JP4136587B2 - Pneumatic tire - Google Patents

Description

表１の結果が示すように、本発明によると、乗り心地性やロードノイズなどの居住性の改善効果と操縦安定性の改善効果とを両立させることができる。これに対し、トッピングゴムの硬度の大小関係が一部逆転した比較例２では、乗り心地性やロードノイズなどの居住性と操縦安定性とが何れも悪化した。
【図面の簡単な説明】
【図１】本発明の空気入りタイヤの一例を示す部分断面図
【図２】本発明の空気入りタイヤの他の例のカーカス層を模式的に示す側面図
【符号の説明】
１ａ ビード
６ ベルト層
６ａ 下層（最内周側のベルト層）
１０ カーカス層
１１ カーカス層の本体部
１２ カーカス層の巻き返し部
Ｃ１ 最も硬度の高いトッピングゴムで被覆されたカーカス層
Ｃ２ ２番目に硬度の高いトッピングゴムで被覆されたカーカス層
Ｃ３ ３番目に硬度の高いトッピングゴムで被覆されたカーカス層
Ｐ１ ベルト層の外側端
Ｐ２ タイヤ最大幅位置
Ｐ３ ビード下のタイヤ内周端[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire including a pair of annular beads, a carcass layer whose ends are rolled back by the bead, and a plurality of belt layers that reinforce the carcass layer positioned below the tread with a tagging effect.
[0002]
[Prior art]
Currently, radial tires, which are the mainstream of pneumatic tires, reinforce a space between a pair of annular beads, and a carcass layer in which a plurality of cords are arranged in the tire radial direction (meridian direction), and a carcass located below the tread. A structure including a plurality of belt layers in which the layers are reinforced by the hoop effect and the cords are inclined with respect to the tire circumferential direction is common. Further, both end portions of the carcass layer are wound back to the outside by beads, and the cords of the wound portions are usually arranged in the tire radial direction.
[0003]
Various types of pneumatic tires are known in which a reinforcing layer reinforced with long fibers or short fibers is provided in addition to the carcass layer around the bead for the purpose of improving the handling stability by increasing the rigidity of the bead portion. ing. There is also known a pneumatic tire in which the rigidity of the bead portion is increased by inclining the cord of the winding portion of the carcass layer from the tire radial direction without providing such a reinforcing layer (for example, Patent Document 1). And Patent Document 2).
[0004]
On the other hand, when the vehicle travels on a relatively rough road surface, noise called road noise is generated in the passenger compartment. This road noise is one of the noises related to tires, and the tires vibrate due to the road surface unevenness being input to the tires, and this vibration is transmitted along the propagation path such as the axle, suspension, and vehicle body, and finally Cause noise in the passenger compartment. Of this vehicle interior noise, low-frequency road noise generated in the vicinity of 125 Hz is close to the primary resonance frequency of the tire and coincides with that frequency, resulting in a road noise peak. Therefore, noise reduction is required.
[0005]
By the way, when the carcass layer is formed, a carcass ply in which a top fabric is covered with an interdigital fabric in which a plurality of cords are arranged in parallel is generally used. As for the topping rubber, the same type of rubber is used on the entire surface of the carcass ply, and changing the type of rubber in a part of the area has not been usually performed. However, in a pneumatic tire that omits the inner liner, a pneumatic tire is known in which the amount of butyl rubber is changed in a part of the carcass ply in order to achieve both air impermeability and drum durability. (See Patent Document 3).
[0006]
[Patent Document 1]
JP-A-11-170807 (first page, FIG. 4)
[Patent Document 2]
JP-A-8-324213 (first page, FIG. 1)
[Patent Document 3]
JP-A-9-58208 (first page, FIG. 2)
[0007]
[Problems to be solved by the invention]
However, in the carcass ply coated with one kind of topping rubber as described above, there is a problem that, when the hardness of the topping rubber is increased, the driving stability is increased, but the ride comfort and road noise are deteriorated. Conversely, when the hardness of the topping rubber is reduced, the ride comfort and road noise are improved, but the steering stability is lowered, that is, the steering stability and the habitability are contradictory.
[0008]
Accordingly, an object of the present invention is to provide a pneumatic tire that can achieve both an improvement effect of comfortability such as ride comfort and road noise and an improvement effect of steering stability.
