JP5425515B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a bead core formed in an annular shape by continuously winding one or more bead wires is embedded in the bead portion, and in particular, improving the durability of the bead portion of the pneumatic tire, The rim assembly property is also improved.

  In general, a bead core of a pneumatic tire has two important functions of enhancing fitting with a rim and ensuring airtightness and mooring a carcass. In recent years, especially in construction vehicle tires, the demand for heavy loads is increasing, and it is necessary to improve the function of the bead core for mooring the carcass and enhance the durability of the bead portion.

  Thus, attempts have been made to improve the durability of the bead portion of the pneumatic tire. For example, Patent Document 1 discloses a bead wire having a pair of acute corners and a pair of obtuse corners in a cross section in the tire width direction. There has been proposed a pneumatic tire that has a parallelogram cross section including a portion and defines the arrangement directions of the acute angle corner and the obtuse angle corner in the cross section in the tire width direction. In this pneumatic tire, the carcass is pulled out by increasing the rotational rigidity of the entire bead core by dispersing the rotational stress in the carcass pullout direction applied to the bead core when the air is filled, when a load is applied, or when it changes with time. In addition, it is possible to improve the durability of the bead wire by making the bead wire circumferentially uniform in the circumferential direction, thereby improving the durability of the bead wire.

JP 2008-254684 A

  However, the pneumatic tire described in Patent Document 1 has a bead wire having a parallelogram section in the tire width direction, although the rotational rigidity of the entire bead core is increased and the durability of the bead portion is greatly improved. Since the corners of the two abut each other and restrain each other when the rim is assembled, the rigidity of the bead core in the tire circumferential direction also increases when compared with a bead core constituted by a bead wire having a circular cross section in the tire width direction. Is inevitable. If the rigidity of the bead core in the tire circumferential direction is increased in this way, the bead core becomes difficult to deform in the tire circumferential direction, and it is difficult to get over the rim flange of the rim when assembling the pneumatic tire to the rim. The pneumatic tire of Patent Document 1 has been required to be further improved in terms of rim assembly.

  In addition, if the rigidity of the bead core in the tire circumferential direction is large, the fitting force and fitting pressure of the bead core with respect to the rim will vary in the tire circumferential position when the rim is assembled. There is a possibility that the fluctuation of the RFV (radial force variation) of the tire increases with the use of.

  Accordingly, it is an object of the present invention to solve these problems of the prior art, and its object is to significantly improve the durability of the bead portion by optimizing the cross-sectional shape and arrangement of the bead wire. Another object of the present invention is to provide a pneumatic tire that can improve the rim assembly property of the tire and improve the deformation amount of the RFV after the rim assembly to the minimum while improving the rim assembly property.

  In order to achieve the above object, the present invention provides a pneumatic tire in which a bead core formed in an annular shape by continuously winding one or more bead wires is embedded in a bead portion, wherein the bead wire has a cross section in the tire width direction. And a parallelogram section having a first acute angle corner and a second acute angle corner forming a pair of acute angle corners, and a first obtuse angle corner and a second obtuse angle corner forming a pair of obtuse angle corners. The first acute angle corner is on the outer side in the tire width direction of the second acute angle corner and on the inner side in the tire radial direction, and the first obtuse angle corner is on the inner side in the tire width direction of the first acute angle corner. The second obtuse angle portion is located on the inner side in the tire width direction of the first acute corner portion, and is located on the same line as the first acute corner portion in the tire radial direction or on the inner side thereof. And the bead wire is Characterized in that formed by shaping against the rim diameter D of the rim with a radius of curvature R in the range of less than 0.05 D 0.5 D.

  Here, the “standard rim” is a standard rim (or an application size defined in industrial standards, standards, etc. effective in regions where tires are manufactured, sold, or used, such as JATMA, TRA, ETRTO, etc. (or “Approved Rim”, “Recommend Rim”).

