CN106956550B

CN106956550B - Pneumatic tire

Info

Publication number: CN106956550B
Application number: CN201611168828.3A
Authority: CN
Inventors: 高桥伸吾; 西实
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 2016-01-08
Filing date: 2016-12-16
Publication date: 2020-02-21
Anticipated expiration: 2036-12-16
Also published as: JP6607046B2; JP2017121893A; CN106956550A

Abstract

The invention provides a pneumatic tire which not only prevents the core of the tire bead from rusting, but also achieves the improvement of the durability. The pneumatic tire includes: the inner liner, prevent rubbing gum, overlap joint portion, core and protective layer. The protective layer is joined to an end of the inner liner layer and is positioned between the core and the rub-resistant compound. The protective layer has: a first end located at a joint portion between the protective layer and the inner liner layer; a second end located radially inward of the core. The bottom surface of the core extends in a generally axial direction. The second end is located between an inboard end of the bottom surface and an outboard end of the bottom surface in the axial direction. The rubber composition for the protective layer contains a base material rubber containing butyl rubber. The ratio of the butyl rubber to the total amount of the base rubber is 65 mass% to 90 mass%.

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire. More specifically, the present invention relates to a heavy duty pneumatic tire mounted on a bus, truck, or the like.

Background

An innerliner is provided in the tire. The inner liner layer is located inside the tire and functions to maintain the internal pressure.

The inner liner is made of a crosslinked rubber produced using a rubber composition. The rubber composition of the inner liner as a base material rubber usually includes butyl rubber. Butyl rubber is known as a rubber which is difficult to permeate gas such as air.

The tire is composed of a plurality of rubber members in combination. The adhesion properties of the respective rubber components are important. Butyl rubber not only contributes to air tightness, i.e. leakage resistance, but also affects the adhesion properties. The inner liner including the butyl rubber has a problem that it is difficult to bond the inner liner to other rubbers. For this reason, various studies have been made on joining of the inner liner layer. And an example of the study is disclosed by japanese patent application laid-open No. 2008-126745.

Patent document 1: japanese patent laid-open No. 2008-126745

Disclosure of Invention

When assembling a tire to a rim, the bead portion of the tire is placed on the bead seat of the rim. When air is filled into the interior of the tire, the bead portion slides axially outward along the bead seat. The bead portion is in contact with a flange of the rim. Thereby, the assembly of the tire to the rim is completed.

A heavy duty tire may be configured to have a rim with a bead seat inclined with respect to an axial direction. The inclination angle of the bead seats of this rim is typically 15 °. When the tire is assembled to the rim, the toe-in portion of the tire floats from the bead seat. Since a gap is formed between the tire and the bead seat, moisture or oxygen may penetrate into the tire from the gap.

A core is provided in a bead portion of a tire. The core typically uses steel wire. For this reason, when moisture or the like penetrates, the core may be rusted. There is also a ply in the bead portion. Steel cords are generally used as carcass cords of the carcass ply for heavy duty tires. Therefore, when moisture or the like penetrates, rust may also develop on the carcass cord.

In order to prevent rusting, an inner liner layer may be provided at the gas permeation portion. But, as previously mentioned, the inner liner has poor adhesion properties. Therefore, depending on the position where the inner liner is disposed, the inner liner may be peeled off. This peeling affects productivity during the manufacture of the tire. Moreover, the peeling affects the durability of the tire.

The invention aims to provide a pneumatic tire which not only prevents a bead core from rusting, but also achieves the purpose of improving the durability.

The pneumatic tire of the present invention includes: an inner liner for maintaining an internal pressure; the anti-friction rubber is placed on a bead seat of the rim; a lap joint portion that contacts a flange of the rim; a core located outside the rubbing gum in a radial direction; a protective layer joined to an end of the inner liner layer and located between the core and the rub-resistant compound, the protective layer having: a first end located at a joint portion between the protective layer and the lining layer; a second end located radially inward of the core. The core includes a bottom surface that is opposed to the bead seat when the tire is assembled to the rim, the bottom surface extending in a substantially axial direction in a cross section of the tire along a plane containing a center axis of the tire. The second end is located between an inboard end of the bottom surface and an outboard end of the bottom surface in the axial direction. The protective layer is composed of a crosslinked rubber formed from a rubber composition. The rubber composition includes a base material rubber including butyl rubber. The ratio of the butyl rubber to the total amount of the base rubber is 65 mass% to 90 mass%.