[0009]
[Means for Solving the Problems]
The above object can be achieved by the present invention as described below.
That is, the pneumatic tire of the present invention includes a pair of annular beads, a carcass layer whose ends are rolled back by the beads, and a plurality of belt layers that reinforce the carcass layer located below the tread by a tagging effect. In the pneumatic tire provided, the carcass layer is coated with a topping rubber of two or more kinds of hardness, and the carcass layer in a region between the outer end of the innermost belt layer and the tire maximum width position Is based on the average value of hardness in the region (Σ area ratio × hardness), the average value of which has a region covered with 60-80 ° topping rubber with the highest hardness of JISA , and other regions Is characterized by being covered with a topping rubber having a JISA hardness of 40 to 70 ° .
[0010]
In the above, the carcass layer is coated with a topping rubber having three or more kinds of hardness, and the portion of the carcass layer wound back by the bead has a second highest hardness of 52 to 70 ° in JISA hardness. It is preferable that the other region is covered with a topping rubber having a JIS hardness of 40 to 67 ° .
[0011]
The carcass layer is covered with a cord with a topping rubber having four or more kinds of hardness, and the carcass layer in the region between the tire maximum width position and the tire inner peripheral edge under the bead has the third hardness. It has a region covered with a topping rubber having a high JISA hardness of 47 to 67 °, and the other region (located below the tread) is preferably covered with a topping rubber having a JISA hardness of 40 to 60 °. .
[0012]
[Function and effect]
According to the present invention, the carcass layer is covered with a topping rubber having two or more kinds of hardness, and the carcass region covered with the topping rubber having the highest hardness is provided in the vicinity of the buttress portion. And improving the steering stability. In other words, by providing a carcass region covered with high hardness topping rubber in the vicinity of the buttress part that does not contribute much to the longitudinal rigidity and easily contributes to the longitudinal rigidity and the lateral rigidity, while improving steering stability, road noise is reduced. Reduction and ride comfort can be improved.
[0013]
The carcass layer is covered with a cord with a topping rubber of three or more types of hardness, and the carcass layer of the portion rolled back with the bead has a region covered with the second highest hardness topping rubber More than 3 types of hardness can be selected, and finer hardness can be selected. By increasing the hardness of the part that has been rewound, both the comfort improvement effect and the steering stability improvement effect can be achieved more reliably. become able to.
[0014]
The carcass layer is coated with a topping rubber having four or more kinds of hardness, and the carcass layer in the region between the tire maximum width position and the tire inner periphery under the bead is the third hardest topping. In the case of having a region covered with rubber, it is possible to select a finer hardness in order to obtain four or more types of hardness, and because the hardness under the belt is relatively low, the comfortability is improved by the envelope effect. In addition, it is possible to more reliably achieve both the improvement effect of the comfortability and the improvement effect of the handling stability.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view showing an example of the pneumatic tire of the present invention.
[0016]
As shown in FIG. 1, the pneumatic tire according to the present invention includes a pair of annular beads 1a, a carcass layer 10 whose ends are wound back by the beads 1a, and a carcass layer 11a located below the tread. And a plurality of belt layers 6 to be reinforced by the above. The pneumatic tire has a cross-sectional structure that is symmetric or substantially symmetric with respect to the equator line CL. In the present embodiment, an example is shown in which the carcass layer 10 is composed of one layer.
[0017]
As the bead 1a, any of the same as a normal pneumatic tire can be adopted. For example, the bead 1a can be manufactured by winding a bead wire a plurality of times in a predetermined cross-sectional shape. A steel wire or the like is used as the bead wire, and surface treatment, adhesion treatment, or the like is usually performed in order to improve adhesion to rubber.
[0018]
A bead filler 1b is disposed on the tire outer periphery side of the bead 1a of the bead portion 1, and the hardness (after vulcanization) of the bead filler 1b is preferably 85 to 95 ° in terms of JISA hardness. The height H1 of the bead filler 1b is preferably 20 to 50% of the tire cross-section height H in order to achieve both a low-frequency road noise reduction effect and a steering stability improvement effect. More preferably, the height is ˜50%.
