JP2008230385A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire that suppresses the occurrence of a river wear along a land part row along the tire circumferential direction. <P>SOLUTION: A center main groove 22, and shoulder main grooves 24, 26 are formed in a tread part 18 of the pneumatic tire. These three main grooves 22, 24, 26 extend in zigzags at the same phase in the tire circumferential direction, and four rows of land part rows are formed in the tread part 18. Out of the four land part rows, two land part rows 32, 34 positioned on a tire equator surface CL side are divided by sipes 40, 50 having central parts tilted with respect to the tire equator surface CL. The sipes 40, 50 are alternately disposed in the tire circumferential direction. The central part 44 of the sipe 40 and the central part 54 of the sipe 50 are arranged to tilt alternately in reverse directions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a plurality of main grooves are formed in the tire circumferential direction, and more particularly to a pneumatic tire particularly suitable for trucks and buses.

  Truck and bus tires (TBR tires) having a rib pattern in which main grooves (swing grooves) extending in a zigzag shape along the tire circumferential direction are widely used (see, for example, Patent Document 1).

  As described above, in a tire having a swing groove along the tire circumferential direction, uneven wear with the swing groove as a starting point may occur in a land portion row (rib row) sandwiched between the swing grooves, depending on use conditions. For example, if a sipe groove or runner groove is formed in the land row adjacent to the center main groove in order to improve grip and wettability, the rib rigidity becomes uneven in the tire circumferential direction and the tire width direction, which is the cause. As a result, riverware is generated in the rib pattern. The river wear is uneven wear in which the land portion row is worn along the main groove over a certain width from the edge, and the step is different from the inner portion of the land portion row that is not worn.

  In Patent Document 1, an auxiliary groove that crosses the block partitioned by the main groove halfway is formed, and the groove width of the auxiliary groove and the lug groove, and the groove width of the main groove located on both sides in the tire width direction of the center main groove It has been studied to suppress the occurrence of riverware by adjusting the ratio, but there is a limit to suppressing the occurrence of riverware by this alone.

The problem of the occurrence of riverware is noticeable in truck and bus tires, but it has also occurred in general pneumatic tires.
Japanese Patent Laid-Open No. 6-1113

  In view of the above facts, an object of the present invention is to provide a pneumatic tire that suppresses occurrence of river wear in a land row along the tire circumferential direction.

  The invention according to claim 1 is a pneumatic tire in which four land portion rows are formed in the tread portion by three main grooves extending in the circumferential direction of the tire, and the three main grooves are zigzag in phase. The two land portion rows that extend in a shape and are located on the tire equatorial plane side are divided by a sipe or groove having a portion inclined with respect to the tire equatorial plane, and the two land portion rows are inclined. The portions are arranged in the tire circumferential direction so as to alternately incline in opposite directions.

  The fact that the main groove extends in a zigzag shape means that the groove portions that are inclined with respect to the extending direction of the main groove extend while being folded so that the inclined directions are alternate. The same phase means that the inclined direction of the inclined groove portion is aligned in the same direction in each main groove at the position in the tire width direction.

  In the invention according to the first aspect, in this manner, four rows of land portion rows are formed in the tread portion by the three main grooves extending in the tire circumferential direction, and the three main grooves are zigzag in phase. It extends to. Thereby, the rigidity in the tire circumferential direction and the tire width direction of each land portion row can be made uniform, and uneven wear resistance (reverse wear resistance) is improved.

  Further, since the inclined portions are arranged in the tire circumferential direction of the land portion rows so as to alternately incline in the opposite directions, it is possible that the directionality of rigidity occurs in each land portion row. Can be suppressed.

  The invention according to claim 2 is characterized in that the cross-sectional shapes in the width direction of the three main grooves are equal.

  Thereby, the rigidity of the edge part of a groove | channel can be equalized and riverware resistance can be improved.

The invention according to claim 3 is characterized in that the maximum width of each of the four land portion rows is equal.
Thereby, since the width of each land part row | line becomes substantially uniform, the rigidity of the tire circumferential direction of each land part row | line | column and the tire width direction can be made further uniform, and riverware resistance further improves.

