Patent Application
20230202244
The present technology relates to a pneumatic tire in which a transponder covered with a coating layer is embedded and particularly relates to a pneumatic tire that can provide improved communication performance of the transponder while ensuring durability of the tire.
For pneumatic tires, embedding an RFID (radio frequency identification) tag (transponder) in a tire has been proposed (see, for example, Japan Unexamined Patent Publication No. H07-137510 A). In embedding the transponder in the tire, coating the transponder with a coating layer and lowering the relative dielectric constant of the coating layer allows the communication performance of the transponder to be improved. However, when the coating layer is too thick, the durability of the tire may degrade.
The present technology provides a pneumatic tire that can provide improved communication performance of the transponder while ensuring durability of the tire.
A pneumatic tire according to an embodiment of the present technology includes a tread portion extending in a tire circumferential direction and having an annular shape, a pair of sidewall portions respectively disposed on both sides of the tread portion, and a pair of bead portions each disposed on an inner side of the pair of sidewall portions in a tire radial direction. In the pneumatic tire, a transponder is embedded in one of the pair of sidewall portions, the transponder is covered with a coating layer, a relative dielectric constant of the coating layer is lower than a relative dielectric constant of a peripheral rubber member adjacent to the coating layer, and a total thickness Gac of the coating layer and a maximum thickness Gar of the transponder satisfy a relationship 1.1≤Gac/Gar≤3.0.
According to an embodiment of the present technology, the transponder is covered with the coating layer, the relative dielectric constant of the coating layer is lower than the relative dielectric constant of the peripheral rubber member adjacent to the coating layer, and the total thickness Gac of the coating layer and the maximum thickness Gar of the transponder satisfy the above-mentioned relationship. Thus, the transponder is sufficiently isolated from the peripheral rubber member and wrapped with the coating layer having a low relative dielectric constant, allowing the communication performance of the transponder to be improved. Further, specifying the upper limit value of the total thickness Gac of the coating layer with respect to the maximum thickness Gar of the transponder can ensure sufficient durability of the tire.
According to an embodiment of the present technology, preferably, the transponder includes a substrate and antennas extending from both ends of the substrate, the transponder extends along the tire circumferential direction, and a distance L between an end of the antennas in the tire circumferential direction and an end of the coating layer in the tire circumferential direction ranges from 2 mm to 20 mm. This reliably covers the entire transponder with the coating layer, allowing a sufficient communication distance of the transponder to be ensured.
Preferably, the transponder includes a substrate and antennas extending from both ends of the substrate, and the antennas extend within a range of ±20° with respect to the tire circumferential direction. Restricting the inclination of the antennas that constitute the transponder in this way can ensure sufficient durability of the transponder.
Preferably, a center of the transponder in a thickness direction is disposed within a range of from 25% to 75% of the total thickness Gac of the coating layer from a surface on one side of the coating layer in a thickness direction. This reliably covers the transponder with the coating layer, allowing a sufficient communication distance of the transponder to be ensured.
Preferably, the coating layer is made of elastomer or rubber and has a relative dielectric constant of 7 or less. Specifying the relative dielectric constant of the coating layer in this way can effectively improve the communication performance of the transponder.
The center of the transponder is preferably disposed 10 mm or more spaced from a splice portion of a tire component in the tire circumferential direction. This can effectively improve the durability of the tire.
The transponder is preferably disposed between a position of 15 mm outer side in the tire radial direction from an upper end of a bead core of a bead portion and a tire maximum width position. This causes the transponder to be disposed in a region having a reduced stress amplitude during travel, thus allowing the durability of the transponder to be effectively improved and further preventing the communication performance of the transponder and the durability of the tire from being degraded.
Configurations of embodiments of the present technology will be described in detail below with reference to the accompanying drawings.
As illustrated in
At least one carcass layer 4 (one layer in
On the other hand, a plurality of belt layers 7 (two layers in
To improve high-speed durability, at least one belt cover layer 8 (two layers in
In the pneumatic tire described above, both ends 4e of the carcass layer 4 are folded back from the tire inner side to the tire outer side around the bead cores 5 and are disposed wrapping around the bead cores 5 and the bead fillers 6. The carcass layer 4 includes a body portion 4A corresponding to a portion extending from the tread portion 1 through each of the sidewall portions 2 to each of the bead portions 3 and a turned-up portion 4B corresponding to a portion turned up around the bead core 5 at each of the bead portions 3 and extending toward each sidewall portion 2 side.