  Moreover, the curvature radius R of the brazing of the bead wire embedded in the pneumatic tire is specified by the following procedure. That is, after disassembling the tire and taking out the bead core so as not to damage the bead wire, the bead wire for two rounds is cut out from the end of the bead wire arranged on the outer side in the tire radial direction so as not to be damaged. Next, the cut-out bead wire is left on a flat surface, and the inner diameter of the annular body formed by the bead wire in a natural state is measured at eight positions evenly spaced on the circumference, and half of the average value is defined as the radius of curvature R.

  Furthermore, it is preferable that the adjacent bead wires are in contact with each other.

  Further, the bead wire has an angle formed between a side between the first acute angle corner and the second obtuse angle corner of the parallelogram cross section and a tire width direction in a range of 0 degrees to 25 degrees. Is preferred.

  Furthermore, it is preferable that each of the acute corner portions of the bead wire is chamfered. The “chamfering” referred to here includes not only a straight corner at a sharp corner, but also rounding.

  Furthermore, it is preferable that the bead core is focused and fixed by a metal band or a textile wound spirally in the extending direction of the bead core.

  Further, the bead core is configured by arranging a plurality of the bead wires in a plurality of times in the tire radial direction and arranged in parallel in the tire width direction, the winding start end of the same bead wire, The tire circumferential position is preferably different from the end.

  Furthermore, the bead core is configured by arranging a plurality of the bead wires wound in a plurality of times in a tire radial direction in parallel in the tire width direction, and is configured to arrange the winding start end and winding end of each bead wire. It is preferable that the positions in the tire circumferential direction are different from each other.

  Furthermore, it is preferable that the cross-sectional shape of the bead core in the tire width direction is a parallelogram or a rectangle.

  Furthermore, it is preferable to dispose a rubber member having a rubber hardness of 85 Hs or more between the bead core and the carcass and at least one of the bead core on the upper side in the tire radial direction. The term “rubber hardness” as used herein means the rubber hardness when measured at a test temperature of 23 ° C. using a durometer hardness / type A tester according to JIS K6253.

  In such a pneumatic tire, the cross section of the bead wire in the tire width direction is a parallelogram cross section, and the adjacent surface of the bead wire adjacent in the tire width direction is a direction in which stress acting in the direction of pulling out the carcass is easily transmitted. Therefore, the rotational stress applied to the bead core at the time of air filling, load application or change with time is dispersed, and the rotational rigidity of the bead core increases as a whole. When the stress is applied, the adjacent bead wires face each other in a direction that makes it difficult to push them upward or downward in the tire radial direction, so the bead core has a uniform tension distribution in the circumferential direction of the bead core as a whole. The durability of the bead part is dramatically improved.

  Further, since the rigidity of the bead wire in the tire circumferential direction is reduced by brazing the bead wire with a relatively small radius of curvature, the bead wire having a quadrilateral cross section parallel to the tire width direction is embedded in the bead portion in the circumferential direction. Even in a pneumatic tire that tends to have high rigidity, the force required for the rim assembly of the tire is reduced, so that it is possible to improve the rim assembly performance of the tire and, in turn, to reduce the RFV amount in the tire-rim assembly. .

It is sectional drawing which shows the tire width direction cross section of the bead part of the pneumatic tire of one Embodiment of this invention applied to the rim | limb. (A)-(c) is sectional drawing of the tire width direction which respectively showed the modification of the bead core to which the said embodiment was applied. It is explanatory drawing for demonstrating the influence which the inclination direction of a bead wire has on the transmissibility of stress. It is sectional drawing of the tire width direction of the bead wire of the tire according to this invention. (A) is a side view of the bead core of the tire according to the present invention, and (b) is a sectional view in the tire width direction of the bead core of the tire of the present invention. (A), (b) is a perspective view which shows the winding start end and winding end of a bead core of a tire according to the present invention, respectively. It is sectional drawing of the tire width direction of the bead part of the tire according to this invention. It is sectional drawing of the tire width direction of the bead part of the tire according to this invention.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a cross section in the tire width direction of a bead portion of a pneumatic tire (hereinafter referred to as “tire”) according to an embodiment of the present invention applied to a rim. FIG. It is sectional drawing which showed the modification of the bead core to which this is applied. In the figure, 1 is a bead portion, 2 is a bead core, 3 is a bead wire constituting the bead core 2, 4 is a carcass extending in a toroid shape between a pair of bead cores 1, and 5 is a rim.

