JP7400240B2 - pneumatic tires - Google Patents

Description

The present invention relates to pneumatic tires. In particular, the present invention relates to pneumatic tires with bands.

A typical pneumatic tire has a band between the tread and the belt. This band has a cord and a topping rubber. This cord is wound substantially circumferentially. This cord restrains the belt. When driving at high speeds, centrifugal force acts on the belt. Since the cord of the band restrains the belt, lifting does not occur even if centrifugal force is applied to the belt. This tire has excellent durability. The band can also contribute to the quietness, handling stability, etc. of the tire. A tire having a band is disclosed in JP-A No. 2008-49880.

Japanese Patent Application Publication No. 2008-49880

When tires are used in harsh conditions, localized delamination occurs between the band cords and the tread. A tire with delamination is no longer usable. A tire that is less likely to peel off is desired.

An object of the present invention is to provide a pneumatic tire with excellent durability.

A pneumatic tire according to the present invention has a tread, a pair of sidewalls, a pair of beads, a carcass, and a band. Each sidewall extends radially generally inwardly from the end of the tread. Each bead is located axially more inward than the sidewall. The carcass spans between one bead and the other along the inside of the tread and the sidewalls. The band is located between the carcass and the tread, and the tread is laminated to this band. The band includes a cord made of organic fiber and a topping rubber that covers the cord. The distance L between this cord and the tread is greater than 0.05 mm.

Preferably, the cords of the band are made of one or more fibers selected from the group consisting of polyethylene terephthalate fibers, polyethylene naphthalate fibers, aramid fibers, nylon fibers, and rayon fibers. Preferably, the cord consists of polyethylene terephthalate fibers.

Preferably, the distance L is 0.15 mm or more.

Preferably, the ratio (L/M) between the distance L (mm) and the tensile modulus M (MPa) of the cord of the band is 1.3×10 ⁻⁵ or more.

In the pneumatic tire according to the present invention, separation between the band cord and the tread is less likely to occur. This tire has excellent durability.

FIG. 1 is a sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a perspective view of a portion of the ribbon for the tire band of FIG. 1; FIG. 3 is an enlarged view of a portion of the tire of FIG. 1. FIG. 4 is an enlarged view of a portion of the tire of FIG. 3.

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

In FIG. 1, a pneumatic tire 2 is shown. In FIG. 1, the up-down direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, a dashed line CL represents the equatorial plane of the tire 2. The shape of this tire 2 is symmetrical with respect to the equatorial plane CL, except for the tread pattern.

This tire 2 has a tread 4, a pair of wings 6, a pair of sidewalls 8, a pair of clinchers 10, a pair of beads 12, a carcass 14, a belt 16, a band 18, an inner liner 20, and a pair of chafers 22. ing. This tire 2 is a tubeless type. This tire 2 is mounted on a passenger car.

The tread 4 has a radially outwardly convex shape. The tread 4 forms a tread surface 24 that contacts the road surface. A groove 26 is cut into the tread 4. The grooves 26 form a tread pattern. The tread 4 has a base layer 28 and a cap layer 30. Cap layer 30 is located radially outward of base layer 28 . The cap layer 30 is laminated to the base layer 28. The base layer 28 is made of crosslinked rubber with excellent adhesive properties. A typical base rubber for base layer 28 is natural rubber. The cap layer 30 is made of crosslinked rubber that has excellent abrasion resistance, heat resistance, and grip properties. The tread 4 may have an undertread layer. An undertread layer may be located between base layer 28 and band 18.

The complex elastic modulus E ^* 1 of the base layer 28 is preferably 1 MPa or more and 15 MPa or less, particularly preferably 2 MPa or more and 8 MPa or less. The complex modulus of elasticity E ^* 1 is measured in accordance with the regulations of "JIS K 6394". The measurement conditions are as follows.
Viscoelastic spectrometer: Iwamoto Seisakusho's "VESF-3"
Initial distortion: 10%
Dynamic distortion: ±1%
Frequency: 10Hz
Deformation mode: Tension Measurement temperature: 70℃

Each sidewall 8 extends substantially inward in the radial direction from the end of the tread 4. A radially outer end of the sidewall 8 is joined to the tread 4. A radially inner end of this sidewall 8 is joined to a clinch 10. This sidewall 8 is made of crosslinked rubber with excellent cut resistance and weather resistance. This sidewall 8 prevents damage to the carcass 14.