Additionally, on a tire inner surface, an innerliner layer 9 is disposed along the carcass layer 4. Furthermore, a cap tread rubber layer 11 is disposed in the tread portion 1, a sidewall rubber layer 12 is disposed in the sidewall portion 2, and a rim cushion rubber layer 13 is disposed in the bead portion 3.
Additionally, in the pneumatic tire described above, the transponder 20 is embedded in a portion of the sidewall portion 2 located on the outer side in the tire width direction from the carcass layer 4. As illustrated in
As the transponder 20, for example, a radio frequency identification (RFID) tag can be used. As illustrated in
The overall shape of the transponder 20 is not particularly limited, and for example, a pillar- or plate-like shape can be used as illustrated in
In the pneumatic tire configured as described above, the relative dielectric constant of the coating layer 23 covering the transponder 20 is set to be lower than the relative dielectric constant of the peripheral rubber member (for example, the bead filler 6, the innerliner layer 9, the sidewall rubber layer 12, the rim cushion rubber layer 13, or the coating rubber of the carcass layer 4) adjacent to the coating layer 23, and as illustrated in
In the pneumatic tire described above, the transponder 20 is covered with the coating layer 23, the relative dielectric constant of the coating layer 23 is lower than the relative dielectric constant of the peripheral rubber member adjacent to the coating layer 23, the total thickness Gac of the coating layer 23 and the maximum thickness Gar of the transponder 20 satisfy the above-mentioned relationship, and thus the transponder 20 is sufficiently isolated from the peripheral rubber member and wrapped with the coating layer having a low relative dielectric constant, allowing the communication performance of the transponder 20 to be improved. That is, the radio wave wavelength shortens in the dielectric body, and the length of the antenna 22 of the transponder 20 is set to resonate with the shortened radio wave wavelength. Optimizing the length of the antenna 22 of the transponder 20 in this way significantly improves communication efficiency. To optimize the communication environment of the transponder 20, however, the transponder 20 should be sufficiently isolated from the peripheral rubber member adjacent to the coating layer 23. Therefore, satisfying the relationship 1.1≤Gac/Gar≤3.0 can improve the communication performance of the transponder 20. Further, specifying the upper limit value of the total thickness Gac of the coating layer 23 with respect to the maximum thickness Gar of the transponder 20 can ensure sufficient durability of the tire. This can provide the improved communication performance of the transponder 20 while ensuring the durability of the tire.
Here, when the value of Gac/Gar is smaller than 1.1, the effect of improving the communication performance of the transponder 20 is not obtained. Conversely, when the value is greater than 3.0, the durability of the tire decreases. In particular, the total thickness Gac of the coating layer 23 and the maximum thickness Gar of the transponder 20 desirably satisfy the relationship 1.5≤Gac/Gar≤2.5. The total thickness Gac of the coating layer 23 is the total thickness of the coating layer 23 at a position including the transponder 20. As illustrated in
Further, the pneumatic tire described above includes the transponder 20 embedded in the outer side in the tire width direction from the carcass layer 4, and thus there is no tire component blocking radio waves during communication with the transponder 20, allowing the communication performance of the transponder 20 to be satisfactorily ensured. In the present technology, the transponder 20 is disposed on the sidewall portion 2, but the position in the tire axial direction is not limited. In a case where the transponder 20 is embedded in the outer side in the tire width direction from the carcass layer 4, the transponder 20 can be disposed between the turned-up portion 4B of the carcass layer 4 and the rim cushion rubber layer 13, or between the carcass layer 4 and the sidewall rubber layer 12. In another configuration, the transponder 20 can be disposed between the turned-up portion 4B of the carcass layer 4 and the bead filler 6 or between the main body portion 4A of the carcass layer 4 and the bead filler 6. As illustrated in
In the pneumatic tire described above, as illustrated in
Here, when the absolute value of the inclination angle α of the transponder 20 with respect to the tire circumferential direction Tc is greater than 20°, the durability of the transponder 20 decreases with respect to repetitive tire deformation during travel. Further, when the distance L between the end of the antenna 22 in the tire circumferential direction and the end of the coating layer 23 in the tire circumferential direction is smaller than 2 mm, the end of the antenna 22 in the tire circumferential direction protrudes out of the coating layer 23, the antenna 22 may be damaged during travel, and the communication distance after travel may be shortened. On the other hand, when the distance L is greater than 20 mm, a local weight increase occurs on the tire circumference, causing degradation in a tire balance.
