JP2000025427A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the cut resistance of a buttress part without reducing productivity. SOLUTION: The pneumatic tire is provided with a carcass 6 containing a carcass ply 6A in which a folded part 6b1 folded back around a bead core 5 from the inside to the outside in the tire-axial direction is connected to a carcass body part 6a1 which extends from a tread part 3 to the bead core 5 of a bead part 4 through a sidewall part 3, and a belt layer 7 arranged outside the carcass 6 in the tire-radial direction and inside the tread part 2. The folded part 6b1 of the carcass ply 6A is provided with an auxiliary part 11 which is folded back inside in the radial direction to terminate at the outer end of a base part 10 extending from the bead core 5 to the inside in the tire-radial direction of the belt layer 7. Further, the height h1 of a terminal point P, at which the auxiliary part 11 terminates, from a bead-base line BL is determined to be 0.6 to 0.8 times the height H of tire-cross section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving cut resistance without reducing productivity.

[0002]

2. Description of the Related Art A radial tire has a carcass in which cords are arranged in a radial direction and a belt in which the carcass is arranged at a small angle with respect to the tire equator outside the carcass in the tire radial direction and inside the tread portion. With layers. When running on uneven terrain such as rocky roads or rubble roads with this radial tire, the sidewalls that are less rigid than the tread, especially buttresses in the tire radial outside area of the sidewalls, contact during running. The body of the carcass is susceptible to cuts due to crushed stones.

Conventionally, in order to prevent such a cut of the carcass at the buttress portion, a reinforcing ply in which organic fiber cords such as nylon are arranged outside the carcass of the buttress portion so that the cords cross each other. To provide a cord reinforcing layer which is superposed as a set of two cords. Further, in this cord reinforcing layer, a rubber layer for maintaining a cord interval between plies may be separately provided in order to prevent the cords from contacting each other.

As described above, providing the cord reinforcing layer separately from the carcass causes an increase in the number of tire components, so that a new supply device for supplying the reinforcing layer to the production stage separately from the carcass is newly provided. Reduce productivity efficiency, such as the need to add.

The inventor of the present invention has conducted intensive studies in view of such problems, and found that, when reinforcing the buttress portion, a folded portion which is folded outward in the tire radial direction around a bead core of a radial structure carcass is used. The folded portion is provided with a sub-portion which is turned radially inward at the outer end of the base extending from the bead core to the tire radially inward of the belt layer and terminates. It has been found that the buttress portion of the tire can be suitably reinforced without increasing the number of components.

As shown in FIG. 3, the carcass folded portion a extends from the bead core c to the inside of the belt layer b in the tire radial direction, and terminates inside the belt layer b in the tire radial direction. 61-261108, JP-A-59-81208, etc., and as shown in FIG.
From the belt layer b to the tire radial direction inner side, the belt layer b is folded back in the tire radial direction inner side and rolled again to the tire radial direction inner side of the bead core c,
Japanese Patent Application Laid-Open No. 2-18104 has been proposed.

However, the one shown in FIG. 3 is intended to improve the cornering performance, and the buttress portion e
Has almost no effect of improving cut resistance. 4 is intended to improve the cornering performance of a racing tire suitable for high-speed running. In addition, since the end of the folded portion a reaches the bead core c and is fixed, the difference from the bead core c is increased. However, there is a problem in that the production efficiency is poor, such as the need for a work to be included, the riding comfort is hardened, and the weight of the tire is significantly increased.

As described above, the present invention provides a pneumatic tire capable of improving the cut resistance of a buttress portion without increasing the number of component parts of the tire and suppressing a significant increase in tire weight. The purpose is.

[0009]

According to a first aspect of the present invention, there is provided a main body extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a portion around the bead core is directed outward from the tire axial direction. A pneumatic tire comprising a carcass including a carcass ply having a plurality of folded portions that are folded back and a belt layer disposed radially outward of the carcass and inward of a tread portion, wherein the carcass ply is folded. The part comprises a sub-part which is bent radially inward at the outer end of the base extending from the bead core to the tire layer radially inward and terminates radially inward, and a bead base line at the terminal end position of the sub-part. The height h1 from the BL is set to 0.6 to the tire sectional height H.
It is characterized by being 0.8 times.

According to a second aspect of the present invention, the carcass is composed of two or more carcass plies, and the carcass plies are connected to the tire equator C by a code of 70-9.
The cords are arranged inclined at an angle of 0 °, and the distance L between the cords of the base portion and the sub-portion is 1 to 5 mm in a region axially outside a tire radial line passing through the tread edge E. The pneumatic tire according to claim 1, wherein

According to a third aspect of the present invention, the sidewall portion forms a protector comprising an annular raised portion extending in the tire circumferential direction by raising an outer wall surface, and a plurality of protectors extending in the tire circumferential direction on the protector. The pneumatic tire for a rally according to claim 1 or 2, wherein a concave groove is formed.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the pneumatic tire according to the present embodiment includes a carcass 6 that is folded back around a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3 and locked, and the inside of the tread portion 2 and The right half cross section of a pneumatic tire for rally running on rough terrain at a high speed, with a belt layer 7 disposed radially outside the carcass 6 in the tire radial direction, is shown in this example.

