WO2022190841A1

WO2022190841A1 - Pneumatic tire

Info

Publication number: WO2022190841A1
Application number: PCT/JP2022/007020
Authority: WO
Inventors: 康揮森田
Original assignee: 住友ゴム工業株式会社
Priority date: 2021-03-09
Filing date: 2022-02-21
Publication date: 2022-09-15
Also published as: JP2022137926A; CN115768633A

Abstract

Provided is a pneumatic tire having at least a tire inner cavity surface composed of a thermoplastic resin, wherein deformation of the tire accompanying heat generation during traveling is suppressed.　The pneumatic tire has a tread part 2. At least the tire inner cavity surface 5 is composed of a thermoplastic resin. The tread part 2 includes a tread reinforcing layer 10 on the inner side in the tire radial direction from the center position of the thickness of the tread part 2. A plurality of grooves 11 are provided in the outermost surface of the tread part 2. A negative ratio, which is the ratio of the total opening area of the plurality of grooves (11) to the virtual ground contact area if the plurality of grooves (11) were all filled, is 20-50%.

Description

pneumatic tire

The present disclosure relates to pneumatic tires.

In general, pneumatic tires are mainly composed of rubber materials, but rubber materials have the problem of being difficult to recycle. BACKGROUND ART In recent years, various proposals have been made for pneumatic tires including members made of highly recyclable materials. For example, Patent Literature 1 below proposes a tire in which a thermoplastic resin is used for a tire frame.

Japanese Patent No. 6138695

In the tire of Patent Document 1, the inner cavity surface of the tire is made of a thermoplastic resin. Such a tire may be deformed due to plasticization of the tire inner surface due to heat generated during running. Specifically, when the inner cavity surface of the tire is plasticized, there is concern that the tire's internal pressure will cause the outer diameter of the tire to grow and the tread portion to be locally and plastically deformed, thereby deteriorating the rolling resistance.

The present disclosure has been devised in view of the actual situation as described above. The main issue is to suppress the deterioration of rolling resistance during running.

The present disclosure is a pneumatic tire having a tread portion, wherein at least a tire inner cavity surface is made of a thermoplastic resin, and the tread portion is radially inward of a center position of the thickness of the tread portion. includes a tread reinforcing layer, the outermost surface of the tread portion is provided with a plurality of grooves, and the negative rate is the ratio of the total opening area of the plurality of grooves to the virtual ground contact area in which all of the plurality of grooves are filled. is a pneumatic tire, between 20% and 50%.

By adopting the above configuration, the pneumatic tire of the present disclosure can suppress deformation of the tire due to heat generation during running.

1 is a meridional cross-sectional view of a pneumatic tire of one embodiment of the present disclosure; FIG. FIG. 2 is an enlarged sectional view of the tread portion of FIG. 1; 4 is an enlarged cross-sectional view of a tread portion of another embodiment of the present disclosure; FIG. 4 is an enlarged cross-sectional view of a tread portion of another embodiment of the present disclosure; FIG. FIG. 4 is a meridional cross-sectional view of a pneumatic tire according to another embodiment of the present disclosure;

2 Tread Part 5 Tire Inner Surface 10 Tread Reinforcing Layer 11 Groove

An embodiment of the present disclosure will be described below based on the drawings. FIG. 1 is a meridional cross-sectional view of a pneumatic tire 1 (hereinafter sometimes simply referred to as tire 1) of the present embodiment. FIG. 1 is a cross-sectional view of the tire 1 in a normal state, including the tire rotation axis. As shown in FIG. 1, the tire 1 of this embodiment is used, for example, as a pneumatic tire for passenger cars. However, the present disclosure is not limited to such an aspect, and may be applied to pneumatic tires for motorcycles and pneumatic tires for carts.

"Regular condition" means that, in the case of tires that meet various standards, the tire is mounted on a regular rim, filled with regular internal pressure, and has no load. In this specification, unless otherwise specified, the dimensions of each part of the tire are the values measured in the normal condition.

A "regular rim" is a rim defined for each tire in a standard system that includes the standard on which the tire is based. For example, JATMA is a "standard rim", For ETRTO, it is "Measuring Rim". In the case of non-standard tires, the "regular rim" is the rim that can be mounted on the rim and can maintain internal pressure, that is, the rim that does not cause air leakage between the rim and tire, and has the largest rim diameter. Small, then refers to the narrowest rim width.

