CN115768633A

CN115768633A - Pneumatic tire

Info

Publication number: CN115768633A
Application number: CN202280004745.8A
Authority: CN
Inventors: 森田康挥
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 2021-03-09
Filing date: 2022-02-21
Publication date: 2023-03-07
Also published as: JP2022137926A; WO2022190841A1

Abstract

A pneumatic tire in which at least the inner cavity surface of the tire is made of a thermoplastic resin, wherein deformation of the tire due to heat generation during running is suppressed. A pneumatic tire has a tread portion 2. At least the tire inner cavity surface 5 is made of a thermoplastic resin. The tread portion 2 includes a tread reinforcing layer 10 on the inner side in the tire radial direction than the center position of the thickness of the tread portion 2. A plurality of grooves 11 are provided on the outermost surface of the tread portion 2. The negative ratio, which is the ratio of the total opening area of the plurality of grooves 11 to the virtual ground contact area for filling the entire plurality of grooves 11, is 20% to 50%.

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire.

Background

In general, a pneumatic tire is mainly composed of a rubber material, but the rubber material has a problem of difficulty in recycling. In recent years, various pneumatic tires including a member made of a material having excellent recyclability have been proposed. For example, patent document 1 listed below proposes a tire using a thermoplastic resin for a tire frame.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 6138695

Disclosure of Invention

Problems to be solved by the invention

The tire of patent document 1 has a tire cavity surface made of a thermoplastic resin. In such a tire, the inner cavity surface of the tire may be plasticized and deformed by heat generated during running. Specifically, if the inner cavity surface of the tire is plasticized, there is a possibility that the outer diameter of the tire grows due to the inner pressure of the tire, local plastic deformation of the tread portion occurs, and the rolling resistance deteriorates.

The present invention has been made in view of the above circumstances, and a main object thereof is to provide a pneumatic tire in which at least a tire cavity surface is made of a thermoplastic resin, which can suppress deformation of the tire caused by heat generation during running and suppress deterioration of rolling resistance during continuous running.

Means for solving the problems

The present invention provides a pneumatic tire having a tread portion, wherein at least a tire inner cavity surface is made of a thermoplastic resin, the tread portion includes a tread reinforcing layer at a position further toward a tire radial direction inner side than a center position of a thickness of the tread portion, a plurality of grooves are provided on an outermost surface of the tread portion, and a negative ratio (negative ratio) which is a ratio of a total opening area of the plurality of grooves to a virtual ground contact area in which the plurality of grooves are entirely filled is 20% to 50%.

ADVANTAGEOUS EFFECTS OF INVENTION

With the above configuration, the pneumatic tire according to the present invention can suppress deformation of the tire caused by heat generation during running.

Drawings

Fig. 1 is a meridian cross-sectional view of a pneumatic tire of one embodiment of the present invention.

Fig. 2 is an enlarged sectional view of the tread portion of fig. 1.

Fig. 3 is an enlarged sectional view of a tread portion of another embodiment of the present invention.

Fig. 4 is an enlarged sectional view of a tread portion of another embodiment of the present invention.

Fig. 5 is a meridian cross sectional view of a pneumatic tire of another embodiment of the present invention.

[ reference numerals ]

2. Tread portion

5. Inner chamber surface of tire

10. Tread reinforcement layer

11. Ditch (I)

Detailed Description

Hereinafter, one embodiment of the present invention will be described based on the drawings. Fig. 1 is a meridian cross-sectional view of a pneumatic tire 1 (hereinafter, may be simply referred to as a tire 1) of the present embodiment. Fig. 1 is a cross-sectional view of the tire 1 including the tire rotation axis in a normal state. As shown in fig. 1, the tire 1 of the present embodiment is used as, for example, a pneumatic tire for a passenger vehicle. However, the present invention is not limited to the above embodiment, and may be applied to a pneumatic tire for a motorcycle or a pneumatic tire for a cart.

The "normal state" is a state in which, in the case of tires specified by various specifications, the tires are assembled to a normal rim by the rim, and are filled with a normal internal pressure and no load. In the present specification, unless otherwise specified, the dimensions and the like of each portion of the tire are values measured in the above normal state.

