JP3148420B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in preventing uneven wear occurring at a rib end sandwiched between a vertical groove or a vertical groove and a shoulder contact end in a pneumatic radial tire having a rib pattern.

[0002]

2. Description of the Related Art Uneven wear in a tire of this type having a rib pattern is mainly caused by step wear starting from a shoulder contact end and river wear occurring at rib ends on both sides of a vertical groove.

Conventionally, step wear has conventionally been provided with a circumferential narrow groove at the shoulder contact end to prevent uneven wear. For the riverware, a straight vertical groove from which zigzag or irregularities are removed has been used since the riverware is formed starting from a point of particularly low rigidity at the end of the rib.

[0004]

However, the linear groove has problems in braking performance and driving performance when traveling on a wet road, and is not sufficient as a method for preventing generation of riverware. As a countermeasure, a method of installing a large number of sipes extending in the tire width direction at the rib end at small intervals in the tire circumferential direction is also provided for the purpose of preventing riverware, but in any case, it is a perfect measure for riverware. It is hard to say.

An object of the present invention is to provide a pneumatic radial tire that can effectively prevent riverware generated at rib ends on both sides of a vertical groove.

[0006]

SUMMARY OF THE INVENTION Since a straight vertical groove generally has a V-shaped cross section to prevent biting of stones, the base of the rib is wider than the ground contact surface. This means that when the ribs touch the ground, they bend due to the vertical force under load, and when the groove wall swells outward, the ribs tend to swell on the ground surface side where the rib width is smaller than the groove bottom, and the rubber movement of the ribs occurs on the ground surface side It becomes easier.
In addition, the movement of the rubber inside the rib itself is accumulated at the rib end, so that the movement of the rubber in the plane of the rib is the largest, and as a result, the rib end is moved more in the tire width direction on the rib surface than in other parts. become. It is well known that this widthwise movement lowers the coefficient of friction of the frictional force against tire circumferential slip, and as a result,
The rib ends are likely to slip in the tire circumferential direction, which is considered to be the cause of the occurrence of riverware.

Accordingly One that reducing the width direction of movement of the rib ends to prevent the occurrence of uneven wear from the rib end
It goes . To this end, it is conceivable to make the cross section of the rib base side smaller than that of the front side and make the cross section of the rib inverted trapezoidal. When the cross-sectional area on the rib base side is smaller than that on the front side, the movement in the width direction at the rib end on the front side can be relatively reduced for the same load. That is, the lowering of the coefficient of friction against the circumferential slip at the rib end is reduced.

However, when the cross section of the rib is inverted trapezoidal, the vertical groove has a pot-shaped cross-section, which tends to cause biting of stones and foreign substances, and also causes permanent deformation such as narrowing of the vertical groove opening due to a load. There are problems that can easily arise.

The present invention has been made in view of the above findings, and has a plurality of linear vertical structures connected in the tire circumferential direction and a plurality of vertical structures between the plurality of vertical grooves.
Between the rib or the vertical groove and the shoulder
In a pneumatic radial tire having a rib inserted,
On the groove walls of the pair of vertical grooves sandwiching the rib, a notch whose width and depth is widened toward the groove bottom of the vertical groove is formed, and at the valley of the notch, the ridgeline of the valley is formed with respect to the tread surface. A pneumatic radial tire having an inversely sloped portion in which the width of the groove is inclined at an angle θ with respect to the normal line N and widens toward the groove bottom is employed.

The angle θ formed by the ridgeline of the cut valley and the normal N is not particularly limited, but the angle θ is preferably about 0 to 30 °. This is because when the angle θ exceeds 30 °, stones and foreign matter are likely to be caught, and when the angle θ is negative, the inclination angle of the groove wall surface depends on the size of the rib surface and the base.
In some cases, a sufficient decrease in rigidity cannot be obtained with the side .

The cross-sectional area of the rib in a plane parallel to the tire tread surface and passing through the rib base side, that is, the groove bottom side, is set within a range of at least 1/2 of the groove depth to the groove bottom.
It is desirable that the cross-sectional area be equal to or smaller than the cross-sectional area of the rib on the surface side of the tread portion . This is to further ensure that the movement of the rubber on the rib base side is smaller than that on the tire tread surface surface side of the rib.

[0012]

According to the present invention, a notch whose width and depth are widened toward the bottom of the vertical groove is formed in the groove wall of the vertical groove, and the ridge line of the valley is formed on the tread surface at the valley of the notch. A conventional tire having a trapezoidal overall rib cross-section because an inclined portion is formed at an angle θ with respect to the normal N to the groove wall, and is inclined in a direction in which the width of the vertical groove is widened, opposite to the inclination of the groove wall. Unlike this, since it is equivalent to a structure having a rectangular or inverted trapezoidal rib cross section, the movement of the rubber on the rib surface side can be made equal to or less than the movement of the rubber on the base side. . Further, since the entire rib cross section is not an inverted trapezoidal shape, there is no risk of settling or stone biting.

Therefore, the movement of the rubber in the width direction of the tire tread portion at the rib surface, particularly at the end of the rib can be reduced without causing stone biting or biting of foreign matter, thereby reducing the friction coefficient against the tire circumferential slip. It is possible to prevent step-like wear (river wear) at the rib end as in the related art.

[0014]

FIG. 1 is a schematic diagram of a rib pattern showing an embodiment of a pneumatic radial tire according to the present invention.
FIG. 3 is an enlarged perspective view of an essential part near a vertical groove of the tire, and FIG. 3 is a cross-sectional view taken along line AA in FIG.

