JP5499921B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

  The present invention relates to a pneumatic tire having a bead core in a bead portion and a manufacturing method thereof, and more particularly to a pneumatic tire and a manufacturing method thereof capable of preventing torsion of a bead core and improving fitting properties. .

  In the bead portion of the pneumatic tire, a bead core formed by winding a plurality of circumferentially in the tire circumferential direction so that at least one bead wire is arranged in a plurality of rows and stages is arranged, and the bead core is made of a rubber composition on the outer peripheral side of the bead core. A bead filler is placed. The bead core plays a role of fixing the carcass layer mounted on the pair of bead portions and maintaining the internal air pressure, and preventing the tire from coming off the rim when the tire is punctured. On the other hand, if the tightening force by the bead core is too strong, the fitting pressure at the time of assembling the tire is increased, and the fitting property is deteriorated. Therefore, it is required to satisfy both the tightening force by the bead core and the fitting property of the tire (see, for example, Patent Documents 1 to 3).

  By the way, if the bead core is twisted (layer disorder) in the pneumatic tire, the tire becomes difficult to be evenly fitted to the rim when the rim is assembled, and the fitting property of the tire tends to deteriorate. Therefore, it is necessary to prevent the bead core from being twisted in order to improve the fitting property of the tire.

JP 2004-359196 A JP 2009-40202 A JP 2009-126269 A

  An object of the present invention is to provide a pneumatic tire that prevents twisting of a bead core and improves fitability, and a method for manufacturing the same.

  In order to achieve the above object, a pneumatic tire according to the present invention includes at least one carcass layer mounted between a pair of bead portions, and the carcass layer is disposed from the inside of the tire around a bead core disposed in each bead portion. In a pneumatic tire in which a bead filler made of a rubber composition is disposed on the outer peripheral side of the bead core, the carcass layer and the carcass layer on the both sides in the tire width direction of the bead buried body composed of the bead core and the bead filler. An auxiliary filler made of a rubber composition is disposed so as to be sandwiched between the bead buried body, the hardness of one auxiliary filler is lower than the hardness of the bead filler, and the hardness of the other auxiliary filler is It is characterized by being higher than the hardness.

In addition, the method for manufacturing a pneumatic tire according to the present invention for achieving the above object includes a bead core in which at least one carcass layer is mounted between a pair of bead portions, and the carcass layer is disposed in each bead portion. The bead filler made of a rubber composition is disposed on the outer periphery side of the bead core, and the carcass layers are disposed on both sides in the tire width direction of the bead buried body composed of the bead core and the bead filler. And an auxiliary filler made of a rubber composition so as to be sandwiched between the bead embedded body, the hardness of one auxiliary filler is lower than the hardness of the bead filler, and the hardness of the other auxiliary filler is A method of manufacturing a pneumatic tire having a higher hardness than the filler,
After molding an unvulcanized tire including the carcass layer, the bead core, the bead filler, and the auxiliary filler, the unvulcanized tire is put into a mold and the unvulcanized tire is pressed with a bladder from the inside. It is characterized by vulcanization.

  As a result of earnest research on the cause of twisting of the bead core, the present inventor found that the bladder bulges inside the tire during vulcanization, and a strong force acts on the bead when the tire is pressed against the mold by the bladder. As a result, the inventors discovered that the twist of the bead core occurs, and reached the present invention.

  That is, in the present invention, auxiliary fillers are arranged on both sides in the tire width direction of a bead embedded body composed of a bead core and a bead filler so as to be sandwiched between the carcass layer and the bead embedded body, and the hardness of one auxiliary filler is set to bead. Since the hardness is lower than the hardness of the filler, the force to deform the bead core during vulcanization can be absorbed by the low-hardness auxiliary filler. Thereby, twist of a bead core can be prevented and fitting nature of a pneumatic tire can be improved.

  However, when only the low-hardness auxiliary filler is added to the bead embedded body, the bead core is moved to the low-hardness auxiliary filler side at the time of vulcanization, and the fitting property is deteriorated. Therefore, by making the hardness of the other auxiliary filler higher than the hardness of the bead filler, it is possible to suppress the bead core from moving to the low-hardness auxiliary filler side, and to maintain its position appropriately.

  In the present invention, one auxiliary filler having a low hardness may be disposed on the outer side in the tire width direction from the bead embedded body, and the other auxiliary filler having a high hardness may be disposed on the inner side in the tire width direction from the bead embedded body. Alternatively, one auxiliary filler having a low hardness may be disposed on the inner side in the tire width direction from the bead embedded body, and the other auxiliary filler having a high hardness may be disposed on the outer side in the tire width direction from the bead embedded body. In either case, the fitting property of the pneumatic tire can be improved.