  The tire according to this embodiment is provided with a plurality of layers of rubber-coated steel cords (not shown) that surround and laminate the outer periphery of the crown part of the carcass 4, which is used for reinforcing the bead part 1, the carcass 4, and the tread part (not shown). And a belt layer (not shown). The carcass 4 may be either a radial carcass or a bias carcass.

  As shown in FIG. 1, the bead core 2 is configured by stacking annular bead wires 3 arranged in eight rows in the tire width direction in a six-layered structure. In addition, the number of rows and the number of steps of the bead wires in the bead core 2 can be appropriately increased or decreased according to the performance required for the tire. The cross-sectional shape of the bead wire 3 in the tire width direction includes a first acute corner portion 7a and a second acute corner portion 7b that form a pair of acute corner portions 7, a first obtuse corner portion 9a that forms a pair of obtuse corner portions 9, The first acute angle corner portion 7a is the outer side in the tire width direction (left side in FIG. 1) of the second acute angle corner portion 7b and the inner side in the tire radial direction (see FIG. 1). The first obtuse corner portion 9a is located on the inner side in the tire width direction (right side in FIG. 1) of the first acute angle corner portion 7a and on the outer side in the tire radial direction (upward side in FIG. 1). Yes, the second obtuse corner 9b is on the inner side in the tire width direction of the first acute corner 7a, and is at the same position as or on the inner side of the first acute corner 7a in the tire radial direction.

  Further, as shown in FIGS. 1 and 2 (c), the bead wire 3 is such that the first acute corner 7a and the first obtuse corner 9a of the bead wire 3 vertically adjacent to each other in the tire radial direction are in contact with each other. Alternatively, they may be arranged in the tire width direction as shown in FIGS. 2 (a) and 2 (b).

  The carcass 4 is formed by, for example, arranging a ply made of an organic fiber cord in a radial arrangement or a bias arrangement so as to straddle a pair of bead cores 2 in a toroidal manner, and winding the ply around the bead cores 2 from the inside of the tire to the outside. The both ends of the bead core 2 are fixed.

  In general, in a pneumatic tire, a tension in the outer side in the tire radial direction is applied to the carcass 4 at the time of air filling, when a load is applied, or a change with time, and therefore, as shown in FIG. Arise. At this time, of the bead wires 3a and 3b adjacent to the left and right in the tire width direction, the right bead wire 3a attempts to move in the direction of arrow α, and the left bead wire 3b conversely attempts to move in the direction of arrow β. In the bead wire 3 of the pneumatic tire according to the invention, the adjacent surfaces S1 of the bead wires 3a and 3b are inclined in the direction in which the stress is transmitted to each other. The applied rotational stress is dispersed, and the rotational rigidity of the bead core 2 as a whole increases. Moreover, since the adjacent surface S1 faces the direction in which it is difficult to push the adjacent bead wire 3 upward or downward in the tire radial direction when the rotational stress in the direction of arrow A is applied, the bead core 2 as a whole is bead wire. The circumferential tension distribution of 3 is made uniform.

  Thus, according to the pneumatic tire of the present invention, it is possible to increase the rotational rigidity of the bead core 2 as a whole and suppress the carcass 4 from being pulled out. Furthermore, since the tension distribution in the circumferential direction of the bead wire 3 can be made uniform, the durability of the bead wire 3 can be improved. Therefore, the durability of the bead portion 1 can be greatly improved.

  As described above, the bead wire 3 has a quadrilateral cross section in the tire width direction, and the adjacent surfaces S1 of the bead wires 3 are inclined in a direction in which stress is transmitted to each other, thereby greatly improving the durability of the bead portion. On the other hand, the bead core 2 formed as an assembly of such bead wires 3 has the corner portions of the adjacent bead wires 3 in contact with each other, that is, 7b and 9a and 9b and 7a, in the rim assembly. Since they are constrained to each other, the rigidity of the bead core 2 in the tire circumferential direction increases, and it becomes difficult to get the bead core 2 over the rim flange of the rim 5.