Each clinch 10 is located substantially inside the sidewall 8 in the radial direction. The clinch 10 is located outside the bead 12 and carcass 14 in the axial direction. The clinch 10 is made of crosslinked rubber with excellent wear resistance. The clinch 10 abuts the flange of the rim on which the tire 2 will be mounted.

Each bead 12 is located inside the clinch 10 in the axial direction. Bead 12 includes a core 32 and an apex 34 extending radially outwardly from core 32 . Core 32 is ring-shaped and includes a wound non-stretchable wire. A typical material for wire is steel. Apex 34 tapers radially outward. Apex 34 is made of highly hard crosslinked rubber.

The carcass 14 spans between the beads 12 on both sides and runs along the tread 4 and sidewalls 8. The carcass 14 is folded back around the core 32 from the inside in the axial direction to the outside. By this folding, a main portion 36 and a folded portion 38 are formed in the carcass 14.

Although not shown, the carcass 14 is made up of a large number of parallel cords and topping rubber. The absolute value of the angle that each cord makes with respect to the equatorial plane is from 75° to 90°. In other words, this carcass 14 has a radial structure. The cord is made of organic fibers. Examples of preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. Carcass 14 may have two or more layers.

The belt 16 is located inside the tread 4 in the radial direction. The belt 16 is laminated with the carcass 14. Belt 16 reinforces carcass 14. Belt 16 consists of an inner layer 40 and an outer layer 42. As is clear from FIG. 1, in the axial direction, the width of the inner layer 40 is slightly larger than the width of the outer layer 42. Although not shown, each of the inner layer 40 and the outer layer 42 consists of a large number of parallel cords and topping rubber. Each cord is tilted with respect to the equatorial plane. The general absolute value of the inclination angle is 10° or more and 35° or less. The direction of inclination of the cords of the inner layer 40 with respect to the equatorial plane is opposite to the direction of inclination of the cords of the outer layer 42 with respect to the equatorial plane. The preferred material for the cord is steel. Organic fibers may be used for the cord. The axial width of the belt 16 is preferably 0.7 times or more the maximum width of the tire 2. Belt 16 may have three or more layers.

Band 18 is located radially outward of belt 16. In the axial direction, the width of band 18 is greater than the width of belt 16. Band 18 covers the entire belt 16.

Belt 16 and band 18 constitute a reinforcing layer. The reinforcing layer may be composed only of the band 18.

Inner liner 20 is located inside carcass 14. Inner liner 20 is joined to the inner surface of carcass 14. The inner liner 20 is made of crosslinked rubber with excellent air shielding properties. A typical base rubber for inner liner 20 is butyl rubber or halogenated butyl rubber. The inner liner 20 maintains the internal pressure of the tire 2.

Each chafer 22 is located near the bead 12. When the tire 2 is installed on the rim, the chafer 22 comes into contact with the rim. This contact protects the vicinity of the bead 12. Although not shown, the chafer 22 is made of cloth and rubber impregnated into the cloth.

FIG. 2 is a perspective view of a portion of the ribbon 44 for the band 18 of the tire 2 of FIG. The ribbon 44 includes a topping rubber 46 and two cords 48. The band 18 is formed by winding the ribbon 44 spirally onto the belt 16. Since ribbon 44 is helical, cord 48 is also helical. This band 18 has a so-called jointless structure. Cord 48 extends substantially circumferentially. Since the belt 16 is restrained by the cord 48, lifting of the belt 16 is suppressed. Ribbon 44 may have three or more cords 48.

As described above, the cord 48 is wound spirally, so strictly speaking, the cord 48 is slightly inclined with respect to the circumferential direction. The absolute value of the angle between the cord 48 and the circumferential direction is 5.0° or less. In the present invention, a direction in which the absolute value of the angle with respect to the circumferential direction is 5.0 degrees or less is defined as a "substantive circumferential direction." The absolute value of the angle between the cord 48 and the circumferential direction is preferably 2.0° or less.

FIG. 3 is an enlarged view showing a part of the tire 2 of FIG. 1. FIG. In FIG. 3, base layer 28 and band 18 are shown. By spirally winding the ribbon 44 described above, a band 18 is formed which is made up of a cord 48 and a topping rubber 46 that covers the cord 48. The base layer 28 and the band 18 are directly laminated.

