WO2013098653A1

WO2013098653A1 - Drive belt for a continuously variable transmission comprising two types of transverse members having a mutually different width

Info

Publication number: WO2013098653A1
Application number: PCT/IB2012/003103
Authority: WO
Inventors: Francis Maria Antonius Van Der Sluis; Joost Johannes Cornelis Jonkers; Dirk Johannes DE KUYPER; Arie VAN DER VELDE; Elena Loredana Deladi; Irinel Cosmin Faraon; Ingmarus Geert Hupkes
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-12-30
Filing date: 2012-12-27
Publication date: 2013-07-04
Anticipated expiration: 2014-06-30
Also published as: CN104024687B; NL1039276C2; JP6257524B2; JP2015503716A; CN104024687A; IN2014CN04880A

Abstract

The invention relates to a drive belt (3) including an endless carrier (31) and a plurality of transverse members (30) that are mounted on and arranged along the circumference of the carrier (31) in an essentially contiguous row. This type of drive belt (3) is well-known, in particular from its application in the friction-type belt-and-pulleys transmission. According to the invention, the efficiency of such a transmission is improved when not all transverse members (30) of the drive belt (3) take part in the frictional contact with the transmission pulleys (1, 2). This technical effect is realized, in accordance with the invention, by providing the drive belt (3) with two types of transverse members (30), whereof the second type is less wide than the first type.

Description

DRIVE BELT FOR A CONTINUOUSLY VARIABLE TRANSMISSION COMPRISING TWO TYPES OF TRANSVERSE MEMBERS HAVING A MUTUALLY DIFFERENT WIDTH The present invention relates to a drive belt for a continuously variable transmission, which is in particular destined to be arranged around two pulleys of the transmission and which comprises a plurality of discrete transverse elements or members for contacting the transmission pulleys, as well as one or more endless carriers for carrying the transverse members for supporting and guiding the transverse members in between the pulleys. The present type of drive belt is also known as a push belt.

Each endless carrier of the drive belt is typically composed of a plurality of mutually nested, continuous flexible metal bands and is also known as a ring set. Each endless carrier is at least partly inserted in a recess provided in the transverse members. In case the drive belt comprises only one endless carrier, such carrier is typically mounted in a central recess of the transverse members that opens towards the radial outside of the drive belt. However, usually the drive belt is provided with at least two endless carriers that are each mounted in a respective one of two recesses of the transverse members, which recesses then open towards a respective lateral or axial side of the transverse members, i.e. of the drive belt.

The transverse members of the drive belt are slidingly arranged along the circumference of the endless carrier or carriers in a virtually continuous row, such that these members are able to transmit forces which are related to a movement of the drive belt. The transverse members have two main body surfaces which, at least partly, extend substantially parallel with respect to each other and which are separated from each other over the (local) thickness of the transverse member. The transverse members are relatively thin, such that a several hundreds thereof are present in the drive belt, allowing the belt to curve along its circumference by the mutual relative rotation of subsequent transverse members. The transverse members are intended for frictionally contacting the transmission pulleys by being clamped widthwise between two conical sheaves of such pulleys. The transverse members arrive in such friction contact through predominantly axially, i.e. widthwise, oriented side faces thereof, which side faces are corrugated to accommodate transmission oil that is applied in the transmission to lubricate the friction contact.

The friction contact between the transverse members and the pulley sheaves allows a force to be transmitted there between, such that the drive belt can transfer a drive torque and rotational movement from one transmission pulley to the other. Such transfer mechanical power by friction is inevitably associated with energy loss due to elastic deformation of parts in the said friction contact and/or because heat is generated therein. In this latter respect, it is suggested in the prior, non-pre-published, Dutch patent application 1038910 to apply both wide, i.e. pulley sheave contacting, and narrow, i.e. non-contacting, transverse members in one drive belt. As a result only a part of the plurality of transverse members of the drive belt will actually be clamped between the pulley sheaves and the said energy loss is reduced. Hence, the efficiency of the torque transmission by this latter drive belt design is improved relative to the known drive belt with transverse members of equal width.

