JP2014028569A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire improved in steering stability by expanding a rigidity difference between a tire inside portion and an outside portion.SOLUTION: In a pneumatic radial tire 1, each bead portion includes bead cores 13a and 23a and bead fillers 13b and 23b, and a carcass layer 5 includes a carcass body portion extending from a tire center line CL up to tire radial direction inside ends of the bead cores 13a and 23b and carcass folded-back portions 15b and 25b folded back at the tire radial direction inside ends of the bead cores 13a and 23a. A length Ca2 of an outside carcass periphery is longer than a length Ca1 of an inside carcass periphery. A length of the outside folded-back portion 25b is longer than that of the inside folded-back portion 15b. A height BH1 of the inside bead filler 13b is higher than a height BH2 of the outside bead filler 23b.

Description

  The present invention relates to a pneumatic radial tire, and more particularly, to a tire having high steering stability and cut resistance.

  For pneumatic radial tires (hereinafter referred to as “tires”), cut resistance, that is, strength against damage caused by rocks and rubble is one of the important performances. In particular, in emerging markets where the penetration rate of automobiles has been rising in recent years, there are many areas where roadways are not sufficiently developed, so tires with high cut resistance are required.

  Generally, a tire is disposed at a tread portion contacting a road surface, a pair of sidewall portions extending toward the tire radial center at both ends of the dread portion, and a tire radial inner end of the sidewall portion, and the tire is fixed to the rim. And a pair of bead portions. Further, the carcass layer that forms the skeleton of the tire extends from the tread portion to the sidewall portion and is folded back at the bead portion to terminate, thereby ensuring the strength of the tire. High cut resistance can be obtained by extending the folded portion of the carcass layer to the tread portion and forming an envelope structure sandwiched between the belt layer and the carcass layer that protects the carcass layer.

JP 2009-023567 A

  However, when the carcass layer has an envelope structure, although the cut resistance is improved, the manufacturing cost increases. The carcass layer has an envelope structure only at the outer part when the tire is mounted on the vehicle, and there is a method to improve cost while maintaining cut resistance, but the tire structure becomes uneven between the outside and inside, and steering stability Gets worse.

  Accordingly, an object of the present invention is to provide a tire that has a good balance of cut resistance, cost performance, and steering stability and can meet the demands in emerging markets.

  In order to solve the above problems, the present invention has the following features. The first feature of the present invention includes a tire inner portion (inner portion 11) positioned on the inner side of the tire center line (tire center line CL) and a tire outer portion (outer portion 21) positioned on the outer side when the vehicle is mounted. A pneumatic comprising a carcass layer (carcass layer 5) extending between an inner bead portion (inner bead portion 13) located in the tire inner portion and an outer bead portion (outer bead portion 23) located in the tire outer portion. A radial tire, wherein each of the inner and outer bead portions includes a bead core (13a, 23a) and a bead filler (13b, 23b), and the carcass layer extends radially inward of the bead core from the tire center line. The carcass main body portion (inner main body portion 15a, outer main body portion 25a) extending to the end and folded at the tire radial direction inner end of the bead core. A carcass folded portion (inner folded portion 15b, outer folded portion 25b), and the length of the carcass main body portion (outer carcass peripheral length Ca2) in the tire outer portion is the carcass main body portion in the tire inner portion. The length of the carcass folded portion in the tire outer portion is longer than the length of the carcass folded portion in the tire inner portion, and the bead filler in the inner bead portion is longer than the length of the inner bead portion. In summary, the height in the tire radial direction (height BH1) is higher than the height in the tire radial direction (height BH2) of the bead filler of the outer bead portion.