The topping rubber 46 is obtained by crosslinking a rubber composition. As the base rubber of the rubber composition, polyisoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR) can be used. Conjugated diene polymers; and non-diene polymers such as ethylene propylene diene rubber (EPDM), butyl rubber (IIR) and halogenated butyl rubber (X-IIR). Two or more types of rubber may be used in combination. Polyisoprene rubber and SBR are preferred because they have excellent mechanical strength, reversion resistance, heat resistance, and crack growth resistance.

Examples of polyisoprene rubber include isoprene rubber (IR), natural rubber (NR), and modified natural rubber. NR includes deproteinized natural rubber (DPNR) and high purity natural rubber (HPNR). Modified natural rubbers include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Specific examples of NR include rubbers commonly used industrially, such as SIR20, RSS#3, and TSR20. Preferred polyisoprene rubbers are NR and IR. NR is particularly preferred because it has excellent elongation at break and strength at break.

Examples of styrene-butadiene rubber (SBR) include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), and modified SBR modified with 3-aminopropyldimethylmethoxysilane and the like. E-SBR is preferred because it contains a large amount of high molecular weight polymer components and has excellent elongation at break.

The content of the conjugated diene polymer in the total amount of the base rubber is preferably 10% by mass or more, more preferably 30% by mass or more, and particularly preferably 50% by mass or more. This content may be 100% by mass.

The content of polyisoprene rubber in the total amount of base rubber is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 30% by mass or more. This content is preferably 90% by mass or less, particularly preferably 70% by mass or less. A topping having a content within the above range has excellent adhesion to the cord 48.

Preferably, the rubber composition of topping rubber 46 contains sulfur. Sulfur crosslinks rubber molecules. Other crosslinking agents may be used with or in place of sulfur. Crosslinking may also be effected by electron beams.

Preferably, the rubber composition of topping rubber 46 includes a vulcanization accelerator along with sulfur. This rubber composition may contain a sulfenamide-based vulcanization accelerator, a guanidine-based vulcanization accelerator, a thiazole-based vulcanization accelerator, a thiuram-based vulcanization accelerator, a dithiocarbamate-based vulcanization accelerator, and the like.

The rubber composition includes a reinforcing agent. A typical reinforcing agent is carbon black. Examples of carbon black include Ketjen black, channel black, furnace black, acetylene black, and thermal black.

The rubber composition may include silica as a reinforcing agent instead of or in addition to carbon black. Examples of silica include dry process silica (anhydrous silicic acid) and wet process silica (hydrated silicic acid).

The rubber composition of the topping rubber 46 may include a softener. Preferred softeners include paraffinic process oils, naphthenic process oils, and aromatic process oils.

Stearic acid, zinc oxide, anti-aging agent, wax, crosslinking aid, etc. are added to the rubber composition of the topping rubber 46 as necessary.

The complex elastic modulus E ^* 2 of the topping rubber 46 is preferably 1 MPa or more and 15 MPa or less, particularly preferably 4 MPa or more and 11 MPa or less. This topping rubber 46 is difficult to separate from the cord 48. The complex modulus of elasticity E ^* 2 of the topping rubber 46 is measured in accordance with the regulations of "JIS K 6394." The measurement conditions are as follows.
Viscoelastic spectrometer: Iwamoto Seisakusho's "VESF-3"
Initial distortion: 10%
Dynamic distortion: ±1%
Frequency: 10Hz
Deformation mode: Tension Measurement temperature: 70℃

The cord 48 is made of organic fiber. Preferred organic fibers include polyethylene terephthalate fibers, polyethylene naphthalate fibers, aramid fibers, nylon fibers, and rayon fibers. Two or more organic fibers may be used in combination.

A particularly preferred organic fiber is polyethylene terephthalate fiber (PET fiber). The cord 48 made of polyethylene terephthalate fiber has a high elastic modulus. This cord 48 can contribute to high-speed durability and quietness of the tire 2.

The cord 48 made of polyethylene terephthalate fiber is typically obtained by twisting two first-twisted cords. As a pre-twisted cord,
(1) Pre-twisted cord made by twisting two multifilaments each with a fineness of 1100 dtex (1100 dtex/2)
(2) Pre-twisted cord made of three multifilaments each having a fineness of 1100 dtex (1100 dtex/3)
(3) Pre-twisted cord made by twisting two multifilaments each with a fineness of 1670 dtex (1670 dtex/2)
is exemplified.

