JPH0617082B2 - Radial tires for heavy loads - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heavy load radial tire having improved durability of a bead portion.

[Conventional technology]

Conventionally, as tires for heavy vehicles such as trucks and buses,
Heavy load radial tires that are specified in JIS D4202 as tires for trucks and buses together with rims are often used for reasons such as lower case rigidity and better riding comfort than bias tires. Since the deformation is large with respect to the lateral force, there is a risk of structural damage at the bead portion, and bead damage is likely to occur within a short period of time under severe operating conditions.

In order to solve the problem peculiar to the heavy load radial tire, various studies have been made on the reinforcing structure of the bead portion, but in recent years, the heavy load radial tire may be used under higher load and higher internal pressure. Moreover, since the radius of action of vehicles has been expanded with the development of the highway network, the condition of long-distance high-speed driving is added, and it is required to endure even more severe conditions.

On the other hand, it is important for heavy-duty radial tires to endure two to three times of reuse, and the proportion of recycled tires used tends to gradually increase for the purpose of reducing vehicle operating costs. Since the durability of such a recycled tire depends on the reinforcement performance of the bead portion of the base tire, improvement of the durability of the bead portion is desired.

By the way, in a radial tire, since the carcass ply is provided with a cord arranged radially, that is, a carcass cord, the sidewall is flexible, and the bending in the tire axial direction, that is, the lateral direction is large, and the tire is deformed by rolling. The amount is much larger than the bias tire.

When such a radial tire is filled with a high internal pressure, the carcass cord of the carcass ply main body portion 2b is pulled outward in the tire radial direction, as shown in FIG. A slippery tendency is generated which causes the so-called "ply blow-through" by being pulled inward in the direction.

Further, the reinforcing layer 5 made of a metal cord arranged adjacent to the folded-back portion 2a is also dragged by the movement of the carcass cord and fluctuates, and shear strain is generated in each portion.

Next, even during load rolling during running of the tire, the tire is most flexed in the lateral direction in the contact area, and the sidewall portion is deformed into a convex shape protruding outward in the tire axial direction and overhangs on the rim flange portion. Such bending deformation is performed. It can be easily understood that the flexural deformation causes a compressive deformation in a portion along the folded-back portion of the carcass ply and an extensional deformation in a portion along the main body portion. As a result, an interlaminar shear strain is generated between the main body portion and the folded portion, and the stress concentration at the cord end is promoted.

Due to further bending deformation, the carcass cord of the main body,
The code path (spacing between adjacent codes) is forcibly widened. Further, this widening facilitates the flexural deformation, and in conjunction with this, the folded portion and the reinforcing layer of the carcass ply are easily pushed outward in the tire axial direction, and the cord path is subjected to a widening force. These series of movements increase the stress concentration due to the step of each cord end of the carcass and the reinforcing layer, and the metal cord end has cracks and separations, which grows to bead damage and further causes “ply blowout”. To be done.

[Problems to be Solved by the Invention]

In the present invention based on such findings, by suppressing the expansion of the cord path of the carcass cord of the carcass ply that promotes such a phenomenon, and reducing the stress concentration and strain at the cord end, the beads in the heavy load radial tire are reduced. It is intended to improve the durability of the part.

In order to solve such a problem, there has been attempted a method of suppressing stress concentration by disposing an organic fiber layer on the outer end of the folded portion or coating with a high hardness rubber layer, but it is still not the only method. Not a sufficient solution.

An object of the present invention is to provide a heavy duty radial tire that can improve the durability of the bead portion.

[Means for Solving the Problems]

The present invention is, in a heavy-duty radial tire, between the bead apex and the carcass turn-up part, the radius of the lower part of the turn-up part and the outer part of the reinforcing layer, which is the smaller radial height. Disposing a fiber reinforcing layer made of an organic fiber cord that extends outward in the radial direction from the inner side in the direction to the outer side in the radial direction, and the reinforcing layer is a tire. A first protective layer portion that covers the inner portion of the inner portion wound axially inward from the inner side in the radial direction to the outer side in the radial direction, and the outer end portion of the high portion. And a second protective layer portion that continuously covers the protruding portion of the fiber reinforcing layer from the upper portion on the outer side in the tire axial direction and swells beyond the protruding portion, the fiber reinforcing layer and the bead apex. The fiber reinforced layer between And a protective layer made of rubber containing short fibers, each of which is composed of a stiffener made of hard rubber, and a buffer made of this stiffener low-elasticity rubber. And the height of the buffer is 20 to 60% of the tire cross-sectional height and extends beyond the fiber reinforcing layer in the radial direction.