  According to this feature, an asymmetrical tire is obtained in which the length of the carcass periphery at the outer portion of the tire is longer than the length of the carcass periphery at the inner portion of the tire. In such an asymmetric tire, the rigidity of the outer portion of the tire having a long carcass peripheral length is smaller, and a difference in stiffness occurs between the inside and outside of the tire. In an asymmetrical tire, the vehicle turns smoothly by a lateral force called conicity acting from a tire outer portion having a low rigidity toward a tire inner portion having a high rigidity. In addition, even when traveling straight, the conicity generated in the opposite direction between the left and right wheels of the vehicle is offset, and steering stability is improved. Further, the contact area of the tread portion is increased at the outer portion of the tire, road surface contact pressure is dispersed, and uneven wear is suppressed.

  Further, since the folded portion of the carcass layer on the tire outer portion is long, the cut resistance of the tire outer portion can be ensured. Further, the manufacturing cost can be reduced as compared with the case where the folded portion is lengthened even in the inner portion of the tire. However, since the length of the folded portion of the carcass layer at the outer portion of the tire is longer than the inner portion of the tire, the rigidity of the outer portion of the tire is increased. Therefore, the difference in rigidity between the inside and outside of the tire due to the asymmetric shape is offset, and steering stability is reduced.

  However, in the tire according to the present invention, the rigidity of the tire inner portion is increased by the amount that the bead filler in the tire inner portion is higher than the bead filler in the tire outer portion. As a result, a difference in rigidity between the inside and outside of the tire is ensured, and steering stability is ensured.

  The tire center line refers to a bead line connecting the centers of the bead cores and a straight line perpendicular to the center point of the bead line in the cross section of the tire in the width direction. The center line in the width direction of the tread portion intersects the tire center line.

  The second feature of the present invention relates to the first feature of the present invention, and further includes a tread portion and a belt layer disposed along the tire radial direction outer side of the carcass layer in the tread portion. The gist is that the carcass folded-back portion in the outer portion extends inward in the tire radial direction of the belt layer.

  A third feature of the present invention is related to the first feature of the present invention, and is summarized in that the carcass folded-back portion in the tire inner portion terminates on the outer side in the tire radial direction from the position of the maximum tire width.

  A fourth feature of the present invention relates to the first feature of the present invention, and is summarized in that a tire radial height of the bead filler of the outer bead portion is 20 mm or less.

  A fifth feature of the present invention relates to the first feature of the present invention, wherein the position of the tire maximum width in the tire outer portion is located on the outer side in the tire radial direction than the position of the tire maximum width in the tire inner portion. The gist is to do.

  The tire according to the present invention has an effect of having a good balance of cut resistance, cost performance, and steering stability.

FIG. 1 is a cross-sectional view in the width direction of a pneumatic radial tire according to an embodiment of the present invention. FIG. 2 is a schematic view of a carcass layer and a bead portion of a pneumatic radial tire according to an embodiment of the present invention. FIG. 3 is a schematic view of a carcass layer and a bead portion of a pneumatic radial tire according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  FIG. 1 is a cross-sectional view in the width direction of a pneumatic radial tire according to an embodiment of the present invention. The tire 1 includes an inner portion 11 located on the inner side of the tire center line CL and an outer portion 21 located on the outer side when the vehicle is mounted. The tire 1 includes a tread portion 2, a pair of sidewall portions 14 and 24, a pair of bead portions 13 and 23, a carcass layer 5, and a belt layer 6. The tire center line CL is a bead line BL connecting the centers of the bead cores 13a and 23a and a straight line orthogonal to the center point of the bead line BL. The center in the width direction of the tread portion 2 intersects the tire center line CL. The belt layer 6 is disposed along the tire radial direction outer side of the carcass layer 5 in the tread portion 2 to reinforce the tread portion 2.

  The inner portion 11 of the tire 1 includes a sidewall portion 14 that extends inward in the tire radial direction from one end of the tread portion 2, and an inner bead portion 13 that is positioned at the inner end in the tire radial direction of the sidewall portion 14. The inner bead portion 13 includes an inner bead core 13a disposed at the inner end in the tire radial direction and an inner bead filler 13b disposed on the outer side in the tire radial direction of the inner bead core 13a and having a substantially triangular cross section. The carcass layer 5 includes a main body portion 15a from the tire center line CL to the inner end in the tire radial direction of the inner bead core 13a, and an inner folded portion 15b folded at the inner end in the tire radial direction of the inner bead core 13a. The length of the main body portion 15a is referred to as an inner carcass peripheral length Ca1.