  The lower end of each auxiliary filler is preferably arranged at a position 30% to 100% of the height in the tire radial direction of the bead core from the upper end of the bead core toward the inner side in the tire radial direction. On the other hand, the upper end of each auxiliary filler is preferably disposed at a position 30% to 100% of the height in the tire radial direction of the bead filler from the upper end of the bead core toward the outer side in the tire radial direction. Thereby, the fitting property of a pneumatic tire can be improved effectively.

  It is preferable that the bead filler has a hardness of 70 to 90, the hardness of one auxiliary filler is 65 or less, and the hardness of the other auxiliary filler is 95 or more. Moreover, it is preferable that the maximum thickness of each auxiliary filler is 0.5 mm or more. Thereby, the fitting property of a pneumatic tire can be improved effectively.

  In the present invention, the hardness of the bead filler and auxiliary filler means the durometer hardness defined in JIS K6253, and is measured using a type A durometer.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which expands and shows the bead part of the pneumatic tire of FIG.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIG. 2 shows a bead portion thereof.

  In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the tire inner side to the outer side around the bead core 5 disposed in each bead portion 3. The bead core 5 is configured by winding a plurality of circumferentially in the tire circumferential direction so that at least one bead wire W is arranged in a plurality of rows and a plurality of stages. A bead filler 6 made of a rubber composition is disposed on the outer peripheral side of the bead core 5. And the bead embedding body 7 which consists of the bead core 5 and the bead filler 6 is enclosed by the main-body part and the folding | returning part of the carcass layer 4. FIG.

  On the other hand, a plurality of belt layers 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 8 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 8, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set, for example, in a range of 10 ° to 40 °.

  In the pneumatic tire described above, an auxiliary made of a rubber composition is sandwiched between the carcass layer 4 and the bead embedded body 7 on both sides in the tire width direction of the bead embedded body 7 composed of the bead core 5 and the bead filler 6. Fillers 6i and 6o are arranged. Here, the hardness of one auxiliary filler 6 i or 6 o is lower than the hardness of the bead filler 6, and the hardness of the other auxiliary filler 6 o or 6 i is higher than the hardness of the bead filler 6. In other words, the hardness of the bead filler 6 is Hc, the hardness of the auxiliary filler 6 i (inner filler) located on the inner side in the tire width direction from the bead filler 6 is Hi, and the auxiliary filler is located on the outer side in the tire width direction from the bead filler 6. When the hardness of 6o (outer filler) is Ho, the magnitude relationship between these hardnesses satisfies either one of the following formulas (1) and (2).

Ho <Hc <Hi (1)
Hi <Hc <Ho (2)

  When manufacturing the said pneumatic tire, the unvulcanized tire provided with the said structural member is shape | molded first. In the tire molding process, the auxiliary fillers 6i and 6o may be bonded to the carcass layer 4 and then the carcass layer 4 may be folded around the bead core 5 or the bead embedded body including the bead core 5 and the bead filler 6 may be used. Auxiliary fillers 6 i and 6 o may be bonded in advance to both sides of 7, and the carcass layer 4 may be folded around the bead core 5 in this state. Then, a desired pneumatic tire can be obtained by putting the molded unvulcanized tire into a mold and vulcanizing the unvulcanized tire while pressing it with a bladder from the inside.

  In the pneumatic tire, auxiliary fillers 6i and 6o are disposed between the carcass layer 4 and the bead embedded body 7 on both sides in the tire width direction of the bead embedded body 7 including the bead core 5 and the bead filler 6, respectively. Since the hardness of one of the auxiliary fillers 6i or 6o is lower than the hardness of the bead filler 6, the force to deform the bead core 5 during vulcanization can be absorbed by the low-hardness auxiliary filler 6i or 6o. . Thereby, the twist of bead core 5, ie, the layer disorder of bead wire W in bead core 5, can be prevented, and the fit nature of a pneumatic tire can be improved.

  Further, since the hardness of the other auxiliary filler 6o or 6i is higher than the hardness of the bead filler 6, the bead core 5 is restrained from moving to the low-hardness auxiliary filler 6i or 6o side during vulcanization, and embedded The position can be maintained properly. Therefore, even when the auxiliary filler 6i or 6o having a low hardness is added to the bead embedded body 7, it is possible to optimize the embedded position of the bead core 5 and ensure good fitting properties.

  Note that the hardness of the bead filler 6 and the auxiliary fillers 6i and 6o is the hardness after vulcanization, but there is a correlation between the hardness after vulcanization and the hardness before vulcanization. Therefore, by defining the magnitude relationship of the hardness after vulcanization, the above behavior is exhibited.

