JP2009061797A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of further improving on-ice braking performance by suppressing the falling of blocks even if the number of sipes is increased. <P>SOLUTION: The tread pattern of this pneumatic tire is formed with a plurality of blocks 26 partitioned by circumferential grooves 22, narrow width lug grooves 24N and wide width lug grooves 24W. The narrow width lug grooves 24N have much narrower groove widths than those of the wide width lug grooves 24W. Each of the blocks 26 is formed with a plurality of sipes 28 along the tire width direction V, in addition, with a plurality of small blocks 26A to 26E by the sipes 28. When the blocks are inclined such as upon braking, adjacent blocks are abutted against through the narrow width lug grooves 24N. Accordingly, falling of the blocks 26 is suppressed to significantly improve the on-ice braking performance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a plurality of blocks having sipes are formed in a tread portion.

  Conventionally, improving brake performance (braking performance) on ice has been studied (see, for example, Patent Documents 1 to 4). Here, in order to improve the braking performance on ice, it is necessary to let water generated on the ice escape to the sipe formed in the tread portion of the tire. For this purpose, the number of sipes is increased to increase the amount of water absorption. It is effective.

  However, conventionally, when the number of sipes is increased, an interval between adjacent sipes, that is, an interval between sipes is narrowed, so that the block rigidity is lowered. For this reason, it has been pointed out that the block collapses greatly at the time of ground contact, the ground contact area is reduced, and the improvement of the braking performance on ice is hindered.

  As countermeasures, Patent Documents 1 to 3 propose to increase block rigidity by devising a sipe shape. Further, Patent Document 4 discloses that a rib is formed on a tread portion of a pneumatic tire for a large passenger car, and a brake performance on ice is improved by devising a sipe shape formed on the rib.

However, it is more preferable if the brake performance on ice can be improved by suppressing the collapse of the block by means other than the sipe shape.
JP-A-7-266810 JP-A-8-175115 JP 2005-67274 A JP 2001-71713 A

  In view of the above facts, an object of the present invention is to provide a pneumatic tire that further improves braking performance on ice by suppressing the collapse of the block even when the number of sipes is increased.

  The invention according to claim 1 is a pneumatic tire in which a plurality of blocks defined by a circumferential groove and a lug groove are formed in a tread portion, and a plurality of sipes are formed in the block, A plurality of the lug grooves are narrow lug grooves having a narrow width.

  Here, the narrow-width lug groove in this specification refers to a lug groove whose lug groove width is 7.5% or more and 25% or less of the lug groove depth.

  In the first aspect of the present invention, even when the number of sipes formed in the block is increased, adjacent blocks come into contact with each other via the narrow lug groove when the block is inclined during braking or the like. Therefore, even if the sipe shape is equivalent to a normal sipe (for example, a flat sipe), the block collapse is suppressed, and the braking performance on ice is greatly improved.

  The invention according to claim 2 is that the lug grooves other than the narrow width lug grooves are wide width lug grooves, so that the narrow width lug grooves and the wide width lug grooves have two kinds of width lug grooves. The tires are alternately arranged in the tire circumferential direction.

  In the invention described in claim 2, since the narrow lug grooves and the wide lug grooves are alternately arranged in the tire circumferential direction, the block collapse is more reliably suppressed.

  The invention described in claim 3 is characterized in that the groove width of the narrow lug groove is 20% or more and 40% or less of the groove width of the wide lug groove.

  If it is narrower than 20%, the drainage performance on the wet road surface tends to be lowered. On the other hand, if it is larger than 40%, it is difficult to improve the braking performance on ice.

  According to the third aspect of the present invention, the performance balance between the wet brake (brake on the wet road surface) and the brake on ice (brake on the ice road surface) is improved, and the performance of both is easily achieved to the target performance.

  According to a fourth aspect of the present invention, a plurality of small blocks are formed in the block by the sipe, and a width of the small block adjacent to the wide lug groove is larger than a width of the small block adjacent to the narrow lug groove. It is wide.

  Thereby, the balance of the rigidity in a block becomes good and the fall of a block is suppressed reliably.

  The invention according to claim 5 is characterized in that the width of the plurality of small blocks formed in the block by the sipe is wider as it is closer to the wide lug groove and narrower as it is closer to the narrow lug groove. And

  Thereby, the effect produced by the invention of claim 4 can be made more remarkable.

  According to the present invention, even if the number of sipes is increased, it is possible to provide a pneumatic tire with further improved braking performance on ice by suppressing the collapse of the block.

