This disclosure relates to a method for manufacturing a transverse segment that is destined to be part of a drive belt for a continuously variable transmission with two pulleys and the drive belt. Such a drive belt is commonly known and is mainly applied running around and between the two transmission pulleys, which pulleys each define a V-groove of variable width wherein a respective circumference part of the drive belt is held.

A known type of drive belt comprises an essentially contiguous row of transverse segments made from steel, in particular DIN 1.2003 steel (75Crl), that are mounted on and around the circumference of an endless carrier that is likewise made from steel, in particular maraging steel. Each such transverse segment defines a slot that is open towards either the radial outside of the drive belt or to an axial side thereof and that accommodates and confines a respective circumference section of the endless carrier, while allowing the transverse segments to move along the circumference thereof. The endless carrier is formed by a number of flat and thin rings that are mutually stacked in the radial direction. This particular type of drive belt, also denoted in the art as a pushbelt, is for example known from the international patent publications WO2015/177372-A1 and W02015/101659-A1.

In the above and the below description the axial, radial and circumference directions are defined relative to the drive belt when placed in a circular posture. A thickness direction and dimension of the transverse segments is defined in the circumference direction of the drive belt, a height direction and dimension of the transverse segment is defined in the said radial direction and a width direction and dimension of the transverse segment is defined in the said axial direction. A thickness direction and dimension of the ring stack is defined in the said radial direction and a width direction and dimension of the ring stack is defined in the said axial direction.

In the row of transverse segments of the drive belt, at least a part of a front main body surface of the transverse segment abuts against at least a part of a rear main body surface of a respectively preceding transverse segment in the said row, whereas at least a part of the rear main body surface of the transverse segment abuts against at least a part of the front main body surface of a respectively succeeding transverse segment. At least one of these front and rear surfaces of the transverse segment, for example the front surface includes an axially extending, convexly curved surface section that is denoted rocking edge hereinafter. This rocking edge divides the transverse segment into a radially outer, or top portion and a radially inner or bottom portion, whereof the bottom portion becomes thinner in downward, i.e. radial inward direction, whereas the top portion is provided with an, at least comparatively, constant thickness. By such thinner bottom portion, the abutting transverse segments in the drive belt are able to tilt, i.e. rotate relative to one another, while pivoting on and remaining in mutual contact through the rocking edge. Thus, together the features of the rocking edge and the thinner bottom portion of the transverse segments allow the drive belt to follow a curved trajectory imposed by the transmission pulleys.

Inter alia, it is noted that the thinner bottom portion of the transverse segment may start with a step providing a sudden, i.e. essentially stepwise thickness reduction of the basic material, or the basic material may be provided with a tapered central part providing a gradual reduction of the thickness of the basic material or with such tapered central part and the thickness step in combination.

Typically the transverse segments are manufactured, i.e. cut and shaped from a strip or plate of basic material in a known blanking process by means of a known blanking device. The known blanking device comprises a die, a guide plate and a blanking punch, whereof the blanking punch is provided with an outline essentially corresponding to the outer contour of the transverse segment to be formed, while the die and guide plate are provided with internal cavities with a corresponding contour, in which cavities the blanking punch is contained. In the known blanking process, the basic material is clamped by and between the guide plate and the die and the blanking punch is pressed through the basic material from the side of the guide plate to the side of the die, thus cutting the transverse segment out of the basic material. Furthermore, in the known blanking device and process, a counter punch or ejector is applied on the opposite side of the basic material relative to the blanking punch. This latter arrangement of the blanking device allows a front surface and/or a rear surface of the transverse segment to be shaped in thickness direction during the blanking thereof, through the plastic deformation of the basic material by being clamped by and between the end faces of the blanking punch and the counter punch respectively, which end faces engage the strip or plate of basic material from both sides thereof. In particular, the rocking edge is shaped in this way by a concavely curved section of the end face of the counter punch.

