JP5388556B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a plurality of land portion rows along a tire circumferential direction are formed in a tread portion.

In a pneumatic tire such as a studless tire, a block pattern for improving performance on ice and snow is formed on a tread portion. Such a block pattern is usually a pattern in which a plurality of block rows along the tire circumferential direction are formed by circumferential grooves and lateral grooves formed in the tread portion. In each block constituting the block row, a plurality of sipes extending in the tire width direction are usually arranged in the tire circumferential direction. (For example, see Patent Document 1)
JP 2007-314137 A

By the way, in order to improve the performance on ice and snow, it is necessary to increase the number of sipes and to fully exhibit the edge effect (scratch effect) by the sipes.
On the other hand, when the number of sipes is increased, the rigidity of the block (the rigidity in the front-rear direction of the block) decreases, and the collapse of the block increases. Therefore, when the contact area of the block decreases, the driving performance and the braking performance (brake performance) on the dry road surface (dry road surface) are lowered, and the steering stability performance is deteriorated.
For this reason, there has been a demand in the market for a pneumatic tire with improved performance on ice and snow and improved steering stability performance on a dry road surface.

  As a countermeasure, Patent Document 1 proposes a pneumatic tire that suppresses a decrease in rigidity in the front-rear direction of the block even when the number of sipes is increased. However, it is more preferable that the tire has further improved steering stability performance by further improving the block rigidity.

  In view of the above fact, an object of the present invention is to provide a pneumatic tire that further improves the steering stability performance on a dry road surface while maintaining the performance on ice and snow.

  The invention according to claim 1 is a pneumatic tire in which a plurality of land portion rows along the tire circumferential direction are formed in the tread portion by a circumferential groove and a lateral groove, and the center that constitutes the circumferential groove A main groove is formed on the tire equator, and a circumferential land portion row adjacent to both sides of the central main groove is formed in the tread portion, and a plurality of blocks constituting the circumferential land portion row include a plurality of blocks. Are formed along the tire circumferential direction on the tire equator side with respect to the tire width direction center position of the block.

  In the first aspect of the present invention, a plurality of width direction sipes are formed in the blocks constituting the circumferential land portion rows adjacent to both sides of the central main groove. And the interruption part which interrupts this width direction sipe in the middle is formed. Accordingly, in the block portion where the width direction sipes are formed, the portion where the interrupted portion is formed has higher rigidity than the portion where the interrupted portion is not formed.

  Here, in order to improve the steering stability by the fluttering center feel (fluctuation during straight running and the feeling of vehicle responsiveness when a small steering angle is added), CF (cornering force) or SAT (Self-aligning torque) needs to be increased. These focus on the tire equator and its vicinity. When the central main groove is formed as in the present invention, the steering stability is improved by increasing the rigidity of the circumferential land portion row adjacent to the central main groove. It is effective in making it. Therefore, the rigidity of the circumferential land portion row is effectively improved by forming the interrupted portion.

  Moreover, this discontinuous part is arrange | positioned along the tire circumferential direction. In other words, the interrupted portion can more effectively suppress the lateral external force perpendicular to the traveling direction (which causes fluttering), and can effectively improve the steering stability on the dry road surface. .

  In general, when the load is low, the contact length decreases greatly from the tire equator to the tread end. Therefore, in Claim 1, the effect obtained becomes more remarkable by arrange | positioning the said interruption part in the tire equator vicinity with a longer contact length. Therefore, according to the present invention, it is possible to greatly suppress the flutter during traveling.

  The tread end means that a pneumatic tire is mounted on a standard rim specified in JATMA YEAR BOOK (2008 edition, Japan Automobile Tire Association Standard) and the maximum load capacity in the applicable size and ply rating in JATMA YEAR BOOK. Fills 100% of the air pressure (maximum air pressure) corresponding to (internal pressure-load capability correspondence table) as the internal pressure, and indicates the outermost contact portion in the tire width direction when the maximum load capability is applied. In addition, when TRA standard and ETRTO standard are applied in a use place or a manufacturing place, it follows each standard.

  According to a second aspect of the present invention, the width-direction sipe extends in a zigzag shape in the sipe longitudinal direction, and opens to the circumferential groove at least at one end.

  Thereby, the block flexibility (that is, the softness of the block for deeper contact with the road surface) necessary for winter tires and many edge components (that is, the components that scratch the road surface) can be obtained.

In the invention according to claim 3, the width in the tire width direction of the discontinuous portion is in the range of 1.0 to 2.6 mm.
This is because if it is less than 1.0 mm, it is difficult to obtain the effect of improving the steering stability, and if it exceeds 2.6 mm, the friction coefficient μ tends to decrease.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the pneumatic tire which further improved the steering stability performance on the dry road surface, maintaining the performance on ice and snow.

