NL1039972C2 - Transverse segment for a pushbelt for a continuously variable transmission and method for blanking it. - Google Patents

Description

TRANSVERSE SEGMENT FOR A PUSHBELT FOR A CONTINUOUSLY VARIABLE TRANSMISSION AND METHOD FOR BLANKING IT

This disclosure concerns a transverse segment that is destined 5 to be part of a pushbelt for a continuously variable transmission. A pushbelt for a continuously variable transmission is commonly known. Such a pushbelt usually comprises two bundles of continuous bands or rings that carry a number of transverse segments. The transverse segments are movably arranged along the entire 10 circumference of the bands and transmit forces that are related to the operation of the transmission wherein the pushbelt is provided.

In the following description of the transverse segment, the mentioned directions refer to the situation in which the transverse segment is part of the pushbelt. A longitudinal direction of the 15 transverse segment corresponds to a circumferential direction of the pushbelt. A vertical transverse or height direction of the transverse segment corresponds to a radial direction of the pushbelt. A horizontal transverse direction or width direction of the transverse segment corresponds to a direction perpendicular to 20 both the longitudinal direction and the vertical transverse direction. The indication of any transverse segment as subsequent transverse segment or previous transverse segment with respect to an adjacent transverse segment is related to a direction of movement of the pushbelt.

25 In the horizontal direction, the transverse segment is on both sides provided with openings for at least partially receiving the bundles of bands. For the purpose of supporting the bundles of bands, the transverse segment comprises carrying surfaces. For the purpose of contact between the transverse segment and pulley 30 sheaves of a continuously variable transmission, the transverse segment is on both sides, as seen in the horizontal direction, provided with pulley sheave contact surfaces, which are divergent in the direction of the carrying surfaces.

In the vertical direction, the transverse segment comprises 35 successively a base portion, a middle portion of which the dimensions in the horizontal direction are smaller than those of the base portion, and a top portion of which the dimensions in the horizontal direction at the location of the connection to the middle portion are larger than those of the middle portion. The 1 03 9972 2 basis portion comprises the carrying surfaces and the pulley sheave contact surfaces. At the pushbelt, the base portion is located at the side of the inner circumference of the pushbelt, whereas the top portion is located at the side of the outer circumference of 5 the pushbelt. An important function of the middle portion is interconnecting the base portion and the top portion.

The transverse segment has two main body surfaces, namely a front surface and a back surface, which extend substantially parallel with respect to each other, substantially perpendicular to 10 the longitudinal direction. At least a part of the front surface of the transverse segment is designed to abut against at least a part of the back surface of a subsequent transverse segment in the pushbelt, whereas at least a part of the back surface of the transverse segment is designed to abut against at least a part of 15 the front surface of a previous transverse segment in the pushbelt.

In the pushbelt, two adjacent transverse segments are tiltable with respect to each other about a tilting edge, which is usually defined at the front surface of each transverse segment, and which extends over the entire width of the transverse segment. Usually, 20 the tilting edge is formed as a convexly curved area of the front surface, which area separates two portions of said front surface that are oriented at an angle relative to one other. An important function of the tilting edge is to provide the mutual contact between adjacent transverse segments that are located between the 25 pulley sheaves of a pulley. The tilting edge is intended to arrange that the forces which are related to a. movement of the pushbelt are transmitted from any transverse segment to a subsequent - transverse segment in a controlled manner.

The transverse segment is manufactured from basic material by 30 means of a blanking process. In the blanking process, a cutting member and a supporting member are applied, wherein the cutting member is designed to cut the transverse segment from the basic material under the influence of a cutting force, and wherein the supporting member is designed to support the transverse segment by 35 a supporting force during the blanking process. During the blanking process, the cutting member penetrates the basic material under the influence of pressure, wherein a mutual movement of the cut transverse segment and the basic material is allowed. At that moment, the transverse segment is clamped between a cutting surface 3 of the cutting member and a supporting surface of the supporting member. Preferably, the front surface of the transverse segment is formed at the side of the supporting member, whereas the back surface is formed at the side of the cutting member. Due to the 5 pressure being prevalent during the blanking process, the shape of the supporting surface is then a determining factor regarding the shape of the front surface of the transverse segment, whereas the shape of the cutting surface is a determining factor regarding the shape of the back surface of the transverse segment.