Since the present invention has the above configuration, the following effects can be obtained.
According to invention of Claim 1, the rigidity of the tire circumferential direction of each land part row | line | column and the tire width direction can be equalize | homogenized, and riverware resistance improves.
According to invention of Claim 2, the rigidity of the edge part of a groove | channel can be equalize | homogenized and riverware resistance can be improved.
According to the invention described in claim 3, since the width of each land portion row becomes substantially uniform, the rigidity in the tire circumferential direction and tire width direction of each land portion row can be further uniformed, The property is further improved.

  Hereinafter, embodiments will be described and embodiments of the present invention will be described. As shown in FIG. 1, a pneumatic tire 10 according to an embodiment of the present invention is a tire used for a truck or a bus, and a toroid between a bead portion 12 having a pair of bead cores 11 and a pair of bead cores 11. And at least one layer of carcass 14 extending in a shape. Further, in the pneumatic tire 10, a belt layer 16 and a tread portion 18 provided with grooves are sequentially arranged outside the crown portion 14 </ b> C of the carcass 14. Further, the pneumatic radial tire 10 is provided with a sidewall portion 20 between the bead portion 11 and the tread portion 18.

  As shown in FIG. 2, the tread portion 18 includes a center main groove 22 extending in the tire circumferential direction on the tire equatorial plane CL, and shoulder main grooves 24 and 26 extending in the tire circumferential direction U on both sides of the center main groove 22, respectively. A total of three main grooves are formed. The three main grooves extend in a zigzag shape with the same phase. The cross-sectional shapes in the tire width direction of the main grooves are equal to each other.

  FIG. 2 shows the position of the tread end T. Here, the tread end T means that a pneumatic tire is mounted on a standard rim prescribed in JATMA YEAR BOOK (2006 edition, Japan Automobile Tire Association Standard), and is the maximum applicable size / ply rating in JATMA YEAR BOOK. Fills 100% of the air pressure (maximum air pressure) corresponding to the load capacity (internal pressure-load capacity correspondence table) as the internal pressure, and indicates the outermost ground contact portion in the tire width direction when the maximum load capacity is loaded. In addition, when TRA standard and ETRTO standard are applied in a use place or a manufacturing place, it follows each standard.

  Four main land rows 30, 32, 34, and 36 are formed in the tread portion 18 by three main grooves including the center main groove 22 and the shoulder main grooves 24 and 26. The position in the tire width direction of the center main groove 22 and the shoulder main grooves 24 and 26 is a position where the rib distribution of the four land portion rows is equal. Accordingly, the shoulder main groove 24 is formed at a position in the tire width direction where the rib distribution between the land portion row 30 and the land portion row 32 is 1: 1, and the shoulder main groove 26 is also formed as a rib distribution between the land portion row 34 and the land portion row 36. Is formed at a position in the tire width direction with a ratio of 1: 1. Further, the maximum width of each land portion row is set to the same maximum width B for all four rows.

Sipes 40 and 50 having portions inclined with respect to the tire equatorial plane CL are arranged in the two land portion rows 32 and 34 located on the tire equatorial plane CL side.
The sipe 40 and the sipe 50 are alternately disposed in the tire circumferential direction U one after another. The sipe shape is the same in the land portion row 32 and the land portion row 34.

  Further, both ends of the sipe 40, 50 are open to the main groove. As a result, the land portion rows 32, 34 are divided by each sipe, and the small land portions are aligned in the tire circumferential direction U in plan view. Looks like a line. In the sipe 40, both end portions 42 are formed along the tire width direction V, and the central portion 44 is inclined with respect to the tire equatorial plane CL. In the sipe 50, both end portions 52 similar to the both end portions 42 are formed along the tire width direction V, and the center portion 54 is inclined in the direction opposite to the center portion 44. In the present embodiment, the inclination angles of the central portions 44 and 54 with respect to the tire equatorial plane CL are the same angle θ. In addition, in the land portion row 32 and the land portion row 34, the formation positions of the sipes 40 and 50 are in the same phase, that is, the tire circumferential position of the sipe 40 and the tire circumferential position of the sipe 50 are The partial row 32 and the land portion row 34 are at the same position.

