KR20190104553A - Drive belt for continuously variable transmission with transverse segments and ring stack - Google Patents

Abstract

The present invention relates to a drive belt 6 for a belt-and-pull type continuously variable transmission comprising a row of transverse segments 10 mounted on a stack 9 of several mutually overlapping rings. The lateral segment 10 is provided with a projection 40 protruding from its front face 11 and a corresponding hole 41 provided in its rear face 12. An offset is provided between the protrusion 40 and the hole 41 in the radial direction R of the drive belt 6, so that in the row of the transverse segments 10 of the drive belt 6, the transverse segments are provided with a protrusion ( 40 will be tilted forward by forcing insertion into the hole 41.

Description

Drive belt for continuously variable transmission with transverse segments and ring stack

The present disclosure relates to a drive belt for a continuously variable transmission having two pulleys and a drive belt. Such drive belts are known from WO2015 / 063132-A1 and comprise several mutually overlapping continuous bands, ie rows of transverse segments each mounted on a stack of flat and thin rings. The transverse segments define slots for receiving and constraining each circumferential section of the ring stack while allowing the transverse segments to move along the circumference of the ring stack. This particular type of drive belt is also referred to as a push type drive belt or push belt.

In the description below, the axial, radial and circumferential directions are defined for the drive belt when positioned in a circular attitude. In addition, the thickness dimension of the transverse segment is defined in the circumferential direction of the drive belt, the height dimension of the transverse segment is defined in the radial direction, and the width dimension of the transverse segment is defined in the axial direction.

Known transverse segments each comprise a base part, a middle part and an upper part. The middle portion of the transverse segment extends radially to interconnect the base portion and the upper portion. On both sides of the middle part, the transverse segments define a slot between the base part and the upper part for receiving each ring stack of the drive belt. In each slot, the radially outwardly bottom surface contacts and supports the ring stack radially outwardly. These bottom surfaces of the slots associated with the base portions of the transverse segments are referred to as support surfaces below.

In the row of transverse segments of the drive belt, at least a part of the front main body surface of the transverse segment abuts at least a part of the rear main body surface of the preceding transverse segment, respectively, in the row, while the rear main body of the transverse segment At least a portion of the surface abuts at least a portion of the front main body surface of the trailing lateral segment, respectively. At least one of these front and rear main body surfaces of the transverse segment, for example the front main body surface, includes an axially extending and convexly curved surface portion. This curved surface portion divides the front main body surface into radially outer surface portions and radially inner surface portions oriented at an angle with respect to each other. The abutting transverse segments of the drive belt can be tilted relative to one another and thus remain in contact with each other at and through the curved surface portion, which is then indicated by the tilting edge. The tilting edge causes the row of lateral segments of the drive belt to follow the local curvature of the ring stack imparted by the transmission pulley.

The transverse segment is further provided with protrusions projecting from the front main body surface and corresponding holes provided in the rear main body surface. In the row of transverse segments of the drive belt, the projections of the trailing transverse segments are at least partially located in the openings of the preceding transverse segments such that mutual displacement of the transverse segments abuts in a plane perpendicular to the circumferential direction of the drive belt. Is prevented or at least limited. Typically, the protrusions and holes have a similar overall shape, for example mainly cylindrical or slightly conical.

As described above, in the drive belt, the transverse segments can be moved relative to the ring stack along its circumference. This has the advantage that during operation of the drive belt, the ring stack is tensioned to a relatively low level with respect to the torque transmitted by the drive belt between the pulleys, at least compared to other types of drive belts. On the other hand, however, it is known that the sliding motion or slip between the transverse segment and the ring stack is small but leads to a conceptual frictional loss. It is known that such sliding motion can be minimized by preferably placing the tilting edge of the transverse segment as close as possible to the radial inside of the ring stack in the height direction. In theory, in this connection, the tilting edge is preferably arranged to coincide with the supporting surface of the transverse segment in question.

However, according to the present disclosure, positioning the tilting edge close to the support surface creates a problem or disadvantage that can be understood as follows. The closer the tilting edge is to the support surface, the sharper the transition edge in between. In turn, sharper transition edges result in higher contact stresses in the ring stack. Indeed, even such a high contact stress may result in exceeding the yield stress of the radially innermost ring of the ring package during operation of the drive belt, thereby impairing the service life of the innermost ring.

Surprisingly, according to the present disclosure, the disadvantage is the inclusion of an offset in the vertical direction between the projections and the holes of the individual transverse segments, in particular by positioning the holes slightly lower than the projections, ie towards the radially inner side of the drive belt. Can be mitigated. By this measure, even when moving straightly between pulleys, the transverse segments will be tilted forward in the row of drive belts because the projections are forced into the holes (below). Thus, in particular, contact between the radially interior of the ring stack and the transition edge between the support surface and the tilting edge is preferably avoided or at least reduced in strength.

