JPH0417805B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in tires.

More particularly, the present invention relates to a tire casing structure, and more particularly to a tire casing structure with a radial carcass, and in particular to a tire casing structure with a radial carcass reinforced with at least one metal ply. It is something. The lower portion of each side of the tire casing, referred to as a "bead," includes a carcass end portion that is wound outwardly around a bead core. In general, "apetskus"
A molded strip consisting of one or two parts of rubber layer, called a molded strip, is placed over the bead core, along the sides, between the carcass ply and its roll-up. The apex extends along the sides to a certain height, and its thickness gradually tapers. Such tire casing structures are used especially for heavy vehicles.

In known casing constructions, one or two layers of steel cord reinforcing plies sloped relative to the bead core provide reinforcement in this area and increase its stiffness. Additionally, the bead has a relatively soft rubber molded component that is bonded to the steel reinforcing ply and acts as a shock absorber. A covering layer of hard rubber is then bonded which resists the wear caused by friction between the bead and the wheel rim on which the tire rests in use.

FIG. 1 of the accompanying drawings shows an example of a casing structure of this known type in partial cross-section, showing in particular the bead portion thereof.

The casing has a radial carcass 10, on top of which is a breaker layer 12 laminated on the side closest to the tread 14. The casing ends at the bead 16 on the side of the wheel rim (reference number 15). More specifically,
This bead is formed by the end portions of the carcass, which are rolled up around a bead core 22 and extend upwardly and outwardly into the rolled up section 2, as indicated by the reference numerals 18 and 20.
form 0. The apex 24 made of relatively hard rubber includes a carcass 10, a bead core 22,
and the winding portion 20, and tapers and disappears in its outer radial portion.

In the known state of the art, the reinforcing ply 26 (first
(only one layer is shown in the figure) is placed on the outside of the roll-up 20 to strengthen and stiffen this area. More specifically, these plies are usually reinforced by metal cords or textile fiber cords, which are parallel to each other and inclined at a slight angle to the circumferential direction of the tire.
The cords thus intersect with the carcass windings 20 to form a rigid network.

FIG. 1 shows a single component 28 in which the bead portion 16 is also molded from relatively soft rubber, and a reinforcing ply 28.
6 and has a hard rubber coating layer 30 extending around the entire bead to resist wear caused by friction between the bead and the wheel rim on which the tire rests in use. It is shown that.

Tire casing constructions of the type described above have the disadvantage that they require a great deal of care and a high level of precision in the manufacturing process. In fact, the reinforcing ply
They must be precisely cut, transported, and installed using expensive tools. The internal movements that inevitably occur during vulcanization lead to displacement of these plies, so that the tire casing produced is sometimes completely unusable. For this reason, systematic depth probing techniques must be used to eliminate these defective tire casings.

It has already been proposed to eliminate reinforcing plies from this type of tire casing construction. For example, French Patent No. 1 343 402 discloses a bead made of very hard and elastic rubber that tapers off at the side of the tire casing in the radially outer part of the tire casing and in the radially inner part of the tire casing. The manufacture of a tire casing having a bead with an apex extending towards the rim rubber is described. In the embodiment described therein, the bottom of the apex is bifurcated, and the ply turn-up is located in the gap between the two limbs of the bifurcation. The axially outer limbs of this apex extend firmly in the direction of the bead seat, so
As a result, it is shown that a tire is formed in which the apex and the clinch strip are integrated.
(A clinch strip is a strip of hard rubber built into the bottom of the sidewall of the tire casing to prevent wear from rubbing against the wheel rim.) These tires have several drawbacks. . First of all, the assembly of the parts of the carcass on the roll-up before vulcanization causes problems, and the bond between the edges of the fabric and the rubber is often very inadequate. Furthermore, in use it has been found that tires with beads of this type do not have the required quality.

Tire casing structures in which the outside of the bead is protected by a hard rubber part are also known. This hard rubber part is located on the outside of the rollup, but the bead does not have an apex. Such beads do not have sufficient rigidity.