10 It is a well-known feature of the above-described blanking process that, at least in the aforementioned setup thereof, convexly curved transition surfaces are formed between the front surface and the circumference surface of the transverse segment that is newly formed, i.e. cut out in such process. These 15 transition surfaces are also known as contraction zones or "Einzug" areas in the art. In the transverse segment, such a contraction zone is present a/o below, i.e. radially inward of both openings between the respective carrying surfaces and the front surface of the transverse segment.

20 Because no contraction zone is present where the middle portion and the body portion of the transverse segment meet, i.e. in-between the openings of the transverse segment, the thickness of the transverse segment just below the carrying surfaces varies along the width thereof. This means that the tilting edge cannot be 25 located close to the carrying surfaces. More in particular, if the tilting edge would be located in the contraction zones below the carrying surfaces, the adjacent transverse segments would arrive in contact with each other only over the central part of the tilting edge, i.e. over approximately the width of the middle portion, 30 where no contraction zone is present and the transverse segment is at its thickest. Such width-wise limited, central mutual contact between the adjacent transverse segments is considered to be detrimental to the mechanical strength and wear resistance of the pushbelt, as described in detail in EP-A-1 458 992.

35 This latter publication also teaches to apply a specifically shaped cutting member in the blanking process, which cutting member is shaped to force material from other parts of the base portion into the said contraction zones below the carrying surfaces. With this latter cutting member the radial extent of these latter 4 contraction zones is reduced. Thus this known blanking process thus enables the tilting edge to be located in relatively close proximity to the carrying surfaces in the radial direction.

Inter alia, it is noted that it is generally considered a 5 favourable and/or desirable feature in the pushbelt design that the tilting edge is located as close to the carrying surface in the radial direction as practically possible, in order to minimize a relative movement between the transverse segments and the bundles of bands and thus to minimise friction losses in the sliding 10 contact between these two component parts of the pushbelt.

According to the present disclosure, the teaching of EP-A-1 458 992 can be taken one step further and the tilting edge can be located closer to the carrying surfaces in the radial direction. The present disclosure relies on the insight that the mutual 15 contact at the tilting edge between the adjacent transverse segments in the pushbelt need not necessarily occur along the entire width-wise extent thereof as implied by EP-A-1 458 992.

Although such mutual contact may indeed not be concentrated in the central part of the base portion of the transverse segment, this 20 does not mean that it may not be concentrated at the lateral sides thereof instead. To the contrary, according to the present disclosure the said mutual contact may be completely avoided at the central part of the base portion without detriment to the performance of the pushbelt.

25 Based on the above two insights, it is presently proposed to provide the transverse segment with a recessed area, which' recessed area extends in radial outward direction from the tilting edge, preferably from below the tilting edge, to at least the (radial) level of the carrying surface and preferably to a position in the 30 middle portion or even in the top portion of the transverse segment. The width of the recessed area corresponds to at least the width of the middle part of the transverse segment. Hereby, the tilting edge may be favourably located close to the carrying surfaces, i.e. in the said contraction zones below these carrying , 35 surfaces, whereby the recessed area avoids the above-explained detrimental, i.e. width-wise limited, central mutual contact between the adjacent transverse segments.

Although the recessed area may, to same effect, be provided on the back surface, it is preferably provided on the front surface of 5 the transverse segment that also includes the tilting edge. Hereby, the material that is displaced to form the recessed area can conveniently be directed towards the contraction zones below the carrying surfaces to favourably reduce the extent thereof.