Looking back, it can be observed that in conventional drive belts, the measure will not have a significant effect since the transition edge is smoothly rounded to a relatively large radius of curvature and is enabled by a relatively large separation between the support surface and the tilting edge. . For example, in a conventional drive belt, the tilting edge is about 1 mm away from the support surface such that the radius of curvature of the transition edge can be at least 0.5 mm.

In particular, the radial inward offset (O) of the holes relative to the protrusions of the individual transverse segments according to the present disclosure can be geometrically quantified as follows:

[Equation 1]

Where O_min represents the minimum value of the offset O, Rr_min represents the minimum radius of the longitudinal curvature of the drive belt, in particular in the transmission pulley, and D represents the thickness of the transverse segment.

By the minimum offset O_min according to Equation 1, the transverse segment of the drive belt is characterized by the fact that the transition edge lies with respect to the radial inside of the imaginary circle of radius Rr_min and the edge between the support surface and the rear main body surface. Tilt forward on the drive belt to the extent that they cross.

For example, for a typical drive belt with an Rr_min value of 30 mm and a D value of 1.6 mm, a minimum offset O_min of 11 micrometers is calculated using Equation 1. The actual design value for the offset O which allows some production spreads and other uncertainties is 1.5-5 times or 15-75 microns of O_min. Preferably, according to the present disclosure, the offset O so applied and thus the forward tilting of the transverse segment imparted by it is limited to five times, more preferably three times, the minimum required value O_min. . Otherwise, the alignment force between the protrusions will be unnecessarily high and / or the ring stack will be forced into contact with the rear edge of the support surface instead.

Now, the novel drive belt described above will be further described with reference to the drawings wherein like reference numerals refer to like or similar parts:
1 provides a schematic perspective view of a continuously variable transmission having a drive belt operating on two pulleys;
2 provides a schematic cross section of a known drive belt circumferentially oriented;
3 provides a schematic width-wise orientation of a transverse segment of a known drive belt;
4 is an enlarged view of a portion of the known transverse segment shown in FIG. 3;
5 is an enlarged view of a portion of the novel transverse segment; And
6 schematically shows a straight track part of a drive belt comprising a new transverse segment.

1 schematically shows a continuously variable transmission, such as for use in an automobile between a prime mover and its drive wheels. The continuously variable transmission is indicated by the numeral 1 as a whole. The continuously variable transmission 1 includes two pulleys 2 and 3 and a drive belt 6 provided as a closed loop around the pulleys 2 and 3. The pulleys 2, 3 are provided with a pulley shaft axis 4 and two pulley sheaves 7, 8, respectively, wherein the first pulley sheave 7 of the two pulley sheaves is formed of each pulley 2, 3. It is fixed to the pulley shaft 4, and the second pulley sheave 8 is axially displaceable with respect to such pulley shaft 4, while it is fixed with respect to the pulley shaft in the rotational direction. During operation of the transmission 1, the drive belt 6 is clamped by each pulley sheave 7, 8 and between the pulley sheaves to the operating radius Rr at each pulley 2, 3, which operation The radius Rr can be changed to change the speed ratio of the transmission by moving the pulley sheaves 7, 8 of the pulleys 2, 3 away from each other, respectively.

The drive belt 6 comprises two sets of mutually radially stacked continuous bands or rings, hereinafter referred to as the ring stack 9. The transverse segments 10 of the drive belt 6 are arranged on the ring stack 9 to form essentially continuous rows along the entire circumference. For simplicity, only some of these transverse segments 10 are shown in FIG. 1.

The transverse segment 10 is provided movably with respect to the ring stack 9 at least along the circumference. As a result, the transmission pulley (by the transverse segment 10) is torqued by friction and against each other and pushes each other forward along the circumference of the ring stack 9 in the rotational direction of the pulleys 2, 3 ( Can be passed between 2, 3). The transverse segments 10 of the drive belt 6 and the rings of the ring stack 9 are typically made of steel. This particular type of transmission 1 and its main operation are well known per se.

In FIG. 2, an exemplary embodiment of the drive belt 6 is oriented in length or circumferential direction C, ie perpendicular to the width or axial direction A and the height or radial direction R of the drive belt 6. It is shown in cross section. In FIG. 3, only the lateral segment 10 of FIG. 2 is shown in side view in the axial direction A. In FIG.

In FIG. 2, the ring stack 9 is shown in cross section and one transverse segment 10 of the drive belt 6 is shown in front. In this case, the ring stack 9 consists of five individual flat and thin flexible endless rings 5, each endless ring 5 in radial direction R to form the respective ring stack 9. Are stacked concentrically with each other. In practice, however, these ring stacks 9 often comprise more than five, for example nine or twelve or possibly even more endless rings 5.