The carcass 6 has at least two radially arranged carcass cords arranged at an angle of 70 ° to 90 ° with respect to the tire equator C. In this embodiment, two carcass cords are sequentially arranged from the tire lumen side. 6A and 6B. In the present embodiment, polyester is used for the carcass cord, but other fiber cords such as nylon, rayon, and aromatic polyamide, and further, steel cords and the like can be used as needed.

The carcass plies 6A, 6B are
In this example, folded portions 6b1 and 6b2 which are turned around the bead core 5 from the tread portion 2 to the bead core 5 of the bead portion 4 via the side wall portion 3 to the bead core 5 from inside to outside of the tire axial direction. Are connected.

The belt layer 7 is composed of at least two belt plies 7A in which cords are arranged at a small angle to the tire equator, for example, at an angle of 10 to 40 °, in this example, two inner and outer belt plies 7A, 7B is formed by overlapping the cords in directions that cross each other. The belt ply 7A in the radial direction is formed wider than the outer belt ply 7B. Further, in this example, a band layer 16 in which nylon cords are arranged parallel to the tire circumferential direction is provided outside the belt layer 7 in the tire radial direction.

In the present embodiment, a steel cord is used as the belt cord, but other than this, an aromatic polyamide, rayon, or another organic fiber cord having high elasticity may be used as necessary.

The width BW of the belt layer 7 in the tire axial direction is
Can be appropriately selected, for example, at about 0.85 to 1.1 times the tread width TW. Here, the tread width TW is the axial distance between the tread edges E. The tread edge E is formed between the outer surface of the tread portion 2 and the sidewall portion 3.
When the outer surface of the tire intersects with an edge as in this example, the edge is used as the edge. It is the position of the outer edge of the ground when filled and given a normal load to ground.

The "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA and a "Design Rim" for TRA , ETRTO, "Measuring Rim". Also, "normal internal pressure"
In the standard system including the standard on which the tire is based, each standard is the air pressure determined for each tire.
If it is the highest air pressure, if TRA, the table "TIRE LOAD LI
The maximum value described in "MITS AT VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" in the case of ETRTO. Load capacity, maximum value of TRA in the above table, or ETRTO
"LOAD CAPACITY" specified in.

In the present embodiment, of the two carcass plies 6A and 6B, the folded portion 6b of one carcass ply 6A whose main body is disposed on the inner side of the tire cavity.
1 includes a sub-portion 11 which is bent radially inward at the outer end of the base portion 10 extending from the bead core 5 to the tire layer radially inner side of the belt layer 7 and terminates at the outer end, and the terminating end of the sub-portion 11 The height h1 of the position P from the bead base line BL is defined as the tire sectional height H of 0.6 to 0.1.
It is characterized by eight times.

As described above, using the folded portion 6b of the carcass ply 6A, the folded portion 6b is extended from the bead core 5 to the inside of the belt layer 7 in the tire radial direction.
0 is provided at the outer end of the carcass ply 6A so as to be folded inward in the radial direction and terminated at a predetermined position. A reinforcing layer that reinforces the main body can be configured, and a structure that is extremely excellent in productivity can be provided.

The height h1 of the end position P of the sub-portion 11 from the bead base line BL is set to 0.6 to 0.8 times the tire cross-section height H, so that the length of the sub-portion 11 is reduced. The cut resistance of the carcass body portion of the buttress portion B can be increased without being restricted to dimensions effective for buttress reinforcement and without significantly increasing the tire weight or hardening the ride comfort of the tire.

The height h1 of the end position P of the sub-portion 11 is
When the tire section height H is less than 0.6 times, the sub-portion 11 extends toward the bead core side, so that the tendency of increasing the tire weight and the tendency of deteriorating the riding comfort become remarkable, so that it cannot be adopted.
Conversely, if the height h1 of the end position P of the sub-portion 11 exceeds 0.8 times the tire cross-section height H, the buttress portion B cannot be effectively reinforced, and the cut resistance aimed at by the present invention is reduced. Can't improve.

The folded portion 6 of the carcass ply 6B
b2 has a base 10 and a sub-portion 11 similar to the carcass ply 6A.
However, in this example, preferably, in the present example, the bead core 5 is turned around to extend radially outward, and the height h2 from the bead base line BL is set to be higher than the end position P of the sub part 11. The belt ends at a position outside the tire radial direction and not inside the belt layer 7 in the tire radial direction. For example, this height h2 is the tire section height H
It is desirable to make a high turn-up in the range of 0.62 to 0.8 times of the above.