5 Further, the recessed area preferably extends in the thickness direction of the transverse segment just as far as the contraction area does. In reality, however, this extent of the recessed area is difficult or even impossible to produce in the blanking process in terms of both the compressive force that would have to be exerted 10 on the transverse segment and the accompanying loss of dimensional accuracy of the transverse segment. Therefore, the depth of the recessed area is in practice preferably limited to the range between 25 and 150 microns, e.g. around 100 microns. This means that also in the presently proposed, novel transverse segment the 15 tilting edge should be located at the some (radial) distance below the carrying surface, however, by the provision of the recessed area such distance can be substantially reduced relative to the conventional transverse segment and pushbelt designs that are currently in production and/or use. More in particular, where in 20 the conventional transverse segment the tilting edge is located at a distance from the carrying surface of at least 1 mm (up to 1.2 mm) , the recessed area of the present transverse segment allows this distance to be reduced to 0.9 mm or less. A radial separation between 0.4 and 0.6 mm between the carrying surfaces and the 25 tilting edge of the transverse segment being considered the optimum when taking into account all of the above influence factors.

It is noted that the presently proposed, novel transverse segment can be manufactured with the blanking process and cutting tool that are described in EP-A-1 458 992, of course with the 30 additional requirement that the centrally located, relatively raised part of the cutting member is raised sufficiently for providing the transverse segment with the said recessed area.

The invention will be explained in detail on the basis of the following description of preferred embodiments of the invention 35 with reference to the drawing, in which equal reference signs indicate equal or similar parts, and in which: figure 1 is a diagrammatical side view of a continuously variable transmission having a pushbelt; 6 figure 2 is a front view of a transverse segment for a pushbelt for a continuously variable transmission; figure 3 is a side view of the transverse segment which is shown in figure 2; 5 figure 4 diagrammatically shows a longitudinal section of a blanking area of a blanking device, and of basic material being placed in there; figure 5 diagrammatically illustrates the blanking process; figure 6 is a cross-section of a part of the known transverse 10 segment, including a tilting edge and a carrying surface thereof; figure 7 illustrates a problem associated with the locating of the tilting edge close to the carrying surface in the known transverse segment; figure 8 illustrates a novel design for the transverse segment by 15 way of a cross-section of a part thereof that corresponds to the part shown in figure 6 and 7; and figure 9 provides a front view of the novel transverse segment illustrated in figure 8.

Figure 1 diagrammatically shows a continuously variable 20 transmission, such as for utilization in a motor vehicle. The continuously variable transmission is indicated in general by the reference sign 1.

The continuously variable transmission 1 comprises two pulleys 4, 5 being arranged on separate pulley shafts 2, 3. A pushbelt 6 is 25 provided in a closed loop around the pulleys 4, 5 and serves for transmitting torque between the pulley shafts 2, 3. The pulleys 4, 5 are each provided with two pulley sheaves, wherein the pushbelt 6 is positioned and clamped between said two pulley sheaves, so that with the help of friction a force may be transmitted between the 30 pulleys 4, 5 and the pushbelt 6.

The pushbelt 6 comprises two endless carriers 7 that are composed of a bundle of a number of mutually nested continuous bands. Transverse segments 10 are arranged on the carriers 7 forming an essentially contiguous row along the entire 35 circumference thereof. The transverse segments 10 are provided movable with respect to the endless carriers 7, at least in the circumferential direction thereof. For the sake of simplicity, only a few of these transverse segments 10 are shown in figure 1.

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Figures 2 and 3 show the transverse segment 10 of the known pushbelt 6 in more detail. A front surface of the transverse segment 10 is indicated in general by the reference sign 11, whereas a back surface of the transverse segment 10 is indicated in 5 general by the reference sign 12. In the following, the front surface 11 and the back surface 12 are generally indicated as main body surfaces 11, 12.

In the vertical direction, the transverse segment 10 comprises successively a base portion 13 of predominantly trapezoidal shape, 10 a relatively narrow middle portion 14 and a top portion 15 of predominantly triangular shape. In the pushbelt 6, the base portion 13 is located at the radially inner circumference side of the carrier 7, whereas the top portion 15 is located radially outward of the carrier 7. Furthermore, in the pushbelt 6, at least a part 15 of the front surface 11 of the transverse segment 10 abuts against at least a part of the back surface 12 of a succeeding transverse segment 10, whereas at least a part of the back surface 12 of the transverse segment 10 abuts against at least a part of the front surface 11 of a preceding transverse segment 10.

