Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16G—BELTS, CABLES, OR ROPES, PREDOMINANTLY USED FOR DRIVING PURPOSES; CHAINS; FITTINGS PREDOMINANTLY USED THEREFOR
  • F16G5/00—V-belts, i.e. belts of tapered cross-section
  • F16G5/16—V-belts, i.e. belts of tapered cross-section consisting of several parts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16G—BELTS, CABLES, OR ROPES, PREDOMINANTLY USED FOR DRIVING PURPOSES; CHAINS; FITTINGS PREDOMINANTLY USED THEREFOR
  • F16G5/00—V-belts, i.e. belts of tapered cross-section
  • F16G5/16—V-belts, i.e. belts of tapered cross-section consisting of several parts
  • F16G5/163—V-belts, i.e. belts of tapered cross-section consisting of several parts with means allowing lubrication

Definitions

• the present invention relates to a drive belt for a continuously variable transmission for motor vehicles, as defined in the preamble of claim 1.
• Such a drive belt is well-known and is, for instance, described in the European patent applications EP-A-0 329 206 and EP-A-0 626 526.
• the known drive belt is composed of a plurality of transverse segments and at least one endless or ring- shaped carrier that extends through an opening or a recess of each of the segments such that these are supported thereby.
• the transverse segments are neither fixed to one another nor to the carrier ring, such that they can move relative to the carrier at least in the circumferential or length direction thereof.
• adjacent transverse segments abut one another through their respective front and back main surfaces, which main surfaces face, at least predominantly, in the said circumferential direction.
• the transverse segments and the carrier ring are made of steel.
• the carrier ring is typically composed of a number of individual bands that are narrowly fitted one around the other.
• the known transverse segment On either axial side thereof, the known transverse segment is provided with a friction surface.
• the transverse segment arrives in (frictional) contact with a driving pulley and a driven pulley of the transmission such that a rotation of the driving pulley can be transferred to the driven pulley via the likewise rotating drive belt.
• An effective thickness of the transverse segment is defined as the dimension of these friction surfaces in the said circumferential direction, i.e. the part of the friction surfaces that is directly available for the contact with the pulleys. This effective thickness is typically less than an overall thickness of the transverse segment because of, for instance, the presence of rounded or slanted transition edges between these friction surfaces and the main surfaces of the transverse segments.
• the known transverse segment is further provided with an essentially cylindrical, possibly slightly tapering, protrusion or stud on its front main surface and a, likewise essentially cylindrical indentation or hole on its back main surface.
• the stud of a first transverse segment is inserted in the hole of a second, adjacent transverse segment.
• such interaction between the stud and the hole of two adjacent transverse segments also limits a rotation of the transverse segments relative to the carrier ring, both about the axial direction of the drive belt, i.e. a pitching of the transverse segments, and about the radial direction of the drive belt, i.e. a yawing of the transverse segments.
• the known drive belt is operated in a lubricated, i.e. oiled environment, both to reduce belt-internal friction losses and to cool the belt and the pulleys of the transmission.
• the lubrication oil will, however, also enter into the holes of the transverse segments, at least in a bent part of the trajectory of the drive belt on the transmission pulleys, where the adjacent transverse segments are mutually oriented at an angle and where the studs are not fully inserted in the holes.
• the lubrication oil in the hole may resist being expelled by the stud to such an extent that the stud is not inserted fully into the hole, at least not during the transit of a respective transverse segment from the said bent trajectory part into the said straight trajectory part.
• This configuration of the drive belt is, however, to be avoided, because it may adversely affect the reliability of operation of the drive belt.
• a noticeable decrease of the operating efficiency of the drive belt is expected at a radial stud/hole-clearance of 25 microns or less. Below a radial stud/hole-clearance of 10 microns the efficiency decrease may become especially pronounced, due to the studs of the transverse segments not being inserted fully into the holes thereof during the above-mentioned transit.
