PatentDe  


Dokumentenidentifikation EP1275526 05.07.2007
EP-Veröffentlichungsnummer 0001275526
Titel Luftreifen
Anmelder Sumitomo Rubber Industries Ltd., Kobe, Hyogo, JP
Erfinder Miyazaki, Shinichi, Kobe-shi, Hyogo-ken, JP;
Toda, Osamu, Kobe-shi, Hyogo-ken, JP
Vertreter Manitz, Finsterwald & Partner GbR, 80336 München
DE-Aktenzeichen 60220215
Vertragsstaaten DE, FR, GB
Sprache des Dokument EN
EP-Anmeldetag 05.07.2002
EP-Aktenzeichen 020151072
EP-Offenlegungsdatum 15.01.2003
EP date of grant 23.05.2007
Veröffentlichungstag im Patentblatt 05.07.2007
IPC-Hauptklasse B60C 9/04(2006.01)A, F, I, 20051017, B, H, EP
IPC-Nebenklasse B60C 9/13(2006.01)A, L, I, 20051017, B, H, EP   

Beschreibung[en]

The present invention relates to a pneumatic tire, more particularly to a carcass structure being capable of reducing the tire weight.

In recent years, in order to improve vehicles' fuel consumption, there is a strong demand for a lightweight tire. Therefore, in order to decrease the tire weight, an attempt to decrease the carcass weight was made by decreasing the cord count for the carcass ply. As well known in the art, a pneumatic tire is vulcanized in a mold while pressurizing the inside of the tire. Therefore, there is a tendency for the topping rubber of the innermost carcass ply to flow out through the carcass cords during vulcanizing the tire. Accordingly, if the carcass cord count is decreased in the innermost carcass ply, the outflow tendency of the topping rubber increases, and as shown in Fig.5, the thickness of the topping rubber (g) covering the inside of the carcass cords is greatly decreased from (t') to (t). As a result, problems such as lowering of airtightness, cord corrosion, cord/rubber separation and the like arise, and the durability is liable to decrease.

DE-A-28 51 526 discloses a flexible body having textile cords of different diameters embedded in a rubber-like material. These textile cords may be used in the belt of a tire for example. The textile cords can provide a tire with the same stability as steel cords but do not conduct heat and cannot corrode.

US-A-3 783 926 discloses a tire carcass with two plies merging into one ply. Successive cords of each ply are inserted between adjacent cords of the other ply, so that the cords of the two plies are located substantially at the same distance from the inner wall of the tire in regions of the carcass between the midheights of the two sidewalls.

GB-A-990,392 discloses a tire carcass where textile cords and metal wires are arranged alternately in the tire circumferential direction. The textile cords and the metal wires have the same diameter and both reinforce the tire. These heterogeneous layers comprising cords of different materials help to decrease the deleterious defects of stresses and to increase the adhesion.

EP-A-555 071 discloses a rubber coated layer for a radial tire where the reinforcing cords are divided into a plurality of groups and the distance between mutually adjoining and opposite reinforcing cords not grouped with each other is wider than a distance between mutually adjoining reinforcing elements separately arranged at equal spaces.

Attention is also drawn to the disclosure of US-A-4 363 346.

It is therefore, an object of the present invention to provide a pneumatic tire, in which the tire weight is reduced without deteriorating the durability. This object is met by a pneumatic tire according to claim 1.

Preferably, the gaps between the carcass cords are set in a range of from 0.02 to 0.80 mm.

Therefore, the strength necessary for the carcass ply is provided by the main cords, and the auxiliary cords hinder the outflow of the topping rubber which causes the topping rubber thickness decrease. Accordingly, the weight of the auxiliary cords can be minimized as far as they can prevent the outflow during vulcanizing the tire, and the total weight of the carcass cords and topping rubber can be minimized without deteriorating the durability.

Embodiments of the present invention will now be described in detail in conjunction with the accompanying drawings.

