CN108223692B

CN108223692B - Drive belt with transverse component and ring set for a continuously variable transmission and method for producing the same

Info

Publication number: CN108223692B
Application number: CN201711400858.7A
Authority: CN
Inventors: C·J·M·万德米尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-12-22
Filing date: 2017-12-22
Publication date: 2021-06-29
Anticipated expiration: 2037-12-22
Also published as: JP7078390B2; CN108223692A; JP2018112312A; NL1042192B1

Abstract

The invention relates to a drive belt (6) for a pulley-type continuously variable transmission, comprising a row of transverse members (10) mounted on a set (9) of a plurality of mutually nested, continuous rings (5), the radially outwardly facing bearing surfaces (42) of the transverse members (10) supporting the set (9) of rings during operation. According to the invention, transverse members (10) of different widths are included in the drive belt (6), and the maximum variation in the width of the transverse members meets specified criteria.

Description

Drive belt with transverse component and ring set for a continuously variable transmission and method for producing the same

Technical Field

The present disclosure relates to a drive belt for a continuously variable transmission having two pulleys and a drive belt. Such a drive belt is known from international patent application publication WO2015/063132-a1 and comprises a row of transverse members each mounted on a set of a plurality of mutually nested continuous belts, i.e. flat and thin rings. The transverse members define slots for receiving and restraining respective circumferential segments of the ring sets while enabling the transverse members to move along the circumference of the ring sets. This particular type of drive belt is also known as a push belt or push belt. The present disclosure also relates to a method for manufacturing a power transmission belt of either design.

Background

In the following description, the axial, radial and circumferential directions are defined with respect to the situation when the drive belt is placed in a circular manner. Furthermore, the thickness dimension of the transverse members is defined in the circumferential direction of the drive belt, the height dimension of the transverse members is defined in said radial direction and the width dimension of the transverse members is defined in said axial direction.

The existing transverse members each comprise a base portion, a middle portion and a top portion. The intermediate portion of the transverse element extends in radial direction, thereby interconnecting said base and top portions of the transverse element. On either side of the intermediate portion, the transverse member defines a slot between its base and top portions for receiving a respective set of rings of the drive belt. At each groove, its radially outward bottom surface contacts and supports the ring sets in a radially outward direction. These bottom surfaces of the groove associated with the base portion of the transverse member are referred to hereinafter as load bearing surfaces.

In a row of transverse members of the drive belt, at least a part of the front body surface of a transverse member abuts against at least a part of the rear body surface of a respective preceding transverse member in the row, and at least a part of the rear body surface of a transverse member abuts against at least a part of the front body surface of a respective subsequent transverse member. At least one of these front and rear body surfaces of the transverse member, for example the front body surface, comprises an axially extending convexly curved surface portion. The curved surface portion divides the front body surface into a radially outer surface portion and a radially inner surface portion oriented at an angle relative to each other. The abutting transverse members in the drive belt can be tilted relative to each other while keeping in mutual contact at and by such curved surface portions, which are thus referred to hereinafter as tilting edges. The beveled edges cause the rows of transverse members of the drive belt to follow the local curve of the set of rings imposed by the drive pulley.

As described above, in the transmission belt, the transverse member is movable relative to the ring sets in the circumferential direction thereof. This has the advantage that during operation of the drive belt, the sets of rings are tensioned to a relatively low level with respect to the torque transmitted between the pulleys through the drive belt, at least in comparison with other types of drive belts. However, on the other hand, such sliding movement or slippage between the transverse members and the ring sets is known to result in small, but substantial frictional losses. It is known that such sliding movements can advantageously be minimized by arranging the inclined edges of the transverse members as close as possible in the height direction to the radially inner side of the set of rings. In this respect, in principle, the oblique edge is preferably arranged to coincide with the bearing surface of the transverse element in question.

In practice, the beveled edge is typically disposed at a distance of about 1mm radially inward of the bearing surface. However, especially by using a specific manufacturing process in the manufacture of the transverse members, said distance may be reduced to 0.9mm to 0.6mm or even less, for example as taught by WO2015/063132-a 1.

The above-mentioned design aspects of the transverse elements and their efficiency-improving effect have been examined and proven in practice. However, in some, but not all cases, these tests also showed a small, but substantially undesirable, reduction in the service life of the overall drive belt, a phenomenon that was neither expected nor understood.

