JP3218145B2 - 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 a radial tire having a plurality of treads, the tread 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 wide accordingly, the wet skid resistance tends to decrease as the oblateness decreases. This is because as the tread width increases, it becomes more difficult to quickly drain the stepped water to the side. Although grooves extending in various directions are cut on the tread for drainage, the grooves must be arranged in a range that does not sacrifice important properties other than wet skid resistance. There is a limit in terms of).

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, in the area of the divided tread part, abnormal early wear occurs due to circumferential dragging in the area close to the central wide groove and wiping in the axial direction centering on the central wide groove. However, it was found that the appearance of the tread portion was significantly impaired, and at the same time, the vibration and the steering stability were lowered. An object of the present invention is to provide a radial tire that solves the above-mentioned 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 radial tread, and In the tire comprising a wide annular recess having a wide width and a tread portion separated in the axial direction by the annular recess, a narrow portion extending in the circumferential direction near the tire axially inner end of the tread facing the annular recess. A pneumatic radial tire having a groove. Here, the inner end in the tire axial direction of the tread portion is defined as the innermost contact limit position (contact end) in the tire axial direction when the tire is loaded on a flat plate under normal internal pressure and load conditions specified in the JATMA standard.

[0006]

The tire according to the present invention has a narrow groove extending in the circumferential direction near the inner end in the tire axial direction of the tread tread, so that a rounded portion extending from the tread to the annular recess ( Even if uneven wear due to dragging occurs when the circumferential length is shorter than the circumferential length of the tread portion), the spread to the tread portion can be blocked by the narrow groove. The position of the narrow groove is more preferably on the side of the slightly annular recess which continues rounded from that position than on the side of the step portion.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a sectional view of a tire showing an example of the present invention, and FIG. 2 is a plan view of the tire. In FIG. 1, a tire 1 has a pair of side walls 2 and a tread portion 3 extending between the two side walls 2 and extending in a cylindrical shape extending in a toroidal shape. The carcass 5 with the end wound around the dring 4
Extending through the second and regions of the tread portion 3, Mataka - between the tread portion 3 in the crown portion of the Kas 5, to strengthen disposed belt layer 6 extending over the full width W _T of the tread portion I have. The carcass 5 has a fiber code represented by polyester, rayon,
At least one ply arranged at 0 ° (radial), and the belt layer 6 is provided with a non-extensible code such as steel and / or aramid at 15 ° relative to the equatorial plane O.
At least two inclined arrangement plies at an angle of 40 °, it like the co - the trunk layer 6 ₁ superimposed to de intersect, heat-shrinkable co-nylon or the like around - a plurality of de the (rubberized ribbon-like bodies), it can be applied equatorial plane O and substantially parallel to formed of spirally wound turn is formed by the auxiliary layer 6 ₂ structure. In FIG. 1, the right half from the equatorial plane O shows only the outer contour, and details are omitted, but it is symmetrical.

The tread portion 3 comprises an annular recess 7 extending continuously in the circumferential direction, and a plurality of tread portions 8 separated in the axial direction by the annular recess. In this embodiment, the annular depression
Numeral 7 is located at the center of the tread portion 3, and thus divides the pair of tread portions 8 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 is 190 to 200% of the thickness of the tread t (maximum rubber thickness of the step parts 8)
Remarkably wide and deep. In order to provide such an annular recess, the carcass 5 and the belt layer 6 are bent radially inward from the skeleton portion thereof. By this a wide annular recess 7 occupies the central portion of the tread portion 3, the width W _S of the step parts becomes the narrowed with 28-38% of the tread width W _T. The British Patent 2,19 mentioned earlier
The tire shown in 3,933 A has a structure in which the tread portion is separated in the axial direction by providing a wide circumferential groove in the center of the tread portion within the thickness range of the tread rubber.

The outer contour of the step portion 8 is formed on an arc having a single large radius of curvature R _T formed on the tread portion 3 like a tread portion of a normal tire having no annular depression 7. Alternatively, the foot 8 may be formed in a separate arc shape. Portion 9 following the annular recess 7 from the step parts 8, smoothly contiguous with the annular recess 7 has an arc of small radius of curvature R _S, shows the axially inner position of the step parts end by symbol E _I. Further, the axially outer end of the tread portion is at the position of reference symbol E _O. The tread ends E _I and E _O are both positions that partially approach the rounded portions.

