WO2012089340A1

WO2012089340A1 - A transverse element for an assembled drive belt with transverse elements and with a tension ring and an assembled drive belt

Info

Publication number: WO2012089340A1
Application number: PCT/EP2011/006587
Authority: WO
Inventors: Geert-Jan Schrauwers; Duc-Minh TRAN; Bert Pennings; Peter Verhoeven; Cornelia Adriana Elizabeth Crebolder
Original assignee: Robert Bosch Gmbh
Priority date: 2010-12-29
Filing date: 2011-12-28
Publication date: 2012-07-05
Also published as: EP2659163A1; CN103299103A; JP2014504701A; NL1038482C2

Abstract

Transverse element (13) for assembled drive belt (10) with transverse elements (13) and with a tension ring 14 that is located on a cut-out in the transverse elements (13) and that, in lateral direction can arrive into contact with a lateral side face (18) of a neck part (13b) of at least a number of the transverse elements (13) of the drive belt (10), which transverse element (13) on either lateral side of a base part (13a) thereof is provided with a contact face (23) destined to contact transmission pulleys, wherein the lateral side face (18) of the neck part (13b) of the transverse element (13) is more wear resistant than the contact faces (23) the transverse element (13).

Description

A TRANSVERSE ELEMENT FOR AN ASSEMBLED DRIVE BELT WITH TRANSVERSE ELEMENTS AND WITH A TENSION RING AND AN ASSEMBLED DRIVE BELT

The invention relates to a transverse element for assembled drive belt according to the preamble of Claim 1 hereinafter. Such a drive belt may be used for transmitting a driving power between two shafts in a drive line, whereto the drive belt is passed around two rotating pulleys and is clamped in the V-grooves as defined by the pulleys between conical pulley sheaves thereof. A generally known use of such a transmission is the continuously variable transmission for 2-wheeled motor vehicles such as scooters. The drive belt and transmission are known per se and were disclosed in, for example, the US patent with publication number 4,612,005 back in 1986.

One particular feature of this known application of the known transmission is that typically no lubricant and/or coolant agent such as oil is provided to the friction contact between the pulleys and the drive, belt. On the one hand a favorably high coefficient of friction is thus realized in the friction contact of this "dry" transmission type and, moreover, a simple construction of the transmission is achievable, in particular in comparison with an actively lubricated or "wet" transmission types. On the other hand the amount of power that can be transmitted by this dry transmission type is severely limited, as are the materials that can suitably be applied therein, in particular for the pulleys and the drive belt.

Indeed, because the pulley sheaves are typically made of metal to ensure a sufficient strength and stiffness thereof, at least that part of the drive belt that arrives in friction contact with these pulley sheaves can normally not be made of metal as well, because otherwise excessive wear would unavoidably occur in the absence of a coolant/lubricant. Although suitable coating materials could possibly be applied to the pulley sheaves, it is usually the drive belt, i.e. at least the contact faces of the so-called transverse elements thereof for contacting the pulley sheaves, that is/are made from either rubber or plastic. Typically, each entire transverse element is molded or (die) casted from such rubber or plastic, such as for example glass fiber- reinforced nylon. It is, however, also known to coat or embed a metal (e.g. aluminum) core with/in a suitable rubber, plastic or other coating material to from the transverse elements.

Further, in order to maximize the power transmitting capacity of the drive belt, it is known in the art to apply a ribbon-like, endless tension ring, i.e. which tension ring is thin in relation to its circumference length and width dimension. To realize the optimum properties for its intended drive belt application, the tension ring is preferably made from metal, in particular stainless steel.

The above-described, specific type of drive belt is known from, for instance, the European patent application publication EP-A-2 115 318. The known belt comprises one or more tension rings and of a number of the transverse elements that are arranged on and in sliding relationship with the tension ring(s). Each transverse element is provided with one or more cut-outs, each cut-out accommodating a respective tension ring in such a manner that a first or base part of the transverse element extends under or radially inward of the tension ring, a second or neck part of the transverse element is situated at the same (radial) level as the said cut-outs and a third or head part of the transverse element extends over or radially outward of the tension ring.

In practice, this specific type of drive belt functions quite well, but ultimately over time may suffer from the limitation that the tension ring can arrive in friction contact with the neck part of the transverse element as a result whereof it cuts sideways, i.e. in lateral/axial direction, into such neck part. In the end, a transverse element can even be cut into two separate parts as a result, in which case the drive belt will likely fail.

