JP6454181B2 - Heavy duty pneumatic tire and manufacturing method thereof - Google Patents

Description

  The present invention relates to a heavy duty pneumatic tire excellent in bead durability and a method for manufacturing the same.

  Conventionally, heavy-duty pneumatic tires mounted on trucks, buses, etc. have improved bead durability by reinforcing the bead portion. For example, Patent Document 1 below includes a carcass ply having a folded portion folded around a bead core of the bead portion and a reinforcing cord filler disposed along the folded portion in order to improve bead durability. It proposes a heavy duty pneumatic tire.

JP 2013-129219 A

  As a result of various experiments by the inventors, it has been found that the difference in height between the outer end of the folded portion of the carcass ply and the outer end of the reinforcing cord filler greatly affects the bead durability. However, in the past, examinations focusing on these height differences have not been sufficiently conducted.

  The present invention has been devised in view of the above circumstances, and further improves the bead durability based on defining the difference in height between the outer end of the carcass ply and the outer end of the reinforcing cord filler. The main object is to provide a heavy-duty pneumatic tire that can be used and a method for manufacturing the same.

  The present invention is a heavy duty pneumatic tire having a carcass extending from a tread portion through a sidewall portion to a bead portion, wherein the carcass extends from the tread portion through the sidewall portion to a bead core of the bead portion. A carcass ply having a main body portion and a folded portion that is connected to the main body portion and is folded from the inner side to the outer side in the tire axial direction around the bead core, and the bead portion includes at least the outer side in the tire axial direction of the folded portion The reinforcing cord filler extending along the folded portion is disposed, and the height h1 of the outer end of the reinforcing cord filler is smaller than the height h2 of the outer end of the folded portion, and those The difference h2-h1 is 5 to 15 mm.

  In the heavy-duty pneumatic tire according to the present invention, an insulation rubber is disposed between the folded portion and the outer portion in the bead portion, and the height of the outer end of the insulation rubber in the tire radial direction is increased. The length h3 is preferably larger than the height h2 of the folded portion, and the difference h3-h2 is preferably 5 to 10 mm.

  In the heavy-duty pneumatic tire according to the present invention, the height h4 of the inner end in the tire radial direction of the insulation rubber is smaller than the height h1 of the outer end of the reinforcing cord filler, and the difference therebetween. The reinforcing cord fillers h1-h4 are preferably 10-15 mm.

  The present invention is a method for producing a heavy duty pneumatic tire, the preparation step of preparing the sheet-like reinforcing cord filler, the sheet-like carcass ply, and the insulation rubber having a substantially obtuse triangle in cross section And a stratification process in which the reinforcing cord filler, the insulation rubber, and the carcass ply are wound in that order on a cylindrical molding drum, and in the stratification process, an apex of the obtuse angle of the insulation rubber is obtained. It winds toward the said reinforcement cord filler side, It is characterized by the above-mentioned.

  In the method for manufacturing a heavy duty pneumatic tire according to the present invention, the insulation rubber includes a short side and a long side sandwiching the apex of the obtuse angle, and in the stratification step, the long side is reinforced with the reinforcement. It is desirable to contact the cord filler.

  The bead portion of the heavy-duty pneumatic tire of the present invention is provided with a reinforcing cord filler extending along the folded portion at least on the outer side in the tire axial direction of the folded portion of the carcass ply. In such a bead portion, bending strain outward in the tire axial direction is reduced by the reinforcing cord filler, and as a result, bead durability is improved.

  The height h1 of the outer end of the reinforcing cord filler is smaller than the height h2 of the outer end of the folded portion, and the difference h2-h1 is 5 to 15 mm. Since the difference h2-h1 between the height h1 of the outer end of the reinforcing cord filler and the height h2 of the outer end of the folded portion is defined in an optimum range, the bead durability is further improved.

  As described above, the heavy duty pneumatic tire of the present invention is excellent in bead durability and can be used for a long time.

