JP2011218972A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new pneumatic radial tire for heavy load, which causes arrangement of a member to be appropriate and improves durability of a bead portion without increasing weight and cost of the tire.SOLUTION: In the pneumatic radial tire for the heavy load, a reinforced rubber layer 9 arranged on an external side in a tire width direction of a folding portion 5c of a carcass ply 5 includes two types of rubbers of a low modulus rubber 9a and a high modulus rubber 9d. The low modulus rubber 9a is disposed between a perpendicular line A drawn from a tire external surface a whose height from reference becomes 2H to a body portion 5a of the carcass ply 5 and a perpendicular line B drawn from a tire external surface b whose height from the reference becomes H to the body portion 5a of the carcass ply 5 when height to an upper end of a flange 10b of an applied rim 10 is set to be H with an external lower end 1a in a width direction of the bead portion 1 as the reference in a tire meridian cross section when internal pressure is filled.

Description

  The present invention relates to a pneumatic radial tire used for construction vehicles and the like, and can be advantageously used as a heavy-duty pneumatic radial tire used particularly under heavy loads.

  In heavy-duty pneumatic radial tires used for heavy vehicles, the force acting on the bead portion during load rolling is large, and therefore the bead portion tends to fail, mainly due to separation failure. For example, nylon chafers and wire chases A fiber chafer such as a fur is added as a reinforcing member to suppress bending deformation from the sidewall portion to the bead portion during internal pressure filling and load application, so-called collapse deformation, and bead during tire rolling The durability of the stepping part and the kicking part in the part is improved. However, the addition of such a reinforcing member leads to an increase in the weight of the tire and an increase in cost due to an increase in material costs and manufacturing man-hours, and cannot satisfy market demands.

  Among heavy vehicle tires, especially for large construction vehicles, a middle turn that sets the height of the carcass ply folding end to the maximum width in the tire cross section in order to improve the cut resistance of the sidewalls. It is common to use an up-structure, but in this case, the largest distortion during rolling of the tire is not at the folded end but near the flange height of the rim, and the deflection rate under load is other than that. Therefore, it was difficult to obtain sufficient durability even if the reinforcing member was applied as it was.

  In recent years, with respect to such a problem, for example, as disclosed in Patent Document 1, the arrangement of members is optimized, and an attempt is made to improve the separation resistance in the bead portion without increasing the weight of the tire and increasing the cost. However, there has been room for improvement since the performance has not been fully satisfactory.

JP-A-10-76822

  An object of the present invention is to provide a new heavy-duty pneumatic radial tire capable of improving the durability in the bead portion without increasing the weight of the tire and increasing the cost by optimizing the arrangement of the members. There is to do.

The present invention has at least one main body part extending in a toroidal shape from the tread part to the sidewall part and the bead part, and a folded part obtained by folding the end part of the main body part around the bead core disposed in the bead part. A piece of carcass ply,
In a heavy-duty pneumatic radial tire provided with a reinforcing rubber layer disposed on the outer side in the tire width direction of the folded portion of the carcass ply and having a lower modulus than the rubber of the carcass ply,
The reinforcing rubber layer is composed of at least two kinds of rubbers including a low modulus rubber having a lowest modulus among the reinforcing rubber layers and a high modulus rubber having a highest modulus among the reinforcing rubber layers.
In a tire meridian cross section in which the tire is mounted on an applied rim and filled with internal pressure, the height from the outer lower end in the width direction of the bead portion to the upper end of the flange of the applied rim is H, and the tire outer surface a at the height H When the vertical line drawn from the outer surface b of the tire at a height of 2H toward the main body part of the carcass ply is defined as A, A heavy-duty pneumatic radial tire having the low modulus rubber disposed therebetween.

  It is desirable that the low modulus rubber is disposed closest to the folded portion of the carcass ply.

  The 100% modulus of the low modulus rubber is desirably 60% or less of the 100% modulus of the high modulus rubber.

