WO2022135743A1 - Procédé d'étalonnage de la longueur de la circonférence d'un anneau dans un procédé d'assemblage d'un ensemble d'anneaux d'une courroie d'entraînement - Google Patents

Procédé d'étalonnage de la longueur de la circonférence d'un anneau dans un procédé d'assemblage d'un ensemble d'anneaux d'une courroie d'entraînement Download PDF

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Publication number
WO2022135743A1
WO2022135743A1 PCT/EP2021/025514 EP2021025514W WO2022135743A1 WO 2022135743 A1 WO2022135743 A1 WO 2022135743A1 EP 2021025514 W EP2021025514 W EP 2021025514W WO 2022135743 A1 WO2022135743 A1 WO 2022135743A1
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WO
WIPO (PCT)
Prior art keywords
ring
ring set
rings
thickness
assembling method
Prior art date
Application number
PCT/EP2021/025514
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English (en)
Inventor
Rene NUIJTEN
Maria del Carmen MICÓ PEREPÉREZ
Johan VERMEER
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Priority to JP2023539057A priority Critical patent/JP2024506781A/ja
Publication of WO2022135743A1 publication Critical patent/WO2022135743A1/fr

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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

Definitions

  • the present disclosure relates to an assembling method of a ring set for a drive belt, in particular a ring circumference length calibration process therein.
  • the drive belt is mainly used as the means for power transmission between two adjustable pulleys of the well-known continuously variable transmission that is mainly applied in motor vehicles.
  • the present type of drive belt is generally known and is composed of a multitude of relatively thin transverse elements that are slidably incorporated on one or more ring sets that are each composed of a number of mutually nested, flexible rings.
  • the transverse elements are not connected to the ring set, but rather can slide along the circumference thereof, in particular during operation in the transmission. Also the individual rings of the ring set can slide relative to one another.
  • the rings of the drive belt which are alternatively denoted hoops, loops or endless bands, are produced from steel, in particular a maraging steel, that combines -amongst others- the mechanical characteristics of great tensile and (bending) fatigue strength with a relatively favourable possibility to process the steel from sheet-shaped base material towards the desired shape and material properties of the end-product rings, which ideally should not vary along the circumference of the rings.
  • These desired material properties comprise a fair hardness of the ring core material, for combining the characteristics of a great tensile strength together with a sufficient elasticity and ductility to allow longitudinal bending of the ring, and a much harder outer or surface layer, for providing wear resistance to the ring.
  • EP1815160-A1 discloses a manufacturing method that departs from a plate-shaped base material that is bent and welded into a cylindrical shape, or tube.
  • the tube is annealed to restore the original material properties thereof, i.e. to largely remove the internal/residual stress and/or inhomogeneous microstructure introduced in plate bending and tube welding.
  • the annealed tube is cut into a number of hoops, e.g. in a slitting or laser cutting process.
  • the edges of the hoops (between its radially oriented main surfaces and its axially oriented side faces) are typically processed to remove burrs therefrom and/or for rounding these off, i.e. in a tumbling or laser melting process.
  • the hoops are rolled and elongated to a desired thickness, which is typically about 0.185 mm in the end product. After rolling the hoops are flexible in their circumference direction and are referred to as rings or bands, that are annealed to restore the original material properties thereof, i.e. to largely remove the internal/residual stress and/or inhomogeneous microstructure introduced in hoop rolling.
  • the annealed rings are calibrated, in which process step these rings are individually wrapped around two rollers and stretched, by forcing these calibration rollers apart while being rotated.
  • each ring is stretched to a respective predefined diameter or circumference length that corresponds to its intended radial position within the ring set.
  • a residual stress distribution is imposed on the rings that a/o defines a so-called curling radius of the ring, as is explained in detail in the European patent application EP1403551-A1.
  • the diameter of the calibration rollers to a large extend determines such residual stress distribution after calibration.
  • the ring set is assembled by mutually nesting the rings, typically from the radial outside inwards, i.e. in order of decreasing ring circumference length. Only a small gap, i.e. play is allowed between the respective pairs of adjacent rings of the ring set in radial direction, i.e. between the outer radius of a respectively inner ring and the inner radius of a respectively outer ring thereof, in order to maximise the fatigue strength of the ring set as a whole in the drive belt application thereof. Typically, such radial ring play varies between a couple of micron negative play to about 10 micron or so of positive play.
  • the ring set After being assembled, the ring set is heat treated by precipitation hardening to increase ring toughness, and (surface) nitriding to introduce residual compressive stress in the outer surface layer of the rings.