It is sectional drawing which shows one Embodiment of the pneumatic tire for heavy loads of this invention. It is an enlarged view of the bead part of FIG. It is sectional drawing which shows the process of forming a carcass base | substrate.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a heavy duty pneumatic tire 1 in a normal state of the present embodiment. The “normal state” is a no-load state in which the heavy-duty pneumatic tire 1 is assembled on a normal rim (not shown) and filled with a normal internal pressure. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values measured in a normal state.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  The “regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA, and “TIRE LOAD” for TRA. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  As shown in FIG. 1, the heavy duty pneumatic tire 1 of the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4.

  In the present embodiment, the carcass 6 is formed from one carcass ply 6A. The carcass ply 6A is a carcass cord layer and includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the main body portion 6a and around the bead core 5 in the tire axial direction. And a folded portion 6b folded from the inside to the outside.

  A steel cord is preferably used for the carcass cord. The carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator C, for example.

  In a preferred embodiment, the height h2 of the outer end 6be of the folded portion 6b from the bead base line BL is, for example, 5% to 20% of the tire cross-section height H in order to exhibit the desired bead portion rigidity as a heavy load tire. Degree, more preferably 10% to 20%.

  FIG. 2 is an enlarged view of the bead portion 4 of FIG. As shown in FIG. 2, the bead portion 4 of this embodiment is provided with a reinforcing cord filler 7 arranged along the carcass ply 6A.

  The reinforcing cord filler 7 includes, for example, one cord ply in which steel cords are arranged in parallel. The reinforcing cord filler 7 of the present embodiment is formed in a substantially U-shaped cross section so as to wrap the bead core 5. More specifically, the reinforcing cord filler 7 includes an inner winding portion 7a extending in the tire radial direction along the tire axial direction inner side of the main body portion 6a of the carcass ply 6A, and a tire shaft of the folded portion 6b of the carcass ply 6A. And an outer winding portion 7b extending in the tire radial direction along the outer side in the direction. Such a reinforcing cord filler 7 reduces the bending distortion of the bead portion 4 to the outer side in the tire axial direction when the tire is loaded under load, and improves bead durability.

  The height h1 of the outer end 7be of the winding portion 7b outside the reinforcing cord filler 7 from the bead base line BL is smaller than the height h2 of the outer end 6be of the folded portion 6b of the carcass ply 6A. This helps to reduce the weight of the tire and to prevent the concentration of strain on the outer end of the outer winding portion 7b.

  The difference h2-h1 between the height h1 of the outer end 7be of the reinforcing cord filler 7 and the height h2 of the outer end 6be of the carcass ply 6A is preferably 5 to 15 mm. If the height difference h2−h1 is smaller than 5 mm, the outer end 7be and the outer end 6be are close to each other to form a large rigidity step, and there is a possibility that distortion concentrates on the outer end 7be and rubber peeling or the like occurs. Conversely, if the height difference h2-h1 is greater than 15 mm, the effect of reducing the distortion of the bead portion is insufficient, and as a result, the bead durability may be reduced. In a particularly preferred embodiment, the height difference h2-h1 is set to 7 to 13 mm.

  An insulation rubber 8 is provided between the folded portion 6 b of the carcass ply 6 </ b> A and the winding portion 7 b outside the reinforcing cord filler 7. The height h4 of the inner end 8i of the insulation rubber 8 from the bead base line BL is smaller than the height h1 of the outer end 7be of the reinforcing cord filler 7. The inner end 8i of the insulation rubber 8 of the present embodiment is tapered toward the inner side in the tire radial direction. Such an insulation rubber 8 increases the distance between cords between the folded portion 6b of the carcass ply 6A and the winding portion 7b outside the reinforcing cord filler 7 toward the outer side in the tire radial direction, and damage due to contact between the cords. Can be reliably prevented, and the durability of the bead portion can be further improved.

