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CN-122029034-A - Vulcanizing mold for a tire of a vehicle wheel

CN122029034ACN 122029034 ACN122029034 ACN 122029034ACN-122029034-A

Abstract

The invention relates to a vulcanisation mould for tyres (2) for vehicle wheels and to a method for manufacturing such a mould. The mould comprises a moulding surface of a tread band (9) of a tyre (2), at least one surface portion of the moulding surface of the tread band having a surface roughness, wherein-the surface portion having the surface roughness has a power spectral density described by a curve representing the power spectral density as a function of the wave number, the power spectral density in m4 and the wave number in nr1 being each represented in logarithmic units with a base of 10, -the curve comprises an intermediate region extending over a predetermined wave number range from an initial wave number value up to a final wave number value, the wave number range in the curve being equal to 0.20, and the initial wave number value being between 3.6 and 4.5 in the curve, -the curve comprises two points representing the power spectral density values at the initial wave number value and at the final wave number value, wherein the straight line joining these two points has a negative angular coefficient, the absolute value of which is greater than or equal to 6.

Inventors

  • R. Balochino
  • C. R. E. Rawiza
  • A. Longqi
  • D.E. Speziari

Assignees

  • 倍耐力轮胎股份公司

Dates

Publication Date
20260512
Application Date
20241016
Priority Date
20231019

Claims (20)

  1. 1. A vulcanisation mould for tyres (2) for vehicle wheels, comprising a moulding surface of a tread band (9) of said tyre (2), at least one surface portion of said moulding surface of said tread band having a surface roughness, wherein: -the surface portion having the surface roughness has a power spectral density described by a curve representing the power spectral density as a function of the wave number, the power spectral density in m 4 and the wave number in m -1 being each represented in logarithmic units, base 10; -the curve comprises an intermediate region extending over a predetermined wavenumber range from an initial wavenumber value up to a termination wavenumber value, the wavenumber range in the curve being equal to 0.20, and the initial wavenumber value being between 3.6 and 4.5 in the curve; -the curve comprises two points representing the power spectral density values at the initial wave value and at the termination wave value, wherein a straight line joining the two points has a negative angular coefficient, the absolute value of the angular coefficient being greater than or equal to 6.
  2. 2. The vulcanization mold of claim 1, wherein the curve includes a first region immediately upstream of the intermediate region in which the power spectral density remains substantially constant as the wavenumber increases.
  3. 3. A vulcanisation mould according to claim 2, wherein said first zone is contiguous with said intermediate zone and extends over a wavenumber range of said initial wavenumber values up to said intermediate zone.
  4. 4. A vulcanisation mould according to claim 2 or 3, wherein in said curve said first region extends over a wavenumber range greater than or equal to 0.3.
  5. 5. A vulcanisation mould as claimed in any of claims 2 to 4, wherein in said curve said first region extends over a wavenumber range less than or equal to 2.
  6. 6. The vulcanisation mold according to any of the claims from 2 to 5, wherein in said first region the value of the power spectral density is comprised between-19 and-15.
  7. 7. A vulcanisation mould according to any of the previous claims, wherein the absolute value of the angular coefficient is greater than or equal to 7.
  8. 8. A vulcanisation mould according to any of the previous claims, wherein said initial wave value of said intermediate zone is comprised between 3.8 and 4.4 in said curve.
  9. 9. A vulcanisation mould according to any of the previous claims, wherein in said intermediate zone, with respect to the average value of the power spectral density in said first zone, the power spectral density exhibits a general decreasing trend with increasing wavenumber.
  10. 10. A vulcanisation mould according to any of the previous claims, wherein said surface roughness has an average roughness value Ra comprised between 8 and 50 μm.
  11. 11. A vulcanisation mould according to any of the previous claims, wherein said vulcanisation mould comprises a plurality of circumferential sectors which define as a whole the moulding surface of the tread band.
  12. 12. A method for producing a vulcanisation mould for tyres (2) for vehicle wheels, comprising a plurality of sectors, wherein each of said sectors comprises a moulding surface of a tread band portion (9) of the tyre (2), comprising, for each sector: -manufacturing at least one surface portion of the molding surface to have a surface roughness such that: Said at least one surface portion of said molding surface having said surface roughness has a power spectral density described by a curve representing power spectral density as a function of wave number, wherein said power spectral density in m 4 and said wave number in m -1 are each represented in logarithmic units, base 10; The curve comprises an intermediate region extending over a predetermined range of wavenumbers starting at an initial wavenumber value and ending at a final wavenumber value, the wavenumber range in the curve being equal to 0.20 and the initial wavenumber value being between 3.6 and 4.5 in the curve; The curve comprises two points representing the power spectral density values at the initial wave value and at the termination wave value, wherein a straight line joining the two points has a negative angular coefficient, the absolute value of the angular coefficient being greater than or equal to 6.
  13. 13. The method of claim 12, further comprising, for each sector, manufacturing a master pattern (20) of the sector, the master pattern comprising a pattern outer surface (21) representative of a negative of the molding surface.
  14. 14. The method of claim 13, further comprising, for each sector, silicone casting on the mold outer surface (21) to produce a silicone overmold of the master mold (20), the silicone overmold comprising an inner surface of a male mold representing the molding surface.
  15. 15. The method of claim 14, further comprising, for each sector, performing a gypsum pour on the inner surface of the silicone overmold to produce a gypsum overmold comprising an outer surface of a negative mold representing the molding surface.
  16. 16. The method of claim 15, further comprising, for each sector, metal casting on the outer surface of the gypsum overmold to produce a metal overmold comprising an inner surface that forms a molding surface of a mold sector.
  17. 17. The method according to claim 16, wherein for each sector the surface roughness on the at least one surface portion of the molding surface is obtained at the same time as manufacturing the main mold (20) or the plaster overmolded or the metal overmolded.
  18. 18. The method of any of claims 12 to 17, wherein the surface roughness on the at least one surface portion of the molding surface is made from a digital model in which the surface roughness is defined by a predetermined algorithm.
  19. 19. The method of claim 18, wherein the predetermined algorithm is a berlin noise algorithm.
  20. 20. The method of any of claims 16 to 19, further comprising, for each sector, removing the plaster overmold from the metal overmold to obtain a mold sector having the molding surface.

