Pneumatic tires

Abstract

To provide a pneumatic tire whose at least a tire inner cavity surface is composed of a thermoplastic resin which suppresses deformation of the tire due to heat generation during travelling.SOLUTION: A pneumatic tire has a tread part 2. At least a tire inner cavity surface 5 is composed of a thermoplastic resin. The tread part 2 includes a tread reinforcement layer 10 at the tire radial direction inner side of a central position of a thickness of the tread part 2. A plurality of grooves 11 are provided on the outermost surface of the tread part 2. A negative rate that is a ratio of the total opening area of the plurality of grooves 11 to a virtual contact area where all the plurality of grooves 11 are embedded is 20% to 50%.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] Generally, pneumatic tires are mainly made of rubber materials, but rubber materials have a problem in that they are difficult to recycle. In recent years, various pneumatic tires including components made of materials with excellent recyclability have been proposed. For example, Patent Document 1 below proposes a tire in which a thermoplastic resin is used for the tire frame. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6138695 Summary of the Invention [Problem to be solved by the invention]

[0004] The tire of Patent Document 1 has a tire inner cavity surface made of a thermoplastic resin. There is a concern that the tire inner cavity surface of such a tire will be plasticized and deformed due to heat generated during running. Specifically, if the tire inner cavity surface is plasticized, the tire outer diameter will grow due to the tire internal pressure and the tread part will be locally and plastically deformed, which may worsen the rolling resistance.

[0005] The present invention was devised in consideration of the above-described circumstances, and has as its main objective to suppress tire deformation due to heat generation during driving and suppress deterioration of rolling resistance during continuous driving in a pneumatic tire in which at least the tire inner cavity surface is made of thermoplastic resin. [Means for solving the problem]

[0006] The present invention relates to a pneumatic tire having a tread portion, at least the tire inner cavity surface being made of a thermoplastic resin, the tread portion including a tread reinforcing layer radially inward of the center position of the thickness of the tread portion, a plurality of grooves being provided on the outermost surface of the tread portion, and a negative ratio, which is the ratio of the total opening area of ​​the plurality of grooves to the virtual contact area obtained by filling all of the plurality of grooves, is 20% to 50%.

[0007] In the pneumatic tire of the present invention, the length of the tread reinforcing layer in the tire axial direction is desirably 25% to 81% of the maximum width of the tire.

[0008] In the pneumatic tire of the present invention, it is desirable that the tread reinforcing layer contains a thermoplastic resin.

[0009] In the pneumatic tire of the present invention, the tread reinforcing layer desirably has a tensile modulus of 100 MPa or more.

[0010] In the pneumatic tire of the present invention, it is preferable that the tread reinforcing layer is covered with the thermoplastic resin that constitutes the tire cavity surface.

[0011] In the pneumatic tire of the present invention, it is preferable that the tread reinforcing layer includes a plurality of cords made of organic fiber or metal.

[0012] In the pneumatic tire of the present invention, the distance from the outermost surface of the tread portion to the tread reinforcing layer is desirably 80% to 90% of the thickness of the tread portion.

[0013] In the pneumatic tire of the present invention, a plurality of circumferential grooves extending in the circumferential direction of the tire are provided on the outermost surface of the tread portion, and a circumferential groove negative ratio, which is the ratio of the total opening area of ​​the plurality of circumferential grooves to the virtual contact area, is preferably 10% to 40%.

[0014] In the pneumatic tire of the present invention, a plurality of widthwise grooves extending in the tire axial direction are provided on the outermost surface of the tread portion, and a widthwise groove negative ratio, which is the ratio of the total opening area of ​​the plurality of widthwise grooves to the virtual contact area, is desirably 10% to 40%.

[0015] In the pneumatic tire of the present invention, the total volume of the plurality of grooves is desirably 2.0% to 10.0% of the volume of the tread portion.

[0016] In the pneumatic tire of the present invention, it is preferable that the tread portion contains a thermoplastic resin. Effect of the Invention

[0017] By adopting the above-described configuration, the pneumatic tire of the present invention can suppress deformation of the tire due to heat generation during running. [Brief description of the drawings]

[0018] [Figure 1] 1 is a meridian cross-sectional view of a pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the tread portion of FIG. [Diagram 3] FIG. 4 is an enlarged cross-sectional view of a tread portion according to another embodiment of the present invention. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a tread portion according to another embodiment of the present invention. [Diagram 5] FIG. 4 is a meridian cross-sectional view of a pneumatic tire according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a meridian cross-sectional view of a pneumatic tire 1 (hereinafter, sometimes simply referred to as tire 1) of this embodiment. Fig. 1 is a transverse cross-sectional view including a tire rotation axis of tire 1 in a normal state. As shown in Fig. 1, tire 1 of this embodiment is used as a pneumatic tire for passenger cars, for example. However, the present invention is not limited to such an embodiment, and may be applied to a pneumatic tire for motorcycles or a pneumatic tire for carts.

