Pneumatic tire

Abstract

Provided is a pneumatic tire capable of improving durability of the tire. In the pneumatic tire comprising a tread portion 1 extending in a tire circumferential direction to form an annular shape, a pair of side wall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged on the inner side of these side wall portions 2 in a tire radial direction, with at least one carcass layer 4 mounted between the pair of bead portions 3, the carcass layer 4 includes a plurality of carcass cords inclined by 5° or more with respect to the tire radial direction, these carcass cords are covered with coat rubber, a transponder 20 is disposed so as to abut against the carcass layer 4 in the side wall portion 2 and be on the inner side of the carcass layer 4 in a tire width direction, a reinforcing rubber layer 10 is disposed on the inner side of the transponder 20 in the tire width direction, and a storage elastic modulus E'r at 80°C of the reinforcing rubber layer 10 is higher than a storage elastic modulus E'c at 80°C of the coat rubber covering the carcass cords.

Description

Pneumatic tire

[0001] The present invention relates to a pneumatic tire with an embedded transponder, and more particularly, to a pneumatic tire that enables improvement of tire durability.

[0002] In pneumatic tires, embedding an RFID tag (transponder) inside the tire has been proposed (for example, see Patent Document 1). For example, in competition tires that require high rigidity, carcass cords are inclined with respect to the radial direction (hereinafter also referred to as the tire radial direction) in order to increase rigidity. When the carcass cords are inclined in this manner, a change in the angle of the carcass cords occurs due to deformation during tire rotation, which generates large stress on the transponder and causes a problem of separation. On the other hand, when a transponder is embedded in a location with little deformation, there is a problem that the communication performance is deteriorated due to the influence of metal members around the transponder.

[0003] Japanese Unexamined Patent Publication No. 7-137510

[0004] An object of the present invention is to provide a pneumatic tire that enables improvement of tire durability.

[0005] To achieve the above object, the pneumatic tire of the present invention includes an annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radial inner side of these sidewall portions, with at least one carcass layer mounted between the pair of bead portions, wherein the carcass layer includes a plurality of carcass cords inclined at 5° or more with respect to the tire radial direction, these carcass cords are covered with a coat rubber, a transponder is disposed in contact with the carcass layer in the sidewall portion and on the tire width direction inner side of the carcass layer, a reinforcing rubber layer is disposed on the tire width direction inner side of the transponder, and the storage elastic modulus E'r (80°C) at 80°C of the reinforcing rubber layer is higher than the storage elastic modulus E'c (80°C) at 80°C of the coat rubber covering the carcass cords.

[0006] In this invention, the carcass layer includes a plurality of carcass cords inclined at 5° or more with respect to the tire radial direction, these carcass cords are covered with a coating rubber, a transponder is positioned in contact with the carcass layer in the sidewall portion and inward from the carcass layer in the tire width direction, and a reinforcing rubber layer is positioned inward from the transponder in the tire width direction, and the storage modulus of elasticity E'r(80°C) of the reinforcing rubber layer at 80°C is higher than the storage modulus of elasticity E'c(80°C) of the coating rubber covering the carcass cords, so this reinforcing rubber layer can suppress deformation of the sidewall portion and improve the durability of the tire.

[0007] In the pneumatic tire of the present invention, the reinforcing rubber layer is preferably located on the innermost surface of the tire and partially positioned in the radial direction, and the carcass layer is preferably exposed over 40% or more of the surface area of ​​the inner surface of the tire. By arranging the reinforcing rubber layer in this manner, the tire can be made lighter and its high-speed durability can be improved.

[0008] It is preferable that the tanδr (80°C) of the reinforcing rubber layer at 80°C is higher than the tanδs (80°C) of the side rubber layer located in the sidewall. By making the tanδ (80°C) of the reinforcing rubber layer higher than that of the side rubber layer, the air inside the tire cavity can be heated earlier, and the internal tire pressure can be raised to the desired pressure. As a result, the temperature of the inner surface of the tire can be raised without raising the temperature of the sidewall, thus improving the tire's warm-up performance while maintaining tire durability.

