JP4530264B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire including a pair of bead portions and sidewall portions, a tread portion disposed between the sidewall portions, and a carcass ply spanned between the bead portions.

  Generally, a pneumatic radial tire includes a pair of bead portions, sidewall portions extending outward in the tire radial direction from the bead portions, and a tread portion disposed between the sidewall portions. Between the bead portions, at least one carcass ply made of ply cords arranged at an angle of approximately 90 ° with respect to the tire equator line is bridged to form a carcass layer forming a tire skeleton.

  Usually, the arrangement pitch of the ply cords constituting the carcass ply is set uniformly in the tire circumferential direction, and the uniformity of the tire is ensured in the green state before vulcanization. However, after vulcanization, a plurality of tire blocks of different sizes are arranged in the tire circumferential direction based on the tread pattern, and there is a difference in stiffness in the tire circumferential direction due to the variation in rigidity of each tire block. It was. Therefore, there is a problem that the uniformity and riding comfort performance of the tire deteriorates.

  In particular, as disclosed in the following Patent Document 1, in recent years, as a noise countermeasure, a pitch variation in which a tire block group in which the circumferential direction length of each tire block is changed is periodically formed is introduced and specified from road surface collision sound. In this case, the wear pitch fluctuates periodically according to the rigidity variation of each tire block constituting the tire block group, as shown in FIG. Polygonal wear occurred.

Patent Document 2 below proposes a pneumatic tire that reduces noise by changing the ply cord arrangement pitch in the tire circumferential direction. In Patent Document 3 below, ply cord arrangement is caused by a problem in the manufacturing method. It is disclosed that the pitch varies in the tire circumferential direction. However, in any case, variation in rigidity between tire blocks is not suppressed, and polygonal wear may occur in a pitch variation type tread pattern.
JP 2002-362112 A Japanese Patent Laid-Open No. 7-1913 JP 2001-171310 A

  Accordingly, an object of the present invention is to provide a pneumatic radial tire that is excellent in tire uniformity and riding comfort performance and can suppress occurrence of polygonal wear.

The above object can be achieved by the present invention as described below. That is, the pneumatic radial tire of the present invention includes a pair of bead portions, a sidewall portion extending outward in the tire radial direction from the bead portion, a tread portion connected to an outer peripheral side end of each of the sidewall portions, a tire A pneumatic radial tire comprising a carcass layer in which a carcass ply made of a ply cord extending at an angle of approximately 90 ° with respect to an equator line is bridged between the bead parts, and the tread part When the total length of the ply cords surrounded by the outline of the tire block projected on the inner peripheral side toward the carcass ply per area of the tire block formed in the tire block is set as the driving density of the tire block, a tire block group arranged in the tire circumferential direction, the sub-crossing the main groove and its main grooves along the tire circumferential direction Largest area only is divided, the implantation density of the tire block of the minimum area included in the tire block group composed of mutually the plurality of the tire block is not connected in the tire circumferential direction and the tire width direction, with its tire blocks in the The tire block has a driving density larger than that of the tire block.

  According to the pneumatic radial tire according to the present invention, the driving density of the tire block with the smallest area of the tire block group arranged in the tire circumferential direction is set to be higher than the driving density of the tire block with the largest area of the tire block group. By making it large, the dispersion | variation in the rigidity of the tire block in a tire circumferential direction is improved, and a uniformity and riding comfort performance become favorable. Further, by improving the variation in the rigidity of the tire block, a difference in wear amount for each tire block is reduced, and the occurrence of polygonal wear can be suppressed even in the case of a pitch variation type tread pattern.

  In the above, it is preferable that the driving density of the tire block is increased as the area of each tire block constituting the tire block group arranged in the tire circumferential direction is smaller.

  The smaller the area of each tire block that constitutes the tire block group arranged in the tire circumferential direction, the greater the driving density of the tire block, thereby improving the variation in the rigidity of the tire block in the tire circumferential direction more effectively. be able to. As a result, it is possible to more effectively enhance the polygonal wear resistance while improving the tire uniformity and riding comfort performance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view showing an example of a pneumatic radial tire. The pneumatic radial tire shown in FIG. 1 includes a bead portion 1 in which a bead 1a and a bead filler 1b, which are converging bodies of bead wires, are disposed, and a sidewall portion 2 that extends outward from the pair of bead portions 1 in the tire radial direction. And a tread portion 3 connected to each outer peripheral side end of the sidewall portion 2. Various tread patterns are formed on the tread surface 8 in the tread portion 3 according to required tire performance and use conditions.