The "regular Rim" is a Rim defined for each tire in a specification system including a specification based on which the tire is based, and for example, the "regular Rim" means a "standard Rim" in the case of JATMA, a "Design Rim (Design Rim)" in the case of TRA, and a "Measuring Rim" in the case of ETRTO. In the case of a tire not specified in the specification, the "regular rim" means a rim that can be rim-assembled and can maintain internal pressure, that is, a rim having the smallest rim diameter and the narrowest rim width next to the rim diameter, among rims in which air leakage does not occur between the rim and the tire.

The "normal internal PRESSURE" refers to an air PRESSURE specified for each TIRE in a specification system including a specification based on which the TIRE is based, and is "maximum air PRESSURE" in case of JATMA, a maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES (TIRE LOADs AT VARIOUS COLD INFLATION PRESSURES) (TIRE PRESSURES) in case of TRA, and an" INFLATION PRESSURE "in case of ETRTO. In the case of tires having no specification, the normal internal pressure is 250kPa in the case of passenger tires, and 350kPa in the case of tires having a normal load larger than that of passenger vehicles.

Here, the tire for a passenger vehicle is a tire mounted on a vehicle which runs 4 wheels, and the normal load is 1000kg or less.

The "normal LOAD" is a maximum LOAD CAPACITY defined for each TIRE in a specification system including a specification based on the TIRE, and is, for example, a maximum LOAD CAPACITY based on a LOAD Index (LI) in the case of JATMA specification (japan automobile TIRE association specification), a maximum value described in "TIRE LOAD LIMITS under VARIOUS COLD INFLATION PRESSURES (TIRE LOAD AT COLD INFLATION PRESSURES) (TIRE LOAD capabilities)" in the case of TRA, and a "LOAD CAPACITY (LOAD availability)" in the case of ETRTO. When the tire is not specified in the specification, the tire is based on a virtual volume V (mm) outside the rim of the tire obtained from the tire section width Lt (mm), the tire outer diameter Dt (mm), the tire section height Ht (mm), and the circumferential ratio ³ ) The value obtained by the following calculation formula is treated as the normal load (kg).

Normal load (kg) =0.000011 × V +175

V＝{(Dt ² -Ht ² )/4}×π×Lt

The tire section width Lt (mm), the tire section height Ht (mm), and the tire outer diameter Dt (mm) may be measured directly from a real tire, or may be measured from a photographic image such as CT.

The tire outer diameter Dt is an outer diameter of the tire in a normal state, and the tire cross-sectional width Lt is a width obtained by removing a pattern, a letter, and the like on the side surface of the tire from a linear distance (total width of the tire) between all the sidewall walls including the pattern, the letter, and the like on the side surface of the tire in the normal state. The tire section height Ht is the height of the tire in the tire section, and can be calculated by subtracting the rim diameter (mm) from the tire outer diameter Dt, and dividing by 2.

The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portion 3 extends inward in the tire radial direction from an end of the tread portion 2 in the tire axial direction. The bead portion 4 is connected to the tire radial direction inner side of the sidewall portion 3. In addition, in the tread portion 2 of the tire 1, at least the tire cavity surface 5 is composed of a thermoplastic resin.

In the present specification, the "thermoplastic resin" refers to a polymer compound which has fluidity due to temperature rise and reversibly becomes a relatively hard and strong state after being cooled again, and can be molded without going through a vulcanization step as in a general rubber member for a tire. Therefore, the thermoplastic resin referred to in the present specification does not include a general rubber member for a tire (vulcanized rubber), but is a recyclable resin material. Whether or not a tire is a tire using a thermoplastic resin can be determined from the temperature dependence of the modulus of elasticity of a tire member and the like.

In addition, in the present specification, the thermoplastic resin includes a non-elastic thermoplastic resin having no rubber-like elasticity in a cooled state and a thermoplastic elastomer having rubber-like elasticity in a cooled state. The thermoplastic elastomer is softened and fluidized as the temperature rises, and after cooling, it is relatively hard and strong, and has rubber-like elasticity. The cooling state is a temperature state in a normal use or storage of the tire. In the present specification, unless otherwise specified, any of the inelastic thermoplastic resin and the thermoplastic elastomer may be used as the thermoplastic resin, or they may be used in combination. However, in a more preferred embodiment, a thermoplastic elastomer is used as the thermoplastic resin.