[0009] Preferably, the chip portion of the transponder is positioned radially inward from the upper end of the bead filler that constitutes the bead portion. By positioning the transponder in this way, it can be placed in a location with less distortion, thereby effectively improving the durability of the tire.

[0010] The tip portion is preferably spaced at least 20 mm outward in the tire radial direction from the upper end of the bead core that constitutes the bead portion. By arranging the transponder in this way, the communication performance of the transponder can be improved.

[0011] Preferably, an identification label is placed on the outer surface of only one of the pair of sidewall sections, and a transponder is located on the other sidewall section. Having the identification label and transponder on the same side of the tire makes tire management easier and is therefore preferable.

[0012] In this invention, the storage modulus E' and the loss tangent tanδ are measured in accordance with JIS K6394 using a viscoelastic spectrometer under the specified conditions of tensile deformation mode, temperature, frequency of 10 Hz, initial strain of 10%, and dynamic strain of ±2%.

[0013] Figure 1 is a meridian cross-sectional view showing an example of a pneumatic tire according to an embodiment of the present invention. Figure 2 is a cross-sectional view showing an enlarged view of the main part of the pneumatic tire of Figure 1. Figure 3 is an explanatory diagram showing the inclination angle of the carcass cord of the pneumatic tire of Figure 1. Figure 4 is a perspective view showing a transponder arranged in the pneumatic tire of Figure 1. Figure 5 is a meridian cross-sectional view showing a modified example of a pneumatic tire according to an embodiment of the present invention.

[0014] The configuration of the present invention will be described in detail below with reference to the attached drawings. Figures 1 and 2 show a pneumatic tire according to an embodiment of the present invention.

[0015] As shown in Figure 1, the pneumatic tire of this embodiment comprises a tread portion 1 that extends in the circumferential direction of the tire and forms an annular shape, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged on the radially inward side of these sidewall portions 2.

[0016] Between the pair of bead portions 3, at least one (two in Figure 1) carcass layer 4 is mounted, consisting of multiple carcass cords arranged radially. The carcass cords are inclined at an angle of 5° or more with respect to the tire's radial direction. The inclination angle θ of the carcass cord in this invention (see Figure 3) is the acute angle of inclination of the carcass cord 4c with respect to the tire's radial direction, measured at the location where the transponder described later is placed. The inclination angle θ of the carcass cord is preferably in the range of 5° to 30°, and more preferably in the range of 15° to 22°. The carcass layer 4 is covered with a coating rubber. Organic fiber cords such as nylon or polyester are preferably used as the carcass cords constituting the carcass layer 4.

[0017] Both ends of the carcass layer 4 are folded back from the inside to the outside of the tire around each bead core 5, and are positioned to enclose the bead core 5 and the bead filler 6. The carcass layer 4 includes a main body portion which extends from the tread portion 1 through each sidewall portion 2 to each bead portion 3, and a winding portion which is wound up around the bead core 5 at each bead portion 3 and extends toward the sidewall portion 2. In the main body portion and the winding portion of the carcass layer 4, the inclination direction of the carcass cord 4c with respect to the tire radial direction is reversed, and the carcass cord 4c intersects between the layers of the main body portion and the winding portion. That is, the carcass layer 4 of the present invention has a so-called half-radial structure.

[0018] An annular bead core 5 is embedded in each bead portion 3, and a bead filler 6 made of a rubber composition with a triangular cross-section is arranged on the outer circumference of the bead core 5. In addition to the carcass layer 4, a fiber-reinforced reinforcing layer may also be provided around the bead core 5 or bead filler 6.

[0019] Multiple belt layers 7 (two in Figure 1) are embedded in the outer circumference side of the carcass layer 4 in the tread portion 1. The belt layers 7 include multiple reinforcing cords that are inclined with respect to the tire's circumferential direction, and the reinforcing cords are arranged to intersect each other between layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire's circumferential direction is set to, for example, a range of 10° to 40°. Steel cords are preferably used as the reinforcing cords in the belt layers 7.