In the folded portion 6b1 of the carcass ply 6A, the length S in the tire axial direction of the overlapping portion overlapping the belt layer 7 in the tire radial direction is preferably, for example, 3 to 10% of the tread width TW. , 5% in this example
And

Further, in the present embodiment, an example in which a cushion rubber 12 is provided between the base portion 10 and the sub-portion 11 of the folded portion 6b1 of the carcass ply 6A is illustrated. As a result, as shown in FIG. 2, in the folded portion 6b1 of the carcass ply 6A, in a region axially outside the tire radial line N passing through the tread edge E, as shown in FIG.
The distance L between the codes d and d of the sub part 11 is set in the range of 1 to 5 mm.

Conventionally, the cushion rubber 12 is provided at both ends in the tire axial direction of the belt layer 7 and radially inside the belt layer 7 to absorb distortion at both ends of the belt layer 7. In the example, the base portion 10 and the sub-portion 11 are provided between the base portion 10 and the sub-portion 11 existing inside the both ends of the belt layer 7 in the tire radial direction without substantially increasing the number of parts. Can be maintained. Therefore, no cushion rubber is provided at both ends of the belt layer 7.

If the distance L between the base 10 and the sub-portion 11 is less than 1 mm, the base 10 and the sub-portion 11
The cords are liable to be damaged by direct contact with each other, and ply loose occurs at the buttress portion B, which tends to reduce durability. Conversely, if the inter-cord distance L exceeds 5 mm, the sub-portion 11 tends to protrude outward in the tire axial direction, and the amount of rubber tends to increase to cover the sub-portion 11. .

In this embodiment, the cushion rubber 12 has a substantially three-month cross section whose thickness gradually decreases from the center to both sides in the tire axial direction. As a result, the distance L between the cords of the base 10 and the sub-portion 11 is gradually increased from the end of the belt layer and maintained so as to be gradually reduced again under a normal internal pressure and no load, thereby securing the flexibility of the buttress portion B. Although possible ones are shown, the present invention is not limited to this configuration.

The cushion rubber 12 is made of, for example, JI
Loss tangent (tan δ) when SA hardness is in the range of 40 to 75 °
Is 0.08 to 0.20 and the complex elastic modulus (E ^* ) is 70 to 8
It is preferable to use a rubber composition of 0 kg / cm ² . The complex elastic modulus E ^* and the loss tangent tan δ are 4 mm width × 3.
A rectangular sample of 0 mm length × 1.5 mm thickness was cut out, and a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. was used.
The values are measured under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%.

The bead core 5 is provided between the body portions 6a1 and 6a2 of the carcass 6 and the folded portions 6b1 and 6b2.
A bead apex 8 extending from the outside to the tire radial direction and made of hard rubber is disposed to reinforce the bead portion 4. This bead apex 8 has, for example, a height ha from the bead base line BL to its radially outer end,
It is set to 0.4 to 0.5 times the tire section height H.

As described above, in the present invention, the buttress portion B can be effectively reinforced by improving the carcass ply. In the present embodiment, the outer wall surface is further raised on the sidewall portion 3 so that the outer wall surface is raised in the tire circumferential direction. A protector 13 consisting of a toroidal ridge is formed, and the protector 1
3 shows an example in which a plurality of concave grooves 14 extending in the tire circumferential direction are formed.

By forming the protector 13 as described above, the side wall portion 3 can be prevented from being broken by cuts caused by hit by crushed stones or the like and cut damage caused by rubbing with curbs, and durability in running on uneven terrain. Can be further improved. Further, on the outer surface of the protector 13, a plurality of, in this example, four concave grooves 14 extending in the tire circumferential direction.
Is provided, the elasticity of the protector 13 can be improved, vertical deflection during traveling can be ensured, and even if crushed stones or the like collide with the sidewall portion 3, the impact can be effectively absorbed. The cut resistance of the tire can be improved. Note that the protector 13 may have a protruding portion formed of a harder rubber than others.

It is preferable that the position of the protector 13 is provided so as to overlap the sub-portion 11 in the tire axial direction.

The groove 14 has a groove depth of 3.0.
mm or less. If the depth of the groove 14 exceeds 3 mm, the impact resistance is improved, but the rubber thickness of the groove bottom of the groove 14 becomes thin, and cracks are easily generated at the groove bottom.

In this embodiment, the end position P of the sub-portion 11 is different from the groove 14 of the protector 13 in the radial direction of the tire. in this way,
By changing the radial position of the end position P of the sub-portion 11 where the stress tends to concentrate and the groove bottom position of the concave groove 14, the sub-portion 1
Large stress concentration at the end position P of 1 can be prevented, and the cut resistance can be improved, and a defect such as ply separation can be effectively suppressed.

