JP3636237B2 - Pneumatic radial tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire with improved bead durability.
[0002]
[Prior art]
Generally, when a pneumatic radial tire is loaded and rolled, a sidewall portion corresponding to the ground contact region is bent and deformed, and when such deformation is transmitted to the bead portion, an outer portion in the tire axial direction of the bead portion, In particular, in order to generate a large compressive strain in the vicinity of the radially outer end of the folded portion of the carcass layer, cracks occur in the rubber surrounding the radially outer end of the folded portion, eventually causing separation and causing tire failure. I was invited.
[0003]
Conventionally, in order to suppress such compressive strain, for example, as shown in FIG. 5, a large number of steel cords in which the carcass layer 2 in the bead portion 1 is inclined at an angle of 60 degrees with respect to the meridian direction are embedded. The wire chafer 3 has been proposed to increase the bending rigidity of the bead portion 1 and consequently reduce the bending deformation of the sidewall portion 4.
[0004]
[Problems to be solved by the invention]
Such a tire 5 has a considerable degree of bead durability, but in recent years, the flattening of the tire 5 has progressed, and the demand for longer life (including rehabilitation) from the market has also increased. Therefore, it was necessary to further improve the durability of the bead part.
[0005]
For this reason, the present inventor has conducted extensive research on the tire 5 as described above, and cracks occurring at the radially outer end of the folded portion 6 of the carcass layer 2 are caused by the deformation of the sidewall portion 4 as described above. In the past, it has been thought that only the compression distortion based on the cause is the cause, but it has been found that it occurs due to the cause described below in addition to the compression distortion. That is, when a braking force is applied to the tire 5 during traveling, the sidewall portion 4 corresponding to the ground contact region is deformed in the circumferential direction due to friction with the road surface, and thereby the reinforcing cord embedded in the main body portion 7. 8a bends like a bow as shown in FIG. However, such a deformation based on braking is blocked at the bead core 9 and thus is not transmitted to the folded portion 6, and the reinforcing cord 8b in the folded portion 6 maintains a state of extending in the radial direction. As a result, during braking as described above, circumferential shear strain occurs in the rubber between the reinforcing cord 8a in the main body portion 7 and the reinforcing cord 8b in the folded portion 6, and in addition, in the aforementioned main body portion 7 Since the amount of deformation in the circumferential direction of the reinforcing cord 8a increases toward the outer side in the radial direction, the shear strain becomes the maximum around the radially outer end 6a of the folded portion 6, and as a result, the radial direction of the folded portion 6 Cracks occur in the rubber surrounding the outer end.
[0006]
The present invention provides a pneumatic radial tire that effectively suppresses cracks and separation at the radially outer end of the folded portion by reducing the compressive strain and shear strain at the radially outer end of the folded portion. Objective.
[0007]
[Means for Solving the Problems]
The purpose is to extend from the vicinity of the bead core to the outer end in the radial direction of the folded portion and the maximum tire width position, and be overlapped in close contact with the main body of the carcass layer. almost many inextensible cord of the orthogonal providing a reinforcing layer extending continuously in the buried circumferentially Rutotomoni, the folded portion of the radially outer ends 100% modulus of 60 ~ 80 kgf rubber chafer near / mm consisting ^{2. the} term rubber provided high modulus region can be achieved by Rukoto.