Preferably, the protective layer of the pneumatic tire has a thickness of 0.4mm to 1.5 mm.

Preferably, the first end of the pneumatic tire is located radially outward of the axially inner end of the core. More preferably, the distance in the radial direction from the axially inner end of the core to the first end of the pneumatic tire is 3mm to 15 mm.

Preferably, in the pneumatic tire, a ratio of the thickness of the protective layer to the thickness of the joint portion is 50% to 90%.

Preferably, the pneumatic tire includes a protective layer engaged with an end portion of the inner liner and located between the core and the chafer. The protective layer has: a first end located at a joint portion between the protective layer and the inner liner layer; and a second end located radially inward of the core.

In this pneumatic tire, the protective layer is made of a crosslinked rubber formed from a rubber composition. The rubber composition comprises a base material rubber, and the base material rubber comprises butyl rubber. The protective layer contributes to the leakage resistance.

The second end of the protective layer in the tire is located between the inboard end of the core bottom surface and the outboard end of the bottom surface. And the protective layer is arranged to overlap with a gap formed between the tire and the rim in a state where the tire is assembled to the rim. Since the protective layer contains butyl rubber, you can suppress the permeation of moisture or oxygen from the gap into the tire. Thereby preventing rusting in the core of the tire.

In this tire, the amount of butyl rubber contained in the rubber composition for the protective layer is appropriately adjusted. The protective layer is reliably joined to not only the inner liner but also the scrub resist. In other words, the protective layer helps prevent peeling of the inner liner and the scrub resist. Thereby preventing damage due to peeling of the inner liner or the rubbing in the tire. The tire has excellent durability.

The tire has no damage to the anti-leakage performance, not only prevents the core from rusting, but also achieves the improvement of the durability. According to the present invention, a pneumatic tire can be obtained which not only prevents the bead core from rusting, but also achieves improved durability.

Drawings

Fig. 1 is a partial sectional view of a pneumatic tire for illustrating an embodiment of the present invention.

Fig. 2 is an enlarged sectional view showing a part of the tire in fig. 1.

Description of reference numerals

2 … tyre

4 … tread

6 … sidewall

8 … lap joint

10 … rubbing gum

12 … tyre bead

14 … tyre body

18 … inner liner

24 … protective layer

24a … first body

24b … second body

30 … core

32 … apex

38 … ply

40 … main part

42 … folded back part

48 … end of the inner liner 18

52 … toe-in of tire 2

54 … wheel rim

58 … bead seat

60 … flange

62 … bottom surface of core 30

64 … first end

66 … second end

Detailed Description

The present invention will be described in detail based on preferred embodiments with reference to the accompanying drawings as appropriate.

Fig. 1 shows a pneumatic tire 2. Specifically, fig. 1 shows a partial cross section of the tire 2 along a plane including the central axis of the tire 2. The vertical direction in fig. 1 is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper plane is the circumferential direction of the tire 2. The chain line CL in fig. 1 indicates the equatorial plane of the tire 2. The tire 2 has a shape symmetrical with respect to the equatorial plane except for the tread pattern.

The tire 2 includes: a tread 4, a pair of sidewalls 6, a pair of clinchs 8, a pair of chafers 10, a pair of beads 12, a carcass 14, a belt 16, an innerliner 18, a barrier layer 20, a pair of fillers 22, and a pair of protective layers 24. The tire 2 is a tubeless tire. The tire 2 is mounted on a truck, a bus, or the like. The tire 2 is a heavy duty tire.

The tread 4 is convex outward in the radial direction. The tread 4 forms a tread surface 26 for contact with the road surface. Grooves 28 are cut in the tread 4. The grooves 28 form a tread pattern. The tread 4 is made of a crosslinked rubber. In this tread 4, wear resistance, heat resistance, and creep resistance are considered.

The sidewalls 6 extend from the ends of the tread 4 toward substantially the inner side in the radial direction. The sidewall 6 is located axially outward of the carcass 14. The sidewalls 6 are composed of a crosslinked rubber having excellent cut resistance and aging resistance. The sidewall 6 prevents damage to the carcass 14.

Each overlapping portion 8 is located substantially radially inward of the sidewall 6. The clinch 8 is located axially outside the bead 12 and carcass 14. The bridging portion 8 is composed of a crosslinked rubber having excellent wear resistance.