In relation to the above drive belt design, it is recognized that it opens up several possibilities for advantageous design changes of the transverse members of different axial dimension or width, mainly with the aim of reducing the manufacturing cost of the drive belt as whole.

In a first embodiment of the drive belt according to the invention, only the wider transverse members are provided with the said corrugated side faces. The narrower transverse members are thus shaped without such corrugation. Such a non- corrugated, i.e. smooth surface can be formed in manufacturing more easily, and typically also more cost effectively, as compared to a corrugated surface.

In a second embodiment of the drive belt according to the invention, the narrower transverse members are also lower, i.e. have a smaller radial dimension, than the wider transverse members. In particular, the narrower transverse members extend to a lesser extent radial inward from the said recess thereof as compared to the wider transverse members. In this way, favorably less material is used in manufacturing and favorably less weight is incorporated in the drive belt.

In a first elaboration of the second embodiment of the drive belt according to the invention, the wider transverse members are provided with a predominantly constant thickness along, essentially, the entire radial dimension thereof. Such transverse members of constant thickness can be formed relatively easily and cost effectively in manufacturing.

In this respect it is noted that conventional transverse members include a tapered bottom part, typically thinning from below the recess thereof and extending in radially inward direction. The thus created transition between an upper part of the transverse member of, at least comparatively, constant thickness and the tapered bottom part thereof is normally shaped as a convexly curved part of a main body surface of such transverse member and is often referred to as the tilting edge thereof. The tilting edge allows the adjacent transverse members in the drive belt to tilt relative to one another, such that the drive belt can follow a curved trajectory, while still remaining in a firm and well-defined mutual contact that is, moreover, located close the endless carrier in the radial direction to minimize efficiency loss due to the friction between the endless carrier and the transverse members.

In this first elaboration of the second embodiment according to the invention, the wider transverse members being in rolling contact with a bottom edge of the narrower transverse members between the main body surfaces and a radially inwardly facing bottom surface thereof. For enhancing such design of the drive belt, in particular for minimizing wear, the said bottom edges of the narrower transverse members are preferably, smoothly convexly rounded for example according to a radius of curvature of 6 mm or more.

Also in a third embodiment of the drive belt according to the invention, the wider transverse members are provided with a predominantly constant thickness along, essentially, the entire radial dimension thereof. However in this embodiment the narrower transverse members are provided with a tilting edge on either side thereof, i.e. on both main body surfaces thereof, for enabling the said relative tilting. In this third embodiment the design and manufacturing of the wider transverse members can be favorably focused on and optimized for the friction contact with the transmission pulleys, whereas the design and manufacturing of the narrower transverse members can be favorably focused on and optimized for the tilting contact with the wider transverse members in the drive belt.

In a fourth embodiment of the drive belt according to the invention, the narrower and the wider transverse members are made, at least in part, from mutually different materials. In this way, the material can be favorably optimized between the transverse members, for example in relation to the respective functions thereof or in terms of cost.

In a first elaboration of the fourth embodiment of the drive belt according to the invention, the wider transverse members are made, at least in part, from a more wear resistant material as compared to the narrower transverse members, for example by including therein a nitrided surface layer or by having a coating of wear resistant material.

In a second elaboration of the fourth embodiment of the drive belt according to the invention, the wider transverse members are made from a material providing a higher coefficient of friction as compared to the narrower transverse members, for example by the latter, i.e. more narrow transverse members having a low friction coating.

In a third elaboration of the fourth embodiment of the drive belt according to the invention, the narrower transverse members are made from a material providing a higher coefficient of thermal expansion as compared to the wider transverse members to compensate for wear and/or plastic deformation during operation of the drive belt.

In a fourth elaboration of the fourth embodiment of the drive belt according to the invention, the narrower transverse members are made from a lighter material compared to the wider transverse members. Since the narrower members are not clamped widthwise between the sheaves, these transverse members are loaded to a lesser extent than the wider transverse members. As a result, a weaker material that is typically also lighter may be used for the narrower transverse member as compared to that used for the wider transverse member.

