JP2013515916A - Drive belt for transmission with convex pulley sheave - Google Patents

Abstract

  The present invention relates to a drive belt for a continuously variable transmission for a motor vehicle with two pulleys, each pulley having two substantially conical pulley sheaves that are driven between the pulley sheaves. A belt is held in a variable radial position, and the drive belt is provided with a transverse element (32), the transverse element (32) having flanks for frictional contact with pulleys on both sides (40) (40) is provided, and the flank (40) is provided with one or more grooves (41) of two different types, of which the first type of groove (50) is Deeper than the second, shallower type groove (51).

Description

  The present invention relates to a drive belt for use in a continuously variable transmission with two variable pulleys, particularly with a convex pulley sheave, as described in the preceding paragraph of claim 1 below. An example of this type of drive belt and associated transmission is described in WO 2006/062400. This known drive belt is particularly characterized by an array of transverse elements slidably attached to a continuous, ie endless tension element.

  When describing the direction with respect to the transverse element, it is always assumed that the transverse element is in an upright position, as shown in FIG. 2 as a front view of the transverse element. In this figure, the longitudinal direction or circumferential direction of the drive belt is perpendicular to the plane of the figure. The horizontal direction or the width direction is a direction from left to right, and the radial direction or the height direction is a direction from top to bottom in the plane of FIG.

  Known transverse elements have a lower part, an intermediate part and an upper part. The endless tension element is formed in this example by two sets of multiple, flat, flexible, ie relatively thin, metal rings. The edges of the lower part of the transverse element, facing upwards in the direction of the upper part, form the support surface of these ring sets. The substantially arrow-shaped upper part of the transverse element is arranged above or radially outward of the ring set and surrounds the ring set in the height direction. The middle part arranged at the height of the ring set connects the lower part and the upper part to each other, the laterally directed edges of the intermediate part being the axial direction of the respective ring set relative to the transverse element A stop surface is formed to restrict the movement. The transverse element is held on the drive belt so that it can move with respect to the circumferential direction of the endless tension element. In this example, a concave portion is provided on one main surface, for example, the rear surface of each transverse element, and a protrusion is provided on the other main surface, for example, the front surface, of each transverse element. The protrusion of one transverse element in is held in the recess of another, ie adjacent transverse element. In addition, the lower part of the transverse element is generally slightly rounded, what is known as a locking edge, ie between the upper side of the substantially constant thickness of the transverse element and the tapered lower side. A transition section is provided. The locking edge allows for relative rotation of adjacent transverse elements so that the drive belt can follow a circumferentially curved track as required at the position of the transmission pulley.

  In known drive belts, the transverse element substantially occupies the entire circumference of the endless tension element and is clamped between the convexly curved sheaves at the position of the transmission pulley, thereby driving the friction force Can be transmitted between the pulley and the drive belt. As a result, the rotation of one pulley can be transmitted to the other pulley by means of a transverse element that pushes forward in the direction of rotation while being guided by an endless tension element.

  As can be seen in the front view of the transverse element, the laterally directed flank or side surface of the lower part of the transverse element is in this case provided with a convex curvature in the height direction. These sides are in frictional contact with the sheave surface of the pulley, which is slightly swollen, i.e. also convex, as seen in the pulley cross section including the (rotational) central axis of the pulley. It has become. The side surfaces of the known transverse elements have one or more grooves, which are defined with respect to the overall or generally convex curved profile of each side surface. . These grooves are provided to receive the lubricant and to achieve a preferably high coefficient of friction between the drive belt and the pulley, as applied in this type of transmission.

  Although known drive belts work by themselves, it has been found that after prolonged operation of the drive belt in the transmission, the side surfaces are prone to wear undesirably. As a result, it has been found that the coefficient of friction gradually but significantly decreases during operation. It has been found that such wear is a problem, particularly when wear is distributed unevenly and the convex profile of the side changes during operation. In extreme cases, it has been found that some of the sides may completely lose the initial convex profile.

  It is an object of the present invention to reduce side wear during operation, or at least reduce side non-uniformity. According to the invention, the object can be achieved by applying the features of the following claim 1 in the design of known drive belts.