  • Precipitation hardening is also known as aging and is realised through heating the rings to a temperature exceeding 400 degrees Celsius (°C), at which temperature microscopic metallic precipitates incubate and grow at random locations throughout the ring material. As the precipitates grow, the hardness of the ring material increases until, generally speaking, a maximum hardness value is reached, after which the hardness of the ring material typically starts to decrease again (so-called over-aging).
  • precipitation hardening is normally performed in an inert or a reducing process atmosphere, such as nitrogen gas or nitrogen gas with some hydrogen gas mixed-in.
  • Nitriding provides the rings with an additionally hardened and, moreover, compressively stressed surface layer.
  • the rings are kept in an ammonia gas (NH3) containing process atmosphere at a temperature of more than 400°C.
  • NH3 ammonia gas
  • the ammonia molecules dissociate at the surface of the rings, forming hydrogen gas and nitrogen atoms, which latter nitrogen atoms enter into the crystal lattice of the ring material.
  • the nitrogen atoms move away from the surface into the ring material by diffusion, thus providing the ring with a nitrided surface layer of increasing thickness.
  • the thickness of the nitride layer, as well as closely related material properties, such as the hardness and the residual compressive stress at the ring surface, that are obtained in/by the nitriding process thus depend on the composition of the nitriding process atmosphere, in particular the ammonia concentration therein, as well as on the temperature and duration of the nitriding process.
  • the thickness of the nitride layer largely determines the mechanical performance and service life of the drive belt in the transmission.
  • the wear and fatigue properties of the ring are suboptimal, or, if the nitride layer is too thick, the ring material will be too brittle and ring stress levels could exceed the elastic limit during operation. In either case, the ring -and hence the drive belt as a whole- will not perform to its full potential or it may even fail prematurely. Therefore, once a target value has been determined for the nitride layer thickness, it is highly desirable that such target thickness is accurately and consistently realised in the (mass) manufacture of the drive belt.
  • the nitride layer thickness at the inside surfaces of the ring set (i.e. at the radially oriented surfaces of the rings that face each other between the pairs of adjacent rings of the ring set) will be less than at the said outside surfaces thereof.
  • This particular aspect of ring set nitriding is, however, unproblematic, since those inside surfaces of the ring set do not arrive in contact with the transverse elements or the transmission pulleys, i.e. experience less contact stress than the outside surfaces thereof.
  • the target thickness of the nitride layer can be less at the said inside surfaces than at the said outside surfaces of the ring set. Nevertheless, it is highly desirable that such target nitride layer thickness values are both realised as accurately and consistently as possible in the (mass) manufacture of the drive belt.
  • the nitride layer at the said inside surfaces of the ring set is not formed as accurate and/or as consistent as at the said outside surfaces thereof.
  • the present invention sets out to improve the known ring set manufacturing method in this respect, i.e. the present invention aims to improve the accuracy and/or consistency with which the nitride layer is formed inside the ring set, i.e. at the radially oriented surfaces of the rings that face each other between the pairs of adjacent rings of the ring set.
  • a gap in radial direction between the adjacent rings of the ring set is more accurately and more consistently implemented when the ring set is assembled.
  • the process gas can enter essentially equally between all pairs of adjacent rings in the ring set in nitriding, such that the nitride layer will be formed favourably more uniform between the individual rings thereof.
  • different gaps can be applied between different pairs of adjacent rings in the ring set.
  • This latter aspect of the present invention may be desirable for influencing the tensile stress experienced by the individual rings of the ring set during operation of the drive belt and/or for differentiating between the nitride layer thickness of the different ring pairs.
  • This latter aspect of the invention can also be applied to influence a small, but significant growth in circumference direction of the rings, i.e. the lengthening thereof, that typically occurs in nitriding.
  • the thickness of a ring is measured as part of the process step of ring calibration.
  • This measured ring thickness is taken into account when determining a desired (inner or outer) diameter or (inner or outer) circumference length in ring calibration, i.e. when determining the final, maximum distance that is applied (i.e. forced) between the calibration rollers in ring calibration.
  • the invention thus takes into account the ring thickness variations between the individual rings after ring rolling. Although these latter thickness variations are small compared to the overall ring thickness, they are of the same order of magnitude as the said radial gap that is required between the rings in nitriding to realise the said radial ring play in the end product, i.e. in the micrometre range.
  • Such thickness measurement is preferably performed contactless, e.g. optically and can be performed before, but preferably during the stretching of the rings in ring calibration.