[0019]
The carcass layer 10 includes a main body portion 11 between the beads 1a and a rewinding portion 12 that is a portion that is rewinded by the beads 1a. In the present embodiment, an example in which the cord angle formed by the cord of the carcass layer 10 and the tire circumferential direction is 85 to 90 °. Examples of the cord constituting the carcass layer 10 include organic fibers such as rayon, polyester, polyamide, and aromatic polyamide, or steel.
[0020]
The belt layer 6 can be exemplified by a two-layer configuration of an upper layer 6b and a lower layer 6a, but the angle of the cords constituting each layer with respect to the tire equator line CL is preferably 10 to 35 °. Moreover, you may provide the fiber reinforcement layer 7 which has arrange | positioned the cord further in the circumferential direction on the upper surface of the upper layer 6b. As the cord material constituting the belt layer 6, any of the materials conventionally used for the belt layer 6 such as steel and organic fibers such as aromatic polyamide can be used.
[0021]
In the present invention, the carcass layer 10 is covered with a cord with a topping rubber having two or more kinds of hardness, preferably with a topping rubber with three or more kinds of hardness, more preferably with a topping rubber with four or more kinds of hardness. This is the case when it is covered. In the present embodiment, an example is shown in which the cord of the carcass layer 10 is covered with topping rubber having four types of hardness.
[0022]
In the present invention, the carcass layer 10 in the region between the outer end P1 of the lower layer 6a, which is the innermost belt layer, and the tire maximum width position P2 corresponding to the height of the tire maximum width W in the meridian section, It has a carcass layer C1 covered with the topping rubber with the highest hardness. The region occupied by the carcass layer C1 is preferably 50% or more, more preferably 60% or more, of the region between the outer end P1 and the tire maximum width position P2. If this is less than 50%, the effect of improving the longitudinal rigidity and lateral rigidity tends to be insufficient.
[0023]
The hardness (after vulcanization) of the topping rubber covering the carcass layer C1 is preferably 60-80 ° in terms of JISA hardness. Further, the hardness of the topping rubber in the region of the carcass layer C1 may be slightly different. In this case, the average value is the highest based on the average value of hardness (Σ area ratio × hardness). Next, the carcass layer C1 is disposed.
[0024]
In the present invention, it is preferable that the rewind portion 12 of the carcass layer 10 that has been rewinded by the bead 1a has the carcass layer C2 that is covered with the second highest hardness topping rubber. The region occupied by the carcass layer C2 is preferably 50% or more, and more preferably 60% or more, of the rolled-up portion 12. In the present invention, the boundary between the rewinding portion 12 and the main body portion 11 of the carcass layer 10 is the tire inner peripheral end P3 under the bead.
[0025]
The hardness (after vulcanization) of the topping rubber covering the carcass layer C2 is preferably 52 to 70 ° in terms of JISA hardness. The carcass layer C2 may have a slightly different hardness in the topping rubber within the region, and in this case, the carcass layer C2 is disposed so as to have the second highest hardness based on the average value of the hardness ( The same applies to the carcass layer C3).
[0026]
In the present invention, it is preferable that the carcass layer in the region between the tire maximum width position P2 and the tire inner peripheral end P3 under the bead has the carcass layer C3 covered with the third highest hardness topping rubber. The region occupied by the carcass layer C3 is preferably 50% or more, more preferably 60% or more, of the region between the tire maximum width position P2 and the tire inner peripheral end P3. The hardness (after vulcanization) of the topping rubber covering the carcass layer C3 is preferably 47 to 67 ° in terms of JISA hardness.
[0027]
The portions other than the carcass layers C1 to C3 are preferably covered with a topping rubber having a hardness lower than that of the carcass layer C3. Specifically, the hardness (after vulcanization) of the topping rubber is preferably 40 to 60 ° in terms of JISA hardness. In the present invention, it is preferable to use the carcass layer C4 covered with such a low hardness topping rubber for the carcass layer 11a located below the tread.
[0028]
In the present embodiment, as shown in FIG. 1, a chacher 21 that reinforces the outside of the carcass layer 10 is provided around the bead, and a flipper 22 that reinforces the inside of the carcass layer 10 is provided. As these, those having increased hardness of rubber or those reinforced with long fibers or short fibers can be used.