[0008]
When braking force is applied to the tire during traveling, the sidewall portion corresponding to the ground contact region is deformed in the circumferential direction, and the reinforcing cord in the main body portion tends to bend like a bow. However, as described above, the reinforcing layer extending from the vicinity of the bead core to the outer end in the radial direction of the folded portion and the tire maximum width position is superposed in close contact with the main body portion of the carcass layer, and the carcass is placed inside the reinforcing layer. Since a large number of non-stretchable cords that are substantially orthogonal to the reinforcing cords in the layer are embedded, the main body portion of the portion that overlaps the reinforcing layer, that is, the portion that overlaps at least the folded portion, is not in the reinforcing layer. It is strongly constrained by the extensible cord and can hardly be deformed. As a result, the reinforcing cord in the overlapping portion substantially maintains the radial extension substantially parallel to the reinforcing cord in the folded portion. As a result, almost no circumferential shear strain occurs in the rubber between the main body and the folded portion, and the occurrence of cracks in the rubber surrounding the radially outer end of the folded portion is effectively suppressed. At this time, the reinforcing cords in the main body are concentrated and bent in a bow shape in a region radially outward from the reinforcing layer. In addition, when the reinforcing layer embedded with the non-extensible cord that is substantially orthogonal to the reinforcing cord as described above is superimposed on the main body, the rigidity of the portion where the reinforcing layer and the main body overlap each other is significantly increased. The influence is given to the surrounding rubber, in particular, the rubber surrounding the radially outer end of the folded portion, and deformation of the rubber is suppressed. For these reasons, the compression and shear strain generated in the rubber surrounding the radially outer end of the folded portion is reduced, and the generation of cracks is further effectively suppressed.
[0009]
Here, the arrangement position of the reinforcing layer may be any outside in the axial direction of the main body, that is, between the main body and the stiffener, or inside in the axial direction of the main body, that is, between the main body and the inner liner. If anything, the former is preferred. The reason for this is that if the reinforcing layer is arranged like the former, the reinforcing layer is arranged close to the folded portion, so that the reinforcing effect of the rubber around the folded portion by the reinforcing layer is increased. This is because the distortion of the rubber surrounding the end portion can be effectively reduced.
[0010]
The inner end of the reinforcing layer in the radial direction is disposed in the vicinity of the bead core, but it is better to approach the bead core in order to reduce partial deformation of the main body. Further, when the radially outer end of the reinforcing layer is disposed between a point A separated by 15 mm and a point B separated by 30 mm radially outward from the radially outer end of the folded portion along the main body, It is possible to reliably suppress cracks and separation at the radially outer end of the. Here, the crossing angle between the non-extensible cord in the reinforcing layer and the reinforcing cord in the main body is preferably in the range of 85 degrees to 90 degrees.
[0011]
Furthermore, a high modulus region made of rubber having a 100% modulus of 60 to 80 kgf / mm ² is provided in a rubber chafer near the radially outer end of the folded portion, and the radially outer end of the high modulus region is turned to the folded portion. Is arranged in a range of 10 mm to 30 mm radially outward along the rubber chafer from the radially outer end of the inner surface, and the radially inner end of the folded portion is 15 mm along the rubber chafer from the radially outer end. If it is arranged in a range separated by 45 mm radially inward, cracks and separation at the radially outer end of the folded portion can be more strongly suppressed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1, 2, and 3, 11 is a pneumatic radial tire. This tire 11 has a pair of bead cores 12 and a carcass layer 13, and this carcass layer 13 is at least one, here, one carcass ply. It consists of 14. The carcass layer 13 is disposed between the bead cores 12 and extends in a toroidal shape, and the carcass layer 13 is wound up from the inner side in the axial direction to the outer side in the axial direction while surrounding the bead core 12, thereby The folded portion 16 is arranged on the outer side in the direction and extends substantially in parallel with the main body portion 15 toward the outer side in the radial direction. A large number of reinforcing cords 17 extending in the radial direction (meridian direction) made of steel wire or the like are embedded in the carcass layer 13. A pair of stiffeners 20 are installed on the outer side in the axial direction of the main body part 15 along the main body part 15 from the bead core 12 and extend almost radially outward while being in close contact therewith. The part 16 has penetrated, and the radially outer ends of the stiffeners 20 are located in the vicinity of the tire maximum width position H. A belt layer 22 is provided outside the carcass layer 13 in the radial direction, and the belt layer 22 is formed by laminating at least two belt plies 23 (three in this case) having steel cords embedded therein. ing. The cords embedded in the belt plies 23 intersect with the tire equatorial plane S at a predetermined angle. A top tread 24 is disposed on the outer side in the radial direction of the belt layer 22, and a plurality of (here, four) main grooves 25 extending in the circumferential direction intersect the main groove 25 on the outer surface of the top tread 24. A plurality of lateral grooves (not shown) are formed. Reference numeral 26 denotes a side tread disposed outside the main body 15 and the stiffener 20 in the axial direction.