The present invention aims to overcome or at least mitigate the above problem and thus to extend the service life of the present type of drive belt. According to the invention such aim is realized by applying the technical measure as defined in the characterizing portion of the claim 1 hereinafter. Thus, according to the invention, the lateral sides of the neck part of one or more of the transverse elements are more wear resistant in relation to friction than other parts of these transverse elements, such as in particular the said (pulley) contact faces thereof, and/or in comparison with other transverse elements of the drive belt.

In a first detailed embodiment of the invention, the transverse element concerned includes a cover shield or guard separate from the main body of the transverse element, i.e. as a modular component, which cover shield forms the lateral sides of the neck part. In the transverse element according to this second embodiment of the invention the cover shield can be made from a wide range of materials such that the most suitable material for a particular drive belt and/or drive belt application can be easily selected. Particularly suitable materials are resilient and/or hard plastics, such as rubber, Teflon, thermosetting plastics in general, or thermoplastic plastics with high (glass) fiber content, or metals, such as stainless steel or aluminum.

In a second detailed embodiment of the invention, the transverse element concerned is entirely made of one such a particularly wear resistant material. Since this latter novel transverse element can otherwise be prone to accelerated deterioration and or can damage the pulley sheave surfaces, it is preferably designed such that it does not arrive into friction contact with the transmission pulleys, i.e. such that it will not be clamped between the pulley sheaves together with the other transverse elements of the drive belt having rubber or plastic interfaces to the pulley sheaves. This implies that the transverse element concerned is preferably less wide than the said other transverse elements of the drive belt. Moreover, to optimally mitigate the physical contact between the tension ring and the said other transverse elements, the neck part of the transverse element concerned is preferably wider than the neck part of the said other transverse elements.

In a third and final detailed embodiment of the invention, the transverse element concerned includes a hard core embedded in a softer coating layer, which core is exposed, i.e. is not provided with the coating, at least at the lateral sides of the neck part of such transverse element. The transverse element according to this first embodiment of the invention is comparatively easy and cheaply to manufacture simply by shielding-off the relevant surface parts thereof in the process step wherein the said coating layer is applied on/to the transverse elements. Suitable coatings and/or core materials are well known in the art. As core material relatively hard materials, such as thermosetting plastics and metals such as steel and aluminum, are typically applied in practice

Preferably, all of the transverse elements of the drive belt are provided with one or more of the above protective measures in accordance with the invention. Still, according to the invention, already a couple of such modified transverse elements will, to a large extend, prevent the tension ring from cutting into the other transverse elements, in particular when these are more or less evenly distributed along the circumference of the drive belt. Preferably, however, the number of such modified transverse elements that are applied in the drive belt, is just sufficient for realizing that at all times at least one such modified transverse element is clamped, or at least present, between the sheaves of each transmission pulley. In practical transmission designs this latter design rule requires a minimum of 5 to 10 of such modified transverse element to be incorporated in the drive belt. The required number of such modified transverse elements can thus remain very small in comparison with a total number of transverse elements that are typically included in a single drive belt of the present type, namely of 150 to 500, in order to favorably limit the (additional) cost of the novel drive belt. In other words, preferably between 1% and 7.5%, more preferably about 5% of the total number of transverse elements is modified in accordance with the invention. Moreover, it is to be preferred that such modified transverse elements are more or less evenly distributed throughout the drive belt, i.e. are provided at essentially equal mutual intervals along the circumference of the drive belt .

The invention will now be explained in greater detail with reference to the exemplary embodiments illustrated in the appended figures.

Figure 1 provides a schematically depicted example of the well-known continuously variable transmission provided with a drive belt.

Figure 2 is a cross-section of the known drive belt oriented in the belt's circumference direction, providing a front view of the known transverse element.

Figure 3 illustrates a first implementation of the invention in a perspective view of the transverse element.

Figure 4 illustrates a second implementation of the invention in a top view of a row of transverse elements.

Figure 5 illustrates a third implementation of the invention in a cross-section of the drive belt providing a front view of the transverse element.