  As shown in FIG. 2, the lower end (inner end in the tire radial direction) of each of the auxiliary fillers 6 i and 6 o is the height of the bead core 5 in the tire radial direction from the upper end (outer end in the tire radial direction) of the bead core 5 toward the inner side in the tire radial direction. It is arranged in the range X1 of 30% to 100% of the height H5. Thereby, the fitting property of a pneumatic tire can be improved effectively. If the lower ends of the auxiliary fillers 6i and 6o do not reach the range X1, the effect of reducing the external force or the effect of retaining the embedded position cannot be obtained sufficiently. Further, even if the lower ends of the auxiliary fillers 6i and 6o are arranged at positions exceeding the range X1, further effects cannot be expected. The lower end of the high-hardness auxiliary filler 6o or 6i is preferably present on the inner side in the tire radial direction than the lower end of the low-hardness auxiliary filler 6i or 6o. Furthermore, the lower end of the high-hardness auxiliary filler 6o or 6i is preferably disposed in the range of 50% to 100% of the tire radial height H5 of the bead core 5 from the upper end of the bead core 5 toward the inner side in the tire radial direction.

  On the other hand, the upper end (outer end in the tire radial direction) of each auxiliary filler 6i, 6o is 30 of the tire radial direction height H6 of the bead filler 6 from the upper end (outer end in the tire radial direction) of the bead core 5 toward the outer side in the tire radial direction. It arrange | positions in the range X2 of% -100%. Thereby, the fitting property of a pneumatic tire can be improved effectively. If the upper ends of the auxiliary fillers 6i and 6o do not reach the range X2, the effect of reducing the external force or the effect of retaining the embedded position cannot be obtained sufficiently. Further, even if the upper ends of the auxiliary fillers 6i and 6o are arranged at positions exceeding the range X2, further effects cannot be expected. Note that the upper end of the high-hardness auxiliary filler 6o or 6i is preferably present on the outer side in the tire radial direction than the upper end of the low-hardness auxiliary filler 6i or 6o. Furthermore, the upper end of the high-hardness auxiliary filler 6o or 6i is preferably arranged in the range of 50% to 100% of the tire radial direction height H6 of the bead filler 6 from the upper end of the bead core 5 toward the outer side in the tire radial direction.

  The bead filler 6 has a hardness in the range of 70 to 90, the low hardness of the auxiliary filler 6i or 6o is 65 or less, more preferably in the range of 45 to 65, and the high hardness of the auxiliary filler 6o or 6i is 95. The above is good. The hardness range of the bead filler 6 satisfies the required performance such as steering stability and riding comfort. On the other hand, if the hardness of the auxiliary filler 6i or 6o having a low hardness is higher than 65, the effect of dispersing the force for twisting the bead core 5 decreases. However, when the hardness of the auxiliary filler 6i or 6o having a low hardness is lower than 45, the difference with respect to the bead filler 6 becomes too large. On the other hand, if the hardness of the auxiliary filler 6o or 6i having a high hardness is lower than 95, the effect of suppressing the movement of the bead core 5 decreases.

  The maximum thickness of each of the auxiliary fillers 6i and 6o is 0.5 mm or more, and more preferably in the range of 1.0 mm to 2.0 mm. This maximum thickness is a thickness measured in the tire width direction. If the maximum thickness of the low hardness auxiliary filler 6i or 6o is smaller than 0.5 mm, the effect of dispersing the force for twisting the bead core 5 decreases. For the auxiliary filler 6i or 6o having a low hardness, the maximum thickness can be reduced as the hardness decreases within the above range. If the maximum thickness of the high hardness auxiliary filler 6o or 6i is smaller than 0.5 mm, the effect of suppressing the movement of the bead core 5 is lowered. For the high hardness auxiliary filler 6o or 6i, the maximum thickness can be reduced as the hardness increases within the above range.

  With a tire size of 215 / 45R17, a carcass layer is mounted between a pair of bead parts, the carcass layer is folded from the inside of the tire to the outside around the bead core disposed in each bead part, and rubber is provided on the outer periphery of the bead core. In a pneumatic tire in which a bead filler (hardness: 80) made of the composition is arranged, it is sandwiched between the carcass layer and the bead embedded body on both sides in the tire width direction of the bead embedded body composed of the bead core and the bead filler. Table 1 shows the hardness and maximum thickness of the auxiliary filler (outer filler) on the outer side in the tire width direction, and the hardness and maximum thickness of the auxiliary filler (inner filler) on the inner side in the tire width direction. Tires of Examples 1 to 8 and Comparative Examples 1 and 2 set as described above were manufactured. For comparison, a tire of Conventional Example 1 that does not include an auxiliary filler was prepared.

  The lower end of each auxiliary filler was disposed at a position of 100% of the height in the tire radial direction of the bead core from the upper end of the bead core toward the inner side in the tire radial direction. On the other hand, the upper end of each auxiliary filler was disposed at a position 50% of the height of the bead filler in the tire radial direction from the upper end of the bead core toward the outer side in the tire radial direction.