Disclosure of Invention

The present disclosure aims to improve the service life of the drive belt, in particular of a drive belt comprising transverse members, wherein the bevelled edge is located at a position within 0.9mm, more in particular within 0.6mm, radially inwards of the bearing surface.

According to the present disclosure, such an improvement can surprisingly be achieved by controlling the deviation of the width dimension of said base portions of the transverse members of the drive belt, in particular by controlling such a width deviation with respect to the radius of curvature of the transition edges between the bearing surfaces and the body surfaces of these transverse members.

According to the idea on which the present disclosure is based, the radial position of the individual transverse members of the drive belt at the drive pulley is determined by their width. The radial position of the bearing surface of the individual transverse elements is therefore also determined by their width. Thus, the bearing surface of the wider transverse member of a pair of abutting transverse members projects radially outwardly relative to the bearing surface of the other narrower transverse member of the pair. Thus, the ring set is not only in contact with these bearing surfaces, but is also curved around the transition edge between at least the bearing surface and the main body surface of the wider transverse part. This contact between the transition edge and the radially inner side of the ring set increases the ring stress level, especially if the transition edge is a relatively sharp edge. In fact, the yield stress of the radially innermost ring of the ring set may even be exceeded, thereby affecting the service life of the innermost ring.

In view of the above phenomenon, it may now be concluded that this is not critical in the known drive belt, since the transition edges of its transverse members are smoothly rounded with a relatively large radius of curvature, in particular with respect to the usual width variations of these transverse members produced in series. However, as the distance between the bearing surface and the inclined edge decreases, the radius of curvature of the transition edge must also decrease.

More particularly, according to the present disclosure, the following empirically derived relationship approximates the maximum width deviation Δ Wm in millimeters permitted between each pair of abutting transverse members in the drive belt, and the radius of curvature Rte in millimeters of the transition edge between its load bearing surface and the body surface, Rte:

ΔWm<0.005*e^(10*Rte) (1)

wherein "e" represents a natural logarithmic base.

For existing belts having a distance between the slanted edge and the bearing surface structure of about 1mm, the radius of curvature Rte of the transition edge may be 0.5mm or more, giving a maximum width deviation Δ Wm of 0.742mm according to equation (1). This latter value is easy to achieve within the accuracy of the commonly employed manufacturing process of cutting out transverse members from strip material by (fine) blanking, followed by deburring and quench hardening, so that the above-mentioned phenomenon does not really occur in existing drive belts. However, for example, to achieve a preferred location of the beveled edge 0.7-0.4mm radially inward of the bearing surface, once the curvature Rte of the transition edge is reduced to 0.3mm or less, the maximum width deviation Δ Wm drops to 0.1mm or less, which is critical to achieving with the commonly employed manufacturing processes.

The above-described novel design requirements according to the present disclosure may in principle be achieved by improving the accuracy of the blanking process, the polishing process and/or the quench hardening process. However, this may not be economical or indeed even feasible. Alternatively, the present disclosure proposes: (a) measuring the width W of the cross-member prior to mounting the cross-member on the ring set; and (b) selecting only those transverse components for mounting on the ring set that meet specified criteria with respect to such width. Such a specified criterion may be, for example, the width range that each transverse member of the drive belt has to meet. Alternatively or additionally, a maximum width deviation may be defined for each successive transverse member mounted on the ring set with respect to an abutting, i.e. previously mounted, transverse member in the row of transverse members of the drive belt.

Drawings

The above described drive belt and method of manufacturing the same will now be further explained with reference to the drawings, in which like reference numerals designate identical or similar parts, and in which:

figure 1 provides a schematic perspective view of a continuously variable transmission with a drive belt running on two pulleys;

figure 2 provides a schematic cross-sectional view of a prior art drive belt in its circumferential orientation;

figure 3 provides a schematic width-oriented view of the transverse members of the known drive belt;

figure 4 is an enlarged view of the corresponding part of the transverse element shown in figure 3;

figure 5 is a schematic view of a transverse member clamped between two sheaves of a pulley;

figure 6 schematically shows a curved track portion of the drive belt; and

fig. 7 provides a diagram in which the model ring stress σ r is plotted against the maximum width deviation Δ Wm between the transverse members 10 of the drive belt 6.