[0029]
Except for the above points, the tire has substantially the same structure as a normal radial tire. That is, as shown in FIG. 1, a side wall rubber 2a is arranged outside the carcass layer 10 and an inner liner rubber 3 is arranged inside the carcass layer 10, and a tread rubber 4 etc. is arranged outside the belt layer 6 as shown in FIG. The predetermined pattern is formed on the outer peripheral surface of the tread rubber 4.
[0030]
Examples of the raw rubber for the rubber layer include natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), and butyl rubber (IIR). These rubbers are reinforced with fillers such as carbon black and silica, and a vulcanizing agent, a vulcanization accelerator, a plasticizer, an antiaging agent, and the like are appropriately blended.
[0031]
The pneumatic tire of the present invention can be manufactured by the same manufacturing method as that of a normal pneumatic tire, except that carcass plies having different topping rubber hardness are used in each part. The carcass ply is formed into a cylindrical shape. For example, after a bead is disposed, a tubular airbag is inserted and shaped into a donut shape by internal pressure, and then a belt layer is formed by a conventional method.
[0032]
As a method of manufacturing a carcass ply having different topping rubber hardnesses in each part, for example, an unvulcanized rubber sheet is formed on both sides using a calender roll or a press device on a comb-like fabric in which a plurality of cords are arranged in parallel. A method of using unvulcanized rubber sheets having partially different hardness when laminating and covering the topping rubber may be mentioned.
[0033]
The thickness of the carcass ply is preferably 0.5 to 1.0 mm. Further, the number of cords to be driven is preferably 40 to 70/5 cm as in the case of a conventional radial tire.
[0034]
As a method for changing the hardness of the rubber, any conventionally known method can be used. Examples thereof include a method for changing the type and mixing ratio of a reinforcing material such as carbon black, and a method for changing the mixing ratio of the vulcanizing agent.
[0035]
[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described.
[0036]
(1) In the above-described embodiment, an example in which the carcass layer is composed of one layer has been described. However, in the present invention, two or more carcass layers 10 may be provided. Also in this case, the carcass layer 10 in the region between the outer end P1 of the lower layer 6a and the tire maximum width position P2 has the carcass layer C1 covered with the topping rubber having the highest hardness. At this time, the region of the carcass layer C1 in each layer may be the same or different in each layer. Further, the other regions may be provided with the regions of the carcass layers C2 to C3 in the same manner as described above.
[0037]
(2) In the above-described embodiment, an example is shown in which the cord of the carcass layer is coated with topping rubber having four types of hardness, but it may be coated with topping rubber having two types of hardness. In that case, the structure of the carcass layer can be a structure of 2 to 5 divisions from the center to the edge.
[0038]
In the case of a two-part structure, the hardness from the center to the vicinity of the belt end may be low and the outside may be high. In the case of a three-part structure, the hardness from the center to the vicinity of the belt end may be low hardness, the appropriate position from the rewind end to the tire maximum width position may be low hardness, and the middle may be high hardness. In the case of the 4-part structure, the hardness from the center to the vicinity of the belt end is low hardness, the region from the tire maximum width position to the tire inner peripheral edge under the bead is low hardness, the middle is high hardness, What is necessary is just to make the area | region from a tire inner peripheral end to the rewinding end high hardness. In the case of a four-part structure, a low-hardness region may be further disposed near the winding end.
[0039]
(3) Further, in the present invention, the cord of the carcass layer may be covered with topping rubbers having three kinds of hardness. In that case, the region of the carcass layer C3 shown in FIG. 1 is covered with a topping rubber having the same hardness as the region of the carcass layer C4, or the region of the carcass layer C3 is topped with the same hardness as the region of the carcass layer C2. It may be covered with rubber.
[0040]
(4) In the above-described embodiment, an example in which the cord angle of the winding portion of the carcass layer is 85 to 90 ° is shown. However, in the present invention, the cord of the winding portion 12 of the carcass layer 10 is shown in FIG. The corner may be inclined. Thereby, the lateral rigidity and the front-rear rigidity in the vicinity of the bead portion can be increased, so that both the improvement effect of the comfortability and the improvement effect of the steering stability can be achieved more reliably. In this case, the cord angle formed by the cord of the winding portion 12 and the tire circumferential direction is preferably 60 to 85 °.
