JPH0495502A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To prevent the interval between bead parts from being narrowed due to heat shrinking of a carcass by post-cure-inflation after tire curing by forming a second ply by cords having greater heat shrinkability than that of cords consisting a first ply. CONSTITUTION:A carcass 2 consists of two plies in which rubber-sheathed radial arrangement cords are arranged, that is, consists of a first ply 9 spreading over between a pair of bead wires 1 and having a bent back part 8 which is turned from the inside to the outside in the axial-direction of a tire around the bread wire 1 to further extend along a hard rubber filler 4, and a second ply 10 similarly spreading over between the bread rings 1 and extending along the outside of the bent back part 8 in the axial direction of the tire toward the bead heel of the bead part 3. In this case, heat shrinkability of the second ply 10 is determined to be grater than that of the first ply 9. That is, the quality of the material of the cords of the second ply 10 is different from that of the cords of the first ply 9, and for example, the difference in shrinkage factor between both the plies is about 25%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bead structure that enables reliable rim assembly in a pneumatic radial tire, particularly in a pneumatic radial tire for automobiles.

PRIOR ART Automotive pneumatic radial tires generally consist of a radially arrayed ply of rubber-coated steel cords straddled in a toroidal manner between a pair of bead wires, with a respective inner tire around each bead wire. The carcass is made of a ply having a folded part of the above ply that is wound back and extends outward from the ply, or a second ply is further arranged to extend toward the heel along the outer side of this ply in the axial direction of the tire.The carcass serves as body reinforcement. is taken as an example.

(Problems to be Solved by the Invention) When assembling a tire onto a rim, it is important to bring the tire's heel from the heel base to the flange of the rim uniformly and closely together without any gaps. This includes the bead-to-heel distance (
It is essential to set the distance (hereinafter referred to as "peed part interval") to a range corresponding to the flange interval of the rim, that is, a width slightly larger than the flange interval.

Here, the tire bead spacing is based on the mold shape and post-cure inflation after tire vulcanization (hereinafter referred to as P).
(abbreviated as CI). Among these determining factors, since the mold shape can be adjusted to desired dimensions, molding can be performed at a predetermined interval between the peas. On the other hand, the tire taken out of the mold after vulcanization is placed in a device that simulates the regular rim of this tire, filled with a predetermined internal pressure, and exposed to the outside air until the next tire or the tire after that is completely cured and cooled. In PCI, it is difficult to secure the necessary distance between the heed parts because the heat shrinkage of the carcass inevitably causes the heed part interval to become narrower than the normal interval.

Therefore, an object of the present invention is to propose a pneumatic radial tire having a bead part structure in which the bead part spacing does not narrow due to heat shrinkage of the carcass in PCI.

(Means for Solving the Problems) The present invention includes a carcass consisting of a ply of radially arranged cords extending in a toroidal manner between a pair of bead portions, and a belt layer consisting of a non-extensible cord disposed at the crown portion of the carcass. The carcass has a folded part of the ply that extends from the inside in the axial direction of the tire to the outside around a bead wire embedded in each bead part and a hard rubber filler placed on the bead wire. In a pneumatic radial tire having a first ply and a second ply extending toward the bead heel along the axially outer side of the tire at this folded portion, the second ply is made of a cord that is more heat-shrinkable than the cord constituting the first ply. It is a pneumatic radial tire with a large cord.

Now, FIG. 1 shows a cross section of the left half of a pneumatic radial tire according to the present invention. In the figure, 1 is the bead wire with only one side shown, 2 is the carcass, 3 is the pead part,
4 is a hard rubber filler placed on the bead wire 5
6 is a belt layer, 6 is a tread rubber, and 7 is a sidewall rubber.

The carcass 2 is made up of plies of rubber-coated radial array cords arranged in two layers in the illustrated example, and extends across a pair of bead wires 1 in a toroidal manner, and extends around the bead wires 1 and the hard rubber filler 4. A first ply 9 having a folded part 8 of the ply which is wound from the inner side to the outer side in the axial direction of the tire and further extends along the hard bum filler 4; and a second ply lO extending along the axially outer side of the tire No. 8 toward the bead heel of the peal portion 3. Note that the first and second plies are shown as an example of one ply each, or may be a plurality of plies, and if the carcass is an odd number of layers of three or more, the first ply is replaced with the second ply.
The structure has one more ply.