  Moreover, as the convex part 29 which comprises the land part row | line | column 30 and becomes convex with respect to the shoulder main groove 24, the convex part 29Y in which the sipe 58 is formed, and the convex part 29N in which the sipe 58 is not formed. Is arranged. In the present embodiment, two convex portions 29Y and one convex portion 29N are sequentially arranged in the tire circumferential direction U in this order.

  Similarly, as the convex portion 35 that constitutes the land portion row 36 and is convex with respect to the shoulder main groove 26, a convex portion 35Y where the sipe 58 is formed, and a convex portion 35N where the sipe 58 is not formed, Is arranged. And like the land part row | line | column 30, in the tire circumferential direction U, the convex part 35Y and the convex part 35N are sequentially arrange | positioned in order of one. The sipe 58 is a short sipe along the tire width direction V, and is open to the main groove at one end and closed in the land portion row at the other end.

  In the land portion row 32, sipes 58 are formed on all convex portions that are convex with respect to the shoulder main groove 24. Moreover, as the convex part 31 which comprises the land part row | line | column 32 and becomes convex with respect to the center main groove | channel 22, the convex part 31Y in which the sipe 58 is formed, and the convex part 31N in which the sipe 58 is not formed are arrange | positioned Has been. In the present embodiment, two convex portions 31Y and one convex portion 31N are sequentially arranged in the tire circumferential direction U in this order.

  In the land portion row 34, sipes 58 are formed on all convex portions that are convex with respect to the shoulder main groove 26. Moreover, as the convex part 33 which comprises the land part row | line | column 34 and is convex with respect to the center main groove | channel 22, the convex part 33Y in which the sipe 58 is formed, and the convex part 33N in which the sipe 58 is not formed are arrange | positioned. Has been. In the present embodiment, two convex portions 33Y and one convex portion 33N are sequentially arranged in the tire circumferential direction U in this order.

  As described above, in the present embodiment, the tread portion 18 has four land portion rows 30 by the three main grooves (the center main groove 22 and the shoulder main grooves 24 and 26) extending in the tire circumferential direction U. , 32, 34, and 36 are formed. The three main grooves extend in a zigzag manner with the same phase. Thereby, the rigidity of the tire circumferential direction U and the tire width direction V of each land part row | line | column 30, 32, 34, 36 can be equalize | homogenized, and the partial wear resistance (riverware resistance) has improved.

  Further, the tire width direction positions of the center main groove 22 and the shoulder main grooves 24, 26 are positions where the rib distribution of the four land portion rows 30, 32, 34, 36 is equal, The maximum width of the land portion row is the maximum width B that is the same for all four rows. Thereby, the rigidity of the tire circumferential direction of each land part row | line | column and the tire width direction can be made further uniform, and it has the structure which further suppresses generation | occurrence | production of riverware.

  The three main grooves (center main groove 22, shoulder main grooves 24, 26) extend in the tire circumferential direction U in the same phase in a zigzag shape. Thereby, it can suppress that the directionality of rigidity generate | occur | produces in each land part row | line | column of 4 rows.

  The three main grooves (center main groove 22, shoulder main grooves 24, 26) have the same cross-sectional shape in the tire width direction. Thereby, the rigidity of the edge part of each main groove can be equalize | homogenized, and riverware resistance can be improved.

  Further, sipes 40 and 50 are formed in the land portion rows 32 and 34 located on the tire equatorial plane CL side among the four land portion rows, whereby the wet property and the grip property of the pneumatic tire 10 are formed. Has improved.

  In addition, center portions 44 and 54 that are inclined with respect to the tire equatorial plane CL are formed in the sipes 40 and 50, respectively. Thereby, the nonuniformity of rigidity in the tire circumferential direction U is alleviated.