  The carcass layer 4 is composed of at least one carcass ply made of a ply cord extending at an angle of approximately 90 ° with respect to the tire equator line C, and is disposed so as to be bridged between the pair of bead portions 1. . As the ply cord, organic fibers such as steel, polyester, rayon, nylon, and aramid are used. These materials are usually subjected to surface treatment, adhesion treatment or the like in order to improve adhesion to rubber. The above structure is the same as a general tire, and the present invention can be applied to any tire having the structure.

  An inner liner layer 5 is disposed on the inner peripheral side of the carcass layer 4 to maintain air pressure. Further, on the outer peripheral side of the carcass layer 4, a belt layer 7 composed of two belt plies laminated on the inside and outside is arranged to reinforce by the effect. Each belt ply is constituted by a steel cord extending inclined at an angle of about 20 ° with respect to the tire equator line C, and the steel cords are arranged so as to cross each other in opposite directions between the plies. The belt ply is not limited to one made of a steel cord, and may be made of an organic fiber such as polyester, rayon, nylon, or aramid. Further, a belt reinforcing layer may be appropriately disposed on the outer peripheral side of the belt layer 7.

  FIG. 2 is a half plan view showing an example of a tread pattern formed on the tread surface. Such a tread pattern includes two linear main grooves 13 along the tire circumferential direction, sub-grooves 14 obliquely crossing the main grooves 13, and a plurality of tire blocks 6 (hereinafter simply referred to as blocks 6). Is omitted). In the present embodiment, the pattern is formed symmetrically with respect to the tire equator line C and is formed continuously in the tire circumferential direction.

  The plurality of blocks 6 formed on the tread surface 8 can be considered as a plurality of tire block groups (hereinafter simply referred to as block groups) arranged in the tire circumferential direction. For example, when the tread pattern of FIG. 2 is divided by the main groove 13, it can be considered that the block groups 10, 11, and 12 are provided. Here, FIG. 2 is an example of a pitch variation type tread pattern in which the circumferential length of the block is changed. Each block group 10 to 12 has a longer circumferential length as it is located in the lower part of FIG. Is also composed of a plurality of large blocks 6.

  FIG. 3 is a plan view when the contour of each block 6 shown in FIG. 2 is projected onto the carcass ply (carcass layer 4) disposed on the inner peripheral side thereof. Here, the total length of the ply cord 9 surrounded by the outline 16 of the block 6 per area of the block 6 is defined as the driving density of the block 6. That is, in the example of FIG. 4, when the area of the block 6 is S and the lengths of the ply cords 9 surrounded by the outline 16 of the block 6 are L1 to L6, respectively, the driving density of the block 6 is (L1 + L2 + L3 + L4 + L5 + L6) / S. Note that the ply cords 9 in the figure are conceptually described, and the actual arrangement pitch becomes denser.

  In this embodiment, as shown in FIG. 3, the arrangement pitch of the ply cords 9 constituting the carcass ply is varied in the tire circumferential direction, and becomes denser as it is located in the upper part of FIG. 3. The driving density of the block 6a having the minimum area included in the block group 10 is larger than the driving density of the block 6e having the maximum area. As a result, the rigidity of the block 6a is relatively high and the block rigidity in the tire circumferential direction is increased. Variation of the is improved. Further, in the present embodiment, the driving density from the block 6a to the block 6e is sequentially increased, and the variation in the block rigidity in the tire circumferential direction can be improved more effectively.

  Here, it is preferable that the arrangement pitch of the ply cords 9 surrounded by the outline 16 of one block 6 is uniform without changing. Thereby, generation | occurrence | production of the rigidity difference in the area | region of the block 6 can be suppressed. The present invention is not limited to a specific tread pattern as long as the blocks 6 are arranged in the tire circumferential direction, and the shape of the blocks 6 is not limited. The tread pattern may be a rib / block pattern in which blocks and ribs are mixed.

  The pneumatic radial tire described above can be manufactured by a conventionally known method except that the driving density of the blocks 6 is formed so as to satisfy the above-described relationship. The driving density of the block 6 is adjusted by forming a carcass ply in which the arrangement pitch of the ply cords 9 is changed in advance on the basis of the tread pattern, and arranging the arrangement on the tread surface 8 of the tire formed using the carcass ply. A tread pattern may be formed at a predetermined position determined in relation to the pitch.