In a fifth embodiment of the drive belt according to the invention, the narrower transverse members are either thicker or thinner than the wider transverse members. In this way, the number and distribution of the wider, i.e. pulley sheave contacting, and the narrower, i.e. non pulley sheave contacting, transverse members can be optimized. For example, to reduce cost, it may be opted to apply narrower transverse members that are thicker than the wider transverse members. Alternatively, if the narrower transverse members of the drive belt are thinner than the wider transverse members thereof, the most robust drive belt design can be realized. Moreover, by including narrower transverse members of varying thickness in the drive belt, the noise that is being produced during operation of the drive can be favorably reduced.

The invention will be explained in more detail on the basis of the following description of the invention with reference to the drawing and in relation to a preferred embodiment thereof. In the drawing figures equal reference signs indicate equal or similar structures and/or parts.

Figure 1 provides a schematic perspective view of the continuously variable transmission with a drive belt running over two pulleys.

Figure 2 is a schematic illustration of a part of the known drive belt, which includes two sets of a number of flexible rings, as well as a plurality of transverse members.

Figure 3 provides a schematic top-view of a section of a particular design of the drive belt.

Figure 4 provides a schematic front view of a first embodiment of the drive belt according to the invention.

Figure 5 provides a schematic front view of a second embodiment of the drive belt according to the invention.

Figure 6 provides a schematic side view of the second embodiment of the drive belt according to the invention. Figure 7 provides a schematic side view of a third embodiment of the drive belt according to the invention.

Figure 8 provides a schematic side view of a fourth embodiment of the drive belt according to the invention.

Figure 9 provides a schematic side view of a fifth embodiment of the drive belt according to the invention.

The schematic illustration of a continuously variable transmission (CVT) in Figure 1 shows a drive belt 3 which is wrapped around two pulleys 1 and 2 and which includes two separate endless carriers 31, as well as a plurality of transverse members 30 that are mounted on and arranged along the circumference of these carriers 31 in an essentially contiguous row. When it is clamped between the two conical pulley sheaves 4, 5 of the pulleys 1, 2, the drive belt 3 is able to transmit a torque "T" and an accompanying rotational movement "ω" between these pulleys 1, 2 to the other 2, 1. At the same time, the running radii R of the drive belt 3 between the sheaves 4, 5 of the respective pulleys 1, 2 determine the (speed) ratio "i" of the CVT, i.e. the ratio between the rotational speeds of the respective pulleys 1, 2. This CVT and its principal operation are known per se.

The drive belt 3 is shown in more detail in a top-view thereof in figure 2 along a section of three transverse members 30 thereof. In this figure 2 it is shown that the endless carriers 31 are each made up of a set of mutually nested, flat and flexible rings 32. The transverse members 30 of the drive belt 3 are arranged in mutual succession along the circumference of the carriers 31, in such manner that they can slide relative to and in the circumference direction of the carriers 31. The transverse members 30 take-up a clamping force exerted between the sheaves 4, 5 of each pulley 1, 2 via pulley contact faces 33 that are provided on either axial side thereof. These pulley contact faces 33 are mutually diverging in radial outward direction to essentially match a V-angle defined between the two sheaves 4, 5 of each pulley 1, 2. A so-called tilting edge 34 represents the transition between a radially outer part of the transverse member 30 of constant thickness and a tapered radial inner part thereof. This shape and tilting edge 34 of the transverse members 30 is what allows the drive belt 3 to follow a smoothly curved trajectory.

Hereinafter, the term "width W" is used in relation to the transverse member 30 and indicates the largest axial distance between the pulley contact faces 33 thereof. In the known drive belt 3, all transverse members 30 thereof are provided with essentially the same width W dimension. In fact, such width W is controlled according to a very narrow tolerance between the said transverse members 30 of the drive belt 3 to equalize the mechanical load exerted on the transverse members 30 during operation.

Such as is illustrated in figure 3, in a schematic top or radially inwardly oriented view thereof, the drive belt 3 may include both wider transverse members 30-1 that have a width W| that take-up the clamping force exerted between the sheaves 4, 5 of each pulley 1, 2 through the pulley contact faces 33 thereof, and more narrow transverse members 30-11 that have a width W_n and that do not, at least not drivingly or frictionally, engage the pulley sheaves 4, 5. The axial sides of the relatively narrow transverse members 30-11 are referred to merely as side faces 35. With this latter particular design of the drive belt 3 the efficiency of the power transmission by the CVT could be improved relative to the more conventional design thereof of figure 2 including only transverse members 30 of substantially identical width.