[0041]
On the other hand, the same effect as described above can be obtained by inclining the cord angle of the carcass layer in the region between the outer end of the innermost belt layer and the tire maximum width position. Also in this case, the cord angle formed by the cord of the carcass layer and the tire circumferential direction is preferably 60 to 85 °.
[0042]
(5) In the above-described embodiment, the example in which the winding end of the winding portion of the carcass layer is arranged in the vicinity of the tire maximum width position has been shown, but the winding end of the winding portion is extended to a higher position. The end may be sandwiched between the end of the belt layer and the carcass layer. In that case, it is preferable that a region higher than the tire maximum width position in the turned-up portion is a carcass layer covered with a topping rubber having the highest hardness.
[0043]
【Example】
Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, the measurement of physical properties and performance evaluation in Examples and the like were performed as follows.
[0044]
(1) A load load (510 kg) based on a graph in which the relationship between the force in the front-rear direction and the deflection in the front-rear direction is measured by applying a force in the front-rear direction in a state where the air pressure of the front-rear rigid tire is 210 KPa and the load load is 510 kg. The force in the front-rear direction corresponding to 0.3 times the value is divided by the front-rear deflection when the force is applied.
[0045]
(2) Based on a graph in which the lateral force-lateral deflection relationship was measured by applying a lateral force in a state where the air pressure of the lateral rigid tire was 210 KPa and the load load was 510 Kg, the load load (510 Kg) The lateral force corresponding to 0.3 times the value was calculated by dividing by the lateral deflection when the force was applied.
[0046]
(3) From a state where the air pressure of the longitudinally rigid tire is 210 KPa and the load load is 510 Kg, applying a force in the vertical direction by the compression test air, the deflection of the tire when + 10% and −10% of the load load is applied. Measured and calculated by dividing the amount of load by the amount of deflection.
[0047]
(4) Steering stability Pneumatic tires of size 205 / 55R16 89V obtained in the working example and the like were mounted on an actual vehicle (2000cc class domestic sedan) with a rim assembly (rim: 6.5J) at an air pressure of 220 kPa. With this actual vehicle, an actual vehicle feeling test (straight ahead, lane change, handling stability) was conducted on the test course when dry, and the result was evaluated with an index where the conventional product was 100. The larger this value, the better the steering stability.
[0048]
(5) Ride comfort As with the handling stability, the actual vehicle feeling test (good road driving performance, rough road driving performance, harshness) was performed by the panelists on the dry test course, and the results were compared with the conventional products. Was evaluated with an index of 100. The larger this value, the better the riding comfort.
[0049]
(6) Road noise Using the same vehicle as the evaluation of steering stability, run on a test course (rough surface) at a speed of 60 km / h and run at a frequency of 125 Hz with a microphone attached to the ear position on the driver's seat side. Frequency road noise) level was measured.
[0050]
Example 1
In a comb-like material using rayon (1840 dtex, stress 2N elongation: 69 N / cord) as the cord, the JISA hardness changes from the center to both ends at 50 ° → 70 ° → 57 ° → 62 ° at predetermined intervals. An unvulcanized rubber sheet (thickness 0.2 mm) of a topping rubber to be (quarterly divided) was sandwiched from both sides to prepare a carcass ply with a driving number of 48/5 cm.
[0051]
Using this carcass ply and a bead filler forming member (JISA hardness 92 ° after vulcanization, triangle base 8 mm, height 45 mm), a carcass layer wound outward with a bead at a cord angle of 90 ° is formed. A pneumatic tire having a tire size of 205 / 55R16 89V as shown in FIG. 1 was prototyped in the same manner as a normal radial tire in other portions. The boundary of hardness 50 ° → 70 ° of the carcass layer of the obtained pneumatic tire is located at the outer end of the innermost belt layer, and the boundary of hardness 70 ° → 57 ° is 10 mm from the tire maximum width position. The boundary of hardness 57 ° → 62 ° was located at the inner peripheral edge of the tire under the bead.
