EP2798236A1

EP2798236A1 - Drive belt for a continuously variable transmission with transverse members provided with contact areas

Info

Publication number: EP2798236A1
Application number: EP11808174.4A
Authority: EP
Inventors: Cornells Johannes Maria VAN DER MEER
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-12-30
Filing date: 2011-12-30
Publication date: 2014-11-05
Also published as: WO2013097884A1; JP5921713B2; JP2015503713A

Abstract

A generally C-shaped transverse member (32) for a drive belt (3) defines a centrally located recess (33) that is open towards an axial side thereof. The transverse member (32) includes a base part (34) located below the recess (33), a connecting part (35) located in line with the recess (33) and a top part (36) located above the recess (33), and which transverse member (32) is provided with a tilting edge (18) forming a transition between a top section and a tapered bottom section of the transverse member (32). A main face (39) of the transverse member (32) is provided with at least two contact areas (50, 60) that are raised relative to other parts of that main face (39) and whereof a lower contact area (50) is located above the tilting edge (18) in the said base part (34) and whereof an upper contact area (60) is located in the said top part (36).

Description

DRIVE BELT FOR A CONTINUOUSLY VARIABLE TRANSMISSION WITH TRANSVERSE MEMBERS PROVIDED WITH CONTACT AREAS

The present invention relates to a drive belt for a continuously variable transmission having two pulleys, each having two pulley sheaves with an at least partially conical surface for wedging-in the drive belt. The known drive belt comprises an endless carrier that is composed of a set of nested, flexible metal rings and a number of transverse members that together form an essentially continuous row along the circumference of the endless carrier and that each define a recess that opens towards an axial or lateral side of the drive belt and wherein the endless carrier is located. Such a drive belt with generally C-shaped transverse members is known from, for example, the European patent publication No. EP-A-0 014 013, in particular figure 1 thereof. The known transverse member includes a base part lying radially inward from or below the recess, a connecting part lying on the axially closed side of the recess and a top part lying radially outside or above the recess. On a front main face of the transverse member, in the base part thereof, a so-called tilting edge is provided that forms a transition between a radially outer or head section and a tapered radially inner or bottom section of the transverse member. Such tapered bottom section and tilting edge allow adjacent transverse members in the drive belt to mutually tilt in a curved trajectory part of the drive belt in the transmission.

Further, on a main face of the transverse member a projection is provided, which projection is inserted in a hole provided in the opposite main face of an adjoining transverse member in the drive belt. Such projection and hole thus serve to mutually align the transverse members in the row of transverse members. Moreover, on both axial sides of the base part the transverse element is provided with pulley contact faces for contacting a pulley sheave surface for producing a frictional contact with the pulleys.

During operation of the drive belt in the transmission the transverse members push each other along the circumference of the endless carrier from a driven pulley to a driving pulley of the transmission. Hereby, the front main face of a respectively succeeding transverse member is in contact with the rear main face of a respectively preceding transverse member, exerting a pushing force on such preceding transverse member in the process. In the known transverse member the entire head section takes part in such pushing contact.

During such operation, vibrations occur in the drive belt, i.e. in the trajectory part thereof that spans from the driving pulley to the driven pulley, which vibrations are disadvantageous in that noise and/or mechanical stress is generated thereby.

According to the invention, by providing an accurately defined contact between the transverse members in the said trajectory part of the drive belt, the vibrations can be favourably reduced. More in particular according to the invention, the said contact between the transverse members is realised through at least two contact areas, which areas are part of a main face of the transverse member. Moreover, one such contact area is located in the base part of each transverse member, radially outward from the tilting edge, and a second contact area is located in the top part of each transverse member close to an upper side thereof. Put alternatively, according to the invention, a radial separation between the said two contact areas is to be maximised, at least within the constraints dictated by the geometry and the manufacturing process of the transverse member.