Examples of the thermoplastic elastomer include polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polystyrene-based thermoplastic elastomers, and polyolefin-based thermoplastic elastomers, and they may be used alone or in combination.

Fig. 2 is an enlarged cross-sectional view of the tread portion 2. As shown in fig. 2, the tread portion 2 includes a tread reinforcing layer 10 on the inner side in the tire radial direction than the center position of the thickness of the tread portion 2. This structure means that, at least on the tire equatorial plane C, the tread reinforcing layer 10 is disposed further toward the tire radial direction inner side than the above-described center position. In a preferred embodiment, 50% or more, more preferably 80% or more of the volume of the tread reinforcing layer 10 is disposed further inward in the tire radial direction than the center position. As a more preferable aspect, in the present embodiment, the entire tread reinforcing layer 10 is disposed further inward in the tire radial direction than the center position.

The tread reinforcing layer 10 is a member having higher rigidity than the thermoplastic resin constituting the tire inner cavity surface 5, and can suppress the growth of the tire outer diameter. Further, a plurality of grooves 11 are provided on the outermost surface of the tread portion 2. The plurality of grooves 11 include both a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of widthwise grooves extending in the tire axial direction. The outermost surface is a surface of the tread portion 2 that can be in contact with a road surface during running of the tire.

The thickness of the tread portion 2 is a distance from the outermost surface of the tread portion 2 to the tire cavity surface in the tire normal direction in a radial cross section of the tire. When the groove 11 is present on the outermost surface of the tread portion 2, the thickness of the tread portion 2 is measured in a virtual state where the groove 11 is filled.

In the present invention, the negative ratio, which is the ratio of the total opening area of the plurality of grooves 11 to the virtual ground contact area of the tread portion 2 in which all of the plurality of grooves 11 are filled, is 20% to 50%. The virtual ground contact area is the total of the ground contact areas over the entire circumference of the tire that is grounded when the tire having the tread portion 2 in which the plurality of grooves 11 are all filled is put into the normal state and the tread portion 2 is pressed against a plane at an inclination angle of 0 °. Similarly, the area of the groove can be calculated by obtaining the area of the groove on the contact surface of the entire circumference of the tire. These can be measured simply by applying ink or the like to the tire surface and transferring it.

In the present invention, with the above configuration, deformation of the tire 1 caused by heat generation during running can be suppressed, and deterioration of rolling resistance during continuous running can be suppressed. The reason for this is presumed to be the following mechanism.

The tire inner cavity surface 5 is acted on by air filled in the tire from time to time by pressure. Therefore, in a tire in which the tire cavity surface 5 is made of a thermoplastic resin, the tire cavity surface is plasticized and deformed by heat generated during running, and further, growth of the tire outer diameter and local and plastic deformation of the tread portion occur. This is particularly concerned with deterioration of rolling resistance. In view of such a problem, in the present invention, by disposing the tread reinforcing layer 10 further toward the tire radial direction inner side, it is possible to prevent the growth of the tire outer diameter and to absorb the deformation in the entire tread portion 2.

In the present invention, when the negative ratio of the tread portion 2 is 20% or more, the heat of the tread portion 2 is easily released from the wall surface of the groove 11. When the negative ratio is 50% or less, local deformation of the outermost surface of the tread portion 2 can be suppressed, and heat generation can be prevented. In the present invention, it is considered that, by such a mechanism, in the pneumatic tire in which at least the tire inner cavity surface 5 is made of a thermoplastic resin, deformation of the tire caused by heat generation during running can be suppressed, and further, deterioration of rolling resistance can be suppressed.

Hereinafter, a more detailed configuration of the present embodiment will be described. Each configuration described below represents a specific embodiment of the present embodiment. Therefore, the present invention can certainly exhibit the above-described effects without having a configuration described below. In addition, even in the tire of the present invention having the above-described features, improvement in performance corresponding to each configuration can be expected by applying any one of the configurations described below alone. Further, when any one of the respective configurations described below is applied in a composite manner, it is possible to expect improvement in composite performance corresponding to each configuration.

