JPH0350004A - Heavy duty pneumatic tire - Google Patents

Abstract

PURPOSE:To improve durability of a bead portion of a tire for a bus and the like mentioned in the subject by arranging an annular isolating rubber layer, which has the same circumferential length as a carcass layer and is butted at both ends in the longitudinal direction, on the carcass layer, and by folding back and curling up both of the carcass and the annular isolating rubber layer around a bead core. CONSTITUTION:An annular isolating rubber layer 7, which has almost the same circumferential length as that of a carcass layer 4 and is butted at both ends in the longitudinal direction, is arranged at a required position of the carcass layer 4. A layer reinforced with steel cord 5 and an inner liner 9 are arranged under the carcass layer 4. The carcass layer 4 and the annular isolating rubber 7 are folded back and curled up around a bead core 2. By this constitution, a circumferentially overlapped spliced portion of the isolating rubber can be eliminated. Consequently, tire uniformity and durability of the bead core portion can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy-duty pneumatic tire with excellent tire uniformity.

[Conventional technology]

Heavy-duty pneumatic tires used for large vehicles such as trunks and buses generally have a bead portion as shown in FIG. 7. In FIG. 7, 1 is a bead portion, and in this bead portion 1, a bead core 2 having a hexagonal cross section is arranged annularly in the tire circumferential direction. On the trend side of the bead core 2, a bead filler 3 consisting of a lower bead filler 3d and an upper bead filler 3u is attached to the bead core 2.
is located adjacent to.

Around this bead core 2, the end portion of the carcass layer 4 is folded back from the inside of the tire to the outside and rolled up along the bead filler 3. 5 is a steel cord reinforcing layer that protects the carcass layer 4, and 6 is a rim.

In a tire having this bead portion l, the bead core 2 and the carcass layer 4 come into contact with each other during running at the corner portions a, b, c, and d of the bead core 2, and the bead wire constituting the bead core 2 and the cord of the carcass layer 4, i.e. The carcass cords rub against each other, causing the carcass cords to wear out. If the wear progresses excessively, the carcass cords may break, causing serious problems with the tire.

Conventionally, in order to prevent such abrasion of the carcass cord, as shown in FIG. There is a separation between 4 and 4.

FIG. 8 shows an enlarged view of the bead core 2 in FIG. 7.

In FIG. 8, an insulating rubber layer 7 is placed on the surface of a bead core 2 having a hexagonal cross section and made up of a plurality of bead wires 8, so that the bead core 2 is wrapped around it.

However, when wrapped in this way, the ninth
As shown in the figure and FIG. 10, the wrapping start end and the wrapping end end of the insulating rubber layer 7 overlap, resulting in a circumferential splice overlap portion A having a width. When the circumferential splice overlap portion A occurs in this way, the bead core 2 is located close to the rim, which greatly affects the uniformity of the tire, resulting in poor tire uniformity. Defects in tire uniformity cause problems such as vehicle body vibration when the tires are mounted on a vehicle and the vehicle is running. In addition, the folded part of the carcass layer in contact with this circumferential splice overlap part A becomes loose, and when the tire is assembled to the rim 6 and the internal pressure is filled, the internal pressure causes the carcass layer to
This causes problems such as the carcass layer winding terminal 4a becoming easy to move and separation occurring at this terminal 4a.

[Problem to be solved by the invention]

The present invention improves tire uniformity by preventing circumferential splice overlaps from occurring in the insulating rubber layer,
Another object of the present invention is to provide a pneumatic radial tire for heavy loads that suppresses the occurrence of separation at the winding end of the carcass layer and improves the durability of the bead portion. recent years,
Even pneumatic radial tires for heavy loads are required to have stability at high speeds, and in particular, emphasis is placed on retreadability, and tire lifespans such as secondary and tertiary lifespans are required. It is important to improve the durability of the bead and the durability of the bead.