In the pneumatic tire described above, as illustrated in
Here, when the absolute value of the inclination angle β of the transponder 20 with respect to the tire circumferential direction Tc is larger than 20°, stress concentrates on the base end portion of the antenna 22 due to repetitive tire deformation during travel, decreasing the durability of the transponder 20. The antenna 22 is not necessarily straight, and the inclination angle β of the antenna 22 is an angle between a straight line connecting the base end with the tip end of the antenna 22 and the tire circumferential direction Tc.
In the pneumatic tire described above, as illustrated in
As the composition of the coating layer 23, the coating layer 23 is preferably made of rubber or elastomer and 20 phr or more of white filler. The relative dielectric constant can be set relatively lower for the coating layer 23 configured as described above than for the coating layer 23 containing carbon, allowing the communication performance of the transponder 20 to be effectively improved. Note that “phr” as used herein means parts by weight per 100 parts by weight of the rubber component (elastomer).
The white filler constituting the coating layer 23 preferably includes from 20 phr to 55 phr of calcium carbonate. This enables a relatively low relative dielectric constant to be set for the coating layer 23, allowing the communication performance of the transponder 20 to be effectively improved. However, the white filler with an excessive amount of calcium carbonate contained is brittle, and the strength of the coating layer 23 decreases. This is not preferable. Additionally, the coating layer 23 can optionally contain, in addition to calcium carbonate, 20 phr or less of silica (white filler) or 5 phr or less of carbon black. In a case where a small amount of silica or carbon black is used with the coating layer 23, the relative dielectric constant of the coating layer 23 can be reduced while ensuring the strength of the coating layer 23.
In addition, the coating layer 23 preferably has a relative dielectric constant of 7 or less and more preferably from 2 to 5. By properly setting the relative dielectric constant of the coating layer 23 as described above, radio wave transmittivity can be ensured during emission of a radio wave by the transponder 20, effectively improving the communication performance of the transponder 20. Note that the rubber constituting the coating layer 23 has a relative dielectric constant of from 860 MHz to 960 MHz at ambient temperature. In this regard, the ambient temperature is 23±2° C. and 60%±5% RH (relative humidity) in accordance with the standard conditions of the JIS (Japanese Industrial Standard) standard. The relative dielectric constant of the rubber is measured by the capacitance method after the rubber is treated at 23° C. and 60% RH for 24 hours. The range from 860 MHz to 960 MHz described above corresponds to currently allocated frequencies of the RFID in a UHF (ultra-high frequency) band, but in a case where the allocated frequencies are changed, the relative dielectric constant in the range of the allocated frequencies is specified as described above.
In the pneumatic tire described above, as illustrated in
As illustrated in
More specifically, when the transponder 20 is disposed between the carcass layer 4 and the innerliner layer 9, the splice portion of the carcass layer 4 and/or the splice portion of the innerliner layer 9 is preferably disposed spaced from the transponder 20. When the transponder 20 is disposed between the carcass layer 4 and one of the sidewall rubber layer 12 and the rim cushion rubber layer 13 and the carcass layer 4 has a low turn-up structure, the splice portion of the bead filler 6 and/or the splice portion of one of the sidewall rubber layer 12 and the rim cushion rubber layer 13 is preferably disposed spaced from the transponder 20 located on the inner side in the tire radial direction from the vertex of the bead filler 6, and the splice portion of the carcass layer 4 and/or the splice portion of one of the sidewall rubber layer 12 and the rim cushion rubber layer 13 is preferably disposed spaced from the transponder 20 located in the flex zone on the outer side in the tire radial direction from the vertex of the bead filler 6. When the transponder 20 is disposed between the carcass layer 4 and one of the sidewall rubber layer 12 and the rim cushion rubber layer 13, and the carcass layer 4 has a high turn-up structure, the splice portion of the carcass layer 4 and/or the splice portion of one of the sidewall rubber layer 12 and the rim cushion rubber layer 13 is preferably disposed spaced from the transponder 20.