  According to the invention, the side surface of the transverse element is provided at least initially with a surface profile (protrusion) having protrusions separated by both relatively shallow and relatively deep grooves. Deeper grooves are provided to receive lubricant as well as known belts, whereas shallower grooves, at least for known belts, are at least side protrusions between the grooves and pulley sheaves. Is provided in order to reduce the initial contact area.

  As a result, a so-called running-in effect is produced during the initial operation of the transmission. That is, the side protrusions wear relatively quickly. By providing a shallow groove, the contact area of the protrusion increases relatively rapidly and accordingly the drive belt is reduced until the wear rate drops to (almost) zero and a steady state minimum wear rate is achieved. The contact pressure between the pulley and the pulley decreases. During initial leveling running wear on the side (surface profile) of the transverse element, the side has an overall side profile that provides a preferably low and / or evenly distributed wear rate during long term operation of the transmission. Naturally formed and stable to provide.

  The invention will be described in more detail below by way of example with reference to the accompanying drawings.

1 schematically shows a continuously variable transmission provided with two pulleys and a drive belt according to the prior art. FIG. FIG. 2 is a cross-sectional view of the transmission shown in FIG. 1 oriented in a tangential direction at a pulley sheave position. 1 is a side view of a transverse element of a drive belt according to the prior art. FIG. 1 is an enlarged view of a part of a known transverse element, seen in the direction of movement of the drive belt or in the circumferential direction, this part having the side of the transverse element provided with a surface profile with grooves. FIG. 4 is an enlarged view of a portion of a side surface provided with a surface profile defined in accordance with the present invention.

  FIG. 1 schematically shows a view of the central part of a continuously variable transmission according to the prior art. The known transmission can be driven by an engine (not shown) by a (forced) primary connection Tp and a primary pulley 1 provided on the input shaft 6 of the transmission and a load side (not shown) by a secondary connection Ts. And a secondary pulley 2 provided on the output shaft 7 of the transmission. Both pulleys 1, 2 are substantially conical pulley sheaves 5 fixedly attached to the respective pulley shafts 6, 7 and can be moved axially with respect to said shafts 6, 7. And a conical pulley sheave 4. The drive belt 3 is clamped between the pulley sheaves 4 and 5 of the two pulleys 1 and 2, and each of these drive belts substantially describes a path in the form of a part of a circle, ie a running radius R. Yes. Mechanical power can be transmitted between the two pulley shafts 6 and 7 by friction between the drive belt 3 and the pulleys 1 and 2, and the transmission ratio of the transmission 1 is such that the primary pulley 1 and the secondary pulley 2 It is given by the ratio of the running radius R of the drive belt 3 at each position.

  The drive belt 3 shown here is of the so-called push belt type with substantially continuous individual elements of transverse elements 32, each transverse element comprising a lower part 33, an upper part 35, a lower part The intermediate portion 34 is formed by connecting the side portion 33 and the upper portion 35 to each other. The edges 36 facing radially upward of the lower part 33 on each side of the upper part 35, ie on each side of the intermediate part 34, facing the upper part 35, are continuous. That is, a support surface 36 for the endless tension element 31 is formed. In this example, the endless tension element 31 is formed by two sets 31a, 31b of a number of overlapping, ie concentrically stacked, flat, relatively thin, flexible rings. The ring of endless tension element 31 and transverse element 32 are made of metal, typically maraging steel and carbon steel, respectively.

  The upper part 35 of the transverse element 32 is arranged radially outward of the endless tension element 31 and surrounds the endless tension element 31 in the height direction, whereas the intermediate part 34 is of the endless tension element 31. It is arranged between the ring sets 31a and 31b. In this case, the axially or laterally directed edge 37 of the intermediate part forms an axial stop surface 37 for the ring sets 31a, 31b, respectively.