"Regular internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standard that the tire is based on. Maximum value described in VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO. In the case of tires for which various standards are not defined, the normal internal pressure is 250 kPa for passenger car tires, and 350 kPa for tires with a larger normal load than passenger car tires.

Here, "passenger car tires" refer to tires that are mounted on automobiles that run on four wheels and have a normal load of 1000 kg or less.

In addition, the above-mentioned "regular load" is the maximum load capacity specified for each tire by the standard in the standard system including the standard on which the tire is based. , the maximum load capacity based on the load index (LI), the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. In the case of tires that are not specified in the standard, the tire section width Lt (mm), the tire outer diameter Dt (mm), the tire section height Ht (mm), and the virtual volume excluding the tire rim calculated from the circumference ratio Based on V (mm ³ ), the value obtained by the following formula is treated as the normal load (kg).
Normal load (kg) = 0.000011 x V + 175
V = {(Dt ² -Ht ² )/4} x π x Lt

The tire cross-sectional width Lt (mm), tire cross-sectional height Ht (mm), and tire outer diameter Dt (mm) can be measured directly from the actual tire or from a CT image.

The tire outer diameter Dt is the outer diameter of the tire in the normal state, and the tire cross-sectional width Lt is the linear distance between the sidewalls including all the patterns and characters on the tire side surface in the normal state (total width of the tire). This is the width excluding patterns and characters on the tire side. 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 two.

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 radially inward from the axial end of the tread portion 2 . The bead portion 4 continues to the inner side of the sidewall portion 3 in the tire radial direction. Moreover, in the tread portion 2 of the tire 1, at least the tire inner cavity surface 5 is made of a thermoplastic resin.

As used herein, the term “thermoplastic resin” refers to a polymer compound that becomes reversible to a relatively hard and strong state when the temperature rises and the material becomes fluid when cooled again, and is used for general tires. This refers to materials that can be molded without undergoing a vulcanization process, such as rubber materials. Therefore, the thermoplastic resin as used herein does not include general tire rubber components (vulcanized rubber), but is a recyclable resin material. Whether or not the tire is made of thermoplastic resin can be determined from the temperature dependence of the elastic modulus of the tire member.

In addition, in this specification, thermoplastic resins include inelastic thermoplastic resins that do not have rubber-like elasticity in a cooled state, and thermoplastic elastomers that have rubber-like elasticity in a cooled state. Thermoplastic elastomers soften and flow as the temperature rises, become relatively hard and strong when cooled, and have rubber-like elasticity. The term "cooled state" means a temperature state when the tire is used or stored in a normal manner. In this specification, unless otherwise specified, as the thermoplastic resin, both non-elastic thermoplastic resins and thermoplastic elastomers can be applied, and these may be used in combination. However, in a more desirable aspect, a thermoplastic elastomer is applied as the thermoplastic resin.

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

FIG. 2 shows an enlarged sectional view of the tread portion 2. As shown in FIG. As shown in FIG. 2 , the tread portion 2 includes a tread reinforcing layer 10 inside the center position of the thickness of the tread portion 2 in the tire radial direction. This configuration means that the tread reinforcing layer 10 is arranged radially inward of the center position at least on the tire equatorial plane C. As shown in FIG. In a preferred embodiment,
50% or more, more preferably 80% or more of the volume of the tread reinforcing layer 10 is arranged radially inward of the center position. As a more desirable aspect, in this embodiment, the entire tread reinforcing layer 10 is arranged radially inward of the center position.

The tread reinforcing layer 10 is a member having higher rigidity than the thermoplastic resin forming the tire inner cavity surface 5, and can suppress the growth of the tire outer diameter. 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 width direction grooves extending in the tire axial direction. The outermost surface means the surface of the tread portion 2 that can come into contact with the road surface during running of the tire.

The thickness of the tread portion 2 described above is the distance in the tire normal direction from the outermost surface of the tread portion 2 to the inner cavity surface of the tire in the radial cross section of the tire. When the grooves 11 are present on the outermost surface of the tread portion 2, the thickness of the tread portion 2 shall be measured in a hypothetical state in which the grooves 11 are filled.

In the present disclosure, 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 refers to the entire circumference of the tire that touches the ground when the tire having the tread portion 2 in which all of the plurality of grooves 11 are filled is in the normal state and the tread portion 2 is pressed against a plane at a camber angle of 0°. It refers to the total contact area over the Similarly, the area of the groove can be calculated by determining the area of the groove on the ground contact surface of the entire circumference of the tire. These can be easily measured by applying ink or the like to the surface of the tire and transferring it.