As shown in fig. 1, the tread portion 2 is composed of a tread ground contact element 8 and a cavity surface member 14. The tread contact element 8 of the present embodiment is, for example, a single-layer structure formed of a single composition. In another embodiment, the tread ground-engaging element 8 may be formed of a multilayer structure using different compositions, such as a base tread portion or a base tread portion.

In the present embodiment, a two-layer structure is formed in which the tread ground contact element 8 and the inner cavity surface member 14 are composed of different compositions. The tread ground-engaging element 8 is composed of, for example, a thermoplastic elastomer different from the inner cavity surface member 14. Alternatively, the tread contact element 8 may be formed of a rubber composition. In addition, the present invention is not limited to the above-described mode, and the tread portion 2 may have a single-layer structure in which the tread contact element 8 and the inner cavity surface member 14 are formed of the same composition. In this case, the tread portion 2 is preferably entirely made of a thermoplastic resin.

In the case where the tread ground-engaging element 8 and the inner cavity surface member 14 are composed of different compositions as in the present embodiment, the air permeability coefficient of the inner cavity surface member 14 is preferably lower than that of the tread ground-engaging element 8 from the viewpoint of keeping air inside the tire. The air permeability coefficient is a value inherent to a material showing an air permeability, and passes through a plastic-film and sheet-gas permeability test method at a temperature of 30 ℃ in accordance with JIS K7126-7-part 1: and (4) measuring by a differential pressure method.

Further, the tread portion 2 has a pair of sidewall portions 13 on the outer side in the tire axial direction. In the embodiment shown in fig. 1, the sidewall portion 13 is a single-layer structure formed of a single composition, and constitutes the sidewall portion 3 and the bead portion 4. In addition, the bead portion 4 includes a bead wire (bead wire) for improving the fitting property. In another embodiment, the sidewall portion 13 may be divided into a plurality of parts to achieve performance required according to the application, such as steering stability and riding comfort, and may function as a bead apex, a rubber chafer, or the like, as in a typical pneumatic tire.

As shown in fig. 2, the tread reinforcing layer 10 includes, for example, a plurality of cords 16 and a coating portion 17 that coats the cords 16.

The cord 16 is, for example, an organic fiber cord or a steel cord. The cord 16 of the present embodiment is wound spirally at an angle of 5 ° or less with respect to the tire circumferential direction, for example. Such a cord 16 can reliably suppress the growth of the tire outer diameter. However, the present invention is not limited to this, and the cord 16 may be inclined at 30 to 60 ° with respect to the tire circumferential direction, for example, like a belt cord of a general tire. In addition, the tread reinforcing layer 10 may include a layer formed of a plurality of cords 16 inclined in a first direction with respect to the tire circumferential direction and a layer formed of a plurality of cords 16 inclined in a second direction opposite to the above-described first direction.

The covering 17 is made of, for example, adhesive rubber (rubberizing rubber). This can effectively suppress the peeling of the tread reinforcing layer 10. However, the present invention is not limited to this embodiment, and the covering 17 may be made of a thermoplastic resin. In this case, the covering 17 is more preferably made of a thermoplastic elastomer. This further improves the recycling performance of the tire.

Fig. 3 shows an enlarged sectional view of the tread portion 2 of another embodiment. As shown in fig. 3, the tread reinforcing layer 10 of the present embodiment contains a thermoplastic resin, and more preferably is entirely composed of a thermoplastic resin. That is, the tread reinforcing layer 10 does not include a cord. Thereby, the recycling performance is further improved. The thermoplastic resin of the tread reinforcing layer 10 is naturally higher in rigidity than the thermoplastic resin constituting the tire inner cavity surface 5. In addition, as the thermoplastic resin of the tread reinforcing layer 10, a thermoplastic elastomer is more preferably applied.

Fig. 4 also shows an enlarged sectional view of the tread portion 2 of another embodiment. As shown in fig. 4, the tread reinforcing layer 10 of this embodiment is covered with a thermoplastic resin constituting the tire inner cavity surface 5. More specifically, the plurality of cords 16 constituting the tread reinforcing layer 10 are embedded inside the thermoplastic resin constituting the tire inner cavity surface 5. In such an embodiment, the thermoplastic resin constituting the tire inner cavity surface 5 is used as the covering portion of the tread reinforcing layer 10, and therefore, the manufacturing cost of the tire can be reduced.