According to the present disclosure, the known blanking process is difficult to control in mass-manufacture in terms of the resulting thickness of the transverse segments. In particular, relatively small thickness variations may occur along the width or the height of the transverse segment, in particular along the width of the rocking edge or between the rocking edge and the top portion of the transverse segment. Although, by the use of the said counter punch, such thickness variations are comparatively small per se (i.e. are in the order of microns only), in the drive belt these variations will disadvantageously accumulate in the said row of abutting transverse segments and can lead to unwanted vibrations and/or increase in stress levels during operation of the drive belt. In practice very high requirements are therefore defined in relation to the thickness and flatness of the said thicker and thinner parts of the basic material, as well as the accuracy and consistency of the blanking process and device.

The present disclosure aims to alleviate these requirements, while maintaining or possibly improving the customary production rate and/or the (shape) accuracy of the thus produced transverse segments .

According to the present disclosure, such aim can be realised with a novel blanking process by applying therein both:

a basic material that is pre-formed with two flat parts of constant, but mutually different thickness, whereof a thicker part corresponds with, at least, a radially outermost part of the said top portion of the transverse segment to be formed and the thinner part corresponds with, at least, a radially innermost part of the said bottom portion of the transverse segment to be formed; and

a counter punch and/or a blanking punch with an end face provided with a protrusion, i.e. with a higher lying section, that extends in the width direction of the transverse segment to be formed and that engages the thinner part of the basic material; and by

pressing the said protrusion into the basic material whereby a depression is formed in the thinner part of the basic material before the actual cutting of the transverse segment by pressing the blanking punch through the basic material.

According to the present disclosure, by the pressure exerted between the blanking punch and the counter punch at the said protrusion thereof, the transverse segment to be formed is firmly clamped and held in place during the actual cutting thereof, not only at its rocking edge and radially outward thereof, but also at some distance radially inward of the rocking edge . Hereby, the transverse element will be more accurately formed. More in particular, pressure is now exerted by the counter punch on the transverse segment to be formed not only, or at least not mainly, at its rocking edge and at its thicker top portion, but also, or at least more so, at its thinner bottom portion. Such wider, more equally distributed pressure distribution over the height of the transverse segment to be formed, favourably diminishes a tendency of the basic material to shift and/or tilt relative to the blanking punch and/or the counter punch during cutting.

Preferably, the protrusion is shaped oblong, extending over the full, local width of the transverse segment to be formed, such that it can be provided in the end face of the counter punch and/or of the blanking punch relatively easily. Preferably, the long direction of the oblong protrusion, more specifically a basis of a preferred isosceles trapezoidal shape thereof, extends in the width direction of the transverse segment, more preferably across the full width of the bottom portion thereof. In the height direction of the transverse segment, the oblong protrusion preferably extends for at least 0.5 mm, at most 1.5 mm and more preferably for about 1 mm. Preferably, the oblong protrusion protrudes between 10 to 100 microns, preferably 10-50 microns, relative to directly neighbouring sections of the end face of the counter punch and/or of the blanking punch, such that the depression that is formed thereby in the bottom portion of the transverse segment shows a depth of about 10 to 100 microns as well. The aforementioned dimensions of the oblong protrusion and of the said depression formed thereby, apply in particular to basic material whereof the said thicker part has a thickness in the range between 1 and 2 mm and whereof the said thinner part has a thickness in the range between 0.5 and 1.5 mm.

The depression formed in the transverse segment by protrusion of the counter punch and/or of the blanking punch can be located at some distance away from a radially inner, i.e. bottom edge of the transverse segment. In this particular embodiment of the blanking process according to the present disclosure, the basic material is optimally clamped and held in place during the actual cutting of the transverse segment. Preferably in this embodiment, the groove is separated from the bottom edge of the transverse segment by 0.5 to 1.5 mm, in particular by a distance corresponding to the dimension of the groove in the said height direction.

In an alternative embodiment of the blanking process according to the present disclosure, the said oblong protrusion of the counter punch and/or of the blanking punch coincides with the bottom edge of the transverse segment. In this case, a step is formed in the bottom portion of the transverse segment by the oblong protrusion in the blanking process, radially inward whereof the said depression extends to the bottom edge of the transverse segment. Thus, in this particular embodiment of the blanking process, a radially innermost part of the bottom portion of the transverse segment is provided with a reduced thickness, relative to other portions thereof. This latter feature has the advantage that the abutting transverse segments in the drive belt are able to tilt relative to one another to a further degree than without such radially innermost part of reduced thickness. Thus, such radially innermost part of reduced thickness allows the drive belt to follow a more narrowly curved trajectory at the transmission pulleys, such that, for example, a range of transmission ratios provided by the transmission can be favourably increased. In this respect it is noted that the basic material could alternatively be pre-formed with a third flat part corresponding with such radially innermost part of reduced thickness of the transverse segment. However, this latter solution would of course not provide the presently considered improvement to the blanking process.