The drive belt design of figure 3 opens up several possibilities for further optimization, in particular in terms of the reducing the manufacturing cost of the drive belt 3 as whole.

A first possible embodiment of the drive belt 3 according to the invention is illustrated in figure 4. In this figure 4 a front view is provided of the left half of a relatively narrow transverse member 30-11 as it is placed in front of a relatively wide transverse member 30-1. in this first embodiment, only the axial side face 33, i.e. the said pulley contact faces 33 of the wider transverse member 30-1 is provided with a corrugation 36. The corresponding side face 35 of the narrower transverse member 30-11 being shaped as an, at least comparatively, smooth surface.

A second possible embodiment of the drive belt 3 according to the invention is illustrated in figure 5. In this figure 5 a front view is provided of the left half of a relatively narrow transverse member 30-11 as it is placed in front of a relatively wide transverse member 30-1. In this second embodiment, the narrower transverse member 30-11 are lower in the vertical direction of figure 5, i.e. have a smaller radial dimension, than the wider transverse members 30-1 such that it extends to a lesser extent in radially inward direction from the carrier 31, i.e. from the carrier receiving recess 37 of such narrower transverse member 30-11, as compared to such radial extent of the wider transverse member 30-1. This second possible embodiment is further illustrated in figure 6 in a side view of row of five such transverse members 30, 30-1, 30-11.

A third possible embodiment of the drive belt 3 according to the invention is illustrated in figure 7. In this figure 7 a side view is provided of row of five transverse members 30, 30-1, 30-11. In this third embodiment, in addition to the narrower transverse members 30-11 being lower than the wider transverse members 30-1 in conformance with the said second possible embodiment, the wider transverse members 30-1 are additionally provided with a predominantly constant thickness along the entire radial extent thereof. Thus the wider transverse members 30-1 do not include the above-mentioned tilting edge 34, in stead the narrower transverse members 30-11 each include two tilting edges 34, one provided on either main body surface thereof.

A fourth possible embodiment of the drive belt 3 according to the invention is illustrated in figure 8. In this figure 8 a side view is provided of row of five transverse members 30, 30-1, 30-11. In this fourth embodiment, in addition to the narrower transverse members 30-11 being lower than the wider transverse members 30-1 in conformance with the said second possible embodiment, both the wider transverse members 30-1 and the narrower transverse members 30-11 are additionally provided with a predominantly constant thickness along the entire radial extent thereof. In this embodiment the bottom edges 38 of the narrower transverse members 30-11 allow a rolling contact between the adjacent transverse members 30 in the drive belt 3.

A fifth possible embodiment of the drive belt 3 according to the invention is illustrated in figure 9. In this figure 9 a side view is provided of row of five transverse members 30-1, 30-11. In this fifth embodiment, in addition to the narrower transverse members 30-11 being lower than the wider transverse members 30-1 in conformance with the said second possible embodiment, both thicker and thinner variants of the transverse members 30-11 are provided in the drive belt 3.

It will be clear to a person skilled in the art that the scope of the present invention is not limited to the examples discussed above, but that several amendments and modification thereof are possible without deviating from the scope of the invention as defined in the appended claims.

Claims

1. Drive belt (3) with an endless carrier (31) and a number of transverse members (30) mounted slidable on the endless carrier (31) each with two main body surfaces where between the transverse member (30) extends in thickness direction and with a recess wherein the endless carrier (31) is inserted, of which transverse members (30) at least two types (I, II) with a mutually differing shape are contained in the drive belt (3), whereof an axial dimension or largest width (W,) of a first type (30-1) of the transverse members (30) is larger than a largest width (Wn) of a second type (30-11) of the transverse members (30) and whereof the transverse members (30) of the first type (30-1), on either axial side thereof, are provided with corrugated side faces (33) destined for frictional contact with pulley sheaves (4, 5) of a continuously variable transmission and which transverse members (30) of the second type (30-11) on either axial side thereof are provided with, at least comparatively, smooth side faces (35).