In FIGS. 2 and 3, the transverse segment 10 is arranged in a radial direction (R) with a base part 13 mainly in the shape of a trapezoid, a relatively narrow middle part 14, and a top part 15 in a mainly triangular shape. It is shown to include). On both sides of the intermediate portion 14, a slot 33 is defined between the base portion 13 and the upper portion 15, and the ring stack 9 is accommodated in the slot. In each slot 33, the radially outwardly supporting surface 42 of the base portion 13 contacts the radially inner side of each ring stack 9 during operation.

The front face of the transverse segment 10 is indicated generally by the reference numeral 11, while the rear face of the transverse segment 10 is indicated generally by the reference numeral 12. In the following, the front face 11 and the rear face 12 are collectively represented by the main body surfaces 11, 12. In the drive belt 6, at least a portion of the front face 11 of the lateral segment 10 abuts at least a portion of the rear face 12 of the trailing lateral segment 10, while the lateral segment 10 At least a portion of the rear face 12 of the abuts at least a portion of the front face 11 of the preceding transverse segment 10.

The transverse segment 10 continues the clamping force exerted between the disks 7, 8 of each pulley 2, 3 through its contact surface 37, and one such contact surface 37 is the transverse segment. On each axial side of 10. These contact surfaces 37 have a radius such that the acute angle represented by the belt angle φ is defined therebetween and closely matches the pulley angle θ defined between the pulley sheaves 7, 8 of the pulleys 2, 3. They diverge from one another outward.

The transverse segment 10 is provided with a projection 40 protruding from its front face 11 and a corresponding hole 41 provided in its rear face 12. In the drive belt 3, the projection 40 of the trailing transverse segment 10 is at least partially located in the hole 41 of the preceding transverse segment 10, so that the circumferential direction C of the drive belt 3 is achieved. The mutual displacement of these adjacent transverse segments 10 in a plane perpendicular to is prevented or at least limited. Typically a nominal clearance of 10 to 50 microns is provided between the outer circumference of the protrusion 40 and the inner circumference of the hole 41, ie between the protrusion / hole-clearance.

A rocking edge 18 is formed in the front face 11 of the base portion 13 of the transverse segment 10. The rocking edge 18 is represented by a convexly curved region of the front face 11, which region separates the two sections of the front face 11 in the radial direction R, the two sections being from each other. Oriented at an angle relative to. An important function of the oscillating edge 18 is to establish mutual pushing contact between adjacent transverse segments 10 when adjacent transverse segments are in a slightly rotated, ie tilted position with respect to each other in the pulleys 2, 3. To provide. In order to advantageously realize the minimum contact stress in the pushing contact as well as for the stability of such contact, the swing edge 18 preferably extends along the entire local width of the transverse segment 10. The swinging edge 18 is preferably located at a minimum distance Drc close to the support surface 42, ie radially inward thereof. However, the smaller this distance Drc, the sharper the transition edge 50 between the front face 11 and the support surface 42 of the transverse segment 10 will be. This latter aspect of the design of the transverse segment 10 is shown in FIG. 4, which is an enlarged view of the area E of FIG. On the left side of FIG. 4, a relatively large radius of curvature at the transition edge 50, compared to the design of the transverse segment 10 on the right side of FIG. 4 with at least relatively small swinging edge-to-ground distance Drc. A relatively large rocking edge-to-earth ground distance Drc is shown that allows Rte to be provided. In practice and as shown in FIG. 4, the radius of curvature Rte is the oscillating edge-to-earth distance Drc to reliably ensure in mass production that the oscillating edge 18 does not overlap with the transition edge 50. Slightly smaller than)

In FIG. 4, the transition edge 50 is shown as an arc of radius Rte. In practice, however, the transition edge 50 may not be so uniformly shaped, in which case the contour is approximated by an arc of radius R (closest fit), at least within the context of the present disclosure. do. As such, the transition edge radius Rte between the support surface 42 and the front surface 11 may seem insignificant. However, this transition edge 50 actually contacts the radial interior of each ring stack 9 to raise its overall stress level. Particularly in view of the latter, it has been found that a substantial stress raising effect occurs when the radius Rte of the transition edge 50 is less than 0.5 mm, in particular less than 0.3 mm.

According to the present disclosure, this contact between the transition edge 50 and the ring stack 9 is offset between the radial position of the projection 40 and the radial position of the hole 41 of the transverse segment 10. By providing O) it is preferably avoided or the strength can be reduced at least. Thus, by lowering the overall stress level of the ring stack 9, the load bearing capacity and / or life of the drive belt 3 can be increased.

