JPH01317814A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To aim at improving mainly the durability by specifying the relative position relationship between the lowering and hoisting sides in the packed area of a bead filler in the carcass layer rewound from inside to outside around a bead core. CONSTITUTION:In the state of a tire fit into a rim 1, the point that the outside wall of a bead part starts clearing from the inflexed face of a rim flange 3, P1, the points that the normal line descending from P1 toward the inside of the tire and rewound carcass layers 7, 8 intersect, P2, P4, and the point that the normal line descending from the rewound end P3 of the carcass layer 8 toward the inside of the tire and the carcass layer 7 intersect, P5 are set respectively. The carcass lines P4, P5 of the area of connecting P2, P4, P5, P3 successively and P2, P3 are set mutually parallel or set such as to oppose from the bead wire side 4 toward the end of the carcass layer. The separation in the rewound end P3 of the carcass is thus prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a heavy-duty radial tire (hereinafter simply referred to as a heavy-duty tire) with improved durability, particularly a tube-type IR or IRA bead seat. This invention relates to a heavy-duty tire that is mounted on a flat-bottomed rim and has improved bead durability.

[Conventional technology]

Conventionally, it has been said that the durability of the bead part of a heavy-duty tire is closely related to the concentration of strain at the end of the rolled-up carcass layer of the bead part. However, the concentration of strain at the end of the winding of the carcass layer can be caused by various factors, and the present situation is that it has not been fully elucidated.

The inventors of the present invention conducted extensive research into the cause of the separation at the end portion of the carcass layer that is rolled back, and found the following.

Conventionally, a carcass line design method in the bead area of this type of tire has been proposed, for example, by Japanese Patent Publication No. 52-2600.
No. 3 and Japanese Patent Publication No. 54-30561, the shape minimizes deformation before and after filling the internal pressure,
There is a technique that attempts to reduce the concentration of strain on the end portion of the carcass layer when it is rolled back.

In addition, in this case, for the triangular composite filler that is interposed between the carcass layer being rolled up from the inside to the outside around the bead core, the distortion of the terminal is reduced by defining the interval between the end of the carcass on the winding down side and the winding side. Japanese Patent Laid-Open No. 155108/1983 discloses a technique for this purpose.

In this case, in tires filled with high internal pressure such as heavy-duty tires, it is practically difficult to completely prevent the change in the carcass line. The carcass line (A) normally changes to the carcass line (B) after internal pressure filling.

Furthermore, due to the internal pressure filling, the carcass line, which is once in equilibrium, undergoes repeated deformation in the lateral direction and changes as the vehicle travels. In this case, the carcass line changes as shown in Figure 2. In the initial run, the carcass line (B) after filling with internal pressure changes to the carcass line shown in (C), and then as the carcass line continues to run, , from the carcass line of (c) (
The carcass line changes to (d) and assumes a stable shape after traveling a substantially constant distance.

What should be noted about such carcass line changes is that the area where the carcass line changes the most is (
(refer to Figure 1), the carcass layer is unrolled at a point halfway in the width direction between the point P+ where the curved surface of the rim flange and the outer wall of the tire bead begin to separate from each other, and the point P7 at the maximum of the carcass line. In the temporal region A, the relationship between the amount of change in the end portion of the carcass layer unwinding and the amount of change in the carcass line in the temporal region A where the carcass layer is unrolled is as follows: After internal pressure filling, Dt ≧d.

After the initial run, Dt>dz After the middle of the run, D:l >>dz It is to be.

Therefore, the carcass line on the carcass layer unwinding side comes close to the carcass cord radial extension line of the carcass layer unwinding terminal, and when the tire is loaded, a phenomenon of bumping against the carcass layer winding terminal occurs, and the Strain concentration increases at the terminal, leading to separation, and the durability of the bead portion is greatly impaired.

On the other hand, as a means to prevent the above-mentioned change in the carcass line and improve the durability of the bead, the material, number, etc. of the bead reinforcement layer are selected to reduce the initial "settling" phenomenon of the carcass line to some extent. However, there is a limit to the effect of improving bead durability, and there is a risk of new separation from the reinforcing layer.

[Problems to be Solved by the Invention] The object of the present invention is to solve the "settling" phenomenon of the bead part that occurs with repeated running in the separation of the end part of the carcass layer of the bead part of the above-mentioned heavy-duty tire. The object of the present invention is to suppress changes in the carcass line caused by this, suppress concentration of strain on the end portion of the carcass layer rolled back, and improve the durability of a heavy-load tire.

[Means to solve the problem]

The present invention forms a composite bead filler layer made of hard rubber and soft rubber filled on the bead core between a carcass layer made of a single layer of stiffle cord wound around the bead core from the inside to the outside of the tire. The tire has a reinforcing layer fitted along the outer side of the rolled-up carcass layer obliquely to the carcass cord, and when the tire is mounted on the rim, the tire can be removed from the curved surface of the rim flange. The point PI where the outer wall of the bead part starts to separate
, Points Pt and Pa where the normal line drawn down toward the inside of the tire from this point P+ intersects the unrolled and rolled up carcass layer, and the inside of the tire from the unrolling terminal P3 of the carcass layer (carcass layer unrolling side) Carcass line P in the area surrounded by point Pu, point P4, point P, and point P3 among the points P where the normal line drawn toward the carcass layer intersects with the carcass layer.4. P s and carcass line P
2. Ps are arranged in parallel or separated from the bead wire side toward the end of the carcass layer.

