Transverse element for a drive belt

Abstract: Transverse element for a drive belt of the kind in which transverse elements whose principal planes rest against eachother are fitted displaceably on one or more supports. The transverse elements (5) are provided with one or more supporting surfaces (10) for the support(s) (14), the supporting surface (10) being profiled at least in the direction transverse to the principal planes of the transverse element (5). The supporting surface (10) is profiled in such a manner that a resultant force, which is to be exerted by a support (4) on the transverse element (5), essentially engages outside the centre of the supporting surface (10) delimited by the principal planes. Stable positioning of the transverse element (5) in the pulleys (1,2) is thereby obtained, slipping and wear are reduced and efficiency increased.

Description: The invention relates to a transverse element for a drive belt as defined by the features of the preamble of claim 1. Such a transverse element for a drive belt is disclosed in GB Patent 2,013,116. The drive belt is used, in particular, in a continuously variable transmission in which the drive belt is used as the transmission means between the pulleys thereof. A drawback of said known transverse element is that, when it is clamped between the pulleys, it tilts slightly, which leads to slipping and consequently the efficiency of the transmission decreases and the wear increases. The object of the invention is to provide a transverse element which remains more stably positioned when it is clamped between the pulleys and is less inclined to tilt. The transverse element according to the invention is defined by the features of claim 1. As a result of this, an improved distribution of forces on the transverse element is achieved when the transverse element is clamped between the pulleys, said transverse element remaining more stably positioned and being less inclined to tilt. Slipping of the transverse element in the pulleys is reduced and the efficiency of the transmission increases. Furthermore, the wear of the transverse element and the pulleys decreases. This measure may optionally be implemented for both operating directions of the drive belt. According to a more specific development of the invention, the supporting surface is profiled in such a manner that the resultant force in the main operating direction of the transverse element engages before the centre. In practice, the continuously variable transmission together with the drive belt incorporated therein will be operated more frequently in the forward direction and less frequently in the reverse direction. In this connection, the use of the continuously variable transmission in vehicles, such as cars, may be mentioned. By allowing the resultant force in the main operating direction of the transverse element to engage before the centre of the supporting surface, a more stable positioning of the transverse element is obtained for the main operating direction of the drive belt. According to further embodiments of the invention, the profile may be curved, convex, concave, bevelled or stepped. According to a more specific development.of the invention, the top of the supporting surface is fitted outside the centre of the supporting surface delimited by the principal planes, in particular at the boundary of the supporting surface and a principal plane of the transverse element. The top may furthermore be flattened. Such profiles and an eccentric top are easy to apply from the point of view of machining and can often be combined with other necessary operations so that the improved transverse element according to the invention can be produced without appreciable further costs. The invention will be explained with reference to a drawing. In this drawing: Fig. 1 shows a diagrammatic side view of a continuously variable transmission; Fig. 2 (a) shows a front view of a transverse element according to the state of the art; Fig. 2 (b) shows a side view of a transverse element according to the state of the art, in cross section, together with, partly shown, corresponding transverse elements; Fig. 3 (a) shows a side view of a transverse element according to the invention, in cross section, having a convex profile and an eccentric top; Fig. 3 (b) shows an element according to (a), in which the top is flattened; Fig. 3 (c) shows an element according to (a), in which the top is fitted at the boundary with the principal plane; Fig 4 (a) shows a side view of a transverse element, in cross section, having a partly bevelled supporting surface and a flat top; Fig 4 (b) shows an element according to (a), having a completely bevelled supporting surface; Fig 4 (c) shows an element according to (a), having two bevelled parts in the supporting surface; Fig. 5 (a) shows a side view of a transverse element, in cross section, having a stepped profile; Fig. 5 (b) shows an element according to (a), having a bevelled connecting piece; Fig. 5 (c) shows an element according to (a), having a convex step. The continuously variable transmission shown in Figure 1 comprises two pulleys 1, 2 on which a drive belt 3 has been put. In this case, the drive belt comprises two supports 4 on which transverse elements 5 have been fitted displaceably. Incidentally, within the framework of the invention, drive belts having one or more than two supports can be used without problem. The principal planes 8a, 8b of the transverse elements 5 (Figures 2a, 2b) bear against each other. Principal plane 8a is bevelled in a plane 6 at the radial inside of the drive belt 3 at a tilt zone 7. The transverse elements are provided with two recesses 9 for receiving the supports 4. The recesses 9 are partly delimited by the supporting surface 10 for the supports 4. In this case, the supporting surface is profiled convexly between the principal planes 8a, 8b (see Figure 2b) and the top of the convexly profiled supporting surface 10 is in the centre between the principal planes 8a, 8b. The transverse element is furthermore provided with two conical flanks 11 for clamping between the pulleys. The transverse elements 5 experience a forward force (Fv) at the conical flanks 11, in particular in the driving pulley 1. Because, in this case, the transverse elements 5 shift over the support 4, a reaction force (Fb), which is directed backwards, occurs at the supporting surface. When positioned in the pulley, the transverse elements 5, 5' bear against each other, in particular at the tilt zone 7. The forward-directed force (Fv) on the conical planes and the backward-directed force (Fb) on the supporting surface produce a moment on the transverse element 5, the centre (C) of which is approximately at the tilt zone 7 in the centre between the principal planes. As a result of said moment, the transverse element 5 will tilt slightly backwards and slip between the pulleys causing loss of efficiency and wear. It has been recognised that, in the transverse element according to the invention, said moment can be counteracted by having the force (Fr) exerted by the support 4 on the supporting surface 10, in the radial direction of the drive belt, no longer running through the centre (C), but engaging outside the centre of the supporting surface. This is shown in Figure 3a, in which the top 12 of the convex supporting surface 10 is shifted slightly in the forward direction. The resultant force Fr which is exerted by a support 4, which is to be received in the recess, on the supporting surface, thus acts in a direction which is opposite to the moment exerted by the forces Fv, Fb. Tilting of the transverse element 5 is thereby prevented and no slipping or excessive wear will occur. Incidentally, this effect can already be achieved by shifting the point of application of the force Fr and/or the top off centre by more or less than one tenth of a millimetre. Incidentally, in those instances where the forces Fv, Fr, Fb are mentioned, this refers to the resultant of the force of the pulley, which engages in a diffused manner, on the conical flank or the support of the supporting surface, respectively. In the embodiment according to Figure 3b, the top 13 is also slightly moved forwards but also flattened. Figure 3c shows an embodiment in which the top 14 is fitted at the boundary with the principal plane 8a. In the embodiment according to Figure 4, the supporting surface 10 is at least partly profiled in a bevelled manner. In Figure 4a, the bevelled plane 18 runs into the essentially flat top plane 15. In Figure 4b, the entire supporting surface 10 is profiled in a bevelled manner and the top 16 is at the boundary with the principal plane 8a. In Figure 4c, the flat top plane 17 runs into two bevelled planes 19, 20. In Figure 5, the supporting surface is designed as a stepped plane. In Figure 5a, this consists of two planes 21 and 22, whereas, in Figure 5b, the two planes 23 and 24 are connected by a bevelled plane 25. Finally, Figure 5c shows an embodiment having a plane 26 and a convex plane 27. It will be obvious that the invention is not limited to the embodiments shown but that various alternatives are conceivable within the scope of the invention. Thus, the measures according to the invention can be applied at the same time for moving the drive belt both in the forward and the backward direction. In most cases, however, the application of measures only for the main operating direction, i.e. the forward direction, may be sufficient. Also, the transverse elements do not necessarily have to be designed with so-called stud/recess means for their mutual coupling.

