JP2007106314A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing the on-snow/on-ice running performance over a long time from the initial stage of use. <P>SOLUTION: A plurality of block rows 24 and rib rows 26 are formed by main grooves 20 extending in the tire circumferential direction and lug grooves 22 extending in the tire width direction on a tire tread part 16 of a pneumatic radial tire 10. A shoulder main groove 20S constituting the main groove 20 demarcates the tire tread part 16 into a center area 28 and a shoulder area 30. In the center area 28, sipes 36 extending in the tire width direction are provided in the block rows 24 and the rib rows 26. In the shoulder area 30, a bottom-raised part 32 in which the depth of the outer lug groove 22E is set to be not less than 40% of the depth of the shoulder main groove 20S is formed in a bottom of the outer lug groove 22E. A lug groove sipe 34 is formed in the bottom-raised part 32. In the center area 28, a shallow sipe 38 for connecting the sipes 36 extending in the tire width direction is formed, and the shallow sipe 38 extends in the tire circumferential direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an all-weather pneumatic tire, and more particularly to a pneumatic tire with improved performance when used under winter driving conditions.

  All-weather pneumatic tires that can run not only on normal road surfaces but also on ice and snow are used.

  In this all-weather pneumatic tire, as a technique to improve the performance on ice and snow, the frictional force is increased by increasing the contact surface area, and the edge component is increased by increasing the number and density of sipes, and the digging effect is increased. It is possible to take measures such as increasing (see, for example, Patent Documents 1 to 5). In particular, it is effective to remove the water film that appears on the ground surface on ice near 0 ° C. For this purpose, it is effective to increase the sipe density.

  However, if the sipe density is increased too much, the block rigidity is lowered, and uneven wear occurs. At the same time, the contact surface area is reduced due to the bending deformation of the block, and the performance on ice and snow is rather lowered. As a method of increasing the edge component by increasing the number and density of sipes, it is conceivable to increase the ground contact area of each block and reduce the non-ground portion, but this is not desirable from the viewpoint of drainage. Thus, there is a limit to improving the performance on ice and snow by increasing the sipe density.

  Therefore, in recent years, it has been proposed to improve the performance on ice and snow without affecting the block rigidity by adding a shallow sipe to the groove bottom (see, for example, Patent Document 6). In this proposal, a sipe is formed at the groove bottom of the lug groove to facilitate the opening of the lug groove. With this configuration, since the lug groove opens from the groove bottom of the sipe, it is easier to open than a shallow lug groove, and snow clogging in the lug groove can be prevented. That is, by making the lug groove shallower, the snow that has entered the lug groove is brought into contact with the groove bottom of the lug groove and hardened, so that the shear rigidity of the snow that has entered the lug groove can be increased and the traction performance can be improved. Yes.

However, since this sipe added to the groove bottom of the lug groove is shallow, it disappears with a short traveling distance, and it is difficult to exhibit its performance over a long period of time.
JP 2000-108615 A JP-A-8-40021 JP-A-8-169212 Japanese Patent Laid-Open No. 10-86613 JP 2002-347413 A JP 2001-187517 A

  In view of the above facts, an object of the present invention is to provide a pneumatic tire with improved performance on ice and snow over a long period from the initial use.

  Normally, the tire stiffness distribution is higher toward the center, and conversely lower at the shoulder. For this reason, at the time of cornering or the like, the steering stability is lowered by the change in rigidity.

  As a result of intensive studies, the present inventor has improved the rigidity of the shoulder portion having low rigidity by raising the width direction groove (lug groove) of the shoulder portion, thereby making the rigidity of the tire itself uniform and improving steering stability. While improving, I came up with the idea of adding a sipe to the bottom of the raised groove. The present inventor has further studied, repeated experiments, and completed the present invention.

  In the first aspect of the present invention, a plurality of block rows or rib rows are formed on the tire tread surface portion by a plurality of main grooves extending substantially in the tire circumferential direction and a plurality of lug grooves extending substantially in the tire width direction. The main groove is a pair of main grooves that sandwich the tire equator, and includes a shoulder main groove that divides the tire tread portion into a central region and a shoulder region, and at least the central region extends in a substantially tire width direction. A plurality of sipes are pneumatic tires provided in the block row or the rib row, and in the shoulder region, the depth of the lug groove is 40% or more of the groove depth of the shoulder main groove. A portion is formed at the groove bottom of the lug groove, and at least one sipe is provided at the bottom raised portion, and at least one shallow sipe connecting the sipe in the central region is the block row. It is formed on the rib rows, and the shallow sipes is characterized in that it extends substantially the tire circumferential direction.

  The substantially tire circumferential direction is a direction extending toward the tire meridian, and the tire width direction is a direction extending toward the tire equator line.

  The plurality of main grooves extending substantially in the tire circumferential direction may extend in a zigzag shape in the tire circumferential direction. The phrase “zigzag extending in the tire circumferential direction” means that the groove portions that are inclined with respect to the tire circumferential direction extend in the tire circumferential direction while turning back so that the inclination directions are alternate.