2. Drive belt (3) with an endless carrier (31) and a number of transverse members (30) mounted slidable on the endless carrier (31) each with two main body surfaces where between the transverse member (30) extends in thickness direction and with a recess wherein the endless carrier (31) is inserted, of which transverse members (30) at least two types (I, II) with a mutually differing shape are contained in the drive belt (3), whereof an axial dimension or largest width (W|) of a first type (30-1) of the transverse members (30) is larger than a largest width (Wn) of a second type (30-11) of the transverse members (30) and whereof the transverse members (30) of the second type (30-11) have a radial dimension that is smaller than a corresponding radial dimension of the transverse members (30) of the first type (30-1).

3. The drive belt (3) according to claim 2, whereof the transverse members (30) of the second type (30-11) extend to a lesser extent radial inward from the said recess thereof as compared to the transverse members (30) of the first type (30-1).

4. The drive belt (3) according to claim 3, whereof the transverse members (30) of the first type (30-1) are provided with an, at least predominantly, constant dimension in the thickness direction along, at least predominantly, the entire surface are of the main body surfaces thereof.

5. The drive belt (3) according to claim 4, whereof a radially innermost bottom part of the transverse members (30) of the second type (30-11) on either side thereof is provided with a curved edge (38) having a radius of curvature of 6 mm or more.

6. The drive belt (3) according to claim 4, whereof the transverse members (30) of the second type (30-11) taper inwards in radial direction below the recess, with a convexly curved part (34), or tilting edge (34) being provided in the both of the main body surfaces of the transverse members (30) concerned.

7. Drive belt (3) with an endless carrier (31) and a number of transverse members (30) mounted slidable on the endless carrier (31), each with two main body surfaces where between the transverse member (30) extends in thickness direction and with a recess wherein the endless carrier (31) is inserted, of which transverse members (30) at least two types (I, II) with a mutually differing shape are contained in the drive belt (3), whereof an axial dimension or largest width (W|) of a first type (30-1) of the transverse members (30) is larger than a largest width (W_n) of a second type (30-11) of the transverse members (30) and whereof transverse members (30) of the first type (30-1) are made from a different material than the transverse members (30) of the second type (30-11).

8. The drive belt (3) according to claim 7, whereof the transverse members (30) of the first type (30-1) are made from a more wear resistant material than the transverse members (30) of the second type (30-11).

9. The drive belt (3) according to claim 7 or 8, whereof the transverse members (30) of the first type (30-1) are made from a material providing a higher coefficient of friction in a friction contact than that of the transverse members (30) of the second type (30-11).

10. The drive belt (3) according to claim 7, 8 or 9, whereof the transverse members (30) of the second type (30-11) are made from a material with a higher coefficient of (thermal) expansion than that of the transverse members (30) of the first type (30-1).

11. The drive belt (3) according to claim 7, 8, 9 or 10, whereof the transverse members (30) of the second type (30-11) are made from a material with a lower specific weight than that of the transverse members (30) of the first type (30-1).

12. Drive belt (3) with an endless carrier (31) and a number of transverse members (30) mounted slidable on the endless carrier (31), each with two main body surfaces where between the transverse member (30) extends in thickness direction and with a recess wherein the endless carrier (31) is inserted, of which transverse members (30) at least two types (I, II) with a mutually differing shape are contained in the drive belt (3), whereof an axial dimension or largest width (W,) of a first type (30-1) of the transverse members (30) is larger than a largest width (W_M) of a second type (30-11) of the transverse members (30) and whereof the transverse members (30) of the second type (30-11) are provided with either a smaller or a larger dimension in the thickness direction than the transverse members (30) of the first type (30-1).

13. The drive belt (3) according to claim 12, whereof the transverse members (30) of the first type (30-1) are provided with mutually similar dimensions in the thickness direction.

14. The drive belt (3) according to claim 12 or 13, whereof the transverse members (30) of the first type (30-1) are provided with an, at least predominantly, constant dimension in the thickness direction along, at least predominantly, the entire surface are of the main body surfaces thereof