Preferably, the said oblong protrusion is provided in the end face of the counter punch that is also provided with a concavely curved section to form the rocking edge of the transverse segment. In this case, the end face of the blanking punch can be provided as a predominantly flat surface.

The above-described method for manufacturing the transverse segment will now be explained in more detail by way of example on the basis of the description below with reference to the drawing, in which:

figure 1 is a simplified and schematic perspective view of a transmission with two pulleys and a drive belt;

figure 2 illustrates the known drive belt in a cross-section thereof facing in its circumference direction and also includes a separate side elevation of only the transverse segment thereof;

- figure 3 schematically illustrates the basic process of blanking the transverse segment from basic material in a cross-section of a blanking area of a blanking device;

- figure 4 provides a top elevation of the basic material used in the blanking process of figure 3, as well as a cross-section thereof;

- figure 5 provides a cross-section of the basic material in an alternative embodiment thereof;

figure 6 schematically illustrates a novel blanking process according to the present disclosure in a first embodiment thereof; figure 7 schematically illustrates an embodiments of the transverse segment obtained with the first embodiment of the novel blanking process according to figure 6;

figure 8 schematically illustrates the novel blanking process according to the present disclosure in a second embodiment thereof; figure 9 schematically illustrates a first embodiments of the transverse segment obtained with the second embodiment of the novel blanking process; and

- figure 10 schematically illustrates a second embodiments of the transverse segment obtained with the second embodiment of the novel blanking process.

Figure 1 shows the central parts of a known continuously variable transmission or CVT that is commonly applied in the drive- line of motor vehicles between the engine and the driven wheels thereof. The transmission comprises two pulleys 1, 2 that are each provided with a pair of conical pulley discs 4, 5 mounted on a pulley shaft 6 or 7, between which pulley discs 4, 5 a predominantly V-shaped circumferential pulley groove is defined. At least one pulley disc 4 of each pair of pulley discs 4, 5, i.e. of each pulley 1, 2, is axially moveable along the pulley shaft 6, 7 of the respective pulley 1, 2. A drive belt 3 is wrapped around the pulleys 1, 2 in a closed loop, located in the pulley grooves thereof, for transmitting a rotational movement and an accompanying torque between the pulley shafts 6, 7.

The transmission typically also comprises activation means (not shown) that -at least during operation- impose on the said axially moveable pulley disc 4 of each pulley 1, 2 an axially oriented clamping force that is directed towards the respective other pulley disc 5 of that pulley 1, 2, such that the drive belt 3 is clamped between each such disc pair 4, 5. These clamping forces not only determine a friction force that can maximally be exerted between the drive belt 3 and a respective pulley 1, 2 to transmit the said torque, but also radial positions R of the drive belt 3 in the pulley grooves. These radial position (s) R determine a speed ratio of the transmission. This type of transmission and its operation are well-known per se.

The drive belt 3 comprises two endless carriers 9 that are composed of a bundle of a number of mutually nested continuous bands or rings 10 (see figure 2) . Transverse segments 8 are arranged on the carriers 9 forming an essentially contiguous row along the entire circumference thereof. For improving clarity, only some of these transverse segments 8 are individually indicated in figure 1. The transverse segments 8 are provided movable with respect to the endless carriers 9, at least in the circumference direction thereof.

Figure 2 shows the transverse segment 8 of the known drive belt 3 in more detail. In figure 2 a front view of the transverse segment 8 is shown in a cross-section of the drive belt 3 oriented in the circumference direction thereof and a side elevation of only the transverse segment 8 is included therein as well.

