DRIVING BELT, ELEMENT FOR SUCH DRIVING BELT AS WELL AS A METHOD FOR PRODUCING SUCH ELEMENT

Abstract: Transverse elements (6), suitable for being used in V-shaped pulleys (1, 2) of a continuously variable trans­ mission, are provided with endless carriers (7), which due to a transmission ratio dependent misalignment of the pulleys (1 2), contact the lateral boundary face (16) of the element (6), under circumstances, which causes an excessive wear and shortens the life of the transmission belt with such elements (8). A solution is being provided to result in elements (8) whose boundary faces (16) are at least partly rounded in the longitudinal direction of the element (8), which can be realised by a sanding operation.

Description: The invention relates to a transverse element to be used for a driving belt, suitable for being used on V-shaped pulleys of a continuously variable transmission, said driving belt being provided with one or more endless carriers on which the transverse elements are movably provided, whereby the transverse elements are provided with one or more recesses for accommodating the carriers, and whereby each recess is bounded by at least one abutting face for butting against the inner side of the carrier, as well as by at least one boundary face for laterally retaining the carrier. Such a transverse element is known from US-A- 4,080,841, whereby the abutting face for butting against the inner side of the carrier is convexly curved, as a result of which it is to a large extent prevented that the carrier laterally touches the element, and wear, casu quo damage due to said touching is considerably reduced and the life of the driving belt is extended. It has become apparent that indeed the contact between the carrier and the transverse element is considerably reduced, but such a contact cannot be prevented at all times. This is especially caused by the geometry of the continuously variable transmission in which the driving belt is used. The pulleys of such a continuously variable transmission are namely aligned for only a limited number of transmission ratios, as is described in detail in NL-A- 8701134. As a result the driving belt often runs out of alignment between the pulleys. The result of this is a lateral movement of the transverse elements when the transverse elements move into the pulleys, which movement is not completely followed by the carrier at once, as a result of which in some extreme cases contact between the transverse elements and the carrier is possible. Said contact is undesired and results in a non-optimal life of the driving belt. The object of the invention is to limit, casu quo overcome the drawbacks of the known transverse elements. In order to accomplish that objective the transverse element of the kind described above is according to the invention characterized in that the lateral boundary face is at least partly rounded in the longitudinal direction of the transverse element. As a result of this measure the transverse elements and the carrier can no longer touch one another in a number of cases, whilst in those cases where there is still contact the nature and the intensity of the contact has been reduced to such an extent that excessive wear or damage cannot occur, as a result of which the life of the driving belt has been considerably improved. The invention will be further explained hereafter, with reference to an embodiment and a drawing. In the drawing: Fig 1 is a diagrammatic illustration of a driving belt around the pulleys of a continuously variable transmission; Fig 2 is an embodiment of a transverse element; Fig 3 is a second embodiment of a transverse element; Fig 4 is a plan view, partly in section, of the driving belt and the pulleys according to Figure 1; Fig 5a shows a method according to the invention, and Fig 5b shows another method according to the invention. Figure 1 illustrates two pulleys 1, 2 of a continuously variable transmission. The pulleys 1, 2 are mounted on the shafts 4 and 5 respectively. Around the pulleys 1, 2 there is provided a driving belt 3. The driving belt 3 comprises a large number of transverse elements 6 which are movably provided on one (Fig 2) or more (Fig 3) carriers 7. The carrier 7 may comprise a single band but may also consist of one or more band packs. The transverse elements 6 are slightly conical towards the inside, by means of the flanks 8, for co-operation with the conical discs of the pulleys 1, 2. Fig 2 illustrates a transverse element 6 for use with a single carrier 7, which carrier 7 may be built up of one or more endless bands. The transverse element 6 thereby comprises a recess 13 with an abutting face 9 for butting against the inner side of the carrier 7. The carrier 7 is furthermore laterally retained by the boundary faces 11 and 12, respectively, whilst the carrier 7 is retained at its upper side by a retaining pin 10. Fig 3 illustrates a transverse element 6 for use with two carriers 7, 7′, which may be accommodated in the recesses 14, 14′. The recesses 14, 14′ are again provided with an abutting face for butting against the inner side of the carriers 7, casu quo 7′. The carrier is retained at its upper side by a cross piece 15. The recess 14 is open at the longitudinal side of the transverse element 6 and is bounded at the opposite side by a boundary face 16. The convexly curved faces 9 have a centring effect on the carriers 7 butting against said faces, as a result of which the carriers will constantly attempt to position themselves above the uppermost point of the convexly formed face 9, and contact with the boundary faces 11, 12 and 16, respectively, is largely prevented. As has become apparent, however, contact is still possible in a number of extreme cases. As is illustrated in Fig 4 this is especially caused by the specific geometry of the continuously variable transmission, whereby the two pulleys are only aligned for a limited number of transmission ratios, and the driving belt often runs out of alignment between the pulleys, therefore. Where the driving belt now enters the pullzy, at the location of pulley 2 in Fig 4 for example, this results in a certain lateral movement of the transverse elements 6 (illustrated with an arrow to the left in detail A which is not completely followed by the carrier 7 at once. The carrier 7 usually does not touch the boundary faces 16 of the transverse elements 6 hereby, in a number of cases, however, contact appears to be unavoidable. In order to reduce the nature and the intensity of said contact between the carrier and the boundary faces 16, and in order to even prevent any contact as yet in a number of cases, the boundary faces 16 are slightly rounded, as is illustrated in Fig 4. Preferably at least the vertical edges oi the boundary faces 16 are rounded, preventing said edges from cutting into the carrier and therewith also preventing damage and wear. A suitable radius of curvature may thereby be selected to be larger,than or equal to 0.2 mm. Between the rounded edges the remaining part of the boundary face 16 may be straight but also curved. The boundary face 16 may also be completely convex, whereby the radius of curvature is preferably larger than or equal to half the thickness of the transverse element 6 , said thickness seen in the longitudinal direction of the driving belt. The intended rounding of the boundary face 16 of the transverse element 6 may be provided in a simple manner, e.g. by drawing the transverse element 6 with the boundary faces 16 (Fig 5a), by means of a tilting movement, along a sanding means, such as a sand ribbon 17. For that purpose one or more transverse elements 6 may be placed e.g. in a slot 19 of a rotating disc 18, whereby the transverse elements 6 are drawn, one by one, with their boundary face 16 along the sand ribbon 17. It will be apparent that e.g. instead of the transverse element also the sanding means, casu quo the ribbon, may be drawn tilted, whether or not through an angle, along the transverse element 6. An alternative method for rounding the boundary faces 16 may be found by upsetting the boundary faces 16 by means of a press tool 20 (Fig 5b). Apart from that this operation can very well be combined with other manners of forming the transverse elements 6, such as die-cutting or progressive die-cutting.