  • Fig.1 is a cross sectional view of a pneumatic tire according to the present invention.
  • Fig.2 is an enlarged schematic cross sectional view of a carcass ply showing an arrangement of main cords and auxiliary cords.
  • Fig.3 is an enlarged schematic cross sectional view of a carcass ply showing another example of the arrangement of the main cords and auxiliary cords
  • Fig.4 is a diagram for explaining the function of the auxiliary cords.
  • Fig.5 is an enlarged schematic cross sectional view of a carcass ply used in reference tires in the undermentioned comparison tests.

In the drawings, pneumatic tire 1 according to the present invention comprises a tread portion 2, a pair of sidewall portions 3, a pair of bead portions 4 each with a bead core 5 therein, a carcass 6 extending between the bead portions 4, and a belt 7 disposed radially outside the carcass 6 in the tread portion 2.

In the example shown in Fig.1, the tire 1 is a radial tire for passenger cars.

The carcass 6 is composed of at least one ply 6A of carcass cords 10. The carcass cords 10 in the ply 6A are arranged radially at an angle of from 70 to 90 degrees with respect to the tire equator, and each extend between the bead portions 4 through the tread portion 2 and sidewall portions 3, and all is turned up around the bead core 5 in each bead portion 4 from the axially inside to the axially outside so as to form a pair of carcass ply turnup portions 6b and a carcass ply main portion 6a therebetween.

The carcass 6 in this example consists of the ply 6A and the cords 10 therein are arranged radially at 90 degrees with respect to the tire equator. And an inner liner 9 made of a gas-impermeable rubber is disposed along the inside of the carcass 6 to face the tire cavity. However, in order to further decrease the tire weight, the inner liner 9 can be omitted as explained later.

During building a raw tire, the carcass ply 6A is formed by applying a sheet of rubberized carcass cords 10 around the tire building drum. The carcass cords 10 in the sheet are laid parallel with each other. Each side of the sheet is covered with a topping rubber 12 (thickness t').

According to the present invention, the carcass cords 10 in the sheet include main cords 10M and auxiliary cords 10S which alternate in the longitudinal direction of the sheet. In the finished tire, accordingly, the main cords 10M and auxiliary cords 10S in the carcass ply 6A alternate in the circumferential direction of the tire. Between the adjacent main cords 10M, one to three auxiliary cords 10S are arranged.

  • Fig.2 shows an example in which one auxiliary cord 10S is disposed between the main cords 10M.
  • Fig.3 shows an example in which two auxiliary cords 10S are disposed between the main cords 10M.

The main cords 10M are for providing support to the tire inner pressure and tire load. In other words, the main function of the main cords 10M is to reinforce the carcass ply. On the other hand. the auxiliary cords 10S are for controlling the outflow of the topping rubber 12 during vulcanization.

In order to achieve a tire weight reduction while maintaining the strength necessary for the carcass ply, a high-strength, high-modulus cord is used as the main cords 10M and the cord count of the main cords 10M is decreased.

Given that a strength index is the product Tm X Km of the cord strength Tm (N) of the main cord 10M and the cord count Km of the main cords 10M per 5 cm ply width, usually, the strength index is set in a range of from 4,000 to 20,000 N/5 cm in case of passenger car tires, and in case of heavy duty tires for trucks and buses, the strength index is set in a range of from 15,000 to 100,000 N/5 cm. It is preferable that the cord strength Tm is not less than 140 (N) in case of a passenger car tire, and in case of heavy duty tire for trucks and buses, the cord strength Tm is not less than 800 (N).

Incidentally, the cord strength Tm may be increased by increasing the cord thickness Dm and/or using a material superior in the rupture strength.

Therefore, it becomes possible to minimize the strength of the auxiliary cord as far as the auxiliary cords can prevent the outflow of the topping rubber. Thus, the auxiliary cords may have a less strength and/or less thickness than the main cords. For example, in case of the passenger car tires in which organic fiber material, e.g. nylon, polyester, rayon and the like is conventionally used in the carcass cords, the strength can be increased by 1) increasing the cord thickness Dm, 2) using high-strength, high-modulus organic fiber material such as high-modulus polyethylene, high-modulus vinylon, aromatic polyamide, polyolefin ketone and the like, or steel fiber material, and/or 3) changing the cord structure.

