JPH0214902A - Flat pneumatic radial tire - Google Patents

Abstract

PURPOSE:To keep off any end separation as well as to make improvements in durability to high speed by increasing the number of sheets of a belt structure auxiliary layer for a flat pneumatic radial tire successively toward an side end from the central zone, and strengthening the circumferential rigidity. CONSTITUTION:An interval between sidewalls S and S' being opposed is reinforced by a radial carcass 10, supporting a treat T, and a belt structure B is set up between this tread T and the radial carcass 10. The tread T each of first to third circumferential grooves 40-45 at a symmetric position from the center of a tire, and first to fourth land part rows 50-56 are partitioned off among these circumferential grooves. The belt structure B is constituted of an auxilairy layer 30 by a heat contractible organic fiber cord together with a belt layer 20 by an inextensional cord of metal or the like, and the number of sheets of this auxiliary layer 30 is increased successively toward a side end from the tire center. Consequently, separation or the like at a belt end is prevented from occurring, thus improvement in durability to high speed is promotable.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to an improvement of a flat pneumatic radial tire, and more particularly to a flat pneumatic radial tire with improved high-speed durability. It is.

(Prior art) Flat pneumatic radial tires, which are generally referred to as ultra-high performance tires, have a wide tire with a so-called aspect ratio (tire cross-sectional height/tire cross-sectional maximum width) of 0°3 to 0.6. It has a tread and is especially used for high-speed running.

FIG. 2 is a cross-sectional explanatory view showing the tread of a conventional flat pneumatic radial tire. A radial carcass 1 reinforced from the sidewall S to the tread T area and the other sidewall S', and a belt having a width substantially corresponding to the tread width and disposed between the tread T and the radial carcass 1. Structure B is included.

Here, the tread T includes at least a pair of third circumferential grooves 4B, 4A' located near the equatorial plane 0 of the tire, and between the circumferential main grooves 4A, 4A' and the tread end 6.6'. At least two pairs of second and third circumferential grooves 4B located
. Land rows 5B, 5B', 3rd land row 5C15
0', fourth land column 5D, 5D' are divided.

In addition, the belt structure B is a non-stretchable cord (metal cord)
A belt layer 2 in which at least two plies arranged at a shallow angle with respect to the equatorial plane O are stacked so that the cords cross each other, and a heat-shrinkable fiber cord is placed on the outer periphery of the belt layer 2, and a heat-shrinkable fiber cord is arranged on the outer periphery of the belt layer 2, and It consists of auxiliary layers 3 arranged substantially in parallel.

And, the sleeve support Irl3 of the belt structure B is - numerically, one layer 3A for the entire width of the tire, and one layer (3A) for both sides of the tire.
3B) or two layers (3B and 3C) are arranged,
This is designed to suppress radial outward expansion of the belt layer 2 due to centrifugal force during high-speed transfer, thereby ensuring high-speed performance.

(Problem to be Solved by the Invention) By the way, when running at ultra-high speed with the conventional flat pneumatic radial tire described above, the tread width is particularly large, and the tread T@ surface has seven or more land rows. In many cases, the central area of the tread T wears out,
Moreover, since the wear profile is a flat surface substantially parallel to the axis of rotation of the tire, as a result, the wear on both sides of the tread is much less than on the central area.

The reason for this is that this type of tire is used in a range where the load during load transfer is small, and the centrifugal force during load transfer is large, so the central area with a large tread mass tends to protrude outwards more than the areas on both sides. it is conceivable that.

For this reason, in conventional flat pneumatic radial tires, after the middle stage of wear, both sides of the tread, which are less worn, bulge outward in the radial direction during running, resulting in an increased burden on the belt ends.

As a result, problems such as separation at the end of the belt and fraying of the sidewall occur, resulting in a significant decrease in the high-speed durability of the tire.

Therefore, the present invention was achieved as a result of studies aimed at solving the problems of the conventional flat pneumatic radial tires described above.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a flat pneumatic radial tire that eliminates problems such as separation at the end of the belt and fraying of the sidewall, and has excellent high-speed durability.