As shown in fig. 2, the length L1 of the tread reinforcing layer 10 in the tire axial direction is 25% to 81% of the maximum width W1 of the tire. In the embodiment shown in fig. 3 and 4, the length of the tread reinforcing layer 10 is also defined in the same manner. Such a tread reinforcing layer 10 can suppress an increase in the manufacturing cost and the weight of the tire, and can suppress the growth of the outer diameter of the tire.

The distance d2 from the outermost surface of the tread portion 2 to the tread reinforcing layer 10 is, for example, 65 to 95%, preferably 80 to 90%, of the thickness d1 of the tread portion 2. This can more reliably exhibit the above-described effects. The distance d2 corresponds to a distance in the tire normal direction from the outermost surface of the tread portion 2 to the outer surface of the tread reinforcing layer 10 on the outer side in the tire radial direction. The outer surface of the tread reinforcing layer 10 refers to the outer surface of the covering portion 17 of the tread reinforcing layer 10 in the embodiment shown in fig. 2, and refers to the outer surface of the cord 16 in the embodiment shown in fig. 4.

The tread reinforcing layer 10 has a tensile elastic modulus Ad greater than that of the thermoplastic resin constituting the tire inner cavity surface 5. Specifically, the tensile elastic modulus Ad of the tread reinforcing layer 10 is preferably 100MPa or more. This can reliably suppress deformation of the tread portion 2 and suppress deterioration of rolling resistance. The tensile modulus of the tread reinforcing layer 10 is calculated from the slope of the stress at the time when a test sample having a width of 10mm and extending 40mm or more in the tire circumferential direction is collected from the tread reinforcing layer 10 and is subjected to tensile deformation in a tensile testing machine to a region where the width of the test sample is 10mm and the length thereof is 40 mm. At this time, the deformation speed of the sample was 200mm/min, and the measurement temperature was room temperature. From the stress values at 0.05% and 0.25% deformation of the obtained stress-strain curve, the slope was calculated and found as the tensile modulus. In addition, when the tread reinforcing layer is a composite of a cord and a thermoplastic resin, etc., the calculation is performed in a composite state of these.

The smaller the distance d2 from the outermost surface of the tread portion 2 to the tread reinforcing layer 10, the greater the tensile elastic modulus Ad of the tread reinforcing layer 10 required for reinforcing the tread portion 2. From such a viewpoint, in order to sufficiently reinforce the tread portion 2, the value Ad × d2/d1 (MPa) obtained by multiplying the tensile elastic modulus Ad (MPa) by the ratio d2/d1 of the distance d2 from the outermost surface of the tread portion 2 to the tread reinforcing layer 10 to the thickness d1 of the tread portion 2 is preferably 100MPa or more, and more preferably 200MPa or more.

The negative ratio of the tread portion 2 is preferably 25% to 40%, and preferably 25% to 35%. Such a tread portion 2 can exhibit excellent heat dissipation properties while suppressing local deformation.

The plurality of grooves 11 of the present embodiment includes a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of widthwise grooves (not shown) extending in the tire axial direction. The ratio of the total opening area of the plurality of circumferential grooves to the virtual ground contact area, that is, the negative circumferential groove ratio is preferably 10% to 40%. Further, it is preferable that a ratio of a total opening area of the plurality of widthwise grooves to the virtual ground contact area, that is, a widthwise groove negative ratio is 10% to 40%. This can ensure rigidity of the tread portion 2 in the tire circumferential direction and rigidity in the tire axial direction in a well-balanced manner.

The total volume of the plurality of grooves 11 is preferably 2.0% to 10.0% of the volume of the tread portion 2. This improves the wet performance and the handling stability in a well-balanced manner. The volume of the tread portion 2 is the total volume of the tread portion 2 divided by the tire normal line passing through the end portion of the tread portion 2 in the tire axial direction on the outermost surface.

