WO2015039933A1 - Anneau souple en acier pour une courroie d'entraînement pour une transmission variable en continu et son procédé de fabrication - Google Patents

Anneau souple en acier pour une courroie d'entraînement pour une transmission variable en continu et son procédé de fabrication Download PDF

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Publication number
WO2015039933A1
WO2015039933A1 PCT/EP2014/069238 EP2014069238W WO2015039933A1 WO 2015039933 A1 WO2015039933 A1 WO 2015039933A1 EP 2014069238 W EP2014069238 W EP 2014069238W WO 2015039933 A1 WO2015039933 A1 WO 2015039933A1
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WO
WIPO (PCT)
Prior art keywords
mass
chromium
ring
drive belt
nickel
Prior art date
Application number
PCT/EP2014/069238
Other languages
English (en)
Inventor
Bert Pennings
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 EP14761653.6A priority Critical patent/EP3047044A1/fr
Publication of WO2015039933A1 publication Critical patent/WO2015039933A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • 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 invention relates both to a flexible steel ring according to the preamble of claim 1 hereinafter and to a method for producing such a ring.
  • This type of ring is used as a component of a drive belt for a continuously variable transmission for, in particular, automotive use such as in passenger motor cars.
  • the drive belt is typically composed of two sets of mutually concentrically arranged rings that are inserted in a recess of transverse members of the drive belt.
  • the drive belt comprises a plurality of these transverse members that are arranged in mutual succession along the circumference of such ring sets.
  • an individual ring normally has a thickness of only 0.2 mm or less, typically of about 0.18 mm.
  • the drive belt is used for transmitting a driving power between two shafts, whereto the drive belt is passed around two rotatable pulleys, respectively associated with one such transmission shaft and provided with two conical discs defining a circumferential V-groove of the pulley wherein the drive belt is accommodated.
  • the drive belt's radius at each pulley -and hence the rotational speed ratio between the transmission shafts- can be varied, while maintaining the drive belt in a tensioned state.
  • This transmission and drive belt are generally known in the art and are, for example, described in the European patent publication EP- A-1243812.
  • the performance of the drive belt is directly linked to not only the combined tensile strength of the ring sets, but to a large extent also the fatigue strength of the individual rings thereof. This is because, during rotation of the drive belt in the transmission, the tension and bending stress in the rings oscillate. In practice it is universally resorted to special steel compositions, in particular so-called maraging steels, as the basic material for the rings in order to realize the desired performance of the drive belt. Additionally to this end, the rings are core hardened and surface (gas-soft) nitrided as part of the standing ring production process.
  • a well known basic material in this respect has a nominal composition of 18 mass% Nickel, 5 mass% Molybdenum, 16 mass% Cobalt, 0.4 mass% Titanium and balance Fe .
  • Such known maraging steel can indeed be processed relatively easily and reliably to form the ring with desirable mechanical properties, it does come with the disadvantage that it is relatively expensive. Therefore, it is a longstanding desire in the art to develop a basic material for the rings that is not only less expensive, but that also can be processed with similar ease and reliability to form rings with similar mechanical properties, in particular fatigue strength, as compared to the known maraging steel basic material.
  • WO 2013/000491 Al a range of stainless steel composition is proposed as a possible alternative.
  • the present disclosure concerns a further development of this known teaching.
  • the chromium oxide that is normally present on the outer surface of the stainless steel is decomposed to free the chromium atoms to form chromium nitride precipitates instead.
  • the process temperature is kept below 400 degrees Celsius just to prevent the decomposition of the chromium oxide layer.
  • the chromium oxide at the ring surfaces decomposes and chromium nitride precipitates form in the metal lattice instead .
  • the rate at which the chromium and nitrogen bond is comparatively slow and, moreover, is exponentially dependent on the process temperature.
  • the presently proposed high-temperature nitriding process should last at least 90 minutes at 450°C and at least 45 minutes at 550°C.
  • the stainless steel alloy composition should additionally satisfy both of the following requirements :
  • Chromium- and Nickel-equivalent values being defined as follows (with all contents expressed in mass%) :
  • chromium-equivalent chromium content + molybdenum content + 1.5*silicon content
  • nickel-equivalent nickel content + 30*carbon content + 0.5* (manganese content + copper content)
  • the ring made from the above basic material composition is nitrided in a gas atmosphere containing 5-15% by volume ammonia, 3-8% by volume hydrogen with either balance nitrogen or with 5-15% by volume of a carbon-containing gas with balance nitrogen.
  • Figure 1 is a schematic illustration of a known drive belt and of a transmission incorporating such known belt.
  • Figure 2 is a schematic illustration of a part of the known drive belt, which includes two sets of a number of flexible steel rings, as well as a plurality of transverse members .