Figure 1 shows the central parts of a known continuously variable transmission or CVT that is commonly applied in the drive line of, in particular, 2- wheeled motor vehicles between the engine and the driven wheel thereof. The transmission comprises two pulleys 11, 12, each provided with two conical pulley sheaves 15, where between a predominantly V-shaped pulley groove is defined and whereof one sheave 15 is axially moveable relative to the other sheave 15 of a respective pulley 11, 12. A drive belt 10 is wrapped around the pulleys 11, 12 for transmitting a rotational movement and an accompanying torque from the one pulley 11, 12 to the other 12, 11. The transmission generally also comprises activation means that impose on the said at least one sheave 15 an axially oriented clamping force Fax directed towards the respective other pulley sheave 15 such that the belt 10 is clamped there between. Also, a (speed) ratio of the transmission between the rotational speed of a driven pulley 12 and the rotational speed of a driving pulley 11 is determined thereby.

An example of a known drive belt 10 is shown in more detail in figure 2 in a cross-section thereof facing in the circumference direction thereof. The known belt 10 is shown to incorporate two tension rings 14. The known belt 10 further comprises a number of transverse segments or elements 13 (see also figure 1) that are held together by the tension rings 14, which tension rings 14 are each located in a respective recess or cut-out provided in the transverse elements 13.

The transverse elements 13 take-up the said clamping force exerted between the pulley sheaves 15 through respective contact faces 23 thereof, such that when an input torque is exerted on a so-called driving pulley 11, friction between the sheaves 15 and the drive belt 10, i.e. the transverse elements 13 thereof, causes a rotation of that driving pulley 11 to be transferred to a so-called driven pulley 12 via the likewise rotating drive belt 10. To allow the drive belt 10 to follow a curved trajectory on the pulleys 11, 12, the transverse elements 13 include a width-wise oriented (rocking) edge 17, where under, i.e. radially inward wherefrom, the transverse element 13 is tapered.

It was found as a limitation of the durability of this known drive belt 10 that during its operation the tension rings 14, which are typically made from a hard material for sufficient strength, can cut in a predominantly lateral or width-wise direction into a neck part 13b of the transverse elements 13 that are typically made from a softer material to limit the weight of the known belt 10, under the influence of a relative movement there between. In figure 2 this relative movement and the cutting in of the neck part 13b is indicated by the dashed horizontal arrows. The neck part 13b of the transverse elements 13 is provided in between and interconnects a base part 13a of the transverse element 13 located under the tension rings 14 and a head part 13c of the transverse element 13 located over the tension rings 14.

According to the invention, the scope of use of the known drive belt 10 can be expanded if the lateral side faces 18 of the neck part 13b of the transverse elements 13 are made from a (wear resistant) material different from that or those of the transverse element 13 itself, in particular by means of a guard or cover shield 19, 20, such as an insert or shielding guard. This first implementation of the invention is illustrated in figure 3.

In figure 3 two examples of such cover shields 19, 20 are illustrated. A first cover shield 19, which is depicted on the left side of figure 3 and which shields the left side face 18a of the neck part 13b of the transverse element 13x depicted in this figure 3, is predominantly crescent- or C-shaped in cross-section. A second, cylindrical cover shield 20 is depicted on the right side of figure 3. This second cover shield 20 is - in this particular example- shaped cylindrical and is sized to fill and fit the cut-out immediately adjacent to the (right) side face 18b of the neck part 18b.

According to the invention, the cover shields 19, 20 can be fitted in the drive belt 10 as a separable component, as well as fixed, e.g. glued, to the transverse element 13x. In particular, in a (not illustrated) preferred embodiment a single, strip shaped, guard is wrapped, i.e. folded around all four sides of the neck part 13b of the transverse element 13x.

Further according to the invention, the scope of use of the known drive belt 10 can also be expanded, if a part of the total number of transverse elements 13 in/of the drive belt 10 is entirely made from a wear resistant material. In this case and especially if a metal is used as wear resistance material, the such modified transverse elements 13y are preferably designed with a reduced lateral dimension, i.e. width, in relation to the other transverse elements 13, such that the such modified transverse elements 13y will not be clamped between the sheaves 15 of the pulleys 11, 12, as illustrated in figure 4 in a top view of a row of transverse elements 13, 13y. Moreover, in this case, the neck part 13b of the such modified transverse elements 13y are preferably designed wider than the neck part 13b of the said other transverse elements 13.

In figure 5 a third implementation of the invention is illustrated in a front view of a transverse element 13z in accordance with the invention. This third implementation departs from the known transverse element design with a metal core 21 embedded in a coating layer 22. The metal core 21 being indicated by the dashed line L, to indicate that in reality it is not exposed, but rather embedded in the coating layer 22.