  The difference h1-h4 between the height h4 of the inner end 8i of the insulation rubber 8 and the height h1 of the outer end 7be of the reinforcing cord filler 7 is preferably 10 to 15 mm. If the height difference h1-h4 is smaller than 10 mm, there is a possibility that the effect of relaxing the strain between the folded portion 6b and the reinforcing cord filler 7 cannot be obtained sufficiently. On the contrary, if the height difference h1-h4 is larger than 15 mm, the rubber volume between the folded portion 6b and the reinforcing cord filler 7 becomes large, and there is a possibility that defects on the bead surface occur.

  The insulation rubber 8 is made of, for example, a soft rubber having a rubber hardness of 50 to 65 degrees. Such an insulation rubber 8 can reliably relieve and absorb the distortion generated between the turning portion 6b during traveling and the outer winding portion 7b. In the present specification, the rubber hardness is a hardness according to durometer type A in an environment of 23 ° C. according to JIS-K6253.

  In a preferred embodiment, the height h3 of the outer end 8o of the insulation rubber 8 from the bead base line BL is greater than the height h2 of the outer end 6be of the folded portion 6b. Such an insulation rubber 8 can cover the outer end 6be of the folded portion 6b, and as a result, the occurrence of cracks and the like near the outer end 6be can be suppressed. In order to exhibit such an action more reliably, the difference h3-h2 between the height h3 of the outer end 8o of the insulation rubber 8 and the height h2 of the outer end 6be of the folded portion 6b is 5 to 10 mm. It is desirable.

  Next, an example of the manufacturing method of the heavy duty pneumatic tire 1 of this embodiment is demonstrated based on FIG. The manufacturing method of the present embodiment includes a preparation process for preparing main tire configurations and a stratification process for winding these on a cylindrical forming drum D.

  In the preparation step, at least the reinforcing cord filler 7, the carcass ply 6A, and the insulation rubber 8 are prepared. The reinforcing cord filler 7 and the carcass ply 6A are each in the form of a sheet. The insulation rubber 8 has a substantially obtuse triangle in cross section. In addition to the bead core 5, examples of the constituent material include an inner liner and an insulation rubber (not shown).

  The cross section of the insulation rubber 8 includes an obtuse angle apex 8a, an obtuse angle apex 8a extending from the obtuse angle apex 8a, a long side 8c extending from the obtuse angle apex 8a, and an obtuse angle apex 8a opposite side 8d. The ratio of the short side 8b to the long side 8c is preferably 1: 1.5 to 3.0. The length of the opposite side 8d is preferably 25 to 35 mm. The maximum thickness t of the insulation rubber 8 (that is, the shortest distance between the obtuse angle vertex 8a and the opposite side 8d) is preferably 2 to 4 mm. The insulation rubber 8 having such a cross-sectional shape can greatly reduce molding defects in the vulcanization process and the like following the stratification process.

  In the stratification step, at least the reinforcing cord filler 7, the insulation rubber 8, and the carcass ply 6A are wound on the cylindrical forming drum D in this order. At this time, the insulation rubber 8 is wound with the apex 8a of the obtuse angle directed toward the reinforcing cord filler 7 side. As a more preferred embodiment, the long side 8 c of the insulation rubber 8 is wound so as to contact the reinforcing cord filler 7. By such a process, the obtuse angle apex 8a is positioned outside the outer end of the reinforcing cord filler 7 in the axial direction, and the obtuse angle apex 8a portion of the installation rubber 8 having a sufficient rubber volume in the vulcanization process. Thus, the outer end 7be of the reinforcing cord filler 7 is reliably covered. Note that the insulation rubber 8 may be preassembled to the reinforcing cord filler 7 in advance. Further, other constituent materials are also wound sequentially, and the cylindrical carcass base 9 is formed.