Detailed Description

Fig. 1 schematically shows a continuously variable transmission, such as is used in motor vehicles between its main engine and drive wheels. A continuously variable transmission is generally indicated by reference numeral 1. The continuously variable transmission 1 comprises two

pulleys

2, 3 and a drive belt 6, which drive belt 6 is arranged in a closed loop around the

pulleys

2, 3. The

belt pulleys

2, 3 are provided with a pulley shaft 4 and two pulley sheaves 7, 8, respectively, wherein the first pulley sheave 7 is fixed on the pulley shaft 4 of the

respective belt pulley

2, 3 and the second pulley sheave 8 is axially movable relative to this pulley shaft 4 while being fixed in the direction of rotation. During operation of the transmission 1, the drive belt 6 is clamped at each

pulley

2, 3 at a running radius R by and between the respective pulley sheaves 7, 8, which running radius R can be changed by moving the pulley sheaves 7, 8 of the

pulleys

2, 3 towards and away from each other, respectively, in order to change the speed ratio of the transmission.

The drive belt 6 comprises two sets of continuous belts or rings, hereinafter referred to as ring sets 9, nested radially one inside the other. The transverse members 10 of the drive belt 6 are arranged on the sets of rings 9 so as to form a substantially continuous row along their entire circumference, of which transverse members 10 only a part is shown in figure 1 for the sake of simplicity.

The lateral member 10 is provided to be movable relative to the ring set 9 at least along the circumferential direction of the ring set 9. Thus, torque can be transmitted between the transmission pulleys 2, 3 by means of friction and by the transverse members 10 pressing against each other and pushing each other forward in the circumferential direction of the ring sets 9 in the direction of rotation of the

pulleys

2, 3. The transverse members 10 of the drive belt 6 and (the rings of) the ring sets 9 are typically made of steel. This particular type of transmission 1 and its main operation are known per se.

In fig. 2, an exemplary embodiment of the drive belt 6 is shown in a sectional view which is oriented in its length direction or circumferential direction C, i.e. perpendicular to the width direction or axial direction a and the height direction or radial direction R of the drive belt 6. In fig. 3, only a side view in the axial direction a of the transverse part 10 of fig. 2 is shown.

In fig. 2, the ring sets 9 are shown in a sectional view and one transverse part 10 of the drive belt 6 is shown in a front view. The ring sets 9 consist in this case of five separate flat, thin and flexible annular rings 5, which annular rings 5 are nested concentrically in the radial direction R with respect to one another to form a respective ring set 9. However, in practice, these ring sets 9 typically comprise more than five annular rings 5, for example nine or twelve, or possibly even more annular rings 5.

In fig. 2 and 3, the transverse member 10 is shown to comprise, in succession in a radial direction R, a substantially trapezoidal base portion 13, a relatively narrow intermediate portion 14 and a substantially triangular top portion 15. A slot 33 is defined between the base portion 13 and the top portion 15 on either side of the intermediate portion 14, the ring assembly 9 being received in the slot 33. At each groove 33, a radially outwardly facing bearing surface 42 of the base portion 13 contacts the radially inner side of the respective ring set 9 during operation.

The front surface of the transverse member 10 is generally indicated by reference numeral 11 and the rear surface of the transverse member 10 is generally indicated by reference numeral 12. Hereinafter, the front surface 11 and the rear surface 12 are generally referred to as body surfaces 11, 12. In the drive belt 6, at least a part of the front surface 11 of a transverse member 10 abuts against at least a part of the rear surface 12 of a subsequent transverse member 10, while at least a part 10 of the rear surface 12 of a transverse member 10 abuts against at least a part of the front surface 11 of a preceding transverse member 10.

The transverse member 10 is subjected to a clamping force exerted between the discs 7, 8 of each

pulley

2, 3 via its contact surface 37, one such contact surface 37 being provided at each axial side of the transverse member 10. These contact surfaces 37 are mutually divergent in the radially outward direction so as to define an acute angle therebetween, referred to as the belt angle Φ, closely matching the pulley angle θ defined between the pulley sheaves 7, 8 of the

pulleys

2, 3.

The cross member 10 is provided with a protrusion 40 protruding from its front surface 11 and with a corresponding hole 41 provided in its rear surface 12. In the drive belt 6, the projection 40 of the trailing transverse member 10 is at least partly located in the hole 41 of the leading transverse member 10, so that mutual displacement of these adjacent transverse members 10 in a plane perpendicular to the circumferential direction C of the drive belt 6 is prevented or at least limited.