  Each test tire is formed by molding an unvulcanized tire having the above-described components, and then charging the unvulcanized tire into a mold and pressing the unvulcanized tire from the inside with a bladder. Was obtained.

  About these test tires, the fitting property was evaluated by the following evaluation method, and the results are also shown in Table 1.

Mating property:
The fitting pressure at the time of assembling each test tire was measured. The fitting pressure was measured 10 times for each tire, and the average value was obtained. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. A larger index value means better fit.

  As can be seen from Table 1, the tires of Examples 1 to 8 were superior in fitting property as compared with Conventional Example 1. On the other hand, although the tires of Comparative Examples 1 and 2 have the same hardness of the auxiliary fillers on both sides, the effect of improving the fitting property was not recognized.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 6i Auxiliary filler (inner filler)
6o Auxiliary filler (outer filler)
7 Bead buried body 8 Belt layer

Claims (14)

  At least one carcass layer is mounted between a pair of bead portions, and the carcass layer is folded from the inside of the tire to the outside around the bead core disposed in each bead portion, and is formed of a rubber composition on the outer peripheral side of the bead core. In the pneumatic tire in which the bead filler is arranged, from the rubber composition so as to be sandwiched between the carcass layer and the bead embedded body on both sides in the tire width direction of the bead embedded body composed of the bead core and the bead filler, respectively. The pneumatic tire is characterized in that an auxiliary filler is arranged, the hardness of one auxiliary filler is lower than the hardness of the bead filler, and the hardness of the other auxiliary filler is higher than the hardness of the bead filler.   The said one auxiliary filler is arrange | positioned in the tire width direction outer side rather than the said bead embedding body, and said other auxiliary filler is arrange | positioned inside the bead embedding body in the tire width direction. Pneumatic tire.   The said one auxiliary filler is arrange | positioned inside a tire width direction rather than the said bead buried body, and said other auxiliary filler is arrange | positioned outside the said bead buried body in the tire width direction. Pneumatic tire.   The lower end of each auxiliary filler is arranged at a position of 30% to 100% of the height in the tire radial direction of the bead core from the upper end of the bead core toward the inner side in the tire radial direction. The pneumatic tire according to Crab.   The upper end of each auxiliary filler is arranged at a position of 30% to 100% of the height in the tire radial direction of the bead filler from the upper end of the bead core toward the outer side in the tire radial direction. The pneumatic tire according to any one of the above.   The hardness of the bead filler is 70 to 90, the hardness of the one auxiliary filler is 65 or less, and the hardness of the other auxiliary filler is 95 or more. Pneumatic tire described in 2.   The pneumatic tire according to claim 1, wherein the maximum thickness of each auxiliary filler is 0.5 mm or more. At least one carcass layer is mounted between a pair of bead portions, the carcass layer is folded from the inside of the tire to the outside around the bead cores arranged in each bead portion, and the rubber composition is formed on the outer peripheral side of the bead core Auxiliary filler comprising a rubber composition so that a bead filler is disposed and sandwiched between the carcass layer and the bead embedded body on both sides in the tire width direction of the bead embedded body composed of the bead core and the bead filler. In which the hardness of one auxiliary filler is lower than the hardness of the bead filler, and the hardness of the other auxiliary filler is higher than the hardness of the bead filler.
After molding an unvulcanized tire including the carcass layer, the bead core, the bead filler, and the auxiliary filler, the unvulcanized tire is put into a mold and the unvulcanized tire is pressed with a bladder from the inside. A method for producing a pneumatic tire, characterized by vulcanization while vulcanizing.   The said one auxiliary filler is arrange | positioned in the tire width direction outer side from the said bead buried body, and said other auxiliary filler is arrange | positioned in the tire width direction inner side from the said bead buried body. A method of manufacturing a pneumatic tire.   The said one auxiliary filler is arrange | positioned inside a tire width direction rather than the said bead buried body, and said other auxiliary filler is arrange | positioned outside the said bead buried body in the tire width direction. A method of manufacturing a pneumatic tire.   The lower end of each auxiliary filler is disposed at a position 30% to 100% of the height in the tire radial direction of the bead core from the upper end of the bead core toward the inner side in the tire radial direction. A method for producing a pneumatic tire according to claim 1.   The upper end of each auxiliary filler is arranged at a position 30% to 100% of the height in the tire radial direction of the bead filler from the upper end of the bead core toward the outer side in the tire radial direction. The manufacturing method of the pneumatic tire in any one.   The hardness of the bead filler is 70 to 90, the hardness of the one auxiliary filler is 65 or less, and the hardness of the other auxiliary filler is 95 or more, 13. The manufacturing method of the pneumatic tire of description.   The maximum thickness of each auxiliary filler is 0.5 mm or more, The manufacturing method of the pneumatic tire in any one of Claims 8-13 characterized by the above-mentioned.

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