[0020] "Normal condition" means, in the case of tires for which various standards are established, that the tire is mounted on a normal rim, inflated to normal internal pressure, and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0021] A "genuine rim" is a rim that is specified for each tire by the standard system that includes the standard on which the tire is based, for example, "standard rim" for JATMA, "design rim" for TRA, and "measuring rim" for ETRTO. For tires not specified by a standard, a "genuine rim" refers to a rim that can be assembled and can hold internal pressure, that is, the rim with the smallest rim diameter and the next narrowest rim width that does not leak air from between the rim and tire.

[0022] "Normal internal pressure" is the pressure set for each tire by each standard, including the standard on which the tire is based. For JATMA, it is the "maximum pressure", for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is the "INFLATION PRESSURE". For tires for which no standard is set, the normal internal pressure is 250 kPa for passenger car tires and 350 kPa for tires with a normal load higher than that of passenger cars.

[0023] Here, passenger car tires refer to tires that are mounted on automobiles that have four wheels and a standard load capacity of 1000 kg or less.

[0024] The above-mentioned "normal load" refers to the maximum load capacity determined for each tire by the standard system including the standard on which the tire is based. For example, in the case of the JATMA standard (Japan Automobile Tire Manufacturers Association standard), it is the maximum load capacity based on the load index (LI), in the case of the TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of the ETRTO, it is the "LOAD CAPACITY". In the case of tires not specified by a standard, it is the virtual volume V (mm) excluding the rim of the tire calculated from the tire section width Lt (mm), tire outer diameter Dt (mm), tire section height Ht (mm), and pi. 3 ) Based on this, the value obtained using the following formula is treated as the normal load (kg). Normal load (kg) = 0.000011×V+175 V = {(Dt 2 -Ht 2 ) / 4}×π×Lt

[0025] The tire section width Lt (mm), tire section height Ht (mm), and tire outer diameter Dt (mm) can be measured directly from an actual tire or from a photographed image such as a CT scan image.

[0026] The tire outer diameter Dt is the outer diameter of the tire in its normal state, and the tire section width Lt is the width obtained by excluding the patterns, letters, etc. on the tire side from the linear distance between the sidewalls (total tire width) including all patterns, letters, etc. on the tire side in its normal state. The tire section height Ht is the height of the tire at the tire cross section, and can be calculated by subtracting the rim diameter (mm) from the tire outer diameter Dt and dividing the result by 2.

[0027] The tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portions 3 extend radially inward from the axial ends of the tread portion 2. The bead portions 4 are continuous with the radially inward ends of the sidewall portions 3. In the tread portion 2 of the tire 1, at least a tire cavity surface 5 is made of a thermoplastic resin.

[0028] In this specification, the term "thermoplastic resin" refers to a polymer compound that becomes fluid when heated and reversibly returns to a relatively hard and strong state when cooled again, and that can be molded without going through a vulcanization process like general rubber components for tires. Therefore, the thermoplastic resin referred to in this specification does not include general rubber components for tires (vulcanized rubber), but is a recyclable resin material. Whether or not a tire uses a thermoplastic resin can be determined from the temperature dependence of the elastic modulus of the tire components, etc.

[0029] In addition, in this specification, the thermoplastic resin includes a non-elastic thermoplastic resin that does not have rubber-like elasticity in a cooled state, and a thermoplastic elastomer that has rubber-like elasticity in a cooled state. A thermoplastic elastomer is a material that softens and flows with an increase in temperature, and becomes relatively hard and strong when cooled, and has rubber-like elasticity. In this specification, unless otherwise specified, both a non-elastic thermoplastic resin and a thermoplastic elastomer can be used as the thermoplastic resin, and these may be used in combination. However, in a more preferable embodiment, a thermoplastic elastomer is used as the thermoplastic resin.

[0030] 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 these may be used alone or in combination.

[0031] Fig. 2 shows 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 located radially inward of the center position of the thickness of the tread portion 2. This configuration means that the tread reinforcing layer 10 is disposed radially inward of the center position at least on the tire equatorial plane C. In a preferred embodiment, At least 50% of the volume of the tread reinforcing layer 10, more preferably at least 80% is disposed radially inward of the center position. As a more preferable aspect, in this embodiment, the entire tread reinforcing layer 10 is disposed radially inward of the center position.