  The carcass ply in which the arrangement pitch of the ply cords 9 is changed is formed, for example, by using a grooved roll in which the arrangement pitch of the grooves through which the cord passes is changed when the cord is rubberized by a calendar. be able to. The carcass ply can also be formed by using, for example, an apparatus disclosed in JP-A-2002-144446. According to the apparatus, since the ply cord can be attached to the forming surface movable in the tire circumferential direction using the supply head movable in the tire width direction, the arrangement pitch of the ply cords can be easily changed. be able to.

  The tread pattern is formed so that the driving density of the blocks 6 has the above-mentioned relationship when vulcanizing the tire formed by using the carcass ply in which the arrangement pitch of the ply cords 9 is changed as described above. In other words, in the example of FIG. 3, the circumferential position of the mold that forms the tread surface 8 is determined so that the driving density of the block 6a is larger than the driving density of the block 6e.

[Other Embodiments]
(1) In the above-described embodiment, the carcass layer 4 is composed of one carcass ply. However, in the present invention, the carcass layer 4 may be composed of a plurality of carcass plies. In such a case, if the driving density of the blocks 6 is in the above-described form in relation to at least one carcass ply constituting the carcass layer 4, preferably in relation to the carcass ply disposed on the outermost periphery. Good.

  (2) In the above-described embodiment, an example in which a tread pattern that is symmetric with respect to the tire equator line C is shown, but the present invention is not limited to this, and an asymmetry with an asymmetry with respect to the tire equator line C. A tread pattern may be formed.

  (3) The present invention may be one in which sipes are formed in the block 6 for the purpose of improving the low noise performance or ice performance of the tire. In such a case, it is preferable to adjust the driving density of the block 6 in consideration of sipe. Specifically, it is preferable to determine the driving density of the block 6 using the area of the block 6 excluding the sipe area.

  (4) FIG. 5 is a plan view of a block group included in a tread pattern according to another embodiment. The block group 17 includes blocks 18 and 19 having different shapes arranged in the tire circumferential direction, and the sizes of the blocks 18 and 19 do not sequentially change along the tire circumferential direction. Even in such a case, the above-described effects can be obtained by forming the driving density of the blocks 18a and 19a having the minimum area of the block group 17 to be larger than the driving density of the blocks 18b and 19b having the maximum area. It is done.

(5) FIGS. 6 and 7 are plan views of a block group included in a tread pattern according to another embodiment. However, the present invention defines the relationship of driving density in a tire block group consisting of a plurality of blocks that are not connected to each other in the tire circumferential direction and the tire width direction as shown in FIG. Having a group is not included in the present invention. The block group 20 shown in FIG. 6 has a land portion 22 extending in the tire circumferential direction on one side in the width direction, and each block 21 is connected to the land portion 22. In the block group 23 shown in FIG. 7, a block 24 and a block 25 are connected in the width direction at periodically formed land portions 26. Even in such a block group, the rigidity varies depending on the size of each block, and the driving density of the block with the smallest area of the block group is made larger than the driving density of the block with the largest area. By forming, the above-mentioned operation effect is obtained. In this case, the blocks used when determining the driving density can be determined by excluding the land portions 22 and 26 as shown by the dotted line frame 27 in FIGS.

  (6) In the above-described embodiment, the example in which the variation tendency of the circumferential length of each block 6 is equal in the tire width direction between the block groups 10, 11, and 12 is shown, but the present invention is not limited to this. Absent. When the variation tendency of the area of each block constituting the block group is different in the tire width direction, it is preferable to adjust the driving density of the block by paying attention to the block group having the largest block area.

  Examples that specifically show the structure and effects of the present invention will be described below. In evaluating the following items, test tires having a tire size of 185 / 65R15 88H having the tread pattern shown in FIG. 2 were produced. In the test tire, the carcass layer was constituted by one carcass ply, and a polyester cord of 1670 dtex / 2 was used as the ply cord. An example in which the ply cord arrangement pitch is uniform was taken as a conventional example, and an example in which the block driving density was adjusted was taken as an example. Table 1 shows the driving density of the blocks 6a to 6b constituting the block group 10 in the conventional example and the example. The driving density is represented by an index when the conventional example is 100.