[0052]
Example 2
In Example 1, except that the unvulcanized rubber sheet of topping rubber in which the JISA hardness changes from the center to both ends at 50 ° → 70 ° → 60 ° at predetermined intervals (three-part structure) was used. A pneumatic tire was manufactured in the same manner as in Example 1. The boundary of the hardness 50 ° → 70 ° of the carcass layer of the obtained pneumatic tire is located at the outer end of the innermost belt layer, and the boundary of the hardness 70 ° → 60 ° is located at the maximum tire width position. Was.
[0053]
Example 3
A pneumatic tire was prototyped in the same manner as in Example 1 except that the hardness of the topping rubber near the center in Example 1 was changed from 50 ° to 60 °. The boundary of the hardness 60 ° → 70 ° of the carcass layer of the obtained pneumatic tire is located at the outer end of the innermost belt layer, and the boundary of the hardness 70 ° → 57 ° is 10 mm from the maximum tire width position. The boundary of hardness 57 ° → 62 ° was located at the inner peripheral edge of the tire under the bead.
[0054]
Comparative example 1 (conventional product)
In Example 1, a pneumatic tire having the same tire size was prototyped in the same manner as a normal radial tire using a uniform carcass ply with a topping rubber hardness of 60 °.
[0055]
Comparative Example 2
In Example 1, except for using an unvulcanized rubber sheet of topping rubber in which the JISA hardness changes from the center to both ends at a predetermined interval of 70 ° → 50 ° → 62 ° → 57 ° (four-part structure), Pneumatic tires were all manufactured in the same manner as in Example 1. The boundary of the hardness 70 ° → 50 ° of the carcass layer of the obtained pneumatic tire is located at the outer end of the innermost belt layer, and the boundary of the hardness 50 ° → 62 ° is 10 mm from the maximum tire width position. The boundary between the hardness and the hardness of 62 ° → 57 ° was located at the inner peripheral edge of the tire under the bead.
[0056]
Table 1 shows the results of the evaluation using the above pneumatic tires.
[0057]
[Table 1]

As shown in the results of Table 1, according to the present invention, it is possible to achieve both an improvement effect of comfortability such as riding comfort and road noise and an improvement effect of steering stability. On the other hand, in Comparative Example 2 in which the magnitude relationship of the hardness of the topping rubber was partially reversed, the comfortability and handling stability such as riding comfort and road noise were all deteriorated.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing an example of a pneumatic tire of the present invention. FIG. 2 is a side view schematically showing a carcass layer of another example of the pneumatic tire of the present invention.
1a Bead 6 Belt layer 6a Lower layer (innermost belt layer)
DESCRIPTION OF SYMBOLS 10 Carcass layer 11 Carcass layer body part 12 Carcass layer rewinding part C1 Carcass layer C2 covered with the highest hardness topping rubber Carcass layer C3 covered with the second highest hardness topping rubber Third highest hardness Carcass layer covered with topping rubber P1 Outer edge of belt layer P2 Maximum tire width position P3 Inner tire edge under bead

Claims (3)

In a pneumatic tire comprising a pair of annular beads, a carcass layer whose ends are rolled back by the bead, and a plurality of belt layers that reinforce the carcass layer located below the tread by a tagging effect,
The carcass layer is coated with a topping rubber having two or more kinds of hardness, and the carcass layer in the region between the outermost end of the belt layer on the innermost peripheral side and the tire maximum width position has a hardness in the region. Based on the average value (Σ area ratio × hardness), the average value has the highest hardness of the JIS hardness of 60 to 80 ° covered with the topping rubber, and the other area has the JIS hardness of 40 A pneumatic tire characterized by being coated with a topping rubber of ˜70 ° . The carcass layer is coated with a topping rubber having a hardness of three or more kinds, and the carcass layer of the portion rewound by the bead is a topping rubber having a JIS hardness of 52 to 70 ° which is the second highest hardness. The pneumatic tire according to claim 1, wherein the other region is covered with a topping rubber having a JISA hardness of 40 to 67 ° . The carcass layer is coated with a topping rubber having four or more kinds of hardness, and the carcass layer in the region between the tire maximum width position and the tire inner peripheral edge under the bead is the third hardest JISA. The region covered with a topping rubber having a hardness of 47 to 67 °, and the other region (located below the tread) is covered with a topping rubber having a JIS hardness of 40 to 60 °. Pneumatic tires.

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