JP2005178483A - Pneumatic tire and pneumatic tire manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire and a pneumatic tire manufacturing method capable of suppressing non-uniform slip between a bead and a carcass. <P>SOLUTION: In a single stage method, a small diameter drum is used. A side tread 4, an inner liner 5 and a carcass 6 are wound around the small diameter drum. A bead supporting part 8 is provided on the small diameter drum, and a bead core 7 is externally inserted facing the bead supporting part. The bead core 7 is then firmly held by the expanded bead supporting part 8. A raw tire between the bead cores 7 is expanded by an expansion drum 3 provided between the bead cores 7 to form an original shape of the tire. An auxiliary cord layer 9 is arranged between the inner liner 5 and the carcass 6. The auxiliary cord layer 9 is provided only at the position aside the bead core 7 in the tire meridian section (the inner direction of the tire in the figure) when the carcass 6 is expanded. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire and a method for manufacturing a pneumatic tire, and more particularly to a pneumatic tire and a method for manufacturing a pneumatic tire capable of suppressing slip of a carcass against a bead during a tire molding process.

  As one method for forming a pneumatic radial tire, single-stage forming using a small-diameter drum is known. This forming method is generally as follows. (1) A side tread, an inner liner, and a carcass are wound around a cylindrical drum, and a pair of beads are extrapolated thereon. (2) By expanding the diameter of the drum, the bead core is sandwiched and fixed together with the carcass etc. on the concave bead support portion arranged on the cylindrical drum. (3) The carcass is inflated by inflating (shaping) the inflating drum (blader) between the beads, and is combined with a separately prepared belt and tread rubber annular overhead ring. (4) Finally, the carcass and the side tread outside the bead are wound up to form a green tire.

  When the carcass (3) is expanded and deformed in the molding process, a pulling force acts on the cord constituting the carcass toward the center of the tire, thereby causing a slight slip between the carcass and the bead. Although the carcass is tightly clamped between the bead core and the inner liner, the amount of slip of this carcass depends on the tire circumference because the circumferential thickness is not uniform, such as the splice of the carcass and inner liner. It is not constant, and the length of the carcass cord between the pair of beads is varied. As a result, it was found that nonuniform rigidity in the tire circumferential direction was produced, and the uniformity was deteriorated.

  As a means for preventing such uneven slip between the carcass and the bead, an auxiliary cord layer made of a steel cord is provided on the inner side in the radial direction of the bead (lower part of the bead in the tire meridian section) and outside the carcass, Has been disclosed (for example, Patent Document 1).

By the way, the radial tire having the belt includes a type in which the left and right carcasses are discontinuous and discontinuous on the inner side in the radial direction of the belt. This carcass is commonly called a hollow carcass. If the carcass has a hollow structure, the rigidity of the crown portion decreases and the tire can be reduced in weight, which leads to an improvement in riding comfort and a reduction in road noise. This type of tire also has a problem that the molding process is basically the same as described above, and the carcass slips slightly during the expansion process. And it is known to cope with such a problem by providing a connection band that restrains the carcass cord in the circumferential direction at least at a portion corresponding to the inner peripheral surface of the bead core (for example, Patent Document 2).
JP 2002-99610 A JP 2001-260617 A

  However, at the time of technical vulcanization, the radially inner side of the bead (the lower part in the tire meridian section) is a place where the rubber flow is relatively large, and the auxiliary cord layer is easily deformed and unevenly displaced on the circumference. As a result, uniformity and rim fitting that can be adjusted in the raw tire are deteriorated. Further, in the case of the hollow carcass, the tension due to expansion is weak, and the closer to the bead, the smaller the action due to the tension is. Therefore, the arrangement of the carcass cords around the bead core tends to be disturbed. For this reason, similar to the above, there is a problem that uniformity (particularly RFV) is deteriorated and a failure due to carcass wrinkles occurs in the subsequent vulcanization process.

  Accordingly, the present invention has been made in view of the above, and is a pneumatic tire that is less susceptible to rubber flow during vulcanization and can suppress uneven slip of beads and carcass, and a method for manufacturing a pneumatic tire. The purpose is to provide.