  The transverse element 32 is held by the drive belt 3 so that it can move in the circumferential direction of the endless tension element 31. In this arrangement, a recess (not shown) is provided in one main surface, for example the rear surface 46, of each transverse element, and a protrusion is provided on each other main surface, for example the front surface 43, of the transverse element. 44, and each protrusion 44 of the transverse element 32 is received in a recess in the adjacent transverse element 32. The lower portion 33 of the transverse element 32 includes what is known as an oscillating edge 45, ie, a substantially constant thickness of the upper portion of the transverse element 32 and the effectively tapered lower portion of the transverse element. There is a generally slightly rounded transition between and the rocking edge 45 extends transversely at the front face 43 of the transverse element 32. The oscillating edge 45 allows an oscillating or tilting movement between adjacent transverse elements 32, so that the drive belt 3 is curved between the sheaves 4, 5 of the pulleys 1, 2 when viewed in the circumferential direction. Can be followed.

  As shown schematically in FIG. 2 in a cross-sectional view of the transmission at the position of pulley sheaves 4, 5, the conical surfaces of sheaves 4, 5 of two pulleys 1, 2 are spherical or convex It is known from the prior art to form in a shape. In this example, the conical surface 10 of the pulley sheaves 4 and 5 has a constant radius of curvature Rr10 and is curved slightly convex in a transverse plane defined by the radial direction and the axial direction. The laterally directed flank or side 40 on each side of the lower part 33 of the transverse element 32 is also provided with a convex curve with a radius of curvature Rr40. In practice, these two radii of curvature Rr10, Rr40 are both significantly larger than the radii of curvature shown in FIG. 2 (and other figures) and are exaggerated in the drawings for clarity. Further, the radii of curvature Rr10, Rr40 have a significant angle between the radial direction and the pulley sheaves 4, 5 and an angle between the radial direction and the side surface 40, ie several degrees, for example about 7.4 degrees and 11 It is specified to change only 4 degrees between 5 degrees. Furthermore, in practice, a curvature radius that changes in the radial direction or the height direction is also used, in contrast to the constant curvature radii Rr10 and Rr40.

  In the transmission, liquid lubricants are used to limit as much as possible wear and / or damage between the sheave face 10 and the side face 40 that are in frictional contact with each other. The side surface 40 of the known transverse element 32 has one or more grooves 41 for receiving the lubricant and thus for achieving a preferably high coefficient of friction in the frictional contact. Yes.

  The side 40 of the transverse element 32 is shown in more detail in FIGS. 3 and 4, which show a side view and a front view of the transverse element 32 at the location of the side 40 of the transverse element, respectively. ing. Side 40 is shown as having a number of grooves 41 separated by a higher portion 42 of side 40. The higher portion 42 forms a side, generally or generally convexly curved profile, and in fact makes (direct, ie physical) contact with the pulley sheave surface 10 during operation. .

  The groove 41 substantially extends in the thickness direction of the transverse element 32, that is, in the circumferential direction of the drive belt 3, and extends between the rear surface 46 and the front surface 43 of the transverse element. The dimensions of the individual grooves 41 in the height or radial direction of the drive belt 3, i.e. the width of the grooves, are preferably approximately equal to 1-5% of the total dimension of the side surface 40 in that direction. The depth of the groove 41 is a less important parameter and is preferably 25% to 50% of the width of the groove.

  In particular, the typical application of the drive belt 3 in a transmission for a passenger car that is driven at one transmission ratio for a long time may cause local, and thus uneven, highly undesirable wear on the side 40. The surface profile of the side surface 40 can be improved in view of the fact that

  According to the present invention, the side surface 40 of the transverse element 32 is provided at least initially with a surface profile having a protrusion 52 separated by a relatively shallow groove 51 and a relatively deep groove 50. This surface profile according to the invention is shown in FIG. 5 in an enlarged view of the portion “A” of the transverse element 32, which portion “A” is the portion shown for the known transverse element 32 in FIG. 4. Corresponding to