Therefore, an object of the present invention is to provide a tire casing structure in which the bead portion has sufficient strength without requiring a reinforcing ply for the bead portion.

According to one aspect of the invention, a tire casing structure includes at least one radially arranged ply extending from one bead core to the other of the bead portions around both bead cores from the inside of the bead portion to the bead portion. The tire casing structure is rolled up outwardly, and an apex rubber layer 44 that is immediately adjacent to the bead core and gradually tapers outward in the radial direction is disposed between the carcass ply 30 and its rolled up portion 40. It is adjacent to the immediate outside of the winding part 40 and is in direct contact with all the winding parts 40 including the winding terminal part 60, and also extends radially outward of the winding part 60 and is in direct contact with a part of the apex rubber layer 44. The bead reinforcing rubber layers 46, 52 are provided with no reinforcing filament at all, and the modulus of the bead reinforcing rubber layers 46, 52 is greater than the modulus of the apex rubber layer 44. The radial dimension h of the bead reinforcing rubber layers 46 and 52 measured with reference to the plane perpendicular to the tire rotation axis is 20 to 20 of the radial dimension H of the tire casing.
60%, and the maximum thickness t of the bead reinforcing rubber layers 46, 52
is 5 to 30% of its radial dimension h.

Preferably, the modulus of the rubber of this bead reinforcement rubber layer is at least twice that of the apex rubber. More specifically, the rubber of this bead reinforcing rubber layer has a stabilized modulus at 20% elongation of at least 1.5 MPa and a shore A hardness equal to at least 75°, while the apex rubber
The stabilizing modulus at 20% elongation is only about 0.65 MPa, and the shore A hardness is about 65°.
It's advantageous. The meaning of the "stabilization" modulus is as described below.

The bead includes a rubber coating layer 50, which is preferably disposed at least in the portion that contacts the wheel rim on which the tire is mounted in use, and serves to prevent rim slippage. In certain embodiments of the invention, the bead reinforcing rubber layer and the covering layer are integrally formed as a single component.

The above design has several advantages. The first is that the molded casing has an extremely long fatigue life. Secondly, no particular problems arise in the manufacture of the tire casing. This is because the internal movement of each component during vulcanization is less than that of the reinforcing ply seen in the prior art, and the edges have fewer drawbacks. In this way, manufacturing precision can be increased. Furthermore, when the structure is formed integrally with the covering layer,
The number of components incorporated into the tire casing is reduced, thus reducing the cost of the casing.

Preferably, the carcass is of radial construction comprising single or multiple plies, each ply comprising a plurality of parallel reinforcing cords, e.g. cords of flexible material such as nylon, Kevlar, or inorganic fiber material such as steel wire. Consists of the code.
Preferably, the reinforcing cord has a high modulus, for example a modulus greater than 2500 Kg/cm ² .

The bead core may have any known structure, such as a cable, creel, or concentrator wire, and may have any desired cross-section, such as circular, hexagonal, or rectangular cross-section. Preferably, the bead core is substantially non-stretchable.

The invention will now be described in more detail, by way of example only, with reference to FIGS. 2 and 3 of the accompanying drawings (FIG. 1 has already been described).

Referring to FIG. 2, the illustrated casing structure includes one or more layers of reinforcing plies, the terminations of which are indicated by numerals 38 and 40.
It is wound outwardly around a bead consisting of a bead core 42 and an apex strip 44 made of rubber. Apex strip 44
is sloped towards its radially outer tip and projects beyond the end 60 of the carcass roll 40. The bead reinforcing rubber layer 46 in the form of an annular strip has a higher modulus than the apex strip rubber and has a radially inner end extending around the periphery of the bead and located at the bead heel, but not in contact with the carcass winding 40 and the apex. It is located axially outwardly adjacent to and in direct contact with a portion of the thread strip 44. The cross section of the bead reinforcing rubber layer 46 extends radially outward from the heel of the bead to a position below the radially outer tip of the apex strip 44. The maximum width t of the bead reinforcing rubber layer 46 is adjacent to the radially outer side of the carcass roll-up section 40 . The cross section of this bead reinforcing rubber layer 46 tapers outward in the radial direction to a predetermined point. A hard rubber anti-rim slip coating layer 50 is placed axially adjacent the bead reinforcement layer 46 and extends below the bead bottom and around the toe of the bead. This rim slippage prevention layer 50
is in contact with the bead seat of the rim 35 to which the tire is attached in use.

