JP3222682B2 - Pneumatic flat 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 a flat radial tire having a plurality of treads, the tread portion being separated by a wide annular recess.

[0002]

2. Description of the Related Art In a tire having a radial structure, especially for a passenger car, the height of the cross section with respect to the width of the tire has been increased due to the necessity of high speed and steering stability in accordance with recent high performance of the vehicle. The ratio, that is, the oblateness tends to decrease, and it is not uncommon for the oblateness to be around 50%, and even a tire having an ultra-flat cross section of as much as 30% has appeared. In the case of a tire having such a flat cross section, since the tire width is wide and the tread width is accordingly wide, the wet skid resistance tends to decrease as the flatness decreases. This is because as the tread width increases, it becomes more difficult to quickly drain the stepped water to the side. Grooves extending in various directions are cut on the tread for drainage, but to arrange grooves without sacrificing important characteristics other than wet skid resistance, the shape and amount (number of grooves) of the grooves There is a limit in terms of itself.

In order to solve such a problem, a wide circumferential groove is provided at the center of the tread portion so that the tread portion is divided into two right and left parts, and two motor cycle tires are arranged side by side. A tire having an outer contour with a small radius of curvature in each of the divided tread sections is proposed in GB 2,193,933 A. It is said that such a tread-shaped tire achieves its purpose in that when traveling on a road surface where the water depth is relatively shallow, water in the right and left treads can be efficiently discharged to the central portion of the tread and both sides. I can.

[0004]

However, on the other hand,
In the tire of such a shape, the divided tread portion area is abnormal due to a central wide groove, a circumferential drag on the area close to each tread edge, and an axial wiping centered on the central wide groove. It has been found that excessive early wear occurs, significantly impairing the appearance of the tread portion, and at the same time, lowering the vibration and steering stability. An object of the present invention is to provide a flat radial tire that solves the above problem.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a side tread from both ends of a cylindrical tread portion radially inward.
A radial arc extending from one of the side walls through the tread portion to the other side wall, a belt layer is disposed on the crown portion of the carcass to reinforce the tread, and The tire comprises a wide annular recess and treads axially separated by the annular recess, the treads having a substantially outer contour on an arc of a single radius of curvature on the cross section of the tread. This is a pneumatic flat radial tire characterized by forming the following.

[0006]

The tire of the present invention comprises a plurality of treads in which the tread portion is axially separated by a wide annular recess, and these treads have substantially a single radius of curvature on the cross section of the tread portion. Since the outer contour is formed on the circular arc, the contact pressure is uniformly distributed in the axial direction in each of the tread portions, so that abnormal wear does not occur. That is, in the case of a flat tire, the radius of curvature of the tread portion is significantly large, usually 2 to 20 times the tire radius, since the flat tire has a tread width (equal to or slightly smaller than the tire width) corresponding to a wide tire width. . Since the outer contours of the steps separated by the annular recess are formed substantially in common on the arc of this radius of curvature, the radius of curvature of the steps is large as in the case of the tire having no annular recess. It is a translation. Therefore, the tread portion has almost no difference in circumferential length between the positions in the axial direction. Therefore, dragging caused when there is a circumferential difference in the ground contact surface and abnormal wear due to wiping hardly occur.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a partial plan development view of a tire showing an embodiment of the present invention, and FIG. 2 is a partial cross-sectional view along AA in FIG. In the figure, tire 1
In FIG. 2, a pair of side walls 2 (a part inward in the radial direction is omitted in FIG. 2) and a tread portion 3 extending in a cylindrical shape over both side walls 2 are connected in a toroidal shape. Bead ring (not shown) embedded at the tip of
A carcass 4 having an end wound up around extends through the area of the side wall 2 and the tread 3;
Further, a belt layer 5 extending over the entire width of the tread portion is disposed between the carcass 4 and the tread portion 3 in the crown portion of the carcass 4 to strengthen the belt layer. Carcass 4 is a fiber code represented by polyester, rayon, nylon,
The belt layer 5 is formed of at least one ply arranged at approximately 90 ° (radial) with respect to the equatorial plane O, and the belt layer 5 is provided with a non-extensible code such as steel and / or aramid. A main trunk layer 6 in which at least two plies inclined at an angle of 10 ° to 30 ° are overlapped so that the codes intersect with each other, and a heat-shrinkable code such as nylon is formed around the main trunk layer 6. A structure composed of an auxiliary layer 7 formed by spirally winding a plurality of rubber-like ribbons (parallel rubber bodies) substantially parallel to the equatorial plane O can be applied.