[Means to solve the problem]

In the heavy-duty pneumatic radial tire of the present invention, the ends of one or more carcass layers are folded back and rolled up around a bead core from the inside of the tire to the outside, and insulation is provided between the bead core and the carcass layer adjacent to the bead core. In a tire having a bead portion with a rubber layer interposed therebetween, an annular insulating rubber layer is disposed on the carcass layer, the longitudinal ends of which have a circumference substantially equal to the circumference of the carcass layer are attached to each other, It is characterized in that this insulating rubber layer is folded and rolled up around the bead core together with the carcass layer.

This means will be explained in detail below with reference to the drawings. Note that the same parts and parts as in FIGS. 7 to 1O are indicated by the same numbers.

In manufacturing the tire of the present invention in which no circumferential splice overlap occurs in the insulating rubber layer, first, as shown in FIG. An annular insulating rubber layer 7 is placed in advance, the longitudinal ends of which have a circumference substantially equal to the circumference of the layer 4 are attached to each other. Further, under the carcass layer 4, a steel cord reinforcing layer 5 and an inner liner 9 are appropriately arranged.

Next, as shown in FIG.
Fold it around and roll it up. The bead core 2 can have a cross section of various polygonal shapes such as a quadrangle, a heptagon, and a hexagon. The insulating rubber layer 7 is made of a rubber composition in which a rubber such as natural rubber or styrene-butadiene copolymer rubber (SBR) is blended with a compounding agent such as carbon black. Furthermore, it is preferable that the insulating rubber layer 7 has a JIS hardness of 80 or more, preferably 85 to 98, and is harder than the bead filler 3.

In this way, it is possible to obtain a heavy-duty pneumatic tire of the present invention having a one-domain structure as shown in FIGS. 3 and 4. In FIGS. 3 and 4, there is no circumferential splice overlap A as in FIGS. 9 and 10, respectively. Further, in FIG. 3, both ends of the insulating rubber layer 7 do not extend upward beyond the bead core 2, whereas in FIG. 4, the insulating rubber layer 7
Both ends of the bead filler 3 extend beyond the bead core 2.
The two figures differ in that the line extends upward along the line.

Corner a of the bead core 2 in FIGS. 3 and 4,
For b, c, and d, the thickness of the insulating rubber layer 7 at the corner near the center in the width direction of the rim 6 (that is, the distance between the bead core 2 and the carcass layer adjacent to this bead core 2) is It is preferable that the thickness of the insulating rubber layer 7 is greater than the thickness of the insulating rubber layer 7 at the other corners. This is because the abrasion force by the carcass layer is most applied to the corners while the vehicle is running. For example, the thickness of the insulating rubber layer 7 at the corners a and b is 1.5 to 2°5II.
Im, the thickness of the insulating rubber layer 7 at the corners c and d is 0°4~0
．． 5 ffIm is recommended. In addition, in this way, the corner a
, the thickness of the insulating rubber layer 7 at b is 1. When the thickness is set to 0 mm or more, the thickness of the insulating rubber layer 7 at the corners c and d is preferably thinner. This is because the thinner the carcass layer is, the more effective it is in suppressing the movement of the carcass layer winding terminal and suppressing the occurrence of separation at that terminal. For this purpose, it is preferable to arrange an insulating rubber layer 7 having partially different thicknesses on the carcass layer 4 as shown in FIG. 5 when manufacturing the tire. As a result, a heavy-duty pneumatic tire having a bead structure in which the thickness of the insulating rubber layer 7 is the largest at the corners as shown in FIG. 6 can be easily obtained by following the molding procedure according to the present invention.

Examples are shown below.

Example The tire uniformity of the tires of the present invention and conventional tires described below was evaluated by measuring the vertical runout during running using the method described below.

The results are shown in Table 1.

■ Tire of the present invention.