If the radial dimension of the tire casing is measured in a plane perpendicular to the axis of rotation and is H as shown in FIG. 1, then the bead reinforcing rubber layer 46 has a radial dimension h, which Depending on the specific dimensions and aspect ratio of the total radial length H.
It is advantageous to be between 20% and 60%. The thickness t of the bead reinforcing rubber layer 46 is between about 5% and 30% of its radial dimension h.

In the example shown, this is a standard size 8.5-
17.5, the bead reinforcing rubber layer 46 is made of rubber, or rather of a rubber mixture, in which case the stabilizing modulus at 20% elongation is greater than or equal to 1.5 MPa. Equally, its Shore A hardness is at least equal to 75°. For comparison, Apex 44 has a stabilizing modulus at 20% elongation.
It is about 0.65MPa and its shore A hardness is 65°.
Made of rubber or mixtures of a certain degree.

The modulus above was measured at exactly 20% elongation. As a practical matter, this elongation rate is very representative of the conditions under which the rubber in the apex strip 44 and bead reinforcement rubber layer 46 will be used. This modulus is called "stabilized" because each value is measured several times in succession, and it is generally accepted that the measurements stabilize after the fifth time. It is this stabilized value that is presented herein.

From the foregoing description, it is clear that the bead reinforcing rubber layer 46 made of hard rubber replaces the reinforcing ply 26 and soft rubber element 28 shown in FIG.

FIG. 3 shows another embodiment, intended for a tire casing of similar dimensions to that shown in FIG. Components in FIG. 3 that are similar to each component in the embodiment of FIG. 2 are given the same reference numerals. Therefore, the only difference between these embodiments is that in the first embodiment shown in FIG. 2, the bead reinforcing rubber layer 46 of hard rubber and the rubber covering layer 50 are formed separately. In contrast, in the specific example of Fig. 2 shown in Fig. 3,
These bead reinforcing rubber layer and rubber coating layer are integrally formed as a single layer 52,
It can be seen that this layer 52 is made of rubber having properties comparable to those of the rubber of the separate bead reinforcing rubber layer 46 of the first embodiment.

An advantage of the second embodiment shown in FIG. 3 over the first embodiment shown in FIG. 2 is that fewer components are used to assemble the tire casing. Therefore, it is possible to reduce the manufacturing costs of the casing to some extent.

In each of the embodiments described with reference to FIGS. 2 and 3, the high modulus, harder rubber apex strip 44 and bead reinforcement layer 46 or 52 provide a certain stiffness to the bead. and this stiffness varies gradually in the transverse direction, allowing the bead to fully fulfill its role as a link between the rim and the tire incorporating the casing.

Tests carried out on tire casings according to the invention show significant advantages of the invention compared to tire casings of known types.

First of all, a study of the distribution of deformation strains in a loaded tire casing shows that the deformation strains are better distributed in the casing made according to the invention. This improved distribution of deformation strain is such that fatigue life is improved.

More specifically, the fatigue life of the tire casing according to the invention was measured during a rolling test using a rolling machine, applying extremely high loads, the highest load being above the nominal load standardized by the ETRTO organization. It reaches 200%.

More specifically, the standard specification 11R22.5SC
A tire casing according to the invention of the type and a conventional casing of the same specification type were subjected to a rolling test under overload. All conventional type casings were removed in the bead area by 250 hours of rolling. Tires according to the invention withstood this test for a longer period of time, one of which showed a rolling reading of 518 hours under the same conditions.

