JP3172249B2 - 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 a pneumatic radial tire, and more particularly to an improvement in a tread pattern of the pneumatic radial tire, and more particularly to an improvement in braking performance on ice and snow road surfaces and wet road surfaces. The pneumatic radial tire is not particularly limited in terms of the type of use of the tire, but is particularly suitable for use as a tire for a passenger car.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 2-169307 discloses a pneumatic tire having a block pattern and a tread having a plurality of thin notches in a block, more specifically, a pneumatic radial tire for trucks and buses. By providing the cut, that is, the sipe only from the position where the distance corresponding to 1/3 to 1/2 of the entire length of the block is protruded from the stepping side end of the block and thereafter, the stepping caused by the fall of the block divided by the sipe during braking is performed. It is disclosed that the contact area of the block caused by the floating on the side is prevented from being reduced, and the braking performance on the icy road is improved.

[0003]

SUMMARY OF THE INVENTION The present invention is not only for braking performance on icy and snowy roads, but also on wet roads which are more often encountered when using pneumatic radial tires on more general roads including ice and snow areas. In order to more effectively improve and improve the braking performance of the tires on ice and snow road surfaces, a large number of blocks, that is, land protrusions that are independent from each other on the outer periphery of the tread are arranged in rows along the circumference of the tread. In addition, for a tire having a block-type tread pattern having a plurality of sipes, each of the land ridges traversing the width of the tread, an effective drainage action by the land ridges and an appropriate effective contact area when braking. It was made as a result of repeated research aiming at separation of the two functions with the aim of securing It is an object of the present invention to propose a pneumatic radial tire having a novel tread pattern excellent braking performance.

[0004]

According to the present invention, a large number of land protrusions which are independent from each other on the outer periphery of the tread are arranged in a plurality of rows along the circumference of the tread, and each land protrusion is connected to the tread. With multiple sipes crossing along the width of the
In a pneumatic radial tire that becomes a block type tread pattern, a land portion belonging to at least most of the rows of the plurality of arrays has a wide head including a stepping edge to the tire ground, and a wide head including the stepped edge. The wide head has a larger sipe distribution density than the narrow head, and has excellent braking performance on ice and snow and on wet roads, with a narrow tail that follows to the kicking edge. A pneumatic radial tire, where the land ridge has a width ratio of the wide head to the narrow tail of 1.1 to 1.4, and the width of the wide head relative to the total length of the wide head and the narrow tail. The percentage is
Be in the range of 0.25 to 0.5, the wide head has a stepped edge inclined with respect to the equatorial plane of the tire,
It is particularly preferred in practice that the wide head has a stepped edge consisting of a convex curve facing the narrow tail of the adjacent land ridge on the row of land ridges.

FIG. 1 shows a block type tread pattern of a pneumatic radial tire according to the present invention in a developed plan view of a main part of a tread 1 of the pneumatic radial tire. The vehicle mounted with the tires rolls up from the bottom to the top of the page of the drawing, so that the land ridges 2 independent from each other on the outer periphery of the tread 1 The edge s and the lower edge serve as the ejection edge k.

In the present invention, the land protuberance 2 comprises a wide head 2a including a stepping edge s and a narrow tail 2b including a kicking edge k. The wide head 2a crosses the wide head 2a in the width direction of the tread 1. (Four in the illustrated example) are provided, but only a small number (one in the illustrated example) of the narrow tail 2b is provided.
In addition, the sipe 3a and the sipe 3b can have a cut depth in the range of 0.2 to 0.8 with respect to the groove depth of the circumferential groove 4.

[0007] In the figure, reference numeral 4 denotes an illustrated example in which the tread 1 is moved 5 in the width direction.
The center block row is divided along the center circumference of the tread, and four circumferential grooves are provided to define a pair of both side block rows and a pair of intermediate block rows. Along the peripheral groove 4, and is divided by the peripheral groove 4 and the sub-groove 5 into the above-mentioned land portion protrusion 2.
Are formed independently of each other.

In the figure, the land ridge 2 belonging to the center block row is a simple rectangular so-called caramel block without a wide head 2a and a narrow tail 2b. It goes without saying that the shape can be the same as that of the land ridge 2 belonging to the block row.

[0009] land portion raised 2 the width W ₁ of the wide head 2a along the widthwise direction of the tread 1, also the ratio of the width W ₂ of the narrow tail 2b 1.
1 to 1.4 and a wide head along the circumference of tread 1
Total length l ₁ of wide head 2a and narrow tail 2b of length l _{1 of} 2a
The ratio with respect to + l ₂ = L is in the range of 0.25 to 0.5, and this relationship is common, and FIGS. 3 (a), (b), (c), (d), (e) and
The shape of the land ridge 2 as shown in (f) can be selected. In the case of FIG. 3 (f), a narrow groove 3a 'is provided in place of the sipe 3a located between the wide head 2a and the narrow tail 2b.

