a flat contour. 5. Het dwarssegment (32) volgens de conclusie 4, met het kenmerk, dat het genoemde tweede deel van de zadelvlakken (42) met de vlakke contour zich enkel in de breedterichting en niet in de radiale richting uitstrekt.The transverse segment (32) according to claim 4, characterized in that said second part of the saddle surfaces (42) with the flat contour extends only in the width direction and not in the radial direction. 6. Het dwarssegment (32) volgens de conclusie 4 of 5, met het kenmerk, dat het genoemde tweede deel van de zadelvlakken (42) met de vlakke contour zich over meer dan de helft van een breedteafmeting van de zadelvlakken (42) uitstrekt.The transverse segment (32) according to claim 4 or 5, characterized in that said second portion of the flat contour saddle surfaces (42) extends over more than half of a width dimension of the saddle surfaces (42). 7. Het dwarssegment (32) volgens de een voorgaande conclusie, met het kenmerk, dat de zadelvlakken (42) zich ten hoogste over 75 micron en bij voorkeur tussen de 25 en 50 micron in radiale richting uitstrekken.The transverse segment (32) according to any preceding claim, characterized in that the saddle surfaces (42) extend at most over 75 microns and preferably between 25 and 50 microns in radial direction.