  Hereinafter, a studless tire for a passenger car will be cited as an embodiment, and an embodiment of the present invention will be described. In the second and subsequent embodiments, the same components as those already described are denoted by the same reference numerals, and description thereof is omitted.

[First Embodiment]
First, the first embodiment will be described. As shown in FIG. 1, a pneumatic tire 10 according to the present embodiment includes a carcass 12 configured by one layer or a plurality of layers, each end portion of which is folded by a bead core 11.

  On the outer side in the tire radial direction of the crown portion 12C of the carcass 12, a belt layer 14 in which a plurality of (for example, two) belt plies are stacked is embedded.

  A tread portion 16 provided with a groove is formed on the outer side of the belt layer 14 in the tire radial direction. As shown in FIG. 2, a plurality of circumferential grooves (main grooves) 22 along the tire circumferential direction U are formed in the tread portion 16 on the tire equatorial plane CL and on both sides thereof. The tread portion 16 is formed with a plurality of lug grooves (sub-grooves) 24 that intersect the tire circumferential direction. In the present embodiment, the lug groove 24 is formed along the tire width direction V. Both end portions of each lug groove 24 communicate with the circumferential groove 22 or extend beyond the tread end T so as to be drained outward in the tire width direction.

  Here, the tread end means that a pneumatic tire is mounted on a standard rim specified in JATMA YEAR BOOK (2005 edition, Japan Automobile Tire Association Standard), and the maximum load in the applicable size and ply rating in JATMA YEAR BOOK. Fills 100% of the air pressure (maximum air pressure) corresponding to the capacity (internal pressure-load capacity correspondence table) as the internal pressure, and indicates the outermost contact portion in the tire width direction when the maximum load capacity is applied. In addition, when TRA standard and ETRTO standard are applied in a use place or a manufacturing place, it follows each standard.

  A large number of blocks 26 are formed in the tread portion 16 by the circumferential grooves 22 and the lug grooves 24.

  As the lug grooves 24, narrow narrow lug grooves 24 </ b> N and wide wide lug grooves 24 </ b> W are alternately arranged in the tire circumferential direction U. The narrow-width lug groove 24N is significantly narrower than the wide-width lug groove 24W. In the present embodiment, the groove width BN of the narrow lug groove 24N is 20% or more and 40% or less of the groove width BW of the wide lug groove 24W.

  As shown in FIGS. 2 to 4, each block 26 is formed with a sipe 28 along the lug groove 24.

  In the present embodiment, four sipe 28 are formed in each block 26, and each sipe 28 is formed along the tire width direction V. The intervals between adjacent sipes 28 are the same. That is, the widths J of the five small blocks 26A to 26E formed in the block 26 by the sipe 28 are the same. In this embodiment, the small block adjacent to the narrow lug groove 24N is referred to as a small block 26A, and the small blocks 26B, 26C, 26D, and 26E are sequentially attached from the small block 26A toward the wide lug groove side. Yes. The width J of the small block is a direction along the tire circumferential direction U.

(Function, effect)
Hereinafter, the operation and effect when the pneumatic tire 10 according to the present embodiment is mounted on the vehicle and travels on the ice road surface S will be described with reference to FIG. In the present embodiment, description will be given using blocks 26F and 26R located on both sides of the narrow lug groove 24N in the tire circumferential direction.

  As shown in FIG. 4, when the pneumatic tire 10 rotates and rolls on the ice road surface S, the block 26F on one side is grounded first, and then the block 26R on the other side is grounded. . Here, when both the block 26F and the block 26R are grounded, the small blocks of both blocks are deformed and inclined with respect to the ice road surface S. Of the small blocks constituting the block 26F, the small block 26AF located at the block kicking side end and the small block 26AR located at the block stepping side end among the small blocks constituting the block 26R come into contact with each other to block. The contact force between them acts.

  In this state, the blocks 26F and 26R support each other. Therefore, compared to the conventional case where each block is grounded alone, in this embodiment, the collapse deformation of the blocks 26F and 26R is suppressed. Therefore, by increasing the number of sipes 28 formed per block 26 in order to increase the amount of water absorption, the braking performance on ice can be sufficiently achieved even when the distance between sipes, that is, the width J of the small blocks is reduced. Can be improved. Moreover, this is realized even if the shape of the sipe 28 is a normal flat plate shape.

  In addition, since the narrow lug grooves 24N and the wide lug grooves 24W are alternately arranged in the tire circumferential direction U, the block 26 is more reliably prevented from falling.