20 To the left and the right of the middle portion 14, the base portion 13 of the transverse segment 10 comprises two carrying surfaces 16 that each serve to support a respective one of the two endless carriers 7 in radial outward direction. Furthermore, the base portion 13 comprises two pulley sheave contact surfaces 17. 25 When the transverse segment 10 moves over the pulley 4, 5, contact between the transverse segment 10 and contact surfaces of the pulley sheaves is established through said pulley sheave contact surfaces 17.

At the front surface 11 in the base portion 13 of the 30 transverse segment 10, a tilting edge 18 is defined. The tilting edge 18 is represented by a convexly curved area of the front surface 11, which area separates two portions of the said front surface 11 that are oriented at an angle relative to one other, and extends along the entire width of the transverse segment 10. The 35 tilting edge 18 is located close to, but still at some distance below, i.e. radially inward from, the carrying surfaces 16. An important function of the tilting edge 18 is to provide a mutual pushing contact between the adjacent transverse segments 10, when 8 said transverse segments 10 are in a tilted position relative to one another at the pulleys 4, 5.

Also, at the front surface 11 of the transverse segment 10, a projection 21 is provided. In the shown example, the projection 21 5 is arranged in the top portion 15, and corresponds in position to a slightly larger hole provided in the back surface 12. In figure 3, the hole is depicted by means of dashed lines and indicated by the reference sign 22. In the pushbelt 6, the projection 21 of the transverse segment 10 is at least partially located inside the hole 10 22 of an adjacent transverse segment 10. The projection 21 and the corresponding hole 22 serve to prevent or at least limit mutual displacement of adjacent transverse segments 10 in a plane perpendicular to the circumferential direction of the pushbelt 6.

The transverse segment 10 is typically cut out of plate-shaped 15 basic material 50 in a blanking process by means of a blanking device 60. In figures 4 and 5, the blanking device 60 and the basic material 50 are diagrammatically illustrated in a cross-section. In the blanking device 60 a cutting member 30, a supporting member 40, a guiding plate 70 and a mould 80 are applied. The guiding plate 70 20 and the mould 80 serve both to clamp the basic material 50 between them and to contain the cutting member 30 and the supporting member 40 in respective guiding spaces 71, 81 thereof.

The part 51 of the basic material 50 that is located between the cutting member 30 and the supporting member 40 is destined to 25 become the transverse element 10. During the actual cutting, the bottom or working surface 31 of the cutting member 30 and a top or working surface 41 of the supporting member 40 are pressed against the basic material 50, at mutually opposite sides thereof, and the cutting member 30 and the supporting member are pushed in unison 30 completely through the basic material 50 in the general direction from the cutting member 30 to the supporting member 40 cutting out the transverse segment 10, as is illustrated in figure 5.

Accordingly, the said working surfaces 31, 41 have an outline that substantially corresponds to the outer contour of the 35 transverse segment 10. Moreover, the front surface 11 of the transverse segment 10, including the projection 21 and the tilting edge 18, is shaped by the working surface 41 of the supporting member 40 and the back surface 12 of the transverse segment 10, including the hole 22, is shaped by the working surface 31 of the 9 cutting member 30. This particular arrangement of the cutting member 30 and of the supporting member 40 may, however, be reversed, or the supporting member 40 may be omitted altogether. In this latter case, the front surface 11 and the back surface 12 of 5 the transverse segment 10 are typically shaped in a separate process step, i.e. preceding and/or following the step of blanking the transverse segment 10.