  • Figure 3 figuratively represents a known manufacturing method of the ring that includes a process step of nitriding .
  • Figure 4 figuratively represents the process step of nitriding according to the present disclosure, as part of the overall manufacturing method of the ring.
  • FIG 1 shows schematically a continuously variable transmission (CVT) with a drive belt 3 wrapped around two pulleys 1 and 2.
  • Each pulley 1, 2 is provided with two conical pulley discs 4, 5, where between an annular, predominantly V-shaped pulley 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 ⁇ and an accompanying torgue T from the one pulley 1, 2 to the other 2, 1.
  • Each pulley 1, 2 generally also comprises activation means that can impose on the said at least one disc 4 thereof an axially oriented clamping force directed towards the respective other pulley disc 5 thereof, such that the belt 3 can be clamped between these discs 4, 5. Also, a (speed) ratio of the CVT between the rotational speed of the driven pulley 2 and the rotational speed of the driving pulley 1 is determined thereby. This CVT is known per se.
  • the drive belt 3 is made up of two sets 31 of mutually nested, flat and flexible steel rings 32 and of a plurality of transverse members 30.
  • the transverse members 30 are arranged in mutual succession along the circumference of the ring sets 31, in such manner that they can slide relative to and in the circumference direction of the ring sets 31.
  • the transverse segments 30 take-up the said clamping force, such when an input torgue T 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.
  • FIG. 3 illustrates a relevant part of the known manufacturing method for the drive belt ring set 31, as it is typically applied in the art for the production of metal drive belts 3 for automotive application.
  • the separate process steps of the known manufacturing method are indicated by way of Roman numerals.
  • a thin sheet or plate 11 of a maraging steel basic material having a thickness of around 0.4 mm is bend into a cylindrical shape and the meeting plate ends 12 are welded together in a second process step II to form a hollow cylinder or tube 13.
  • the tube 13 is annealed.
  • the tube 13 is cut into a number of annular hoops 14, which are subseguently -process step five V- rolled to reduce the thickness thereof to, typically, around 0.2 mm, while being elongated.
  • the hoops 14 are usually referred to as rings 32.
  • the ring 32 is subjected to a further, i.e. ring annealing process step VI for removing the work hardening effect of the previous rolling process step by recovery and re-crystallization of the ring material at a temperature considerably above 600 degrees Celsius, e.g. about 800°C.
  • a seventh process step VII the ring 32 is calibrated by mounting it around two rotating rollers and stretching it to a predefined circumference length by forcing the said rollers apart.
  • this seventh process step VII also internal stresses are imposed on the ring 32.
  • the ring 32 is heat-treated in an eighth process step VIII of combined ageing or bulk precipitation hardening and nitriding or case hardening. More in particular, such combined heat-treatment involves keeping the ring 32 in an oven chamber containing a controlled gas atmosphere that comprises ammonia, nitrogen and hydrogen gas. In the oven chamber, i.e. in the process atmosphere, the ammonia molecules decompose at the surface of the ring 32 into hydrogen gas and nitrogen atoms that can enter into the metal lattice of the ring 32. By these interstitial nitrogen atoms the resistance against wear as well as against fatigue fracture is known to be increased remarkably. Typically, this eighth process step VIII of combined ageing and nitriding is carried out until a nitrided layer or nitrogen diffusion zone formed at the outer surface of the ring 32 is between 25 and 35 micron thick .
  • the ring set 31 is formed by radially stacking, i.e. concentrically nesting, a number of thus formed and processed rings 32, as is further indicated in figure 3 in the ninth step IX depicted therein. Since only a small play or clearance is allowed between the neighboring rings 32 of the ring set 31 in the radial direction, each ring 32 of the ring set 31 is reguired to be suitably dimensioned in relation to the other rings 32 thereof. To this end, the individual rings 32 of the ring set 31 are typically selected from a stock of rings 32 of accurately known circumference length.
  • the process temperature in the heat treatment of the eighth process step VIII in the above- described, known manufacturing method is kept below 400 °C, in order to prevent that the protective chromium oxide surface layer of the stainless steel is compromised or even lost completely, due to the formation of chromium nitride precipitates .
  • a process temperature of more than 500°C is applied in the above-described eighth process step VIII.
  • a favourably short (-ened) process time can be applied for the said heat treatment.
  • the protective chromium oxide surface layer of the stainless steel is compromised or lost completely as a result of the said heat treatment and the chromium will form chromium nitride precipitates instead.
  • the fatigue strength of the thus manufactured ring 32 is neither detrimentally effected by the absence chromium oxide surface layer, nor by the presence of chromium nitrides near the surface of the ring 32.
  • good results were obtained with a stainless steel basic material with chromium-equivalent of between 11.5 and 15.5 and a nickel- equivalent of between 9.5 and 11.5.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