In the vertical direction in figure 2, which vertical direction corresponds to the radial direction of the drive belt 3 when placed in a circular posture outside the transmission, the transverse segment 8 comprises successively a body part 13 of predominantly trapezoidal shape, a relatively narrow neck part 14 and a head part 15 of predominantly triangular shape. In the drive belt 3, the carriers 9 thereof are located on either side of the neck part 14, i.e. in-between the body part 13 and the head part 15 of transverse segment 8.

A circumference surface 16, 17 of the transverse segment 8 comprises two supporting surfaces 16 of the body part 13 to either side of the neck part 14, that each serve to support a respective one of the two endless carriers 9 in radial outward direction. Furthermore, the circumference surface 16, 17 of the transverse segment 8 includes two contacting surfaces 17 of the body part 13 on either axial side thereof, that serve to contact the pulley discs 4, 5 when the transverse segment 8 moves around the respective pulleys 1, 2.

A front main body surface of the transverse segment 8 is indicated in general by the reference sign 11, whereas a back main body surface of the transverse segment 8 is indicated in general by the reference sign 12. At the front surface 11 in the body part 13 of the transverse segment 8, a rocking edge 18 is defined. The rocking edge 18 is represented by a convexly curved area of the front surface 11, which area separates two sections of the said front surface 11 that are oriented at an angle relative to one other, and extends along the entire (axial) width of the transverse segment 8. The rocking edge 18 is located close to, but still at some distance below, i.e. radially inward from, the supporting surfaces 16. An important function of the rocking edge 18 is to provide a mutual pushing contact between the adjacent transverse segments 8, when said transverse segments 8 are in a tilted position relative to one another at the pulleys 4, 5.

At some distance below the rocking edge 18, i.e. also in the body part 13 of the transverse segment 8, a step 20 is defined in the front surface 11 thereof. The step 20 represents a local, i.e. stepwise change of the thickness of the transverse segment 8. Just below such step 20 the thickness of the transverse segment 8 is thus less than just above it.

Also, at the front surface 11 of the transverse segment 8, a stud 21 is provided. In the shown example, the stud 21 is arranged in the head part 15, and corresponds in position to a slightly larger hole 22 provided in the rear surface 12. In figure 2, the hole is depicted by means of dashed lines and indicated by the reference sign 22. In the drive belt 3, the stud 21 of the transverse segment 8 is at least partially located inside the hole 22 of an adjacent transverse segment 8. The stud 21 and the corresponding hole 22 serve to prevent or at least limit mutual displacement of adjacent transverse segments 8 in a plane perpendicular to the circumference direction of the drive belt 3.

The transverse segment 8 is cut out of a strip of basic material 50 in a blanking process that is illustrated in figure 3. The strip of basic material 50 is contoured and, in particular, is pre-formed with a thickness step 53 corresponding to the said step 20 of the transverse segment 8.

In figure 3, four stages of the blanking process are represented in a schematic cross-section of the blanking device 60. In the blanking device 60, a blanking punch 30, a counter punch 40, a guide plate 70 and a die 80 are applied. The blanking punch 30 and the counter punch 40 are provided with an outer contour that essentially corresponds to the outer contour of the transverse segment 8 to be formed. The guide plate 70 is provided with an internal cavity 71 and the die 80 is provided with an internal cavity 81. Both cavities 71, 81 are provided with an inner contour that essentially corresponds to the outer contour of the transverse segment 8 as well, wherein blanking punch 30 and the counter punch 40 and contained. An end face 31 of the blanking punch 30 is arranged to engage the basic material 50 on one side thereof and an end face 41 of the counter punch 40 is arranged to engage the basic material 50 from the other side thereof. In particular, the counter punch end face 41 engages the side of the basic material 50 with the said thickness step 53, which basic material side corresponds with the front surface 11 of the transverse segment 8 to be formed. The counter punch end face 41 is thus shaped to form the rocking edge 18, whereto it includes a concavely curved section. This particular arrangement of the blanking punch 30 and of the counter punch 40 may, however, be reversed.