  The outer portion 21 of the tire 1 includes a sidewall portion 24 that extends inward in the tire radial direction from the other end of the tread portion 2, and an outer bead portion 23 that is positioned at the inner end in the tire radial direction of the sidewall portion 24. The outer bead portion 23 includes an outer bead core 23a disposed at an inner end in the tire radial direction and an outer bead filler 23b disposed on the outer side in the tire radial direction of the outer bead core 23a and having a substantially triangular cross section. The carcass layer 5 includes a main body portion 25a from the tire center line CL to the inner end in the tire radial direction of the outer bead core 23a, and an outer folded portion 25b folded at the inner end in the tire radial direction of the outer bead core 23a. The length of the main body portion 25a is referred to as an outer carcass peripheral length Ca2.

  The outer carcass peripheral length Ca2 is longer than the inner carcass peripheral length Ca1. Therefore, the tire 1 has an asymmetric shape, and the rigidity of the inner part 11 is higher than the rigidity of the outer part 21. As a result, a lateral force called conicity works from the outer portion 21 having a low rigidity toward the inner portion 11 having a high rigidity, and the vehicle turns smoothly. In addition, even when traveling straight, the conicity generated in the opposite direction between the left and right wheels of the vehicle is offset, and steering stability is improved. Furthermore, the contact area of the tread portion 2 is increased in the outer portion 21, the road surface contact pressure is dispersed, and uneven wear is suppressed.

  FIG. 2 is a schematic view of the carcass layer 5 in the cross section in the tire width direction. The outer folded portion 25b of the carcass layer 5 is longer than the inner folded portion 15b. Thereby, the cut resistance of the outer portion 21 is ensured. In addition, the manufacturing cost can be reduced as compared with the case where the inner folded portion 15b has the same length as the outer folded portion 25b.

  As shown in FIG. 3, the outer folded portion 25 b preferably has an envelope structure that extends to the tread portion 2 and extends between the carcass layer 5 and the belt layer 6. By making the outer folded portion 25b into an envelope structure, cut resistance can be enhanced. The inner folded portion 15b is preferably terminated at a position higher than the position of the maximum tire width, that is, at the outer side in the tire radial direction and at the inner side in the tire radial direction from the tread portion. Thereby, compared with the case where both the inner folding | turning part 15b and the outer folding part 25b are made into an envelope structure, cost can be suppressed and sufficient rigidity can also be ensured also to the inner part 11. FIG. Note that the position of the maximum tire width in the outer portion 21 is located on the outer side in the tire radial direction than the position of the maximum tire width in the inner portion 11.

  Here, the maximum tire width means the maximum width of a tire when it is mounted on an applicable rim at the applicable size specified in the 2005 YEAR BOOK issued by JATMA and filled with the prescribed internal pressure. A regular rim is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA, "Design Rim" for TRA, or ETRTO Means "Measuring Rim". The normal internal pressure is the air pressure specified by the above standards for each tire. If it is JATMA, it is the maximum air pressure. If it is TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, ETRTO If so, it is "INFLATION PRESSURE". The regular load is the load specified by the above-mentioned standard for each tire. If it is JATMA, the maximum load capacity, if it is TRA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", ETRTO If so, it is "LOAD CAPACITY".

  FIG. 2 is a schematic view of the bead portions 13 and 23 in the cross section in the tire width direction. Here, the tire radial direction height BH1 of the inner bead filler 13b is higher than the tire radial direction height BH2 of the outer bead filler 23b. The rigidity of the inner part 11 is higher than that of the outer part 21 because the height BH1 of the inner bead filler is higher than the height BH2 of the outer bead filler 23b in the tire radial direction. Thereby, the rigidity difference between the inner part 11 and the outer part 21 is enlarged, and the steering stability is improved. The height BH2 of the outer bead filler 23b is preferably less than 35 mm, and more preferably 20 mm or less.