  In the tire meridian cross section, when a perpendicular drawn from the tire outer surface c where the thickness of the rubber outside the folded portion of the carcass ply is the maximum toward the main body of the carcass ply is C, the low modulus rubber The thickness to the folded portion is preferably 20% or more of the thickness from the tire outer surface c to the folded portion.

  The low modulus rubber preferably has a cross-sectional shape that tapers from the folded portion of the carcass ply toward the outer surface of the tire.

  The 100% modulus of the high modulus rubber is preferably in the range of 3.4 MPa to 6.0 MPa.

  Of the reinforcing rubber layer disposed between the rim flange and the carcass ply turn-up portion, the low modulus rubber is disposed between the perpendicular lines A and B, so that the distortion in the carcass ply rubber near the rim flange is reduced. And separation failure is less likely to occur.

  Since the low modulus rubber is disposed closest to the folded portion of the carcass ply, the distortion in the carcass ply rubber can be more effectively reduced.

  Since the 100% modulus of the low modulus rubber is set to 60% or less of the 100% modulus of the high modulus rubber, the distortion in the carcass ply rubber can be further reduced.

  At the position where the thickness of the rubber outside the folded portion of the carcass ply becomes the maximum, the thickness of the low modulus rubber is set to 20% or more of the thickness of the rubber outside the folded portion, so that the distortion in the rubber of the carcass ply is sufficient. It is possible to suppress the separation failure and the separation failure is less likely to occur.

  Since the low modulus rubber is tapered from the folded part of the carcass ply toward the outer surface of the tire, in the reinforcing rubber layer, more rubber with higher modulus is distributed from the folded part to the outer surface of the tire. That is, it is possible to suppress the falling deformation in the bead portion.

  Since the 100% modulus of the high modulus rubber is in the range of 3.4 MPa to 6.0 MPa, the strain distribution in the rubber of the carcass ply does not change greatly, and the performance of the low modulus rubber is not impaired. It is possible to sufficiently exhibit the effect of reducing the above.

It is the figure which showed the tire meridian cross section about the left half upper part of a tire about embodiment of the pneumatic radial tire for heavy loads according to this invention. FIG. 2 is a tire meridian cross-sectional view showing an enlarged main part of a bead portion shown in FIG. 1. (A) is the model figure used for the computer simulation of the tire shown in FIG. 2, (b) is the model figure which changed the shape of the low modulus rubber | gum with respect to Fig.3 (a). FIG. 6 is a tire meridian cross-sectional view showing a tire in which the shape of the low modulus rubber is changed with respect to the tire shown in FIG. 2 according to another embodiment of the present invention. It is tire meridian sectional drawing which showed the conventional tire. It is a figure which shows the relationship between the thickness of the low modulus rubber, and the distortion | strain of the rubber | gum of a carcass ply. It is a figure which shows the relationship between the modulus of the low modulus rubber with respect to high modulus rubber, and the distortion | strain of the rubber | gum of a carcass ply. It is a figure which shows the relationship between the modulus of a high modulus rubber, and the distortion | strain of the rubber | gum of a carcass ply in the edge part of a low modulus rubber.

  Hereinafter, the present invention will be described more specifically with reference to the drawings.

  FIG. 1 is a diagram showing a tire meridian cross section of the embodiment of a heavy-duty pneumatic radial tire with respect to the upper left half of the tire, and FIG. 2 is an enlarged view of the main part of the bead portion shown in FIG. It is a tire meridian sectional view.

  In FIG. 1, 1 is a bead portion on the left side of the tire connected in the circumferential direction of the tire, 2 is a sidewall portion on the left side of the tire extending from the bead portion 1 toward the outer side in the radial direction of the tire, and 3 is a left side of the tire. It is a tread part which makes a toroidal shape straddling the side wall part 2 and the side wall part on the right side of the tire (not shown).

  Reference numeral 4 denotes a bead core disposed in the bead portion 1, which extends in the circumferential direction of the tire and has a ring shape. The bead core 4 is formed by bundling a plurality of bead wires made of, for example, high carbon steel, and the cross-sectional shape in the illustrated example is a hexagon, but various other shapes such as a quadrangle and a circle can be adopted.