In the present invention, the step portion 8 is located near the axially inner end E _I of the tire, that is, on or near the end E _I , or axially inside or outside this position, and extends along the tread end E _I. Narrow groove 10
Shall be provided. The annular recess 7 side away 4mm from the axially inner end E _I step parts in FIGS. 1 and 2, shows an example where the narrow groove 10 provided one width 2 mm, depth 5 mm. The narrow groove 10 can be applied within a range of substantially 0.5 to 5 mm per width w and a depth e of 20 to 80% of the maximum t of the tread portion. And the number is one or more. If the narrow groove is plural, wide near the width or the portion 9 having a rounded end E _I, narrow, deep depth, shallow, varied within the above range can be provided. By doing so, the spread of uneven wear generated in the short circumferential portion 9 to the tread portion 8 is reduced.
The position can be effectively suppressed or blocked.

As shown in FIG. 2, the tread portion 3 of the tire according to the embodiment has an annular recess 7 from the axially outer end E _O of the tread portion.
A large number of lug grooves 11 extend toward the land portion 13 together with a circumferential groove 12 provided substantially at the center of the tread portion. Lug groove
Numeral 11 inclines in the direction converging with the equatorial plane O between the left and right treads 8 and extends into the annular recess 7 leaving a constriction 14 in the land near the circumferential groove 12. As a result, the land portion divided by the lug grooves is axially divided by the narrow grooves 10. If the lug groove 11 does not reach the annular recess 7,
10 can not be divided at the position of the lug groove 11 is provided continuously in the circumferential direction parallel to the tread portion edge E _I.

[0012]

[Effect] To confirm the effect of the tire according to the present invention, 235 /
A tire of the embodiment shown in FIGS. 1 and 2 using a 45R17 size passenger car tire, and in addition to this, a step portion formed by an outer contour having a relatively small radius of curvature _{RT of the step portion} 8.
8 and a comparative tire without a narrow groove was prepared and subjected to an uneven wear test to evaluate. 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 24 °). Was used in common. For tread specifications, tread width
Regarding W _T , the width W _D and the depth d of the annular recess, the tires of the example and the comparative tire were set to 210 mm, 57 mm and 20 mm. The radius of curvature R _T of the tread portion 8 is also 23 in both the embodiment and the comparative example.
00 mm (the same value as the single radius of curvature of the tread portion). And for tires of Examples, 2mm wide at a position axially inner 4mm from step parts end E _I, it provided one of the narrow groove 10 of depth 5 mm (depth e / tread thickness t = 0.5).

The test tire is assembled on an 8J × 17 rim.
The internal pressure of 1 kgf / Cm ² was charged, and the state of abrasion was examined by running 2500 km on a test road mainly including an asphalt pavement road with an actual vehicle. As a result, in the comparative tire, premature wear including heel and toe wear occurred at both ends of the left and right tread portions, and in particular, heel and toe wear with a difference of 1 mm was measured at the end facing the annular depression. 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.

As described above, the flat radial of the present invention is formed by forming a substantially outer contour on an arc having a single radius of curvature on the cross section of the tread portion with respect to the tread portion separated in the axial direction by the annular recess. The tire can advantageously prevent partial premature wear, which is likely to occur with this type of tire.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire showing an example of the present invention.

FIG. 2 is a plan view of a tire showing an example of the present invention.

[Explanation of symbols]

1 Tire 2 Side wall 3 Tread section 5 Carcass 6 Belt layer 7 Annular recess 8 Tread section 10 Groove E _I Inner axial end of tread section

Continuation of front page (56) References JP-A-63-34204 (JP, A) JP-A-6-320911 (JP, A) JP-A-63-87302 (JP, A) JP-A-4-185505 (JP) , A) Fully open sho 59-132404 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11/00-11/04 B60C 11/12, 3/00

Claims (1)

(57) [Claims] 1. Sidewalls extend in a radially inward direction from both ends of a cylindrical tread portion, and one of these sidewalls passes through a tread portion and the other sidewall.
A radial arc extending over the carcass and a belt layer disposed on the crown of the carcass for reinforcement, and the tread is axially separated by the wide annular recess and the annular recess. A pneumatic radial tire, comprising: a tire having a tread portion, wherein a narrow groove extending in a circumferential direction is provided near a tire axially inner end of the tread portion facing the annular recess.