  Further, the groove width BN of the narrow lug groove 24N is set to 20% or more and 40% or less of the groove width BW of the wide lug groove 24W. As a result, the performance balance between the wet brake (brake on the wet road surface) and the ice brake (brake on the ice top surface) is improved, and the performance of both is achieved to the target performance. The groove width BN of the narrow lug groove 24N is preferably in the range of 1 to 3 mm, and the groove width BW of the wide lug groove 24W is preferably in the range of 5 to 8 mm.

  In the present embodiment, the sipe 28 has a flat plate shape along the lug groove 24. However, the present invention is not limited to this, and the zigzag shape on the block surface or in the tire depth direction (block depth direction). The sipe may extend to Here, the sipe extending in a zigzag shape means that the sipe portions that are inclined with respect to the extending direction of the sipe extend while being folded back so that the inclined directions are alternated. A so-called three-dimensional sipe that extends in a zigzag shape on the block surface (particularly in the tire circumferential direction) and also extends in a zigzag shape in the block depth direction may be formed.

[Second Embodiment]
Next, a second embodiment will be described. In the pneumatic tire according to the present embodiment, as shown in FIGS. 5 and 6, the sipe 48 formed in the block 46 of the tread portion is different in formation position compared to the first embodiment.

  In the present embodiment, sipes 48 along the lug grooves 24 are formed in each block 46. Four sipes 48 are formed in each block 46, and each sipe 48 is formed along the tire width direction V. As shown in FIG. 5, the width J1 of the small block 46A adjacent to the narrow lug groove 24N is narrower than the width J2 of the small block 46E adjacent to the wide lug groove 24W. The width J1 of the small blocks 46A to 46C near the narrow lug groove 24N is the same narrow width, and the widths J2 of the small blocks 46D and 46E near the wide lug groove 24W are the same wide.

  According to the present embodiment, the small block 46E adjacent to the wide lug groove 24W is wide and has high rigidity. Accordingly, when the tire rolls, even if the small block 46E does not contact the block facing the tire circumferential direction U across the wide lug groove 24W, the collapse of the small block 46E is further suppressed than in the first embodiment. Yes.

  Further, since the small block 46D adjacent to the small block 46E is also wide and has high rigidity, the falling of the small block 46D is further suppressed.

  As shown in FIGS. 5 and 6, in this embodiment, the small blocks 46A to 46C close to the narrow-width lug groove 24N have the same narrow width, and the small blocks 46D close to the wide-width lug groove 24W. Although the example in which the width of 46E is the same wide width is given, the widths of the small blocks 46A to 46E are distributed so that they are wider as they are closer to the wide lug grooves 24W, and gradually narrower as they are closer to the narrow lug grooves 24N. May be. Thereby, the said effect is recognized more notably.

<Test example>
In order to confirm the effect of the present invention, the inventor has an example of a pneumatic tire according to the first embodiment (hereinafter referred to as a tire of Example 1) and an example of a pneumatic tire according to the second embodiment (hereinafter, referred to as “tire of tire”). Example 2) and an example of a conventional pneumatic tire (hereinafter referred to as a conventional tire) were prepared, and a braking performance test was performed on an icy road to evaluate the braking performance. In the conventional tire, as shown in FIG. 7, a block 86 is formed in the tread portion instead of the block 26. The conventional tire is not formed with a narrow lug groove, but is formed with a lug groove 84 having the same width.

  Regarding the lug groove width, in the tires of Examples 1 and 2, the groove width BN of the narrow lug groove 24N was 1.5 mm, and the groove width BW of the wide lug groove 24W was 6.5 mm. In the conventional tire, the groove width BP (see FIG. 7) of the lug groove 84 is 4 mm. Therefore, the total capacity of the lug grooves 24 in Examples 1 and 2 (the sum of the capacity of the narrow lug grooves 24N and the capacity of the wide lug grooves 24W) and the total capacity of the lug grooves 84 in the conventional tire are the same. It has become. Thereby, in the tires of Examples 1 and 2, the area on the tread surface side of the block is the same as that of the conventional tire, and the drainage performance from the lug groove 24 is equal to or more than that of the conventional tire. Has been.

  As for the block dimensions, in the tire of Example 1, as shown in FIG. 3, the tire circumferential direction length L is 25 mm, the tire width direction length M is 20 mm, and the tire radial direction depth (block height) H is 10 mm. The width J of the small blocks 26A to E is 5 mm, and the depth h of the sipe 28 is 8 mm. In the tire of the second embodiment, as shown in FIG. 6, the outer dimensions (values of L, M, and H) of the block 46 are the same as those of the tire of the first embodiment, and three small blocks 46A close to the narrow lug groove 24N. The width J1 of .about.C is 4 mm, and the width J2 of the two small blocks 46D and 46E close to the wide lug groove 24W is 6.5 mm. In the tire of the conventional example, the block size was made the same as that of the tire of Example 1. That is, the external dimensions of the block 86 (values of L, M, and H), the number of sipes 88, the width J of the small blocks 86A to 86E formed by the sipes 88, and the depth h of the sipes 88 are the values of the first embodiment. Same as tire.