  5 is a carcass ply. The carcass ply 5 has a configuration in which ply cords for reinforcement are arranged in a direction substantially perpendicular to the circumferential direction of the tire and the ply cords are embedded in rubber. As the rubber of the carcass ply 5, one having a relatively high modulus is used. In the example shown in the figure, it is composed of a single carcass ply. The carcass ply 5 has a main body portion 5a extending in a toroidal shape from the tread portion 3 through the sidewall portion 2 to the bead portion 1, and an end portion 5b extending from the main body portion 5a is directed around the bead core 4 from the inside to the outside. The folded portion 5c is formed. The end portion 5b has a middle turn-up structure in which the end portion 5b is pulled up above the maximum width of the tire in the meridian cross section of the tire shown in FIG. 1, thereby ensuring cut resistance.

  Reference numeral 6 denotes a belt layer composed of at least one belt disposed on the outer side in the radial direction of the tire with respect to the carcass ply 5. In the illustrated example, the belt layer 6 is formed by three belts. A reinforcing cord (not shown) is embedded in each belt of the belt layer 6. For example, the cord is spirally wound along the circumferential direction of the tire, or the cord is inclined and arranged with respect to the circumferential direction of the tire. The direction of the cords is mixed between the belts to satisfy the tire performance.

  7 is a rubber chafer. The rubber chafer 7 is wound around the outside of the carcass ply 5 in the bead portion 1 and protects the carcass ply 5 by preventing the bead portion 1 from being worn by rubbing against the rim during traveling. The rubber chafer 7 uses a relatively high modulus rubber.

  Reference numeral 8 denotes a stiffener for reinforcing the bead portion 1. The stiffener 8 is arranged on the outer side in the tire radial direction of the bead core 4 and has a shape that tapers toward the tread portion 3.

  Reference numeral 9 denotes a reinforcing rubber layer disposed outside the folded portion 5c of the carcass ply 5 in the tire width direction. The reinforcing rubber layer 9 is made of at least two kinds of rubbers having a lower modulus than the rubber of the carcass ply 5. The modulus of rubber of the reinforcing rubber layer 9 </ b> A is desirably lower than that of the rubber chafer 7. The reinforcing rubber layer 9 is preferably covered with rubber of the rubber chafer 7 or the sidewall portion 2 on the outer surface of the tire.

  FIG. 2 is a cross section of the tire meridian in a state where the tire according to the present invention is mounted on the applied rim 10 and the normal internal pressure is filled. The applied rim 10 includes a bead seat 10a on which the bead portion 1 is seated, and a flange 10b that rises from the outer end of the bead seat 10a and curves in a direction that protrudes outward in the tire radial direction. Here, “the state of being applied to the applicable rim and filled with the internal pressure” means that the tire is attached to the applicable rim specified by a predetermined industry standard, and the maximum size of the single wheel in the applicable size specified by the industry standard. The air pressure corresponding to the load (maximum load capacity) is filled and it means the state of no load. With regard to such industrial standards, standards that are effective in the regions where tires are produced or used are defined, and these standards include, for example, “The Tire and Rim Association Inc. YEAR BOOK” (including design guides) in the United States. ) (Hereinafter referred to as TRA standards) in Europe, “The European Tire and Rim Technical Organizations Standards”, and in Japan, “JATMA Year Book” of the Japan Tire Automobile Tire Association.

  The low modulus rubber 9a having the lowest modulus among the reinforcing rubber layers 9 has a height from the lower end 1a in the tire width direction of the bead portion 1 to the upper end of the flange 10b in the tire meridian section at the time of internal pressure filling shown in FIG. When the height is H, a normal line A drawn from the tire outer surface a having a height H from the reference toward the main body 5a of the carcass ply 5 and a tire outer surface having a height 2H from the reference It is arrange | positioned between the perpendicular B drawn toward the main-body part 5a of the carcass ply 5 from b. In the conventional heavy-duty radial tire, the deflection around the rim flange during load rolling is significantly larger than that of other types of tires, and a large compression is applied to the region between the flange 10b and the carcass ply 5. A large strain is generated in the region surrounded by the normal lines A and B in the rubber of the carcass ply 5, but in the heavy duty radial tire according to the present invention, the low modulus rubber 9a is disposed in the region. The carcass ply 5 is not greatly deformed, and the distortion can be reduced. The reinforcing rubber layer 9 excluding the low modulus rubber 9a is provided with a relatively high modulus rubber, so that the bead portion 1 can be supported so as not to fall down when a load is applied.

