NL1039276C2

NL1039276C2 - Drive belt for a continuously variable transmission comprising two types of transverse members having a mutually different width.

Info

Publication number: NL1039276C2
Application number: NL1039276A
Authority: NL
Inventors: Francis Maria Antonius Sluis; Joost Johannes Cornelis Jonkers; Dirk-Jan Kuyper; Arie Velde; Elena Loredana Deladi; Irinel Cosmin Faraon; Ingmarus Geert Hupkes
Original assignee: Bosch Gmbh Robert
Priority date: 2011-12-30
Filing date: 2011-12-30
Publication date: 2013-07-03
Also published as: CN104024687A; JP2015503716A; IN2014CN04880A; WO2013098653A1; JP6257524B2; CN104024687B

Description

DRIVE BELT FOR A CONTINUOUSLY VARIABLE TRANSMISSION COMPRISING TWO TYPES OF TRANSVERSE MEMBERS HAVING A MUTUALLY DIFFERENT WIDTH

5 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 10 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 15 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 20 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 2 5 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 30 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.

35 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 1039276 2 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, 5 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 damped 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.

10 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 15 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 20 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.

25 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.

30 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 35 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 3 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, 5 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 10 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, 15 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 2 o 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 2 5 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 30 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 35 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 4 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 5 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.

10 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 15 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.

20 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 2 5 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 30 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.

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

5

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.

5 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 10 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 "w" 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 15 sheaves 4, 5 of the respective pulleys 1, 2 determine the (speed) ratio T 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 20 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 25 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. 30 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 35 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 6 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 5 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 WM 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 10 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 15 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 20 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 25 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 30 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 35 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 7 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 5 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 10 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 15 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 20 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 25 the invention as defined in the appended claims.

1039276

Claims

1. Drive belt (3) with an endless support (31) and a number of transverse elements (30) slidably arranged on the support (31) with two main surfaces between which a transverse element (30) extends in thickness direction and with a recess in which the endless carrier (31), of which transverse elements (30) at least two types (I, II), of mutually different shape, are accommodated in the drive belt (3), an axial dimension of which is the largest transverse dimension (W |) of a first type (30-1) of the transverse elements (30) is larger than a largest transverse dimension (Wh) of a second type (30-11) of the transverse elements (30), which transverse elements (30) of the first type (30-1) in transverse direction on either side thereof are provided with corrugated contact surfaces (33) intended for frictional contact with pulley discs (4, 5) of a continuously variable transmission and which transverse elements (30) of the second type (30-11) on either side thereof are provided with flat side faces (35 ).

2. Drive belt (3) with an endless support (31) and a number of transverse elements (30) slidably arranged on the support (31) with two main surfaces between which a transverse element (30) extends in thickness direction and with a recess in which the endless support (31) and of which transverse elements (30) at least two types (I, II), of mutually different shape, are accommodated in the drive belt (3), an axial dimension of which is the largest transverse dimension (W |) of a first type (30-1) of the transverse elements (30) is larger than a largest transverse dimension (Wn) of a second type (30-11) of the transverse elements (30) and of which the transverse elements (30) of the second type (30-11) a radial dimension is smaller than a corresponding radial dimension of the transverse elements (30) of the first type (30-1).

A drive belt (3) according to claim 2, the transverse elements (30) of the second type (30-11) extending less radially below said recess thereof compared to the transverse elements (30) of the first type 30 (30-1).

4. Drive belt (3) according to claim 3, of which the transverse elements (30) of the first type (30-1) are provided with a substantially constant dimension in thickness direction over at least substantially the entire surface of the main surfaces thereof.

5. Drive belt (3) as claimed in claim 4, of which the transverse elements (30) of the second type (30-11) are provided on either side thereof in a radially defined bottom side with a curved edge with a radius of curvature of 6 mm or more . 1039276 f

A drive belt (3) according to claim 4, the transverse elements (30) of the second type (30-11) tapered radially below said recess thereof, wherein in the two main surfaces of the respective transverse elements (30) convex curved part (34), or tilting edge (34) is provided 5

7. Drive belt (3) with an endless support (31) and a number of transverse elements (30) slidably arranged on the support (31) with two main surfaces between which a transverse element (30) extends in thickness direction and with a recess in which the endless support (31), of which transverse elements (30) at least two types (I, II), of mutually different shape, are accommodated in the drive belt (3), an axial dimension of which is the largest transverse dimension (W |) of a first type (30-1) of the transverse elements (30) is larger than a largest transverse dimension (WM) of a second type (30-11) of the transverse elements (30), which transverse elements (30) of the first type (30) 30-1) are made of a different material than the transverse elements (30) of the second type (30-11).

A drive belt (3) according to claim 7, the transverse elements (30) of the first type (30-1) being made of a more wear-resistant material than the transverse elements (30) of the second type (30-11).

9. Drive belt (3) according to claim 7 or 8, of which the transverse elements (30) of the first type (30-1) are made of a material with a higher coefficient of friction in a frictional contact than the transverse elements (30) of the second type (30-11).

10. Drive belt (3) according to claim 7, 8 or 9, of which the transverse elements (30) of the second type (30-11) are made of a material with a higher (thermal) expansion coefficient than the transverse elements (30) of the first type 25 (30-1).

11. Drive belt (3) according to claim 7, 8, 9 or 10, of which the transverse elements (30) of the second type (30-11) are made of a material with a lower specific gravity than the transverse elements (30) of the first type (30-1).

12. Drive belt (3) with an endless carrier (31) and a number of transverse elements (30) slidably arranged on the carrier (31) with two main surfaces between which a transverse element (30) extends in thickness direction and with a recess in which the endless carrier (31), of which transverse elements (30) at least two types (I, II), of mutually different shape, are accommodated in the drive belt (3), an axial dimension of which is the largest transverse dimension (W |) of a first type (30-1) of the transverse elements (30) is larger than a largest transverse dimension (WM) of a second type (30-11) of the transverse elements (30), which transverse elements (30) of the second type (30-11), at least at least a part thereof, are provided with a smaller or larger dimension in thickness direction than the transverse elements (30) of the first type (30-1).

13. Drive belt (3) according to claim 12, the transverse elements (30) of the first type (30-1) having mutually corresponding dimensions in the thickness direction.

A driving belt (3) according to claim 12 or 13, the transverse elements (30) of the first type (30-1) being provided with a substantially constant dimension in the thickness direction over at least substantially the entire surface of the main surfaces thereof.