The present invention relates to a drive belt according to the preamble of claim 1.

A drive belt as described above is generally used for the transmission of driving power between two shafts in a drive line. The drive belt is passed around a pair of pulleys, each pulley being provided on a different shaft. By frictional contact between a first pulley and the drive belt, a rotational motion of the first pulley is transformed into a translational motion of drive belt. By frictional contact between the drive belt and a second pulley, the translational motion of the drive belt is in turn transformed into a rotational motion of the second pulley. The second pulley is thus driven by the first pulley via the drive belt.

" A generally known use of a drive belt as described above is in the

continuously variable transmission of a two-wheeled vehicle such as a scooter. In such a transmission, each pulley comprises a pair of pulley sheaves, each sheave having an inclined, inward facing flank for contacting a side surface of the drive belt. Depending on the distance of the two sheaves with respect to each other, the drive belt runs along a pulley at a larger or a smaller diameter. By varying the distance of the pulley sheaves in a driving pulley or in a driven pulley, the transmission ratio between the two pulleys can, subject to certain limitations, be freely chosen.

Generally, in scooters, a drive belt is applied having a tension element comprising an elastomeric or rubber ring, the ring having embedded therein a number of tension fibers. Mounted on the ring are a number of support elements for supporting the tension element on a pair of pulleys, each support element having a pair of contact surfaces for sustaining frictional contact with a pair of pulley sheaves. Each support element is positioned inside a notch provided in the outer surface of the rubber ring, each support element thereby being fixed with respect to the ring in the longitudinal direction of the drive belt.

A drive belt as described in the previous paragraph is disclosed in JP- 2006207793. The known drive belt runs dry and is loaded by pulling. A pull belt is able to bridge a relatively large distance between two drive shafts. As compared to a push belt, the energy-efficiency of a pull belt, however, is relatively low. An objective of the present invention is to provide a cost-efficient, dry-running pull-belt for use with a continuously variable transmission, the pull belt having an improved energy-efficiency.

The above objective is attained by a drive belt according to claim 1 .

In a drive belt according to the invention, a tension element comprising a wire is directly glued, by means of an adhesive, to a support element. As a result, the drive belt lacks an elastomeric or rubber carrier like the one present in the known drive belt. A carrier like in the known drive belt is an element of substantial volume, which during running of the drive belt continuously needs to be deformed, and which thus forms a significant source of energy loss. In a drive belt according to the invention, energy loss due to deformation of the tension element during running of the drive belt hence is significantly reduced as compared to the known drive belt. A drive belt according to the invention therefore exhibits an improved energy-efficiency. This will in turn also improve the energy-efficiency of a vehicle comprising the belt. Furthermore, the cost-efficiency of the belt is improved by reduced material costs.

With a support element having an attachment surface in contact with the adhesive, the attachment surface may be provided with a relief in order to increase the area of attachment between a support element and the wire.

A relief may comprise a number of recesses extending in the circumferential direction of the drive belt. Thus, there will be a relatively large area of attachment between the support element and the wire.

A recess may cover the whole of the attachment surface in the circumferential direction. Thereby, an area of attachment between the support element and the wire is increased to a maximal extent without the wire having to bend. This facilitates the use of a wire that is relatively stiff.

The number of windings may be smaller than the number of recesses.

Thereby, it is possible for a wire to cover multiple recesses, the area of attachment between a support element and the wire being relatively large. In a preferred embodiment, the number of windings is smaller than the number of recesses by a ratio of less than 0.5, preferably a ratio in the range 0.2-0.4.

In a preferred embodiment, the attachment surface comprises two adjacent recesses separated by a protrusion, the protrusion having a prismatic shape. Thus, the size of the contact surface and the adhesive force that can be obtained between the wire and a support element may be significantly increased.

Preferably, a prismatic protrusion has a top angle of at most 80 degrees, more preferably 30 to 60 degrees.

A prismatic protrusion preferably has a base width of 0.3 to 3 mm, more preferably 0.5 to 0.8 mm. The attachment surface may comprise a first protrusion and a second protrusion, said protrusions each comprising a top, a diameter of the wire being at least equal to a distance between the two tops. The wire can thereby cover multiple tops, thus strengthening the degree of fixture between the wire and a support element. Preferably, said diameter is larger than said distance, so that the whole of a top can press into the wire.

An attachment surface may comprise a first portion and a second portion, the second portion facing the first portion with a wire positioned in between, the wire being attached to each of the first portion and the second portion. The adhesive force per support element can thereby be doubled.