The density of the cords 48 in the band 18 is preferably 30 ends/5 cm or more. This band 18 can restrain the belt 16 well. From this point of view, the density is more preferably 32 ends/5 cm or more, particularly preferably 34 ends/5 cm or more. This density is preferably 45 ends/5 cm or less. Density is the number of cord 48 sections contained in a 5 cm wide band 18 section. This number is counted in a direction perpendicular to the direction in which the cord 48 extends.

FIG. 4 is an enlarged view showing a part of the tire 2 of FIG. 3. As shown in FIG. In FIG. 4, base layer 28 and band 18 are shown. In FIG. 4, the symbol R is the thinnest region of the topping sandwiched between the cord 48 and the tread 4. Arrow L indicates the thickness of region R. In other words, the arrow L is the distance between the cord 48 and the tread 4. In this embodiment, a distance L is measured between the cord 48 and the base layer 28. For tires with an undertread, the distance L is measured between the cord 48 and the undertread. The distance L is measured in a cross section of a test piece obtained by cutting the tire 2. In the tire 2 according to the invention, the distance L is greater than 0.05 mm.

Due to the difference between the elastic modulus of the cord 48 and the elastic modulus of the topping rubber 46, stress is concentrated at the interface between the cord 48 and the topping rubber 46. Due to the difference in the elastic modulus of the topping rubber 46 and the base layer 28, stress is concentrated at the interface between the topping rubber 46 and the base layer 28. When the interface between the cord 48 and the topping rubber 46 is close to the interface between the topping rubber 46 and the base layer 28, excessive stress is concentrated in the region R, and the topping rubber 46 in the region R peels off from the cord 48. In the tire 2 according to the present invention, since the distance L is greater than 0.05 mm, stress is dispersed. In this tire 2, peeling of the topping rubber 46 from the cord 48 is suppressed. This tire 2 has excellent durability.

From the viewpoint of durability, the distance L is more preferably 0.15 mm or more, particularly preferably 0.7 mm or more. From the viewpoint of reducing the weight of the tire 2, the distance L is preferably 2.0 mm or less, particularly preferably 1.5 mm or less.

The ratio (L/M) between the distance L (mm) and the tensile modulus M (MPa) of the cord 48 is preferably 1.3×10 ⁻⁵ or more. In the tire 2 in which the ratio (L/M) is within this range, even if the stress concentration due to the difference between the elastic modulus of the cord 48 and the elastic modulus of the topping rubber 46 is large, the topping rubber 46 is not affected by the stress from the cord 48. Peeling can be suppressed. From this point of view, the ratio (L/M) is more preferably 3.0×10 ⁻⁵ or more, particularly preferably 4.0×10 ⁻⁵ or more. The ratio (L/M) is preferably 1.0×10 ⁻³ or less.

The tensile modulus M of the cord 48 is preferably 3000 MPa or more. The cord 48 having a tensile modulus M within this range can contribute to the high-speed durability and quietness of the tire 2. From this viewpoint, the tensile modulus M is more preferably 6000 MPa or more, particularly preferably 9000 MPa or more. The tensile modulus M is preferably 15,000 MPa or less.

The tensile modulus M is measured by a constant load elongation test specified in "JIS L 1017". In the graph obtained from this measurement, the origin and the elongation rate under constant load are connected with a straight line, and the elastic modulus M is calculated based on the slope of this straight line. Measurements are made at a temperature of 23°C.

In manufacturing this tire 2, a plurality of rubber members are assembled to obtain a low cover (unvulcanized tire). This raw cover is put into a mold. The outer surface of the row cover contacts the cavity surface of the mold. The inner surface of the row cover abuts the bladder or tang. The raw cover is pressurized and heated within the mold. The rubber composition of the low cover flows due to pressurization and heating. The rubber undergoes a crosslinking reaction by heating, and the tire 2 is obtained.

In the present invention, unless otherwise specified, the dimensions and angles of each member of the tire 2 are measured with the tire 2 installed on a regular rim and filled with air to achieve the regular internal pressure. Ru. No load is applied to the tire 2 during the measurement. In this specification, a regular rim means a rim defined in the standard on which the tire 2 is based. A "standard rim" in the JATMA standard, a "Design Rim" in the TRA standard, and a "Measuring Rim" in the ETRTO standard are regular rims. In this specification, the normal internal pressure means the internal pressure defined in the standard on which the tire 2 is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures. In the case of the passenger car tire 2, the dimensions and angles are measured at an internal pressure of 180 kPa.