A sheet-like carcass material made of a heavy-duty pneumatic tire of tire size IIR22.5 or a rubber-coated steel cord was cut at 90 degrees to the cord to form a carcass layer, as shown in Figures 1 and 2. like,
Insulating rubber layer on carcass layer (thickness 1.0mm x width 32m)
m), the inner liner and the steel cord reinforcement layer are bonded in advance, the bead material is bonded with the bead filler to the bead core, and the carcass layer is folded back on the forming drum, and then the rim cushion rubber, side tread, belt layer, and cap are formed. After attaching the tread etc., it was made into a product through a vulcanization mold.

■ Conventional tires.

Heavy load pneumatic tire with tire size IIR22.5. As shown in Fig. 8 to Fig. 1θ, the bead core is wrapped around the bead core with an insulating rubber layer (thickness 1.0 ms), and the width of the circumferential splice overlap portion is set as 10III11 to form the bead portion shown in Fig. 7. It was made into a structure.

Toyogo regular plate fixed 1 wide rim 22.5 x 8.25 precision rim for runout measurement (production online M/C), part of tread crown center and part of tread shoulder under the condition of air pressure 5.0 kgf/cd. Vertical runout was measured. In this case, for each 50 samples of the same size produced in parallel, the value (am) above the average value (95χ confidence interval) at the Tre 7 crown and part of the trend shoulder. evaluated. Note that the confidence interval here refers to the range in which the parameter falls between the average value and the interval with a probability of 95%.

4. As is clear from Table 1, there is no particular difference between the tire of the present invention and the conventional tire in the tread crown portion, but it can be seen that the tire of the present invention is superior in a portion of the trend shoulder. That is, in a part of the trend shoulder, the average value of longitudinal runout is clearly larger in the conventional tire than in the tire of the present invention. This is an indication of non-uniform fit between the rim and the tire, and therefore conventional tires have poor tire uniformity.

〔Effect of the invention〕

As explained above, according to the present invention, the insulating rubber layer is attached to the carcass layer first and the circumferential splice overlap part of the insulating rubber layer as in the conventional method is eliminated, thereby improving tire uniformity. It is possible to improve the durability of the bead portion by suppressing the occurrence of separation at the winding end of the carcass layer, which is caused by the carcass layer folding being likely to be loose at the circumferential splice overlap portion.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams showing an example of the method for manufacturing a pneumatic tire for heavy loads according to the present invention, and FIGS. 3 and 4 are cross-sectional views of an example of the bead portion of the pneumatic tire for heavy loads according to the present invention, respectively. FIG. 5 is an explanatory diagram showing the other side of the method for manufacturing a heavy-duty pneumatic tire of the present invention, and FIG. 6 is a cross-sectional explanation of an example of the cord part of a heavy-duty pneumatic tire obtained by this method. It is a diagram. FIG. 7 is an explanatory cross-sectional view showing an example of the structure of a bead portion of a conventional pneumatic tire for heavy loads, FIG. 8 is an enlarged cross-sectional view of the bead core, and FIG. 9 is an explanatory side view of the bead core.
FIG. 10 is an enlarged explanatory view of section A in FIG. 9. l...Bead portion, 2...Bead core, 3...Bead filler 3d...Lower bead filler 3u...
Upper bead filler, 4... Carcass layer, 5... Steel cord reinforcing layer, 6... Rim, 7... Insulating rubber layer, 8... Bead wire. Figure Figure Figure Figure m Clause, 0

Claims (1)

[Claims] A tire having a bead portion in which an end portion of one or more carcass layers is folded back and rolled up around a bead core from the inside of the tire to the outside of the tire, and an insulating rubber layer is interposed between the bead core and a carcass layer adjacent to the bead core. In this step, an annular insulating rubber layer is placed on the carcass layer, and both longitudinal ends of the circumference are attached to each other, and the insulating rubber layer and the carcass layer are placed around the bead core. A pneumatic tire for heavy loads that is folded back and rolled up.