With the first portion of the attachment surface comprising a recess, the second surface portion may comprise a protrusion facing said recess. A wire can then be pushed by the protrusion into the recess, thereby increasing the area of attachment between a support element and the wire.

The windings may be provided in a single layer or in multiple layers. A drive belt comprising a wire having windings in multiple layers is significantly stronger. Also, a weakening effect of any loose ends of a wire on the tension element as a whole is reduced.

The present invention further relates to a method for manufacturing a drive belt according to the invention. These and other aspects, features and advantages of the present invention will be further explained by the following description of one or more preferred embodiments with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which:

Figure 1 schematically shows in perspective view a drive belt mounted on a pair of pulleys of a continuously variable transmission;

Figure 2 schematically shows in perspective view a portion of a drive belt according to the state of the art;

Figure 3 schematically shows in perspective view a portion of a drive belt according to the invention;

Figure 4 schematically shows in perspective view a bottom piece and a top piece of a support element of a drive belt according to the invention;

Figure 5 schematically shows in perspective view a support element of a drive belt according to the invention;

Figure 6 schematically shows a transverse cross section through a drive belt according to the invention;

Figure 7 schematically shows in perspective view a mounting device to be used in the manufacturing of a drive belt according to the invention;

Figure 8 schematically shows in perspective view part of the mounting device of Figure 7, having mounted thereon a number of bottom piece of support elements of a drive belt according to the invention;

Figure 9 schematically shows in perspective view a bottom piece of a support element according to the invention, a number of portions of wire being arranged on the bottom piece.

Figure 1 shows a continuously variably transmission 2 comprising a first pulley 100a and a second pulley 100b. Each pulley 100a, 100b is mounted on a drive shaft 200a, 200b. Running on the two pulleys 100a, 100b is a drive belt 1 .

Each pulley 100a, 100b comprises a pair of pulley sheaves 101 a, 101 b. Each pulley sheave 101 a, 101 b has an inclined contact surface 102 facing the contact surface 102 of the other pulley sheave 101 a, 101 b. Within each pulley 100a, 100b, the pulley sheaves 101 a, 101 b are moveable with respect to each other in the axial direction of the respective drive shaft 200a, 200b so that the distance between the contact surfaces 102 of the two pulley sheaves 101 a, 101 b can be varied.

With the contact surfaces 102 of the two pulley sheaves 101 a, 101 b deviating with respect to each other in the radially outward direction of a pulley 100a, 100b, bringing the two pulley sheaves 101 a, 101 b closer together urges the drive belt 1 to move radially outward to continue running at a larger diameter. Vice versa, moving the two pulley sheaves 101 a, 101 b away from each other allows the drive belt 1 to move radially inward to continue running at a smaller diameter.

The drive belt 1 is an elongated, endless and therefore substantially ring- shaped member, which is passed around both of the drive shafts 200a, 200b. On each pulley 100a, 100b, the drive belt 1 is contained in between the two pulley sheaves 101 a, 101 b. The drive belt 1 comprises at the sides facing in the axial direction of the drive shafts 200a, 200b a pair of contact surfaces for sustaining frictional contact with each of the pulleys 100a, 100b, each contact surface of the drive belt 1 being in contact with a contact surface 102 of a pulley sheave 101 a, 101 b.

With the first pulley 100a being a driving pulley, the second pulley 100b is driven by the first pulley 100a via the drive belt 1 . The transmission ratio between the first pulley 100a and the second pulley 100b can be varied by changing the radius at which the drive belt 1 runs at each of the pulleys 100a, 100b.

In the following, the tangential direction of the ring shape of a drive belt will also be referred to as the circumferential direction of the drive belt. The axial direction of a drive shaft, being also the axial direction of the ring shape, will also be referred to as the axial direction. The radial direction with respect to the ring shape will also be referred to as the radial direction. Said circumferential direction, axial direction and radial direction will not only be used in relation to a drive belt as a whole, but also in relation to a tension element or a support element as separate pieces.

Figure 2 shows a drive belt 300 according to the state of the art. The drive belt 300 comprises a tension element 301 , 302 comprising an elastomeric or rubber ring- shaped carrier 301 . The carrier 301 has embedded therein a number of tension fibers 302 extending in the circumferential direction. Mounted on the carrier 301 are a number of support elements 303 made out of a plastics material.