[0020] On the outer circumference side of the belt layer 7, at least one belt cover layer 8 is arranged, with reinforcing cords arranged at an angle of, for example, 5° or less with respect to the circumferential direction of the tire, for the purpose of improving high-speed durability. In Figure 1, the belt cover layer 8 constitutes a pair of edge cover layers that cover only the ends of the belt layer 7. Organic fiber cords such as nylon or aramid are preferably used as the reinforcing cords of the belt cover layer 8.

[0021] In the above-described pneumatic tire, a reinforcing rubber layer 10 is provided on the inner surface of the sidewall portion 2. This reinforcing rubber layer 10, located on the innermost side in the tire width direction, is preferably provided continuously in the circumferential direction of the tire to suppress vibration, but it can also be provided intermittently. Furthermore, one end of the reinforcing rubber layer 10 should extend at least to the end of the belt layer 7, and the other end of the reinforcing rubber layer 10 should extend at least to the upper end 5e (the outer end in the radial direction of the tire) of the bead core 5. Note that since the reinforcing rubber layer 10 is not provided on the inner surface of the tread portion 1, the carcass layer 4 is exposed.

[0022] The storage modulus E'r(80°C) of the reinforcing rubber layer 10 at 80°C is set higher than the storage modulus E'c(80°C) of the coating rubber covering the carcass cords. In particular, the storage modulus E'r(80°C) of the reinforcing rubber layer 10 is preferably 1.5 times or more, and more preferably 2.0 times or more, than the storage modulus E'c(80°C) of the coating rubber. The storage modulus E'r(80°C) of the reinforcing rubber layer 10 is preferably in the range of 8 MPa to 18 MPa. Furthermore, the thickness of the reinforcing rubber layer 10 is preferably equal to or greater than the thickness of the carcass layer 4, and more preferably 1.5 times or more, than the thickness of the carcass layer 4.

[0023] Furthermore, in the above-described pneumatic tire, a transponder 20 is embedded inward in the tire width direction from the carcass layer 4. The transponder 20 is in contact with the carcass layer 4 in the sidewall portion 2 and is positioned inward in the tire width direction from the carcass layer 4. The transponder 20 also extends along the tire circumferential direction. The transponder 20 may be positioned so as to be inclined within a range of -10° to +10° with respect to the tire circumferential direction.

[0024] For example, an RFID (Radio Frequency Identification) tag can be used as the transponder 20. As shown in Figure 4, the transponder 20 has a chip unit 21 for storing data and an antenna 22 for contactlessly transmitting and receiving data. By using such a transponder 20, information about tires can be written to or read in a timely manner, and tires can be managed efficiently. RFID is an automatic identification technology that consists of a reader / writer having an antenna and a controller, and an ID tag having a chip unit and an antenna, and is capable of exchanging data wirelessly.

[0025] A columnar transponder 20, as shown in Figure 4, is preferable because it can follow the deformation of the tire in all directions. In this case, the antenna 22 of the transponder 20 protrudes from each end of the tip portion 21 and has a spiral shape. This allows it to follow the deformation of the tire during driving, improving the durability of the transponder 20. Furthermore, communication can be ensured by appropriately changing the length of the antenna 22.

[0026] Furthermore, it is preferable that the entire transponder 20 be covered with a rubber coating layer 23. This coating layer 23 is formed, for example, by sandwiching both the front and back surfaces of the transponder 20 between two rubber sheets to cover the entire transponder 20. By protecting the transponder 20 with this coating layer 23, the adhesion and durability of the transponder 20 can be improved.