  The reinforcing rubber layer 9 is located outside the region defined by the vertical lines A and B, that is, the lower end 9b is positioned on the inner side in the tire radial direction from the vertical line A, and the upper end 9c is positioned on the outer side in the tire radial direction from the vertical line B. Is preferred. As a result, the portion of the reinforcing rubber layer 9 where the rubber having a relatively high modulus excluding the low modulus rubber 9a is arranged to extend long in the tire radial direction. The collapse deformation of the part from the wall part 2 to the bead part 1 is suppressed. In the example shown in FIG. 2, both the lower end 9 b and the upper end 9 c have a pointed tip, but may have a curved shape.

  The low modulus rubber 9a is preferably disposed closest to the folded portion 5c of the carcass ply 5. Thereby, the distortion can be more effectively reduced by the low modulus rubber 9a disposed closest to the carcass ply 5. Here, the term “adjacent” includes not only the case where the low modulus rubber 9a is in close contact with the folded portion 5c of the carcass ply 5, but also the case where it is slightly separated.

  The 100% modulus of the low modulus rubber 9a is preferably 60% or less of the 100% modulus of the high modulus rubber 9d. As a result, the moduli of the low modulus rubber 9a and the high modulus rubber 9d are optimized, and the distortion in the rubber of the carcass ply 5 can be further suppressed.

In the tire meridian cross section, a perpendicular drawn from the tire outer surface c where the thickness of the rubber outside the folded portion 5c of the carcass ply 5 is maximized toward the main body 5a of the carcass ply 5 is defined as C. In this perpendicular line C, and the length from the low modulus rubber 9a until the folded portion 5c and _{L 1,} in case where the length _{L 2} to the folded portion 5c from the outer surface of the tire _c, L 1 / _{L 2} is more than 20% Preferably there is. Thereby, the thickness of the low modulus rubber 9a is ensured, and the distortion in the rubber of the carcass ply 5 can be sufficiently suppressed.

The low modulus rubber 9a has a cross-sectional shape that tapers from the folded portion 5c toward the outer surface of the tire (thickness direction) in the tire meridian cross section in a state where the normal internal pressure is filled, that is, the carcass ply 5 of the low modulus rubber 9a. When the portion from the side end portions 9a ₁ to 9a ₂ is the inner edge portion and the end portions 9a ₃ to 9a ₄ on the tire outer surface side are the outer edge portions, the length of the outer edge portion is shorter than the length of the inner edge portion. It is preferable. Thereby, in the reinforced rubber layer 9, as the folded portion 5c approaches the outer surface of the tire, more rubber having a high modulus is distributed, and the collapse deformation at the bead portion 1 can be effectively suppressed. . The end portions 9a ₃ and 9a ₄ may be matched so that the low modulus rubber 9a has a substantially triangular shape, or is bent from the end portions 9a ₁ to 9a ₃ through 9a ₄ to 9a _2. The shape may be smoothly curved without providing an end. In addition, when the portion from the end portions 9a ₁ to 9a ₃ is the lower edge and the portion from the end portions 9a ₂ to 9a ₄ is the upper edge, the lower edge and the upper edge may be straight or curved. It may be.

  In the example of FIG. 2, the low modulus 9a is arranged in such a manner that the reinforcing rubber layer 9 is divided into three. For example, as shown in FIG. 4, the low modulus 9a is thinned to reduce the reinforcing rubber layer 9a. Nine other rubbers may surround the low modulus 9a.