Each support element 303 is substantially plate-shaped, and is arranged facing in the circumferential direction of the drive belt 300. At the sides facing in the opposite axial directions, a support element 303 comprises a contact surface 304a, 304b for coming into contact with the contact surface of a pulley sheave. The two contact surfaces 304a, 304b have an inclined position with respect to each other so as for the two contact surfaces 304a, 304b to fit the inclined contact surfaces of a pair of pulley sheaves. In its centre, the support element 303 comprises a slit 305 allowing the carrier 301 to extend through the support element 303.

At its radially outward and inward facing surfaces, the carrier 301 is provided with a sequence of transversely oriented notches 306. Adjacent notches are separated by a ridge 307a, 307b of carrier material. Each support element 303 extends into a notch 306, such that the support element 303 is fixed with respect to the tension element 301 , 302 in the circumferential direction of the drive belt 300 by a pair of ridges 307a, 307b neighbouring said notch 306.

It is noted that a support element 303 in the known drive belt is formed as an integral piece which has been injection moulded at the location of a notch 306, which piece is attached to the carrier 301 solely by means of form closure between the pair of ridges 307a, 307b neighbouring the notch 306 and said piece.

Figure 3 shows a drive belt 1 according to the invention. The drive belt 1 comprises a number of support elements 50, each support element 50 comprising a bottom piece 20 and a top piece 30 which have been assembled together to form the whole of a support element 50, leaving a slit 55 in the centre of the support element 50. The drive belt 1 comprises a tension element 10 extending through the slit 55 of each support element 50. The drive belt 1 further comprises an adhesive 60 provided in the slit 55 of each support element 50, the adhesive 60 connecting each support element 50 to the tension element 0.

The tension element 10 comprises a wire 40 having a number of windings 41 extending in the circumferential direction of the drive belt 1 . In Figure 3, only a portion of each winding 41 is shown. The windings 41 as a whole each extend along the full circumference of the drive belt 1 , wherein an end of a first winding 41 a neighbouring a second winding 41 b is connected to an end of that second winding 41 b. The different portions of the windings 41 shown in Figure 3 may be connected to each other so as to form a single wire 40, or form part of multiple wires. All windings 41 passing through the slit 55 of a support element 50 are positioned side by side such as to substantially fill the whole width of the slit 55. A winding 41 passing through a support element 50 is connected to that support element 50 through the adhesive 60 provided in the slit 55.

The adhesive 60 is schematically depicted in Figure 3 as filling the whole of the space of the slit 55 left available by the windings 41 . It is noted that within the scope of the invention, the adhesive 60 however not necessarily fills the whole of said space. Furthermore, it is also possible that part of the fixation of a support element 50 with respect to the tension element 10 results from friction between a winding 41 and the support element 50, rather than through an adhesive 60.

Figure 3 shows only a single layer of windings 41 . Within the scope of the invention, the tension element 10 may also comprise multiple layers, wherein each layer extends at a different radial position. Independent of the number of layers, the radial mid-plane of a tension element 1 as a whole is preferably located at the level of the neutral axis of the drive belt 1 . Each support element 50 comprises a pair of contact surfaces 54a, 54b for contacting the contact surfaces of a pair of pulley sheaves. The contact surfaces 54a, 54b of a support element 50 are formed as surfaces of the bottom piece 20 facing in opposite axial directions of the drive belt 1 . Like in the state of the art, the contact surfaces 54a, 54b of a support element 50 have an inclined position with respect to each other so as for the two contact surfaces 54a, 54b to fit the inclined contact surfaces of a pair of pulley sheaves. The two contact surfaces 54a, 54b of a support element 50 are preferably positioned symmetrically or substantially symmetrically with respect to the neutral axis of the drive belt 1 , so that no tilting moment or only a limited tilting moment is exerted on the support element 50.

Like in the state of the art, a portion of the support element extending radially below the neutral axis of the drive belt 1 may be tapered so as to facilitate tilting of adjacent support elements 50a, 50b with respect to each other to allow bending of the drive belt 1 . In a stretched configuration, adjacent support elements 50a, 50b are positioned at a distance with respect to each other of about 0.1 mm.

The wire or thread 40 may comprise one or more aramid fibers, wherein the wire 40 further may be spun or have a woven structure. A diameter of the wire 40 may be in the order of 0.3-1 .8 mm, the diameter preferably being around 0.9 mm. Such a wire may for instance be woven from a number of fibers having a diameter of about 12 μηι. Other materials such as carbon fiber or glass fiber may also be used, possibly even steel wire. Also, multiple wires may be used.

It is noted, that each coiled wire has loose ends. It is noted, that each coiled wire has loose ends. To mitigate the weakening effect of these loose ends, the number of windings preferably is at least three.