In the present disclosure, by adopting the above configuration, deformation of the tire 1 due to 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 always under pressure from the air filled in the tire. For this reason, in a tire having a tire inner cavity surface 5 made of a thermoplastic resin, the tire inner cavity surface is plasticized and deformed by heat generated during running, which leads to growth of the tire outer diameter and local and plastic deformation of the tread portion. deformation occurs. As a result, there is a concern that rolling resistance will deteriorate, among other things. To address such a problem, according to the present disclosure, the tread reinforcing layer 10 is disposed further inside in the tire radial direction, so that the entire tread portion 2 can absorb the deformation while preventing the tire outer diameter from growing.

In addition, in the present disclosure, the negative rate of the tread portion 2 is 20% or more, so that the heat of the tread portion 2 can be easily released from the wall surfaces of the grooves 11 . Further, when the negative ratio is 50% or less, local deformation of the outermost surface of the tread portion 2 is suppressed, and heat generation thereof can be prevented. In the present disclosure, due to such a mechanism, in a pneumatic tire in which at least the tire inner cavity surface 5 is made of a thermoplastic resin, deformation of the tire due to heat generation during running can be suppressed, and thus deterioration of rolling resistance can be suppressed. it is conceivable that.

A more detailed configuration of the present embodiment will be described below. Each configuration described below represents a specific aspect of the present embodiment. Therefore, it goes without saying that the present disclosure can exhibit the above effects even if it does not have the configuration described below. Further, even if any one of the configurations described below is applied alone to the tire of the present disclosure having the features described above, an improvement in performance according to each configuration can be expected. Furthermore, when some of the respective configurations described below are applied in combination, it is possible to expect a combined improvement in performance according to each configuration.

As shown in FIG. 1, the tread portion 2 is composed of a tread contacting element 8 and a lumen surface member 14. As shown in FIG. The tread ground-contacting element 8 of this embodiment has, for example, a single-layer structure formed from a single composition. In other embodiments, the tread-contacting element 8 may be formed of multiple layers using different compositions, for example, the base tread portion and the undertread portion.

In this embodiment, the tread contact element 8 and the inner cavity surface member 14 have a two-layer structure made of different compositions. Tread-contacting element 8 is, for example, constructed of a different thermoplastic elastomer than lumen surface member 14 . Alternatively, the tread contact element 8 may be constructed from a rubber composition. Also, the present disclosure is not limited to the embodiments described above, and the tread portion 2 may be a single-layer construction in which the tread-contacting element 8 and the lumen surface member 14 are formed of the same composition. In this case, it is desirable that the tread portion 2 be entirely made of a thermoplastic resin.

As in this embodiment, when the tread contact element 8 and the inner cavity surface member 14 are composed of different compositions, the air permeability coefficient of the inner cavity surface member 14 is higher than that of the inner cavity surface member 14 from the viewpoint of retaining air inside the tire. It is preferably lower than the air permeability coefficient of element 8 . The air permeability coefficient is a material-specific value that represents the air permeability coefficient, and at a temperature of 30 ° C., in accordance with JIS K 7126-7, plastics - film and sheet - gas permeability test method - Part 1 : Measured by the differential pressure method.

A pair of side portions 13 are provided on the outer side of the tread portion 2 in the axial direction of the tire. In the embodiment shown in FIG. 1, the side portion 13 has a single layer structure made 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 in order to improve fitting. In another embodiment, the side portion 13 is divided into a plurality of members, and a bead apex or a rubber chafer is formed like a normal pneumatic tire in order to achieve the performance required according to the application, such as steering stability and ride comfort. It is also possible to assign a role such as

As shown in FIG. 2, the tread reinforcing layer 10 includes, for example, a plurality of cords 16 and a covering portion 17 that covers the cords 16.

For the cord 16, for example, an organic fiber cord or steel cord is used. The cord 16 of this embodiment is, for example, spirally wound at an angle of 5° or less with respect to the tire circumferential direction. Such a cord 16 can reliably suppress the growth of the tire outer diameter. However, the cords 16 are not limited to such a mode, and the cords 16 may be inclined at 30 to 60° with respect to the tire circumferential direction, like belt cords of general tires. The tread reinforcing layer 10 is composed of a layer composed of a plurality of cords 16 inclined in a first direction with respect to the tire circumferential direction and a plurality of cords 16 inclined in a second direction opposite to the first direction. A layer may be included.