Furthermore, these tests were carried out on tire casings according to the invention under actual specification conditions.
These tires with standard dimensions (8.5R 17.5SC)
It was installed on a car with a total load equal to 6250Kg. These casing beads remain intact after the first use until the tread is worn down, and again after the second use period they are fully restored as allowed by retreading of the crown. It was confirmed that even the wear was intact.

Therefore, previous testing has shown that the present invention provides a better fatigue life than conventional tire casings, yet allows for lower cost manufacturing of these casings, and the use of this new manufacturing is expected to increase. It is shown that.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of an example of a tire casing structure of a known type, FIG. 2 is a cross-sectional view of a portion around a bead of a tire casing structure according to one embodiment of the present invention, and FIG. FIG. 3 is a cross-sectional view similar to FIG. 2 according to a second embodiment of the invention; 10, 30 is carcass, 16 is bead, 22,
42 is bead core, 24,44 is apex, 4
0 is a winding part of the carcass ply, 46 and 52 are bead reinforcing rubber layers, 50 is a bead part rubber coating layer,
60 is the winding end of the carcass ply, t is the maximum thickness of the bead reinforcing rubber layer, H is the radial dimension of the tire casing, and h is the radial dimension of the bead reinforcing rubber layer. A indicates the outer side in the radial direction of the tire casing, B indicates the inner side in the radial direction, C indicates the outer side in the axial direction (bead portion), and D indicates the inner side in the axial direction (bead portion).

Claims (1)

[Claims] 1. At least one radially arranged ply extending from one bead core to the other bead core of the bead portion is wound around both bead cores from the inside of the bead portion to the outside of the bead portion. In the tire casing structure, an apex rubber layer 44 that tapers gradually outward in the radial direction immediately adjacent to the bead core is disposed between the carcass ply 30 and its rolled up portion 40, and immediately adjacent to said rolled up portion 40. The bead reinforcing rubber layers 46 and 52 are adjacent to the outside and are in direct contact with all of the winding sections 40 including the winding terminal section 60, and extend radially outward of the terminal section 60 and are in direct contact with a portion of the apex rubber layer 44. The bead reinforcing rubber layers 46, 52 do not contain any reinforcing filaments, and the modulus of the bead reinforcing rubber layers 46, 52 is greater than the modulus of the apex rubber layer 44; The radial dimension h measured with reference to the plane perpendicular to the tire rotation axis is 20 to 20 of the radial dimension H of the tire casing.
60%, and the maximum thickness t of the bead reinforcing rubber layers 46, 52
is 5 to 30% of the radial dimension h of the bead reinforcing rubber layers 46 and 52. 2 The rubber of the bead reinforcing rubber layers 46 and 52 is
A tire casing structure according to claim 1, characterized in that the tire casing structure has a modulus at least twice the modulus of the rubber of the apex 44. 3. The tire casing structure according to claim 1 or 2, wherein the shore A hardness of the rubber of the bead reinforcing rubber layers 46, 52 is greater than the shore A hardness of the rubber of the apex 44. . 4. A patent characterized in that the bead further includes a rim slippage prevention rubber coating layer 50, and the rim slippage prevention rubber coating layer 50 is disposed at least on the bead portion that contacts the wheel rim to which the tire is attached during use. A tire casing structure according to any one of claims 1 to 3. 5. The rim anti-slip rubber coating layer and the bead reinforcing rubber layer are integrally formed as a single component 52, which component 52 extends around at least the portion of the bead that contacts the wheel rim on which the tire is mounted in use. 5. Tire casing structure according to claim 4, characterized in that it is elongated. 6. The carcass 30 is of radial construction and comprises one or more plies, each ply comprising a plurality of parallel reinforcing cords, preferably metal cords.
The tire casing structure according to any one of Item 5.