The contact areas in accordance with the invention protrude relative to other parts of the main face concerned (i.e. those parts surrounding the contact areas) . At these contact areas the thickness of the transverse member is thus greater than at the location of the said other parts of the main face concerned. However, such greater thickness is small in absolute terms and will typically be in the order of magnitude of between a minimum of five to ten and a maximum of around a hundred micrometres. Further, for reasons well-known in the art of drive belt design, as represented by EP-A- 1 061 285 in particular, the thickness at the contact area in the top part of the transverse member is preferably somewhat greater than at the contact area located in the base part thereof.

In an elaboration of the invention, the surface area of the contact area in the top part of the transverse member is equal to or larger than the surface area of the contact area in the base part of the transverse member .

In a further elaboration of the invention, the said two contact areas each extend to the axial sides of the transverse member.

In yet a further elaboration of the invention, the said contact area located in the base part of the transverse member is composed of two parts, each such respective contact area part being located towards a respective axial side of the transverse member. In particular, these two contact area parts in the base part are mutually separated at an axial position corresponding to the axial position of the closed side of the recess. More in particular, the projection and hole are provided in between these two contact area parts in the base part. Preferably, in this case, a radial position of the projection overlaps, at least in part, with that of the tilting edge, which tilting edge is thus locally interrupted thereby.

Preferably also, one part contact area part in the base part is located below the recess and extends over a major part, preferably over the whole, of the axial extent thereof. In yet a further elaboration of the invention, also the said contact area located in the top part of the transverse member is composed of two parts, each such respective contact area part likewise being located towards a respective axial side of the transverse member.

All of the above described, increasingly more detailed technical measures in accordance with the invention directly or indirectly contribute to a certain extent to improving the stability of the drive belt in said trajectory part thereof.

The present invention is based on the technical insight that without the said defined contact areas, relatively high lying, i.e. projecting areas will occur randomly in each transverse member of the drive belt. As a result a point of (initial) contact between the transverse members varies randomly along the circumference of the drive belt and the abovementioned, detrimental vibrations can easily occur. However, by using the measure (s) according to the invention, it is ensured in a relatively simple and reliable manner that the contact between the transverse members is in principle uniform throughout the drive belt.

The invention will now be explained by way of example on the basis of the description below with reference to the drawing, in which:

figure 1 is a perspective view of a partially cutaway transmission with a pulleys and a drive belt; figure 2 is a front view of a generally C-shaped transverse member of the drive belt, which shows the contours of a main face thereof;

figure 3 shows a side view of the transverse element of figure 2;

figure 4 shows the known transverse member of figure 2 incorporated in the drive belt;

figure 5 shows a first embodiment of a generally C- shaped transverse member according to the present invention;

figure 6 shows a second embodiment of a generally C- shaped transverse member according to the present invention; and

figure 7 shows a third embodiment of a generally C- shaped transverse member according to the present invention;

Figure 1 diagrammatically shows the central parts of a continuously variable transmission for the drive of, for example, passenger motor vehicles. This transmission is known per se and comprises at least a first and a second drive wheel, or pulley 1, 2 and a drive belt 3 accommodated between the conical sheaves 4,. 5 of the pulleys 1 and 2. At least one sheave 4 of each pulley 1, 2 is axially movable over a respective pulley shaft 6, 7. For this purpose, electronically controllable and hydraulically acting movement means are generally accommodated in the transmission, which means are not shown in the figures. The activation of these movement means leads to an axial movement of the moveable sheaves 4 and, consequently, to an adjustment of the radial positions R of the drive belt 3 between the sheaves 4, 5 of the pulleys 1, 2. The driving force of a pulley 1, 2 is transmitted by means of friction in the contact between the pulley sheaves 4, 5 and the drive belt 3.

The known drive belt 3 is composed of an endless carrier 31 and a number of transverse members 32 that are mounted on the carrier 31 in an essentially contiguous row along the circumference thereof. The transverse members 32 are accommodated in the drive belt 3 so as to be freely movable along the circumference of the drive belt 3.

Figures 2 provides a close-up of the transverse member 32, looking in the circumferential direction L of the drive belt 3, and figure 3 provides a side view of the transverse member 32, looking from the right to the left of figure 2.