• transverse segments that are formed progressively i.e. that are produced from plate material towards their final shape in a number of cutting and shaping stages
• a stud/hole-clearance of 25 microns or less on average between the transverse segments, in case of the lower limit for the spread or tolerance in manufacturing.
• the effective thickness thereof will typically amount to less than 0.70 mm.
• the equation (1) prescribes a maximum of 35 microns for the radial stud/hole-clearance for the standard, 24 mm wide transverse segment.
• a practical range for the radial stud/hole- clearance will normally include a value of less than 25 microns.
• a practical manufacturing tolerance range based on the equation (1) can be: 25 ⁇ 10 microns, which range has a minimum value of 15 microns. Thus, already when a slightly larger manufacturing tolerance is allowed, such minimum value will drop to 10 microns or less.
• the present disclosure aims to reconcile the desire to apply a small radial stud/hole-clearance with the desire to minimise the adverse affect that such small clearance can has on the transmission efficiency.
• this disclosure is aimed at facilitating or otherwise enhancing the discharge of lubrication oil from the hole of the transverse segment by a stud of an adjacent transverse segment that is inserted into it.
• An obvious measure for improving such discharge would be to apply the said small radial stud/hole-clearance only in the width direction of the transverse segment and to apply larger clearance in other directions, in particular in the height direction of the transverse segment perpendicular to the width and thickness directions thereof, for example by flattening an underside and a topside of the stud relative to its conventional round cross-sectional shape, or by shaping the hole more or less like an ellipse with its long-axis in the height and its short-axis in the width direction.
• the preferred production method is to form the stud from material that is made available by the (press-)shaping of the hole, the stud and the hole are preferably provided with a largely similar shape.
• the circumference surface of the stud and/or of the hole is corrugated in the sense that it is provided with ridges and grooves, mutually alternating along the circumference of the stud and/or the hole.
• Such corrugation was found to be surprisingly effective in improving the discharge of lubrication oil from the hole in comparison with the many other conceivable shapes of the stud and/or the hole.
• the radial stud/hole-clearance can be approximately and favourably the same in every direction, i.e. along the entire circumference of the stud and hole.
• the advantageous lubrication oil discharge feature of the surface corrugation is attributed to a twofold effect thereof. Firstly, the grooves of the corrugation form channels that accommodate the lubrication oil and that facilitate the discharge thereof, in particular if the corrugation is applied to the stud of the transverse segment. Secondly and probably most importantly, by the corrugation the pressure exerted by the stud on the lubrication oil when it enters into the hole is increased, at least locally at the protruding ridges thereof, which pressure serves to set the lubrication oil in motion towards an area of lower pressure, i.e. to the corrugation grooves and, ultimately, to the outside of the hole.
• the corrugation is provided preferably along the entire circumference of the stud and/or hole and preferably on a fine scale.
• the top surfaces of the ridges of the corrugation may each be between 10 and 100 microns wide and may be mutually separated by between 25 and 250 microns, at least for the said commonly applied transverse segment.
• figure 1 provides a schematically representation of the known continuously variable transmission with two pulleys and a drive belt;
• figure 2 illustrates a transverse segment of the drive belt according to figure 1, both in a side and in a front elevation thereof;
• figure 3 schematically indicates the feature of rotation of the transverse segments of the belt at a pulley ("element yawing");
• figure 4 provides a novel embodiment of the transverse segment in a cross- sectional perspective view of a top part thereof including a stud and a hole
• figure 5 provides a different view of the novel embodiment of the transverse segment according to figure 4.
• Figure 1 shows the central parts of a known continuous variable transmission, as is commonly applied in the drive line of personal vehicles between the engine and the drive wheels thereof.
• the transmission comprises two pulleys 1, 2, each provided with two pulley sheaves 4, 5, and a drive belt 3 that is wrapped around the said pulleys 1, 2, located clamped between the respective pulley sheaves 4, 5 thereof.
