JP2001171318A - Pneumatic radial tire - Google Patents

Abstract

(57) [Problem] To provide a pneumatic radial tire having both abrasion resistance and bead portion durability. The carcass layer includes a tread portion, a sidewall portion, and a bead portion, and is arranged at an angle of substantially 90 ° with respect to the tire equator, and is turned over by a bead core.
In a pneumatic radial tire having a radially outer side of the carcass layer and a belt reinforcing layer disposed between the tread rubber layers, the treads on both shoulders of the tread are assembled in a regular rim and filled with a regular internal pressure. The width drop amount is 4% to 6.5% of the tread width, and a triangular cross-sectional projection projecting outward from the tire is continuously formed in the circumferential direction from the bead portion on the upper side of the bead rim flange to the sidewall portion. Provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire capable of achieving both abrasion resistance and bead portion durability by optimizing a cross-sectional shape of a tread end portion and securing bead portion rigidity.

[0002]

2. Description of the Related Art The running of tires causes the wear of tread rubber, but the degree of wear varies depending on the running conditions such as the roughness and unevenness of the road surface, cornering and braking, running speed, and the type of vehicle used. Come.

For example, RV (Recreational)
A four-wheel drive vehicle used for multiple purposes, such as a "vehicle" vehicle, has a heavy vehicle weight, and thus has severe tire wear conditions.

[0004] In particular, when the conditions of use become severe, not only the wear rate becomes faster, but also [1] both shoulder portions of the tread wear faster, [2] the central portion of the tread wears faster,
[3] Frequent occurrence of uneven wear such as only one side of the tread wears quickly and [4] wear of a part of the tread circumference quickly.

In order to improve the wear resistance described above, it is effective to make the tread tread portion uniform in contact with the ground. As a countermeasure, a curvature (R1) of the tread shoulder portion toward the outside of the tire and another curvature (R1) of the sidewall shoulder portion toward the outside of the tire, as shown in the cross-sectional view of the tire in FIG.
It has been conventionally known that the tread width (TW) drop amount (ΔH) at both tread shoulders is reduced with respect to the tread width (TW) defined by the distance between the intersections (P1) and (P2) of 2). ing.

However, when the drop amount (ΔH) is reduced, the strain applied to the tread tread portion is reduced and the ground contact shape becomes uniform, and the abrasion is improved. However, the strain applied to the tread portion reduces the sidewall. As a result, the bead portion is moved in the direction of the over-bead portion and a large strain is applied to the bead portion, resulting in a decrease in the durability of the bead portion.

[0007]

SUMMARY OF THE INVENTION As described above, while the wear resistance can be improved by reducing the amount of tread width reduction at both tread shoulders, the problem that the durability of the bead portion is lowered is solved by the present invention. The inventor analyzed the relationship between the shape of each part of the tire and the strain applied thereto, and found a method for solving the above problem by appropriately dispersing the strain and preventing the strain from being concentrated on a specific part.

An object of the present invention is to provide a pneumatic radial tire that achieves both improvement in wear resistance and bead durability.

[0009]

The present invention provides a tread portion,
A carcass layer comprising a sidewall portion and a bead portion, arranged at an angle of substantially 90 ° with respect to the tire equator, and folded by a bead core; and a belt reinforcing layer disposed between a radial outside of the carcass and a tread rubber layer. In the pneumatic radial tire provided with the rim, when the rim is assembled to the regular rim and the regular internal pressure is filled, the tread width drop amount at both shoulder portions of the tread is 4% to 6.5% of the tread width, and the bead portion rim is provided. The pneumatic radial tire is characterized in that a protrusion having a triangular cross section that protrudes toward the outside of the tire is continuously provided in a circumferential direction on a sidewall portion above the flange.

[0010] By reducing the amount of tread width drop at both tread shoulders from that of the conventional product and in the range of 4% to 6.5% of the tread width, distortion of the tread tread portion is reduced to make the ground contact shape uniform, In addition, by providing a protrusion having a triangular cross section on the sidewall portion above the bead portion rim flange, the rigidity of the bead portion can be increased. In addition, by adopting a triangular cross section, it is possible to suppress the heat generation while suppressing the volume of the rubber while securing the rigidity.

Further, it is preferable that the apex of the triangular protrusion is located on a sidewall portion between the bead portion rim flange and the tire maximum width portion.

By providing the apex of the triangular protrusion on the bead side from the tire maximum width position, the distortion applied to the bead portion is transferred to the buttress portion, and the bead durability is further improved.

The height of the apex of the triangular protrusion is 2
Claim 1 characterized in that it is in the range of 5 mm to 5 mm.
2 is a pneumatic radial tire.