A pneumatic radial tire having a feature in the above-described block type tread pattern itself has the following general structure. That is, a fiber cord ply (polyester, rayon, nylon) comprising a pair of sidewalls connected to the tread on both sides thereof and a bead formed on the inner periphery of each side wall, and a bead core embedded in both bead portions fixedly united on both sides. ) And a toroidal radial carcass along the inner circumference of the tread, and a non-extensible cord (steel, aramid) surrounding the crown area of the radial carcass and disposed between the carcass and the tread ) A belt that is cross-laminated with a swash cloth (cord angle 10 ° to 30 ° with respect to the equatorial plane of the tire) and, if necessary, further over the entire outer periphery or both side edges of the belt, heat-shrinkable cord (eg, nylon) is applied to the tire. It has an auxiliary layer arranged substantially parallel to the equatorial plane.

[0011]

The at least most of the land protruding rows (two-sided block rows and intermediate block rows shown in FIG. 1) which form a row along the tread circumference and are arranged in a plurality in the width direction of the tread. Since the land ridge 2 to which it belongs has the wide head 2a including the step edge s, when the step edge s of the wide head 2a starts to touch the water film spreading on the wet road surface. The water draining action is effective to push the water film to both sides of the land protuberance 2 to force drainage from the sub-groove 5 to the circumferential groove 4, and the wide head 2a forms a narrow tail 2b. The sipe 3a having a larger distribution density than the stepped edge s every time the sipe edge touches the ground.
Under the same draining action as in the above, it helps to promote the drainage more advantageously. This draining action is ensured, and the width of the wide head 2a is increased to such an extent that the drainage is not carried over after the land uplift, that is, to the narrow tail, while the narrow tail 2b becomes the wide head 2a. On the other hand, by taking a relatively long length and reducing the array distribution density of the sipes 3a, an effective ground contact length is secured for the land protuberance 2 so that a ground contact area necessary for braking is obtained. The braking performance on the road surface can be improved.

[0012]

EXAMPLE For a test tire having a tire size of P195 / 70 R14, W ₁ : 20 mm, W ₂ : 16 mm, l ₁ : 16 mm, l _{2 in} the pattern arrangement shown in FIG. : 20mm: Pneumatic radial tire of the present invention in which land ridges 2 having specifications of sipe width 0.5mm, sipe arrangement interval 4mm, sipe depth 7mm, groove depth (both circumferential groove and sub-groove) 10mm are arranged. Comparative example in which the caramel-shaped blocks belonging to the center block row of FIG. 1 were applied to both side and middle block rows, and the distribution of the sipe in the stepping-side half portion of the caramel-shaped blocks was increased. A prototype was produced together with a conventional example according to the disclosure of Japanese Patent Application Laid-Open No. 2-169307, and an actual vehicle test of each tire was performed as follows. The air pressure was unchanged at 2.0 kgf / cm ² , and the braking performance (braking distance) at each vehicle speed of 40 km / h on ice and snowy roads and 80 km / h on wet roads was measured and compared, and the results in the following table were obtained.

[0013]

[Table 1]

[0014]

According to the present invention, the braking performance of a pneumatic radial tire having a block type tread pattern on icy and snowy road surfaces and on wet road surfaces can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a developed plan view of a tread main part of an embodiment.

FIG. 2 is a diagram showing a planar shape of a land portion ridge.

FIG. 3 is an explanatory view showing a modified example of the land portion ridge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread 2 Land ridge 2a Wide head 2b Narrow tail 3a, 3b Sipe 3a 'Narrow groove 4 Circumferential groove 5 Secondary groove

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-16811 (JP, A) JP-A-3-112704 (JP, A) JP-A-2-169307 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B60C 11 / 11,11 / 12

Claims (4)

(57) [Claims] A plurality of land ridges that are independent of each other on the outer periphery of the tread are arranged in a plurality of rows along the circumference of the tread, and each of the land ridges traverses along the width of the tread. In the pneumatic radial tire which becomes a block type tread pattern having a sipe, a land portion belonging to at least most of the rows of the plurality of arrays has a wide head including a stepping edge to the tire contact surface, Following this wide head, with a narrow tail reaching the kick-out edge, the wide head has a greater sipe distribution density than the narrow tail, and has excellent braking performance on ice and snow and on wet road surfaces A pneumatic radial tire, characterized in that: The land ridge has a width ratio of the wide head to the narrow tail of 1.1 to 1.4, and a ratio of a length of the wide head to a total length of the wide head and the narrow tail is 0.25 to 0.5. The pneumatic radial tire according to claim 1, having a dimension within a range. 3. The pneumatic radial tire according to claim 1, wherein the wide head has a stepped edge inclined with respect to the equatorial plane of the tire. 4. The pneumatic radial tire according to claim 1, wherein the wide head has a stepped edge formed of a convex curve facing the narrow tail of the land ridge adjacent on the row of land ridges. .