Figure 4 shows in more detail a bottom piece 20 and a top piece 30 of a support element in an unassembled position. The bottom piece 20 is a generally U- shaped element having a transverse base portion 22 and a pair of arms 23a, 23b extending up from the base portion 22. The top piece 30 is a generally T-shaped element having a central stem portion 32 and a pair of arms 33a, 33b extending sideways from the stem portion 32. Positioned in between its two arms 23a, 23b, the bottom piece 20 comprises a central space 24 for receiving the stem portion 32 of the top piece 30.

Formed as a recess in each of its arms 23a, 23b, the bottom piece 20 comprises a receiving space 21 a, 21 b. Pending from each of its arms 33a, 33b, the top piece 30 comprises a fixing leg 31 a, 31 b. The receiving spaces 21 a, 21 b are formed such that when the stem portion 32 of the top piece 30 is received in the central space 24 of the bottom piece 20, each of the fixing legs 31 a, 31 b is received in a corresponding receiving space 21 a, 21 b of the bottom piece 20. The shape of a fixing leg 31 a, 31 b and the corresponding receiving space 21 a, 2 b are adapted to each other so that a top piece 30 is fixed with respect to the bottom piece 20 in the axial and circumferential directions of a drive belt 1 when the top piece 30 has been placed on the bottom piece 20. To support the mutual fixation, at the end of each fixing leg 31 a, 31 b, a top piece 30 comprises an abutment surface 34a, 34b which is to abut on a bottom surface of a receiving space 21 a, 21 b so as to be connected to said bottom surface for instance by ultrasonic welding. Also, the shapes of the fixing legs 31 a, 31 b and the receiving spaces 21 a, 21 b may be mutually adapted to be glued together so as to connect the top piece 30 to the bottom piece 20.

At the bottom end of the stem portion 32, the top piece 30 comprises a surface 70b which in the assembled support element 50 forms a top surface of the slit 55. At a side of the base portion 22 facing the central space 24, the bottom piece comprises a surface 70a which in the assembled support element 50 forms a bottom surface of the slit 55. Each of the two surfaces 70a, 70b is herein also referred to as an attachment surface.

Each attachment surface 70a, 70b is provided with a relief 75a, 75b for enlarging the area of attachment between the support element 50 and the tension element 10. In the embodiment shown in Figure 3, the reliefs 75a, 75b are each formed as a ribbed surface having a number of recesses extending in the

circumferential direction of the drive belt, each recess covering the whole of the attachment surface 70a, 70b in said direction.

Figure 5 shows the bottom piece 20 and top piece 30 of Figure 4 in an assembled position, the bottom piece 20 and the top piece 30 thus forming a complete support element 50. In the depicted embodiment, the relief 75b on the top piece 30 is complementary to the relief 75a on the bottom piece 20 such that a recess in one relief 75a, 75b faces a protrusion in the other relief 75a, 75b. The two reliefs 75a, 75b together form a relieved slit 55 of constant height.

Figure 6 shows a portion of a transverse cross section through a support element of a drive belt according to the invention. The portion shows a slit 55 of the support element, the relief 75a of an attachment surface on a bottom piece of the support element forming the bottom surface of the slit 55, a relief 75b of an

attachment surface on a top piece of the support element forming the top surface of the slit 55, and a number of windings 41 a, 41 b extending through the slit 55.

Each relief 75a, 75b comprises a number of recesses 71 . Each pair of recesses 71 a, 71 b is separated by a protrusion 72a. The protrusion 72a is of triangular prismatic shape, and thus has a triangular transverse cross section as shown in Figure 6. The protrusion 72a has a top angle a measured as the angle between its flanks, which angle in the embodiment shown in Figure 6 is around 65 degrees. The top 72a" itself of the protrusion is rounded, which allows the top 72a' to function as an area of attachment between a winding 41 and the support element. The protrusion 72a has a base width W measured as the distance between two recesses 71 a, 71 b lining the protrusion 72a.

A distance between the respective tops 72a", 72b' of two adjacent protrusions 72a, 72b is smaller than the diameter of a winding 41 a, so that a portion of a winding 41 a in the slit 55 is in contact with both protrusions 72a, 72b. This promotes a strong bond between the winding 41 a and the support element. In Figure 6, the ratio between said diameter and said distance is about 0.5. Said ratio is equivalent to the ratio of a certain number of windings comprised by a drive belt according to the invention and a number of recesses provided in the relief of a support element as seen in the transverse direction of the drive belt.