  Furthermore, the inclination directions of the central portion 44 of the sipe 40 and the central portion 54 of the sipe 50 are opposite to each other, and the sipe 40 and 50 are alternately arranged in the tire circumferential direction U. Thereby, the directionality of the rigidity generated in the land portion rows 32 and 34 by the sipes 40 and 50 is canceled. Therefore, the directivity does not appear in the rigidity of the land portion row as in the case of the same inclination direction. Since the sipe 40, 50 has the same shape and the same phase in the land portion rows 32, 34, the tire width direction rigidity of the land portion rows 32, 34 is made uniform.

  Convex portions 29Y and 35Y in which sipes 58 are formed are respectively disposed in the land portion rows 30 and 36 located on the outer side in the tire width direction among the four land portion rows. As a result, the rigidity of the ribs in the tire circumferential direction U of the land portion rows 30 and 36 can be made uniform to further reduce the uneven wear resistance (riverware performance).

  In the present embodiment, the sipe 40, 50 is formed on the land portion rows 32, 34. However, a horizontal groove or a hot dip inclined at the center as in the sipe 40, 50 is used. Instead of the sipes 40 and 50, they may be formed.

<Test example>
In order to confirm the effect of the present invention, the present inventor made an example of the pneumatic tire 10 of the first embodiment (hereinafter referred to as an example) and two examples of a pneumatic tire for comparison (hereinafter referred to as a comparative example). 1 and Comparative Example 2) were prepared, and the degree of uneven wear (river wear) due to actual running was measured and evaluated.

  As shown in FIG. 3, in Comparative Example 1, a center main groove 72 is formed instead of the center main groove 22 and shoulder main grooves 74, 76 are formed instead of the shoulder main grooves 24, 26, compared to the embodiment. ing. The center main groove 72 is a main groove extending in a zigzag shape in the tire circumferential direction U, like the center main groove 22. The shoulder main grooves 74 and 76 are main grooves extending in the same phase and shape in the tire circumferential direction U. The shoulder main groove 74 includes a staggered groove portion 78 and a staggered groove portion 78 adjacent in the tire circumferential direction. The shoulder main groove 76 has the same configuration as the shoulder main groove 74, and the shoulder main grooves 74 and 76 and the center main groove 72 are different in shape. Therefore, the rib distribution between the land portion row 80 and the land portion row 82 and the rib distribution between the land portion row 84 and the land portion row 86 are not 1: 1. In the land portion rows 80 and 82, short sipes 88 that open to the staggered portion 78 of the shoulder main groove 74 are formed at predetermined positions. This sipe 88 is the same sipe as the sipe 58. Similarly, sipes 88 are formed at predetermined positions in the land portion rows 84 and 86 so as to open to staggered portions of the shoulder main groove 76. Further, sipes 88 are formed in the land portion rows 82 and 84 so as to open to the center main groove 72.

  As shown in FIG. 4, in the comparative example 2, a center main groove 92 is formed instead of the center main groove 22 as compared with the embodiment. The center main groove 92 extends in a zigzag shape in the tire circumferential direction U. In the center main groove 92, protrusions 93 are arranged in a line along the center line at the groove bottom. In Comparative Example 2, shoulder main grooves 94 and 96 are formed in place of the shoulder main grooves 24 and 26. The shoulder main groove 94 is a main groove extending in a zigzag shape in the tire circumferential direction U, and an inversion groove 98 that is slightly inverted is formed at a corner that is concave with respect to the tire equatorial plane CL. The shoulder main groove 96 is also shaped similar to the shoulder main groove 94, but the shoulder main groove 94 and the shoulder main groove 96 are not in phase. The shoulder main grooves 94 and 96 are different in shape from the center main groove 92. Therefore, the rib distribution between the land portion row 100 and the land portion row 102 and the rib distribution between the land portion row 104 and the land portion row 106 are not 1: 1. In Comparative Example 2, a sipe 110 is formed instead of the sipe 40 or 50. The sipe 110 is inclined in the same direction with respect to the tire equatorial plane CL at both end portions 112 and the central portion 114, and the central portion 114 and the tire equatorial plane are more than the angle α formed between the both end portions 112 and the tire equatorial plane CL. The inclination angle β formed with CL is an acute angle. Further, in Comparative Example 2, a short sipe 118 similar to the sipe 88 is formed at a predetermined position connected to the shoulder main grooves 94 and 96.