Note that in the embodiment of
In the example illustrated in the embodiment described above, the end 4e of the turned-up portion 4B of the carcass layer 4 is disposed close to the upper end 6e of the bead filler 6. However, no such limitation is intended, and the end 4e of the turned-up portion 4B of the carcass layer 4 can be disposed at any height.
Tires according to Comparative Examples 1 and 2 and Examples 1 to 20 were manufactured. The tires were each a pneumatic tire having a tire size of 235/60R18, and including a tread portion extending in the tire circumferential direction and having an annular shape; a pair of sidewall portions respectively disposed on both sides of the tread portion and a pair of bead portions each disposed on the inner side of the pair of sidewall portions in the tire radial direction. In the pneumatic tire, a columnar transponder was embedded in one of the pair of sidewall portions on the outer side in the tire width direction of the carcass layer, and the transponder was covered with a coating layer. The ratio Gac/Gar between the total thickness Gac of the coating layer and the maximum thickness Gar of the transponder, the distance L between the end of the antenna in the tire circumferential direction and the end of the coating layer in the tire circumferential direction, the angle β of the antenna with respect to the tire circumferential direction, the position of the transponder center within the coating layer, the relative dielectric constant of the coating layer, the material of the coating layer, the distance in the tire circumferential direction from the transponder center to the splice portion of the tire component, and the position of the transponder in the tire radial direction were set as shown in Tables 1 and 2.
In Comparative Examples 1 and 2 and Examples 1 to 20, the relative dielectric constant of the coating layer is lower than that of the peripheral rubber member. The position of the transponder center within the coating layer is expressed the ratio of the distance from the surface of the coating layer on the carcass layer side to the transponder center to the total thickness Gac of the coating layer.
In Tables 1 and 2, the position of the transponder in the tire radial direction corresponds to each of the positions A to E illustrated in
Tire evaluation (durability) and transponder evaluation (communication performance and durability) were conducted on the test tires using a test method described below, and the results are indicated in Tables 1 and 2.
Each of the test tires was mounted on a wheel of a standard rim, and a traveling test was performed by using a drum testing machine at an air pressure of 120 kPa, a maximum load of 102%, and a traveling speed of 81 km/h, and the traveling distance at the time of a failure in the tire was measured. The evaluation results are expressed as three levels: “Excellent” indicates that the traveling distance reached 6480 km, “Good” indicates that the traveling distance was 4050 km to 6480 km, and “Poor” indicates that the traveling distance was less than 4050 km. Furthermore, after the end of traveling, each test tire was checked for the availability of communication of the transponder and for damage to the transponder. Results are expressed as two levels: “Good” indicates that communication was enabled and no damage was found (as new as new products), and “Fair” indicates that communication was enabled but the communication distance has decreased due to damage to the antenna.
For each test tire, a communication operation with the transponder was performed using a reader/writer. Specifically, the maximum communication distance was measured with the reader/writer at a power output of 250 mW and a carrier frequency of from 860 MHz to 960 MHz. The evaluation results are expressed as three levels: “Excellent” indicates that the communication distance was 1000 mm or more, “Good” indicates that the communication distance was 500 mm to 1000 mm, and “Fair” indicates that the communication distance was less than 500 mm.
As can be seen from Tables 1 and 2, the pneumatic tires of Examples 1 to 20 were able to improve the communication performance of the transponder while ensuring the durability of the tire as compared to Comparative Example 1. In Comparative Example 1, since Gac/Gar=1.0, the communication performance of the transponder was not sufficient. In Comparative Example 2, since Gac/Gar=3.1, the durability of the tire was not sufficient.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-093557 | May 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/017861 | 5/11/2021 | WO |