In case of the heavy duty tires in which steel cords are conventionally used as the carcass cords, the strength can be increased by 1) increasing the cord thickness Dm and/or 2) changing the cord construction.

As explained above, the main function of the auxiliary cords 10s is to control the outflow of rubber during vulcanization. Therefore, the cord strength Ts thereof can be decreased to under the cord strength Tm of the main cord 10M. Further, in view of the material cost and weight reduction, it is preferable that the product Ts X Ks of the cord strength Ts and the number Ks (= 1, 2 or 3) of the auxiliary cord(s) 10s between the main cords 10M is set in a range of not more than 0.3 times, more preferably not more than 0.2 times, still more preferably not more than 0.15 times the cord strength Tm.

Incidentally, the cord strength Ts of the auxiliary cord 10S can be decreased by making the cord thickness Ds smaller than the main cords 10M and/or employing a material having a smaller rupture strength.

When the cord strength Ts is decreased by only decreasing the cord thickness Ds, it is preferable that the cord thickness Ds is set in a range of from 0.1 to 0.67 times, more preferably 0.1 to 0.4 times the cord thickness Dm of the main cords 10M. If the thickness Ds is more than 0.67 times the thickness Dm, the tire weight increases contrary to the purpose of the present invention. If the thickness Ds is less than 0.1 times the thickness Dm, it becomes difficult to control the outflow of the topping rubber.

Further, in order to effectively prevent the outflow of the topping rubber, the cord count of the carcass cords 10 (inclusive of 10M and 10S) is determined such that the gaps L therebetween are within a range of from 0.02 to 0.80 mm and substantially constant.

If the gaps L are more than 0.80 mm, the outflow is liable to occur. If the gaps L are less than 0.02 mm, fretting wear is liable to be caused between the adjacent cords and separation from the toping rubber tends to occur.

The above-mentioned inner liner 9 is made of air-impermeable rubber and extends over the tire inner surface facing the tire cavity with a substantially constant thickness. As the air-impermeable rubber, used is a butyl rubber compound including not less than 20 weight % of butyl rubber and/or halogenated butyl rubber as its base rubber material. A diene rubber can be used as the remaining part of the base rubber material, if any. In the air-impermeable rubber compound, a halogenide of isobutylene-paramethyl styrene copolymer can be also used instead of the butyl rubber and/or halogenated butyl rubber.

As mentioned before, in order to further reduce the tire weight, it is preferable that the air-impermeable rubber is used as the topping rubber 12 for the carcass ply 6A and the inner liner rubber 9 is omitted. In this case, it is possible that the air-impermeable rubber is used only in an inside part of the topping rubber facing the tire cavity, and in the outside part, a different rubber compound, e.g. diene rubber and the like is used.

The above-mentioned belt includes a breaker 7 and optional band disposed radially outside the breaker 7. The breaker 7 comprises at least two cross plies 7A and 7B of cords laid parallel with each other at an angle of from 10 to 35 degrees with respect to the tire equator. For the breaker cords, steel cords and high performance organic fiber cords such as aromatic polyamide and the like can be suitably used. In this example which is a passenger car radial tire, the belt 7 is composed of two cross breaker plies ply 7A and 7B. In case of heavy duty tire, the breaker 7 composed of three or four plies is usually used.

Comparison Tests

Radial tires having a tire size of 195/65R14 for passenger cars and a tire size of 11R22.5 for trucks and buses were made and tested as follows.

The test tires were disassembled, and the thickness of the carcass topping rubber covering the carcass cords was measured as the thickness t after the tire vulcanization and the thickness (t) is shown in Table 1 together with the thickness (t') before vulcanization.

Further, undulation of the carcass topping rubber due to the outflow during vulcanization was visually observed. According to the position of the boundary between the carcass topping rubber and inner liner rubber, the degree of undulation was ranked as follows.