• the pulley sheaves 4, 5 are shaped generally conical and at least one pulley sheave 4 is incorporated in the transmission axially moveable along a respective pulley shaft 6, 7 over which it is placed.
• the transmission also comprises activation means that impose on the said at least one sheave 4 an axially oriented force Fax directed towards the respective other pulley sheave 5, such that the belt 3 is clamped there between and a rotational movement and accompanying torque can be transmitted between the pulleys at a variable transmission ratio.
• the drive belt 3 comprises at least one endless or ring-shaped carrier 31 and a number of transverse segments 33, with the carrier ring 31 extending through an opening 37 of the transverse segments 33, such that these are moveable along the circumferential direction of the carrier ring 31.
• the carrier ring 31 consists of two parts 31, each such part being composed of a number of individual bands 32 that are narrowly fitted around one another.
• the transverse segments 33 are basically metal plates that are facing in the circumferential direction of the carrier ring 31 and that are provided with a friction surface 35 on either axial side thereof, for frictionally engaging the pulley sheaves 4, 5.
• adjacent transverse segments 33 abut one another through their respective front and rear main surfaces 38, 41 as is shown for a pair of abutting transverse segments 33 on the right-hand side of figure 2.
• a bottom side of the transverse segments 33 is tapered.
• An axially extending edge 42, between such tapered bottom side and a top part transverse segments 33 of largely constant thickness, on the front main surface 38 serves as and defines the axis of rotation between each pair of abutting transverse segments 33.
• the known transverse segments 33 include a stud 39 projecting from the front main surface 38 and a hole 40 provided in the back main surface 41.
• the stud 38 of a first transverse segment 33 of a pair of abutting transverse segments 33 is at least partly inserted in the hole of a second transverse segment 33 of such pair, whereby these transverse segments 33 mutually align each other perpendicular to the said circumferential direction.
• a clearance or play RCL there between in the radial direction of the stud limits -i.e. determines the maximum possible- mutual displacement between the abutting transverse segments 33 in the plane of the main surfaces 38, 41.
• Figure 3 provides a schematic view of a pair of abutting transverse segments 33 that are both clamped between the sheaves 4, 5 of a pulley 1, 2. From this figure 3 it appears that a rotation of the transverse segments 33 about the radial direction is accompanied by a sliding movement between the front main surface 38 with the stud 39 and the rear main surface 41 with the hole 40 of the transverse segments 33, which sliding movement is thus limited to said radial stud/hole-clearance RCL. According to the art, it is preferred that this type of rotation of the transverse segments 33 is limited, such that the forces Fn L , Fn R exerted by the pulley sheaves 4, 5 on the friction surfaces 35 of the transverse segment 33 work to counteract such rotation. If the cross-sectional shape of the transverse segment 33 closely approximates a rectangle, this latter criterion can be quantified as follows:
• - W is the width thereof.
• a more or less rounded or slanted transition surface 25 is mostly present between the main surfaces 38, 41 and the friction surfaces 35 of the transverse segments 33, either as incorporated in the particular design of the transverse segment 33 or as a result of the processes involved in the manufacturing thereof, such as blanking and (stone) tumbling.
• the effective width Teff of this latter transverse segment 33 that available for contact with the pulley sheaves 4, 5, i.e. the breadth of the friction surfaces 35 thereof, is noticeably less than the largest or overall thickness Tall of that transverse segment 33. In this case the equation (1) applies instead.
• the (cross-sectional shape of the) transition surface 25 between the friction surface 35 and the front main surface 38 can be approximated by arc with a radius of 0.3 mm, whereas the transition surface 25 between the friction surface 35 and the rear main surface 41 can be approximated by a slanted plane with a dimension in the thickness direction of the transverse segment 33 of 0.5 mm.
• the effective thickness Teff of such transverse segment 33 is 0.8 mm less than its overall thickness Tall, which overall thickness in this example amounts to 1.5 mm in combination with a width of the transverse segment 33 of 24 mm.