(Operation) The height of the fiber reinforcement layer, which is larger in the radial direction inward of the lower portion, which is the smaller radial height between the folded portion of the carcass and the outer portion of the reinforcing layer. This fiber reinforcement layer reinforces the bead portion and the side wall portion, and extends beyond the outer end of the folded portion because it consists of an organic fiber cord that extends outward in the radial direction and intersects the cord of each ply. By being extended, the strain is shared at the folded portion of the carcass ply and the outer end of the reinforcing layer, and delamination is prevented at this portion.

Further, the first protective layer portion that covers the outer end portion of the inner portion of the reinforcing layer that is wound inward in the tire axial direction on the inner side in the tire axial direction is
In addition to relaxing the strain at the outer edge of this inner part and preventing stress concentration, it effectively suppresses the widening of the cord path of the carcass ply body part to reduce tire deformation and, as a result, the bead rigidity. Increase.

A second protective layer continuously covering the outer end portion of the higher portion of the folded portion of the carcass and the outer portion of the reinforcing layer and the protruding portion of the fiber reinforcing layer on the outer side in the tire axial direction. The portion enhances the rigidity of the bead portion and the sidewall portion, relaxes interlayer strain at the cord end, and reduces stress concentration.

The third protective layer portion provided between the bead apex on the inner side in the tire axial direction of the high portion increases rigidity of the bead portion and the side wall portion together with the second protective layer, and reduces flexural deformation. , Protects the outer edge parts of the reinforcing layer and the fiber reinforcing layer as a unit, disperses and alleviates the stress concentration that tends to occur in these parts, and in the vicinity of the sidewall part that is peculiar to radial tires and is flexible in the axial direction of the tire. By extending each terminal, it is possible to prevent a step in rigidity and reduce the occurrence of cracks in the terminal.

In addition, the bead apex is made of high elastic rubber and has a stiffener along the body of the carcass, so that the bead portion can be strengthened together with the reinforcement layer and the fiber reinforcement layer to reduce flexural deformation, and the strain generated at each cord end can be reduced. The buffer, which is made of low-elasticity rubber, reduces the shear strain that acts on the bead apex when the sidewall part flexes during load rolling of the tire and the stretching force repeatedly acts on the bead part. , The stress concentration at the folded end of the carcass ply and the cord end of the reinforcing layer is effectively dispersed together with the protective layer made of rubber with end fibers,
Reduces rubber peeling. Furthermore, by using low elasticity rubber, the resistance to compressive stress and bending stress is reduced,
It also contributes to the suppression of heat generation in the bead portion, which can improve the durability of the bead portion.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

The carcass has a folded-back portion 2 which is folded back from the inner side in the tire axial direction to the outer side at the bead core 3 to the main body portion 2b extending from the tread portion to the bead core 3 to reach the bead core 3.
The carcass ply 2 is formed by integrally connecting a.
Further, a belt layer using a steel cord (not shown) is arranged radially inward of the tread portion and outside the carcass.

The carcass ply 2 has steel cords radially arranged.

Further, as shown in FIG. 1, the radial outer end 2a1 of the folded-back portion 2a is located radially inward of the maximum width position of the tire, whereby, when the tire rolls,
Avoid areas with a large amount of deformation, reduce strain, and avoid stress concentration.

On the outside of the folded portion 2a of the carcass ply in the axial direction of the tire, a reinforcement made of a steel cord or an aromatic polyamide cord is wound inward in the radial direction of the bead core 3 along the main body portion 2b of the carcass. Layer 5 is arranged.

The reinforcing layer 5 is provided on the outer portion 5a extending along the folded portion 2a of the carcass ply on the outer side in the tire axial direction,
An inner portion 5b is provided, which wraps the inner side of the bead core in the radial direction along the carcass ply from the outer side in the tire axial direction to the inner side and terminates.

Further, the portion 5a of the reinforcing layer 5 on the outer side in the axial direction of the tire has a height of the outer end 5a1 in the radial direction, which is the same as the height of the outer end 2a1 of the carcass ply, from the bead base portion to the tire maximum width position. It is smaller than the height of the direction.