The known transverse member 32 is shaped similar to the letter "C", i.e. is generally C-shaped. The known transverse member 32 defines a centrally located recess 33 that is open towards one axial side of the transverse member 32. The known transverse member 32 thus includes three main parts 34, 35, 36, whereof a first or base part 34 lies below or inward from the recess 33 in the radial direction R, whereof a second or connecting part 35 lies in line with the recess 33 in the axial direction A and whereof a third or top part 36 lies radially outward from the recess 33. In the drive belt 3, the endless carrier 31 is located in the said recess 33.

On either axial end thereof, the base part 34 is provided with a pulley contact face 37 for producing the friction contact with the pulley sheaves 4, 5. These pulley contact faces 37 of the transverse member 32 are mutually oriented at an angle φ that corresponds to an angle φ that is defined between the conical sheaves 4, 5 of the pulleys 1, 2 (figure 1) .

On a front main face 39 of the transverse member 32, in the base part 34 thereof, a so-called tilting edge 18 is provided that forms a transition between a radially outer or head section and a tapered radially inner or bottom section of the transverse member 32. Such tilting edge 18 and tapered bottom section allow the transverse members 32 in the drive belt 3 to mutually tilt in a curved trajectory part of the drive belt 3 in the transmission .

Further on the front main face 39 of the transverse member 32, however in the top part 36 thereof, a projection 40 is provided. In the drive belt 3 the projection 40 is inserted in a hole 41 provided in the opposite, i.e. rear main face 38 of an adjoining transverse member 32. Such projection 40 and hole 41 serve to mutually align the transverse members 32 in the said row of transverse members 32.

Finally, in figure 4, a cross-section of the known transmission is shown. The drive belt 3 is shown to be wedged between the (marginally indicated) pulley sheaves 4, 5. It is shown that the consecutive transverse members 32', 32" of the drive belt 3 are (axially) mirrored, that is to say that the recesses 33 of such consecutive transverse members 32', 32" open towards mutually opposite axial sides of the drive belt 3. In figure 4, the rear lying transverse member 32" is indicated with the dashed lines where is lies behind the front lying transverse member 32'. As a result of such arrangement of the transverse members 32, 32', 32", the endless carrier 31 thereof is completely confined in the plane of figure 4, i.e. in the axial and radial directions A, R of the drive belt 3.

Also in figure 4, the typical construction of the endless carrier 31 is shown, that includes a number of radially nested rings.

In figure 5 the present invention is schematically illustrated in a first embodiment thereof. In this first embodiment of the invention the front main face 39 of the transverse member 32 is designed with two so-called contact areas 50 and 60 that are indicated by the hatchings and that are raised relative to the remaining, other parts of the front main face 39. In other words, at the location of the contact areas 50, 60 the thickness of the transverse member 32, i.e. the separation or distance between its front main face 39 and its rear main face 38, is greater than outside these areas 50, 60.

In accordance with the invention a lower contact area 50 is provided in the base part 34 of the transverse member 32, i.e. below the recess 33 defined thereby, however, still above the tilting edge 18 thereof. The other, i.e. upper contact area 60 is provided in the top part 36 of the transverse member 32 near the radially upper side thereof. Both the said two contact areas 50, 60 extend over the full axial dimension of the transverse member 32. Moreover, in accordance with the invention, a surface area of the upper contact area 60 is at least equal to a surface area of the lower contact area 50.

In the drive belt 3, the transverse member 32 makes contact, at least initially, with a preceding transverse member at the location of the contact areas 50, 60 thereof. According to the invention, such precisely defined and specifically positioned contact areas 50, 60 provides a stable contact between the consecutive transverse members 32, 32', 32" of the drive belt 3 and vibrations are favourably suppressed.

In practice, the said greater thickness at the contact areas 50, 60 can be limited to several tens of micrometres, which is small compared to a nominal thickness of the transverse element 32 of around 1.5 mm. Further in practice, the borders of the contact areas 50, 60 need not be sharply defined, but may be formed as a gradually slope. According to the definition applied now, those parts of the front main face 39 that lie less than 10 micrometres below a highest point of a contact area 50, 60 concerned, are considered to be part of the respective contact area 50, 60.