The covering part 17 is composed of, for example, a topping rubber having adhesiveness. This effectively suppresses peeling of the tread reinforcing layer 10 . However, it is not limited to such an aspect, and the covering portion 17 may be made of a thermoplastic resin. In this case, it is more desirable that the covering portion 17 is made of a thermoplastic elastomer. This further improves the tire recycling performance.

FIG. 3 shows an enlarged cross-sectional view of the tread portion 2 of another embodiment. As shown in FIG. 3, the tread reinforcing layer 10 of this embodiment includes a thermoplastic resin, and more desirably is entirely composed of a thermoplastic resin. That is, this tread reinforcing layer 10 does not contain cords. This further improves recycling performance. Needless to say, the thermoplastic resin of the tread reinforcing layer 10 has higher rigidity than the thermoplastic resin forming the inner cavity surface 5 of the tire. Further, it is more desirable to apply a thermoplastic elastomer to the thermoplastic resin of the tread reinforcing layer 10 .

FIG. 4 shows an enlarged cross-sectional view of the tread portion 2 of still another embodiment. As shown in FIG. 4, the tread reinforcing layer 10 of this embodiment is covered with a thermoplastic resin forming the inner cavity surface 5 of the tire. More specifically, a plurality of cords 16 forming the tread reinforcing layer 10 are embedded inside the thermoplastic resin forming the inner cavity surface 5 of the tire. In such an embodiment, the thermoplastic resin forming the inner cavity surface 5 of the tire is used as the covering portion of the tread reinforcing layer 10, so that the manufacturing cost of the tire can be reduced.

As shown in FIG. 2, the axial length L1 of the tread reinforcing layer 10 is 25% to 81% of the tire maximum width W1. 3 and 4, the length of the tread reinforcing layer 10 is similarly defined. Such a tread reinforcing layer 10 can suppress an increase in tire outer diameter while suppressing an increase in tire manufacturing cost and tire weight.

The distance d2 from the outermost surface of the tread portion 2 to the tread reinforcing layer 10 is, for example, 65% to 95% of the thickness d1 of the tread portion 2, preferably 80% to 90%. As a result, the above-described effects are exhibited more reliably. The distance d2 corresponds to the distance in the normal direction of the tire from the outermost surface of the tread portion 2 to the outer surface of the tread reinforcing layer 10 on the radially outer side of the tire. The outer surface of the tread reinforcing layer 10 means the outer surface of the covering portion 17 of the tread reinforcing layer 10 in the embodiment shown in FIG. 2, and the outer surface of the cord 16 in the embodiment shown in FIG. .

The tensile elastic modulus Ad of the tread reinforcing layer 10 is greater than the tensile elastic modulus of the thermoplastic resin forming the inner cavity surface 5 of the tire. Specifically, the tensile elastic modulus Ad of the tread reinforcing layer 10 is desirably 100 MPa or more. As a result, deformation of the tread portion 2 is reliably suppressed, and deterioration of rolling resistance can be suppressed. The tensile elastic modulus of the tread reinforcing layer 10 was determined by taking a test sample extending from the tread reinforcing layer 10 in a width of 10 mm and extending 40 mm or more in the tire circumferential direction, and using a tensile tester to apply tensile deformation to an area of 10 mm in width and 40 mm in length. and calculated from the slope of the stress at that time. At this time, the deformation speed of the sample is 200 mm/min, and the measurement temperature is room temperature. From the stress values at 0.05% and 0.25% deformation of the obtained stress-strain curve, the slope is calculated and obtained as the tensile elastic modulus. If the tread reinforcing layer is a composite of cords and thermoplastic resin, the composite state is used for calculation.

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

The negative rate of the tread portion 2 is desirably 25% to 40%, desirably 25% to 35%. Such a tread portion 2 can exhibit excellent heat dissipation while local deformation is suppressed.

The multiple grooves 11 of the present embodiment include multiple circumferential grooves extending in the tire circumferential direction and multiple width direction grooves (not shown) extending in the tire axial direction. The circumferential groove negative rate, which is the ratio of the total opening area of the plurality of circumferential grooves to the virtual ground contact area, is preferably 10% to 40%. Further, the width direction groove negative ratio, which is the ratio of the total opening area of the plurality of width direction grooves to the virtual ground contact area, is preferably 10% to 40%. As a result, the rigidity of the tread portion 2 in the tire circumferential direction and the rigidity in the tire axial direction are ensured 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. As a result, wet performance and steering stability are improved in a well-balanced manner. The volume of the tread portion 2 means the total volume of the tread portion 2 defined by the tire normal line passing through the end of the outermost surface of the tread portion 2 in the tire axial direction.