[0013]
31 is a pair of reinforcing layers that are interposed between the main body portion 15 and the stiffener 20 of the carcass layer 13 so as to be in close contact with the outer side of the main body portion 15 in the axial direction. The reinforcing layer 31 extends continuously in the circumferential direction. Here, the reinforcing layer 31 may be overlapped in a state of being in close contact with the inner side in the axial direction of the main body part 15, but when the reinforcing layer 31 is disposed on the outer side in the axial direction as in the present embodiment, the reinforcing layer 31 is disposed in the vicinity of the folded portion 16 Therefore, the effect of suppressing deformation of rubber around the folded portion 16 by the reinforcing layer 31 is increased, and thereby, distortion of rubber surrounding the radially outer end portion of the folded portion 16 can be effectively reduced. . For this reason, it is preferable that the reinforcing layer 31 be disposed on the outer side in the axial direction as in this embodiment.
[0014]
The reinforcing layer 31 has a radially inner end 31a positioned in the vicinity of the bead core 12, and a radially outer end 31b positioned between the radially outer end 16a of the folded portion 16 and the maximum tire width position H. As a result, the reinforcing layer 31 extends from the vicinity of the bead core 12 to between the radially outer end 16a of the folded portion 16 and the tire maximum width position H. Here, the radially inner end 31a of the reinforcing layer 31 is positioned in the vicinity of the bead core 12 when the radially inner end 31a is far away from the bead core 12 in the radially outward direction. Is applied, the main body portion 15 between the radially inner end 31a and the bead core 12 is deformed in the circumferential direction, and shear strain as described in the prior art occurs at the radially outer end 16a of the folded portion 16. Because it does. Therefore, the closer the inner radial end 31a of the reinforcing layer 31 is to the bead core 12, the lower the partial deformation of the main body 15, that is, the deformation of the main body 15 between the radial inner end 31a and the bead core 12. Can do. In addition, the radially outer end 31b of the reinforcing layer 31 is positioned between the radially outer end 16a of the folded portion 16 and the tire maximum width position H because the radially outer end 31b is in the radial direction of the folded portion 16. If the tire 11 is positioned radially inward from the outer end 16a, the tire 11 may be deformed in the circumferential direction by the circumferential deformation that occurs in the main body portion 15 radially outward from the radially outer end 31b. This is because a large shear strain similar to that described above is generated at the radially outer end 16a of the turned-up portion 16. On the other hand, when the radially outer end 31b is located radially outside the tire maximum width position H, This is because the length in the radial direction of the deformable main body 15 when braking the tire 11 becomes too short, and as a result, the strain at the deformed portion becomes abnormally large. And the radial direction outer end 31b of such a reinforcement layer 31 is separated from the radial direction outer end 16a of the turned-up portion 16 along the main body portion 15 by 15 mm radially outward and point B separated by 30 mm. It is preferable to arrange | position between. The reason is that if the radial outer end 31b is arranged in the above-mentioned range, the radial length of the deformable main body 15 during braking of the tire 11 is sufficient, while the radial outer end of the folded portion 16 is sufficient. This is because the shear strain at 16a can be reliably reduced.