  • A: The undulation was not observed.
  • B: The boundary did not run out beyond the inner ends of the cords as shown in Fig.4.
  • C: The boundary ran out to a position between the inner ends of the cords and the cord center line H.
  • D: The boundary ran out beyond the cord center line H as shown in Fig. 5.

The test results and the specifications of the carcass ply are shown in Table 1. The cord thickness and cord strength were measured according to Japanese Industrial Standard (JIS) L-1017 in case of organic fiber cords and JIS G-3510 in case of steel cords. Table 1 Tire Ref.A Ex.A Ref.B Ex.B Tire size 195/65R14 195/65R14 11R22.5 11R22.5 Carcass ply Fig.5 Fig.2 Fig.5 Fig.3 Main cord 1100dtex//2/2 1100dtex//12/2 3+8+13X0.175 3+8+13X0.175 Material HM polyester HM polyester steel steel Strength Tm (N) 280 280 1510 1510 Thickness Dm (mm) 0.78 0.78 1.05 1.05 Count Km /5cm 45 45 26 26 Tm X Km (N) 12600 12600 39260 39260 Auxiliary cord -- 490dtex -- 1X3X0.175 Material -- 6-nylon -- steel Strength Ts (N) -- 29 -- 189 Thickness Ds (mm) -- 0.3 -- 0.37 Number Ks -- 1 -- 2 (Ts X Ks)/Tm -- 0.1 -- 0.25 Gap L (mm) 0.7 0.02 0.87 0.24 Ds/Dm -- 0.38 -- 0.35 Undulation C A D B Thickness t (after) (mm) 0.17 0.23 0.4 0.65 t' (before) (mm) 0.26 0.26 0.85 0.85


Anspruch[de]
Luftreifen (1), umfassend

einen Laufflächenabschnitt (2),

ein Paar Seitenwandabschnitte (3),

ein Paar Wulstabschnitte (4),

eine Karkasslage (6A) aus Korden (10), die sich zwischen den Wulstabschnitten (4) durch den Laufflächenabschnitt (2) und die Seitenwandabschnitte (3) erstreckt,

wobei die Karkasskorde (10) Hauptkorde (10M) für einen Verstärkungszweck und Zusatzkorde (10S) zum Steuern der Ausströmung von Gummierungsgummi (12) während der Reifenvulkanisierung umfassen,

die Hauptkorde (10M) und Zusatzkorde (10S) abwechselnd in der Umfangsrichtung des Reifens angeordnet sind, und

die Zusatzkorde (10S) eine Dicke (Ds) in einem Bereich des 0,1 bis 0,67-fachen der Dicke (Dm) der Hauptkorde (10M) aufweisen,

dadurch gekennzeichnet, dass

die Anzahl von Zusatzkord(en) (10S) zwischen jeweils zwei benachbarten Hauptkorden (10M) in einem Bereich von eins bis drei liegt.
Luftreifen (1) nach Anspruch 1, wobei

die Zwischenräume (L) zwischen den Karkasskorden (10) in einem Bereich von 0,02 bis 0,80 mm liegen.
Luftreifen (1) nach Anspruch 1, wobei

die Hauptkorde (10M) und (10S) ein organischer Kord sind.
Luftreifen (1) nach Anspruch 1, wobei

die Hauptkorde (10M) ein Polyesterkord sind und die Zusatzkorde (10S) ein Nylonkord sind.
Luftreifen (1) nach Anspruch 1, wobei

die Hauptkorde (10M) und die Zusatzkorde (10S) ein Stahlkord sind.
Luftreifen (1) nach Anspruch 1, wobei

die Hauptkorde (10M) ein Stahlkord sind und die Zusatzkorde (10S) ein organischer Kord sind.
Luftreifen (1) nach Anspruch 1, wobei

eine luftundurchlässige Kautschukmischung als ein Gummierungsgummi (12) für die Karkasslage (6A) verwendet wird.
Anspruch[en]
A pneumatic tire (1) comprising

a tread portion (2),

a pair of sidewall portions (3),

a pair of bead portions (4),

a carcass ply (6A) of cords (10) extending between the bead portions (4) through the tread portion (2) and sidewall portions (3), wherein

