JP4750398B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire with improved running performance, and more particularly to a pneumatic tire that is particularly suitable for use in trucks and buses.

  In pneumatic tires used for trucks, buses, etc., various improvements have been made to groove shapes and sipe shapes in order to improve running performance on wet road surfaces, icy road surfaces, snowy road surfaces, and the like (see, for example, Patent Document 1). ).

  By the way, from the viewpoint of securing block rigidity, the block structure is such that sipes gradually disappear when the tire wears beyond 50% wear. Accordingly, the negative rate decreases as the wear amount approaches the upper limit of the allowable wear amount, and there is a problem that the wet road surface performance is not sufficiently ensured. In this specification, the state of 50% wear means a state in which the groove depth of the deepest groove is 50% of the depth of a new article.

  In addition, it is effective to form many sipes to improve the performance on ice. However, if many sipes are formed, block durability and uneven wear resistance tend to be reduced. I can't do it. For this reason, there also existed a problem that performance on ice could not be improved so much.

These problems have been particularly noticeable in pneumatic tires used for trucks and buses.
JP 2002-321509 A

  In view of the above fact, an object of the present invention is to provide a pneumatic tire with further improved running performance.

The invention according to claim 1 is defined by four main grooves provided in the tread portion and extending in the tire circumferential direction, and lug grooves that intersect the main grooves and that are sequentially shifted in phase in the tire width direction. A plurality of blocks formed, and provided on the outside in the tire width direction of the plurality of blocks, and having a narrow groove extending in the tire circumferential direction at a tread end position, thereby forming a shoulder portion in the tire width direction, have a, a tire width direction outer block is composed of a main groove side block unit constituting the tread portion, a main groove side block portion of the block and the tire width direction outer block, along the lug grooves Three or more sipes are formed, and the sipes on both outer sides in the tire circumferential direction are closed sipes, and the sipes located between the closed sipes are open. The sipe surface of the closed sipe and the open sipe is a flat plate shape or a bent surface shape in which one or more bent portions are formed, and the sipe depth of the closed sipe and the open sipe is It is ½ or more of the depth of the main groove, the sipe length of the closed sipe is ½ or more of the block width of the block, and in the tire width direction outer block portion of the tire width direction outer block, A circumferential sipe along the tire circumferential direction is formed, and the lug groove that is open at the tread end of the lug groove formed in the tread portion and the lug groove formed in the shoulder portion are in phase. It is formed by .

In the first aspect of the invention, of the sipes formed on the main groove side block portion of the block and the tire width direction outer block, the sipes on both outer sides in the tire circumferential direction are closed sipes and are located between the closed sipes. Since the sipe is an open sipe, the running performance can be improved by increasing the edge component. The sipe surface of the closed sipe and the open sipe is a flat plate shape or a bent surface shape in which one or more bent portions are formed, and the sipe depth of the closed sipe and the open sipe is 1 of the depth of the main groove. Since the sipe length of the closed sipe is ½ or more of the block width of the block, sufficient block rigidity can be ensured. Therefore, it is possible to provide a pneumatic tire that achieves both improvement in running performance and securing of block rigidity. In the present specification, the sipe length refers to the length between both ends of the sipe along the sipe longitudinal direction.

  Moreover, since the number of main grooves is four, the negative ratio in the tire circumferential direction can be increased, and drainage performance can be ensured.

When the tire rolls on the snow, the snow is compressed by a lug groove between the blocks to generate a snow column shear force, thereby generating a traction force on the snow. In the conventional pneumatic tire, since at least a part of the lug grooves are formed in the same phase in the tire width direction, there is a problem that the snow column shear force is discontinuous (non-uniform). In the first aspect of the invention, the lug grooves formed in the tread portion are sequentially shifted in the tire width direction in this way, so that the snow column shear force is generated continuously (that is, uniformly). Can do.

The tire width direction outer side block straddles the shoulder part and the tread part, and has a narrow groove extending in the tire circumferential direction at the tread end position, so that the tire width direction outer side block part constituting the shoulder part, and the tread In addition to the main groove side block portion constituting the portion, a circumferential sipe along the tire circumferential direction is formed in the tire width direction outer block portion. Furthermore, the lug groove opened at the tread end among the lug grooves formed in the tread portion and the lug groove formed in the shoulder portion are formed in the same phase. As a result, when running on a snowy road surface, the snow in the lug groove opening at the tread end can be smoothly discharged to the outside in the tire width direction, and the friction reduction between the tread part and the snowy road surface is sufficiently prevented. Can be prevented.

  The tread end means that a pneumatic tire is mounted on a standard rim specified in JATMA YEAR BOOK (2002 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, in the main groove side block portion of the outer block in the tire width direction and the block, two closed sipes and one open sipe are formed, and the closed Both the sipe and the open sipe extend in a zigzag shape.