In figure 7 the present invention is schematically illustrated in a third embodiment thereof. Also in this third embodiment of the invention both the upper contact area 60 is composed of two separate parts 60a, 60b and the lower contact area 50 is composed of two separate parts 50a, 50b. Each such contact area part 50a, 50b, 60a, 60b being located towards a respective axial side of the transverse member 32. The contact area parts 50a, 50b in the base part 34 are mutually separated at an axial position corresponding to the axial position of the closed side of the recess 33. Moreover, the projection 40 and hole (not shown) are not provided in the top part 36 of the transverse member 32, but in the base part 34 in-between the said contact area parts 50a, 50b. In accordance with the invention, the projection 40 in the base part 34 is provided with a predominantly rectangular shape and overlaps, at least in the radial direction and at least in part, with the tilting edge 18. Naturally, the hole (not shown) is provided with a shape that can accommodate such rectangular projection in the base part 34, overlapping with the tilting edge 18.

Claims

1. Transverse member (32) for a drive belt (3) for use in a continuously variable transmission such as for passenger motor vehicles with two drive wheels (1, 2) where between the drive belt (3) is accommodated, which transverse member (32) is generally C-shaped and defines a centrally located recess (33) that is open towards one axial side thereof, which transverse member (32) includes a base part (34) located below the recess (33), a connecting part (35) located in line with the recess (33) and a top part (36) located above the recess (33), and which transverse member (32) is provided with a tilting edge (18) forming a transition between a top section and a tapered bottom section of the transverse member (32), characterised in that, a main face (39) of the transverse member (32) is provided with at least two contact areas (50, 60) that are raised relative to other parts of that main face (39) and whereof a lower contact area (50) is located above the tilting edge (18) in the said base part (34) and whereof an upper contact area (60) is located in the said top part (36) close to an upper side of the transverse member (32).

2. The transverse member (32) according to claim 1, characterised in that, a surface area of the upper contact area (60) is equal or larger than a surface area of the lower contact area (50) .

3. The transverse member (32) according to claim 1 or

2, characterised in that, the lower contact area (50) and the upper contact area (60) extend to the axial sides of the transverse member (32).

4. The transverse member (32) according to one of the preceding claims, characterised in that, the upper contact area (60) is composed of two parts (60a, 60b) that are each located at a respective axial side of the transverse member (32) .

5. The transverse member (32) according to one of the preceding claims, characterised in that, the lower contact area (50) is composed of two parts (50a, 50b) that are each located at a respective axial side of the transverse member (32).

6. The transverse member (32) according to claim 5, characterised in that, the said two parts (50a, 50b) of the lower contact area (50) are mutually separated at an axial position corresponding to an axially closed side of the recess (33) .

7. The transverse member (32) according to claim 6, characterised in that, in-between the said two parts (50a, 50b) of the lower contact area (50) is provided with a projection (40) that is intended to be accommodate in a recess (41) provided in an opposite main face (38) of a preceding transverse member (32) in the drive belt (3) .

8. The transverse member (32) according to claim 7, characterised in that, the projection (40) is of a predominantly rectangular shape and is positioned, in part, in line with tilting edge (18) that is locally interrupted thereby.

9. The transverse member (32) according to claim 6, 7 or 8, characterised in that, one part (50b) of the lower contact area (50) is located below the recess (33) and extends over a major part, preferably over the whole, of the axial extent thereof.

10. The transverse member (32) according to any one of the preceding claims, characterised in that, the said contact areas (50, 60) and/or contact area parts (50b, 60, 60a, 60b) protrude between 5 and 100 microns relative to other parts of the main face concerned (39) .

11. Drive belt (3) including an endless carrier (31) and a number of transverse elements (32) according to one of the preceding claims, wherein the endless carrier (31) is accommodated in the recesses (33) of the transverse members (32) such that the base part (34) of the transverse members (32) is located on the radial inside of the endless carrier (31) .