  • the said maximum distance S applied between the centrelines of the calibration rollers in ring calibration is stepwise increased or decreased between sequentially calibrated rings of the ring set.
  • - G[x] represents the gap that is applied in radial direction between the x th and (x+1) th ring pair of the ring set in calibration and that can have the same value for all ring pairs in the ring set.
  • Equation (1o) applies if the rings of the ring set are sequentially calibrated starting from the radially outermost ring (with index [m]) radially inwards
  • equation (1i) applies if the ring set is assembled by sequentially nesting rings from the inside out.
  • at least the elastic deformation of ring must be taken into account as well in a known manner, i.e. whether by calculation/estimation or by measurement.
  • equation (1o; 1 i) it appears that the thickness of the outermost ring (with index [m]) is not needed, at least not within the context of the present invention, such that the measurement thereof can potentially be omitted. Moreover, if the ring set is assembled from the outside in, equation (1o) suggests that the desired diameter or circumference length of the rings (other than the said outermost ring) is determined, in part, by the (measured) thickness of a respective ring itself that must thus be measured when the ring is stretched to such desired diameter or circumference length.
  • equation (1i) suggests that the desired diameter or circumference length of the rings (other than the said outermost ring) is determined, in part, by the (measured) thickness of an adjacent ring that is located inside such respective ring in the ring set.
  • the ring thickness measurement can also be carried out after the ring is stretched.
  • the ring thickness is measured while the ring is tensioned by calibration rollers. More preferably, the said measured ring thickness is determined as an average of multiple measurements along the circumference of the ring.
  • the ring can be rotated by the calibration rollers in-between or even during the said multiple thickness measurements.
  • figure 1 provides a schematically depicted example of the well-known continuously variable transmission provided with a drive belt
  • figure 2 is a section of the drive belt shown in perspective
  • figure 3 schematically illustrates the presently relevant part of the known, overall manufacturing method of the ring set component of the drive belt
  • figure 4 provides a diagrammatic representation of the heat treatment of gas-soft nitriding in the manufacturing method according to figure 3
  • figure 5 schematically illustrates the process step of ring calibration in accordance with the present invention.
  • Figure 1 shows the central parts of a known continuously variable transmission or CVT that is commonly applied in the drive line of motor vehicles between the engine and the drive wheels thereof.
  • the transmission comprises two pulleys 1, 2, each provided with two conical pulley discs 4, 5, where between a predominantly V-shaped groove is defined and whereof one disc 4 is axially moveable along a respective pulley shaft 6, 7 over which it is placed.
  • a drive belt 3 is wrapped around the pulleys 1, 2 for transmitting a rotational movement co and an accompanying torque T from the one pulley 1 , 2 to the other 2, 1.
  • the transmission generally also comprises activation means that impose on the said at least one disc 4 an axially oriented clamping force Fax directed towards the respective other pulley disc 5 such that the belt 3 is clamped there between. Also, a (speed) ratio of the transmission between the rotational speed of the driven pulley 2 and the rotational speed of the driving pulley 1 is determined thereby.
  • FIG. 2 An example of a known drive belt 3 is shown in detail in figure 2 in a section thereof, which belt 3 incorporates two ring sets 31 that are each composed of a set of -in this example- six thin and flat, i.e. band-like, flexible rings 32.
  • the belt 3 further comprises a multitude of plate-like metal transverse elements 33 that are held together by the ring sets 31 that are each located in a respective recess of the transverse elements 33.
  • the transverse elements 33 take-up the said clamping force Fax, such when an input torque Tin is exerted on the so-called driving pulley 1 , friction between the discs 4, 5 and the belt 3, causes a rotation of the driving pulley 1 to be transferred to the so-called driven pulley 2 via the likewise rotating drive belt 3.
  • the drive belt 3 and in particular the rings 32 thereof are subjected to a cyclically varying tensile and bending stresses, i.e. a fatigue load.
  • a fatigue load i.e. the resistance against metal fatigue, i.e. the fatigue strength of the rings 32 thus determines the service life of the drive belt 3 at a given torque T to be transmitted thereby. Therefore, it has been a long standing general aim in the development of the ring set manufacturing method to realise the required ring fatigue strength and wear resistance at a minimum combined material and processing cost.
  • Figure 3 illustrates the presently relevant part of the known overall drive belt 3 manufacturing method, i.e. of the manufacturing of the ring set(s) 31 thereof, wherein separate process steps are indicated by way of Roman numerals.
  • a thin sheet or plate 11 of base material that typically has a thickness in the range between 0.3 mm and 0.6 mm is bend into a cylindrical shape and the meeting plate ends 12 are welded together in a second process step II to form an open, hollow cylinder or tube 13.