The chafers 10 are located adjacent to the beads 12, respectively. The scuff rubber 10 in this tire 2 extends from the end of the clinch portion 8 toward substantially the inside in the axial direction. The scuff guard 10 may also be integral with the bridge portion 8. The material of the rubbing preventive 10 is the same as that of the lapping part 8.

The beads 12 are located axially inward of the respective overlapping portions 8. The bead 12 includes a core 30 and an apex 32.

The core 30 is located radially outward of the chafer 10. The core 30 is annular. The core 30 comprises a coiled non-stretch wire. Specifically, the core 30 is configured such that a bundle 34 of wound non-stretchable wires is covered with a packing rubber 36. A typical material for the wire is steel.

Apex 32 extends radially outward from core 30. As shown in fig. 1, the apex 32 is pointed outward in the radial direction. The apex 32 is made of a crosslinked rubber having high hardness.

The carcass 14 includes a ply 38. The carcass 14 in the tire 2 is formed of a ply 38. The carcass 14 may be formed of two or more plies 38.

The ply 38 in this tire 2 spans between the beads 12 on both sides and along the inner side of the tread 4, sidewalls 6 and clinch 8. The ply 38 is folded back around the core 30 from the axially inboard side toward the outboard side. By this folding back, a main portion 40 and a folded-back portion 42 are formed in the ply 38. The ply 38 includes a main portion 40 and a turnback portion 42.

Although not shown, the plies 38 are respectively composed of a plurality of cords and topping rubbers juxtaposed. The cords are respectively angled at an absolute value of 75 DEG to 90 DEG from the equatorial plane. In other words, the carcass 14 has a radial structure. The material of the cord is steel. The ply 38 comprises steel cords.

In the tire 2, the end of the folded portion 42 is located between the outer end of the apex 32 and the core 30 in the radial direction. As described above, the tire 2 is mounted on a truck, a bus, or the like. A large load acts on the bead 12 portion of the tire 2. The end of the folded portion 42 tends to be strained. An intermediate layer 44 and a belt 46 are also provided in the bead 12 portion of the tire 2. These members suppress the concentration of strain toward the end of the folded-back portion 42.

The belt 16 is located radially inward of the tread 4. The belt 16 is laminated with the carcass 14. The belt 16 reinforces the carcass 14. The belt layer 16 in this tire 2 is composed of a first layer 16a, a second layer 16b, a third layer 16c, and a fourth layer 16 d. The belt 16 in this tire 2 is composed of 4 layers. The belt 16 may be composed of 3 or 2 layers.

As shown in fig. 1, the second layer 16b has the largest width among the first layer 16a, the second layer 16b, the third layer 16c, and the fourth layer 16d for constituting the belt layer 16 in the axial direction of the tire 2. And is a layer having the largest axial width among the layers constituting the belt layer 16 in the tire 2, that is, the end of the second layer 16b is the end of the belt layer 16. In this tire 2, the axial width of the belt layer 16 is represented by the axial width of the second layer 16 b. Preferably, the axial width of the belt 16 is 0.7 times or more the maximum width of the tire 2.

Although not shown, the first layer 16a, the second layer 16b, the third layer 16c, and the fourth layer 16d are respectively composed of a plurality of cords and topping rubbers juxtaposed. The material of the cord is steel. The belt 16 comprises steel cords. The cords in the layers are each inclined to the equatorial plane. The absolute values of the angles formed by the cords and the equatorial plane are 12 DEG to 70 DEG, respectively.

An inner liner 18 is positioned inside the carcass 14. The inner liner 18 is engaged with the inner surface of the carcass 14 via a barrier layer 20. The inner liner 18 is composed of a crosslinked rubber having excellent airtightness. A typical base material rubber for the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 maintains the internal pressure of the tire 2. In other words, the inner liner 18 contributes to the leakage resistance of the tire 2. The end 48 of the inner liner 18 in the tire 2 is located radially inward of the core 30. This ensures the internal pressure holding effect of the inner liner 18.

The insulation layer 20 is sandwiched between the carcass 14 and the inner liner 18. The spacer layer 20 is composed of a crosslinked rubber having excellent adhesive properties. The insulation layer 20 is not only strongly bonded to the carcass 14, but also to the inner liner 18. The barrier layer 20 prevents the inner liner 18 from peeling away from the carcass 14.