Claims: Transverse elements (5) for a drive belt of the kind in which the transverse elements whose principal planes (8a, 8b) rest against each other are fitted displaceably on one support (4) or more supports (4, 4) and are provided with one supporting surface (10) or more supporting surfaces (10, 10) for the support(s), which supporting surface(s) is(are) profiled at least in the direction transverse to the principal planes of the transverse element and has(have) a centre, which centre is defined by equal distances from the principal planes, characterised in that the supporting surface(s) is(are) profiled in such a manner that a resultant force, which is to be exerted by the support(s) on the transverse element, essentially engages outside the centre of the supporting surface. Transverse element according to Claim 1, characterised in that the supporting surface is profiled in such a manner that the resultant force in the main operating direction of the transverse element engages before the centre. Transverse element according to Claim 1 or 2, characterised in that the supporting surface is curved. Transverse element according to Claim 3, characterised in that the supporting surface is at least partly convex. Transverse element according to Claim 3, characterised in that the supporting surface is at least partly concave. Transverse element according to Claim 1 or 2, characterised in that the supporting surface comprises at least a bevelled part. Transverse element according to Claim 1 or 2, characterised in that the supporting surface is at least partly stepped. Transverse element according to Claims 2 - 7, characterised in that the top of the supporting surface is fitted outside the centre of the supporting surface delimited by the principal planes. Transverse element according to Claims 4 and 8, characterised in that the top of the convexly curved supporting surface, in the main operating direction of the transverse element, is fitted before the centre of the supporting surface. Transverse element according to Claim 8 or 9, characterised in that the top is positioned at the boundary of the supporting surface and a principal plane of the transverse element. Transverse element according to one of the preceding Claims 8 -10, characterised in that the top is flattened. Drive belt provided with transverse elements according to one of the preceding claims.

Inventors: SMEETS PAUL MARIA, SMEETS, PAUL MARIA
Applicants: DOORNES TRANSMISSIE BV, VAN DOORNE'S TRANSMISSIE B.V.
Application year: 1993
Main classification: F16G5
IPC codes: F16G5