It is a well-known feature of the above-described blanking process that, at least in the aforementioned setup thereof, 10 convexly curved transitions 20 are formed between the front surface 11 and the circumference surface (including the pulley sheave contact surfaces 17 and the carrying surfaces 16) of the transverse segment 10. These transitions 20 are also known as contraction zones 20 or "Einzug" areas 20 in the art. In the transverse segment 15 10 such a contraction zone 20 is a/o present below, i.e. radially inward of both openings between the respective carrying surfaces 16 and the front surface 11 of the transverse segment 10, as indicated in figure 5, as well as figure 2. As a consequence, the tilting edge 18 is in practice located a certain distance below the 20 carrying surfaces 16, i.e. radially inward from and outside the contraction zones 20, even though, theoretically speaking, the tilting edge 18 of the base portion 13 is preferably located close to, even immediately adjacent to the carrying surfaces 16.

In figure 6 the known design of the transverse segment 10 is 25 schematically reproduced by way of a cross-section of a part thereof including the tilting edge 18, the carrying surface 16 and the contraction zone 20 there between. In figure 6 the convex curvature of the tilting edge 18 has been exaggerated to be able to discern the convex shape thereof on the scale of this figure. Also 30 the size of the contraction zone 20 has been exaggerated for such purpose.

Figure 6 illustrates that in the known design of the transverse segment 10 the top side TS of the tilting edge 18 is provided at some distance A radially inward from (i.e. in figure 6: 35 to the left of) the contraction zone 20 below the carrying surface 16. An example of such known design is provided by EP-A-1 458 992, according to which document the radial separation, i.e. distance A, between the tilting edge 18 and the contraction zone 20 below the carrying surface 16 is chosen as small as possible.

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If the tilting edge 18 would be located even higher on the transverse segment 10 (i.e. more towards the right in figure 6) and no such radial separation is applied, the convex curvature of tilting edge 18 would merge with the convex curvature of the 5 contraction zone 20, as illustrated in figure 7. As a result, the tilting edge 18 would no longer be formed in a single straight line, but rather would comprise three parts 18', 18", namely one central part 18' located radially inward of in the middle portion 14 of the transverse segment 10 and two lateral parts 18" located 10 radially inward of the two carrying surfaces 16 on either side of the side central part 18' of' the tilting edge 18. These latter two lateral parts 18" of the tilting edge 18 below the carrying surfaces 16 are retracted relative to the central part 18' thereof, meaning that a local thickness of the transverse segment 10 is less 15 at the said two lateral parts 18" of the tilting edge 18 than at the central part 18' thereof. Thus, in the pushbelt 6 comprising the transverse segments 10 according to figure 7, the adjacent transverse segments 10 would only make contact through the central part 18' of the tilting edge 18, which is considered to be 20 detrimental to the mechanical strength and wear resistance of the pushbelt 6.

To still allow the tilting edge 18 to be located high on the transverse segment 10 (i.e. more towards the right in figure 6), e.g. between 0.2 and 0.8 mm radially inward of the carrying 25 surfaces 16, one of the main body surfaces 11, 12 thereof is provided with a centrally located recessed area 25. In the figures 8 and 9 such novel design of the transverse segment 10 is illustrated with the recessed area 25 being provided in the front surface 11 thereof.

30 To ensure that the contact between the adjacent transverse segments 10 in the pushbelt 6 takes place at the (two parts on either side of the recessed area 25 of the) tilting edge 18 in the contraction zone 20 below the carrying surface 16, the said recessed area 25 extends upwards from the tilting edge 18 and is at 35 least as wide as the middle portion 14 of the transverse segment 10. In the embodiment thereof of figure 9, the recessed area 25 is chosen somewhat wider to -in the axial direction- also cover the (stress relief) notches 26 that are typically provided between the side faces of the middle portion 14 and the carrying surfaces 16 of 11 the base portion 13. Moreover, in figure 9, the recessed area 25 is chosen higher and -in the radial direction- extends from below the tilting edge 18 outwards up to and including the radial outer edge of the transverse segment 10.

5 The depth of the recessed area 25, in particular defined relative to the starting thickness of the basic material 50, determines the extend thereof in radially inward direction, at least in combination with the thickness of the basic portion 13. The thus defined depth of the recessed area 25 is present in figure 10 9 only at the top portion 15, i.e. between the dotted line 25 representing the bottom of the recessed area 25 and the front surface 11. After all, the top side TS of the tilting edge 18, representing the thickest part of the base portion 13, is retracted by it merging with the contraction zone 20.