  • the tube 13 is annealed.
  • the tube 13 is cut into a number of annular hoops 14, which are subsequently -process step five V- rolled to reduce the thickness thereof to a value between 0.100 and 0.250 mm, typically to about 185 micron, while being elongated.
  • rings 32 After rolling the hoops 14 are referred to as rings 32.
  • the rings 32 are subjected to a further, i.e. ring annealing process step VI for removing the work hardening effect of the previous rolling process (i.e. step five V) by recovery and re-crystallisation of the ring material at a temperature considerably above 600 degree Celsius (“°C"), e.g. about 800 °C.
  • a further, i.e. ring annealing process step VI for removing the work hardening effect of the previous rolling process (i.e. step five V) by recovery and re-crystallisation of the ring material at a temperature considerably above 600 degree Celsius (“°C"), e.g. about 800 °C.
  • the rings 32 are calibrated, i.e. they are each individually wrapped around two rollers and are stretched to a predefined circumference length while being rotated, by forcing the said rollers apart.
  • this seventh process step VII also an internal stress distribution is imposed on the rings 32.
  • ring sets 31 are assembled, each from a number of the rings 32 of suitable, mutually adapted circumference length, by stacking these rings 32 one around the other.
  • the ring set 31 is illustrated with only two rings 32 for simplicity, the ring set 31 is typically composed of 6 to 12 rings.
  • the ring sets 31 are heat-treated in a ninth process step IX of precipitation hardening or aging IX-A and of gas-soft nitriding IX-N. More in particular, aging and nitriding involve heating the ring sets 31 to a temperature of between 400 and 550 °C in a furnace containing a controlled gas atmosphere that is composed of nitrogen, hydrogen and ammonia gas.
  • the exact process settings of the heat treatment are selected in dependence on the base material of the rings 32 (i.e. the alloy composition of the maraging steel), as well as on the mechanical properties that are desired for the rings 32.
  • the nitriding part of the ninth process step IX is schematically illustrated in a cross-section B-B of the ring set 31 indicated in figure 3.
  • a gap 34 between the illustrated pair of adjacent rings 32 is highly exaggerated (i.e. in reality, such gap 34 is far smaller than, i.e. considerably less than 10% the thickness of the rings 32).
  • the ring set 31 is immersed in a process atmosphere containing gaseous ammonia molecules that are schematically represented in figure 4 by four circles each: a large circle representing a nitrogen atom and three smaller circles representing the hydrogen atoms of the ammonia molecules.
  • ammonia dissociation reaction can thus be represented in a formula, as follows:
  • the rate at which this ammonia dissociation reaction (2) occurs is proportional to the process temperature and the ammonia concentration in the process atmosphere and is inversely proportional to the hydrogen concentration in the process atmosphere.
  • the ammonia concentration will typically be less than at the outside the ring set 31.
  • ammonia is supplied mostly by (gas) diffusion, whereas outside the gap 34 also a forced circulation of the process atmosphere is available to supply ammonia (and to remove hydrogen).
  • the path length of ammonia diffusion inside the gap 34 is much longer than to the outside of the ring set 31. This means that inside the gap 34 the ammonia concentration is highly dependent on the size of the gap 34, as is the thickness of the resulting nitride layer.
  • the accuracy and/or consistency of the gaps 34 created between each pair of adjacent rings 32 in the ring set 31 in the said eighth process step VIII of ring set 31 assembling is improved.
  • such improvement is realised by determining the diameter or (inner) circumference length of the ring 32 that is to be obtained in the process step VII of ring calibration, not only in relation to the radial position of that respective ring 32 within the ring set 31 , but also in relation to the actual thickness thereof.
  • ring thickness is measured as part of the process step VII of ring calibration.
  • the process step VII of ring calibration is thereto carried out in 4 stages.
  • the ring 32 is placed around two calibration rollers 15.
  • the two calibration rollers 15 are moved apart until the ring 32 runs straight there between, i.e. is tensioned there between with minimal elastic elongation.
  • the ring 32 is rotated by (rotationally) driving one or both of the calibration rollers 15, while the thickness D of the ring 32 is measured at several locations along its circumference to determine an average value for such thickness D.
  • the ring thickness D is continually measured and averaged along the entre circumference of the ring.
  • the two calibration rollers 15 are moved further apart to increase a distance S between the centrelines thereof, whereby the ring 32 is plastically deformed until its desired diameter or (inner) circumference length is reached that takes into account its measured (average) thickness D.
  • an elastic spring-back of the ring 32 that occurs at removing of the ring tension and possibly other influence factors need to be taken into account as well, as is already known and practiced in the art.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Heat Treatment Of Articles (AREA)
  • Control Of Heat Treatment Processes (AREA)