  The 100% modulus of the high modulus rubber 9d is preferably in the range of 3.4 MPa to 6.0 MPa. Within this range, the strain distribution in the rubber of the carcass ply 5 is not greatly changed, and the performance of the low modulus rubber 9a is not impaired, so that the effect of reducing the strain can be sufficiently exhibited. Moreover, by setting it as the said range, it becomes possible to optimize the range of the high modulus rubber | gum 9d, and to suppress the fall deformation | transformation of the bead part 1 effectively.

  As shown in FIGS. 2 and 4, the low modulus rubber 9 a is preferably covered with a rubber chafer 7 at the outer edge. Thereby, it can support so that bead part 1 may not fall down at the time of load loading.

  Using the models shown in FIGS. 3A and 3B, the peak positions of strains in the rubber of the carcass ply were investigated. In addition, a tire having a size of 59 / 80R63 under the following conditions is prototyped, and this tire is mounted on a regular rim (5 ° taper rim) defined in the TRA standard and a regular internal pressure of 700 Kpa, a load of 101.6 tons (about 100 % Load), the thickness of the low modulus rubber, the modulus of the low modulus rubber relative to the high modulus rubber, the optimum value of the modulus of the high modulus rubber, and the durability of the bead portion were investigated. In each tire, the reinforcing rubber layer was composed of two types of low modulus rubber and high modulus rubber. The rubber modulus was measured according to JIS K6251-1993, and the measurement was performed in an environment of 23 ° C.

The peak position of strain in the carcass ply rubber was investigated by computer simulation using the models shown in FIGS. 3 (a) and 3 (b). 3A shows a case where the end portions 9a ₁ and 9a ₂ of the low modulus rubber 9a are on the vertical lines A and B, respectively, and FIG. 3B shows that the end portions 9a ₁ and 9a ₂ are on the vertical line A. And B are shown inside.

The thickness of the low modulus rubber, preparing a tire of changing the length L ₁ to the folded portion 5c with respect to the length L ₂ from the outer surface of the tire c until the folded portion 5c from the low modulus rubber 9a, the load Below, the distortion of the carcass ply rubber was investigated. The results are shown in FIG.

  For the modulus of the low modulus rubber relative to the high modulus rubber, a tire was prepared by changing the 100% modulus of the low modulus rubber to the 100% modulus of the high modulus rubber, and the distortion of the carcass ply rubber was examined under the above load. . The modulus of the carcass ply rubber, which is the upper limit of the modulus, was used as the modulus of the high modulus rubber as a reference. FIG. 7 shows the results including the distortion of the reference tire of the conventional example in which the reinforcing member is made of a single rubber as shown in FIG.

For the optimum modulus of the high modulus rubber, a tire with a changed modulus of the high modulus rubber was prepared, and the distortion of the carcass ply rubber at the end 9a ₂ of the carcass ply rubber was examined under the above load. FIG. 8 shows the result including the distortion of the reference tire as the conventional example shown in FIG.

The durability of the bead portion is shown in FIG. 2, in which the low modulus rubber is an area surrounded by the perpendicular lines A and B and is arranged adjacent to the carcass ply, and L ₁ / L ₂ is 60% on the perpendicular line C. And the tire shown in FIG. 4 in which the low modulus rubber is surrounded by the vertical lines A and B and is adjacent to the carcass ply, and the L ₁ / L ₂ is 20% on the vertical line C. Were prepared and checked with a drum testing machine having a drum diameter of 5 m. The drum was rotated under the condition that the surface speed of the tire was 10 km / h, and the load was increased stepwise by 10% every 24 hours, and the time until the failure of the bead part could be visually confirmed was investigated. . At this time, the rubber in the tread portion was scraped off so that the first failure occurred in the bead portion. The results are shown in Table 1, including the conventional reference tire shown in FIG.

As a result, the peak position of the strain in the rubber of the carcass ply was on the perpendicular C in the model shown in FIG. 3A and the end 9a ₂ in the model shown in FIG. That is, in any case, since the low modulus rubber is disposed at the portion where the strain peak exists, it was confirmed that the strain can be effectively reduced.