  Therefore, in the pneumatic tire according to the present invention, the bead wire 3 having the above-described configuration is preliminarily 0.05D to less than 0.5D, preferably 0.2D to 0.4D with respect to the rim diameter D of the standard rim 5. Continuous brazing is performed with a radius of curvature R in the range. Thereby, since the rigidity in the tire circumferential direction of the bead core 2 composed of the bead wire 3 having a parallelogram cross section can be reduced, the force required for the tire rim assembly is reduced, and the fitting pressure of the bead core 2 to the rim 5 is consequently reduced. It becomes uniform in the circumferential direction, and the amount of RFV after rim assembly can be reduced.

  Here, the reason why the radius of curvature R is set to 0.05D or more is that it is difficult to make the radius of curvature R less than 0.05D, and the rigidity of the bead wire 3 is excessively lowered and the rim assembly property is improved. This is because the resultant pressure becomes too low and the amount of change in RFV after rim assembly increases. On the other hand, when the radius of curvature R is less than 0.5D, if it is 0.5D or more, the rigidity of the bead wire 3 is not sufficiently lowered, and the rim assembly property is not sufficiently improved. This is because the amount of change increases.

  In general, when a tire rim is assembled, it is necessary to expand the diameter of the bead portion 1 and set it on the bead seat portion of the rim 5. Since the directional rigidity is low, the diameter is expanded even with a relatively small force, so that the bead portion can be fitted (fit) uniformly on the circumference. Further, after the rim assembly, the bead core 2 tries to reduce the diameter by the action of the bead wire 3 having a radius of curvature R smaller than the rim diameter D, so that the fitting pressure of the bead portion 1 to the rim 5 is improved.

  Here, it is preferable that the adjacent bead wires 3 are in contact with each other. When a buffer member such as rubber is interposed between the adjacent bead wires 3, the buffer member creeps with time and is crushed to change the shape of the entire bead core. However, if the adjacent bead wires 3 are brought into direct contact with each other in this way, the change over time of the bead core 2 as a whole can be reduced as compared with the case where a buffer member is interposed. The disconnection can be suppressed and the distortion of the end portion of the carcass 4 can be reduced. In addition, when the adjacent bead wires 3 are brought into direct contact with each other, the rigidity in the tire circumferential direction of the bead core 2 is further increased. However, in the pneumatic tire according to the present invention, since the brazing is performed, the rim assembly property is It is secured.

  Further, as shown in FIGS. 2A to 2C, the bead wire 3 has a parallelogram cross-section, the side 10 between the first acute corner 7 a and the second obtuse corner 9 b and the tire width direction. The angle formed is preferably in the range of 0 ° to 25 °. In this way, when the bead core 3 is wound to form the bead core 2, a predetermined taper angle can be given to the bead core 2, and as a result, an appropriate taper angle can be given to the lower portion of the bead portion 1 that contacts the rim.

  FIG. 4 is a sectional view showing a section of another bead wire according to the present invention. As shown in FIG. 4, the bead wire 3 preferably has chamfered acute corners 7a and 7b. By doing so, the stress applied to the acute corners 7a and 7b when the rotational stress in the direction of arrow A (see FIG. 3A) is generated in the bead core 2 can be dispersed, and the bead core 2 and the carcass can be dispersed. Since the damage (crack) of the contact portion 4 can be prevented, the durability of the bead portion 1 can be further improved.

  FIG. 5A is a side view schematically showing a state in which the bead core according to the present invention is taken out from the tire, and FIG. 5B is a cross-sectional view showing a cross section in the tire width direction of the bead core 2 according to the present invention. . The bead core 2 is converged by a bead wire 3 by a metal strip 11 as shown in FIG. 5A or by a textile 13 wound spirally in the extending direction of the bead core 2 as shown in FIG. 5B. It is preferable to fix. By doing in this way, collapse of bead wire 3 at the time of vulcanization and running can be controlled. For example, a metal body 11 made of steel or an aluminum alloy can be suitably used. For the textile 13, for example, a fabric using an organic fiber yarn such as nylon, rayon, or polyester can be suitably employed. .