L'invention concerne un anneau souple (32) fabriqué en acier inoxydable destiné à être utilisé dans une courroie d'entraînement (3) pour une transmission variable en continu, dont une couche de surface contient des précipités de nitrure de chrome. L'invention concerne en outre un traitement thermique pour la fabrication d'un tel anneau souple (32), c'est-à-dire pour réaliser la couche de surface contenant le nitrure de chrome.
PCT/EP2014/069238 2013-09-19 2014-09-10 Anneau souple en acier pour une courroie d'entraînement pour une transmission variable en continu et son procédé de fabrication WO2015039933A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP14761653.6A EP3047044A1 (fr) 2013-09-19 2014-09-10 Anneau souple en acier pour une courroie d'entraînement pour une transmission variable en continu et son procédé de fabrication

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL1040395A NL1040395C (en) 2013-09-19 2013-09-19 Flexible steel ring for a drive belt for a continuously variable transmission and method for producing such.
NL1040395 2013-09-19

Publications (1)

Publication Number Publication Date
WO2015039933A1 true WO2015039933A1 (fr) 2015-03-26

Family

ID=49585561

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2014/069238 WO2015039933A1 (fr) 2013-09-19 2014-09-10 Anneau souple en acier pour une courroie d'entraînement pour une transmission variable en continu et son procédé de fabrication

Country Status (3)

Country Link
EP (1) EP3047044A1 (fr)
NL (1) NL1040395C (fr)
WO (1) WO2015039933A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018122397A1 (fr) * 2016-12-30 2018-07-05 Robert Bosch Gmbh Composant annulaire métallique d'une courroie d'entraînement pour une transmission à variation continue et son procédé de fabrication

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1243812A1 (fr) 2001-03-19 2002-09-25 Van Doorne's Transmissie B.V. Courroie à éléments poussants et matériau pour celle-ci
US20050187056A1 (en) * 2004-02-24 2005-08-25 Yucong Wang CVT belt with chromium nitride coating
WO2013002633A1 (fr) * 2011-06-30 2013-01-03 Robert Bosch Gmbh Procédé de fabrication d'un composant annulaire de courroie d'entraînement
WO2013000491A1 (fr) 2011-06-30 2013-01-03 Robert Bosch Gmbh Bague flexible pour courroie de transmission d'une transmission à variation continue et procédé de fabrication de cette bague

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1243812A1 (fr) 2001-03-19 2002-09-25 Van Doorne's Transmissie B.V. Courroie à éléments poussants et matériau pour celle-ci
US20050187056A1 (en) * 2004-02-24 2005-08-25 Yucong Wang CVT belt with chromium nitride coating
WO2013002633A1 (fr) * 2011-06-30 2013-01-03 Robert Bosch Gmbh Procédé de fabrication d'un composant annulaire de courroie d'entraînement
WO2013000491A1 (fr) 2011-06-30 2013-01-03 Robert Bosch Gmbh Bague flexible pour courroie de transmission d'une transmission à variation continue et procédé de fabrication de cette bague

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018122397A1 (fr) * 2016-12-30 2018-07-05 Robert Bosch Gmbh Composant annulaire métallique d'une courroie d'entraînement pour une transmission à variation continue et son procédé de fabrication
NL1042208B1 (en) * 2016-12-30 2018-07-23 Bosch Gmbh Robert Metal ring component of a drive belt for a continuously variable transmission and its manufacutring method
JP2020504784A (ja) * 2016-12-30 2020-02-13 ローベルト ボツシユ ゲゼルシヤフト ミツト ベシユレンクテル ハフツングＲｏｂｅｒｔ Ｂｏｓｃｈ Ｇｍｂｈ 無段変速機用の駆動ベルトの金属リング部材およびその製造方法

Also Published As

Publication number Publication date
NL1040395C (en) 2015-03-23
EP3047044A1 (fr) 2016-07-27

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