[0032] The tread reinforcing layer 10 is a member having higher rigidity than the thermoplastic resin constituting the tire cavity surface 5, and can suppress the growth of the tire outer diameter. In addition, 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.

[0033] The thickness of the tread portion 2 is the distance in the tire normal direction from the outermost surface of the tread portion 2 to the tire cavity surface in the radial cross section of the tire. When grooves 11 are present on the outermost surface of the tread portion 2, the thickness of the tread portion 2 is measured in a hypothetical state in which the grooves 11 are filled.

[0034] 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 contact area of ​​the tread portion 2 in which all of the plurality of grooves 11 are filled, is 20% to 50%. The virtual contact area refers to the total contact area over the entire circumference of the tire that comes into contact with the ground when a tire having a 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 flat surface at a camber angle of 0°. Similarly, the area of ​​the groove portion can be calculated by determining the area of ​​the groove portion in the contact surface over the entire circumference of the tire. These can be simply measured by applying ink or the like to the tire surface and transferring it.

[0035] In the present invention, by adopting the above-mentioned configuration, it is possible to suppress deformation of the tire 1 due to heat generation during running, and to suppress deterioration of rolling resistance during continuous running. The following mechanism is presumed to be the reason for this.

[0036] The tire cavity surface 5 is constantly under pressure from the air filled in the tire. For this reason, in a tire in which the tire cavity surface 5 is made of a thermoplastic resin, the tire cavity surface is plasticized and deformed due to heat generated during running, which in turn causes the tire outer diameter to grow and localized plastic deformation of the tread portion. This is particularly a concern as it may worsen the rolling resistance. In response to this problem, in the present invention, the tread reinforcing layer 10 is disposed further inward in the tire radial direction, thereby preventing the tire outer diameter from growing and absorbing deformation throughout the tread portion 2.

[0037] Also, in the present invention, the negative ratio of the tread portion 2 is 20% or more, which makes it easier for heat to escape from the tread portion 2 through the wall surfaces of the grooves 11. Furthermore, the negative ratio is 50% or less, which suppresses local deformation of the outermost surface of the tread portion 2 and prevents heat generation. It is believed that, due to this mechanism, in the present invention, in a pneumatic tire in which at least the tire cavity surface 5 is made of a thermoplastic resin, tire deformation caused by heat generation during running can be suppressed, and thus deterioration of rolling resistance can be suppressed.

[0038] A more detailed configuration of this embodiment will be described below. Each configuration described below shows a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configuration described below. In addition, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0039] As shown in Fig. 1, the tread portion 2 is composed of a tread ground contact element 8 and a lumen surface member 14. In this embodiment, the tread ground contact element 8 is, for example, a single-layer structure formed from a single composition. In other embodiments, the tread ground contact element 8 may be formed from a multi-layer structure using different compositions, such as a base tread portion and an undertread portion.

[0040] In this embodiment, the tread ground contact element 8 and the lumen surface member 14 have a two-layer structure made of different compositions. The tread ground contact element 8 is made of, for example, a thermoplastic elastomer different from the lumen surface member 14. In another embodiment, the tread ground contact element 8 may be made of a rubber composition. The present invention is not limited to the above embodiment, and the tread portion 2 may have a single-layer structure in which the tread ground contact element 8 and the lumen surface member 14 are formed of the same composition. In this case, it is desirable that the entire tread portion 2 is made of a thermoplastic resin.

[0041] When the tread grounding element 8 and the lumen surface member 14 are made of different compositions, as in this embodiment, it is preferable that the air permeability coefficient of the lumen surface member 14 is lower than the air permeability coefficient of the tread grounding element 8, from the viewpoint of retaining air inside the tire.

[0042] A pair of side portions 13 are provided on the axially outer sides of the tread portion 2. In the embodiment shown in Fig. 1, the side portions 13 have a single-layer structure made of a single composition, and constitute the sidewall portion 3 and the bead portion 4. The bead portion 4 includes a bead wire to improve fit. In another embodiment, the side portions 13 may be divided into a plurality of members, each of which may function as a bead apex or rubber chafer, as in a normal pneumatic tire, in order to achieve performance required depending on the application, such as steering stability and ride comfort.

[0043] 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 .

[0044] The cord 16 may be, for example, an organic fiber cord or a steel cord. The cord 16 of this embodiment is, for example, wound spirally 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 present invention is not limited to this embodiment, and the cord 16 may be, for example, inclined at 30 to 60° with respect to the tire circumferential direction like a belt cord of a general tire. The tread reinforcing layer 10 may include a layer made of a plurality of cords 16 inclined in a first direction with respect to the tire circumferential direction, and a layer made of a plurality of cords 16 inclined in a second direction opposite to the first direction.