As shown in FIG. 6, the thickness of the low modulus rubber increases the internal distortion of the carcass ply when L ₁ / L ₂ is up to 20%. However, when the thickness is 20% or more, the distortion can be kept almost constant. It was confirmed that it was possible.

  As shown in FIG. 7, the modulus of the low modulus rubber with respect to the high modulus rubber has a tendency that the strain increases as the modulus ratio increases. It was confirmed that when the 100% modulus of the low modulus rubber is 60% or less of the 100% modulus of the high modulus rubber, it can be made smaller than the distortion of the reference tire as a conventional example.

As you increase the modulus of the high modulus rubber, distortion of the rubber of the carcass ply at the ends 9a ₂ low modulus rubber, it tends to increases after once decreased as shown in FIG. 8 revealed. It has been confirmed that when the modulus of the high modulus rubber is 3.4 MPa to 6.0 MPa, it can be made smaller than the strain of the reference tire as a conventional example.

  It was confirmed that the conforming tires 1 to 4 according to the present invention have a longer running time until failure and the durability of the bead portion is improved with respect to the reference tire as a conventional example. In particular, tires (compatible tires 3 and 4) in which the value of the 100% modulus of the low modulus rubber is small and the value of the 100% modulus of the high modulus rubber is large relative to the 100% modulus of the high modulus rubber were particularly good.

  According to the present invention, it is possible to stably provide a heavy-duty pneumatic radial tire that can improve durability in the bead portion without increasing the weight of the tire or increasing the cost by optimizing the arrangement of the members. Can supply.

DESCRIPTION OF SYMBOLS 1 Bead part 1a Width direction outer side lower end 2 Side wall part 3 Tread part 4 Bead core 5 Carcass ply 5a Main body part 5b End part 5c Folding part 6 Belt layer 7 Rubber chafer 8 Stiffener 9 Reinforcement rubber layer 9a Low modulus rubber 9d High modulus rubber 10 Applicable rim 10a Bead seat 10b Flange

Claims (6)

At least one carcass ply having a main body part extending in a toroidal shape from the tread part to the side wall part and the bead part, and a folded part obtained by folding the end part of the main body part around the bead core disposed in the bead part. When,
In a heavy-duty pneumatic radial tire provided with a reinforcing rubber layer disposed on the outer side in the tire width direction of the folded portion of the carcass ply and having a lower modulus than the rubber of the carcass ply,
The reinforcing rubber layer is composed of at least two kinds of rubbers including a low modulus rubber having a lowest modulus among the reinforcing rubber layers and a high modulus rubber having a highest modulus among the reinforcing rubber layers.
In a tire meridian cross section in which the tire is mounted on an applied rim and filled with internal pressure, the height from the outer lower end in the width direction of the bead portion to the upper end of the flange of the applied rim is H, and the tire outer surface a at the height H When the vertical line drawn from the outer surface b of the tire at a height of 2H toward the main body part of the carcass ply is defined as A, A heavy-duty pneumatic radial tire having the low modulus rubber disposed therebetween.   2. The heavy-duty pneumatic radial tire according to claim 1, wherein the low modulus rubber is disposed closest to a folded portion of the carcass ply.   3. The heavy-duty pneumatic radial tire according to claim 1, wherein a 100% modulus of the low modulus rubber is 60% or less of a 100% modulus of the high modulus rubber.   In the tire meridian cross section, when a perpendicular drawn from the tire outer surface c where the thickness of the rubber outside the folded portion of the carcass ply is the maximum toward the main body of the carcass ply is C, the low modulus rubber 4. The heavy-duty pneumatic radial tire according to claim 1, wherein a thickness to the folded portion is 20% or more of a thickness from the tire outer surface c to the folded portion.   5. The heavy-duty pneumatic radial tire according to claim 1, wherein the low modulus rubber has a cross-sectional shape that tapers from a folded portion of the carcass ply toward an outer surface of the tire.   The pneumatic radial tire for heavy loads according to any one of claims 1 to 5, wherein a 100% modulus of the high modulus rubber is in a range of 3.4 MPa to 6.0 MPa.

Images