Here, it is important that the second ply 10 has higher heat shrinkability than the first ply 9. In other words, the cord of the second ply 10 and the cord of the first ply 9 are made of different materials, and the heat shrinkage rate of both is adjusted. The combination is such that the difference between the values is approximately 5%. Specifically, the cord of the first ply 9 is made of polyester (1000d
/2.1500 d/2 etc.) and the second ply 10 cord is made of nylon (840d/2.126°d/2 etc.).

The hard rubber filler 4 is tapered in thickness from the base disposed on the bead wire 1 toward the outside in the radial direction of the tire.
It is disposed inside the folded portion 8 of the ply 9 in the axial direction to ensure the lateral rigidity of the tire and also serves to maintain a predetermined distance between the first ply 9 and the second ply 10.

The belt layer 6 is composed of multiple layers of rubber-coated non-stretchable cords laminated around the outer periphery of the crown portion of the carcass 2, and is embedded in the tread rubber 6 to serve for reinforcement of the tread portion. Please follow the customary practices for this type of tire.

(Function) If the carcass, which is the frame of the tire, is made up of the above-mentioned first and second plies, so-called up-down structure, and the second ply is made of a material with greater heat shrinkage than the first ply,
Due to the heating during the tire vulcanization process, there is a difference in the amount of heat shrinkage between the first ply and the second ply, and the second ply has a larger heat shrinkage than the first ply, so the axially outer part of the sidewall This results in tension or shrinkage, and therefore, during the PCI process after vulcanization, the second ply is subjected to greater tension than the first ply. Then, in the tire during the PCI process, stress in the direction of increasing the radius of curvature is effectively applied to the area of the sidewall, particularly the rubber filler 4, which is widely separated from the first and second plies, and the gap between the heel parts is widened.

By widening the interval between the bead F parts, preferably in the range of 95 to 120% of the flange interval of the rim, rim assembly can be performed reliably, and the bead part is evenly adhered to the entire circumference of the rim flange, allowing air to flow through the rim. filling becomes easy.

Also, since there is no gap between the tire and the rim that leads to uniformity, you can expect the tire's original performance.

Note that the interval between the bead parts can be changed by adjusting the thickness of the hard rubber filler placed between the first ply and the second ply.

(Example) According to the structure shown in Fig. 1, tire size 195/6
Five 5R14 pneumatic radial tires were prototyped for each specification according to the specifications shown in Table 1. In addition, in the same table, the first
α, β, γ and t shown in Figure 2, which is an enlarged view of the bead part in the figure.
The dimensions are shown. Here, α is the height of the folded end of the carcass from the perpendicular line passing through the heel of the heel and lowered to the equatorial plane of the tire, β is the height of the base of the hard rubber filler, and γ is the height of the tapered end of the hard rubber filler. and t respectively indicate the width of the hard rubber filler base.

In all of the test tires, the belt layer was made of steel cord ((
It was made into a two-layer cross-layer consisting of I X 5 ) Xo, 23). Also, the spacing between the heat parts in the mold is 140mm.
, and the bead spacing in the tire just before PCI is 1
It was 52 mm.

Each test tire mentioned above is size 5 V2JJ
After installing it on the rim of 4 and visually inspecting the fit, 1
．． An air filling test up to 8 kgf/cm2 was conducted.

The results are shown in Table 2.

Table 1 Table 2 (ne) Pet: Polyester cord, Ny, nylon cord However, for tires Nα3 and 4, the heat shrinkage rate was changed between the first ply and the second ply by treatment of the ply cord.

(*1) Rim width 5.5 inches (139.7mm) (*2
) ◎... Very good ○... Good △... Not so good (Effect of the invention) According to this invention, even after PCI, the bead gap does not narrow, so the tire is securely attached to the rim. It can be easily installed in the tire, it can be easily filled with air, and the original performance of the tire can be fully utilized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the tire of this invention. FIG. 2 is an enlarged view of the heat section of the tire shown in FIG. 1. 1...Bead wire 3...Bead part 5...Belt layer 7...Side wall rubber 8...Folded part of ply 10...Second ply 2... carcass 4...Hard rubber filler 6...Tread rubber 9...1st ply

Claims (1)

[Scope of Claims] 1. A carcass comprising a ply of radially arranged cords extending in a toroidal manner between a pair of bead portions, and a belt layer comprising a non-extensible cord disposed at the crown portion of the carcass, a first ply having a folded portion of the ply extending from the inside in the axial direction of the tire to the outside around the bead wire embedded in each bead portion and the hard rubber filler placed on the bead wire; In a pneumatic radial tire, the second ply extends along the axially outer side of the tire toward the bead heel at the turn-up part, and the second ply is made of air that becomes a cord with greater heat shrinkage than the cord constituting the first ply. Includes radial tires.