[Structure of the Invention] (Means for Solving the Problems) The present inventors have conducted various studies on the causes of separation at the end of the belt layer and sidewall fraying, especially after the middle stage of wear. Due to the early wear of the center area, which is a unique property of these types of tires, the tread rubber mass of the tread center area becomes smaller after the middle stage of the tread wear as a whole, while the tread rubber mass of the tread center area becomes smaller, while the tread rubber mass of the tread side areas, especially the belt layer edges, decreases. The mass was found to be in an unbalanced state, which is essentially the same as at the initial stage of wear.

Therefore, after the middle stage of wear, due to the relatively large mass of the tread on both sides of the tread, during high-speed running, the centrifugal force pulls the tread outward in the radial direction. Along with the concentration of strain and the heat generated at that time, large shear strain occurs between the carcass and its folded end in the sidewall, which induces separation of the carcass folded end because the carcass body has a originally small elastic modulus, and furthermore, this This will cause the separation to stretch and cause the sidewall to bulge. As a result of various studies, it was found that increasing the circumferential rigidity of the belt crosspiece in stages from the center of the tread to the side edges is effective in eliminating belt edge separation and blowing from the sidewalls. Discover this and arrive at the present invention.

That is, the flat pneumatic radial tire of the present invention includes a cylindrical tread, sidewalls extending radially inward from both ends of the tread, and a radial carcass that is mutually reinforced from one sidewall to the tread area and the other sidewall. , a belt structure having a width substantially corresponding to a tread width and disposed between the tread and the radial carcass, the tread having at least a pair of first circumferential grooves located near the equatorial plane of the tire; At least 62 pairs of second and third circumferential grooves located between the directional groove and the tread end are provided symmetrically with respect to the equatorial plane, and the land section row is divided into at least seven rows by these circumferential grooves. In addition, the belt structure includes at least two plies in which non-extensible cords are arranged at a shallow angle with respect to the equatorial plane, and the belt layer is overlaid so that the cords intersect with each other, and on the outer periphery of the belt layer. A tire comprising an auxiliary layer in which heat-shrinkable fiber cords are arranged substantially parallel to the equatorial plane,
The number of auxiliary layers of the belt structure is determined from the first land section row divided between the two first circumferential grooves to the second land section row divided into the first circumferential groove and the second circumferential groove. , increases sequentially toward the third land row divided into the second circumferential groove and the third circumferential groove, and the fourth land row divided between the third land row and the tread edge, and increases the circumference of the belt structure. A flat pneumatic radial tire whose directional rigidity is gradually strengthened from the center of the tread to the side edges.

(Function) The flat pneumatic radial tire of the present invention includes at least seven rows of ridges in the tread portion, formed by a pair of first circumferential grooves and at least two pairs of second and third circumferential grooves. In the wide flat tire, the number of auxiliary layers in the belt structure is determined from the central area corresponding to the pair of circumferential grooves to the first to third circumferential grooves divided by the first circumferential groove and the second and third circumferential grooves. Since the number of auxiliary layers in the side area is increased to at least 4 toward the fourth land section row, the circumferential rigidity of the belt structure is strengthened stepwise from the center of the tread to the side edge, and The rigidity of the area can be maximized.

Therefore, in the flat pneumatic radial tire of the present invention, even if the tread rubber mass of both side areas increases after the middle stage of tire traction, the rigidity of the belt structure from the central area to both side areas is gradually strengthened. In particular, the at least four auxiliary layers present on both sides of the belt act as a reinforced hoop for the ends of the belt layer, which may cause problems such as separation at the ends of the belt and fraying of the sidewalls. There is no problem, and high-speed durability can be greatly improved.

(Description of Examples) Examples of the flat pneumatic radial tire of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory cross-sectional view showing an embodiment of the flat pneumatic radial tire of the present invention.

Although parts other than the tread are not shown in FIG. 1, the other parts have a well-known structure.

In other words, a flat pneumatic radial tire has a pair of annular bead cores, and a radial carcass extends between both bead cores in a toroidal manner. It consists of one or more plies arranged at an angle of substantially 90 degrees with respect to the circumferential direction, and although not shown, both ends of the ply are wound around the bead core from the inside in the axial direction to the outside. This is a well-known structure in which a hard rubber filler is usually filled between the rolled up ends and the radial carcass.