Abstract

L'invention concerne un procédé d'assemblage d'un ensemble (31) d'anneaux souples (32) qui sont imbriqués entre eux, comprenant une étape de traitement (VII), chaque anneau souple (32) étant étalonné par étirage de celui-ci jusqu'à un diamètre prédéfini ou à une longueur de circonférence prédéfinie, respectivement, qui correspond à sa position radiale prévue à l'intérieur de l'ensemble (31) d'anneaux. Selon la présente invention, ledit diamètre prédéfini ou ladite longueur de circonférence prédéfinie des anneaux souples (32) est déterminé par rapport à une épaisseur mesurée des anneaux souples (32).
PCT/EP2021/025514 2020-12-24 2021-12-22 Procédé d'étalonnage de la longueur de la circonférence d'un anneau dans un procédé d'assemblage d'un ensemble d'anneaux d'une courroie d'entraînement WO2022135743A1 (fr)

Priority Applications (1)

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JP2023539057A JP2024506781A (ja) 2020-12-24 2021-12-22 駆動ベルト用のリングセットの組立て方法におけるリングの周方向の長さの較正プロセス

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL1043882A NL1043882B1 (en) 2020-12-24 2020-12-24 Ring circumference length calibration process in a manufacturing method of a ring set for a drive belt
NL1043882 2020-12-24

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1403551A1 (fr) 2002-09-30 2004-03-31 Van Doorne's Transmissie B.V. Courroie de transmission et transmission continûment variable l'utilisant
EP1815160A1 (fr) 2004-11-17 2007-08-08 Robert Bosch Gmbh Courroie de poussee et son procede de fabrication
WO2009132689A1 (fr) * 2008-04-28 2009-11-05 Robert Bosch Gmbh Procédé de fabrication d’un composant d'anneau de courroie d'entraînement
WO2020135928A1 (fr) * 2018-12-24 2020-07-02 Robert Bosch Gmbh Procédé de fabrication d'un segment métallique pour un jeu de segments d'une courroie d'entraînement pour une transmission à variation continue

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1403551A1 (fr) 2002-09-30 2004-03-31 Van Doorne's Transmissie B.V. Courroie de transmission et transmission continûment variable l'utilisant
EP1815160A1 (fr) 2004-11-17 2007-08-08 Robert Bosch Gmbh Courroie de poussee et son procede de fabrication
WO2009132689A1 (fr) * 2008-04-28 2009-11-05 Robert Bosch Gmbh Procédé de fabrication d’un composant d'anneau de courroie d'entraînement
WO2020135928A1 (fr) * 2018-12-24 2020-07-02 Robert Bosch Gmbh Procédé de fabrication d'un segment métallique pour un jeu de segments d'une courroie d'entraînement pour une transmission à variation continue

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JP2024506781A (ja) 2024-02-15
NL1043882B1 (en) 2022-07-20

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