（１）乗心地性能
ホイールサイズ１５×６．０ＪＪのリムに組み付け、空気圧を２１０ｋＰａとしたテストタイヤを、実車（国産車、２名乗車）に装着し、良路および悪路を走行してフィーリング試験による官能評価を行った。フィーリング試験では、乗員にテストタイヤの種類をふせておき、実車走行の後に１０点満点における採点を行わせた。点数が多いほど乗心地が良好であることを示す。

(1) Ride comfort performance A test tire with a wheel size of 15 x 6.0 JJ and an air pressure of 210 kPa is mounted on a real car (domestic car, 2 passengers), driving on good and bad roads. Sensory evaluation by a ring test was performed. In the feeling test, the occupant was informed of the type of the test tire, and the scoring was performed with a maximum score of 10 after running the vehicle. The more points, the better the riding comfort.

(2) Uniformity Based on the test method prescribed in JIS D 4233, RFV (radial force variation) representing the magnitude of the force variation in the tire radial direction generated in the tire receiving the load was measured. Moreover, TFV (tangential force variation) representing the magnitude of the fluctuation of the force in the longitudinal direction of the tire generated in the tire receiving the load was measured based on JASO C618.

  Specifically, a test tire with a wheel size of 15 × 5.5 JJ and an air pressure of 200 kPa is pressed against the rotating drum under a load of 430 kg, and the axial distance between the tire and the rotating drum is kept constant. While, the amount of fluctuation in the force in the tire radial direction and the tire longitudinal direction generated when the tire was rotated was measured. The smaller the numerical value, the smaller the amount of force fluctuation, and the better the uniformity.

表２より、実施例では、ブロックの打ち込み密度を調整することにより、ブロック毎の剛性のばらつきが改善され、従来例よりも乗心地性能に優れていることがわかる。また、実施例では、ＲＦＶとＴＦＶとが共に従来例よりも小さく、ユニフォミティに優れていることがわかる。特に、ＴＦＶは、ブロックの剛性に起因して変動することが知られており、タイヤ周方向におけるブロックの剛性のばらつきが小さいことがわかる。これにより、本発明は、ピッチバリエーションタイプのトレッドパターンにおいて、耐多角形摩耗性を高めうるものであることがわかる。

From Table 2, it can be seen that, in the example, by adjusting the driving density of the blocks, the variation in rigidity of each block is improved, and the riding comfort performance is superior to the conventional example. In the example, both RFV and TFV are smaller than the conventional example, and it can be seen that the uniformity is excellent. In particular, TFV is known to vary due to the rigidity of the block, and it can be seen that there is little variation in the rigidity of the block in the tire circumferential direction. Thus, it can be seen that the present invention can improve the polygonal wear resistance in the pitch variation type tread pattern.

Half sectional view showing an example of pneumatic radial tire Half plan view showing an example of tread pattern The top view which illustrates the outline of the tire block projected on the carcass ply Diagram explaining the driving density of the tire block The top view of the block group which the tread pattern concerning another form has Plan view of a block unit having the tread pattern according to another embodiment (however, not intended containing Murrell to the present invention.) Plan view of a block unit having the tread pattern according to another embodiment (however, not intended containing Murrell to the present invention.) Conceptual side view of a tire with polygonal wear

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Carcass layer 6 Tire block 6a Minimum area block 6e Maximum area block 7 Belt layer 8 Tread surface 9 Ply cord 10, 11, 12 Block group 16 Tire block outline 17 Tire block Group 18, 19 Tire block 20 Tire block group 21 Tire block 22 Land 23 Tire block group 24, 25 Tire block 26 Land 27 Dotted frame (tire block)
C tire equator line

Claims (2)

A pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, a tread portion connected to each outer peripheral side end of the sidewall portion, and an angle of approximately 90 ° with respect to the tire equator line In a pneumatic radial tire comprising a carcass layer formed by extending at least one carcass ply formed of a ply cord extending between the bead parts,
The total length of the ply cord surrounded by the outline of the tire block projected on the inner peripheral side toward the carcass ply per area of the tire block formed in the tread portion is the driving density of the tire block. and when,
A tire block group arranged in the tire circumferential direction, which is divided only by a main groove along the tire circumferential direction and a secondary groove crossing the main groove, and there is no mutual connection in the tire circumferential direction and the tire width direction A pneumatic radial characterized in that the driving density of a tire block having a minimum area of a tire block group including a plurality of tire blocks is set larger than the driving density of a tire block having a maximum area of the tire block group. tire.   2. The pneumatic radial tire according to claim 1, wherein the driving density of the tire block increases as the area of each tire block constituting the tire block group arranged in the tire circumferential direction decreases.

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