In the figure, 1 is a tread portion, 2 is a shoulder contacting end, and a vertical groove 3 is formed in the tread portion 1 continuously in the tire circumferential direction. Reference numeral 4 denotes a rib sandwiched between the frames 3, 3, and reference numeral 5 denotes a shoulder rib sandwiched between the groove 3 and the shoulder grounding end 2. Reference numeral 6 denotes a narrow groove provided in the tire circumferential direction on the shoulder contact end 2 side of the shoulder rib 5. Reference numeral 7 denotes a notch formed on the inclined surface of the groove wall 8 of the vertical groove 3. In this embodiment, the opening end 9 of the vertical groove 3 to the tire tread portion starts from the opening end 9 toward the groove bottom 10 of the vertical groove 3. It is formed in a state where the width and depth are widened. In this embodiment, the ridges 11 and the valleys 12 of the zigzag cuts 7 that face each other with the vertical groove 3 interposed therebetween face to face and form a pair.
N indicates the normal to the curved surface of the tread surface, and H indicates the depth of the vertical groove 3. 13 is the ridge line R of the valley 12 is the normal line N
In contrast to the inclination of the groove wall 8 at an angle .theta., It is an inversely inclined portion inclined in the direction in which the groove width of the vertical groove 3 is widened.

Therefore, the shear stress on the rib base side B is changed to the surface side S
Can be equal to or less than the shear stress of the tire, reduce the movement of rubber at the rib edge, reduce the coefficient of friction against tire circumferential slip, and prevent step-like wear (riverware) Is what you can do.

FIG. 4 is an enlarged sectional view of a main part showing another embodiment. This embodiment differs from the above embodiment in that the reverse inclined portion 14 is not formed in the entire range of the valley portion 12 ,
The vertical groove 3 is formed from the middle of the groove depth toward the groove bottom 10.

FIG. 5 is an enlarged cross-sectional view of a main part of a tire in which a reversely inclined portion 15 is formed on the ridge 11 of the vertical groove 3 from the middle of the groove wall 8 toward the groove bottom 10.

Next, the tire size 11R22. Each of the four tires of Example 5 was used as a front tire of a 2-DD type trailer. S. A was run on a dedicated road of A in a constant volume condition (running distance of 24000 km or more per 1 mm of tread rubber), and the wet road braking performance and uneven wear resistance were evaluated.
For comparison, a conventional tire (Comparative Example 1) shown in FIG. 6 having no reversely inclined portion and a tire (Comparative Example 2) having an angle θ of 35 ° with the normal N were similarly evaluated. Table 1 shows the results. In FIG. 6, reference numeral 16 denotes a tread portion, 17 denotes a vertical groove, 18 denotes a rib, and 19 denotes a sipe.

The braking performance of the wet road braking performance of Comparative Example 1 was 10
It was compared with 0 and indicated by an index. Comparative Example 1 for uneven wear resistance
The size (w × d) at the time of 30% wear of the riverware of the tire was expressed as an index with 100 being set. The smaller the value, the better. Note that w indicates the width of uneven wear and d indicates the same depth (see FIG. 7).

[0021]

[Table 1]

From Table 1, it can be seen that the tire of the present invention has better wet road braking performance and uneven wear resistance than the conventional tire (Comparative Example 1). Just angle θ is 3
If it exceeds 0 °, chipping occurs at the zigzag peaks and cracks occur at the valleys.

[0023]

According to the present invention, a notch is formed on the groove wall of the vertical groove so that the width and depth of the vertical groove increase toward the groove bottom, and the ridgeline of the valley is stepped on the valley of the cut. Since the reverse inclined portion was formed at an angle θ with respect to the normal line N to the surface of the surface and inclined in the direction in which the groove width of the vertical groove was widened, opposite to the inclination of the groove wall, the entire rib cross section was trapezoidal. Unlike conventional tires, it has a structure that partially retains the inverted trapezoidal rib cross section, so there is no risk of permanent deformation at the opening of the vertical groove, and no stepping at the rib end Wear (riverware) can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic view of a rib pattern showing one embodiment of a pneumatic radial tire according to the present invention.

FIG. 2 is an enlarged perspective view of a main part near a vertical groove of the tire.

FIG. 3 is a sectional view taken along line AA in FIG. 1;

FIG. 4 is an enlarged sectional view of a main part showing another embodiment.

FIG. 5 is an enlarged sectional view of a main part showing another embodiment.

FIG. 6 is a schematic view of a rib pattern of a conventional tire.

FIG. 7 is an enlarged sectional view of a main part showing the magnitude of uneven wear.

[Explanation of symbols]

 2 Shoulder grounding end 3 Vertical groove 4 Rib 5 Shoulder rib 7 Cut 8 Groove wall 10 Groove bottom 11 Crest 12 Valley 13 Reverse slope 14 Reverse slope 15 Reverse slope N Normal R Ridge

Claims (2)

(57) [Claims] 1. A plurality of linear flutes extending in the circumferential direction of a tire.
And the rib or the vertical groove interposed between the plurality of vertical grooves
In the pneumatic radial tire having a rib sandwiched between the shoulder ground contact end, a notch whose width and depth increase toward the groove bottom of the vertical groove is formed on a groove wall of a pair of vertical grooves sandwiching the rib , In addition, the ridge line of the valley portion has a normal line N to the tread surface portion at the valley portion of the cut.
And the groove width of the vertical groove increases toward the groove bottom at an angle θ
A pneumatic radial tire characterized by forming a reverse inclined portion inclined in a different direction . 2. The method according to claim 1 , wherein said cut of said rib is formed at a position where said cut is formed.
Fraud and mitigating risk rib cross-sectional area of the rib base portion is parallel to the tire tread portion surface, according to claim 1 is smaller than the rib cross-sectional area of the tread portion surface in the region of the groove bottom at least 1/2 of the groove depth Pneumatic radial tire.