[0045] The covering portion 17 is made of, for example, a topping rubber having adhesiveness. This effectively prevents the tread reinforcing layer 10 from peeling off. However, the present invention is not limited to this embodiment, and the covering portion 17 may be made of a thermoplastic resin. In this case, it is more preferable that the covering portion 17 is made of a thermoplastic elastomer. This further improves the recycling performance of the tire.

[0046] 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 contains a thermoplastic resin, and more preferably is entirely made of a thermoplastic resin. That is, the tread reinforcing layer 10 does not contain a cord. This further improves the recyclability. It goes without saying that the thermoplastic resin of the tread reinforcing layer 10 has higher rigidity than the thermoplastic resin constituting the tire inner cavity surface 5. It is more preferable that a thermoplastic elastomer is applied to the thermoplastic resin of the tread reinforcing layer 10.

[0047] 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 the thermoplastic resin that constitutes the tire cavity surface 5. More specifically, a plurality of cords 16 that constitute the tread reinforcing layer 10 are embedded inside the thermoplastic resin that constitutes the tire cavity surface 5. In this embodiment, the thermoplastic resin that constitutes the tire cavity surface 5 is used as the covering portion of the tread reinforcing layer 10, so that the manufacturing cost of the tire can be reduced.

[0048] 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 tire width W1. The length of the tread reinforcing layer 10 is similarly defined in the embodiments shown in Fig. 3 and Fig. 4. Such a tread reinforcing layer 10 can suppress the growth of the tire outer diameter while suppressing increases in tire manufacturing costs and tire weight.

[0049] 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, and preferably 80 to 90%. This makes it possible to more reliably achieve the above-mentioned effects. The distance d2 corresponds to the 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. Moreover, 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 means the outer surface of the cord 16 in the embodiment shown in FIG. 4.

[0050] The tensile modulus Ad of the tread reinforcing layer 10 is greater than the tensile modulus of the thermoplastic resin constituting the tire cavity surface 5. Specifically, the tensile modulus Ad of the tread reinforcing layer 10 is desirably 100 MPa or more. This reliably suppresses the deformation of the tread portion 2, and suppresses the deterioration of the rolling resistance. The tensile modulus of the tread reinforcing layer 10 is calculated from the slope of the stress when a test sample having a width of 10 mm and extending 40 mm or more in the tire circumferential direction is taken from the tread reinforcing layer 10 and tensilely deformed in a region of the test sample having a width of 10 mm and a length of 40 mm using a tensile tester. At this time, the deformation speed of the sample is 200 mm / min, and the measurement temperature is room temperature. The slope is calculated from the stress values ​​at 0.05% and 0.25% deformation of the obtained stress-strain curve, and is obtained as the tensile modulus. When the tread reinforcing layer is a composite of cords and thermoplastic resin, the calculation is performed in the composite state.

[0051] 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 to reinforce the tread portion 2. From this perspective, in order to sufficiently reinforce the tread portion 2, the value Ad×d2 / d1 (MPa) obtained by multiplying the tensile 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 100 MPa or more, and more preferably 200 MPa or more.

[0052] The negative ratio of the tread portion 2 is preferably 25% to 40%, and more preferably 25% to 35%. Such a tread portion 2 can exhibit excellent heat dissipation properties while suppressing local deformation.

[0053] The grooves 11 of this embodiment include 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. A circumferential groove negative ratio, which is a ratio of a total opening area of ​​the plurality of circumferential grooves to a virtual contact area, is preferably 10% to 40%. Also, a widthwise groove negative ratio, which is a ratio of a total opening area of ​​the plurality of widthwise grooves to a virtual contact area, is preferably 10% to 40%. This ensures a good balance between the rigidity of the tread portion 2 in the tire circumferential direction and the rigidity in the tire axial direction.

[0054] 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 provides a well-balanced improvement in wet performance and steering stability. Note that 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 axial end of the outermost surface of the tread portion 2.

[0055] The tread ground contact element 8 is a portion for contacting the road surface, and in this embodiment is made of general vulcanized rubber for tires. Also, a known tread rubber composition can be applied to the tread ground contact element 8 of this embodiment. However, in order to improve recyclability, the tread ground contact element 8 may contain a thermoplastic resin in part, and the entire tread ground contact element 8 may be made of a thermoplastic resin. In this case, it is more preferable that the entire tread ground contact element 8 is made of a thermoplastic elastomer.