The fillers 22 are respectively located in the vicinity of the beads 12. The filler 22 is layered with the carcass 14. The filler 22 is folded back around the core 30 of the bead 12 radially inward of the carcass 14. Although not shown, the filler 22 is composed of a plurality of cords and topping rubber arranged side by side. The cords are respectively inclined with respect to the radial direction. The material of the cord is steel. The filler 22 inhibits local toppling of the bead 12. The filler 22 contributes to the endurance performance of the tire 2. In this tire 2, the end of the filler 22 is covered with the covering rubber 50.

The protective layers 24 are respectively located at the toe 52 portions of the tire 2. As shown in fig. 1, the protective layer 24 has an L-shape in cross section of the tire 2. The protective layer 24 is composed of a portion extending radially outward from the portion of the front bundle 52 (hereinafter also referred to as a first body 24a) and a portion extending axially substantially outward (hereinafter also referred to as a second body 24 b).

The protective layer 24 in the tire 2 is made of a crosslinked rubber formed of a rubber composition. And the rubber composition contains a base material rubber. The main component of the base rubber in the tire 2 is butyl rubber. In other words, the main component of the base material rubber contains butyl rubber.

The base material rubber in this tire 2 includes, in addition to the butyl rubber, other rubbers such as natural rubber, synthetic natural rubber, ethylene propylene diene rubber, and the like. From the viewpoint of tackiness, natural rubber is preferable as the other rubber.

The rubber composition for the protective layer 24 contains a reinforcing agent. A typical reinforcing agent is carbon black. FEF, GPF, HAF, ISAF, SAF, etc. may be used. From the viewpoint of the strength of the protective layer 24, the amount of carbon black is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, with respect to the mass part of the base rubber 100. From the viewpoint of flexibility of the protective layer 24, the amount of carbon black is preferably 70 parts by mass or less, and more preferably 60 parts by mass or less. Silica may also be used with or in place of carbon black. At this time, dry silica and wet silica may be used.

The rubber composition used for the protective layer 24 may include, in addition to the reinforcing agent, a filler, a softener, a tackifier, a crosslinking agent such as sulfur, a vulcanization accelerator, a crosslinking assistant, an anti-aging agent, and the like. The rubber composition is formulated with the most appropriate chemicals in the most appropriate amount by taking into consideration the processability and performance of the tire 2.

Fig. 2 shows a portion of the bead 12 of the tire 2 in fig. 1. The vertical direction in fig. 2 is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper plane is the circumferential direction of the tire 2.

Fig. 2 also shows a rim 54 to which the tire 2 is assembled. The rim 54 is a regular rim. The tire 2 is assembled to the rim 54, and the tire 2 is filled with air so that the internal pressure of the tire 2 becomes a regular internal pressure.

The regular rim in the present specification means a rim specified by a specification to which the tire 2 conforms. For example, "standard Rim" in JATMA specification, "Design Rim" in TRA specification and "Measuring Rim" in ETRTO specification are regular rims.

The regular internal pressure in the present specification means an internal pressure defined by a specification to which the tire 2 conforms. The "maximum air PRESSURE" in the JATMA specification, "the" maximum value "described in" TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "in the TRA specification, and" INFLATION PRESSURE "in the ETRTO specification are normal internal PRESSURES.

In the present specification, unless otherwise specified, the dimensions and angles of the respective components of the tire 2 are measured in a state where the tire 2 is assembled on a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. No load was applied to the tire 2 at the time of measurement. In the case of the passenger tire 2, the dimension and angle may be measured in a state where the internal pressure is 180 kPa.

The rim 54 includes a pair of fitting portions 56. The beads 12 of the tire 2 are partially fitted in the fitting portions 56, respectively. The fitting portion 56 includes a bead seat 58 and a flange 60. The chafer 10 of the tire 2 is placed on the bead seat 58. The flange 60 is in contact with the clinch 8 of the tyre 2.

The bead seats 58 in the rim 54 shown in fig. 2 are inclined with respect to the axial direction. The inclination angle of the bead seat 58 is usually set to 15 °. The rim 54 in which the inclination angle of the bead seat 58 is set to 15 ° is also referred to as a 15 ° cone rim. This inclination angle is represented by an inclination angle of the surface of the bead seat 58 on the side of the scuff rubber 10.

The core 30 of the bead 12 in this tire 2 has a hexagonal cross section. The cross-section of the core 30 has six corners. For convenience of explanation of the present invention, symbols a, b, c, d, e and f are given to these corner portions in fig. 2. The corner b of the core 30 is an axially inner end of the core 30.