In a first stage A of the blanking process, the basic material 50 in introduced or at least advanced between the blanking punch 30 and the guide plate 70 on the one hand and the counter punch 40 and the die 80 on the other hand. In a second stage B of the blanking process, the basic material 50 is firmly clamped and held in place by and between the guide plate 70 and the die 80. In a third stage C of the blanking process, the blanking punch 30 and the counter punch 40 are moved towards one another until these exert a considerably pressure on the basic material 50. In this third stage, the end face 31 of the blanking punch 30 shapes the rear surface 12 of the transverse segment 8 that is the still to be formed and the end face 41 of the counter punch 40 shapes its front surface 12. Typically, the rear surface 12 of the transverse segment 8 is shaped as a flat surface by the blanking punch 30, whereas the counter punch 40 shapes at least the convexly curved rocking edge 18 and an inclined surface section between the rocking edge 18 and the step 20 into the front surface 11 thereof. In a fourth stage D of the blanking process, the blanking punch 30 and the counter punch 40 are pushed into the cavity 81 of the die 80, thus separating, i.e. cutting out the transverse segment 8 from the basic material 50.

The solid arrows in figure 3 illustrate the forces that are respectively exerted by the blanking punch 30 and the counter punch 40 on the basic material 50 during the blanking of the transverse segment 8. In particular, in the said third stage C, the front surface 11 of the transverse segment 8 including the rocking edge 18 is shaped by plastic deformation under the influence of the forces exerted by and between the counter punch 40 and the blanking punch 30. In the said fourth stage D, the force exerted by the counter punch 40 is reduced, at least relative to the force exerted by the blanking punch 30, whereby the basic material 50 is pierced by the blanking punch 30 to cut out the transverse segment 8.

Figure 4 provides a top elevation of the basic material 50, as well as a cross-section thereof with the dashed lines indicating the outline of the transverse segment 8 to be formed relative thereto. In figure 4 it is visible that the thickness step 53 of the basic material 50 corresponds to the step 20 in the front surface 11 of the transverse segment 8. Thus, the basic material 50 is provided with a thicker part 51 of thickness T1 and a thinner part 52 of thickness T2. Otherwise the basic material 50 is provided with a predominantly rectangular outer contour. By providing the basic material 50 with the said thickness step 53, at least the radial extent of the material that is to be displaced to correctly form or shape the transverse segment 8 is reduced, at least relative to a basic material 50 having a rectangular cross- section of uniform thickness. Hereby, at least the said third stage C of the blanking process is easier to perform and/or control.

As illustrated in figure 5, it is also known to provide the basic material with a tapered central part 54, defining an inclined surface section thereof, between the thicker part 51 and the thinner part 52 thereof, instead of the said thickness step 53. By such tapered central part 54 of the basic material 50, the forces and/or pressures involved in the blanking process for forming the rocking edge 8 and/or the inclined surface section of the transverse segment 8 can be reduced further. Alternatively, the tapered central part 54 may be combined with a thickness step, as indicated by the dotted line in figure 5. Regardless of whether the basic material is provided with only the step 53, only the tapered central part 54 or with a combination thereof, it comprises the said two flat parts 51 and 52 of constant, but mutually different thickness T1 and T2, whereof the thicker part 51 corresponds with a radially outermost part of the transverse segment 8 to be formed, including at least the head part 15, and whereof the thinner part 52 corresponds with a radially innermost part of that segment 8.

According to the present disclosure, the above described, known method for manufacturing the transverse segment 8, in particular the known blanking process part thereof, can be improved upon. In particular according to the present disclosure, the counter punch 40 is preferably arranged to contact the basic material 50 -and to exert the said pressure- not only at the rocking edge 18 and possibly at the head part 15 of the transverse segment 8 to be formed, but also in the thinner part 52 of the basic material 50 corresponding to a bottom portion of the transverse element 8 radial inward of the thickness step 20 and/or the said inclined surface section thereof. Hereby, a tendency of the basic material 50 and/or of the counter punch 40 to shift and/or tilt during blanking could be advantageously decreased and the accuracy of the blanking process is thus improved further.

A first possible embodiment of the blanking process according to the present disclosure is illustrated in figure 6. Figure 6 represents a cross-section of a blanking device 60 similar to figure 3, in particular the first stage A and the third stage C depicted therein, however limited to the body portion 13 of the transverse segment 8 to be formed and including only the blanking punch 30 and the counter punch 40 of the blanking device 60. The region of the basic material 50 illustrated in figure 6 is indicated in figure 4 as the region contained by the dotted circle C. In figure 6, the dashed lines drawn through the basic material 50 indicate the contours of body portion 13 of the transverse segment 8 to be formed, including its supporting surface 16 and a radially inner, bottom edge 23 of its body portion 13.