  Hereinafter, a truck / bus tire is taken as an example as an embodiment, and an embodiment of the present invention will be described.

As shown in FIG. 1, a pneumatic tire 10 according to an embodiment of the present invention includes a carcass 12 whose both ends are folded at bead cores 11 </ b> C of bead portions 11.
A belt layer 14 (for example, 1 belt 14A, 2 belt 14B, and 3 belt 14C) is embedded on the outer side of the crown portion 12C of the carcass 12 in the tire radial direction.

  A tread portion 18 having grooves is formed on the outer side of the belt layer 14 in the tire radial direction. The tread portion 18 is formed with three circumferential main grooves. Since the tread pattern of the tread portion 18 is symmetrical with respect to the tire equator CL, the tread portion on one side from the tire equator CL will be described in detail below, and the description of the remaining tread portions will be omitted.

  The circumferential main groove is composed of a first main groove 22 that passes over the tire equator CL and second main grooves 23 that are formed on both outer sides in the tire width direction of the first main groove 22.

  The tread portion 18 is connected to an inner inclined groove 24 that is open to the first main groove 22 and is inclined with respect to the tire circumferential direction U, and an outer end in the tire width direction of the inner inclined groove 24. An outer inclined groove 26 whose inclination direction with respect to U is opposite to the inner inclined groove 24 is formed. The outer inclined groove 26 opens to the second main groove 23. As a result, the first block row 28 along the tire circumferential direction U is formed between the first main groove 22 and the second main groove 23L. In the first block row 28, blocks 28 defined by the first main groove 22, the second main groove 23, the inner inclined groove 24, and the outer inclined groove 26 are arranged in the tire circumferential direction U. A bottom raised portion 30 for increasing the groove height is formed at the bottom of the inner inclined groove 24.

  Further, the tread portion 18 is formed with a width direction groove 32 that opens to the second main groove 23 and extends to the outer side in the tire width direction (left direction in the drawing in the V direction in FIG. 2). As a result, the second block row 34 is formed outside the second main groove 23 in the tire width direction.

  Further, the first block row 28 is formed with sub-grooves 35 that open to the outer inclined grooves 26 and are closed within the blocks. The sub-groove 35 is inclined with respect to the tire circumferential direction U so that the inclination direction is opposite to that of the outer inclined groove 26.

A plurality of width direction sipes 38 are formed in the block portion 36I on the tire equator CL side of the auxiliary groove 35. Each width-direction sipe 38 extends in a zigzag shape in the sipe longitudinal direction, and opens to the first main groove 22 at one end. In the block portion 36I, a discontinuous portion 40 that interrupts the widthwise sipe 38, that is, a discontinuous portion 40 in which the sipe wall surfaces of the widthwise sipe 38 are connected to each other, is more tire equator than the center position in the tire width direction. It is arranged along the tire circumferential direction U on the CL side. Therefore, the site | part in which the interruption part 40 is formed is continuing in the tire circumferential direction U within the block part 36I. The width W of the interrupted portion 40 is in the range of 1.0 to 2.6 mm.
A width-direction sipe 42 is also formed in the block portion 36E on the tread end T side of the sub-groove 35. The width direction sipe 42 formed in the block portion 36E is not interrupted.

  A plurality of width direction sipes 48 are also formed in each block 46 constituting the second block row 34. Each block 46 is formed with a circumferential sipe 50 that is connected to the widthwise grooves 32 adjacent to each other in the tire circumferential direction U. The width sipe 48 is formed on both sides of the circumferential sipe 50 in the tire width direction. A plurality are formed along the direction U. The width sipe 48 does not open to the circumferential sipe 50.

  As described above, in the present embodiment, in the circumferential block row (the first block row 28 in FIG. 2) adjacent to both sides of the first main groove 22, a plurality of widthwise sipes 38 are formed in each block 36. Has been. And the interruption part 40 which made the sipe wall surface continue is formed so that this width direction sipe 38 may interrupt in the middle. Therefore, in the block portion where the width direction sipe 38 is formed, the portion where the interrupted portion 40 is formed has higher rigidity than the portion where the interrupted portion 40 is not formed.

  Here, as described above, it is necessary to increase CF (cornering force) and SAT (self-aligning torque) in order to improve steering stability such as flutter and center feel. These have the tire equator CL and the vicinity thereof as a power point. When the first main groove 22 that passes over the tire equator CL is formed as in the present embodiment, the first main groove 22 adjacent to the first main groove 22 is formed. Increasing the rigidity of the block row 28 is effective in improving steering stability. Therefore, the rigidity of the first block row 28 is effectively improved by forming the interrupted portion 40.

  Further, the interrupted portion 40 is disposed along the tire circumferential direction U. That is, the interrupted portion 40 can more effectively suppress the lateral external force perpendicular to the traveling direction (the cause of the flutter), and can effectively improve the steering stability on the dry road surface. it can.