As described above, in the present embodiment, the structure of the protector 13 of the sidewall portion 3 is combined with the structure of the base portion 10 and the sub-portion 11 of the folded portion 6b of the carcass ply 6A, thereby further improving the durability. It is possible to enhance the cut property and prevent the sidewall portion from being damaged, and also suppress an increase in weight and a decrease in ride comfort.

Although the present invention has been described using a pneumatic rally tire, the present invention can be suitably used other than this kind of tire.

[0038]

EXAMPLES A pneumatic rally tire having a tire size of 205 / 65R15 and shown in Table 1 was prototyped (Examples 1 to 4 and Comparative Examples 1 to 3) while traveling on a rally course on a rocky road. 10mm length at buttress B
The frequency of occurrence of the above cut flaws was examined, and Comparative Example 1 was evaluated as 10
The index was evaluated. The smaller the value of the tire weight, the better. Table 1 shows the test results.

[0039]

[Table 1]

As a result of the test, it was confirmed that all of the tires of the examples had improved cut resistance at the buttress portion. In addition, in the structural tire shown in FIG. 3 (Comparative Example 2), the reinforcing effect of the buttress portion is not sufficient, so that the cut resistance is not improved. Conversely, the tire having the structure shown in FIG. 4 (Comparative Example 3) In (2)), the cut resistance was good, but a large increase in tire weight and a decrease in productivity were observed, and it was confirmed that the ride quality was very hard.

[0041]

As described above, according to the first aspect of the present invention, the folded portion of the carcass ply is used and the folded portion is formed at the outer end of the base extending from the bead core to the inside of the belt layer in the tire radial direction. The reinforcing layer of the buttress portion can be formed by the carcass ply by providing the sub-portion which is folded inward in the direction and ends at a predetermined position. Further, since the number of components of the tire is not increased, the cut resistance of the buttress portion can be improved without lowering the productivity.

The height h1 of the end position of the sub-part from the bead d base line BL is set to 0.6 of the tire sectional height H.
By limiting the range to about 0.8 times, the cut resistance of the buttress portion can be increased without significantly increasing the tire weight and hardening the riding comfort of the tire.

According to the second aspect of the present invention, the distance L between the cords of the base and the sub-portion is limited to the range of 1 to 5 mm, so that damage due to contact between the cords of the base and the sub-portion can be prevented, and the buttress portion can be prevented. In addition, it is possible to suppress ply loose at the same time and to prevent an increase in tire weight due to an increase in the amount of rubber.

According to the third aspect of the present invention, since the protector is formed on the side wall portion, the cut caused by the crushed stones hitting the side wall portion and the destruction from the cut due to the rubbing with the curb are more reliably achieved. It is possible to improve the durability in running on uneven terrain. In addition, since the outer surface of this protector is provided with a plurality of grooves extending in the tire circumferential direction, the elasticity of the protector can be improved, the deflection during running can be secured and the ride comfort can be prevented, and the sidewall portion is Even when crushed stones collide, the impact can be effectively absorbed, and the cut resistance of the tire can be further improved in combination with the configuration of the base and the sub-portion.

[Brief description of the drawings]

FIG. 1 is a right half sectional view of a pneumatic tire showing one embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA.

FIG. 3 is a right half sectional view of a tire showing a conventional technique.

FIG. 4 is a right half sectional view of a tire showing a conventional technique.

FIG. 5 is a right half sectional view of a tire showing a conventional technique.

[Explanation of symbols]

 Reference Signs List 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layer 10 base of folded part 11 sub part of folded part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 13/02 B60C 13/02

Claims (3)

[Claims] 1. A carcass including a carcass ply having a body portion extending from a tread portion to a bead core of a bead portion via a sidewall portion and having a turn-back portion connected around the bead core from the inside to the outside in the tire axial direction. A pneumatic tire comprising a belt layer disposed radially outside of the carcass in the tire radial direction and inward of the tread portion, wherein the folded portion of the carcass ply extends from the bead core to the tire radial inside of the belt layer. And a bead base line B at the outermost end of the base portion, which is bent radially inward and terminates at the outer end of the base portion.
The height h1 from L is 0.6 to 0.8 of the tire section height H.
A pneumatic tire characterized by a factor of two. 2. The carcass is composed of two or more carcass plies, and the carcass plies are arranged with cords inclined at an angle of 70 to 90 ° with respect to the tire equator C. The distance L between the cords is 1 in a region axially outside the tire radial line passing through the tread edge E.
The pneumatic tire according to claim 1, wherein the diameter is set to 5 mm. 3. The side wall portion has a protector comprising an annular raised portion extending in the circumferential direction of the tire by raising an outer wall surface, and a plurality of grooves extending in the circumferential direction of the tire are formed in the protector. The pneumatic tire for a rally according to claim 1 or 2, wherein: