US-12623496-B2 - Tire comprising an optimized layer of self-sealing product

US12623496B2US 12623496 B2US12623496 B2US 12623496B2US-12623496-B2

Abstract

The tire comprises a tread ( 14 ) comprising a deeply cut rib ( 68, 70 ) and a slightly cut rib ( 62, 64, 66 ), and a layer of a self-sealing product ( 80 ) comprising: a portion ( 90″, 92 ″) extending in line with the deeply cut rib ( 68, 70 ) and having an average thickness Ec>0 of self-sealing product, and a portion ( 100′, 102′, 104 ′) extending in line with the slightly cut rib ( 62, 64, 66 ) and having an average thickness Eb≥0 of self-sealing product such that Eb<Ec.

Inventors

Frederic Sarazin

Assignees

COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN

Dates

Publication Date: 20260512
Application Date: 20210924
Priority Date: 20200929

Claims (14)

1 . A tire comprising a tread comprising: P deeply cut ribs comprising at least one transverse cut having a depth Ht such that Ht/Hs≥50%, where Hs is a tread pattern height and P is a total number of deeply cut ribs present on the tire, wherein a width of the transverse cuts of the P deeply cut ribs is greater than or equal to 1.0 mm; Q=2 or Q=3 non-cut or slightly cut ribs, Q being a total number of non-cut or slightly cut ribs present on the tire, the non-cut or slightly cut ribs lacking transverse cuts or comprising transverse cuts, each non-cut or slightly cut rib satisfying, for at least 50% of a number of transverse cuts of the or each non-cut or slightly cut rib, the following conditions: the transverse cuts of each non-cut or slightly cut rib have a width strictly less than 1.0 mm, and the transverse cuts of each non-cut or slightly cut rib have a depth H such that H/Hs<50%; an airtight internal layer; and a layer of a self-sealing product extending circumferentially radially on an inside of part of the airtight internal layer, wherein, over at least 50% of a circumferential length of the layer of self-sealing product, the layer of self-sealing product comprises: P>1 axial portions extending axially in line with one of the P deeply cut ribs and each having an average thickness Eck>0 of self-sealing product, one or more thick axial portions, at least partially coinciding with all or part of the P>1 axial portions, and Q=2 or Q=3 axial portions extending axially in line with one of the Q non-cut or slightly cut ribs and each having an average thickness Ebj≥0 of self-sealing product, with j ranging from 1 to Q, and being such that, for each value of k ranging from 1 to P, at least 50% of the values of j ranging from 1 to Q are such that Ebj<Eck, wherein each of the one or more thick axial portions is axially delimited by two adjacent inflection points on a radially inner surface curve of the layer of self-sealing product, each inflection point being (1) a point at which, in a meridian section plane, a direction of curvature of the radially inner surface curve of the layer of self-sealing product changes or (2) a termination point of the radially inner surface curve of the layer of self-sealing product in contact with the airtight internal layer, and wherein a thickness of each of the one or more thick axial portions increases in a direction axially toward an inside of the each of the one or more thick axial portions from each of the adjacent inflection points.
2 . The tire according to claim 1 , wherein each deeply cut rib and each non-cut or slightly cut rib is axially delimited by an axially inner end and by an axially outer end, each axially inner and outer end being chosen from: an axial end of the tread, and an axially inner or outer end of a main circumferential cut having a depth Ha such that Ha/Hs≥50%, the axially inner and outer ends of each deeply cut rib or each non-cut or slightly cut rib being ends that are adjacent to one another.
3 . The tire according to claim 1 , wherein Ec≥1.10×Eb.
4 . The tire according to claim 1 , wherein Ec≤5.00×Eb.
5 . The tire according to claim 1 , wherein an axial width Wy of the each of the one or more thick axial portions is such that Wy/Lcy≥0.50, where Lcy is an axial width of each deeply cut rib.
6 . The tire according to claim 1 , wherein the or each transverse cut of each deeply cut rib has a depth ranging from 2.0 mm to the tread pattern height.
7 . The tire according to claim 1 , wherein each axial end of the layer of self-sealing product is arranged at an axial distance less than or equal to 20% of the tread in relation to each axial end, respectively, of the tread.
8 . The tire according to claim 1 , wherein the tread comprises: an axially central portion comprising: two axially outermost main circumferential cuts arranged axially one on each side of a median plane of the tire and having a depth Ha1, Ha2, respectively, such that Ha1/Hs≥50% and Ha2/Hs≥50%, and each non-cut or slightly cut rib, and wherein first and second axially lateral portions arranged axially on an outside of an axially central portion axially one on each side of the axially central portion in relation to a median plane of the tire, each first and second axially lateral portion extending axially from each axial end of the tread to each axially outer end of each axially outermost main circumferential cut, at least one of the first and second axially lateral portions comprising a deeply cut rib.
9 . The tire according to claim 8 , wherein each first and second axially lateral portion comprises a first and a second deeply cut rib, respectively.
10 . The tire according to claim 1 , wherein the Q=2 or 3 axial portions are arranged axially between two adjacent axial portions of the layer of self-sealing product extending axially in line with two of the P deeply cut ribs.
11 . The tire according to claim 10 , wherein the tread comprises N=Q+1>1 main circumferential cuts respectively having a depth Hai such that Hai/Hs≥50% for i ranging from 1 to N, N being a total number of main circumferential cuts present on the tire, each non-cut or slightly cut rib being arranged axially between two adjacent main circumferential cuts and being delimited axially by the two adjacent main circumferential cuts, wherein the layer of self-sealing product comprises N>1 axial portions each extending axially in line with one of the N main circumferential cuts and each having an average thickness Eai>0 of self-sealing product, such that, for each value of i ranging from 1 to N, at least 50% of the values of j ranging from 1 to Q are such that Ebj<Eai.
12 . The tire according to claim 11 , wherein each main circumferential cut has an axial width greater than or equal to 1.0 mm.
13 . The tire according to claim 11 , wherein each main circumferential cut has a depth ranging from 4.0 mm to the tread pattern height.
14 . The tire according to claim 11 , wherein an axial width Wx of each of the one or more thick axial portions is such that Wx/Lcx≥0.50, where Lcx is an axial width of a main circumferential cut.