  The bead core 5 is fitted into the cylindrical carcass base 9 from the outside in the axial direction. Thereafter, according to the custom, the portion 9b outside the bead core 5 of the carcass base body 9 is folded back to the main portion 9a between the bead cores 5 and 5, and the main portion 9a is reduced while reducing the axial distance of the bead cores 5 and 5. Shaped toroidal. Also, a raw cover is formed by attaching a belt layer, tread rubber (not shown) or the like.

  As mentioned above, although the especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A heavy-duty pneumatic tire having the basic structure shown in FIG. 1 and having a size of 245 / 70R19.5 based on the specifications shown in Table 1 was prototyped and the performances thereof were compared.
The test method is as follows.

<Bead durability>
Each test tire was prototyped and was run on a drum testing machine at a speed of 20 km / h under the conditions of a rim having a size of 7.5 × 19.5, an internal pressure of 850 kPa, and a longitudinal load of 43.88 kN. And the running time until damage generate | occur | produces in a bead part was measured. The results are shown as an index with the traveling time of Comparative Example 1 as 100. It shows that it is excellent in durability, so that a numerical value is large.

<Poor molding>
In each example, 30 heavy-duty pneumatic tires were prototyped, and the presence of molding defects such as cracks in the vicinity of the bead portion was inspected with the naked eye of the observer. The evaluation is indicated by an index with the number of molding defects of Comparative Example 1 as 100. It shows that it is so favorable that a numerical value is large.
Test results and the like are shown in Table 1.

  As a result of the test, it was confirmed that the heavy duty pneumatic tires of the examples all improved the bead durability with respect to the comparative example. In addition, it was confirmed that the heavy duty pneumatic tires of the examples had suppressed molding defects, and as a result, the manufacturing cost was also reduced.

DESCRIPTION OF SYMBOLS 1 Heavy load pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 7 Reinforcement cord filler 8 Insulation rubber 9 Carcass base D Molding drum

Claims (4)

A heavy-duty pneumatic tire having a carcass extending from a tread portion to a bead portion through a sidewall portion,
The carcass includes a main body part that extends from the tread part through the sidewall part to the bead core of the bead part, and a folded part that is continuous from the inner side in the tire axial direction around the bead core and folded around the bead core. Including a carcass ply having,
The bead portion is provided with a reinforcing cord filler that extends at least on the outer side in the tire axial direction of the folded portion along the folded portion, and an insulation rubber provided between the folded portion and the reinforcing cord filler. And
The height h1 from the bead base line at the outer end of the reinforcing cord filler is smaller than the height h2 from the bead base line at the outer end of the folded portion, and the difference h2-h1 is 5 to 5. 15mm der is,
The height h3 from the bead base line of the outer end in the tire radial direction of the insulation rubber is larger than the height h2 of the outer end of the folded portion, and the difference h3-h2 is 5 to 10 mm. heavy duty pneumatic tire, characterized in that it. The height h4 from the bead base line of the inner end in the tire radial direction of the insulation rubber is smaller than the height h1 of the outer end of the reinforcing cord filler, and the difference h1-h4 is 10 to 10%. heavy duty pneumatic tire according to claim 1, wherein a 15 mm. A method for producing a heavy duty pneumatic tire according to claim 1 or 2 ,
Preparing the sheet-like reinforcing cord filler, the sheet-like carcass ply, and the insulation rubber having a substantially obtuse triangle in cross section; and
Including a stratification step of winding the reinforcing cord filler, the insulation rubber, and the carcass ply in a cylindrical molding drum in that order;
In the stratification step, the heavy-duty pneumatic tire manufacturing method is characterized by winding an obtuse angle apex of the insulation rubber toward the reinforcing cord filler side. The insulation rubber consists of two sides sandwiching the apex of the obtuse angle, a short side and a long side,
The method for manufacturing a heavy duty pneumatic tire according to claim 3 , wherein in the stratification step, the long side is brought into contact with the reinforcing cord filler.

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