  In order to achieve the above-described object, a pneumatic tire according to claim 1 includes at least one carcass integrated with a tread portion, a side portion, a bead portion, and a folded portion folded around the bead core. A pneumatic tire provided with an auxiliary cord layer on the outer surface of the carcass only at a position on the side of the bead core in the tire meridional section.

  In the pneumatic tire according to claim 2, a belt is disposed on the inner peripheral side of the tread, extends from the inner peripheral portion of the belt to the left and right bead cores, and is folded back from the inner side to the outer side of the bead core. Further, in the pneumatic tire having a hollow carcass, an auxiliary cord layer is provided on the outer surface of the hollow carcass only at a position on the side of the bead core in the tire meridional section.

  When the auxiliary cord layer is provided on the outer surface of the carcass, the carcass is firmly pressed by the bead support portion when the raw tire is formed in a single stage. Thereby, even if the carcass is pulled in the tire center direction, the carcass position can be sufficiently fixed, and uneven slip of the bead and the carcass can be suppressed. In addition, the rubber flow is not adversely affected during the vulcanization process after green tire molding.

  Further, in the pneumatic tire according to claim 3, in the pneumatic tire, the auxiliary cord layer is made of a steel cord or an organic fiber cord rubber covering material arranged at an angle of 10 to 70 degrees with respect to the tire circumferential direction. It is configured.

  As the cord angle is smaller, a higher frictional force can be obtained, but the cord layer tends not to follow the diameter of the drum during molding. Therefore, the angle is preferably set to 10 to 70 degrees. Moreover, a steel cord can obtain a higher frictional force as a material of the cord, but if the angle is small, it is difficult to follow the drum diameter expansion. For this reason, 20 to 60 degrees for steel cords and 10 to 40 degrees for organic fiber cords are desirable.

  In the pneumatic tire according to claim 4, in the pneumatic tire, the width of the auxiliary cord layer is 0.5 to 1.0 times the cross-sectional height of the bead core.

  The width h of the auxiliary layer is 0.5 to 1.0 times, preferably 0.8 to 1.0 times the bead core cross-sectional height H. If it is less than 0.5 times, the contact area with the carcass becomes small, so that it is difficult to obtain a sufficient restraining effect. This increases the ride comfort and causes a vulcanization failure due to air remaining in the raw tire.

  Further, in the pneumatic tire according to claim 5, in the pneumatic tire, the thickness of the auxiliary cord layer is 1.5 mm or less.

  If the auxiliary cord layer is too thick, a step may occur between the inner cord and the inner liner during molding, and a failure due to remaining air may occur. For this reason, in consideration of reducing the effect of the step while suppressing the slip of the carcass, the thickness is set to 1.5 mm or less, preferably 1.2 to 0.9 mm.

  In the pneumatic tire according to claim 6, in the pneumatic tire, the auxiliary cord layer is made of rubber harder than carcass coat rubber.

  By using hard rubber, it is possible to resist the tension pulled in the tire center direction. The hard rubber may be directly adhered to the carcass rubber or may be adhered via the coating rubber.

  According to a seventh aspect of the present invention, there is provided a method of manufacturing a pneumatic tire, wherein a side tread, an inner liner, and a carcass are wound around a cylindrical tire forming drum, and a pair of bead cores are placed on the drum, and the drum is mounted. By expanding the diameter, the bead core is sandwiched and fixed together with the carcass etc. on the concave bead support portion arranged on the drum, and the expansion of the expansion drum between the pair of beads expands the air to expand the carcass. In the tire manufacturing method, when the carcass is inflated, an auxiliary cord layer is disposed on the surface of the carcass only at a position on the side of the bead core in the meridian section of the tire.

  The pneumatic tire according to the present invention can surely suppress uneven slip of beads and carcass during the green tire molding process, and adversely affects the rubber flow during the subsequent vulcanization process. It will not reach. As a result, there is no failure in the vulcanization process, and the circumferential rigidity of the tire can be made uniform and the rim fitting property can be improved. Therefore, according to the present invention, uniformity that affects road noise and riding comfort can be improved (RFV can be reduced). In addition, uniformity can be improved in the hollow carcass structure having the characteristics of effectively reducing the tire mass and maintaining the operational stability. Moreover, according to the manufacturing method of the pneumatic tire concerning this invention, the above pneumatic tires can be manufactured easily.