  The deeper groove 50 is provided for the purpose of receiving a lubricant, just as in known belts, whereas the shallower groove 51 is at least compared to the known belt 3 with grooves 50, It is provided to reduce at least the initial contact area between the protrusion 52 between the pulleys 51 and the pulley sheaves 4 and 5. As a result, a leveling effect occurs during the initial operation of the transmission. That is, the protrusion 52 of the side surface 40 is worn relatively quickly. By providing the shallow groove 51, the contact area of the protrusion 52 increases relatively rapidly, and the contact pressure between the drive belt 3 and the pulleys 1 and 2 is accordingly reduced to (almost) zero wear rate. Decrease until steady state minimum wear rate is achieved. During the initial running-in wear of the side surface 40 (surface profile) of the transverse element 32, the side surface of the transverse element preferably provides a low and / or evenly distributed wear rate during the long-term operation of the transmission. Naturally formed and stable so as to provide an overall lateral profile.

  Preferably, the surface profile protrusion 52 is provided at least initially with a smoothly rounded (curved) profile that is smoothly rounded. Preferably, the shallow grooves 51 and the deep grooves 50 are alternately provided on the side surface 40. More preferably, the shallow groove 51 and the deep groove 50 extend over the entire local thickness of the transverse element 32, ie the dimension of the transverse element in the circumferential direction of the drive belt 3.

  Preferably, the deep groove 50 is 5 to 25 times deeper than the shallow groove 51, and the groove depth is at the (relatively) protruding portion 52 that is the initial contour “C” of each side surface 40. It is measured perpendicular to the tangent virtual continuous convex curve. More preferably, the depth of the deep groove is 25 to 250 μm. More preferably, the depth of the shallow groove 51 is 2 to 20 μm. More preferably, the deep groove 50 has a depth greater than five times the depth of the shallow groove 51.

  Preferably, the deep groove 50 has a width of 25-100 μm, while the shallow groove 51 has a width of 100-250 μm. More preferably, the shallow groove 51 has a width larger than twice the width of the deep groove 50.

  Preferably, at least the shallow groove 51, but more preferably the deep groove 50, at least initially, is provided with a smoothly rounded, concavely curved contour. More preferably, the concave contour of at least the shallow groove 51 of the surface profile smoothly transitions to the convex contour of the protrusion 52 but preferably also to the contour of the deep groove 50.

Claims (8)

  A drive belt (3) for a continuously variable transmission for a motor vehicle with two pulleys (1, 2), each pulley (1, 2) having two substantially conical pulley sheaves ( 4 and 5), a drive belt (3) is held between the pulley sheaves in a variable radial position (R), said drive belt (3) having a transverse element (32) The transverse element (32) is provided with a side surface (40) for frictional contact with the pulley (1,2), the surface (40) having a groove (41; 50; 51) In the form in which a profile is provided, the surface profile has at least two types of grooves (50; 51) separated by protrusions (52) of the surface profile, of which the first Type of Groove (50), a second, and said deeper than shallower type grooves (51), the drive belt (3) for a continuously variable transmission for a motor vehicle.   The drive belt (1) according to claim 1, wherein the side surface (40) of the transverse element (32) is curved convexly at least if it is defined by a virtual continuous curve in contact with the projection of the surface profile. 3).   3. The drive belt according to claim 1, wherein shallow grooves (51) and deep grooves (50) are provided alternately in the surface profile.   The depth of the groove (50; 51) is measured perpendicular to a virtual continuous convex curve in contact with the protrusion (52) of the surface profile. The drive belt (3) according to item.   The drive belt (3) according to claim 4, wherein the depth of the shallow groove (51) is 2 to 20 µm and / or the depth of the deep groove (50) is 25 to 250 µm.   The drive belt (3) according to any one of claims 1 to 5, wherein the width of the deep groove (50) is 25 to 100 µm.   The drive belt (3) according to any one of claims 1 to 6, wherein the width of the shallow groove (50) is 100 to 250 µm.   8. A transmission comprising two pulleys (1, 2) having two substantially conical pulley sheaves (4, 5), between said pulley sheaves. In the type in which the drive belt (3) according to claim 1 is held at a variable radial position (R), the pulley sheave (4, 5) of the pulley has a convex curve along the radial direction of the pulley sheave. A transmission characterized in that a transmission is provided.

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