CN-122029054-A - Tyre for vehicle wheels

Abstract

The application relates to a tyre (2) for vehicle wheels, comprising a tread band (9) having a tread surface comprising at least one surface portion having a surface roughness, wherein the power spectral density of the surface portion having the surface roughness is represented by a curve representing the power spectral density as a function of wave number in units of The sum of the power spectral densities in units of The curve comprising a middle region extending over a predetermined wavenumber range from an initial wavenumber value up to a final wavenumber value, the wavenumber range being equal to 0.20 in the curve and the initial wavenumber value being between 3.6 and 4.5 in the curve, the curve comprising two points representing power spectral density values at the initial wavenumber value and at the final wavenumber value, wherein a straight line joining the two points has a negative angle coefficient, the absolute value of the negative angle coefficient being 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 (12)

1. 1. Tyre (2) for vehicle wheels, comprising a tread band (9) having a tread surface comprising at least one surface portion having a surface roughness, wherein: -the power spectral density of the surface portion having the surface roughness is represented by a curve representing the power spectral density as a function of wave number in units of The sum of the power spectral densities in units of Is expressed in logarithmic units with a base of 10; -the curve comprises an intermediate region extending over a predetermined wavenumber range from an initial wavenumber value up to a final wavenumber value, the wavenumber range being equal to 0.20 in the curve and the initial wavenumber value being between 3.6 and 4.5 in the curve; -the curve comprises two points representing power spectral density values at an initial wave value and at a final wave value, wherein a straight line joining the two points has a negative angle coefficient, the absolute value of the negative angle coefficient being greater than or equal to 6.
2. 2. Tyre (2) according to claim 1, wherein said curve comprises a first region immediately upstream of the intermediate region, in which said power spectral density remains substantially constant as said wave number increases.
3. 3. Tyre (2) according to claim 2, wherein said first region is contiguous with said intermediate region and extends the covered wavenumber range up to said initial wavenumber value of said intermediate region.
4. 4. A tyre (2) as claimed in 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. Tyre (2) according to any one 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. Tyre (2) according to any one of claims 2 to 5, wherein, in said first region, the value of the power spectral density is comprised between-19 and-15.
7. 7. Tyre (2) according to any one of the previous claims, wherein the absolute value of said negative angle coefficient is greater than or equal to 7.
8. 8. Tyre (2) according to any one of the previous claims, wherein said initial wave value of said intermediate region is in the range of 3.8 to 4.4 in said curve.
9. 9. Tyre (2) according to any one of the previous claims, wherein in said intermediate region said power spectral density exhibits a tendency to overall decrease with increasing wavenumber with respect to the average value of said power spectral density in said first region.
10. 10. Tyre (2) according to any one of the previous claims, wherein said surface roughness has an average roughness value Ra comprised between 8 and 50 μm.
11. 11. Tyre (2) according to any one of the previous claims, wherein said curve further comprises a third region immediately downstream of the intermediate region, in which said power spectral density exhibits a general decreasing trend with increasing wavenumbers with respect to the average value of said power spectral density in said third region.
12. 12. Tyre (2) according to claim 11, wherein in said third region the decrease in power spectral density is generally slower than the decrease in power spectral density in said intermediate region as the wave number increases.

Description

Tyre for vehicle wheels Technical Field The present invention relates to a tyre for vehicle wheels. Background The tire of the present invention is preferably a tire intended to achieve high performance on low grip roads, particularly snow-covered or ice roads. However, the tire of the present invention may be used on tight and/or high grip roadways, such as, for example, dry asphalt roadways. 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 above-mentioned axially opposite ends respectively engage with respective annular anchoring structures, each of which is normally formed by at least one substantially circumferential annular insert, called "bead core", on which at least one filler insert is normally applied, which tapers radially away from the rotation axis. The annular anchoring structures are located in the areas generally identified as "beads". The inner diameter of the bead corresponds approximately to the so-called "fitting diameter" of the tire 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 in a radially external position 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, made of elastomeric material having suitable properties 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 tyre axial outer surface with respect to a median plane perpendicular to the tyre rotation axis. 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 "tubeless" tyres, at least one layer of elastomeric material is provided at a radially internal position with respect to the carcass ply, commonly referred to as "liner", 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 building process of a green tyre comprises the steps of building a carcass structure, building a crown structure and shaping and assembling steps in which a toroidal shape is imparted to the carcass structure by assembling the carcass structure 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 structure of the tyre 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 formed of circumferential sectors configured to be coupled to the first sidewall plate and the second sidewall plate when the curing mold is closed to continue curing of the green tire. The circumferential sectors surround the molding cavity and are typically provided with a plurality of shaped reliefs intended to create a series of grooves on the tread band appropriately arranged according to the desired tread pattern. In particular, the surfaces of the circumferential sectors are shaped as negative molds that together reproduce the desired tread pattern of the tire. The term "elastomeric material" is used to denote a composite comprising at least one elastomeric polymer and at least one reinforcing filler. Such composites may also include various types of additives, such as 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 with reference to the vulcanization mold used in the tire production process. In particular, the terms "axial" and "axially" are used to indicate reference values/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 reference values/quantities of arrangement/measurement or extension 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