As shown in FIG. 1, the tread T of the tire has sidewalls s and s' extending radially inward from both ends of the tread T, and from one sidewall S to the tread 1 area and from the other side. A radial carcass 10 mutually reinforced on the wall S′ and a substantially tread T
It includes a belt structure B having a width corresponding to the width of , and disposed between the tread T and the radial carcass 10.

Here, the tread T includes at least a pair of first circumferential grooves 40.41 located near the equatorial plane O of the tire, and at least a pair of first circumferential grooves 40.41 located near the equatorial plane O of the tire, and at least a pair of first circumferential grooves 40.41 located near the equatorial plane O of the tire and at least At least six circumferential grooves consisting of two pairs of circumferential grooves, that is, second circumferential grooves 42.43 and third circumferential grooves 44.45, are symmetrical and approximately equal to each other with respect to the equatorial plane O. These at least six circumferential grooves are provided at intervals, and the first land row 50, the second land row 51.52, the third land row 53.54, and the fourth land row 5
5.56 are classified.

In addition, the belt structure B includes at least two plies of non-stretchable cords such as metal cords arranged at a shallow angle (approximately 50° to 30°) with respect to the equatorial plane O so that the cords intersect with each other. Consisting of a superimposed belt layer 20 and an auxiliary M30 in which heat-shrinkable fiber cords made of organic fiber cords are arranged substantially parallel to the equatorial plane 0 on the outer periphery thereof with a width slightly exceeding the width of the belt layer, The number of the auxiliary layers 30 is determined from the central area (first land row 50) corresponding between the first circumferential grooves 40.41 to the first circumferential grooves 40.41 and the second circumferential grooves 42. 43 (second land row 51.52), the second circumferential groove 42.4
3 and the third circumferential groove 44.45 (third land row 53.54) and a bright area (fourth land row 53.54) corresponding to the third circumferential groove 44.45 and the tread edge 60.60' land line 5
5.56).

That is, in this embodiment, the first land row 50 has one auxiliary layer 30 covering the entire area of the tread T, and the second land row 51 has one auxiliary layer 30 covering the entire area of the tread T.
．． 52 has a total of two auxiliary layers 30 and narrow auxiliary layers 31.31', and the third land row 53.54 has the auxiliary 130 narrow auxiliary layers 31.31' and further narrow auxiliary layers 32. 32' in total, and the fourth land row 55, 56 has the auxiliary layer 30
, a narrow width auxiliary layer 31.31', a narrow width auxiliary layer 32.32', and a further narrow width auxiliary layer 33.33'. By arranging the auxiliary layers in this way, The circumferential rigidity of the belt structure B is gradually strengthened from the central area of the tread T toward both side areas, and the rigidity of the fourth land section row 55, 56 is the strongest.

In addition, each of the auxiliary layers 30 to 33 in the belt structure B has one end located on the radially outer side of the fourth land section row 55, 56, and the other end located on the axial direction of each of the land section rows 50 to 56. It is preferable that the auxiliary layer terminates at a position 5III or more inward from the outer edge of each land row, and more preferably at a position substantially in the center of the ridge. The other end position need not even be included within the predetermined block. This not only makes ideal the hoop effect of both sides of the tread T (namely, the fourth land row 55, 56) and the difference in belt rigidity. , it is possible to take measures against defects during manufacturing, and also to obtain favorable results in terms of measures against separation at the axially inner end of each auxiliary layer.

By configuring as described above, the circumferential rigidity of the belt structure is gradually strengthened from the center area of the tread to both end areas, and the rigidity of both end areas (bright areas) is greatest, so that Problems such as belt edge separation and sidewall fraying are eliminated, and high-speed durability can be greatly improved.

Next, the effects of the flat pneumatic radial tire of the present invention will be further explained using test examples.

(Test Example) The configuration shown in FIG. 1 was added to a radial tire of tire size 255140ZR17.

That is, Rayon cord 1650 d/2 is used as the radial carcass 10, and the belt layer 20 of the belt structure B is
Steel cords of 0.23XIX5 were arranged so as to cross each other at an angle of 25 degrees with respect to the circumferential direction of the tire.