In the base part 13 of the transverse part 10 at the front surface 11 a rocking edge 18 is defined. The rocking edge 18 is embodied by a convexly curved region of the front surface 11, which separates in the radial direction R two portions of said front surface 11, which are oriented at an angle with respect to each other. An important function of the rocking edge 18 is to provide a mutual pushing contact between adjacent transverse members 10 when said transverse members 10 are in a slightly rotated, i.e. inclined, position relative to each other at the

pulleys

2, 3. In order to advantageously achieve a minimum contact stress in said pressing contact and for stability of such contact, the rocking edge 18 preferably extends along the entire local width of the transverse member 10. It is within the scope of the present disclosure that the width W of the cross member 10 is defined at the rocking edge 18.

The rocking edge 18 is preferably located close to the bearing surface 42, i.e. at a minimum distance dr radially inwards thereof. However, the smaller this distance Drc, the sharper the transition edge 50 between the front surface 11 and the bearing surface 42 of the transverse member 10 will be. This latter aspect of the design of the transverse member 10 is shown in fig. 4 in an enlarged view of the area E indicated by the dashed circle in fig. 3. At least in comparison to the design of the transverse member 10 on the right side of fig. 4 with a relatively small rocking edge-bearing surface distance Drc, a relatively large rocking edge-bearing surface distance Drc is shown on the left side of fig. 4, so that the transition edge 50 is provided with a relatively large radius of curvature Rte. In practice, as shown in fig. 4, the radius of curvature Rte is slightly smaller than the rocking edge-bearing surface distance dr c in order to reliably ensure that the rocking edge 18 does not overlap the transition edge 50 in mass production.

In fig. 4, the transition edge 50 is shown as a circular arc with a radius Rte. In practice, however, the transition edge 50 may not be so uniform in shape, in which case its profile approximates (a closest fit to) a circular arc of radius Rte, at least within the scope of the present disclosure. Thus, the transition edge radius Rte between the bearing surface 42 and the main body surfaces 11, 12 does not seem to be important. However, at least for the relatively wide transverse members 10 of the drive belt 6, this transition edge 50 does in fact come into contact with the radially inner side of the respective ring set 9, thereby increasing its overall stress level.

In an exaggerated manner, shown in fig. 5, a wider transverse element 10-b having a larger width W-b will be located at a slightly larger radial position R-b than the radial position R-a of a narrower transverse element 10 having a smaller width W-a when clamped between the pulley sheaves 7, 8. In other words, said running radius R of the conveyor belt 6 at the

pulleys

2, 3 varies slightly, in practice, between the respective transverse members 10 in relation to their respective widths W-a, W-b. The difference Δ R in the radial position R is directly related to the difference Δ W in the widths W-a, W-b:

ΔR＝1/2ΔW/tan(1/2Θ) (2)

this latter aspect is further schematically illustrated in fig. 6 by a set of seven transverse members 10, of which only the base parts 13 are shown in mutually inclined positions, so as to form curved track portions of the drive belt 6. On the left side of fig. 6, all transverse members 10 have the same width W, so that they run between the pulley sheaves 7, 8 at the same radial position R, as indicated by the dashed line. On the right side of fig. 6, said transverse members 10-a, 10-b having different widths W-a, W-b are present in the curved track portion. As can be seen in FIG. 6, in the row of transverse components 10, when the narrower transverse component 10-a is followed by the wider transverse component 10-b, as shown in phantom, the transition edge 50 of the wider transverse component 10-b impinges on the radially inner side of the ring set 9.

The overall stress level of the inner rings of the ring set 9 of the drive belt 6 has been modelled, including the stress-raising effect of the contact of such rings with the transition edge 50. Fig. 7 provides a diagram of several values of the annular stress σ r of such a model with respect to the maximum width deviation Δ Wm of the transverse member 10 occurring in the drive belt 6 and the radius of curvature Rte of the transition edge 50. Also drawn in figure 7 is a broken line representing the critical ring stress σ r-crit for designing the drive belt 6, which should not be exceeded during operation. Within the scope of the present disclosure, this critical design ring stress σ r-crit is derived by subtracting a safety margin of 10% from the yield stress of the ring. From fig. 7, the relationship according to equation (1) between the transition edge radius Rte and the maximum width deviation Δ Wm can be derived.

Based on fig. 7, equation (1), and especially when the transverse component 10 is manufactured with a relatively small radius of curvature Rte of the transition edge 50 between its body surfaces 11, 12 and the bearing surface 42, the present disclosure proposes to measure the width W of the transverse component 10 before mounting the transverse component 10 on the ring set 9, and to select only those transverse components 10 for mounting on the ring set 9 that meet a predetermined criterion with respect to their measured width W.