The tread contact element 8 is a part for contacting the road surface, and in this embodiment, it is made of general vulcanized rubber for tires. Also, a known tread rubber composition can be applied to the tread contact element 8 of the present embodiment. However, in order to improve recyclability, the tread contact element 8 may partially contain thermoplastic resin, and the entire tread contact element 8 may be made of thermoplastic resin. In this case, the tread contact element 8 is more preferably made entirely of thermoplastic elastomer.

FIG. 5 shows a meridional cross-sectional view of the tire 1 of another embodiment of the present disclosure. As shown in FIG. 5, the tire 1 of this embodiment includes, for example, a toroidal tire frame member 7 including a pair of bead portions 4, and a tread contact element 8 forming the outermost surface of the tread portion 2. . At least equip. The tire frame member 7 constitutes the bead portion 4 and the sidewall portion 3 . In addition, the tire frame member 7 includes an undertread portion 2 d that is arranged radially inward of the tread contact element 8 . The undertread portion 2d is a member that supports the tread contact element 8, and is continuous with the sidewall portions 3 on both sides. As such, the present disclosure is not limited to the embodiments shown in FIGS. Aspects shall also be included.

Although the pneumatic tire according to one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the specific embodiments described above, and can be implemented with various modifications.

A pneumatic tire for a passenger car having the structure shown in FIG. As a comparative tire, a tire having the structure shown in FIG. 1 and a negative rate of 55% was experimentally produced. The tire of the comparative example is substantially the same as the tire of the example except for the above items. Each test tire was tested for rolling resistance to evaluate the degree of tread deformation. Common specifications and test methods are as follows.
Tire size: 195/65R15
Rim: 15 x 6.0J
Tire pressure: 250kPa

<Rolling resistance>
Rolling resistance was measured when the test tires were run on a drum tester. The results are indicated by the reciprocal of the rolling resistance, and are indicated by an index with the comparative example being 100. It shows that rolling resistance is so small that a numerical value is large.
The results of the tests are shown in Tables 1-5.

As shown in Tables 1 to 5, it was confirmed that the tires of Examples had low rolling resistance and suppressed tire deformation due to heat generation during running.

[Appendix]
The present disclosure includes the following aspects.

[Present Disclosure 1]
A pneumatic tire having a tread portion,
At least the inner cavity surface of the tire is made of a thermoplastic resin,
The tread portion includes a tread reinforcing layer radially inward of the central position of the thickness of the tread portion,
A plurality of grooves are provided on the outermost surface of the tread portion,
The negative rate, which is the ratio of the total open area of the plurality of grooves to the virtual ground contact area in which all the grooves are filled, is 20% to 50%.
pneumatic tires.
[Disclosure 2]
The pneumatic tire according to the present disclosure 1, wherein the axial length of the tread reinforcing layer is 25% to 81% of the tire maximum width.
[Disclosure 3]
The pneumatic tire according to the