The tread contact element 8 is a portion for contacting the ground, and is formed of a general vulcanized rubber for a tire in the present embodiment. In addition, in the tread ground contact element 8 of the present embodiment, a known composition of tread rubber can be applied. However, in order to improve recyclability, the tread contact element 8 may contain a part of the thermoplastic resin, and the entire tread contact element 8 may be formed of the thermoplastic resin. In this case, the tread ground-engaging elements 8 are more preferably entirely composed of a thermoplastic elastomer.

Fig. 5 shows a meridian cross section of a tire 1 of another embodiment of the present invention. As shown in fig. 5, the tire 1 of the present embodiment includes, for example: a ring-shaped tire frame member 7 including a pair of bead portions 4, and a tread ground contact element 8 constituting the outermost surface of the tread portion 2. The tire frame member 7 constitutes the bead portion 4 and the sidewall portion 3. At least comprises the following components. Further, the tire frame member 7 includes an under tread portion 2d arranged on the inner side of the tread ground contact element 8 in the tire radial direction. The bottom tread portion 2d is a member supporting the tread ground contact element 8, and is connected to the sidewall portions 3 on both sides. As described above, the present invention is not limited to the embodiment shown in fig. 1 to 4, and includes the embodiment shown in fig. 5 as long as the tire cavity surface 5 of the tread portion 2 is made of a thermoplastic resin.

The pneumatic tire according to the embodiment of the present invention has been described above in detail, but the present invention is not limited to the above specific embodiment and may be modified to various embodiments.

Examples

Pneumatic tires for passenger vehicles having the structure shown in fig. 1 were produced by trial production in accordance with the specifications of tables 1 to 5. As a tire of the comparative example, a tire having the structure of fig. 1 and a negative ratio of 55% was tried out. The tire of the comparative example is substantially the same as the tire of the example except for the above-mentioned points. For each test tire, rolling resistance was tested to evaluate the degree of deformation of the tread portion. The general specifications and test methods are as follows.

Tire size: 195/65R15

Rim: 15X 6.0J

Tire internal pressure: 250kPa

< rolling resistance >

The rolling resistance of the test tire during running on a roller tester was measured. The results are expressed as the reciprocal of the rolling resistance, and are expressed by an index with the comparative example being 100. The larger the value, the smaller the rolling resistance.

The test results are shown in tables 1 to 5.

[ Table 1]

As shown in tables 1 to 5, it was confirmed that the tires of the examples had low rolling resistance and deformation of the tires accompanied by heat generation during running was suppressed.

[ accompanying notes ]

The present invention includes the following modes.

[ invention 1]

A pneumatic tire having a tread portion, characterized in that,

at least the tire inner cavity surface is made of a thermoplastic resin,

the tread portion includes a tread reinforcing layer at a position further toward the inner side in the tire radial direction than a center position of a thickness of the tread portion,

a plurality of grooves are provided on the outermost surface of the tread portion,

the negative ratio, which is the ratio of the total opening area of the plurality of trenches to the virtual ground area in which all of the plurality of trenches are filled, is 20% to 50%.

[ invention 2]

The pneumatic tire according to the present invention 1, wherein the tread reinforcing layer has a length in the tire axial direction of 25% to 81% of the maximum width of the tire.

[ invention 3]

The pneumatic tire according to the invention 1 or 2, wherein the tread reinforcing layer contains a thermoplastic resin.

[ invention 4]

The pneumatic tire according to any one of claims 1 to 3, wherein the tread reinforcing layer has a tensile elastic modulus of 100MPa or more.

[ invention 5]

The pneumatic tire according to any one of claims 1 to 4, wherein the tread reinforcing layer is covered with the thermoplastic resin constituting the tire inner cavity surface.

[ invention 6]

The pneumatic tire according to any one of claims 1 to 5, wherein the tread reinforcing layer includes a plurality of cords formed of an organic fiber or a metal.

[ invention 7]

The pneumatic tire according to any one of claims 1 to 6, wherein a distance from an outermost surface of the tread portion to the tread reinforcing layer is 80% to 90% of a thickness of the tread portion.

[ invention 8]

The pneumatic tire according to any one of the inventions 1 to 7, wherein,

a plurality of circumferential grooves extending in a tire circumferential direction are provided on an outermost surface of the tread portion,

the ratio of the total opening area of the plurality of circumferential grooves to the virtual ground contact area, that is, the negative circumferential groove ratio, is 10% to 40%.