Claims: 1. Transverse element (6) to be used for a driving belt, suitable for being used on V-shaped pulleys of a continuously variable transmission, said driving belt (3) being provided with one or more endless carriers (7,7′) on which the transverse elements (6) are movably provided, whereby the transverse elements (6) are provided with one or more recesses (13;14,14′) for accommodating the carriers (7,7′), and whereby each recess (13;14,14′)is bounded by at least one abutting face (9) for butting against the inner side of the carrier (7,7′), as well as by at least one boundary face (11,12;16) for laterally retaining the carrier (7,7′), characterized in that the lateral boundary face (11,12;16) is at least partly rounded in the longitudinal direction of the transverse element (6). 2. Transverse element (6) according to claim 1, characterized in that at least one of the vertical edges of the lateral boundary face (11,12;16) is rounded. 3. Transverse element (6) according to claim 2, characterized in that the vertical edge is rounded, with a radius larger than or equal to 0.2 mm. 4. Transverse element (6) according to claim 2 or 3, characterized in that the part of the lateral boundary face (11,12;16) located between the edges is flat. 5. Transverse element (6) according to claim 2 or 3, characterized in that the part of the boundary face (11,12;16) located between the edges is convex. 6. Transverse element (6) according to any one of the claims 1 - 5, characterized in that the lateral boundary face is (11,12;16) convex. 7. Transverse element (6) according to claim 6, characterized in that the lateral boundary face (11,12;16) is convex, with a radius of curvature which is larger than or equal to half the thickness of the element (6). 8. Driving belt provided with a transverse element (6) according to any one of the preceding claims. 9. Method for producing a transverse element (6) according to any one of the claims 1 -7, characterized in that the at least partial rounding of the lateral boundary face (11,12;16) is provided by means of a sanding operation. 10. Method according to claim 9, characterized in that the lateral boundary face (11,12;16) is moved along means for the sanding operation by means of a tilting movement. 11. Method according to claim 8, characterized in that the element (6) is positioned in a rotating disc (18), and is moved with the boundary face (11,12;16) along the sanding means by the disc (18). 12. Method according to claim 10 or 11, characterized in that the sanding means comprise a sand ribbon (17). 13. Method for producing a transverse element (6) according to any one of the claims 1 - 7, characterized in that the at least partial rounding of the boundary face (11,12;16) is provided by means of an upsetting operation.

Inventors: VAN LITH, JOHANNES HENDRIKUS
Applicants: VAN DOORNE'S TRANSMISSIE B.V.
Application year: 1989
Main classification: F16G5
IPC codes: F16G5