[0056] FIG. 5 shows a meridian cross section of a tire 1 according to another embodiment of the present invention. As shown in FIG. 5, the tire 1 according to this embodiment includes, for example, a toroidal 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 portions 4 and the sidewall portion 3. The tire frame member 7 also includes an undertread portion 2d disposed on the tire radially inner side of the tread ground contact element 8. The undertread portion 2d is a member that supports the tread ground contact element 8, and is connected to the sidewall portions 3 on both sides. Thus, the present invention is not limited to the embodiments shown in FIGS. 1 to 4, and includes the embodiment shown in FIG. 5 as long as the tire inner cavity surface 5 of the tread portion 2 is made of a thermoplastic resin.

[0057] Although the pneumatic tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described specific embodiment and can be modified and implemented in various aspects. EXAMPLES

[0058] A pneumatic tire for passenger cars having the structure shown in FIG. 1 was prototyped based on the specifications in Tables 1 to 5. As a comparative tire, a tire having the structure shown in FIG. 1 and a negative rate of 10% was prototyped. The comparative tire was substantially the same as the example tire except for the above-mentioned points. For each test tire, the rolling resistance was tested to evaluate the degree of deformation of the tread portion. The common specifications and test methods are as follows. Tire size: 195 / 65R15 Rim: 15×6.0J Tire pressure: 250kPa

[0059] <Rolling resistance> The rolling resistance was measured when the test tire was run on a drum test machine. The results are shown as the reciprocal of the rolling resistance, and are expressed as an index with the comparative example being 100. The higher the value, the lower the rolling resistance. The test results are shown in Table 1.

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] [Table 4]

[0064] [Table 5]

[0065] As shown in Tables 1 to 5, it was confirmed that the tires of the examples had low rolling resistance and suppressed tire deformation due to heat generation during running. [Explanation of symbols]

[0066] 2 Tread section 5 Tire inner cavity surface 10 Tread reinforcement layer 11 Groove

Claims

1. A pneumatic tire having a tread portion, At least the tire inner cavity surface is made of a thermoplastic resin, The tread portion includes a tread reinforcing layer located radially inward of a center position of a thickness of the tread portion, A plurality of grooves are provided on the outermost surface of the tread portion, a negative ratio, which is a ratio of a total opening area of ​​the plurality of grooves to a virtual ground contact area in which all of the plurality of grooves are filled, is 20% to 50%; The tread reinforcing layer is covered with the thermoplastic resin constituting the tire inner cavity surface. Pneumatic tires.

2. A pneumatic tire having a tread portion, At least the tire inner cavity surface is made of a thermoplastic resin, The tread portion includes a tread reinforcing layer located radially inward of a center position of a thickness of the tread portion, A plurality of grooves are provided on the outermost surface of the tread portion, a negative ratio, which is a ratio of a total opening area of ​​the plurality of grooves to a virtual ground contact area in which all of the plurality of grooves are filled, is 20% to 50%; 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. Pneumatic tires.

3. A pneumatic tire having a tread portion, At least the tire inner cavity surface is made of a thermoplastic resin, The tread portion includes a tread reinforcing layer located radially inward of a center position of a thickness of the tread portion, A plurality of grooves are provided on the outermost surface of the tread portion, a negative ratio, which is a ratio of a total opening area of ​​the plurality of grooves to a virtual ground contact area in which all of the plurality of grooves are filled, is 20% to 50%; The tread portion contains a thermoplastic resin. Pneumatic tires.

4. A pneumatic tire as described in any one of claims 1 to 3, wherein the axial length of the tread reinforcing layer is 25% to 81% of the maximum width of the tire.

5. A pneumatic tire as described in any one of claims 1 to 4, wherein the tread reinforcing layer contains a thermoplastic resin.

6. A pneumatic tire as described in any one of claims 1 to 5, wherein the tensile modulus of the tread reinforcing layer is 100 MPa or more.

7. A pneumatic tire as described in any one of claims 1 to 6, wherein the tread reinforcing layer includes a plurality of cords made of organic fibers or metal.

8. A plurality of circumferential grooves extending in the circumferential direction of the tire are provided on the outermost surface of the tread portion, 8. The pneumatic tire according to claim 1, wherein a circumferential groove negative ratio, which is a ratio of a total opening area of ​​the plurality of circumferential grooves to the virtual contact area, is 10% to 40%.

9. A plurality of widthwise grooves extending in the tire axial direction are provided on the outermost surface of the tread portion, 9. The pneumatic tire according to claim 1, wherein a widthwise groove negative ratio, which is a ratio of a total opening area of ​​the widthwise grooves to the virtual contact area, is 10% to 40%.

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

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