Patent Application
20230202245
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.
For pneumatic tires, embedding an RFID (radio frequency identification) tag (transponder) in a tire has been proposed (see, for example, Japan Unexamined Patent PublicationNo. 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 covering with the coating layer is insufficient, the communication performance of the transponder may degrade.
The present technology provides a pneumatic tire that can provide improved communication performance of a transponder.
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 sidewall portions extending in the tire circumferential direction, 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 shortest distance D from an outer edge of the coating layer to the transponder in a tire meridian cross-section is 0.3 mm or more.
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 shortest distance D from the outer edge of the coating layer to the transponder in the tire meridian cross-section is 0.3 mm or more. Thus, the transponder is sufficiently isolated from the peripheral rubbermember and wrapped with the coating layer having a low relative dielectric constant, allowing the communication performance of the transponder to be improved.
According to an embodiment of the present technology, the total thickness Gac of the coating layer preferably ranges from 1.5 mm to 3.5 mm. This can achieve the effect of improving the communication performance of the transponder and improve the durability of the transponder due to the protective effect based on the coating layer. Further, specifying the upper limit value of the total thickness Gac of the coating layer allows sufficient durability of the tire to be ensured.
Preferably, the transponder includes a substrate and antennas extending from both ends of the substrate and has 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. Furthermore, specifying the upper limit value of the distance L avoids occurrence of a local weight increase on the tire circumference and can satisfactorily maintain a tire balance.
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 of the carcass layer 4 in the tire width direction extending in the tire circumferential direction. 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 adjacent to the coating layer 23 (for example, the bead filler 6, the innerliner layer 9, the sidewall rubber layer 12, the rim cushion rubber layer 13, and the coating rubber of the carcass layer 4). Moreover, 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, and the shortest distance D from the outer edge of the coating layer 23 to the transponder 20 in the tire meridian cross-section is set to be 0.3 mm or more. Thus, the transponder 20 is sufficiently isolated from the peripheral rubber member and wrapped with the coating layer having a low relative dielectric constant, so that the communication performance of the transponder 20 can 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, by sufficiently ensuring the shortest distance D from the outer edge of the coating layer 23 to the transponder 20, the communication performance of the transponder 20 can be improved.
Here, when the shortest distance D from the outer edge of the coating layer 23 to the transponder 20 in the tire meridian cross-section is smaller than 0.3 mm, the effect of improving the communication performance of the transponder 20 cannot be obtained. In particular, the shortest distance D from the outer edge of the coating layer 23 to the transponder 20 in the tire meridian cross-section preferably ranges from 0.3 mm to 1.0 mm.
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 total thickness Gac of the coating layer 23 is less than 1.5 mm, the effect of improving the communication performance of the transponder 20 is reduced, and furthermore, the effect of improving the durability of the transponder 20 is reduced since the protective effect based on the coating layer 23 is reduced. On the other hand, when the total thickness Gac of the coating layer 23 is greater than 3.5 m, there is concern that tire durability will degrade. 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
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 effect of improving the communication performance of the transponder 20 will be reduced, the end of the antenna 22 in the tire circumferential direction may protrude from the coating layer 23 during travel, the antenna 22 may be damaged, and the communication performance after travel may degrade. On the other hand, even when the distance L is greater than 20 mm, the effect of further improving the communication performance of the transponder 20 cannot be obtained, and thus the tire balance can be degraded due to unnecessary weight increase.
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.
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 Example 1 and Examples 1 to 15 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 sidewall portions on the outer side in the tire width direction of the carcass layer extending in the tire circumferential direction, and the transponder was covered with a coating layer. The shortest distance D from the outer edge of the coating layer to the transponder in the tire meridian cross-section, the total thickness Gac of the coating layer, 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 relative dielectric constant 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 Example 1 and Examples 1 to 15, the relative dielectric constant of the coating layer is lower than that of the peripheral rubber member.
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. Communication Performance (transponder):
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.
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.
As can be seen from Tables 1 and 2, the pneumatic tires of Examples 1 to 15 were able to improve the communication performance of the transponder as compared to Comparative Example 1. In Comparative Example 1, since D=0.2, the communication performance of the transponder was not sufficient.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-093569 | May 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/017862 | 5/11/2021 | WO |