Further, when the height of the outer end 2a1 of the folded-back portion 2a of the carcass ply becomes large, the height of the outer portion 5a is made small, or the height is made different, thereby making the terminal 2a different.
The positions of 1, 5a1 are displaced in the height direction, thereby preventing concentration of rigidity steps due to overlapping of terminals.

In the present specification, the folded-back portion 2a and the outer portion 5
Among a, the smaller height, in the case of FIG. 1, the folded portion 2a is named as the lower part S, and the larger height, in this example, the outer part 5a of the reinforcing layer 5 is named as the higher part. To do.

The outer end 5b1 of the inner portion 5b is preferably higher than the height of the folded-back portion 2a as shown in the figure, whereby the bead portion is reinforced.

Also, by inclining the cord of the reinforcing layer 5 at an angle of 20 ° to 70 ° with respect to the cord arrangement direction of the carcass,
The carcass ply 2 can be reinforced to prevent widening of the cord path of the carcass cord and to reduce interlayer shear strain in the cord terminal.

Further, a bead apex 6 extending outward in the radial direction is provided between the main body portion 2b of the carcass ply 2 and the folded-back portion 2a with the upper portion of the bead core 3 as the bottom side, and the bead apex 6 and the carcass Folding part 2
a and the outer portion 5a of the reinforcing layer 5 between the folded portion 2
a, the fiber reinforcing layer 7 along the inner side of the reinforcing layer 5 in the tire axial direction
Is operated.

The fiber reinforcing layer 7 is formed between the bead apex 6 and the folded portion 2a, that is, the lower portion S which is the folded portion 2a in this example.
Has a protruding portion extending radially inward from the outer end of the outer end of the high portion M, which is the outer portion 5a in the present example, to the outer side in the radial direction, and this high portion M Extending radially outward along.

The height of the fiber reinforcing layer 7 is as described above,
It is higher than the height h of the outer end 6b1 of the bead apex 6 and is approximately midway between the outer end of the high portion M and the outer end 6b1 of the bead apex 6 as shown in FIG. It should be high.

As a result, the fiber reinforcing layer 7 reinforces the tire from the bead portion to the sidewall portion and improves the bending rigidity.

The fiber reinforcing layer 7 is arranged at an angle of 20 ° to 70 ° with respect to the cord arranging direction of the carcass ply, is inclined in the direction opposite to the cord of the reinforcing layer 5, and the folded portion 2a of the carcass is formed. It is sandwiched between the reinforcing layer 5 and the fiber reinforcing layer 7. Therefore, the cords of the reinforcing layer 5 and the fiber reinforcing layer 7 cross each other at an angle of 20 to 70 and closely adhere to the cords of the folded portion 4a arranged substantially in parallel with the tire radial direction, so that the folded portion 2a. The interlaminar shear strain is reduced by bearing and relaxing the force in the pulling direction due to the slip effect that acts on.

The cord of the fiber reinforcing layer 7 is an organic fiber cord of nylon, polyester or the like having a low elastic modulus. Note that the fiber reinforcing layer 7 can be inserted between the folded portion 4a of the carcass 4 and the reinforcing layer 5 if necessary, such as when the height of the folded portion is large.

The bead apex 6 includes a stiffener 6A made of highly elastic rubber that extends from the upper side of the bead core 3 toward the side wall portion along the tire axial direction outer side of the carcass body 2b, and the tire shaft of the stiffener 6A. It is formed as a two-layer body with a buffer 6B which is adjacent to the outer side in the direction and extends outward in the radial direction with a sidewall portion and which is made of low-elasticity rubber.

High elastic rubber has, for example, a complex elastic modulus E of 250 kgf / cm ²
As described above, the JIS hardness is in the range of 75 ° to 95 °, and the outer end 6a1 of the stiffener 6A is at least the high part M.
Extends above the outer edge of the.

The low elastic rubber has, for example, a complex elastic modulus E of 80 to
200 kgf / cm ² or more, JIS hardness in the range of 50 ° to 80 °, and lower elasticity than the high elastic rubber, and the outer end 6b1 of the buffer 6B is the outer end 6a1 of the stiffener 6A, The height h of the fiber reinforcing layer 7 beyond the outer end 7a1 is in the range of 20% to 60%, preferably 30 to 40% of the sectional height of the tire from the bead base portion to the upper surface of the tread portion. .

As described above, the bead apex 6 is made of high elastic rubber and is provided with the stiffener 6A along the carcass body 2b, whereby the bead portion can be strengthened together with the reinforcing layer 5 and the fiber reinforcing layer 7, and flexural deformation can be reduced. The distortion generated at the cord end can be reduced.