[0015]
Further, a large number of non-extensible cords 32 are embedded in the reinforcing layer 31 so as to be substantially orthogonal to the reinforcing cords 17 in the carcass layer 13, that is, to extend in the circumferential direction. Here, it is preferable that the non-extensible cord 32 in the reinforcing layer 31 and the reinforcing cord 17 in the main body 15 intersect each other in a range of 85 degrees to 90 degrees. The reason is that when the crossing angle G is less than 85 degrees, the non-extensible cord 32 and the reinforcing cord 17 are deformed by pantograph when the tire 11 is braked, and the circumferential deformation of the main body portion 15 cannot be effectively suppressed. Because there are cases.
[0016]
Since the portion overlapping the reinforcing layer 31 as described above, that is, the main body portion 15 at least overlapping the folded portion 16 is strongly restrained by the non-extensible cord 32 in the reinforcing layer 31. Even if a braking force is applied during traveling, it can hardly be deformed. As a result, the reinforcing cord 17a in the main body 15 is substantially the same as the reinforcing cord 17b in the folded portion 16 as shown in FIG. Maintain almost parallel radial extension. As a result, almost no shearing strain in the circumferential direction is generated in the rubber (stiffener 20) between the main body portion 15 and the folded portion 16, and cracking of the rubber surrounding the radially outer end portion of the folded portion 16 is effective. Is suppressed. At this time, the reinforcing cord 17a in the main body portion 15 is concentrated and bent in a bow shape in a region radially outward from the radially outer end 31b of the reinforcing layer 31. In addition, when the reinforcing layer 31 in which the non-extensible cord 32 substantially orthogonal to the reinforcing cord 17 is embedded as described above is superimposed on the main body portion 15, the rigidity of the portion where the reinforcing layer 31 and the main body portion 15 overlap each other. Is significantly increased, and the influence thereof is given to the surrounding rubber, in particular, the rubber surrounding the outer end portion in the radial direction of the folded-back portion 16, and the deformation of the rubber is suppressed. For these reasons, the compression and shear strain generated in the rubber surrounding the radially outer end of the folded portion 16 is reduced, and the generation of cracks is further effectively suppressed.
[0017]
Reference numeral 35 denotes a pair of rubber chafers covering the folded portion 16, and these rubber chafers 35 are arranged on the outer side in the axial direction of the folded portion 16 and the side tread 26. Each rubber chafer 35 is provided with a high modulus area 36 in the vicinity of the radially outer end 16a of the folded portion 16, that is, in an approximate radial position, and the high modulus area 36 has a 100% modulus of 60 to 80 kgf / and a rubber is mm ^2. As described above, when the rubber chafer 35 in the vicinity of the radially outer end 16a of the folded portion 16 is provided with the high modulus region 36 in the above-described range having high rigidity, the rubber surrounding the radially outer end portion of the folded portion 16 is It is sandwiched from both sides by the high modulus region 36 and the highly rigid portion where the reinforcing layer 31 and the main body 15 overlap each other, so that deformation is strongly suppressed and cracking is strongly suppressed. If the 100% modulus of the rubber constituting the high modulus region 36 exceeds 80 kgf / mm ² , the crack progressability is greatly reduced and the tire performance is deteriorated, so that it cannot be used. The rubber chafer 35 other than the high modulus region 36 is made of a general chafer rubber having a 100% modulus of 30 to 58 kgf / mm ² . And the radial outer end 36a of the high modulus region 36 is disposed in a range M that is 10 mm to 30 mm away from the radial outer end 16a of the folded portion 16 along the rubber chafer 35 radially outward, The radially inner end 36b is preferably disposed in a range N that is separated from the radially outer end 16a of the folded portion 16 along the rubber chafer 35 by 15 mm to 45 mm radially inward. The reason for this is that if the distance from the radially outer end 36a to the radially outer end 16a is less than 10 mm or the distance from the radially inner end 36b to the radially outer end 16a is less than 15 mm, This is because the deformation of the rubber surrounding the end cannot be sufficiently suppressed, while the distance from the radially outer end 36a to the radially outer end 16a exceeds 30 mm or radially outward from the radially inner end 36b. If the distance to the end 16a exceeds 45 mm, the installation range of the high modulus area 36 becomes too wide and enters the high deformation area, so that cracks are likely to occur and tire performance may deteriorate. It is.