  In the first aspect of the present invention, since the bottom raised portion is formed in which the groove depth of the lug groove is 40% or more of the groove depth of the shoulder main groove, it is possible to improve the steering stability during normal traveling. it can. In addition, since ice and snow enter the bottom of the raised lag groove during ground contact on the snow, the sipe formed at the raised bottom in the lag groove greatly contributes to the improvement of the performance on the snow. That is, the number of functioning sipes is greatly increased and the edge components are increased, so that the performance on snow is greatly improved. Moreover, since the sipe arranged in the lug groove is hard to disappear even if the tire is used for a long time, the performance of the sipe arranged in the raised portion in the lug groove can be continued.

  In addition, the edge component in the circumferential direction is increased by the shallow sipe that connects the sipe provided in the tire width direction to the ribs and blocks in the tire center area, so it is effective against lateral slip. Is.

  Thus, by forming both the shallow sipe and the sipe in the lug groove raised to the bottom, it is possible to obtain a pneumatic tire having improved performance on ice and snow for a long period from the initial use.

  In addition, it is preferable that the depth of the lug groove is 60% or less of the depth of the shoulder main groove since drainage can be secured.

  The invention according to claim 2 is characterized in that the depth of the sipe deepest portion of the sipe formed in the block, the rib, and the bottom raised portion is the same depth as the main groove. To do.

  The depth equivalent to the main groove means that the distance from the tire tread is almost equal.

  According to the second aspect of the present invention, since the sipe in the lug groove has a depth that opens when rolling, clogged snow can be discharged efficiently.

  The invention described in claim 3 is characterized in that a sipe depth of the shallow sipe is in a range of 1 to 3 mm.

  If the depth of the shallow sipe is less than 1 mm, it will disappear due to wear in a short period of time, and it is not preferable if it is deeper than 3 mm, because it causes uneven wear due to the reduction in the rigidity of the block.

  According to the third aspect of the present invention, by forming the shallow sipe, it is possible to surely improve the performance on ice and snow over a long period of time without causing a decrease in block rigidity.

  The invention described in claim 4 is characterized in that the sipe depth of the shallow sipe is not uniform throughout the tire.

  Thereby, even if the wear of the shallow sipe progresses, the effect of improving the performance on ice and snow can be prolonged.

  According to the present invention, it is possible to realize a pneumatic tire having improved performance on ice and snow over a long period from the initial use.

  Hereinafter, embodiments will be described and embodiments of the present invention will be described. As shown in FIG. 1, a pneumatic radial tire 10 according to an embodiment of the present invention is an all-weather tire including a carcass 12 whose both ends are folded back by bead cores 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 ply belt is overlapped is embedded. A tire tread surface portion 16 is formed on the outer side of the belt layer 14 in the tire radial direction.

  As shown in FIG. 2, the tire tread surface portion 16 includes a plurality of block rows 24 and a plurality of main grooves 20 extending substantially in the tire circumferential direction and a plurality of lug grooves (lateral grooves) 22 extending substantially in the tire width direction. A rib row 26 is formed. The main groove 20 includes a shoulder main groove 20S that is a pair of main grooves sandwiching the tire equator CL and that partitions the tire tread surface portion 16 into a central region 28 and a shoulder region 30. The lug groove 22 includes an inner lug groove 22I located on the inner side in the tire width direction of the shoulder main groove 20S and an outer lug groove 22E located on the outer side in the tire width direction of the shoulder main groove 20S.

  The outer lug groove 22E extends from the tread end T to the shoulder main groove 20S. Here, the tread end means that a pneumatic tire is mounted on a standard rim prescribed in JATMA YEAR BOOK (2004 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.

  And in the shoulder region 30, the bottom raising part 32 which makes the groove depth of the outer side lug groove 22E 40% or more of the groove depth of the shoulder main groove 20S is formed in the outer side lug groove 22E. The bottom raised portion 32 is formed with a sipe 34 (hereinafter referred to as a lug groove sipe 34) that extends substantially in the tire radial direction from the groove bottom. As can be seen from FIG. 3, the depth of the lug groove sipe 34 is set to a depth equivalent to the bottom surface of the outer lug groove portion where the bottom raised portion 32 is not formed.

  A plurality of sipes 36 extending substantially in the tire width direction and shallow sipes 38 connecting the sipes 36 are formed in the central region 28 in each block 25 and rib row 26 constituting the block row 24. Yes. The depth of the sipe 36 extending substantially in the tire width direction is deeper than the lug groove sipe 34, and the depth of the deepest portion of the sipe 36 is equal to the depth of the shoulder main groove 20S (see FIG. 4). On the other hand, the shallow sipe 38 extends substantially in the tire circumferential direction. And the depth of this shallow sipe 38 is non-uniform in the whole tire, and the depth value is made into multiple values.