That is, the tire of the present invention has the points Pz, P4, and ps.
and the carcass line P a = P s of the bead filler filling area surrounded by point P3 and the car man line Pz, P
s in parallel or away from the bead wire side toward the carcass layer end, that is, in FIG. ps ) 1, <1
2, the "sag" caused by the lateral deformation caused by running, as described above, can be reduced by changing the carcass line of area A shown in FIG. ), the carcass layer unwinding side is not located on the extended line of the carcass layer unwinding terminal in the carcass cord direction, suppressing the poking phenomenon of the carcass layer unwinding terminal, and reducing the carcass layer unwinding end at the bead portion. It is possible to prevent separation of the parts and improve the durability of the tire.

Here, as shown in FIG. 1, carcass lines Pz, P4
The ratio of the soft rubber of the composite filler filled in the lower bead core side is preferably 0.15 or less in terms of area ratio to the cross-sectional area below the carcass lines Pz and Pa. This makes it possible to strengthen the bead core side, making it difficult for the carcass layer to slip off. Also, point P
2. The proportion of soft rubber in the area connecting P8, P, and P4 is 0.70 as an area ratio to the total cross-sectional area of this area.
It is preferable to make the bead filler layer more flexible, since this makes the bead filler layer relatively flexible and allows it to exhibit a stress relieving effect.

In the present invention, the hard rubber preferably has a JIS hardness of 70" or more, and the soft rubber preferably has a JIS hardness of 100 or more lower than the hard rubber.

Further, in the present invention, it is preferable that the height of the rim flange when assembled from the rim reference line and the height hc to the carcass winding end satisfy the following relationship.

hc= (1,25~1.85) x ht this paste,
Take, hc < 1.25 h.

This eliminates the above-mentioned sticking phenomenon of the end of the carcass roll-up under load, but the end of the roll-back ends up receiving a strong reaction force from the rim flange, which improves the durability of the rim part. There isn't. Also, hc > 1.85 h.

When this happens, the carcass line approaches the maximum area A of change, and the lateral stress applied to the end portion of the winding increases, making it impossible to avoid a decrease in the durability of the bead portion.

Furthermore, the thickness (T) between the bead part outer wall P, which intersects the normal line lowered from the carcass layer unwinding end P to the carcass layer unwinding side (inside the tire), and the carcass layer unwinding side (T) is aligned with the carcass line. It is desirable to form a bead shape (bead profile) that is maximal.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

The tire size is 10.00R2014PR, and the durability is as follows: air pressure 9.00Kg/cm", load 52
The evaluation was made by running the tire under conditions of 00 kg and a speed of 45 km/hour until separation occurred at the end of the tire.

The rim used is 7.0OTx20 (the bead seat shape is an IRA rim, and the rim flange height is 38° Omo).
+).

The evaluation results were expressed as an index with the result of the conventional tire set as 100.

Example 1.2, Conventional Example As shown in FIG. 1, in the tire having a one-bead structure, as shown in the table, the carcass line P4. Ps and carcass line Pz, P
Three types of tires were created with different relationships with x.

In addition, in these tires, the shape of the carcass line on the carcass layer unwinding side is the same, and P, , P
b have the same thickness, and a composite filler of hard rubber with a JIS hardness of 72" and soft rubber with a JIS hardness of 58° is used as the bead filler. The area ratio was set as SOW, the area ratio of the soft rubber occupying the core side below the carcass lines P2 and P4 was set as 8χ, he was set as 60 mm, and t+ was set as 9.0 mm.

The durability of these tires was evaluated and the results shown in the table were obtained.

From the table, the tire of the present invention has significantly superior durability compared to conventional tires.

〔Effect of the invention〕

In the tire of the present invention, the relative positional relationship of the carcass layer on the unrolling side and the rolling side in the bead filler filling region is specified in the carcass layer that is wound back from the inside to the outside around the bead core of the tire. According to this specification, the carcass line fluctuates due to "sagging" caused by lateral deformation during driving, and the unwinding side of the carcass layer is located on the extension line in the tire radial direction of the unwinding end of the carcass layer. This prevents separation of the end of the carcass layer from being rolled back, which is caused by the bumping phenomenon between the unrolling side and the end of the carcass layer, thereby significantly improving the durability of the tire.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the bead region of the tire of the present invention, and FIG. 2 is a sectional view showing changes in carcass lines in the tire bead region. DESCRIPTION OF SYMBOLS 1... Rim, 4'... Bead core, 5... Hard rubber, 6... Soft rubber, 7... Carcass layer winding-down side, 8... Carcass layer winding-up side. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] At least one carcass layer of radially disposed steel cord is wound around the bead core from the inside of the tire to the outside, and the carcass layer is filled between the rolled carcass layers and over the bead core. A tire having a bead filler made of hard rubber and soft rubber, and at least one cord reinforcing layer disposed obliquely to the carcass cord along the outside of the rolled-up carcass layer, When this tire is fitted to the rim, there is a point P_1 where the outer wall of the bead of the tire begins to separate from the curved surface of the rim flange, a normal line drawn from this point P_1 toward the inside of the tire, and Points P_2, P_4, P_5 and A radial tire for heavy loads, characterized in that carcass lines @P_4, P_5@ in the area sequentially connecting point P_3 and carcass lines P_2, P_3 are configured to be parallel or to be separated from the bead wire side toward the end of the carcass layer.