The height of the apex of the triangular protrusion is 2 mm or more.
When the thickness is within the range of 5 mm, it is possible to secure the rigidity of the bead portion and to prevent a decrease in durability due to heat generation.

Preferably, the cross-sectional shape of the triangular protrusion is a trapezoidal triangle whose apex is shifted toward the rim flange, and the center of the bead rigidity can be arranged at an optimum position required by tire performance. .

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 is a sectional view showing a tire according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view showing a bead portion of the tire.
FIG. 3 is a half sectional view of the tire in a tire width direction.

As shown in FIG. 3, the tire (T) of the present invention comprises a tread portion (1), a sidewall portion (2) and a bead portion (3), and has a cord arrangement at an angle of about 90 ° with respect to the tire equator. A belt reinforcement comprising a carcass layer (4) folded back by a bead core (5) and a plurality of steel cord and / or fiber cord layers disposed between the radial outside of the carcass layer and the tread rubber layer (7). It has a layer (6), the structure of which is the same as that of a general pneumatic radial tire, and a pattern consisting of main grooves and sub-grooves is formed on the outer periphery of the tread.

Tread width (TW) of the tire (T)
Introduces TRA (The Tire and Ri)
In the state where the rim is assembled to a regular rim prescribed by the m Association and a normal internal pressure is filled, another curvature (R1) of the tread shoulder portion toward the tire outside and another curvature of the sidewall shoulder portion toward the tire outside (see FIG. 1). R2)
Is the distance between the intersections (P1) and (P2) of the tread, and the tread width (TW) drop (ΔH) of the tread shoulders is the tire height (H1) from the nominal rim diameter (B) to the top of the tread equator. From (B), the intersection (P1) or (P
The difference (ΔH) from the height (H2) up to 2).

Tread width (TW) of both shoulders of the tread
The drop amount (ΔH) is 4 to 6.5% of the tread width (TW).
Is set to be smaller than the conventional value exceeding 6.5%.
As a result, the step between the central portion of the tread and the shoulder portion is reduced, the strain applied to the tread portion is reduced, the ground contact shape becomes uniform, and the abrasion becomes uniform. In particular, uneven wear properties are improved.

When the drop (ΔH) in the tread width (TW) is small, the wear resistance is improved, but when it is less than 4%, the bead durability deteriorates, and when it exceeds 6.5%, the wear resistance is increased. And uneven wear tends to occur.

However, when the strain applied to the tread tread portion is reduced, the amount of strain applied to the tire does not change. Therefore, the strain applied to the tread moves from the sidewall portion (2) to the bead portion (3). In particular, the strain concentration on the bead portion increases, and the bead durability decreases.

In order to disperse the strain concentration on the bead portion (3), a protrusion (11) having a triangular cross section is continuously formed in the circumferential direction on the sidewall portion (2) above the bead portion rim flange (10). By providing this, the rigidity of the bead portion (3) can be increased, and the position of the inflection portion during tire running can be adjusted.

The triangular cross-sectional shape of the projection is more rigid than other shapes such as a semicircle and a trapezoid, and can suppress the volume of the rubber at the projection. This is because the properties can be improved and the increase in weight can be suppressed.

Further, the apex (12) of the projection (11)
Is preferably provided between the rim flange (10) and the maximum width portion (13) of the tire, whereby it is easy to secure the rigidity of the bead portion, the deformation of the bead portion is further reduced, and the bead durability is further improved. Can be.

The height (A) of the apex (12) of the projection is 2
It needs to be in the range of 5 mm to 5 mm. If it is less than 2 mm, the bead portion rigidity cannot be obtained, and the durability is not improved. vice versa,
If it exceeds 5 mm, the rubber volume of the bead portion becomes too large, and the durability performance accompanying heat generation deteriorates.

The cross-sectional shape of the triangular projection is preferably a trapezoidal triangle with its apex (12) offset to the rim flange side. The center of the bead rigidity is brought closer to the bead core (5), and the inflection portion is formed. Can be moved to the upper portion of the sidewall portion to further improve the durability of the bead portion.

(Example) As shown in FIG. 2, triangular projections having a base width of 35 mm and a projection apex positioned at 25 mm from the nominal rim diameter are provided continuously on the bead portions on both sides in the tire circumferential direction. Example tire (Examples 1 to 4) having a width drop amount of 5% and comparative tire (Comparative example 1)
４4) and a conventional tire having no protrusion in the tread width drop amount and a comparative test of abrasion resistance and durability were performed. The results are shown in Table 1 below. Each tire was a radial tire having a size of P235 / 75R15, and the internal structure of the carcass layer, the belt reinforcing layer, and the like was the same.