[0027] In the pneumatic tire described above, the carcass layer 4 includes a plurality of carcass cords inclined at 5° or more with respect to the tire's radial direction, and these carcass cords are covered with a coating rubber. The transponder 20 is positioned in contact with the carcass layer 4 in the sidewall portion 2 and inward from the carcass layer 4 in the tire width direction, and the reinforcing rubber layer 10 is positioned inward from the transponder 20 in the tire width direction. Since the storage modulus of elasticity E'r (80°C) of the reinforcing rubber layer 10 at 80°C is higher than the storage modulus of elasticity E'c of the coating rubber covering the carcass cords, the deformation of the sidewall portion 2 can be suppressed by this reinforcing rubber layer 10, and the durability of the tire can be improved.

[0028] In the above-described pneumatic tire, the reinforcing rubber layer 10 is preferably positioned on the innermost surface of the tire and partially positioned in the radial direction. Furthermore, the carcass layer 4 is preferably exposed over 40% of the inner surface area of ​​the tire (in other words, the reinforcing rubber layer 10 covers 50% or less of the inner surface area of ​​the tire). It is also desirable that the carcass layer 4 is exposed over 70% or less of the inner surface area of ​​the tire (in other words, it is desirable that the reinforcing rubber layer 10 covers 20% or more of the inner surface area of ​​the tire). The reinforcing rubber layer 10 only needs to be on the side (one side) where the transponder 20 is positioned, but it may also be on both sides. If the reinforcing rubber layer 10 is on both sides, the length and position of the reinforcing rubber layer 10 may differ on each side. By positioning the reinforcing rubber layer 10 in this way, the tire can be made lighter and its high-speed durability can be improved.

[0029] The arrangement of the reinforcing rubber layer 10 described above is suitable for racing tires used only for a short period of time. Because racing tires have a much shorter lifespan than passenger car tires, it is not necessarily required to have an inner liner layer (air permeability prevention layer), and a half-radial structure that can increase rigidity is suitable because of the large rotational torque during driving. This half-radial structure causes distortion to the transponder located in the sidewall, but the arrangement of the reinforcing rubber layer 10 according to the present invention provides an excellent suppression effect against deformation of the sidewall 2. Furthermore, since it is beneficial to raise the temperature of the inner surface of the tire early in racing tires, setting tanδ as described below is even more suitable for racing tires.

[0030] It is preferable that the tanδr (80°C) of the reinforcing rubber layer 10 at 80°C is higher than the tanδs (80°C) of the side rubber layer located in the sidewall portion 2. In particular, it is more preferable that the tanδr (80°C) of the reinforcing rubber layer 10 is 1.2 times or more than the tanδs (80°C) of the side rubber layer. The tanδr (80°C) of the reinforcing rubber layer 10 is preferably in the range of 0.12 to 0.20. By making the tanδ of the reinforcing rubber layer 10 higher than that of the side rubber layer in this way, the air inside the tire cavity can be heated earlier, and the internal tire pressure can be raised to the desired pressure. As a result, the temperature of the inner surface of the tire can be raised without raising the temperature of the sidewall portion 2, thereby improving the tire's warm-up performance while maintaining the tire's durability.

[0031] The chip portion 21 is preferably positioned radially inward from the upper end 6e (the outer end in the tire radial direction) of the bead filler 6. By positioning the transponder 20 in this manner, it can be placed in a location with less distortion, thereby effectively improving the durability of the tire. Furthermore, the chip portion 21 is preferably spaced at least 20 mm radially outward from the upper end 5e of the bead core 5. That is, as shown in Figure 2, the distance d2 between the chip portion 21 and the upper end 5e of the bead core 5 should be 20 mm or more. By positioning the transponder 20 in this manner, the communication performance of the transponder can be improved. In general, it is desirable that the chip portion 21 be positioned within the region S in the tire radial direction shown in Figure 2.

[0032] In the above-described pneumatic tire, if an identification label is placed only on the outer surface of one of the pair of sidewall sections 2, it is preferable that a transponder 20 be placed on this sidewall section 2. The identification label can be a barcode, QR code (registered trademark), numbers, letters, or a combination thereof. Placing the identification label and the transponder 20 on the same side of the tire in this manner facilitates tire management and is therefore preferable. In particular, writing the information from the identification label onto the transponder 20 makes management easier.