In addition to all of the details of the foregoing description and accompanying drawings, the present disclosure also relates to and includes all of the features of the claims. Any reference signs placed between parentheses in the claims shall not be construed as limiting the scope of the claims but shall be construed as merely providing non-limiting examples of the corresponding feature. The claimed features may be applied to a given product or a given process individually, as the case may be, but any combination of two or more of these features may be applied here.

The invention set forth in this disclosure is not limited to the embodiments and/or examples explicitly mentioned herein, but encompasses modifications, variations and practical applications of the embodiments and/or examples, especially those within the scope of availability to those skilled in the art.

Claims

1. Drive belt (6) with a ring set (9) and with a plurality of transverse members (10), which transverse members (10) are arranged successively and movably on the ring set (9), which transverse members (10) are provided with grooves (33) for receiving the ring set (9), which grooves (33) are delimited at their bottom side by a bearing surface (42) at the upper side of a base portion (13) of the respective transverse member (10), which base portion (13) is further provided with a rocking edge (18) and a transition edge (50), the rocking edge (18) being represented by a portion of a front body surface (11) of the transverse member (10) extending in the width direction over a width dimension (W) of the base portion (13) of the respective transverse member (10) and being convexly curved perpendicularly to the width direction, the transition edge (50) being located between the bearing surface (42) and the front body surface (11) of the transverse member (10), the width dimension (W) of the transverse member (10) is defined at the swing edge (18), characterized in that the dimension of the transverse member (10) of the drive belt (6) satisfies the relation:

ΔWm<0.005*e^(10*Rte) (1)，

where Rte is the mean radius of curvature of the transition edge (50) in millimeters, where e is the base of the natural logarithm and Δ Wm is the maximum difference in the width dimension (W) between all transverse members (10) of the drive belt (6).

2. Drive belt (6) according to claim 1, characterized in that the average radius of curvature Rte of the transition edges (50) of all transverse members of the drive belt (6) is equal to or less than 0.4 mm.

3. Drive belt (6) according to claim 1 or 2, characterized in that the rocking edges (18) of all transverse members of the drive belt (6) are positioned less than 0.9mm below its bearing surface (42).

4. Drive belt (6) according to claim 2, characterized in that the average radius of curvature Rte of the transition edges (50) of all transverse members of the drive belt (6) is equal to or less than 0.3 mm.

5. Drive belt (6) according to claim 2, characterized in that the average radius of curvature Rte of the transition edges (50) of all transverse members of the drive belt (6) is equal to or less than 0.2 mm.

6. Drive belt (6) according to claim 3, characterized in that the rocking edges (18) of all transverse members of the drive belt (6) are positioned less than 0.7mm below its bearing surface (42).

7. Drive belt (6) according to claim 3, characterized in that the rocking edges (18) of all transverse members of the drive belt (6) are positioned less than 0.6mm below its bearing surface (42).

8. A method for manufacturing a drive belt (6), which drive belt (6) has a ring set (9) and has a plurality of transverse members (10), which transverse members (10) are arranged successively and movably on the ring set (9), which transverse members (10) are provided with grooves (33) for receiving the ring set (9), which grooves (33) are delimited at their bottom sides by bearing surfaces (42) at the upper sides of base portions (13) of the respective transverse members (10), which base portions (13) are further provided with a rocking edge (18) and a transition edge (50), the rocking edge (18) being represented by a portion of a front body surface (11) of a transverse member (10) extending in the width direction over a width dimension (W) of the base portion (13) of the respective transverse member (10) and being convexly curved perpendicular to this width direction, a transition edge (50) being located between the bearing surface (42) and the front main body surface (11) of the transverse members (10), a width dimension (W) of the transverse members (10) being defined at the oscillation edge (18), in which method the width dimension (W) of the transverse members (10) is determined, i.e. measured, before the transverse members (10) are arranged on the ring set (9), wherein, for all transverse members (10) of the drive belt (6), only those transverse members (10) are arranged on the ring set (9) for which the difference in width dimension (W) is within a predetermined range,

wherein the predetermined range is equal to 0.005 ^ (10 ^ Rte) in millimeters, wherein Rte is the average radius of curvature of the transition edge (50) in millimeters, wherein e is the base of the natural logarithm.