Tire for motor-vehicle wheels provided with a tread producing a low rolling noise
AssigneePirelli Coordinamento Pneumatici S.p.A.
InventorsMaurizio Boiocchi, Gianfranco Colombo
Life of this patent
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Abstract
A tread for motor-vehicle tires has a raised pattern formed of a plurality of shaped blocks 7 distributed in circumferential rows 3, 4, 5, 6 disposed in parallel and in side by side relation. The number of the shaped blocks 7 arranged in each row gradually increases while moving from the equatorial plane X--X to the axial outer side edges 1a of the tread 1. Thus a gradual increase in the longitudinal stiffness of the shaped blocks 7 is achieved on passing from the side edges 1a of the tread 1 to the equatorial plane X--X, which brings about a reduction in the mobility of said blocks on the road contact patch and lower rolling noise.
Claims18
A tire for motor-vehicle wheels provided with a tread producing a low rolling noise, comprising:
- a raised pattern formed of a plurality of shaped blocks (7, 7a, 7b) distributed in parallel circumferential rows (3, 4, 5, 6) bounded by longitudinal grooves (2) extending circumferentially of the tire, the parallel circumferential rows (3, 4, 5, 6) comprising inner central rows (3), inner shoulder rows (5) and outer shoulder rows (6), the outer shoulder rows (6) being adjacent to respective side edges of the tire,
- each row comprising a plurality of shaped blocks circumferentially separated from each other by respective transverse cuts (8, 9, 9a, 10),
- in which each of said rows has first transverse cuts (8) each of which are in alignment with a respective one of the first transverse cuts of an adjacent block row to define continuous transverse grooves (13) each extending from an outer side edge of the tread to a position adjacent an equatorial plane of the tire,
- wherein each of said transverse grooves (13) comprises a first portion extending from one of the axial outer side edges of the tread and extending between blocks of an outer shoulder row (6), and a second portion disposed obliquely of the longitudinal grooves (2) and located between blocks of an inner central row (3), and one curved union portion between the first and second portions, wherein in each row of said shaped blocks said first transverse cuts (8) define an impact angle (.alpha.) with the respective longitudinal grooves, the value of the impact angle (.alpha.) in the rows (6) of blocks closest to each of the axial outer side edges of the tread is in the range of 70.degree. to 105.degree., and
- said inner central rows have a number of shaped blocks which is lower than the number of shaped blocks provided in the outer shoulder rows,
- wherein at least one continuous circumferential rib (11) is disposed close to the equatorial plane, said rib being defined by two of said longitudinal grooves (2),
- wherein said longitudinal grooves (2) have a smaller width than the first transverse cuts (8),
- wherein the first portion of said continuous transverse grooves and the second portion of said continuous transverse grooves are straight.
Dependencies are inferred from the claim text.