Description

BACKGROUND The present invention relates to a tyre. A tyre is understood to mean a casing intended to form a cavity by cooperating with a support element, for example a rim, this cavity being able to be pressurized to a pressure higher than atmospheric pressure. A tyre according to the invention has a structure of substantially toroidal shape exhibiting symmetry of revolution about a main axis of the tyre. EP2629964 discloses a tyre comprising a tread intended to come into contact with the ground, when the tyre is running, via a tread surface. The tread comprises main circumferential cuts and central ribs, each of which is arranged axially between two adjacent main circumferential cuts and which are axially delimited by the said two adjacent main circumferential cuts. The tyre of EP2629964 comprises an airtight internal layer intended to form a cavity which is airtight with respect to the inflation gas when the tyre is mounted on a mounting support, for example a rim, and a layer of a self-sealing product extending circumferentially radially on the inside of part of the airtight internal layer. In the event of perforation of the tyre owing to a perforating object, the layer of self-sealing product makes it possible to seal the orifice created by the perforating object under the effect of the internal pressure of the tyre. This is because, under the effect of the internal pressure of the tyre, the self-sealing product is made to flow into the orifice through which the air streams towards the outside, in order to seal it and re-establish airtightness with respect to the inflation gas. Numerous self-sealing products have been described in the prior art, notably in U.S. Pat. No. 4,426,468, EP1090069, WO99/62998, U.S. Pat. Nos. 4,113,799, 4,115,172, 4,913,209, 5,085,942, 5,295,525, FR2955587 and EP2167329. The presence of the layer of self-sealing product, although it has proven to be effective at combating perforations, necessarily causes the tyre to become heavier than a tyre that lacks a layer of self-sealing product. An aim of the invention is to provide a tyre provided with a layer of sealing product, which is as lightweight as possible and of which the layer of self-sealing product is substantially as effective against perforations as the layers of self-sealing product of the tyres of the prior art. SUMMARY To this end, one subject of the invention is a tyre comprising: a tread comprising:at least one rib, referred to as deeply cut rib, comprising at least one transverse cut having a depth Ht such that Ht/Hs≥50%, where Hs is the tread pattern height,at least one rib, referred to as non-cut or slightly cut rib, which lacks transverse cuts or comprises transverse cuts, each satisfying, for at least 50% of the number of transverse cuts of the or each non-cut or slightly cut rib, at least one of the following conditions: the transverse cut of the non-cut or slightly cut rib has a width strictly less than 1.6 mm,the transverse cut of the non-cut or slightly cut rib has a depth H such that H/Hs<50%, an airtight internal layer,a layer of a self-sealing product extending circumferentially radially on the inside of part of the airtight internal layer,over at least 50% of the circumferential length of the layer of self-sealing product, the layer of self-sealing product comprising:an axial portion extending axially in line with the deeply cut rib and having an average thickness Ec>0 of self-sealing product,an axial portion extending axially in line with the non-cut or slightly cut rib and having an average thickness Eb≥0 of self-sealing product such that Eb<Ec. The inventors responsible for the invention have determined that the axial portions of the tread that run the greatest risk of being perforated are the ribs in which the deepest transverse cuts are formed. In accordance with the invention, these axial portions comprise the transverse cuts having a depth at least equal to half of the tread pattern height. Thus, the invention provides a relatively high average thickness Ec of self-sealing product in line with these deeply cut ribs, thereby making it possible to ensure high effectiveness of the layer of self-sealing product against the perforations that occur in these deeply cut ribs. In order to reduce the weight of the tyre, the inventors have determined that the weakly or slightly cut ribs statistically run a lower risk of being perforated. This is because, in the case of a non-cut rib, a relatively great thickness of the tread resists perforation to a greater extent than a relatively small thickness does. In the case of a slightly cut rib comprising shallow transverse cuts, for the one part, the thickness of the tread protects the tyre from perforation if the perforating object is relatively short and, for the other part, a relatively great thickness of the tread resists perforation to a greater extent than a relatively small thickness does. In addition, in the case of a slightly cut rib compr