EXAMPLES Hereinafter, the effects of the present invention will be clarified through examples, but the present invention should not be interpreted in a limited manner based on the descriptions of these examples.

[Example 1]
A pneumatic tire having the structure shown in FIG. 1 was manufactured. The size of this tire is 225/45R17. In this tire, the base layer had a complex modulus of elasticity E ^* 1 of 3.0 MPa, and the topping rubber of the band had a complex modulus of elasticity E ^* 2 of 6.0 MPa. The cord of the band consists of polyethylene terephthalate fibers. The tensile modulus M of this cord was 7900 MPa. The distance L was 0.15 mm.

[Example 2-4 and Comparative Example 1]
Pneumatic tires of Examples 2-4 and Comparative Example 1 were obtained in the same manner as in Example 1, except that the distance L was changed as shown in Table 1 below.

[Example 5-8 and Comparative Example 2]
Pneumatic tires of Examples 5-8 and Comparative Example 2 were obtained in the same manner as in Example 1, except that a cord made of nylon fiber was used for the band and the distance L was as shown in Table 2 below. .

[Evaluation of adhesive strength]
A test piece having a circumferential length of 150 mm and a width direction length of 25 mm was taken from the tire. A cut was formed between the base layer and the band of this test piece to partially separate the base layer and the band. The base layer side and the band side, which were separated by the notch, were each sandwiched between parallel chucks of a tensile testing machine. The band side was pulled in the circumferential direction at a pulling speed of 50 mm/min, and the peel resistance (N/25 mm) was measured. The results are shown as indices in Tables 1 and 2 below.

As shown in Tables 1 and 2, the tires of each example have excellent adhesive strength. From this evaluation result, the superiority of the present invention is clear.

The pneumatic tire according to the present invention can be mounted on various vehicles.

2... Pneumatic tire 4... Tread 6... Wing 8... Sidewall 10... Clinch 12... Bead 14... Carcass 16... Belt 18... Band 20. ... Inner liner 22 ... Chafer 28 ... Base layer 30 ... Cap layer 44 ... Ribbon 46 ... Topping rubber 48 ... Band cord

Claims (5)

It has a tread, a pair of sidewalls, a pair of beads, a carcass and a band.
each sidewall extending generally radially inward from an end of the tread;
Each bead is located axially more inward than the sidewall,
The carcass is spanned between one bead and the other bead along the inside of the tread and the sidewall,
The band is located between the carcass and the tread, and the tread is laminated on the band,
The band includes a cord having a tensile modulus M of 6000 MPa or more, and a topping rubber that covers the cord,
The distance L between the cord and the tread is 0.15 mm or more,
A pneumatic tire in which the ratio (L/M) between the distance L (mm) and the tensile modulus M (MPa) of the cord is 1.3×10 ⁻⁵ or more. The pneumatic tire according to claim 1, wherein the cord is made of one or more types of fibers selected from the group consisting of polyethylene terephthalate fibers, polyethylene naphthalate fibers, aramid fibers, nylon fibers, and rayon fibers. It has a tread, a pair of sidewalls, a pair of beads, a carcass and a band.
each sidewall extending generally radially inward from an end of the tread;
Each bead is located axially more inward than the sidewall,
The carcass is spanned between one bead and the other bead along the inside of the tread and the sidewall,
The band is located between the carcass and the tread, and the tread is laminated on the band,
The band includes a cord having a tensile modulus M of 6000 MPa or more, and a topping rubber that covers the cord,
The distance L between the cord and the tread is greater than 0.05 mm,
The ratio (L/M) between the distance L (mm) and the tensile modulus M (MPa) of the cord is 1.3×10 ⁻⁵ or more,
A pneumatic tire in which the above cord is made of polyethylene terephthalate fiber. It has a tread, a pair of sidewalls, a pair of beads, a carcass and a band.
each sidewall extending generally radially inward from an end of the tread;
Each bead is located axially more inward than the sidewall,
The carcass is spanned between one bead and the other bead along the inside of the tread and the sidewall,
The band is located between the carcass and the tread, and the tread is laminated on the band,
The band includes a cord made of polyethylene terephthalate fiber and a topping rubber that covers the cord,
The distance L between the cord and the tread is greater than 0.05 mm,
A pneumatic tire in which the ratio (L/M) between the distance L (mm) and the tensile modulus M (MPa) of the cord is 1.3×10 ⁻⁵ or more. The pneumatic tire according to claim 4, wherein the distance L is 0.15 mm or more.

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