The winding 4 a is received in the recess 71 a lined by the two protrusions

72a, 72b, the winding 41 a thus having an area of attachment with the support element comprising portions of the flanks of both of said two protrusions 72a, 72b. This promotes a strong bond between the winding 41 a and the support element. The strong bond is further promoted by the fact that the winding 41 a is pressed into said recess 71 a by a protrusion 72c facing said recess 71 a, which protrusion 72c is present in the opposite relief 70b.

It is noted that in Figure 6, an adhesive is not indicated. In principle, an adhesive may however be present at all locations where it can attach a winding 41 a to an attachment surface 70a, 70b or to an adjacent winding 41 b.

In the following, a method for manufacturing a drive belt according to the invention is described with reference to Figures 7-9.

Figure 7 shows a mounting device 200 comprising a mounting drum 210 and a pair of positioning rings 220a, 220b mounted on the mounting drum 210.

The mounting drum 210 is substantially disc-shaped, comprising a cylindrical outer surface 21 1 . The positioning rings 220a, 220b are each fitted around the mounting drum 210, each positioning ring 220a, 220b being located at an edge of the outer surface 21 1 . In between the pair of positioning rings 220a, 220b, the mounting device 200 comprises an annular mounting space 221 extending along the full circumference of the mounting drum 210. At a side facing the mounting space 221 , each positioning ring 220a, 220b is provided with a sequence of receiving spaces 222a, 222b. Figure 7 furthermore shows a number of bottom pieces 20 that have been positioned in said receiving spaces 222a, 222b. Figure 8 shows in more detail the portion of the mounting device 200 of Figure 7 having positioned thereon said number of bottom pieces 20. Each bottom piece 20 is positioned in the mounting space 221 with it base portion 22 resting on the outer surface 21 1 of the mounting drum 210, each of its arms 23a, 23b at least for a part being received in a pair of opposite receiving spaces 222a, 222b provided in the positioning rings 220a, 220b. The mutual distance of the receiving spaces 222a, 222b within each positioning ring 220a, 220b is adapted to the mutual distance of a number of bottom pieces 20 in a drive belt according to the invention, such that the bottom pieces 20 of a sequence of such pieces received in the receiving spaces 222a, 222b have the same mutual position as in such a drive belt.

In a method for manufacturing a drive belt according to the invention, a mounting device as depicted in Figures 7 and 8 is provided, as well as a number of support elements 50 as depicted in Figure 4, each support element 50 comprising a bottom piece 20 and a top piece 30. The different bottom pieces 20 are positioned in a sequential fashion along the full circumference of the mounting drum 210.

Furthermore, a wire is provided, which is then coiled around the assembly of bottom pieces 20 on the mounting drum 2 0. After the coiling step, the top pieces 30 are mounted on each of the bottom pieces 20 positioned on the drum, such as to form the support elements 50.

In assembling the support elements, the fixing legs 31 a, 31 b of a top piece 30 are inserted in the receiving spaces 21 a, 21 b of the corresponding bottom piece 20. An adhesive may be provided in the receiving space 21 a, 21 b so as to physically connect the top piece 30 to the bottom piece 20. The top piece 30 and the bottom piece 20 may also be connected by ultrasonic welding, in which the abutment surface 34a, 34b is welded to a bottom surface of said receiving space 21 a, 21 b.

Preferably, the wire 40 is coiled as indicated in Figure 9, showing a number of windings 41 arranged side by side, the windings 41 touching each other and covering the whole of the base portion 22 of a bottom piece 20 in between the two arms 23a, 23b. Within the scope of the invention, the diameter of the wire 40 and the distance between the two arms 23a, 23b may be adapted to each other so that this effect can be obtained.

An adhesive may be applied to the wire 40, to the top and bottom pieces 20, 30, or both of the wire 40 and the top and bottom pieces 20, 30. The adhesive may be applied either before or after the coiling step. Depending on the type of adhesive used, the manufacturing method may furthermore also comprise a step for hardening the adhesive after it has been applied.

After the drive belt has been completed it can be removed from the mounting device 200 by disassembling the mounting device 200 so as to remove either one of the positioning rings 220a, 220b from the mounting drum, after which the completed drive belt can be slid sideways off the mounting drum 210.

It should be clear to a person skilled in the art that the present invention is not limited to the exemplary embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the appending claims. Even if certain features are recited in different dependent claims, the present invention also relates to an embodiment comprising these features in common. Furthermore, any reference signs in a claim should not be construed as limiting the scope of that claim.