In addition, the buffer 6B made of low elastic rubber reduces the shear strain acting on the bead apex when the sidewall portion bends during the load rolling of the tire and the stretching force repeatedly acts on the bead portion. The stress concentration at the end 2a1 of the folded portion 2a of the ply and the end 5a1 of the portion 5a outside the reinforcing layer is effectively dispersed together with the protective layer 8 to reduce rubber peeling. Further, by using a rubber having low elasticity, resistance to compressive stress and bending stress can be reduced, and it can contribute to suppression of heat generation at the bead portion.

The complex elastic modulus was measured by using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., and the initial strain was 10 at a temperature of 70 ° C.
%, Frequency 10 Hz, amplitude 2%, width 4 mm x length 30 mm x 2
It is measured using a mm sample piece.

Further, in the heavy load radial tire of the present invention, the outer end portion of the inner portion 5b of the reinforcing layer 5 extending in the radial direction is extended from the inner side to the outer side in the radial direction from the outer end 5b1 to the tire axial direction. The first protective layer portion 11 that covers the inside, the radially outer end portion of the high portion M and the protruding portion of the fiber reinforcing layer 7 from the high portion M, and the outer end 5a1 of the protruding portion. 2nd over and covering continuously on the outside in the axial direction of the tire
Of the fiber reinforcing layer 7 extending in the radial direction and inside the fiber reinforcing layer 7 in the tire axial direction and in contact with the bead apex 6.
Protective layer 8 consisting of a third protective layer portion 10 covering over 1
Is provided.

The protective layer 8 is an organic fiber such as vinylon, rayon, polyester, nylon or aramid or an inorganic fiber such as glass or steel cord, which has been subjected to an adhesive treatment in a rubber component such as natural rubber, isoprene rubber, butadiene rubber or styrene butadiene rubber. However, 0.1 denier or more is 0.1
Short fiber cut to a length of ~ 30mm is made into rubber component 100
Young's modulus of 10 to 100 parts mixed and dispersed with respect to 10 parts is 10
It is formed by using rubber mixed with end fibers in the range of about ³ to 10 ⁴ kg / cm ² .

In addition, the first protective layer portion 11 includes the inner portion 5 b of the reinforcing layer 5.
A sheet having a substantially uniform thickness in the range of 0.4 to 5 mm, which covers the outer end 5b1 from inside and extends radially inward and outward along the carcass ply body 2b beyond the outer end. Formed as a body.

Therefore, in addition to relaxing the strain at the outer end 5b1 of the inner portion 5b and preventing stress concentration, the expansion of the cord path of the main body of the carcass ply is effectively suppressed together with the winding portion 5b of the reinforcing layer 5. The deformation of the bead portion is reduced, and as a result, the rigidity of the bead portion is increased. The first protective layer portion 11 is formed using a sheet-shaped member having a relatively wide width from the inside and outside heights.

The second protective layer portion 9 extends from the vicinity of the bead bottom portion to the vicinity of the outer end 6b1 of the bead apex 6,
In this example, the outer portion 5a of the reinforcing layer 5, which is the above-mentioned upper portion M,
And the outer end 7a1 of the fiber reinforcement layer 7 is covered.
The second protective layer portion 9 is a relatively thin sheet body having a wall thickness in the range of 0.4 mm to 10 mm, and the distance a from the inner end 9b1 to the inner end 7b1 of the fiber reinforcing layer 7 is ,
It is preferable to maintain the rigidity of the inside of the fiber reinforcing layer 7 and to reduce the strain in the region by making the length about 10 mm or more and extending the inside. Further, the second protective layer portion 9 enhances the rigidity of the bead portion and the sidewall portion, alleviates interlayer strain at the cord end, and reduces stress concentration.

As described above, the third protective layer portion 10 extends in the radial direction, is located inside the fiber reinforcing layer 7 in the axial direction of the tire, and is in contact with the bead apex 6 so as to cover the outer end portion of the fiber reinforcing layer 7. The end 7a1 is exceeded and the outer end substantially coincides with the outer end 6b1 of the bead apex 6. Moreover, the inner end 10
b1 is located near the outer end 5a1 of the reinforcing layer 5.