  Below, the example of the pneumatic tire concerning the present invention is described in detail based on a drawing. Note that the present invention is not limited to the embodiments.

  1 is a cross-sectional view showing a pneumatic tire manufacturing apparatus according to Embodiment 1 of the present invention. FIG. 1 shows an apparatus 1 according to a single stage method for forming a green tire. Moreover, the figure is sectional drawing when the small diameter drum of the apparatus 1 is cut | disconnected in radial direction, and is a part concerning one side among the parts symmetrical with respect to a tire axis.

  In the single stage method, a small-diameter molding drum 2 is used. A side tread 4, an inner liner 5, and a carcass 6 are wound around the small diameter drum 2. Further, the small-diameter drum 2 is provided with a bead support portion 8, and a bead core 7 is extrapolated so as to face the portion. Thereafter, the bead core 7 is strongly sandwiched between the bead support portions 8 having an enlarged diameter. Then, the raw tire between the bead cores 7 is inflated by the expansion drum 3 provided between the bead cores 7, and the original form of the tire is formed.

  A portion surrounded by a square in FIG. 1 is an enlarged view of a portion surrounded by a dotted line in the upper part. As shown, an auxiliary cord layer 9 is disposed between the inner liner 5 and the carcass 6. The auxiliary cord layer 9 is provided only at a position on the side of the bead core 7 in the tire meridian section (in the tire inner direction) when the carcass 6 is inflated. If the inner liner 5 is not present or not in the illustrated position, the auxiliary cord layer 9 is provided on the outer surface of the carcass 6.

  FIG. 2 is a cross-sectional view illustrating a state in which the bead core is fitted to the bead support portion. When the diameter of the bead support portion is increased as described above, the bead core 7 sandwiches the side tread 4, the inner liner 5 and the carcass 6 with the bead support portion. At this time, the auxiliary cord layer 9 is disposed inside the bead core 7 and the carcass 6 is firmly pressed by the bead support portion. Thereby, even if the carcass 6 is pulled in the tire center direction, the carcass position can be sufficiently fixed, and uneven slip of the bead core 7 and the carcass 6 can be suppressed.

  Further, if the auxiliary cord layer 9 is provided at this position, the rubber flow flowing under the bead core 7 in the mold is not adversely affected in the vulcanization process after the green tire is molded. That is, when the raw tire is vulcanized, the lower part of the bead core 7 is a place where the rubber flow is relatively large, and the auxiliary cord layer is deformed and the carcass cord is shifted accordingly. In the present invention, this can be prevented. Further, in the present invention, since the auxiliary cord layer 9 is located between the inner liner 5 and the carcass 6, it is possible to prevent the splicing from occurring on the tire circumference.

  If there is an auxiliary cord layer that becomes a step under the bead core, the gauge changes, and the change has a great influence on the fitting performance. Therefore, when such an auxiliary cord layer is used, it is not easy to design the material and the gauge, but the present invention does not need to consider it. The auxiliary cord layer can be arranged on the inner side of the bead core, and at the same time, the auxiliary cord layer can also be arranged on the outer side of the bead core so as not to increase the mass.

  FIG. 3 is a cross-sectional view showing the position of the auxiliary cord layer after molding the tire, and the left half is an enlarged view of the vicinity of the right half bead core. As shown in the figure, the carcass 11 is integrated with a tread portion, a side portion, a bead portion, and a folded portion that is folded around the bead core 12. There may be a plurality of carcass plies.

  The auxiliary cord layer 13 is made of a rubber coating material of steel cord or organic fiber cord arranged at an angle of 10 to 70 degrees with respect to the tire circumferential direction. This is because the smaller the cord angle, the higher the frictional force can be obtained, but the cord layer tends to be unable to follow the diameter expansion of the drum during molding. Moreover, a steel cord can obtain a higher frictional force as a material of the cord, but if the angle is small, it is difficult to follow the drum diameter expansion. For this reason, it is desirable to set it at 20 to 60 degrees for steel cords and 10 to 40 degrees for organic fiber cords.