  Since the comparative examples 1 and 2 are configured as described above, they are tires with a small amount of river wear compared to the conventional pneumatic tires, and are excellent in river wear resistance.

  In this test example, all tire sizes were set to 12R22.5. In each of the example, comparative example 1, and comparative example 20, 20 tires were prepared, assembled into a standard rim, and then subjected to a running test under a normal load with a normal internal pressure. In the running test, the vehicle was set to 2D4 and the tire was attached to the steer shaft to fix the mounting position, and the running distance was set to 50,000 km.

  Here, “regular rim” refers to a standard rim in the applicable size specified in the 2006 YEAR BOOK issued by JATMA, for example, and “normal load” and “regular internal pressure” are also issued by JATMA. The maximum load in the applicable size and ply rating defined in the 2006 YEAR BOOK and the air pressure with respect to the maximum load. When the TRA standard or ETRTO standard is applied at the place of use or manufacturing, the respective standards are followed.

  In this test example, in any of the example, comparative example 1, and comparative example 2, after running, the amount of riverware generated in the land side row on the center side was obtained. The value of the riverware amount was determined by calculating the product of the depth and width of the volume of the rubber part subjected to riverware. And the average value of the riverwear amount of 20 tires was calculated.

In the examples, the evaluation at this average value was taken as the evaluation index 100. In Comparative Example 1 and Comparative Example 2, an evaluation index that is a relative evaluation with respect to the Examples was calculated. The evaluation results are shown in Table 1.

  The evaluation results in Table 1 indicate that the larger the evaluation index, the greater the amount of riverware. As can be seen from Table 1, in Comparative Examples 1 and 2, the amount of riverware was larger than that in Examples. Here, since the comparative examples 1 and 2 are excellent in river wear resistance as compared with the conventional pneumatic tires as described above, the examples are more excellent in river wear resistance than the comparative examples 1 and 2. As a result, the effect of suppressing the riverware generated from the vicinity of the three main grooves was remarkably recognized.

  The embodiments of the present invention have been described with reference to the embodiments. However, the above embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. Needless to say, the scope of rights of the present invention is not limited to the above embodiment.

1 is a tire radial direction cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a partial top view of the Example used by the test example. It is a partial top view of the comparative example 1 used by the test example. It is a partial top view of the comparative example 2 used by the test example.

Explanation of symbols

10 Pneumatic tire 18 Tread part 22 Center main groove (main groove)
24 Shoulder main groove (main groove)
26 Shoulder main groove (main groove)
30 Land part row 32 Land part row 34 Land part row 36 Land part row 40 Sipe 44 Center part (inclined part)
50 Sipe 54 Center part (inclined part)
72 Center main groove (main groove)
74 Shoulder main groove (main groove)
76 Shoulder main groove (main groove)
80 Land portion row 82 Land portion row 84 Land portion row 86 Land portion row 92 Center main groove (main groove)
94 Shoulder main groove (main groove)
96 Shoulder main groove (main groove)
100 Land portion row 102 Land portion row 104 Land portion row 106 Land portion row 110 Sipe 114 Center portion (inclined portion)
B Maximum width CL Tire equatorial plane U Tire circumferential direction

Claims (3)

In the pneumatic tire in which four rows of land portion rows are formed in the tread portion by three main grooves extending in the tire circumferential direction,
The three main grooves extend in a zigzag shape with the same phase,
Two land part rows located on the tire equatorial plane side are divided by a sipe or groove having a portion inclined with respect to the tire equatorial plane,
The pneumatic tire according to claim 2, wherein the two land portion rows are arranged in the tire circumferential direction so that the inclined portions are alternately inclined in opposite directions.   The pneumatic tire according to claim 1, wherein each of the three main grooves has the same cross-sectional shape in the width direction.   The pneumatic tire according to claim 1 or 2, wherein the maximum width of each of the four rows of land portions is equal.

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