  The bead core 2 comprises a single bead wire 3 that has been brazed, spirally wound continuously in the circumferential direction while shifting the position in the tire width direction, and constitutes a single layer. It can be formed by forming a plurality of layers in a procedure. Alternatively, a plurality of bead wires 3 subjected to such brazing are arranged in parallel in the tire width direction, and simultaneously wound in the circumferential direction to form one layer, and a plurality of the same procedures are performed on this layer. It can also be formed by forming a layer.

  Here, it is preferable that the tire circumferential direction positions of the winding start end 15 and the winding end end 17 of the same bead wire 3 are different from each other as shown in FIG. In this way, the bead core 2 composed of a plurality of bead wires 3 can significantly reduce the time required for producing the bead core 2 as compared to the bead core 2 configured by sequentially winding a single bead wire 3 in the tire radial direction. . However, when the winding start end 15 and the winding end end 17 of the bead wire 3 are concentrated at one place on the circumference of the bead core 2, stress is easily concentrated on this step, leading to a decrease in fracture strength. In particular, the winding start end 15 is a fulcrum of bending stress. The bead portion 1 may be damaged. Therefore, by making the winding start end 15 and the winding end end 17 of the same bead wire 3 different at the tire circumferential position, the stress concentration can be reduced while improving the production efficiency of the bead core 2. Further, as shown in FIG. 5 (a), the angle θ at which the line segments connecting the winding start end 15 and the winding end end 17 and the center point C of the bead core 2 cross each other is 40 degrees or more. It is preferably within the range of 80 degrees or less, and particularly preferably 60 degrees. This is because when the angle θ is less than 40 degrees, the effect of reducing the stress concentration is not sufficient, and when it exceeds 80 degrees, the weight balance on the circumference of the bead core 2 is lowered and the tire uniformity deteriorates.

  6 (a) and 6 (b) are perspective views showing the winding start end and winding end end of the bead core according to the present invention, respectively, and a plurality of bead cores 2 are provided as shown in FIGS. 6 (a) and 6 (b). The bead wires 3 are wound in a stack in the tire radial direction and arranged in parallel in the tire width direction, and the tire circumferential direction of the winding start end 15 and the winding end end 17 of each bead wire 3 is configured. The positions are preferably different from one another. As described above, if the bead core 2 is composed of a plurality of bead wires 3, it is advantageous in terms of production efficiency. However, when the tire circumferential direction positions of the winding start end 15 and the winding end end 17 of each bead wire 3 are the same, that is, when these ends 15 and 17 are aligned in the tire width direction, stress is concentrated on these steps. This tends to cause a decrease in fracture strength and may become a fulcrum of stress and damage the bead portion 1. Therefore, by differentiating the ends 15 and 17 of each bead wire 3 in the circumferential position, stress concentration can be reduced while improving the production efficiency of the bead core 2.

  Furthermore, the cross-sectional shape of the bead core 2 in the tire width direction is preferably a parallelogram as shown in FIGS. 2B and 2C or a rectangle as shown in FIG. By doing in this way, it becomes the shape which is easy to shape as a section shape of the whole bead core.

  FIG. 7 is a cross-sectional view showing a cross section in the tire width direction of the bead core according to the present invention. As shown in FIG. 7, it is preferable to dispose a high hardness rubber 19 having a rubber hardness of 85 Hs or more between the bead core 2 and the carcass 4 and at least one of the bead core 2 on the upper side in the tire radial direction. In general, a rubber having a high rubber hardness has a smaller flow during vulcanization than a rubber having a low rubber hardness. Thus, the high hardness rubber 19 is disposed between the bead core 2 and the carcass 4 in this way, The flow of rubber around the bead core 2 can be reduced, and collapse of the bead core 2 can be suppressed. Further, by disposing the high-hardness rubber 19 on the upper side in the tire radial direction of the bead core 2, it is possible to suppress the falling of the load-bearing bead part 1 and to reduce the shear swell generated in the bead part 1. The durability of the bead portion 1 can be improved.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . For example, the carcass 4 that is wound around the bead core 2 from the inside of the tire to the outside may be further disposed so as to surround the bead core 2 as shown in FIG. The carcass 4 is further hardly pulled out, and the durability of the bead portion 1 can be further enhanced.