  The width h of the auxiliary cord layer 13 is 0.5 to 1.0 times, preferably 0.8 to 1.0 times the height H of the bead core 12. This is because if it is less than 0.5 times, the contact area with the carcass becomes small, and it becomes difficult to obtain a sufficient restraining effect. On the other hand, even if it is larger than 1.0 times, it is not necessary in terms of restraint effect, and conversely, the mass increases, causing a deterioration in ride comfort and causing vulcanization failure due to air remaining in the raw tire, etc. Because it becomes.

  The thickness of the auxiliary cord layer 13 is 1.5 mm or less, preferably 1.2 to 0.9 mm. If the thickness of the auxiliary cord layer is thick, a step is generated between the inner liner and the inner liner during molding, and a failure due to remaining air may occur. For this reason, it is preferable to make it into the said range in consideration of reducing the effect of the step while suppressing the slip of the carcass.

  Table 1 is a table showing results of experiments on the arrangement, material, width ratio h / H, thickness, and the like of the auxiliary cord layer according to the present invention. The evaluation of the experimental results was carcass slip amount, RFV of uniformity (UF), and riding comfort. RFV is expressed as an exponent, and the smaller the value, the better. The ride comfort is a sensory evaluation by a veteran monitor, and this is also expressed as an index. On the contrary, the larger the value, the better. In addition, the tire used for evaluation is a so-called summer tire of 215 / 45R17 size.

  As shown in the table, all of Experimental Examples 1 to 3 according to the present invention can greatly suppress the amount of carcass slip. In particular, in Examples 1 and 3 in which the auxiliary cord layer was steel and the thickness was 1.0 or 1.5 mm, the amount of carcass slip could be suppressed to 1/6 of the conventional example. Further, in Comparative Example 3, the auxiliary cord layer was placed under the bead, that is, the inside of the bead in the tire radial direction, so that the amount of slip of the carcass was suppressed, but it was found that the ride quality was lowered due to the positional relationship with the rim. It was.

  As described above, according to the pneumatic tire according to the present invention, it is difficult to be affected by the rubber flow at the time of vulcanization, and the non-uniform slip of the bead and the carcass can be surely suppressed. Uniformity can be improved and uniformity can be improved, and uniformity can be improved (RFV can be reduced). Thereby, riding comfort and road noise resistance can be improved.

  FIG. 4 is a cross-sectional view showing a pneumatic tire having a so-called hollow carcass. As described in the background art, a radial tire having a belt is called a so-called hollow carcass in which the left and right carcasses 21 are discontinuous and discontinuous on the inner side (inner peripheral side) in the radial direction of the belt. There are tires. For example, there is a tire in which the discontinuous width, that is, the hollow width Bw1 is 80% or more of the belt width Bw.

  In this type of tire, the molding process is basically the same as that of the conventional tire, and the carcass 21 slips slightly in the expansion process during molding. Accordingly, in a second embodiment of the present invention, a tire developed to solve such a problem will be described. The tire has an auxiliary cord layer 23 on the outer surface of the hollow carcass 21 only at a position on the side of the bead core 22 when viewed in the meridional section.

  The auxiliary cord layer 23 in this invention is basically the same as in the first embodiment, and is composed of a rubber coating material of steel cord or organic fiber cord arranged at an angle of 10 to 70 degrees with respect to the tire circumferential direction. Similarly, the width h of the auxiliary cord layer 23 is 0.5 to 1.0 times the bead core height H, and the thickness of the auxiliary cord layer 23 is 1.5 mm or less. The auxiliary cord layer 23 was made of rubber harder than the rubber that coats the carcass 21. This is because by using hard rubber, it is possible to strongly resist the tension pulled in the tire center direction. The hard rubber may be directly adhered to the carcass rubber or may be adhered via the coating rubber.

