Patent Application
20240278516
The present technology relates to a method for producing a pneumatic tire for embedding a transponder coated with a coating layer and particularly relates to a method for producing a pneumatic tire that can suppress vulcanization defects of a 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). When the transponder is coated with a coating layer and embedded in a tire, a gap is generated between the coating layer and a rubber member around the coating layer to cause vulcanization defects.
The present technology provides a method for producing a pneumatic tire that can suppress vulcanization defects of a tire.
A method for producing a pneumatic tire according to an embodiment of the present technology is a method for producing a pneumatic tire for embedding a transponder including: causing a coating layer coating the transponder to have, in a thickness direction thereof, a top surface layer located on a top surface side of the transponder and a back surface layer located on a back surface side of the transponder: forming a step at least at an end portion on one side of both end portions of the coating layer in a width direction such that positions of end portions of the top surface layer and the back surface layer do not coincide with each other: embedding the transponder coated with the coating layer having the step in an unvulcanized tire; and vulcanizing the unvulcanized tire.
In an embodiment of the present technology, causing the coating layer coating the transponder to have, in the thickness direction thereof, the top surface layer located on the top surface side of the transponder and the back surface layer located on the back surface side of the transponder, forming the step at least at the end portion on the one side of the both end portions of the coating layer in the width direction such that the positions of end portions of the top surface layer and the back surface layer do not coincide with each other, embedding the transponder coated with the coating layer having the step in an unvulcanized tire, and vulcanizing the unvulcanized tire allows a gap generated between the coating layer and a rubber member disposed adjacent to the coating layer to be reduced by the step. This can suppress vulcanization defects of the tire around the transponder.
In the method for producing a pneumatic tire according to an embodiment of the present technology, the step is preferably formed by shifting the positions of end portions of the top surface layer and the back surface layer at least at the end portion on the one side of both end portions of the coating layer in the width direction in sandwiching the transponder between the top surface layer and the back surface layer. This can effectively suppress vulcanization defects of the tire.
The step is preferably formed at each of both end portions in the width direction of the coating layer. This can effectively suppress vulcanization defects of the tire.
A width of the step preferably ranges from 1.5 mm to 5.0 mm. This can effectively suppress vulcanization defects of the tire and improve tire durability.
A thickness of at least one of the top surface layer or the back surface layer preferably ranges from 0.5 mm to 2.5 mm. This can effectively suppress vulcanization defects of the tire.
A relative dielectric constant of the coating layer is preferably lower than a relative dielectric constant of a rubber member disposed adjacent to the coating layer, and a total thickness Gac of the coating layer and a maximum thickness Gar of the transponder preferably satisfy a relationship 1.1≤Gac/Gar ≤3.0. This sufficiently separates the transponder from the adjacent rubber member and wraps the transponder with the coating layer having a low relative dielectric constant, thus allowing 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.
The coating layer is preferably made of elastomer or rubber and preferably has a relative dielectric constant of 7 or less. This enables the transponder to have a radio wave transmitting property, effectively improving the communication performance of the transponder.
Mooney viscosity of the coating layer is preferably lower than Mooney viscosity of a rubber member disposed adjacent to the coating layer. This makes the rubber flow of the coating layer during vulcanization satisfactory and causes vulcanization defects to be less likely to occur even when a gap is generated between the coating layer and the adjacent rubber member.
A minimum value MLc on a vulcanization curve obtained from torque detection by using a rheometer in the coating layer is preferably lower than a minimum value MLt on a vulcanization curve obtained from torque detection by using the rheometer in a rubber member disposed adjacent to the coating layer. This makes the rubber flow of the coating layer during vulcanization satisfactory and causes a gap to be less likely to be generated between the coating layer and the adjacent rubber member, thus allowing vulcanization defects of the tire to be effectively suppressed.
The transponder is preferably disposed such that a longitudinal direction of the transponder is within a range of ±10° with respect to a circumferential direction of a forming drum. This can effectively improve tire durability.
The center of the transponder is preferably disposed 10 mm or more away from a splice portion of a tire component in the tire circumferential direction. This can effectively improve tire durability.
The transponder is preferably disposed between a position 15 mm on an outer side in a tire radial direction from an upper end of a bead core of a bead portion and a position 5 mm on an inner side in the tire radial direction from an end of a belt layer. This causes metal interference to be less likely to occur and can have the communication performance of the transponder.
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.
An innerliner layer 9 is disposed along the carcass layer 4 on a tire inner surface. 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.