  Further, when the load is low, the contact length decreases greatly from the tire equator CL to the tread end T. Therefore, by arranging the discontinuous portion 40 in the vicinity of the tire equator CL having a longer contact length, this effect becomes more prominent, and flutter during running can be greatly suppressed.

  Further, each width direction sipe 38 extends in a zigzag shape in the sipe longitudinal direction, and opens in any of the circumferential main grooves at at least one end. Thereby, block flexibility required for winter tires and many edge components can be obtained.

  Further, the width W of the interrupted portion 40 is set to a range of 1.0 to 2.6 mm. As a result, the steering stability can be sufficiently improved without lowering the friction coefficient μ.

<Test example>
In order to confirm the effect of the present invention, the present inventor made four examples of the pneumatic tire according to the above embodiment (hereinafter referred to as tires of Examples 1 to 4) and an example of a pneumatic tire for comparison (hereinafter referred to as a tire). A tire of a comparative example (see FIG. 3) was prepared. Then, a snow road base μ-S driving test, a snow road base μ-S braking test, and a steering stability test were performed to evaluate the performance of each tire.

  Here, the μ-S driving test on the snow road base is a method in which a snow road is formed on a turntable tester and a tire is run on the snow road to drive the peak μ at the time of driving, that is, the friction coefficient μ. This is a test that measures high values. In this test example, the peak μ from 10 km / h to 20 km / h was measured.

  Similarly, the on-snow μ-S braking test is a test in which a snow road is formed on a turntable tester and a tire is run on the snow road to measure the peak μ during braking. In this test example, the peak μ from 10 km / h to 0 km / h was measured.

  In the driving stability test, the vehicle was run on the dry road surface of the test course, and the performance was evaluated by the feeling of the panelists. In this evaluation, a score of 10 points was given, and a score of 6 or more was given as the second grade.

  The tire of Example 1 is a tire in which the width of the interrupted portion 40 is 0.8 mm. The tire of Example 2 is a tire in which the width of the interrupted portion 40 is 1.2 mm. The tire of Example 3 is a tire in which the width of the interrupted portion 40 is 2.5 mm. The tire of Example 4 is a tire in which the width of the interrupted portion 40 is set to 3.0 mm.

  Compared to the tires of Examples 1 to 4, the tire of the comparative example is formed by replacing the width-direction sipe 88 with the width-direction sipe 38 by not forming the discontinuity 40 as shown in FIG. Tire.

In this test example, all tire sizes were 235 / 65R16C 115 / 113R.
In this test example, all tires were tested in a state where the applied rim was 7 J × 16, the internal pressure was 475 kPa, and a normal load was applied. Here, “regular load” refers to the maximum load in the applicable size / ply rating defined in the 2008 YEAR BOOK issued by JATMA.
The test results are shown in Table 1.

表１から判るように、雪路台上μ−Ｓ駆動試験でのピークμ、雪路台上μ−Ｓ制動試験でのピークμは、実施例１〜４タイヤでは何れも比較例のタイヤに比べて同等であった。

As can be seen from Table 1, the peak μ in the snow road base μ-S driving test and the peak μ in the snow road base μ-S braking test are the same as those of the tires of the comparative examples. It was equivalent.

  And the steering stability performance in the dry road surface was improving significantly compared with the tire of the comparative example in all of Examples 1-4 tire.

  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 top view showing a tread pattern of a pneumatic tire concerning one embodiment of the present invention. It is a top view which shows the tread pattern of the tire of the comparative example used by the test example.

Explanation of symbols

10 Pneumatic tire 18 Tread portion 22 First main groove (central main groove)
28 1st block row (circumferential land portion row)
36 Block 38 Width sipe 40 Discontinuity CL Tire equator U Tire circumferential direction W Width

Claims (3)

A pneumatic tire in which a plurality of land portion rows along the tire circumferential direction are formed by a circumferential groove and a lateral groove in the tread portion,
A central main groove constituting the circumferential groove is formed on the tire equator, and a circumferential land portion row adjacent to both sides of the central main groove is formed on the tread portion,
A plurality of width direction sipes are formed in the blocks constituting the circumferential land portion row, and the discontinuity portion that interrupts the width direction sipes in the middle of the block is closer to the tire equator than the center position in the tire width direction of the block A pneumatic tire is disposed along the tire circumferential direction.   2. The pneumatic tire according to claim 1, wherein the width-direction sipe extends in a zigzag shape in the sipe longitudinal direction, and opens in the circumferential groove at least at one end.   The pneumatic tire according to claim 1 or 2, wherein a width in a tire width direction of the discontinuous portion is in a range of 1.0 to 2.6 mm.

Images