  Table 2 is a table showing the results of experiments on the carcass structure of the auxiliary cord layer according to the present invention, the presence / absence of the auxiliary layer, the position and the height. Evaluation was RFV, steering stability (referred to as steering stability) riding comfort, and road noise among mass and uniformity (UF). Each evaluation value is expressed as an index, and the performance shown by the magnitude of the numerical value is as shown in the lower right of the table. In addition, it experimented about the arrangement | positioning position of an auxiliary | assistant cord layer, when it is only the inner side of the bead in the tire meridian section (Experimental Examples 1 and 2) and when it is both inside and outside (Experimental Example 3). The tire size used for the evaluation was 195 / 60R15.

  As shown in the table, it was found that all of Experimental Examples 1 to 3 according to the present invention can greatly improve the uniformity. This is a result of the auxiliary cord layer uniformly pressing the carcass from the inside of the bead or from both the inside and the outside and suppressing the carcass slip. In addition, the hollow carcass structure originally made it possible to reduce the weight, improve the ride comfort, and improve the road noise without deteriorating the maneuverability. However, the present invention realizes further improvement of the ride comfort. The pneumatic tire according to the present invention did not adversely affect the rubber flow even in the vulcanization process after the tire molding, and there was no failure due to it.

  In this way, in the hollow carcass structure that can effectively reduce the tire mass, maintain the operational stability, and improve the riding comfort and road noise, the present invention can be applied to the carcass near the bead. It is possible to suppress the disorder of the code sequence and improve the uniformity that was a drawback.

  The pneumatic tire according to the present invention is produced as a tire for a general passenger car, etc., while considering the tire molding process and the vulcanization process, an auxiliary cord layer is disposed to suppress uneven slip of the carcass, It contributes to the improvement of uniformity. Moreover, the manufacturing method of the pneumatic tire concerning this invention is related with the manufacturing method of this pneumatic tire.

It is sectional drawing which shows the manufacturing apparatus of the pneumatic tire concerning Example 1. FIG. It is sectional drawing which shows the state which the bead core fitted to the bead support part. It is sectional drawing which shows the position of the auxiliary | assistant cord layer after tire shaping | molding. It is sectional drawing which shows the pneumatic tire which has what is called a hollow carcass.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus 2 Example 3 Expansion drum 4 Side tread 5 Inner liner 6, 11, 21 Carcass 7, 12 Bead core 8 Bead support part 9, 13, 23 Auxiliary cord layer

Claims (7)

In a pneumatic tire provided with at least one carcass that is integrated from the tread portion to the bead portion through the side portion and the folded portion around the bead core,
A pneumatic tire having an auxiliary cord layer on an outer surface of the carcass only at a position on a side of the bead core in a tire meridional section. In a pneumatic tire having a hollow carcass disposed on the inner peripheral side of the tread, extending from the inner peripheral portion of the belt to the left and right bead cores, and folded from the inside to the outside of the bead core and moored.
A pneumatic tire comprising an auxiliary cord layer on an outer surface of the hollow carcass only at a position on a side of the bead core in a tire meridional section.   3. The pneumatic cord according to claim 1, wherein the auxiliary cord layer is made of a rubber coating material of steel cord or organic fiber cord arranged at an angle of 10 to 70 degrees with respect to a tire circumferential direction. tire.   The pneumatic tire according to any one of claims 1 to 3, wherein a width of the auxiliary cord layer is 0.5 to 1.0 times a cross-sectional height of the bead core.   The pneumatic tire according to any one of claims 1 to 4, wherein a thickness of the auxiliary cord layer is 1.5 mm or less.   The pneumatic tire according to any one of claims 1 to 5, wherein the auxiliary cord layer is made of rubber harder than carcass coat rubber. A cylindrical tire molding drum is wound with a side tread, an inner liner, and a carcass, and a pair of bead cores are placed on the drum, and the diameter of the drum is increased to form a concave shape disposed on the drum. In the method of manufacturing a pneumatic tire in which the bead core is sandwiched and fixed together with the carcass and the like in a bead support portion, and the carcass is inflated by inflating an expansion drum between the pair of beads.
A method for manufacturing a pneumatic tire, comprising: arranging an auxiliary cord layer on the surface of the carcass only at a position on a side of the bead core in the meridian section of the tire when the carcass is inflated.

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