[0033] Furthermore, in the above-mentioned pneumatic tire, the relative permittivity of the coating layer 23 is preferably 7 or less, and more preferably 2 to 5. In addition, it is preferable that the relative permittivity of the coating layer 23 is set lower than the relative permittivity of the rubber member arranged adjacent to the coating layer 23. By setting the relative permittivity of the coating layer 23 in this way, radio wave transmission when the transponder 20 radiates radio waves can be ensured, and the communication performance of the transponder 20 can be effectively improved. The relative permittivity of the rubber constituting the coating layer 23 is a relative permittivity of 860 MHz to 960 MHz at room temperature. Here, room temperature conforms to the standard conditions of the JIS standard, which is 23 ± 2°C and 60% ± 5% RH. The rubber is treated at 23°C and 60% RH for 24 hours, and then the relative permittivity is measured by the capacitance method. The aforementioned range of 860 MHz to 960 MHz corresponds to the current allocated frequencies for RFID in the UHF band. If the above allocated frequencies are changed, the relative permittivity for that range of allocated frequencies should be defined as described above.

[0034] The coating layer 23 preferably contains 20 phr or less of carbon black. Furthermore, it is more preferable that the coating layer 23 contains 3 phr or more of carbon black. When the coating layer 23 contains a specific amount of carbon black in this way, the dielectric constant of the coating layer 23 can be reduced, thereby improving the communication performance of the transponder 20. In this specification, "phr" means parts by weight per 100 parts by weight of the rubber component (elastomer).

[0035] The above-described embodiment shows an example without an inner liner layer, but it is not limited to this. As shown in Figure 5, an inner liner layer 9 can be placed on the innermost surface of the tire, and the transponder 20 can be placed between the carcass layer 4 and the reinforcing rubber layer 10.

[0036] In a pneumatic tire comprising a tread portion extending in the circumferential direction of the tire and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged radially inward of these sidewall portions, with a carcass layer mounted between the pair of bead portions, tires of Comparative Examples 1 to 4 and Examples 1 to 10 were manufactured with the following settings: inclination angle of the carcass cord, presence or absence of a reinforcing rubber layer, ratio of the reinforcing rubber layer to the coat rubber E'r / E'c, ratio of the thickness of the reinforcing rubber layer to the thickness of the carcass layer, presence or absence of an inner liner, exposure ratio of the carcass layer, ratio of the reinforcing rubber layer to the side rubber layer tanδr / tanδs, distance d1, and distance d2 as shown in Table 1. The tire sizes were 300 / 650R18 for the front and 330 / 710R18 for the rear.

[0037] In Comparative Examples 1 to 4, the transponder is positioned between the carcass layer and the inner liner layer, while in Examples 1 to 10, the transponder is positioned between the carcass layer and the reinforcing rubber layer. In Comparative Examples 1 to 4 and Examples 1 to 10, the thickness of the carcass layer is 1.0 mm, and the storage modulus E'c(80°C) of the coating rubber covering the carcass cord is 3.0 MPa. In Comparative Examples 1 to 4 and Examples 1 to 10, the transponder is covered with a coating layer having a dielectric constant of 7, and the thickness of the coating layer is 1 mm.

[0038] In Table 1, "Distance d1" refers to the distance between the tip portion and the upper end of the bead filler. A negative value indicates that the tip portion is radially outward from the upper end of the bead filler, and a positive value indicates that the tip portion is radially inward from the upper end of the bead filler. "Distance d2" refers to the distance between the tip portion and the upper end of the bead core. "Carcass layer exposure ratio" indicates the ratio (×100%) of the surface area of ​​the exposed carcass layer to the surface area of ​​the inner surface of the tire.

[0039] These test tires were evaluated using the following test methods: tire evaluation (high-speed durability, load durability, and warm-up time) and transponder evaluation (communication performance). The results are shown in Table 1.