In the pneumatic tire described above, the transponder 20 is embedded between the carcass layer 4 and the innerliner layer 9. 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 limited to particular shapes and can use a pillar- or plate-like shape as illustrated in, for example,
In an example illustrated in the embodiment of
Next, a method for producing a pneumatic tire according to an embodiment of the present technology will be described. In producing the pneumatic tire as described above, the pneumatic tire is produced by placing the innerliner layer 9 on a forming drum, layering thereon the transponder 20 coated with the coating layer 23 and tire components including the carcass layer 4, the bead core 5, the bead filler 6, the belt layer 7, and the belt cover layer 8, bonding the cap tread rubber layer 11, the sidewall rubber layer 12, and the rim cushion rubber layer 13 to form an unvulcanized tire, and vulcanizing the unvulcanized tire.
In such a producing process, a forming step of forming a step 24 in the coating layer 23 coating both the top and back surfaces of the transponder 20 is performed in advance. In the forming process, as illustrated in
For example, when the coating layer 23 having the cross-sectional shape illustrated in
In the method for producing a pneumatic tire described above, causing the coating layer 23 coating the transponder 20 to have, in the thickness direction thereof, the top surface layer 23x located on the top surface side of the transponder 20 and the back surface layer 23y located on the back surface side of the transponder 20, forming the step 24 at least at an end portion on one side of the both end portions 23a and 23b of the coating layer 23 in the width direction such that the positions of end portions of the top surface layer 23x and the back surface layer 23y do not coincide with each other, embedding the transponder 20 coated with the coating layer 23 having the step 24 in the unvulcanized tire, and vulcanizing the unvulcanized tire allows a gap generated between the coating layer 23 and a rubber member (for example, the innerliner layer 9) disposed adjacent to the coating layer 23 to be reduced by the step 24. This can suppress vulcanization defects of the tire around the transponder 20.
On the other hand, using a transponder coated with a coating layer having no step causes a level difference to be locally formed on the circumference of the unvulcanized tire, generates a gap around the transponder between the coating layer and a rubber member disposed adjacent to the coating layer, and causes vulcanization defects of the tire to be likely to occur. In this case, the transponder disposed on an outer side in the tire width direction from the carcass layer causes air to be entrained and cracking to be likely to occur around the transponder. On the other hand, the transponder disposed on an inner side in the tire width direction from the carcass layer causes a projection toward an inner side in the tire radial direction and thus causes release agent to be entrained and cracking to be likely to occur around the transponder.
In the method for producing a pneumatic tire described above, the step 24 is preferably formed by shifting the positions of end portions of the top surface layer 23x and the back surface layer 23y at least at the end portion on the one side of both end portions 23a and 23b in the width direction of the coating layer 23 in sandwiching the transponder 20 between the top surface layer 23x and the back surface layer 23y. For example, using two extruders and disposing the band-like top surface layer 23x and the band-like back surface layer 23y extruded from the respective extruders on the top and back surfaces of the transponder 20 can cover the entire transponder 20. In this case, the widths of the top surface layer 23x and the back surface layer 23y extruded from the respective extruders are different from each other, and the positions of end portions of the top surface layer 23x and the back surface layer 23y are disposed to be shifted in the width direction. This can form the step 24 at least at an end portion on one side of both end portions 23a and 23b of the coating layer 23 in the width direction. Coating the transponder 20 in this manner allows vulcanization defects of the tire to be effectively suppressed.
In particular, the step 24 is preferably formed at both end portions in the width direction of the coating layer 23. Providing the step 24 on the coating layer 23 in this manner can further reduce a gap between the coating layer 23 and a rubber member disposed adjacent to the coating layer 23, thus allowing vulcanization defects of the tire to be effectively suppressed.
In disposing the transponder 20 coated with the coating layer 23 having the step 24 on a forming drum D, the transponder 20 is preferably disposed such that the longitudinal direction of the transponder 20 is in the range of ±10° with respect to the circumferential direction of the forming drum D as illustrated in
In the method for producing a pneumatic tire described above. Mooney viscosity of the coating layer 23 is preferably lower than Mooney viscosity of a rubber member disposed adjacent to the coating layer 23. Examples of such an adjacent rubber member may include the carcass layer 4, the bead filler 6, the innerliner layer 9, the sidewall rubber layer 12, and the rim cushion rubber layer 13. A ratio of Mooney viscosity [ML (1+4) 100° C.] of the coating layer 23 to Mooney viscosity [ML (1+4) 100° C.] of the adjacent rubber member preferably ranges from 0.3 to 0.9, more preferably from 0.5 to 0.8, and most preferably from 0.5 to 0.7. In an embodiment of the present technology, the Mooney viscosity [ML (1+4) 100° C.] is measured in accordance with JIS (Japanese Industrial Standard) K6300-1, by a Mooney viscometer using an L-shaped rotor, and under conditions of preheating time of 1 minute, rotation time of rotor of 4 minutes, and test temperature of 100° C. Appropriately setting the Mooney viscosity of the coating layer 23 with respect to the adjacent rubber member in this manner makes the rubber flow of the coating layer 23 during vulcanization satisfactory and causes vulcanization defects to be less likely to occur even when a gap is generated between the coating layer 23 and the adjacent rubber member.