In this tire 2, the surface connecting the corner a and the corner f is the bottom surface 62 of the core 30. The bottom surface 62 is opposed to the bead seat 58. When the tire 2 is assembled to the rim 54, the core 30 of the tire 2 includes a bottom surface 62 that opposes the bead seat 58 of the rim 54. The section of the tyre 2 shown in figure 2 is along a plane containing the central axis of the tyre 2. In the cross section of the tire 2, the bottom surface 62 extends in a substantially axial direction. The corner a is an axially inner end of the bottom surface 62, and the corner f is an axially outer end of the bottom surface 62.

In fig. 2, symbol CE denotes one end of the contact surface between the tire 2 and the rim 54. As shown in fig. 2, the tire 2 does not contact the rim 54 in a portion inside the end CE in the axial direction. A gap is formed between the tire 2 and the rim 54 at a portion axially inward of the end CE.

As shown in fig. 2, the position of the end CE of the contact surface substantially coincides with the position of the corner a of the core 30 in the axial direction. In other words, in a state where the tire 2 is assembled to the rim 54 and filled with air so as to have a normal internal pressure, the end CE of the contact surface is formed at a position corresponding to the corner a of the core 30 in the axial direction.

The protective layer 24 in this tire 2 is joined at a portion of its first end 64 (i.e., the first body 24a) to a portion of the end 48 of the innerliner 18. A portion of the second end 66 of the protective layer 24 (i.e., the second body 24b) is located in the radial direction and between the core 30 and the scuff guard 10. That is, the tire 2 is joined to a part of the end portion 48 of the inner liner 18, and includes the protective layer 24 located between the core 30 and the scuff rubber 10. Thus, the protective layer 24 has a first end 64 at the junction with the inner liner 18 and a second end 66 radially inward of the core 30.

In the tire 2, the second body 24b of the protective layer 24 extends from a portion of the toe 52 of the tire 2 along the bead seat 58 and toward the substantially axially outer side. The second end 66 of the protective layer 24 is located between the inboard end a of the bottom surface 62 of the core 30 and the outboard end f of the bottom surface 62. This tire 2 is configured such that, even if a gap as shown in fig. 2 is formed in a state of being assembled to the rim 54, the protective layer 24 overlaps with the gap. As described above, the rubber composition for the protective layer 24 includes butyl rubber as the base material rubber. The protective layer 24 inhibits moisture or oxygen from penetrating into the tire 2 from the gap. Thereby preventing the core 30 of the tire 2 from rusting.

The carcass 38 and the filler 22 are disposed between the protective layer 24 and the core 30 in the tire 2. As previously described, the plies 38 and fillers 22 each comprise steel cords. The protective layer 24 of the tire 2 prevents rusting of the cords contained in the ply layer 38 and the cords contained in the filler 22.

In the tire 2, the ratio of the butyl rubber to the total amount of the base rubber in the rubber composition for the protective layer 24 is 60 mass% or more. The protective layer 24 contributes to the leakage resistance. As described above, in this tire 2, a typical base material rubber of the inner liner 18 is butyl rubber or halogenated butyl rubber. Therefore, the protective layer 24 made of the rubber composition is reliably joined to the inner liner 18. From the viewpoint of leak resistance and reliable adhesiveness, the ratio is preferably 70% by mass or more.

For example, protective layer 24 is bonded to rub-resistant compound 10 and barrier layer 20 in addition to liner layer 18. Diene fine rubbers such as natural rubber are mainly used for the base material rubber of the scuff rubber 10 and the separator 20. Therefore, when the base material rubber contains an excessive amount of butyl rubber, the adhesion property of the protective layer 24 to these components is impaired.

In the tire 2, the ratio of the butyl rubber to the total amount of the base rubber in the rubber composition for the protective layer 24 is 90 mass% or less. The protective layer 24 is securely bonded not only to the inner liner 18 but also to the rub protection compound 10 and the release layer 20. From this viewpoint, the ratio is preferably 85% by mass or less.

As described above, in this tire 2, the amount of butyl rubber contained in the rubber composition for the protective layer 24 is appropriately adjusted. So that the protective layer 24 has a gas tightness comparable to that of the inner liner 18. Thereby achieving an improved leakage resistance in the tire 2. The protective layer 24 is also securely bonded to not only the inner liner 18 but also the rub shield 10. In other words, the protective layer 24 helps prevent peeling of the inner liner 18 and the rub protector 10. Thereby preventing damage in the tire 2 mainly due to peeling of the inner liner 18 and the scuff rubber 10. The tire 2 has excellent durability.