[0040] High-speed durability (tire): Each test tire was assembled onto a wheel with a standard rim, and a running test was performed using a drum tester under conditions of an air pressure of 180 kPa and a load of 7 kN. Specifically, the speed was increased by 10 km / h every 10 minutes starting from an initial speed of 200 km / h, and the running distance at the time a failure occurred in the tire was measured. The evaluation results are shown as an index with Comparative Example 1 set to 100. A larger index value means more excellent high-speed durability.

[0041] Load durability (tire): Each test tire was assembled onto a wheel with a standard rim, and a running test was performed using a drum tester under conditions of an air pressure of 180 kPa and a speed of 250 km / h. Specifically, the load was increased by 0.5 kN every 20 minutes starting from an initial load of 5 kN, and the running distance at the time a failure occurred in the tire was measured. The evaluation results are shown as an index with Comparative Example 1 set to 100. A larger index value means more excellent load durability.

[0042] Warm-up performance (tire): Each test tire was assembled onto a wheel with a standard rim, and under the condition of an air pressure of 180 kPa, actual vehicle running was performed on a 4.5 km per lap test course consisting of a dry road surface, and the lap time of the first lap was measured. The evaluation results are shown as an index using the reciprocal of the measured value, with Comparative Example 1 set to 100. A larger index value means more excellent warm-up performance.

[0043] Communication performance (transponder): For each test tire, communication work with the transponder was carried out using a reader / writer. Specifically, the maximum communicable distance was measured with the reader / writer set to an output of 250 mW and a carrier wave frequency of 860 MHz to 960 MHz. The evaluation results are shown as an index with Comparative Example 1 set to 100. A larger index value means more excellent communication performance.

[0044]

[0045] As can be seen from Table 1, the pneumatic tires of Examples 1 to 10 had the high-speed durability, load durability, and warm-up performance of the tires improved in a well-balanced manner compared to Comparative Example 1.

[0046] On the other hand, in Comparative Examples 2 to 4, the load-bearing durability of the tires deteriorated because they lacked a reinforcing rubber layer.

[0047] 1. Tread section 2. Sidewall section 3. Bead section 4. Carcass layer 5. Bead core 6. Bead filler 7. Belt layer 10. Reinforcement rubber layer 20. Transponder CL Tire centerline

Claims

1. A pneumatic tire comprising a tread portion extending in the circumferential direction of the tire and forming an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the radial side of the sidewall portions, wherein at least one carcass layer is mounted between the pair of bead portions, the carcass layer includes a plurality of carcass cords inclined at 5° or more with respect to the radial direction of the tire, these carcass cords are covered with a coating rubber, a transponder is positioned in contact with the carcass layer in the sidewall portion and inward from the carcass layer in the tire width direction, a reinforcing rubber layer is positioned inward from the transponder in the tire width direction, and the storage modulus of elasticity E'r (80°C) of the reinforcing rubber layer at 80°C is higher than the storage modulus of elasticity E'c (80°C) of the coating rubber covering the carcass cords.

2. The pneumatic tire according to claim 1, characterized in that the reinforcing rubber layer is arranged on the innermost surface of the tire and is partially arranged in the radial direction, and the carcass layer is exposed over 40% or more of the surface area of ​​the inner surface of the tire.

3. The pneumatic tire according to claim 1 or 2, characterized in that the tanδr (80°C) of the reinforcing rubber layer at 80°C is higher than the tanδs (80°C) of the side rubber layer disposed in the sidewall portion.

4. The pneumatic tire according to any one of claims 1 to 3, characterized in that the chip portion constituting the transponder is positioned radially inward from the upper end of the bead filler constituting the bead portion.

5. The pneumatic tire according to claim 4, characterized in that the tip portion is spaced 20 mm or more outward in the tire radial direction from the upper end of the bead core that constitutes the bead portion.

6. The pneumatic tire according to any one of claims 1 to 5, characterized in that an identification label is placed only on the outer surface of one of the pair of sidewall portions, and the transponder is placed on the one sidewall portion.

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