Here, the ratio of the Mooney viscosity of the coating layer 23 to the Mooney viscosity of the adjacent rubber member of smaller than 0.3 makes the rubber flow of the coating layer 23 during vulcanization excessively good, may expose the transponder 20, and degrades communication performance of the transponder 20 when the transponder 20 comes into contact with the adjacent rubber member. On the other hand, the ratio of the Mooney viscosity of the coating layer 23 to the Mooney viscosity of the adjacent rubber member of larger than 0.9 degrades the rubber flow of the coating layer 23 during vulcanization, causes a gap to be likely to be generated between the coating layer 23 and the adjacent rubber member, and thus causes vulcanization defects of the tire to be likely to occur.
Additionally, the minimum value MLc on a vulcanization curve obtained from torque detection by using a rheometer in the coating layer 23 is preferably smaller than the minimum value MLt on a vulcanization curve obtained from torque detection by using the rheometer in the rubber member disposed adjacent to the coating layer 23. It is more preferable that the minimum value MLc of the coating layer 23 and the minimum value MLt of the adjacent rubber member satisfy the relationship 0.2≤MLc/MLt<1.0. Appropriately setting the viscosity of the coating layer 23 in this manner makes the rubber flow of the coating layer 23 during vulcanization satisfactory and causes a gap to be less likely to be generated between the coating layer 23 and the adjacent rubber member, thus allowing vulcanization defects of the tire to be effectively suppressed. In an embodiment the present technology, the vulcanization curve obtained from torque detection by using the rheometer is in accordance with JIS K6300-2 and is obtained by measuring, at a temperature of 170° C. a vulcanization curve having the torque to be obtained on the vertical axis and the vulcanization time on the horizontal axis. The minimum value of torque is ML in the vulcanization curve.
Here, the minimum value MLc of the coating layer 23 and the minimum value MLt of the adjacent rubber member of lower than the lower limit of the relational expression described above makes the rubber flow of the coating 35 layer 23 during vulcanization excessively good, may expose the transponder 20, and degrades communication performance of the transponder 20 when the transponder 20 comes into contact with the adjacent rubber member. On the other hand, the minimum value MLc of the coating layer 23 and the minimum value MLt of the adjacent rubber member exceeding the upper limit of the relational expression described above degrades the rubber flow of the coating layer 23 during vulcanization, causes a gap to be likely to be generated between the coating layer 23 and the adjacent rubber member, and thus causes vulcanization defects of the tire to be likely to occur.
In the method for producing a pneumatic tire described above, a width w of the step 24 (see
Here, the width w of the step smaller than 1.5 mm cannot sufficiently obtain the effect of improving vulcanization defects of the tire, degrading tire durability due to the vulcanization defects of the tire. The width w of the step larger than 5.0 mm increases the gap between the coating layer 23 and the adjacent rubber member, thus failing to sufficiently obtain the effect of improving vulcanization defects of the tire and degrading tire durability due to the vulcanization defects of the tire.
A thicknesses t (see
Here, the thickness t of the coating layer 23 smaller than 0.5 mm degrades the communication performance of the transponder 20 but allows vulcanization defects of the tire around the transponder 20 to be suppressed. The thickness t of the coating layer 23 greater than 2.5 mm improves the communication performance of the transponder 20 but causes vulcanization defects of the tire to be likely to occur. Setting the thickness t of the coating layer 23 within the range described above can effectively suppress vulcanization defects of the tire.
In the method for producing a pneumatic tire described above, the relative dielectric constant of the coating layer 23 coating the transponder 20 is set to be lower than the relative dielectric constant of the rubber member (for example, the innerliner layer 9, the bead filler 6, the sidewall rubber layer 12, the rim cushion rubber layer 13, or the coating rubber of the carcass layer 4) disposed adjacent to the coating layer 23, and a total thickness Gac of the coating layer 23 and the maximum thickness Gar of the transponder 20 preferably satisfy the relationship 1.1≤Gac/Gar≤3.0. 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, and is, for example, as illustrated in
Setting the relative dielectric constant of the coating layer 23 in this manner and allowing the total thickness Gac of the coating layer 23 and the maximum thickness Gar of the transponder 20 to satisfy the relationship described above causes the transponder 20 to be sufficiently isolated from the adjacent rubber member and to be wrapped with the coating layer 23 having a low relative dielectric constant, thus allowing the communication performance of the transponder 20 to be improved. In other words, the wavelength of the radio wave of a communication device is λ, the relative dielectric constant of the coating layer 23 covering the transponder 20 is εr, the wavelength of the radio wave passing through the coating layer 23 is λ/√εr, and thus the length of the antenna 22 of the transponder 20 is set so as to resonate with the wavelength λ/√εr. Optimizing the length of the antenna 22 of the transponder 20 in this way significantly improves communication efficiency. However, the transponder 20 needs to be sufficiently isolated from the adjacent rubber member adjacent to the coating layer 23 in order to optimize the communication environment of the transponder 20. 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 aforementioned ratio is excessively small (the total thickness Gac of the coating layer 23 is excessively thin), the transponder 20 comes into contact with the adjacent rubber member, resonant frequency is shifted, and the communication performance of the transponder 20 is degraded. On the other hand, when the aforementioned ratio is excessively large (the total thickness Gac of the coating layer 23 is excessively thick), tire durability tends to be degraded.