[ invention 9]

The pneumatic tire according to any one of claims 1 to 8, wherein,

a plurality of widthwise grooves extending in the tire axial direction are provided on the outermost surface of the tread portion,

the ratio of the total opening area of the plurality of widthwise grooves to the virtual ground contact area, that is, the widthwise groove negative ratio, is 10% to 40%.

[ invention 10]

The pneumatic tire according to any one of claims 1 to 9, wherein a total volume of the plurality of grooves is 2.0% to 10.0% of a volume of the tread portion.

[ invention 11]

The pneumatic tire according to any one of claims 1 to 10, wherein the tread portion contains a thermoplastic resin.

[ invention 12]

The pneumatic tire according to any one of claims 1 to 11, wherein the negative ratio is 25% to 35%.

[ invention 13]

The pneumatic tire according to any one of claims 1 to 12, wherein the thermoplastic resin contains a thermoplastic elastomer having rubber-like elasticity in a cooled state.

[ invention 14]

The pneumatic tire according to any one of claims 1 to 13, wherein,

the tread portion includes a tread ground-engaging element constituting the outermost surface and a cavity surface member constituting the tire cavity surface,

the inner cavity surface member has a lower air permeability coefficient than the tread ground engaging element.

[ invention 15]

The pneumatic tire according to any one of claims 1 to 14, wherein,

a value Ad × d2/d1 (MPa) obtained by multiplying a tensile elastic modulus Ad (MPa) of the tread reinforcing layer by a ratio d2/d1 of a distance d2 from the outermost surface to the tread reinforcing layer to a thickness d1 of the tread portion is 100MPa or more.

Claims

1. A pneumatic tire having a tread portion, characterized in that,

at least the tire inner cavity surface is composed of a thermoplastic resin,

2. The pneumatic tire according to claim 1, wherein the tread reinforcing layer has a length in the tire axial direction of 25% to 81% of the maximum width of the tire.

3. The pneumatic tire according to claim 1 or 2, wherein the tread reinforcing layer contains a thermoplastic resin.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the tread reinforcing layer has a tensile modulus of elasticity of 100MPa or more.

5. The pneumatic tire according to any one of claims 1 to 4, wherein the tread reinforcing layer is covered with the thermoplastic resin constituting the tire inner cavity surface.

6. The pneumatic tire according to any one of claims 1 to 5, wherein the tread reinforcing layer comprises a plurality of cords formed of an organic fiber or a metal.

7. The pneumatic tire according to any one of claims 1 to 6, wherein a distance from an outermost surface of the tread portion to the tread reinforcing layer is 80% to 90% of a thickness of the tread portion.

8. The pneumatic tire according to any one of claims 1 to 7,

9. The pneumatic tire according to any one of claims 1 to 8,

the ratio of the total opening area of the plurality of widthwise grooves to the virtual ground contact area, that is, the negative ratio of the widthwise grooves is 10% to 40%.

10. The pneumatic tire according to any one of claims 1 to 9, wherein a total volume of the plurality of grooves is 2.0% to 10.0% of a volume of the tread portion.

11. The pneumatic tire according to any one of claims 1 to 10, wherein the tread portion contains a thermoplastic resin.

12. The pneumatic tire according to any one of claims 1 to 11, wherein the negative ratio is 25% to 35%.

13. The pneumatic tire according to any one of claims 1 to 12, wherein the thermoplastic resin contains a thermoplastic elastomer having rubber-like elasticity in a cooled state.

14. The pneumatic tire according to any one of claims 1 to 13,

the tread portion includes a tread ground-engaging element constituting the outermost surface and an inner cavity surface member constituting the inner cavity surface of the tire,

the air permeability coefficient of the inner cavity surface member is lower than the air permeability coefficient of the tread ground-engaging element.

15. The pneumatic tire according to any one of claims 1 to 14, wherein a value Ad x d2/d1 obtained by multiplying a tensile elastic modulus Ad of the tread reinforcing layer by a ratio d2/d1 of a distance d2 from the outermost surface to the tread reinforcing layer to a thickness d1 of the tread portion is 100MPa or more, and a unit of the tensile elastic moduli Ad, ad x d2/d1 is MPa.