Patent Application
20230080547
The present technology relates to a pneumatic tire in which a transponder covered with a covering layer is embedded and particularly relates to a pneumatic tire that can provide improved transponder durability while ensuring tire durability.
For pneumatic tires, embedment of an RFID (radio frequency identification) tag (transponder) in a tire has been proposed (see, for example, Japan Unexamined Patent Publication No. H07-137510). In the case where a transponder is embedded in the tire, the durability of the tire or the transponder cannot be sufficiently ensured if the physical properties of the covering layer for protecting the transponder are inadequate. For example, in a case where the glass transition temperature of the covering layer is too high, the durability of the tire at low temperature degrades, and the transponder is likely to be damaged due to tire deformation during travel at low temperature.
The present technology provides a pneumatic tire that can provide improved transponder durability while ensuring tire durability.
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 disposed on both sides of the tread portion; and a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions. The tire is embedded with a transponder covered with a covering layer. A glass transition temperature Tg of the covering layer is in a range of from −70° C. to −45° C.
In an embodiment of the present technology, the transponder is covered with the covering layer, and the glass transition temperature Tg of the covering layer is set in the range described above, and thus cracking in the covering layer during travel in a low-temperature environment can be prevented, while the protective effect of the covering layer on the transponder during travel at high temperature can be ensured. This can improve the durability of the transponder while ensuring the durability of the tire.
In the pneumatic tire according to an embodiment of the present technology, a storage modulus E′c (−20° C.) at −20° C. of the covering layer is preferably in a range of from 3 MPa to 17 MPa. This can effectively improve the durability of the transponder in a low-temperature environment while ensuring the durability of the tire.
The covering layer preferably has a relative dielectric constant of 7 or less. This can ensure the radio wave transmissivity of the transponder and improve the communication performance of the transponder.
Preferably, the transponder is embedded on an outer side in a tire width direction of the carcass layer, and a storage modulus E′c (−20° C.) at −20° C. of the covering layer and a storage modulus E′out (−20° C.) at −20° C. of a rubber member having a largest storage modulus at 20° C. of rubber members located on the outer side in the tire width direction of the transponder satisfy a relationship 0.1≤E′c (−20° C.)/E′out (−20° C.)≤1.5. This can effectively improve the durability of the transponder in a low-temperature environment while ensuring the durability of the tire.
The covering layer is preferably formed of a rubber or an elastomer and 20 phr or more of a white filler. This can lower the relative dielectric constant of the covering layer and effectively improve the communication performance of the transponder.
The white filler preferably includes from 20 phr to 55 phr of calcium carbonate. This can lower the relative dielectric constant of the covering layer and effectively improve the communication performance of the transponder.
A center of the transponder is preferably disposed 10 mm or more away in the tire circumferential direction from a splice portion of a tire component. This can effectively improve the durability of the tire.
The transponder is preferably disposed between a position 15 mm away from and on an outer side in the tire radial direction of an upper end of a bead core of the bead portion and a tire maximum width position. Accordingly, the transponder is disposed in a region where the stress amplitude during travel is small. This can effectively improve the durability of the transponder, and does not degrade the durability of the tire.
A distance between a cross-sectional center of the transponder and a tire surface is preferably 1 mm or more. This can effectively improve the durability of the tire as well as improve the scratch resistance of the tire.
A thickness of the covering layer preferably ranges from 0.5 mm to 3.0 mm. This can effectively improve the communication performance of the transponder without making the tire surface uneven.
Preferably, the transponder includes an IC (integrated circuit) substrate that stores data and an antenna that transmits and receives data, and the antenna has a helical shape. This allows the transponder to follow deformation of the tire during travel, improving the durability of the transponder.
In an embodiment of the present technology, the glass transition temperature Tg is a temperature at which a tan δ reaches a maximum value due to glass transition, the tan δ being measured while varying the temperature at a temperature elevation speed of 2° C./min. The tan δ is measured at a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of ±2% in a tensile deformation mode using a viscoelastic spectrometer in accordance with JIS (Japanese Industrial Standard)-K 6394. The storage modulus E′ is measured at a designated temperature, a frequency of 10 Hz, an initial strain of 10%, and a dynamic distortion of ±2% using a viscoelasticity spectrometer in a tensile deformation mode in accordance with JIS-K6394.
A configuration according to an embodiment 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 each folded back from a tire inner side to a tire outer side around the bead core 5, wrapping around the bead core 5 and the bead filler 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 a sidewall portion 2 side.
A tire inner surface includes an innerliner layer 9 disposed along the carcass layer 4. The tread portion 1 includes a cap tread rubber layer 11, the sidewall portion 2 includes a sidewall rubber layer 12, and the bead portion 3 includes a rim cushion rubber layer 13.