  That is, since the tire 1 has an asymmetric shape, the rigidity of the inner portion 11 is higher than that of the outer portion 21, and the steering stability is ensured. However, in order to ensure cut resistance, the outer folded portion 25b of the carcass layer 5 is made longer than the inner folded portion 15b, so that the rigidity of the outer portion 21 is enhanced, and the rigidity difference between the inner portion 11 and the outer portion 21 is increased. Is offset. Here, the rigidity of the inner portion 11 is increased by making the height BH1 of the inner bead filler 13b higher than the height BH2 of the outer bead filler. As a result, a difference in rigidity between the inner portion 11 and the outer portion 21 is ensured, and steering stability is also ensured.

  Next, in order to further clarify the effect of the present invention, test results performed using tires according to Examples 1 and 2 and Comparative Examples 1 to 4 below will be described. In addition, the data regarding the tires according to Examples 1 and 2 and Comparative Examples 1 to 4 were measured under the following conditions.

・ Tire size: 155 / 65R13
・ Vehicle type: Mini passenger car (Suzuki Wagon R)
・ Rim: 4.00Bx13
-Load: 2 passengers Here, the structure of the pneumatic radial tire which concerns on Examples 1, 2 and Comparative Examples 1-4 is demonstrated with reference to Table 1 and drawing.

  As shown in FIG. 1, the tire according to Example 1 is an asymmetrical tire in which the outer carcass peripheral length Ca2 is longer than the inner carcass peripheral length Ca1. As shown in FIG. 3, the outer folded portion 25 b has an envelope structure that extends to between the belt layer 6 and the carcass layer 5 of the tread portion 2. The inner folded portion 15b terminates at a position higher than the position of the tire maximum width, that is, the outer side in the tire radial direction and the inner side in the tire radial direction from the tread portion. The height BH1 of the inner bead filler 13b is higher than the height BH2 of the outer bead filler 23b.

  The tire according to Example 2 is substantially the same as the tire according to Example 1. However, the height BH2 of the outer bead filler 23b is lower than the outer bead filler of the tire according to the first embodiment, and the difference between BH1 and BH2 is larger than that of the first embodiment.

  The tire according to Comparative Example 1 is a symmetrical tire in which the inner carcass peripheral length and the outer carcass peripheral length are equal. The height of the bead filler is equal between the inner portion and the outer portion, and is equal to the height BH1 of the inner bead filler 13b in the tire according to the first embodiment. The folded portion of the carcass layer has an envelope structure in both the inner portion and the outer portion.

  The tire according to Comparative Example 2 is substantially the same as the tire according to Comparative Example 1. However, the folded portion of the carcass layer in the inner portion terminates at a position higher than the position of the maximum tire width, that is, the outer side in the tire radial direction and the inner side in the tire radial direction from the tread portion.

  The tire according to Comparative Example 3 is substantially the same as the tire according to Comparative Example 2. However, the tire has a symmetrical shape in which the inner carcass peripheral length and the outer carcass peripheral length are equal.

  The tire according to Comparative Example 4 is substantially the same as the tire according to Comparative Example 1. However, in both the inner portion and the outer portion, the folded portion of the carcass layer terminates at a position higher than the position of the maximum tire width, that is, the outer side in the tire radial direction and the inner side in the tire radial direction from the tread portion. .