  Next, tires according to the present invention (Examples) and comparative tires (Comparative Examples) were prototyped and performance evaluations were performed, which will be described below.

  All of the tires used in the test are radial tires for truck buses having a tire size of 11R22.5.

  The tire of Example 1 is a tire having the structure shown in FIG. 1 in the bead portion 1, and the bead core 2 has a parallelogram cross section having a width of 2 mm, a height of 1.3 mm, an acute angle of 70 degrees, and an obtuse angle of 110 degrees. The nine metal bead wires 3 are arranged in parallel in the tire width direction in the direction shown in FIG. 1, wound in five layers in the tire radial direction, and focused and fixed by a metal band 11. In addition, this tire has a configuration in which both end portions of one layer of the carcass 4 are folded around the bead core 2 from the inside to the outside of the tire, and four belt layers are disposed on the outer periphery side of the carcass 4 in the tread portion. In addition, about structures other than the bead part 1, it follows a conventional pneumatic tire and description is abbreviate | omitted.

  Further, the bead wire 3 of the tire of Example 1 was previously brazed with a curvature radius R of 0.45 D with respect to the rim diameter D of the rim 5 in advance.

  The tire of Example 2 is configured in the same manner as the tire of Example 1 except that the radius of curvature R of the brazing applied to the bead wire 3 is 0.4D.

  The tire of Example 3 is configured in the same manner as the tire of Example 1 except that the radius of curvature R of the brazing applied to the bead wire 3 is 0.25D.

  The tire of Example 4 is configured in the same manner as the tire of Example 1 except that the radius of curvature R of the brazing applied to the bead wire 3 is 0.2D.

  In the conventional tire, a bead core 2 is formed using a round bare wire instead of the bead wire 3 (not shown). That is, the bead core 2 is made of the same metal as in Examples 1 to 4, and is arranged with nine 1.8 mm diameter round strand wires arranged in parallel in the tire width direction, and wound in five layers in the tire radial direction. Its cross-sectional shape is rectangular. Further, the bead wire is preliminarily brazed with a curvature radius R of 0.6 D with respect to the rim diameter D of the rim 5.

  In the tire of Comparative Example 1, the bead wire is previously brazed with a curvature radius R that is 0.55 D with respect to the rim diameter D of the rim 5. It is the same as a tire.

  In the tire of Comparative Example 2, the bead wire is previously brazed with a curvature radius R that is 0.04D with respect to the rim diameter D of the rim 5. It is the same as a tire.

  Each of these test tires was tested for durability of the bead portion, rim fit, rim slip, and air leakage by the following methods. The rim slip test and the air leak test were performed in order to evaluate the amount of change in RFV after the tire was assembled to the rim.

(Durability test)
In the durability test of the bead part, the tire is mounted on a rim of the same size 8.25, the room temperature is 45 degrees, an air pressure of 700 kPa (relative pressure) is applied, and an indoor drum tester is used. The tire was rolled at a speed of 60 km / h under the action of a load of 57 kN (180% of the normal load), and the running distance until the bead portion failed was measured. The results are shown in Table 1. In addition, the evaluation result of Table 1 is represented by the index | exponent which set the value of the tire of the prior art example to 100, and represents that durability is so high that a numerical value is large.

(Rim fit test)
Each of the test tires is mounted on a rim of size 8.25 to form a tire wheel, an internal pressure of 700 kPa (relative pressure) is applied to fit the rim and the tire, and then a bead of the tire wheel is used using a CT scanner. The part was observed, the gap between the rim and the bead part was measured, and the rim fit property was evaluated by the total value of the gaps at 10 places on the circumference. The evaluation results are shown in Table 1. In addition, the evaluation result of Table 1 is represented by the index | exponent which set the value of the tire of the prior art example to 100, and it is excellent in rim fitting property, so that a numerical value is small.