  In the present embodiment, since the groove depth of the outer lug groove 22E is raised to 40% or more of the groove depth of the shoulder main groove 20S, steering stability during normal traveling can be improved. In addition, since ice and snow enter the bottom of the raised outer lug groove 22E at the time of ground contact on the snow, the lug groove sipe 34 also greatly contributes to the improvement of the snow performance. That is, the number of functioning sipes is greatly increased and the edge components are increased, so that the performance on snow is greatly improved. Further, since the lug groove sipe 34 is hard to disappear even if the tire is used for a long time, the performance of the lug groove sipe 34 can be continued. In addition, since the shallow sipe 38 is formed in the block row 24 and the rib row 26 in the central area 28 and the edge component in the circumferential direction is increased, it is effective for the slip in the lateral direction.

  Thus, by forming both the shallow sipe 38 and the lug groove sipe 34, it is possible to obtain a pneumatic tire having improved performance on ice and snow for a long period from the initial use.

  Moreover, since the depth of the deepest part of the sipe 36 is the same depth as the main groove 20, a sipe opens at the time of rolling, and clogged snow can be discharged | emitted.

  Furthermore, since the sipe depth of the shallow sipe 38 is in the range of 1 to 3 mm, it does not disappear due to wear in a short period of time, and it does not cause uneven wear due to block rigidity reduction. It is possible to reliably realize improvement in performance on ice and snow over a period of time.

  In addition, since the sipe depth of the shallow sipe 38 is not uniform throughout the tire, even if the wear of the shallow sipe 38 progresses, the effect of improving performance on ice and snow can be prolonged.

<Test example>
The inventor has three examples of the pneumatic radial tire 10 according to the above embodiment (hereinafter referred to as a tire of Example 1, a tire of Example 2, and a tire of Example 3), and an example of a conventional pneumatic radial tire. (Hereinafter referred to as conventional tires) and comparative pneumatic pneumatic tires (hereinafter referred to as comparative tires) are tested for snow braking performance, snow traction performance, and dry steering stability. went. Table 1 shows the tire conditions for each tire.

試験条件は、以下のような共通条件とした。

The test conditions were the following common conditions.

Tire size: 225 / 45R17
Rim size: 8J x 17 inches Tire pressure: 250kPa
Load: 450kgf
In this test example, the evaluation for the tire of the conventional example was taken as index 100, and the index for relative evaluation was calculated for the other tires (tires of Examples 1 to 4). The evaluation results are also shown in Table 1. Table 1 shows that the higher the index, the better the performance.

  As can be seen from Table 1, in the tires of Examples 1 to 3, the snow braking performance, snow traction performance, and dry steering stability were all improved as compared with the conventional tires. Moreover, in the tire of the comparative example, the dry steering stability was improved as compared with the tire of the conventional example, but the snow braking performance and the snow traction performance were lowered.

  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.

It is a tire radial direction sectional view of a pneumatic radial tire concerning one embodiment of the present invention. 1 is a partial plan view of a pneumatic radial tire according to an embodiment of the present invention. It is a typical tire width direction sectional view of a pneumatic radial tire concerning one embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows the structure of the sipe formed in the block with the pneumatic radial tire which concerns on one Embodiment of this invention. (The sipe extended zigzag in the direction parallel to a cross section is drawn in a simplified and planar state. )

Explanation of symbols

10 pneumatic radial tire 16 tire tread 20 main groove 20S shoulder main groove 22 lug groove 22I inner lug groove 22E outer lug groove 24 block row 25 block 26 rib row 28 central region 30 shoulder region 32 bottom raised portion 34 lug groove sipes (at least One sipe)
36 Sipe 38 Shallow Sipe CL Tire Equator

Claims (4)

A plurality of block rows or rib rows are formed in the tire tread surface portion by a plurality of main grooves extending substantially in the tire circumferential direction and a plurality of lug grooves extending substantially in the tire width direction, and the main grooves sandwich the tire equator. A pair of main grooves, including a shoulder main groove that divides the tire tread portion into a central region and a shoulder region, and at least the central region includes a plurality of sipes extending substantially in the tire width direction. A pneumatic tire provided in a row of ribs,
In the shoulder region, a bottom raised portion that makes the groove depth of the lug groove 40% or more of the groove depth of the shoulder main groove is formed in the groove bottom of the lug groove, and at least one of the bottom raised portions Sipes are provided,
In the central region, at least one shallow sipe that connects the sipe is formed in the block row or the rib row, and the shallow sipe extends in a substantially tire circumferential direction. .   2. The pneumatic according to claim 1, wherein a depth of a sipe deepest portion of the sipe formed on the block, the rib, and the bottom raising portion is equal to the depth of the main groove. tire.   The pneumatic tire according to claim 1 or 2, wherein a sipe depth of the shallow sipe is in a range of 1 to 3 mm.   The pneumatic tire according to any one of claims 1 to 3, wherein the sipe depth of the shallow sipe is not uniform throughout the tire.

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