[0018]
Next, test examples will be described. In this test, the conventional tire provided with the wire chafer 3 as shown in FIG. 5, the test tire 1 provided with only the reinforcing layer 31 shown in FIGS. A test tire 2 provided with both a reinforcing layer 31 and a high modulus region 36 having a 100% modulus of 70 kgf / mm ² was prepared. Here, the reinforcing layer 31 of the test tires 1 and 2 is embedded with a non-extensible cord 32 having a crossing angle G of 90 degrees therein, and its radially outer end 31b is radially outside the folded portion 16. Further, the radial outer end 36a and the radial inner end 36b of the high modulus region 36 in the test tire 2 are separated from the radial outer end 16a of the folded portion 16 by 20 mm and 30 mm, respectively. And conventionally, the tire sizes of the test tires were all 275 / 70R22.5. Next, after filling each tire with an internal pressure of 9.0 kgf / cm ² and applying a 180% load of JATMA standard, it is pressed against the drum at 60 km / h at the radially outer end 16a of the folded portion 16 at 60km / h. The car was run until a failure occurred. Assuming that the running distance of the conventional tire at this time is an index of 100, the test tire 1 is 120 and the test tire 2 is 130, and the bead durability is greatly improved.
[0019]
【The invention's effect】
As described above, according to the present invention, cracks and separation at the radially outer end of the folded portion can be effectively suppressed.
[Brief description of the drawings]
FIG. 1 is a meridian sectional view showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view in the vicinity of a bead portion.
FIG. 3 is a view taken along arrows II of FIG.
FIG. 4 is a side view with a part broken away for explaining a state during braking.
FIG. 5 is a cross-sectional view showing the vicinity of a bead portion of a conventional pneumatic radial tire.
FIG. 6 is a side view with a part broken away for explaining a state during braking.
[Explanation of symbols]
11 ... Pneumatic radial tire 12 ... Bead core
13 ... Carcass layer 15 ... Main body
16 ... turn-up part 16a ... radial direction outer end
17 ... Reinforcement cord 20 ... Stiffener
22 ... belt layer 24 ... top tread
31 ... Reinforcing layer 31b ... Radial outer edge
32 ... Non-extensible cord 35 ... Rubber chafer
36 ... High modulus region 36a ... Outer end in radial direction
36b ... Radial inner end H ... Tire maximum width position

Claims (2)

It consists of a pair of bead cores, a toroidal main body disposed between the bead cores, and a folded portion wound around the bead core from the inside to the outside, and a plurality of reinforcing cords extending in the meridian direction are embedded inside A carcass layer, a belt layer and a top tread disposed radially outward of the main body, a stiffener extending substantially radially outward from the bead core along the main body, and covering the outer side in the axial direction of the folded portion. In a pneumatic radial tire provided with a rubber chafer disposed, the pneumatic tire extends from the vicinity of the bead core to a position between the radially outer end of the folded portion and the maximum tire width position, and overlaps with the main body of the carcass layer. A large number of non-stretchable cords that are substantially orthogonal to the reinforcing cords in the carcass layer are embedded inside. Has been circumferentially disposed reinforcing layer extending continuously Rutotomoni, the high modulus region 100% modulus of rubber is 60 ~ 80 kgf / mm ² in the radially outer end near the rubber chafer of the folded portion A pneumatic radial tire characterized by being provided . The radially outer end of the high modulus region is arranged in a range away from the radially outer end of the folded portion by 10 mm to 30 mm radially along the rubber chafer, and the radially inner end of the high modulus region is The pneumatic radial tire according to claim 1 , wherein the pneumatic radial tire is arranged in a range separated from the radially outer end of the folded portion by 15mm to 45mm radially inward along the rubber chafer .

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