  The sipe extending in a zigzag shape means that the sipe portion is continuously formed so that the sipe is folded with the inclination direction being alternated with respect to the sipe extending direction.

According to the second aspect of the invention, the effect of the first aspect of the invention can be easily achieved.

  According to the present invention, it is possible to realize a pneumatic tire with further improved running performance.

  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 pneumatic tire used for buses and trucks, and includes a carcass 12 extending in a toroid form from a pair of bead cores 11, and a crown of the carcass 12. A belt 14 provided on the outside of the belt portion, and a tread portion 16 provided on the outside of the belt 14 and continuous in a toroidal manner between the sidewall portions.

  As shown in FIG. 2, central main grooves 20 </ b> L and 20 </ b> R that are symmetrical with respect to the tire equatorial plane CL and extend in the tire circumferential direction are formed in the central region 19 of the tread portion 16. Shoulder main grooves 22L and 22R extending in the tire circumferential direction are formed on the outer sides in the tire width direction of the central main grooves 20L and 20R, respectively. Thus, the four main grooves along the tire circumferential direction are formed in the tread portion 16. In the present embodiment, the four main grooves have the same depth.

A number of lug grooves 24 are formed in the tread portion 16. Both ends of the lug groove 24 are opened in two of the four main grooves, respectively. As a result, a large number of blocks 26 defined by the main groove and the lug groove are formed in the tread portion 16, and the large number of blocks 26 form three block rows 28.

  In this embodiment, the tire circumferential direction position of the lug groove 24 is sequentially shifted for each block row, and the lug groove having the same tire width direction position is not formed.

  In each block 26, three sipes 30 are formed along the lug grooves 24. Two sipes 30C located on both outer sides in the tire circumferential direction of the sipes 30 are closed sipes. One sipe 30M located between the closed sipes is an open sipe, and both ends are open to the block wall surface 26W.

  The sipes 30C and 30M both extend in a zigzag shape, and the sipe surfaces of the sipe 30C and 30M are surfaces that extend in a zigzag shape in which surfaces having different inclination directions are alternately arranged. The sipe depth of the sipe 30C, 30M is ½ or more of the depth of the main groove, and the sipe length L of the sipe 30C is ½ or more of the block width B of the block 26.

Further, the blocks 26E as the outer blocks in the tire width direction constituting the block rows 28E located on both outer sides in the tire width direction of the three block rows 28 are formed across the shoulder portion 34 and the tread portion 16. The narrow groove 38 extending in the tire circumferential direction is formed at the position of the tread end T of the block 26E, so that the block 26E has a tire width direction outer side block portion 40 constituting the shoulder portion 34, and a tread portion. 16 is formed with a main groove side block portion 42 that constitutes 16. In the main groove side block portion 42, two sipes 30C and one sipes 30M are formed in the same manner as the other blocks 26.

  A circumferential sipe 43 is formed in the tire width direction outer side block portion 40 along the tire circumferential direction. Of the lug grooves 24 formed in the tread portion 16, the lug grooves 24 </ b> E opening at the tread end T and the lug grooves 44 formed in the shoulder portion 34 are formed in the same phase.

  As described above, in the present embodiment, two sipe 30Cs on both outer sides in the tire circumferential direction of the sipe 30 are closed sipes, and one sipe 30M located between the closed sipes is an open sipe. Therefore, running performance such as on-ice performance can be significantly improved by increasing the edge component.

  In addition, the sipe surfaces of the sipe 30C and 30M are zigzag-like surfaces in which surfaces having different inclination directions are alternately extended, and the sipe depth of the sipe 30C and 30M is 1 of the depth of the main groove. The sipe length of the sipe 30C is ½ or more of the block width of the block 26. Therefore, the block rigidity can be sufficiently ensured, and the block durability and uneven wear resistance are improved. Thereby, it can be set as the pneumatic tire 10 which made the improvement of running performance and ensuring block rigidity compatible.

  Furthermore, since the number of main grooves is four, the negative ratio in the tire circumferential direction can be increased, and drainage performance can be ensured.

  Further, since the phase in the tire width direction of the lug grooves 24 formed in the tread portion 16 is sequentially shifted, a snow column shear force can be generated continuously (that is, uniformly).

  Further, since the lug groove 24E opened at the tread end T and the lug groove 44 formed in the shoulder portion 34 are formed in the same phase, this allows the tread end T when traveling on a snowy road surface. The snow in the lug groove 24 </ b> E opening in the tire can be smoothly discharged to the outside in the tire width direction via the lug groove 44, and the friction reduction between the tread portion 16 and the road surface on snow is sufficiently prevented. be able to.