  In this test example, for all tires, the tire size was set to 195 / 65R15, the tire was mounted on a regular rim, the internal pressure was set to 200 kPa, and the test was performed by running the vehicle in a state where it was attached to a passenger car and loaded with a regular load. Here, “regular rim” means, for example, a standard rim in an applicable size defined in the 2006 YEAR BOOK issued by JATMA, and “regular load” similarly refers to the 2006 YEAR issued by JATMA. It refers to the maximum load at the applicable size and ply rating specified in BOOK.

In this test example, the braking distance from the initial speed of 40 km / h until full braking was applied to the stationary state was measured, and the average deceleration was calculated from the initial speed and the braking distance. And the evaluation index based on the average deceleration of the tire of a conventional example was set to 100, and the evaluation index used as relative evaluation about the tire of Example 1, 2 was computed. The evaluation results are shown in Table 1.

  The evaluation results in Table 1 indicate that the larger the evaluation index, the higher the performance on ice, that is, the shorter the braking distance and the better the braking performance. As can be seen from Table 1, the evaluation index of the tire of Example 1 was higher than that of the conventional tire.

  Therefore, in the conventional tire, when the number of sipes 88 is increased, the block rigidity is greatly reduced and the contact area is reduced, and the braking performance on ice cannot be improved so much. In the tire of Example 1, It was found that the block rigidity can be increased and the braking performance on ice is greatly improved compared to the conventional tire. FIG. 8 shows a region Q in which the ground contact area is reduced in the conventional tire.

  In addition, the evaluation index of the tire of Example 2 is higher than that of the tire of Example 1, and it was found that the braking performance on ice is better than that of the tire of Example 1.

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

It is tire radial direction sectional drawing of the pneumatic tire which concerns on 1st Embodiment. It is explanatory drawing which shows the block arrangement of the tread part of the pneumatic tire which concerns on 1st Embodiment in a planar state. It is a perspective view of the block which constitutes the tread part of the pneumatic tire concerning a 1st embodiment (state where a block is located in the upper part of a tire). In a 1st embodiment, it is a typical partial side sectional view showing that a pneumatic tire rolls on an icy road surface. It is explanatory drawing which shows the block arrangement of the tread part of the pneumatic tire which concerns on 2nd Embodiment in a planar state. It is a perspective view of the block which constitutes the tread part of the pneumatic tire concerning a 2nd embodiment (state where a block is located in the upper part of a tire). It is explanatory drawing which shows the block arrangement of the tread part of the conventional pneumatic tire used by the test example in a planar state. It is typical partial side surface sectional drawing which shows that the conventional pneumatic tire used by the test example rolls on an ice road surface.

Explanation of symbols

10 Pneumatic tire 16 Tread portion 22 Circumferential groove 24 Lug groove 24N Narrow lug groove 24W Wide lug groove 26 Block 26F Block 26R Block 26A-E Small block 26AF Small block 26AR Small block 28 Sipe 46 Block 48 Sipe 46A-E Small Block 84 Lug groove 86 Block 88 Sipe BN Groove width BW Groove width J1 Width J2 Width

Claims (5)

A plurality of blocks partitioned by a circumferential groove and a lug groove are formed in the tread portion, and the block is a pneumatic tire in which a plurality of sipes are formed,
A pneumatic tire characterized in that a plurality of the lug grooves are narrow-width lug grooves.   Of the lug grooves, except for the narrow lug grooves, wide lug grooves are used, so that the two types of lug grooves, the narrow lug grooves and the wide lug grooves, are alternately arranged in the tire circumferential direction. The pneumatic tire according to claim 1, wherein   The pneumatic tire according to claim 2, wherein a groove width of the narrow lug groove is 20% or more and 40% or less of a groove width of the wide lug groove. A plurality of small blocks are formed in the block by the sipe,
The pneumatic tire according to claim 2 or 3, wherein a width of the small block adjacent to the wide lug groove is wider than a width of the small block adjacent to the narrow lug groove.   5. The air according to claim 4, wherein a width of a plurality of small blocks formed in the block by the sipe is wider as it is closer to the wide lug groove and is narrower as it is closer to the narrow lug groove. Tires.

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