The tire 2 is intended to prevent the core 30 of the bead 12 from rusting and to improve durability without impairing leakage resistance. According to the present invention, it is possible to obtain the tire 2 which can prevent the core 30 of the bead 12 from rusting and improve the durability.

As described above, the protective layer 24 in this tire 2 not only has the air-tightness comparable to that of the inner liner 18, but also is sufficient to consider that the protective layer 24 has the adhesion property with the inner liner 18 and the chafing dish 10. In this tire 2, it is not necessary to arrange the inner liner 18 so as to overlap the aforementioned gap in order to prevent rusting of the core 30, as in the conventional tire. Also in this configuration, in order to prevent peeling of the inner liner 18 or the rubbing-resistant rubber 10, it is not necessary to provide another member considering the adhesion property with the both. The protective layer 24 also contributes to weight reduction of the tire 2.

As shown in fig. 2, the second end 66 of the protective layer 24 in this tire 2 is axially outward of the corner a of the core 30. The protective layer 24 sufficiently covers a gap formed between the tire 2 and the rim 54. The tire 2 can effectively suppress penetration of moisture or oxygen into the tire 2 from the gap. Thereby further preventing rusting of the core 30 and the like of the tire 2. From this viewpoint, it is preferable that the second end 66 of the protective layer 24 in the tire 2 is located axially outward of the corner portion a of the core 30, that is, the axially inward end of the bottom surface 62 of the core 30.

Although the amount of butyl rubber is appropriately adjusted, since the protective layer 24 contains butyl rubber, the protective layer 24 has inferior adhesion properties as compared with a rubber member containing no butyl rubber. Therefore, when the second end 66 of the cover sheet 24 is located axially outward of the corner f of the core 30, strain is concentrated on the second end 66, and the cover sheet 24 may be detached from the scuff tape 10 or the lap portion 8 depending on the case.

As shown in fig. 2, the second end 66 of the protective layer 24 in this tire 2 is axially inward of the corner f of the core 30. Therefore, it is difficult to concentrate strain on the second end 66 of the protective layer 24. The tire 2 effectively prevents the protective layer 24 from coming off the scuff rubber 10 or the clinch portion 8. Thereby allowing the tire 2 to have excellent durability. From this viewpoint, the second end 66 of the protective layer 24 of the tire 2 is preferably configured to be axially inward of the corner f of the core 30, that is, the axially outward end of the bottom surface 62 of the core 30. From the viewpoint of sufficiently suppressing rust without impairing the durability, it is preferable that the protective layer 24 is configured such that the second end 66 thereof is located between the center and the outer end of the bottom surface 62 of the core 30 in the axial direction.

The first end 64 of the protective layer 24 in the tire 2 is located radially outward of the corner b of the core 30, i.e., the axially inner end of the core 30. Not only the second body 24b but also the first body 24a of the protective layer 24 in this tire 2 effectively contributes to the leakage resistance performance. The tire 2 not only ensures leakage resistance, but also reliably ensures the adhesion area between the protective layer 24 and the inner liner 18. The tire 2 can prevent the core 30 from rusting and can further improve durability without impairing leakage resistance. From this viewpoint, the first end 64 of the protective layer 24 of the tire 2 is preferably located radially outward of the axially inner end of the core 30. Specifically, the first end 64 of the protective layer 24 is preferably disposed so that the radial distance from the axially inner end of the core 30 to the first end 64 is 3mm to 15 mm.

As shown in fig. 1 (or fig. 2), a part of the end portion 48 of the inner liner 18 in the tire 2 is tapered inward in the radial direction.

As previously mentioned, the protective layer 24 in this tire 2 contributes to the leakage resistance. Therefore, even if the joint portion of the inner liner 18 and the protective layer 24 is formed in a tapered shape like the tire 2, the tire 2 can prevent the core 30 from rusting and maintain excellent leakage resistance. Further, by configuring a part of the end portion 48 of the inner liner 18 to be pointed inward in the radial direction, air is effectively prevented from being taken into the end portion 48 in the process of manufacturing the tire 2. Further, the inner liner 18 having a sharp-pointed shape in which a part of the end portion 48 is formed inward in the radial direction suppresses influence on the quality of the tire 2. The protective layer 24 contributes to manufacturing of a high-quality tire 2 and weight reduction of the tire 2.