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. The “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. 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.
The coating layer 23 preferably has a relative dielectric constant of 7 or less and more preferably from 2 to 5. Appropriately setting the relative dielectric constant of the coating layer 23 in this manner allows radio wave transmittivity when the transponder 20 emits a radio wave to be ensured, effectively improving the communication performance of the transponder 20. The rubber constituting the coating 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 by the capacitance method after the rubber is treated at 23° C. and 60% RH for 24 hours. The range of 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 may be specified as described above.
In the method for producing a pneumatic tired described above, as a placement region in the tire radial direction, the transponder 20 is preferably disposed between a position P1 15 mm on an outer side in the tire radial direction from an upper end 5e of the bead core 5 (an end portion on the outer side in the tire radial direction) and a position P2 5 mm on an inner side in the tire radial direction from an end 7e of the belt layer 7. In other words, the transponder 20 is preferably disposed in a region S1 illustrated in
As illustrated in
In an example illustrated in the embodiment of
As illustrated in
In an example illustrated in the embodiment of
In an example illustrated in the embodiment described above, the step 24 is formed only at the end portion on one side of the coating layer 23 in the width direction, but no such limitation is intended. In forming the step 24, as illustrated in
In forming the step 24, as illustrated in
In a method for producing a pneumatic tire having a tire size of 245/35R21 in which a transponder is embedded, tires of Conventional Example and Examples 1 to 13 were produced. For each of the tires, a transponder was coated with a coating layer, the transponder coated with the coating layer was embedded in an unvulcanized tire, and the unvulcanized tire was vulcanized. The presence or absence of a step of the coating layer, the width of the step of the coating layer, Gac/Gar, the material of the coating layer, the relative dielectric constant of the coating layer, the position of the transponder in the tire circumferential direction, and the position of the transponder in the tire radial direction were set as shown in Table 1.
In Conventional Example and Examples 1 to 13, the transponder is embedded between the carcass layer and the innerliner layer, and the relative dielectric constant of the coating layer coating the transponder is set to be lower than that of a rubber member (the innerliner layer and coating rubber of the carcass layer) disposed adjacent to the coating layer.
In Table 1, the position of the transponder in the tire circumferential direction indicates the distance (mm) measured from the center of the transponder to the splice portion of the tire component in the tire circumferential direction. The position of the transponder in the tire radial direction corresponds to each of the positions A to C illustrated in
Tire evaluations (vulcanization defects and durability) and transponder evaluation (communication performance) were conducted on these test tires in accordance with the following test methods, and the results are shown in Table 1.
Two hundred tires were produced for each test tire, and the occurrence of vulcanization defects around the transponder was visually confirmed to calculate the rate of occurrence of vulcanization defects. The evaluation results are expressed in three levels: “Excellent” indicates no vulcanization defects, “Good” indicates the rate of occurrence of vulcanization defects of less than 3%, and “Fair” indicates the rate of occurrence of vulcanization defects of 3% or more.
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, 102% of the maximum load, and a traveling speed of 81 km/h. After the test was performed, the traveling distance at the time of occurrence of a failure in the tire was measured. Evaluation results are expressed in three levels: “Excellent” indicates that the traveling distance reached 6480 km, “Good” indicates that the traveling distance was 4050 km or more and less than 6480 km, and “Fair” indicates that the traveling distance was less than 4050 km.
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 in three levels: “Excellent” indicates that the communication distance is 1000 mm or more, “Good” indicates that the communication distance is 500 5 mm or more and less than 1000 mm, and “Fair” indicates that the communication distance is less than 500 mm.
As can be seen from Table 1, the pneumatic tires of Examples 1 to 13 5 were able to suppress the occurrence of vulcanization defects of the tire as compared with the Conventional Example. Additionally, the pneumatic tires of Examples 1 to 7 and 9 to 13 were able to provide improved durability of the tire as compared with Conventional Example, and the pneumatic tires of Examples 5 to 13 were able to provide improved communication performance of the transponder as compared with Conventional Example.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-103073 | Jun 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/023600 | 6/13/2022 | WO |