The second and third protective layer portions 9 and 10 increase the rigidity of the bead portion and the side wall portion to reduce the deflection, and integrally form the outer portion 5a of the reinforcing layer 5 and the outer ends of the fiber reinforcing layer 7. Cover and protect parts. As a result, the stress concentration that tends to occur in these parts is dispersed and alleviated, and the step of rigidity due to the extension of each terminal near the sidewall portion that is flexible in the tire axial direction peculiar to the radial tire is prevented, and The generation of cracks can be reduced.

〔The invention's effect〕

Thus, in the heavy load radial tire of the present invention, the reinforcing layer is arranged in the folded portion of the carcass, and since the fiber reinforcing layer and the protective layer are configured as described above, the stress concentration at the folded portion or the outer end portion of the reinforcing layer is reduced. It is relieved, effectively prevents peeling from the rubber, and prevents widening of the cord path in the carcass body. The bead apex is made of highly elastic rubber and has a stiffener along the body of the carcass to strengthen the bead part together with the reinforcement layer and the fiber reinforcement layer to reduce flexural deformation and reduce strain at each cord end. sell.

In addition, the buffer made of low-elasticity rubber reduces the shear strain that acts on the bead apex when the sidewall part bends during load rolling of the tire and the stretching force repeatedly acts on the bead part. The stress concentration at the ends of the ply turn-back portion and the cord of the reinforcing layer is effectively dispersed together with the protective layer to reduce rubber peeling. Further, by using a rubber having low elasticity, the resistance to compressive stress and bending stress is reduced, and the durability of the bead portion can be improved by contributing to suppression of heat generation of the bead portion.

[Brief description of drawings]

FIG. 1 is a sectional view of a bead portion showing an embodiment of the present invention,
FIG. 2 is a diagram explaining the force acting on the bead portion. 2 ... Carcass ply, 2a ... Folding part, 2b ... Main body part, 3 ... Bead core, 5 ... Reinforcing layer, 5a ... Outer part 5b ... Inner part, 6 ... Bead apex, 6A ... ... stiffener, 6B ... buffer, 7 ... fiber reinforcing layer, 8 ... protective layer, 11 ... first protective layer portion. 9: Second protective layer section. 10 ... Third protective layer section.

Claims (1)

[Claims] 1. A radial-arranged steel integrally provided with a folded-back portion which is continuous with a main body portion from a tread portion to a sidewall portion to a bead core of a bead portion and which is folded back from the inner side in the tire axial direction to the outer side and terminated at the bead core. A carcass consisting of a cord, and by wrapping the radially inner side of the bead core from the outer side in the tire axial direction of the folded-back portion to the inner side in the tire axial direction, and terminating it, the outer side in the axial direction of the tire and the inner side of the inner side being wound inward. In a heavy load radial tire having a reinforcing layer having a portion, and a bead apex made of rubber extending radially outward from a bead core between the body portion of the carcass and the folded portion of the carcass, the reinforcing layer is , A steel cord or an aromatic polyamide cord, and with the folded portion of the carcass The outer portion of the reinforcing layer is different in radial height, and between the bead apex and the folded portion of the carcass, the folded portion of the carcass and the outer portion of the reinforcing layer. The outer edge of the outer part of the lower part, which has the smaller radial height, and the outer part of the higher part, which has the greater height, extends radially outward from the inner part of the part. A fiber reinforcing layer made of an organic fiber cord having a protruding portion and intersecting with the reinforcing layer or the cord of the carcass, and the inner side of the inner portion of the inner portion where the reinforcing layer is wound inward from the inner side in the radial direction. A first protective layer part that covers the inner part of the part of the carcass beyond the outer end in the radial direction in the axial direction of the tire, and the folded part of the carcass and the outer part of the reinforcing layer. The above is the one with the larger height The outer end portion of the side portion and the protruding portion that the fiber reinforcing layer extends beyond the outer end of the higher portion to the outside in the radial direction, continuously cover the outside in the axial direction of the tire, and the outside portion in the radial direction. A second protective layer portion extending over and a third protective layer portion extending radially outwardly between the fiber reinforcing layer and the bead apex, and each short fiber The bead apex has a JIS hardness of 75 to 90 ° which is tapered outward from the bead core in the radial direction and along the tire axial direction outer side of the main body of the carcass. The stiffener extends outside the axial direction of the stiffener beyond the outer end of the stiffener and has a JIS hardness of 5
And a buffer made of rubber having a elasticity of 0 to 80 ° and a elasticity lower than that of the stiffener.
A radial tire for heavy loads, which is 0% and extends radially outward from the fiber reinforcing layer.