the carcass cords (10) include main cords (10M) for reinforcing purpose and auxiliary cords (10S) for controlling outflow of topping rubber (12) during tire vulcanization,

the main cords (10M) and auxiliary cords (10S) are arranged alternately in the tire circumferential direction,

the auxiliary cords (10S) have a thickness (Ds) in a range of from 0.1 to 0.67 times the thickness (Dm) of the main cords (10M)

characterized in that the number of auxiliary cord(s) (10S) between every two adjacent main cords (10M) is in a range of from one to three.
A pneumatic tire (1) according to claim 1, wherein

the gaps (L) between the carcass cords (10) are in a range of from 0.02 to 0.80 mm.
A pneumatic tire (1) according to claim 1, wherein

the main cords (10M) and the auxiliary cords (10S) are an organic cord.
A pneumatic tire (1) according to claim 1, wherein

the main cords (10M) are a polyester cord,

and the auxiliary cords (10S) are a nylon cord.
A pneumatic tire (1) according to claim 1, wherein

the main cords (10M) and the auxiliary cords (10S) are a steel cord.
A pneumatic tire (1) according to claim 1, wherein

the main cords (10M) are a steel cord, and

the auxiliary cords (10S) are an organic cord.
A pneumatic tire (1) according to claim 1, wherein

an air-impermeable rubber compound is used as a topping rubber (12) for the carcass ply (6A).
Anspruch[fr]
Bandage pneumatique (1) comprenant : une partie de bande de roulement (2), une paire de parties de paroi latérale (3), une paire de parties de talon (4), un pli de carcasse (6A) de cordes (10) s'étendant entre les parties de talon (4) en passant par la partie de bande de roulement (2) et les parties de paroi latérale (3), les cordes (10) de carcasse comprenant des cordes principales (10M) pour un but de renforcement et des cordes auxiliaires (10S) pour contrôler l'écoulement des couches de gomme (12) pendant la vulcanisation du bandage, les cordes principales (10M) et les cordes auxiliaires (10S) étant agencées de manière alternée dans la direction circonférentielle du bandage, les cordes auxiliaires (10S) ayant une épaisseur (Ds) allant de 0,1 à 0,67 fois l'épaisseur (Dm) des cordes principales (10M), caractérisé en ce que le nombre de corde(s) auxiliaire(s) (10S) entre deux cordes principales (10M) adjacentes est de l'ordre de un à trois. Bandage pneumatique (1) selon la revendication 1, dans lequel les espaces (L) entre les cordes (10) de carcasse sont de l'ordre de 0,02 à 0,80 mm. Bandage pneumatique (1) selon la revendication 1, dans lequel les cordes principales (10M) et les cordes auxiliaires (10S) sont une corde organique. Bandage pneumatique (1) selon la revendication 1, dans lequel les cordes principales (10M) sont une corde en polyester, et les cordes auxiliaires (10S) sont une corde en nylon. Bandage pneumatique (1) selon la revendication 1, dans lequel les cordes principales (10M) et les cordes auxiliaires (10S) sont une corde en acier. Bandage pneumatique (1) selon la revendication 1, dans lequel les cordes principales (10M) sont une corde en acier et les cordes auxiliaires (10S) sont une corde organique. Bandage pneumatique (1) selon la revendication 1, dans lequel on utilise un composant en caoutchouc imperméable à l'air en tant que couche de caoutchouc (12) pour le pli de carcasse (6A).






IPC
A Täglicher Lebensbedarf
B Arbeitsverfahren; Transportieren
C Chemie; Hüttenwesen
D Textilien; Papier
E Bauwesen; Erdbohren; Bergbau
F Maschinenbau; Beleuchtung; Heizung; Waffen; Sprengen
G Physik
H Elektrotechnik

Anmelder
Datum

Patentrecherche

Patent Zeichnungen (PDF)

Copyright © 2008 Patent-De Alle Rechte vorbehalten. eMail: info@patent-de.com