  Table 1 shows the evaluation results of steering stability and pinch cut when the tires according to Examples 1 and 2 and Comparative Examples 1 to 4 are new. Steering stability evaluation is a sensory evaluation of steering stability by running of a test driver (internal pressure 220 kPa), and is evaluated with a maximum of 10 points. Evaluation with respect to the tire according to Comparative Example 1 is 5 points, and the higher the value, the higher the evaluation. The pinch cut was evaluated based on the failure rate when the cleat having a height of 60 cm was overcome (internal pressure 150 kPa). The larger the failure rate, the higher the cut resistance. Table 1 shows the manufacturing costs of the tires according to Examples 1 and 2 and Comparative Examples 1 to 4. The manufacturing cost of the tire according to Comparative Example 1 is set to 100, and the lower the value, the lower the cost.

  As a result of the test, as for the cut resistance, the tires according to Examples 1 and 2 and Comparative Examples 1 to 3 in which the outer portion of the carcass layer had an envelope structure recorded high numerical values. Among them, the tires according to Examples 1 and 2 and Comparative Examples 2 and 3 are manufactured at a lower manufacturing cost than the tire according to Comparative Example 1 because the length of the folded portion of the carcass layer in the inner part is shorter than the envelope structure. Is suppressed. In particular, since the outer bead filler of the tire according to Example 2 is smaller than that of other tires, the manufacturing cost is greatly suppressed.

  Regarding the steering stability, the tires according to Examples 1 and 2 obtained higher evaluation than the tire according to Comparative Example 1. This is because the tire according to Examples 1 and 2 has an asymmetric shape, and the difference in rigidity between the inner part and the outer part caused by the height of the inner bead filler being higher than that of the outer bead filler is It seems to have contributed to the improvement of sex. That is, in the tires of Examples 1 and 2, the difference in rigidity between the inner part and the outer part is offset by the length of the carcass layer folded part of the inner part shorter than the envelope structure. It was also found that the difference in rigidity was ensured by the height difference of the bead filler and the steering stability was sufficiently ensured. In particular, the tire according to Example 2 obtained the highest evaluation for the handling stability because the outer bead filler was smaller than the other tires.

  Therefore, in the tires according to Examples 1 and 2, the inner portion and the outer portion are preferably provided with an asymmetric shape, the length of the carcass layer folded portion, and the height difference of the bead filler, thereby providing cut resistance, cost performance, and It was found that the steering stability was well balanced.

  As described above, the present invention can be used for a pneumatic radial tire having a good balance of cut resistance, cost performance, and steering stability.

DESCRIPTION OF SYMBOLS 1 Pneumatic radial tire 2 Tread part 5 Carcass layer 6 Belt layer 13,23 Bead part 14,24 Side wall part Ca1, Ca2 Carcass peripheral length

Claims (5)

A tire inner portion positioned on the inner side of the tire center line and a tire outer portion positioned on the outer side when the vehicle is mounted; A pneumatic radial tire comprising a carcass layer extending through
Each of the inner and outer bead portions includes a bead core and a bead filler, and the carcass layer includes a carcass main body portion extending from the tire center line to a tire radial inner end of the bead core, and a tire radial inner end of the bead core. And the carcass folded portion folded at
The length of the carcass main body portion in the tire outer portion is longer than the length of the carcass main body portion in the tire inner portion,
The length of the carcass folded portion in the tire outer portion is longer than the length of the carcass folded portion in the tire inner portion,
The tire radial height of the bead filler in the inner bead portion is higher than the tire radial height of the bead filler in the outer bead portion. A tread portion, and a belt layer disposed along the tire radial direction outer side of the carcass layer in the tread portion,
The tire according to claim 1, wherein the carcass folded-back portion in the tire outer portion extends on the inner side in the tire radial direction of the belt layer.   2. The tire according to claim 1, wherein the carcass folded-back portion in the tire inner portion terminates at a tire radial direction outer side than a position of a tire maximum width.   The tire according to claim 1, wherein a height of the bead filler in the outer bead portion in a tire radial direction is 20 mm or less.   2. The tire according to claim 1, wherein the position of the tire maximum width in the tire outer portion is located on the outer side in the tire radial direction than the position of the tire maximum width of the tire inner portion.

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