(Rim slip test)
When a load of 4.9 N is applied to the tire wheel placed on the flat plate, the flat plate pressed on the tread portion is slid in this state, and the bead portion slides on the rim. The force applied to the rim was measured, and the rim slip property was evaluated based on the measured value. The evaluation results are shown in Table 1. In addition, the evaluation result of Table 1 is represented by the index | exponent which set the value of the tire of the prior art example to 100, and represents that there are so few rim slips, so that a numerical value is small.

(Air leakage test)
The tire wheel was left with an internal pressure of 220 kPa applied, the internal pressure after 30 days was measured, and the air leakage was evaluated by the amount of decrease in the pressure. The evaluation results are shown in Table 1. In addition, the evaluation result of Table 1 is represented with the index | exponent which set the value of the tire of the prior art example to 100, and represents that there are few air leaks, so that a numerical value is small.

  From the results shown in Table 1, the tires of Examples 1 to 4 have the distance to failure dramatically increased as compared to the tires of the conventional example, while maintaining the rim slipperiness and air leakage performance equally. It can be seen that the rim assembly is greatly improved. Therefore, the tires of Examples 1 to 4 can improve the durability of the entire bead portion, and are excellent in overall fitting characteristics by improving the rim assembly property, and the amount of change in RFV after the rim assembly is improved. Can be minimized.

1: bead portion 2: bead core 3: bead wire 4: carcass 5: rim 7: acute corner 7a: first acute corner 7b: second acute corner 9: obtuse corner 9a: first obtuse corner 9b: first Two obtuse corners 10: Side 11: Metal band 13: Textile 15: Winding end 17: Winding end 19: High hardness rubber

Claims (9)

In a pneumatic tire in which a bead core formed in an annular shape by continuously winding one or more bead wires is embedded in a bead portion,
The bead wire includes a first acute angle corner and a second acute angle corner forming a pair of acute corners, and a first obtuse corner and a second obtuse angle corner forming a pair of obtuse corners in the tire width direction cross section. Having a parallelogram cross section having
The first acute angle corner is outside the tire width direction of the second acute angle corner and inside the tire radial direction, and the first obtuse angle corner is inside the tire width direction of the first acute angle corner. The second obtuse angle portion is located on the inner side in the tire width direction of the first acute angle corner portion, and is located on the same line as the first acute angle corner portion or on the inner side in the tire radial direction. As well as
The bead wire, air-filled tires ing been shaping in the range of less than 0.05 D 0.5 D relative to the rim diameter D of the standard rim radius of curvature R.   The pneumatic tire according to claim 1, wherein the adjacent bead wires are in contact with each other.   The bead wire has an angle formed between a side between the first acute angle corner and the second obtuse angle corner of the parallelogram section and a tire width direction in a range of 0 degrees to 25 degrees. The pneumatic tire according to 1 or 2.   The pneumatic tire according to any one of claims 1 to 3, wherein the bead wire is chamfered at each of the acute angle corners.   The pneumatic tire according to any one of claims 1 to 4, wherein the bead core is obtained by focusing and fixing the bead wire by a metal band or by a textile wound spirally in the extending direction of the bead core.   The bead core is configured by arranging a plurality of the bead wires wound in layers in the tire radial direction and arranged in parallel in the tire width direction, and the winding start end and winding end end of the same bead wire The pneumatic tire as described in any one of Claims 1-5 in which the tire circumferential direction position differs.   The bead core is configured by arranging a plurality of the bead wires wound in layers in the tire radial direction and arranged in parallel in the tire width direction, and the winding start end and the winding end end of each bead wire. The pneumatic tire according to any one of claims 1 to 6, wherein tire circumferential positions are different from each other.   The pneumatic tire according to any one of claims 1 to 7, wherein a cross-sectional shape of the bead core in the tire width direction is a parallelogram or a rectangle.   The pneumatic according to any one of claims 1 to 8, wherein a rubber member having a rubber hardness of 85 Hs or more is disposed between the bead core and the carcass and at least one of the bead core on the upper side in the tire radial direction. tire.

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