The pneumatic tire described above includes a transponder 20 embedded in a portion on an outer side in a tire width direction of the carcass layer 4. The transponder 20 extends along the tire circumferential direction. The transponder 20 may be inclined at an angle in a range of from −10° to 10° with respect to the tire circumferential direction. As illustrated in
The transponder 20 may be, for example, a radio frequency identification (RFID) tag. As illustrated in
The overall shape of the transponder 20 is not particularly limited, and can be, for example, a pillar-like shape or plate-like shape as illustrated in
In the pneumatic tire thus configured, a glass transition temperature Tg of the covering layer 23 covering the transponder 20 is set in a range of from −70° C. to −45° C. In particular, the glass transition temperature Tg of the covering layer 23 is preferably in the range of from −60° C. to −50° C.
In the pneumatic tire described above, the transponder 20 is covered with the covering layer 23, and the glass transition temperature Tg of the covering layer 23 is set in the range described above, and thus cracking in the covering layer 23 during travel in a low-temperature environment can be prevented, while the protective effect of the covering layer 23 on the transponder 20 during travel at high temperature can be ensured. This can improve the durability of the transponder 20 while ensuring the durability of the tire.
Here, in a case where the glass transition temperature Tg of the covering layer 23 is lower than the lower limit value, the heat resistance of the covering layer 23 degrades, the protective effect of the covering layer 23 on the transponder 20 during travel at high temperature degrades, and the transponder 20 is likely to be damaged. Conversely, in a case where the glass transition temperature Tg of the covering layer 23 is higher than the upper limit value, a crack is likely to be generated in the covering layer 23 during travel in a low-temperature environment, and thus the durability of the tire at low temperature degrades, and the transponder is likely to be damaged due to tire deformation during travel at low temperature.
Further, in the pneumatic tire described above, the transponder 20 is embedded on the outer side in the tire width direction of the carcass layer 4, and thus there is no tire component blocking radio waves during communication with the transponder 20, and the communication performance of the transponder 20 can be favorably ensured. In a case where the transponder 20 is embedded on the outer side in the tire width direction of 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.
In the pneumatic tire described above, a storage modulus E′c (−20° C.) at −20° C. of the covering layer 23 is preferably in a range of from 3 MPa to 17 MPa. By thus setting the physical properties of the covering layer 23, the durability of the transponder 20 can be effectively improved in a low-temperature environment.
Here, in a case where the storage modulus E′c (−20° C.) at −20° C. of the covering layer 23 is lower than the lower limit value, the rigidity of the covering layer 23 decreases, and the protective effect thereof degrades. Conversely, in a case where the storage modulus E′c (−20° C.) at −20° C. of the covering layer 23 is higher than the upper limit value, the rigidity of the covering layer 23 increases, the covering layer 23 becomes brittle, and the covering layer 23 becomes prone to breakage, and thus the transponder 20 is likely to be damaged.
The storage modulus E′c (−20° C.) at −20° C. of the covering layer 23 and the storage modulus E′c (0° C.) at 0° C. of the covering layer 23 preferably satisfy the relationship 1.0≤E′c (−20° C.)/E′c (0° C.)≤1.5. By thus setting the physical properties of the covering layer 23, the temperature dependency of the covering layer 23 decreases (the covering layer 23 is less likely to generate heat), and this prevents the covering layer 23 from softening even with a rise in tire temperature during high-speed travel, effectively improving the durability of the transponder 20.
In the pneumatic tire described above, of the rubber memb ers located on the outer side in the tire width direction of the transponder 20 (the sidewall rubber layer 12 and the rim cushion rubber layer 13 in
Furthermore, in a structure in which the transponder 20 is embedded on the outer side in the tire width direction of the carcass layer 4, the storage modulus E′ out (−20° C.) at −20° C. of the external member and the storage modulus E′c (−20° C.) at −20° C. of the covering layer 23 preferably satisfy the relationship 0.1≤E′c (−20° C.)/E′out (−20° C.)≤1.5. In particular, the relationship 0.15≤E′c (−20° C.)/E′out (−20° C.)≤1.30 is preferably satisfied. This can effectively improve the durability of the transponder 20 while ensuring the durability of the tire in a low-temperature environment.
Here, in a case where the value of E′c (−20° C.)/E′out (−20° C.) is smaller than the lower limit value, the rigidity of the covering layer 23 decreases, and the protective effect thereof degrades. Conversely, in a case where the value of E′c (−20° C.)/E′out (−20° C.) is larger than the upper limit value, the rigidity of the covering layer 23 increases, the covering layer 23 becomes brittle, and the covering layer 23 becomes prone to breakage, and thus the transponder 20 is likely to be damaged.
The composition of the covering layer 23 is preferably a rubber or an elastomer and 20 phr or more of a white filler. Such a composition of the covering layer 23 can lower the relative dielectric constant of the covering layer 23, compared to a composition containing carbon, and effectively improve the communication performance of the transponder 20. Note that “phr” means weight parts per 100 parts by weight of a rubber component (elastomer).
The white filler forming the covering layer 23 preferably includes from 20 phr to 55 phr of calcium carbonate. This can lower the relative dielectric constant of the covering layer 23 and effectively improve the communication performance of the transponder 20. However, too much calcium carbonate in the white filler makes the covering layer 23 brittle and lowers its strength, and this is not preferable. The covering layer 23 can optionally include 20 phr or less of a silica (white filler) or 5 phr or less of a carbon black in addition to calcium carbonate. An addition of a small amount of silica and carbon black can lower the relative dielectric constant of the covering layer 23 while ensuring the strength thereof.