15 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 merely provided as non-binding examples of the 20 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 25 (are) not limited to the embodiments and/or the examples that are explicitly mentioned herein, but also encompasses amendments, modifications and practical applications thereof, in particular those that lie within reach of the person skilled in the relevant art.

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Claims (13)

Cross section (10) for a push belt (6) with two annular carriers (7) and with a number of transverse segments (10) successively and movably placed on the carriers (7), which transverse segment (10), viewed in a width direction is provided on both sides with openings for receiving the carriers (7) bounded in one direction by bearing surfaces (16) of a base portion (13) of the transverse segment (10) located below the apertures, said base portion (13) also comprises a tilting edge (18) in the form of a convexly curved surface extending across it in the width direction and perpendicular to said width direction, characterized in that the base portion (13) comprises a lowered area (25) said direction oriented perpendicularly to the width direction 15 is at least at the height of the tilting edge (18) which extends in that direction at least as far as the bearing surfaces (16) and which extends in the width direction between said bearing surfaces (16) extends. The transverse segment (10) according to claim 1, characterized in that the lowered region (25) extends perpendicularly to the width direction beyond the bearing surfaces (16) and preferably to an extreme edge of the transverse segment (10) . The transverse segment (10) according to claim 1 or 2, characterized in that the lowered region (25) is located on the same side of the transverse segment (10) as the tilting edge (18) and that the tilting edge (18) the lowered area (25) is divided in two 30 The transverse segment (10) according to claim 1, 2 or 3, characterized in that the tilting edge (18) is located at a distance of less than 0.9 millimeters below the bearing surfaces (16). The transverse segment (10) according to a preceding claim, characterized in that the tilting edge (18) is located at a distance of between 0.4 and 0.6 mm below the bearing surfaces (16). 1 03 9972 The cross section (10) according to a preceding claim, characterized in that the lowered area (25) is between 25 and 250 micrometers lower than surrounding parts of the cross section (10). 5 7. Method comprising cutting out a transverse segment (10) from a base material (50) in a blanking process, which, viewed in the width direction, is provided on both sides with openings which are bounded in one direction by 10 bearing surfaces (16) of a base portion (13) of the transverse segment (10) located below the openings, and wherein the transverse segment (10) is also provided with a tilting edge (18) in the form of a transverse section perpendicular to the transverse segment (10) and perpendicular to said widthwise, convexly curved surface forming part, at least adjoining, a first main body surface (11) of the transverse segment (10) oriented substantially perpendicularly to the bearing surfaces (16), characterized in that centrally located in the first main body surface (11), or in a second main body surface (12) thereof located on the other side of the transverse segment (10), an indentation (25) is provided which is situated in said perpendicular is oriented at the width direction at least at the level of the tilting edge (18), which in that direction extends at least up to the bearing surfaces (16) and which extends in the width direction between said bearing surfaces 25 (16). The method according to claim 7, characterized in that in the blanking process at least one side of the bearing surfaces (16) a convex curved transition surface (20) is formed in each case and that the tilting zone (18) is located in, at least at least adjoins those transition surfaces (20). The method according to claim 7 or 8, characterized in that the tilting zone (18) is divided in two by the central depression (25). The method according to claim 7, 8 or 9, characterized in that the central depression (25) extends beyond the bearing surfaces (16) and preferably to an extreme edge or edges of the transverse segment (10). The method according to at least one of claims 7 to 10, characterized in that the tilting edge (18) is arranged at a distance of less than 0.9 mm from the bearing surfaces (16). The method according to at least one of claims 7 to 11, characterized in that the tilting edge (18) is at a distance of 0.8 mm or 10 less and preferably at a distance between 0.4 and 0.6 mm, under the bearing surfaces (16). The method according to at least one of claims 7 to 12, characterized in that a thickness dimension of the transverse segment (10) in the lowered region (25) between 25 and 250 micrometers and preferably around 100 micrometers is smaller than a corresponding thickness dimension of the base material (50). 1 03 9972