A part of the first end 64 of the protective layer 24 in the tire 2 is tapered outward in the radial direction. As described above, a part of the end portion 48 of the inner liner 18 is tapered inward in the radial direction. In the joint portion between the protective layer 24 and the inner liner 18 in the tire 2, the protective layer 24 and the inner liner 18 are respectively formed in a pointed shape. The tire 2 can suppress the influence of the joint portion on the quality of the tire 2 to be small.

Preferably, in the tire 2, a portion of the first end 64 of the protective layer 24 is tapered radially outward from the end 48 of the inner liner 18, and a portion of the end 48 of the inner liner 18 is tapered radially inward from the first end 64 of the protective layer 24. For this reason, a portion having a particularly thick thickness is prevented from being formed in the portion constituted by the inner liner layer 18 and the protective layer 24. The tire 2 is configured such that the portion configured by the inner liner 18 and the protective layer 24 has a substantially uniform thickness as a whole. The portion constituted by the lining layer 18 and the protective layer 24 as a whole contributes to good leakage resistance.

The double arrow T2 in fig. 2 is the thickness of the protective layer 24. The thickness T2 is represented by the thickness of the protective layer 24 measured in the axial direction and at a position corresponding to the axially inner end of the bottom surface 62 of the core 30, i.e., the corner a.

Preferably, the thickness T2 of the protective layer 24 in the tire 2 is 0.4mm to 1.5 mm. By setting this thickness to 0.4mm or more, penetration of moisture or oxygen into the protective layer 24 from the gap is reliably suppressed. The protective layer 24 in the tire 2 effectively prevents the core 30 from rusting. By setting the thickness T2 to 1.5mm or less, the height difference in the second end 66 of the protective layer 24 is prevented from being brought into the air. The protective layer 24 contributes to manufacturing a high-quality tire 2.

The double-headed arrow TJ in fig. 2 is the thickness of the joint portion between the protective layer 24 and the inner liner layer 18. The double-headed arrow T1 is the thickness of the protective layer 24 (first body 24a) in the joining portion. The thicknesses TJ and T1 are measured in the axial direction at positions corresponding to the radially inner ends of the cores 30, i.e., the corners b.

Preferably, the ratio of the thickness T1 of the protective layer 24 to the thickness TJ of the joint portion in the tire 2 is 50% to 90%. By setting this ratio to 50% or more, not only the influence of the inner liner 18 on the quality can be suppressed, but also the end portion 48 of the inner liner 18 can be effectively prevented from taking in air. From this viewpoint, the ratio is more preferably 60% or more. By setting this ratio to 90% or less, the internal pressure holding effect can be obtained at the joint portion substantially the same as that of the portion constituted by the inner liner 18 alone. So that the tire 2 maintains good leakage resistance. From this viewpoint, the ratio is more preferably 80% or less.

[ examples ] A method for producing a compound

Hereinafter, although the effects of the present invention will be described by way of examples, the present invention should not be construed as being limited thereto.

[ example 1]

Tires as shown in fig. 1-2 were produced. The tire size was 275/80R 22.5. In this embodiment 1, a protective layer is provided. These are all indicated by "Y" in the column of the protective layer in Table 1. The first end of the protective layer is disposed radially outward of the axially inner end of the core (the corner b of the core). These are all indicated by "out" in the column for the location of the first end in table 1. The second end of the protective layer is arranged in the axial direction between the inner end (corner a of the core) and the outer end (corner f of the core) of the bottom surface of the core. These are all indicated by "a-f" in the column for the position of the second end in table 1. The ratio of the butyl rubber to the entire mass of the base rubber (IIR ratio in table 1) in the rubber composition for the protective layer was set to 70 mass%. The thickness T2 of the protective layer was 1.0 mm.

Comparative example 1

A tire of comparative example 1 was obtained in the same manner as in example 1 except that no protective layer was provided. This comparative example 1 is a conventional tire. The case where no protective layer is provided is represented by "N" in the protective layer column of table 1.

Comparative example 2

A tire of comparative example 2 was obtained in the same manner as in example 1, except that the second end of the protective layer was disposed axially inward of the inner end of the bottom surface of the core (the corner a of the core). The case where the position of the second end is located axially inward of the inner end of the bottom surface of the core is indicated by "in the column of the second end position in table 1.

Comparative example 3

A tire of comparative example 3 was obtained in the same manner as in example 1, except that the second end of the protective layer was disposed axially outward of the outer end of the bottom surface of the core (the corner f of the core). The case where the second end position is located axially outward of the outer end of the bottom surface of the core is indicated by "out" in the column of the second end position in table 1.