According to the invention, this known design has been modified by removing the coating layer at the lateral side faces 18 of the neck part 13b of the transverse element 13z or by not coating these lateral side faces 18 in the first place. In either case, the effect is that in the drive belt 10 the metal core 21 of the transverse element is exposed at the neck part 13b of the transverse element 13z and thus forms an abutment for a (relative) lateral movement of the tension rings 14.

Claims

CONCLUSIES

1. Transverse element (13) for assembled drive belt (10) with transverse elements (13) and with a tension ring 14 that is located on a cut-out in the transverse elements (13) and that, in lateral direction, can arrive into contact with a lateral side face (18) of a neck part (13b) of at least a number of the transverse elements (13) of the drive belt (10), which transverse element (13) on either lateral side of a base part (13a) thereof is provided with a contact face (23) destined to contact transmission pulleys, characterized in that, the lateral side face (18) of the neck part (13b) of the transverse element (13) is more wear resistant than the contact faces (23) the transverse element (13).

2. Transverse element (13) according to claim 1, characterized in that, at the location of the neck part (13b) of the transverse element (13), it is provided with a cover shield (19, 20) as a separate component, i.e. is non-integrally formed with the neck part (13b).

3. Transverse element (13) according to claim 2, characterized in that, the cover shield (19, 20) is made of a resilient and/or hard plastic or a metal, in particular stainless steel or aluminum.

4. Transverse element (13) according to claim 1, characterized in that, the transverse element (13) includes a core (21) that is embedded in a coating layer (22) and in that the coating layer (22) is absent at the location of the neck part (13b), i.e. either was not applied or was removed after application.

5. Transverse element (13) according to claim 1, characterized in that, the core (21) is made of a thermosetting plastics or a metal, in particular stainless steel or aluminum.

6. Assembled drive belt (10) with transverse elements (13) and with a tension ring 14 that is located on a cutout in the transverse elements (13) and that, in lateral direction, can arrive into contact with a lateral side face (18) of a neck part (13b) of at least a number of the transverse elements (13) of the drive belt (10), which transverse element (13) on either lateral side of a base part (13a) thereof is provided with a contact face (23) destined to contact transmission pulleys, characterized in that, the drive belt (10) includes a least some and preferably exclusively transverse elements (13) according to one of the claims 1-5.

7. Assembled drive belt (10) according to claim 6, including only some transverse elements (13) according to one of the claims 1-5, characterized in that, the neck part (13b) of the elements (13) according to one of the claims 1-5 is wider than the neck part (13b) of other transverse elements (13) of the drive belt (10) .

8. Assembled drive belt (10) according to claim 6 or 7, including only some transverse elements (13) according to one of the claims 1-5, characterized in that, the base part (13a) of the elements (13) according to one of the claims 1-5 is less wide than the base part (13a) of other transverse elements (13) of the drive belt (10) .

9. Assembled drive belt (10) according to claim 6 or 7, including only some transverse elements (13) according to one of the claims 1-5, characterized in that, the transverse elements (13) according to one of the claims 1-5 make up between 1 and 5% of the total number of transverse elements (13) in the drive belt (10).

10. Assembled drive belt (10) with transverse elements (13) and with a tension ring 14 that is located on a cutout in the transverse elements (13) and that, in lateral direction, can arrive into contact with a lateral side face (18) of a neck part (13b) of at least a number of the transverse elements (13) of the drive belt (10), which transverse element (13) on either lateral side of a base part (13a) thereof is provided with a contact face (23) destined to contact transmission pulleys, characterized in that, a part of the transverse elements (13) of the drive belt (10) are made of a material that is more wear resistant than other transverse elements (13) of the drive belt (10) .

11. Assembled drive belt (10) according to claim 10, characterized in that, the neck part (13b) of the said part of the transverse elements (13) of the drive belt (10) is wider than the neck part (13b) of the said other transverse elements (13) of the drive belt (10) .

12. Assembled drive belt (10) according to claim 10 or 11, characterized in that, the base part (13a) of the said part of the transverse elements (13) of the drive belt (10) is less wide than the base part (13a) of the said other transverse elements (13) of the drive belt (10) .

13. Assembled drive belt (10) according to claim 10, 11 or 12, characterized in that, the said part of the transverse elements (13) comprises between 1 and 5% of the total number of transverse elements (13) in the drive belt (10) .