Description

Vulcanizing mold for a tire of a vehicle wheel Technical Field The present invention relates to a vulcanisation mould for tyres for vehicle wheels, and a method for manufacturing a vulcanisation mould. Background Tires for vehicle wheels generally comprise a carcass structure shaped according to a substantially toroidal configuration and comprising at least one carcass ply having axially opposite ends. The axially opposite ends described above are engaged with respective annular anchoring structures, each of which is generally formed by at least one substantially circumferential annular insert (known as "bead core") on which at least one filler insert is generally applied, said filler insert tapering radially away from the axis of rotation. The annular anchoring structures are located in the areas commonly referred to as "beads". The inner diameter of the bead corresponds substantially to the so-called "fitting diameter" of the tyre on the respective mounting rim. The tire further comprises a crown structure comprising at least one belt strip in a radially external position with respect to the carcass ply, and a tread band radially external with respect to the belt strip. Longitudinal and transverse incisions are typically formed in the tread band, which are arranged to define a desired tread pattern. Between the tread band and the belt strip or strips, a so-called "underlayer" may be arranged, which underlayer is made of an elastomeric material having suitable properties in order to achieve a firm bond between the belt strip or strips and the tread band. The tyre also comprises a pair of so-called sidewalls made of elastomeric material, said sidewalls representing the axially external surface of the tyre with respect to a median plane perpendicular to the rotation axis of the tyre. For example, the sidewalls represent an axially external surface with respect to the annular anchoring structure, one or more carcass plies, one or more belt strips and possibly at least a portion of the tread band. In a "tubeless" tyre, at least one layer of elastomeric material (commonly referred to as "liner") is provided in a radially internal position with respect to the carcass ply, said layer of elastomeric material having airtight characteristics and generally extending from one bead to the other. The production cycle of the tire provides the building process of the green tire and the subsequent molding and curing processes. In particular, the green tyre building process comprises the steps of building a carcass structure, building a crown structure and shaping and assembling steps in which the carcass structure is given a toroidal shape by assembling it to the crown structure. The green tyre thus built is transferred to a moulding and vulcanisation line where a moulding and vulcanisation process is carried out, which is adapted to define the tyre structure according to the desired geometry and tread pattern. For this purpose, the green tyre is arranged in a moulding cavity defined inside the vulcanisation mould. Generally, the curing mold includes a first sidewall plate, a second sidewall plate opposite the first sidewall plate, and a crown of circumferential sectors configured to be coupled to the first sidewall plate and the second sidewall plate when the curing mold is closed for curing the green tire. The circumferential sectors surround the molding cavity and are typically provided with a plurality of shaped projections intended to create a series of grooves in the tread band suitably arranged according to the desired tread pattern. In particular, the surfaces of the circumferential sectors are shaped in such a way as to jointly reproduce the negative of the tread pattern desired for the tyre. The term "elastomeric material" is used to refer to a composite comprising at least one elastomeric polymer and at least one reinforcing filler. Such composites may also include additives such as, for example, cross-linking agents and/or plasticizers. Due to the presence of the cross-linking agent, such materials can be cross-linked by heating to form the final product. The terms "axial", "radial", "circumferential" and "circumferentially" are used with reference to the tire or to the vulcanization mold used in the tire production process. In particular, the terms "axial" and "axially" are used to refer to references/quantities arranged/measured or extended in a direction substantially parallel to the rotation axis of the tyre or vulcanisation mould. The terms "radial" and "radially" are used to indicate references/quantities arranged/measured or extended in a direction perpendicular to the rotation axis of the tyre or of the vulcanisation mould and lying in a plane comprising such rotation axis. The terms "circumferential" and "circumferentially" are used to indicate references/quantities arranged/measured or extended along a circumference developing around the rotation axis of the tyre or of the vulcanisation mould. The ter