• the equation (1) prescribes a maximum radial stud/hole-clearance RCL of 35 microns, which maximum value can be controlled in manufacturing by means of a tolerance range of -for instance- 25 ⁇ 10 microns.
• Figure 4 provides a cross-section section of such novel transverse segment 33, showing only the top part thereof with the stud 39 and the hole 40.
• circumference surface 43 of the hole 40 is corrugated, i.e. is provided with a pattern of mutually alternating ridges 44 and grooves 45.
• Figure 5 provides a further view of such novel transverse segment 33 shown in figure 4, in particular of the hole 40 with the corrugated circumference surface 43.
• Figure 5 provides a view of the rear main surface 41 of such novel transverse segment 33, looking into the hole 40 thereof.
• ridges 44 and grooves 45 are provided in total along the circumference of the hole 40, with the breadth of each groove 45 amounting to about four time the breadth of the (top surface of the) ridges 44.
• tops of the ridges 44 may be curved slightly concavely to closely follow the contour of the circumference surface of the stud 39, however, these ridge tops are preferably shaped as essentially flat or even slightly convexly surfaces to further increase the pressure exerted by the ridges 44 on the lubrication oil when the stud 39 is inserted (further) into the hole 40.
• the stud 39 and the hole 40 are typically provided with a diameter of approximately 2.0 mm.
• the corrugation shown in the figures 4 and 5 can be calculated to be on a fine scale with the ridge tops having a breadth of ⁇ 28 microns, each pair of adjacent ridge tops being separated by ⁇ 112 microns, which latter value thus represents the said breadth of the groove 45.
• this disclosure concerns a transverse segment 33 for a drive belt 3 with a carrier ring 31 and with a plurality of transverse segments 33 that are placed slideably on the carrier ring 31, which transverse segments 33 are each provided with two main surfaces 38, 41, where between the transverse segment 33 extends in thickness direction and with two friction surfaces 35 provided on either side thereof, where between the transverse segment 33 extends in width direction, whereof on a front main surface 38 is provided with a largely cylindrically shaped protrusion 39 and whereof a rear main surface 41 is provided with a largely cylindrically shaped indentation 40, a diameter of the indentation 40 being somewhat larger than a diameter of the protrusion 39, whereby at least some radial clearance RCL is present between the protrusion 39 and the indentation 40 of two subsequent transverse segments 33 in the drive belt 3, with a circumference surface of the protrusion 39 or a circumference surface 43 of the indentation 40 being ribbed, i.e. corrugated.
• This disclosure also concerns the above-
• This disclosure also concerns any one of the above-described transverse segments 33, wherein the ridges 44 and the grooves 45 extend over the circumference surface 43 in the axial direction thereof.
• This disclosure also concerns any one of the above-described transverse segments 33, wherein the ridges 44 and the grooves 45 extend over the circumference surface 43 in the axial direction thereof.
• This disclosure also concerns any one of the above-described transverse segments 33, wherein a dimension of the ridges 44 in the circumference direction of the circumference surface 43 amounts to between 10 and 100 microns and wherein a dimension of the grooves 45 in that direction amounts to between 25 and 250 microns.
• This disclosure also concerns any one of the above-described transverse segments 33, wherein the diameter of the indentation 40 is at most 35 micron, preferably at most 25 micron, more preferably at most 10 micron larger than the diameter of the protrusion 39.
• This disclosure also concerns a drive belt 3 with a carrier ring 31 and with a plurality of any one of the above-described transverse segments 33 that are placed slideably on the carrier ring 31.
• This disclosure also concerns the above-described drive belt 3, wherein, on average between all pairs of adjacent transverse segments 33 in the drive belt 3, the said radial clearance RCL is at most 25 micron.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Transmissions By Endless Flexible Members (AREA)
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Cited By (1)

Citations (6)

Family Cites Families (5)

• 2012
  • 2012-12-24 NL NL1039973A patent/NL1039973C2/en active
• 2013
  • 2013-12-23 WO PCT/EP2013/077873 patent/WO2014102225A1/en active Application Filing
  • 2013-12-23 CN CN201380067461.4A patent/CN104937307B/zh active Active
  • 2013-12-23 JP JP2015550058A patent/JP6391591B2/ja not_active Expired - Fee Related

Patent Citations (6)

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