[ examples 2 to 4]

Tires of examples 2 to 4 were obtained in the same manner as in example 1, except that the thickness T2 of the protective layer was set to the same value as in table 2 below.

[ examples 5 to 7]

Tires of examples 5 to 7 were obtained in the same manner as in example 1, except that the ratio of the butyl rubber was set as in table 3 below.

[ leak resistance Property ]

The tire is assembled to a rim, and air is filled so that the inner pressure of the tire becomes a normal inner pressure. Air was filled and left for 9 weeks. The internal pressure reduction rate due to leaving standing was determined from the internal pressure after filling and the internal pressure after leaving standing, and the leak resistance was evaluated from the reduction rate. The results are shown exponentially in tables 1 to 3 below. The larger the value, the smaller the reduction rate, the superior leakage resistance is obtained.

[ durability Properties ]

A tire was assembled on a regular rim, and after water (about 100cc) was added to the tire, the tire was filled with air to make the internal pressure 830 kPa. The tire was charged into an oven set at 70 ℃. And left to stand for 1 week in this state to deteriorate the tire. The deteriorated tire was mounted on a drum-type running tester, and a standard load (longitudinal load of 36.77 kN) was applied to the tire. The tire was run on a drum having a radius of 1.7m at a speed of 80 km/h. The distance traveled until the tire broke was measured. The results are shown as indices in tables 1 to 3 below. The larger the value, the longer the measuring distance, the excellent durability is obtained.

[ removal of rubbing gum ]

A test tire was mounted on a regular rim, and air was filled into the tire so that the internal pressure was 830 kPa. The tire was mounted to front and rear wheels of a truck (10 tons) and run on a loop type track at a speed of 80km/h in a maximum load state. The running is continued until the tread is worn. After running, the tire was recovered to confirm whether the anti-rub rubber was peeled off. The number of the anti-scuff rubber drops was determined from 100 test tires on average, and the rate of occurrence of the drops was obtained. The results are shown as indices in tables 1 to 3 below. The larger the value, the lower the incidence of rub-off of the rub resist.

[ formation of Rust ]

A tire was assembled on a regular rim, and after water (about 100cc) was added to the tire, the tire was filled with air to make the internal pressure 830 kPa. The tire was charged into an oven set at 70 ℃. And left to stand for 1 week in this state to deteriorate the tire. Whether or not the core of the tire bead after deterioration rusts was confirmed. The results are shown in tables 1 to 3 below as "Y" indicating rusting and "N" indicating no rusting.

[ TABLE 1]

TABLE 1 evaluation results

[ TABLE 2]

TABLE 2 evaluation results

[ TABLE 3]

Table 3 evaluation results

As shown in tables 1 to 3, the evaluation of the tires of examples was higher than that of the tires of comparative examples. The results show the superiority of the present invention.

The technique described above relating to the protective layer can also be applied to various tires.

Claims

1. A pneumatic tire, comprising:

an inner liner for maintaining an internal pressure;

an anti-rub rubber which is loaded on a bead seat of a rim;

a lap joint portion that contacts a flange of the rim;

a core located outside the rubbing gum in a radial direction;

a protective layer joined to an end of the inner liner layer and positioned between the core and the rub-resistant compound,

the protective layer has:

a first end located at a junction with the inner liner layer; and

a second end located radially inward of the core,

said core comprising a bottom surface opposite said bead seats when the tire is assembled on said rim,

said bottom surface extending in a substantially axial direction in a section of the tire along a plane containing a central axis of the tire,

in an axial direction, the second end is located between a center of the bottom surface and an outer end of the bottom surface,

the protective layer is composed of a crosslinked rubber formed from a rubber composition,

the rubber composition comprises a base material rubber,

the matrix material rubber comprises butyl rubber,

the ratio of the butyl rubber to the total amount of the base rubber is 65 mass% to 90 mass%.

2. A pneumatic tire according to claim 1,

the thickness of the protective layer is more than 0.4mm and less than 1.5 mm.

3. A pneumatic tire according to claim 1 or 2,

the first end is located radially outward of an axially inner end of the core.

4. A pneumatic tire according to claim 3,

a radial distance from an axial inner end of the core to the first end is 3mm to 15 mm.

5. A pneumatic tire according to claim 1,

the ratio of the thickness of the protective layer to the thickness of the joint portion is 50% to 90%.