According to the present disclosure, the end face 41 of the counter punch 40 is provided with an oblong protrusion 42 opposite the said thinner part 52 of the basic material 50. In other words, the counter punch 40 is provided with a higher lying section of the end face 41 that in the blanking process engages the basic material 50 in the said bottom portion of the transverse segment 8 to be formed, i.e. radially inward of the said step 20 thereof. In the said third stage C of the blanking process, the oblong protrusion 42 is pressed into the thinner flat part 52 of the basic material 50, such that a depression 100 is formed therein and thus also in the said bottom portion of the transverse segment 8 to be formed. Although such depression 100 of the transverse segment 8 by itself need not serve any particular functional purpose in the drive belt 3, by its creation in the blanking process prior to the cutting stage D, the basic material 50 is held firmly in place relative to the counter punch 40 in such cutting stage D. Moreover, pressure is exerted by the blanking punch 30 and the counter punch 40 on the basic material 50 favourably also in the bottom portion of the transverse segment 8 to be formed, i.e. in addition to the pressure exerted at its rocking edge 18 and in its head part 15.

Preferably, the oblong protrusion 42 of the counter punch 40 extends over the full, local width dimension thereof and thus also of the transverse segment 8 to be formed, such that the depression 100 created thereby extends over the full, local width of the body part 13 of the transverse segment 8. The transverse segment 8 obtained with this first embodiment of the blanking process according to the present disclosure is schematically illustrated in figure 7.

In figures 6 and 7 the oblong protrusion 42 of the counter punch 40 and thus the depression 100 of the transverse segment 8 is separated from, i.e. does not overlap or coincide with the bottom edge 23 of the transverse segment 8. However, in an alternative, second possible embodiment of the blanking process according to the present disclosure, the oblong protrusion 42 is provided at an edge of the counter punch 40, coinciding with the bottom edge 23 of the transverse segment 8. This particular embodiment of the novel blanking process is illustrated in figure 8, whereas the transverse segment 8 obtained therewith is schematically illustrated in two embodiments thereof in figures 9 and 10.

In this latter case, an additional step 101 is formed in the bottom portion of the transverse segment 8 by the oblong protrusion 42 in the blanking process. Radially inward of such additional step 101 the depression 100 extends to the bottom edge 23 of the transverse segment 8. By such depression 100 extending to the bottom edge 23 of the transverse segment 8, the abutting transverse segments 8 in the drive belt 3 are able to tilt relative to one another to a further degree than without such depression 100, improving the flexibility of the drive belt 3 as a whole.

As illustrated in figure 9, the said step 101 that forms the radial outward extend of the depression 100 is shaped as a single continuous surface that does thus not intersect the bottom edge 23 of the transverse segment 8. However, depending on the shape of such bottom edge 23, the said step 101 can also be formed in two or more separate parts 101a, 101b, as shown in figure 10. In this case, also the depression 100 is broken up in multiple parts 100a, 100b.

In summary, the present disclosure thus concerns a method for blanking a transverse segment (1) from a basic material (50) that is pre-formed with two flat parts (51, 52) of constant, but mutually different thickness, whereof a thicker part (51) corresponds with a radially outermost part of the transverse segment (8) and whereof the thinner part (52) corresponds with a radially innermost part of the transverse segment (8) . In particular according to the present disclosure, a counter punch (40) is applied in the blanking method with an end face (41) that is provided with a protrusion (42), extending in the width direction of the transverse segment (8) and engaging the thinner part (52) of the basic material (50) . Before the transverse segment (8) is actually cut from the basic material (50), the protrusion (42) of the counter punch (40) is pressed into the basic material (50), thus forming a depression (100) therein. The present disclosure, in addition to the entirety of the preceding description and all details of the accompanying figures, also concerns and includes all of 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 respective features. The claimed features can be applied separately in a given product or a given process, as the case may be, but can also be applied simultaneously therein in 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, in particular those that lie within reach of the person skilled in the relevant art .