<Experimental example>
The inventor first performed a performance test using a new (unused) conventional pneumatic tire (11R22.5 W980Z).

  As test conditions, the vehicle weight was 20 t (2-D4 as a vehicle), the rim size was 22.5 × 7.50, the air pressure was 900 kPa, and the load was a normal load.

  Then, (1) turning performance on a wet road surface, (2) braking performance on ice, and (3) traction performance on snow were measured, and the index was 100 as a reference value. This index is shown in Table 1.

（１）ウェット路面での旋回性能試験では、コンクリート路面上で水深２ｍｍの水膜が形成されたウェット路面とし、旋回加速度を測定することにより行った。（２）氷上ブレーキ性能試験では、アイス路面（氷上路面）で減速度を測定することにより行った。（３）雪上トラクション性能試験では、雪上路面で発進時の加速度を測定することにより行った。

(1) The turning performance test on the wet road surface was performed by measuring the turning acceleration on a wet road surface in which a water film having a water depth of 2 mm was formed on the concrete road surface. (2) In the on-ice brake performance test, the deceleration was measured on the ice road surface (ice surface). (3) The snow traction performance test was performed by measuring the acceleration at the start on the snowy road surface.

  In addition, the present inventor uses a pneumatic tire 10 according to the above-described embodiment, which has the same standard and dimensions as the pneumatic tire of the above-described conventional example (hereinafter referred to as the pneumatic tire of the example). The performance test was performed under the same conditions as the conventional pneumatic tire. And the index | index used as the relative evaluation with respect to the pneumatic tire of the said new conventional example was computed about said three items. The calculated index is also shown in Table 1. Table 1 shows that the larger the index, the better the performance.

  As can be seen from Table 1, the new example pneumatic tires were evaluated better than the new conventional pneumatic tires for all items.

  Furthermore, the present inventor puts the pneumatic tire of this example into a 50% worn state, performs a performance test under the same conditions on the turning performance on the wet road surface, and evaluates relative to the new conventional pneumatic tire. An index was calculated.

  For comparison, the pneumatic tire of the above-mentioned conventional example is put into a state of 50% wear, a performance test is performed on the turning performance on the wet road surface under the same conditions, and the relative evaluation with respect to the new conventional pneumatic tire is performed. An index was calculated. These calculated indices are also shown in Table 1.

  As can be seen from Table 1, the turning performance on the wet road surface of the pneumatic tire of the above example in the state of 50% wear is far better than the pneumatic tire of the conventional example in the state of 50% wear. The result was.

  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 which shows the tread part of the pneumatic tire which concerns on one Embodiment of this invention.

Explanation of symbols

10 Pneumatic tire 16 Tread portion 20L Central main groove (main groove)
20R Central main groove (main groove)
22L Shoulder main groove (main groove)
22R Shoulder main groove (main groove)
24 lug groove 24E lug groove 26 block 26E block 30 sipe 30C sipe (closed sipe)
30M Sipe (Open Sipe)
34 Shoulder portion 38 Narrow groove 40 Tire width direction outer side block portion 42 Main groove side block portion 43 Circumferential sipe 44 Lug groove

Claims (2)

A number of blocks defined by four main grooves provided in the tread portion and extending in the tire circumferential direction; and lug grooves that intersect the main grooves and that are sequentially shifted in phase in the tire width direction ;
A tire width direction outer side block part which constitutes a shoulder part, and a main groove which constitutes the tread part by having narrow grooves extending in the tire circumferential direction at the tread end position, provided on the tire width direction outer side of the multiple blocks A tire width direction outer block composed of a side block portion, and
I have a,
Three or more sipes along the lug groove are formed on the main groove side block portion of the block and the tire width direction outer block ,
The sipe on both outer sides in the tire circumferential direction is a closed sipe,
Sipes located between the closed sipes are open sipes,
The sipe surface of the closed sipe and the open sipe is a flat plate shape or a bent surface shape in which one or more bent portions are formed,
The sipe depth of the closed sipe and the open sipe is ½ or more of the depth of the main groove,
The sipe length of the closed sipe is ½ or more of the block width of the block,
In the tire width direction outer block portion of the tire width direction outer block, a circumferential sipe along the tire circumferential direction is formed,
A pneumatic tire characterized in that a lug groove opened at a tread end of the lug groove formed in the tread portion and a lug groove formed in the shoulder portion are formed in the same phase. . The main groove side block portion of the outer block in the tire width direction and the block are both formed with two closed sipes and one open sipe,
The pneumatic tire according to claim 1 , wherein both the closed sipe and the open sipe extend in a zigzag shape.

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