Further, as the auxiliary layer 30, nylon cords 12 that cover the entire width of the belt layer 20 and are substantially parallel to the circumferential direction of the tire are used.
60 d/2 in one layer, and each land column 51.5
2, the ends of narrow auxiliary layers 31 and 31' made of the same nylon cord as the auxiliary layer 30 are connected to each land row 53.
．． At the center of the auxiliary layer 54, there is an end of the narrow auxiliary layer 32, 32' made of the same nylon cord as the auxiliary layer 7 [ff30], and at the center of each land row 55, 56 there is the same nylon cord as the auxiliary layer 30. The terminal ends of the narrow width auxiliary layers 33, 33' consisting of The flat pneumatic radial tire of the present invention was manufactured according to the manufacturing conditions of ordinary radial tires.

On the other hand, for comparison, a conventional tire was manufactured under the same conditions as above, except that a total of three auxiliary layers were placed on the radially outermost land row as shown in Figure 2. did.

For these two types of radial tires, tire wear amount = 50%, tire internal pressure: 2.5 kg/cJ, vehicle speed:
Step up sequentially from +++/hr to 100,
As a result of an actual vehicle test under the condition of load: 500 kg, the index of the tire of the present invention was 125 when the conventional tire was set as 100, demonstrating that it has excellent high-speed durability.

[-3'! ! , bright effect] As described above in detail, the flat pneumatic radial tire of the present invention has the following effects due to the pair of first circumferential features and the at least two pairs of second and third circumferential self-extinguishers. In a wide flat tire having at least seven rows of ridges in the tread,
The number of auxiliary layers in the belt structure is increased from the central area corresponding to the pair of first circumferential self-extinguishing spaces to the first circumferential inner groove and the second circumferential inner groove.
, the number of auxiliary layers of the opening is increased sequentially toward at least two intermediate regions corresponding to the third circumferential self-extinguishing space, the third circumferential inner groove, and the land section row of the opening corresponding to the tread end, and the number of auxiliary layers of the opening is increased at least. By using four layers, the circumferential rigidity of the belt structure can be strengthened in stages from the center of the tread toward the opening, and the rigidity of both side areas can be maximized.

Therefore, in the flat pneumatic radial tire of the present invention, even if the tread rubber mass on both sides increases after the middle stage of tire wear, the rigidity of the belt structure from the central area to both sides is strengthened in stages. In particular, the at least four auxiliary layers present on both sides of the belt act as a hoop, eliminating problems such as separation at the end of the belt and wiping from the sidewalls, greatly improving high-speed durability. can be increased to

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view showing an embodiment of a flat pneumatic radial tire of the present invention, and FIG. 2 is an explanatory cross-sectional view showing a conventional flat pneumatic radial tire. T・・・・・・・・・・・・・・・Tread s,
s'・・・・・・Sidewo B・・・・・・・・・
・・・・・・・・・Belt structure 0・・・・・・・・・
・・・・・・・・・Equatorial plane 10・・・・・・・・・・・・
...Radial force 20...
・Belt layer 30-33.31'-33'・Old・・Auxiliary layer 40.41・・・First circumferential groove 42.43・・・Second circumferential groove 44.45・...Third circumferential information 50-56...Land row 60.60'...Tread end Lukas

Claims (1)

[Scope of Claims] A cylindrical tread, sidewalls each extending radially inward from each end of the tread, a radial carcass reinforced from one sidewall to the tread area and the other sidewall, and a radial carcass having a substantially tread width. a belt structure disposed between the tread and the radial carcass and having a width corresponding to at least two pairs of second and third circumferential grooves located between the belt structure and the belt structure are provided symmetrically with respect to the equatorial plane, and the land section row is divided into at least seven rows by these circumferential grooves; However, there is a belt layer in which at least two plies in which non-extensible cords are arranged at a shallow angle with respect to the equatorial plane are stacked so that the cords intersect with each other, and a heat-shrinkable fiber cord is placed on the outer periphery of the belt layer. In the tire comprising auxiliary layers arranged substantially parallel to the equatorial plane, the number of auxiliary layers of the belt structure is increased from the first land row divided between the two first circumferential grooves to the first circumferential groove. A second land row divided into a directional groove and a second circumferential groove, a third land row divided into a second circumferential groove and a third circumferential groove, and a third land row divided into a tread edge. A flat pneumatic radial tire characterized in that the circumferential rigidity of the belt structure is gradually strengthened from the center of the tread toward the side edges.