present disclosure

1 or 2, wherein the tread reinforcing layer contains a thermoplastic resin.
[Disclosure 4]
4. The pneumatic tire according to any one of present disclosures 1 to 3, wherein the tread reinforcing layer has a tensile modulus of 100 MPa or more.
[Disclosure 5]
5. The pneumatic tire according to any one of the present disclosures 1 to 4, wherein the tread reinforcing layer is covered with the thermoplastic resin forming the inner cavity surface of the tire.
[Disclosure 6]
6. The pneumatic tire according to any one of present disclosures 1 to 5, wherein the tread reinforcing layer includes a plurality of cords made of organic fibers or metals.
[Present Disclosure 7]
7. The pneumatic tire according to any one of present disclosures 1 to 6, wherein the distance from the outermost surface of the tread portion to the tread reinforcing layer is 80% to 90% of the thickness of the tread portion.
[Disclosure 8]
The outermost surface of the tread portion is provided with a plurality of circumferential grooves extending in the tire circumferential direction,
8. The pneumatic tire according to any one of present disclosures 1 to 7, wherein a circumferential groove negative rate, which is a ratio of the total open area of the plurality of circumferential grooves to the virtual ground contact area, is 10% to 40%.
[Disclosure 9]
The outermost surface of the tread portion is provided with a plurality of width direction grooves extending in the tire axial direction,
The pneumatic tire according to any one of present disclosures 1 to 8, wherein a width direction groove negative rate, which is a ratio of the total opening area of the plurality of width direction grooves to the virtual ground contact area, is 10% to 40%.
[Present Disclosure 10]
The pneumatic tire according to any one of present disclosures 1 to 9, wherein the total volume of the plurality of grooves is 2.0% to 10.0% of the volume of the tread portion.
[Present Disclosure 11]
The pneumatic tire according to any one of present disclosures 1 to 10, wherein the tread portion contains a thermoplastic resin.
[Present Disclosure 12]
The pneumatic tire according to any one of present disclosures 1 to 11, wherein the negative rate is 25% to 35%.
[Disclosure 13]
13. The pneumatic tire according to any one of present disclosures 1 to 12, wherein the thermoplastic resin includes a thermoplastic elastomer having rubber-like elasticity in a cooled state.
[Present Disclosure 14]
The tread portion includes a tread ground-contacting element that constitutes the outermost surface and a lumen surface member that constitutes the tire lumen surface,
14. The pneumatic tire according to any one of the present disclosures 1-13, wherein the air permeability coefficient of the lumen surface member is lower than the air permeability coefficient of the tread-contacting element.
[Disclosure 15]
A value Ad×d2/d1 (MPa ) is 100 MPa or more, the pneumatic tire according to any one of present disclosures 1 to 14.

Claims

A pneumatic tire having a tread portion,
At least the inner cavity surface of the tire is made of a thermoplastic resin,
The tread portion includes a tread reinforcing layer radially inward of the central position of the thickness of the tread portion,
A plurality of grooves are provided on the outermost surface of the tread portion,
The negative rate, which is the ratio of the total open area of the plurality of grooves to the virtual ground contact area in which all the grooves are filled, is 20% to 50%.
pneumatic tires.
The pneumatic tire according to claim 1, wherein the axial length of the tread reinforcing layer is 25% to 81% of the maximum width of the tire.
The pneumatic tire according to claim 1 or 2, wherein the tread reinforcing layer contains a thermoplastic resin.
The pneumatic tire according to any one of claims 1 to 3, wherein the tread reinforcing layer has a tensile modulus of 100 MPa or more.
The pneumatic tire according to any one of claims 1 to 4, wherein the tread reinforcing layer is covered with the thermoplastic resin forming the inner cavity surface of the tire.
The pneumatic tire according to any one of claims 1 to 5, wherein the tread reinforcing layer includes a plurality of cords made of organic fibers or metal.
The pneumatic tire according to any one of claims 1 to 6, wherein the distance from the outermost surface of the tread portion to the tread reinforcing layer is 80% to 90% of the thickness of the tread portion.
The outermost surface of the tread portion is provided with a plurality of circumferential grooves extending in the tire circumferential direction,
The pneumatic according to any one of claims 1 to 7, wherein a circumferential groove negative rate, which is a ratio of the total opening area of the plurality of circumferential grooves to the virtual ground contact area, is 10% to 40%. tire.
The outermost surface of the tread portion is provided with a plurality of width direction grooves extending in the tire axial direction,
The pneumatic according to any one of claims 1 to 8, wherein a width direction groove negative rate, which is a ratio of the total opening area of the plurality of width direction grooves to the virtual ground contact area, is 10% to 40%. tire.
The pneumatic tire according to any one of claims 1 to 9, wherein the total volume of said plurality of grooves is 2.0% to 10.0% of the volume of said tread portion.
The pneumatic tire according to any one of claims 1 to 10, wherein the tread portion contains a thermoplastic resin.
The pneumatic tire according to any one of claims 1 to 11, wherein the negative rate is 25% to 35%.
The pneumatic tire according to any one of claims 1 to 12, wherein the thermoplastic resin includes a thermoplastic elastomer having rubber-like elasticity in a cooled state.
The tread portion includes a tread ground-contacting element that constitutes the outermost surface and a lumen surface member that constitutes the tire lumen surface,
14. A pneumatic tire according to any preceding claim, wherein the lumen surface member has an air permeability coefficient lower than the air permeability coefficient of the tread-contacting element.
A value Ad×d2/d1 (MPa ) is 100 MPa or more.