The tread portion 3 comprises an annular recess 8 extending continuously in the circumferential direction, and a plurality of steps 9 separated in the axial direction by the annular recess. In this embodiment, the annular depression
Numeral 8 is located at the center of the tread portion 3, and thus divides the pair of tread portions 9 symmetrically with respect to the equatorial plane O. Annular recess width
W _D is 25% to 45% of the tread width W _T, the depth d significantly wide as 190 to 200 percent of the thickness of the tread (the maximum rubber thickness of the tread portion 9), and deep. In order to provide such an annular recess, the carcass 4 and the belt layer 5 are bent radially inward from the skeleton portion thereof. Tread part
By this a wide annular recess 8 occupies the center of the 3, the width W _S of the step parts becomes the narrowed with 28-38% of the tread width W _T.

[0009] tread portion 3, on an arc C _T of a single radius of curvature R _T which is formed in the tread portion 3 as the tread portion of a conventional tire having no annular recess 8, the outer contour of the left and right step parts C _S
Are formed substantially in agreement. End of equator plane O side of step 9
10 follows the annular recess 8 with a small chamfer-like curve. It is effective for the purpose of the present invention to form the portion 11 at the axially outer end corresponding to the tread end E of the tread portion with a small curve similarly to the inner end portion.

The left and right treads 9 are formed in a linear circumferential groove 12 at a central portion in the axial direction or a portion slightly shifted in the direction of the equatorial plane O.
And a plurality of inclined grooves 13 and 14 are provided at predetermined intervals in the circumferential direction from the annular recess 8 and the tread end E to the vicinity of the circumferential groove 12, respectively, so that a constricted portion is left.
At 15 and 16, the single-flow comb-shaped land portions 17 and 18 which are continuous in the circumferential direction and face one side in the circumferential direction are divided. Width W _G and a depth h of the circumferential groove, each relative to the width W _D and depth d of the annular recess s 6
-18%, and 35-50%. Note that the width and depth of the inclined grooves 13 and 14 can be provided to be equal to, slightly smaller than, and shallower than the width and depth of the circumferential groove 12, respectively.

[0011]

[Effect] To confirm the effect of the tire according to the present invention, 235 /
A tire of the embodiment having the structure shown in FIGS. 1 and 2 using a 45R17 size passenger car tire, and in addition to this, a step portion 9 having a curvature radius R _{S of the step portion} 9 independently formed by a relatively small outer contour. A comparative tire provided with was prepared, tested for abnormal wear, and evaluated. In preparing the test tire, the carcass had a radial structure of two 1500d / 2 polyester code plies, and the belt layer had two plies of 1 × 5 steel code (code angle 66 °). Was used in common. For tread specifications, tread width W _T , annular recess width
Per W _D and depth d, and the tires of Examples 200mm both comparative tires, 32 mm, and 20 mm. The radius of curvature R _S of the tread portion 9 was 2300 mm (the same value as the single radius of curvature R _T ) of the tire of the example, and 450 mm of the tire of the comparative example.

The test tire is assembled on an 8J × 17 rim.
Fill the internal pressure of 1Kgf / Cm ² and use a real vehicle to drive to general national road 5
The state of wear was examined by traveling 2500 km on a public road including 0%, 45% on an expressway, and 5% on a mountain road. As a result, in the comparative tire, early abrasion including heel and toe abrasion occurred at both ends of the left and right tread portions. In particular, at the end on the side of the annular depression, heel and toe abrasion with a difference of 1 mm was measured. On the other hand, the heel and toe abrasion of the same portion of the tire of the example was only 0.4 mm, and the abrasion appearance was extremely good.

[0013] Thus, the flat radial of the present invention is formed by forming an outer contour substantially on an arc having a single radius of curvature on the cross section of the tread portion with respect to the step portion separated in the axial direction by the annular recess. Tires can advantageously prevent partial premature wear, which tends to occur with such tires.

[Brief description of the drawings]

FIG. 1 is a partial plan development view of a tire showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view along AA in FIG.

[Explanation of symbols]

1 Tire 2 Sidewall 3 Tread 4 Carcass 5 Belt layer 8 Annular depression 9 Tread R _T Single radius of curvature of tread tread R _S Curvature of tread

Claims (1)

(57) [Claims] A radial arc extending from both ends of a cylindrical tread portion radially inward, and extending from one of the side walls through the tread portion to the other side wall; A belt layer is disposed on the crown portion of the carcass to reinforce the tire, and the tread portion is formed into a tire having a wide annular recess and a tread portion separated in the axial direction by the annular recess. The pneumatic flat radial tire, wherein the portion substantially forms an outer contour on an arc having a single radius of curvature on a cross section of the tread portion.