This novel design of the transverse segment 10 is schematically illustrated in FIG. 5 in an enlarged view of a portion thereof, in part in relation to the transverse segment 10 in the region F indicated by the dotted oval in FIG. 3. Corresponds. In FIG. 5, the central axis of the cylindrical protrusion 40 is indicated by the solid line CA40 and the central axis of the hole 41 is indicated by the dotted line CA41. Thus, the offset O corresponds to the separation between the central axis CA40 of the cylindrical protrusion 40 and the central axis CA41 of the hole 41. According to the present disclosure, this offset O amounts to about 15 to 75 micrometers when the typical thickness of the transverse segment 10 is 1.4 to 1.8 mm. Therefore, even in the scale of FIG. 5, the offset O is exaggerated.

If the offset O incorporated in the novel transverse segment 10 exceeds the nominal protrusion / hole-clearance, then the transverse segments 10 are first transverse when pressed together in a row of drive belts 3. The protrusion 40 of the directional segment 10 is forcibly tilted forward with respect to the ring stack 9 by forcibly being inserted into the hole 41 (below) of the adjacent transverse segment 10. Thereby, as schematically shown in FIG. 6, the contact between the radially interior of each ring stack 9 and the transition edge 50 of the transverse segment 10 is between the transmission pulleys 2, 3. It can preferably be avoided in the straight section of the drive belt 3 traversing. In addition, the transverse segment 10 also enters between two pulley sheaves 7, 8 at such a tilted position with respect to the ring stack 9, with each transverse clamped between the pulley sheaves 7, 8. The radial position of the transition edge 50 of the directional segment 10 is slightly smaller than the radial position of the opposite edge of the support surface 42 on the rear face 12 side of the lateral segment 10. Thereby, the contact between the radially interior of each ring stack 9 and the transition edge 50 between the support surface and the tilting edge is at least preferably reduced in strength.

The present disclosure relates to and encompasses all features of the appended claims, in addition to all the details of the foregoing description and all the details of the accompanying drawings. Reference numerals enclosed in parentheses in the claims do not limit the scope, and are provided merely as a non-limiting example of each feature. The claimed features may be applied individually in a given product or given process, but in some cases, it is also possible to apply any combination of two or more of those features.

The present invention (s) represented by the present disclosure is not limited to the examples and / or examples expressly mentioned herein, but include corrections, modifications and practical applications, in particular within the scope of those skilled in the art. do.

Claims (8)

A transverse segment 10 for a drive belt 6 having a ring stack 9 and a plurality of consecutive transverse segments 10 movably disposed on the ring stack 9 and transverse segments 10. ) Comprises an opening 33 for receiving the ring stack 9 of the drive belt 6, the opening 33 of which is at the lower side the top of the base portion 13 of the transverse segment 10. Delimited by the support surface 42 at the side, the base portion 13 also extends over the width of the base portion 13 of the transverse segment 1 in the front face 11 of the transverse segment 10. A rocking edge 18 in the form of a convexly curved region of the and a similarly convexly curved transition edge 50 between the support surface 42 and the front surface 11 of the transverse segment 10, The transverse segment 10 further comprises a projection 40 on its front face 11 and a hole 41 in its rear face 12 positioned opposite the front face 11. , In the lateral segment,
The protrusions 40 and the holes 41 are mainly conical or at least cylindrically shaped, with an offset O between the central axis CA40 of the protrusions 40 and the central axis CA41 of the holes 41. Transverse segment (10), characterized in that is provided. Transverse segment (10) according to claim 1, characterized in that the radius of curvature (Rte) of the curved transition edge (50) is smaller than 0.5 mm, in particular smaller than 0.3 mm. 3. The swinging edge 18 according to claim 1 or 2, which is located below 0.9 mm of the support surface 42, in particular below 0.7 mm of the support surface, more particularly 0.6 mm of the support surface. Transverse segment (10), characterized in that located below less than. 4. Transverse segment (10) according to claim 1, 2 or 3, characterized in that the offset (O) amounts to 15 to 75 micrometers. The transverse segment (10) according to claim 4, characterized in that a clearance is formed between the outer circumference of the protrusion (40) and the inner circumference of the hole (41), the clearance reaching between 10 and 50 micrometers. Transverse segment (10) according to claim 5, characterized in that the offset (O) is greater than half of the difference between the diameter of the outer circumference of the protrusion (40) and the diameter of the inner circumference of the hole (41). In a drive belt 6 comprising a plurality of transverse segments 10 according to claim 6, the offset O applied to these transverse segments 10 is given by the following equation:

Greater than its minimum value (O_min),
Rr_min represents the minimum radius of the longitudinal curvature of the drive belt 6, and D represents the maximum thickness of the transverse segment 10 measured between the front face 11 and the rear face 12, Drive belt (6). The drive belt (6) according to claim 7, characterized in that the offset (O) applied to these transverse segments (10) is less than 5 times and preferably less than 3 times its minimum value (O_min).

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