The covering layer 23 preferably has a relative dielectric constant of 7 or less, and more preferably of from 2 to 5. By thus setting the relative dielectric constant of the covering layer 23 as appropriate, the radio wave transmissivity of the transponder 20 during emission of radio waves can be ensured, and the communication performance of the transponder 20 can be effectively improved. Note that the rubber forming the covering layer 23 has a relative dielectric constant of from 860 MHz to 960 MHz at ambient temperature. Here, the ambient temperature is 23±2° C. and 60%±5% RH (relative humidity) in accordance with the standard conditions of the JIS standard. The relative dielectric constant of the rubber is measured in accordance with an electrostatic capacitance method after a 24-hour treatment at 23° C. and 60% RH. 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, it is only required that the relative dielectric constant in the range of the allocated frequencies be specified as described above.
A thickness t of the covering layer 23 is preferably from 0.5 mm to 3.0 mm, and more preferably from 1.0 mm to 2.5 mm. Here, the thickness t of the covering layer 23 is a rubber thickness at a position including the transponder 20, and is, for example, a rubber thickness obtained by summing a thickness t1 and a thickness t2 on a straight line extending through the center of the transponder 20 and intersecting a tire surface (tire outer surface in
In the pneumatic tire described above, the transponder 20 is preferably disposed in a placement region in the tire radial direction between a position P1 15 mm away from and on the outer side in the tire radial direction of an upper end 5e (an end portion on the outer side in the tire radial direction) of the bead core 5 and a position P2 where the tire width is greatest. That is, the transponder 20 is preferably disposed in a region S1 illustrated in
As illustrated in
Note that while the embodiment of
As illustrated in
While the embodiment described above illustrates an example in which the end 4e of the turned up portion 4B of the carcass layer 4 is disposed at or near an upper end 6e of the bead filler 6, 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 to 2 and Examples 1 to 14 were manufactured. The tires were each a pneumatic tire having a tire size of 265/40ZR20 and including: a tread portion extending in a tire circumferential direction and having an annular shape; a pair of sidewall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions. A transponder was embedded on an outer side in the tire width direction of the carcass layer, the transponder being covered with a covering layer. The position in the tire radial direction of the transponder, the glass transition temperature Tg of the covering layer, the storage modulus E′c (−20° C.) of the covering layer, E′c (−20° C.)/E′out (−20° C.), the relative dielectric constant of the covering layer, and the thickness of the covering layer were set as in Table 1.
Comparative Examples 1 to 2 and Examples 1 to 14 used a transponder having a pillar-like shape, and set the distance in the tire circumferential direction from the center of the transponder to a splice portion of a tire component to 10 mm and the distance from the cross-sectional center of the transponder to a tire outer surface to 2 mm or more.
In Table 1, the position in the tire radial direction of the transponder corresponds to one of positions A to E illustrated in
The test tires were subjected to tire evaluation (durability) and transponder evaluation (communication performance and durability) in accordance with a test method described below, and the results are indicated together in Table 1.
With each test tire mounted on a wheel of a standard rim, a travel test was performed using a drum testing machine at a temperature of −20° C., an air pressure of 120 kPa, 65% of the maximum load, and a travel speed of 81 km/h, and the distance traveled at the time of a tire failure was measured. Evaluation results are expressed as index values with Comparative Example 1 being assigned an index value of 100. Larger index values indicate superior tire durability.
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 set at a power output of 250 mW and a carrier frequency of from 860 MHz to 960 MHz. Evaluation results are expressed as index values with Comparative Example 1 being assigned an index value of 100. Larger index values indicate superior communication performance.
After performing the tire durability test described above at low temperature, each test tire was checked for whether the transponder was communicable and whether the same was damaged, and the results are indicated in three levels: “Excellent” in a case where the transponder was communicable and not damaged; “Good” in a case where the transponder was communicable but damaged; and “Poor” in a case where the transponder was not communicable.
With each test tire assembled on a standard rim wheel, a high-speed durability test under the ECE (Economic Commission for Europe) R30 conditions was performed at a temperature of 38° C., an air pressure of 360 kPa, and 80% of the maximum load, and then each test tire was checked for whether the transponder was communicable and whether the same was damaged, and the results are indicated in three levels: “Excellent” in a case where the transponder was communicable and not damaged; “Good” in a case where the transponder was communicable but damaged; and “Poor” in a case where the transponder was not communicable.
As can be seen from Table 1 here, tire durability and transponder durability were improved in a well-balanced manner in the pneumatic tires of Examples 1 to 14, compared to Comparative Examples 1 to 2.
In Comparative Example 1, the glass transition temperature Tg of the covering layer was too low, and thus the durability of the transponder at high temperature was poor. In Comparative Example 2, the glass transition temperature Tg of the covering layer was too high, and thus the durability of the tire and the transponder at low temperature was poor.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-024292 | Feb 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/005237 | 2/12/2021 | WO |