The wear resistance was determined by measuring the distance traveled per 1 mm of wear from the amount of tread wear before and after running the actual vehicle at 30,000 Km by mounting the tire on a 3000 cc four-wheel drive vehicle produced in Japan and performing rotation every 5,000 km. It was calculated and the result was shown as an index with the conventional product as 100. The higher the value, the better.

As for the durability, an air pressure of 180 kPa, a load of 950 Kg, and an indoor drum durability tester were used.
The traveling distance until the occurrence of the failure at a speed of 80 km / h was indicated by an index when the conventional product was taken as 100. The higher the value, the better.

Further, the bead portion distortion of each of the tires was determined by FE
The strain energy density was calculated from the M (finite element method) analysis using a computer. Calculation range is tire pressure 10kPa, applied load 0Kg to air pressure 200kP
a, up to a load of 650 Kg, and the results are shown in Table 1 as an index with the conventional product as 100. The larger the value, the greater the distortion.

Further, in order to confirm the difference in the projection shape, a durability test was conducted on a tire according to Example 3 in which a projection having a semicircular cross section and a trapezoid having a height of 3 mm was provided (the results are not shown in the table). ). It can be seen that the rubber volume of the bead portion is large and the heat generation is about 20% higher than that of the third embodiment, the bead portion failure occurs early, and the triangular shape has an excellent heat radiation effect.

[0033]

[Table 1] As is clear from the above results, in any case, the tires of the example take the tread width drop amount of both tread shoulders in an appropriate range, obtain a uniform ground contact shape, have excellent wear resistance, and have a triangular cross section. The protrusions ensured the rigidity of the bead portion and prevented the bead portion from decreasing in durability.

In Comparative Examples 1, 2 and 3 in which no projections are provided or which are too small, the distortion of the bead portion is large and the durability of the bead portion is inferior. In particular, Comparative Example 1 has a large concentration of strain in the bead portion.
In addition, the result agrees well with the FEM calculation result.

In Comparative Example 4 in which the protrusion height was too high, the rubber volume was large and a bead separation failure occurred due to heat generation, and a decrease in bead durability was observed.

[0036]

As described above, in the pneumatic radial tire according to the present invention, the tread width reduction of both tread shoulders is 4% to 6.5% of the tread width, and the bead on the upper side of the bead rim flange is provided. From the section to the sidewall section,
Triangular cross-section projections that protrude toward the outside of the tire are provided continuously in the circumferential direction, so that the strain applied to the tire is properly dispersed and the rigidity of the bead is ensured, resulting in wear resistance and bead durability. Gender compatibility can be realized.

[Brief description of the drawings]

FIG. 1 is a tire cross-sectional profile illustrating an example of the present invention.

FIG. 2 is an enlarged sectional contour view of a bead portion for explaining an embodiment of the present invention.

FIG. 3 is a half sectional view in the tire width direction showing one embodiment of the present invention.

[Explanation of symbols]

 T ... pneumatic radial tire 1 ... tread portion 2 ... sidewall portion 3 ... bead portion 4 ... carcass layer 5 ... bead core 6 ... belt layer 7 ... tread rubber layer 8 ... shoulder portion 9 ... ... Rim 10 ... Rim flange 11 ... Triangular cross-section protrusion 12 ... Vertex of triangular protrusion 13 ... Tire maximum width position 14 ... Tread equator A ... Vertex height of triangular protrusion B ... Nominal rim diameter R1 ... curvature of tread shoulder R2 ... curvature of shoulder P1, P2 ... intersection of R1 and R2 H1 ... tire height H2 ... distance between nominal rim diameter (B) and P1 and P2 ΔH ... drop in tread width Amount TW ... Tread width

Claims (4)

[Claims] 1. A carcass layer comprising a tread portion, a sidewall portion, and a bead portion, arranged in a code at an angle of substantially 90 ° with respect to the tire equator, and turned over by a bead core;
In a pneumatic radial tire having a radially outer side of the carcass layer and a belt reinforcing layer disposed between the tread rubber layers, the treads on both shoulders of the tread are assembled in a regular rim and filled with a regular internal pressure. The width drop amount is 4% to 6.5% of the tread width, and a triangular cross-section projection that protrudes outward from the tire is provided continuously in the circumferential direction on the sidewall portion above the bead portion rim flange. A pneumatic radial tire characterized by: 2. The pneumatic radial tire according to claim 1, wherein the apex of the triangular protrusion is located on a sidewall portion between a bead portion rim flange and a tire maximum width portion. 3. The height of the apex of the triangular protrusion is 2 mm.
3. The method according to claim 1, wherein the distance is within a range of about 5 mm.
The pneumatic radial tire described in 1. 4. The pneumatic radial tire according to claim 1, wherein a cross-sectional shape of the triangular protrusion is a trapezoid having a vertex offset toward a rim flange.