JP3061353B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a novel bead filler for reinforcing a bead portion to improve the appearance of the bead portion while maintaining running performance such as ride comfort and steering stability, and to improve tire performance. The present invention relates to a pneumatic tire that can increase the durability of a tire.

[0002]

2. Description of the Related Art In a pneumatic tire used for heavy vehicles such as passenger cars, light trucks, buses, etc., during running, as shown in FIG. A large compressive force repeatedly acts on the outer surface side of the bead portion in the vicinity of the separation point p where the is separated from the bead portion a.

For this reason, conventionally, a plurality of plies constituting a carcass are formed, and further, a bead reinforcing layer formed by plies in which organic fiber cords are arranged is provided on the outer surface side of the bead portion a to provide a bead portion. The compression strength was increased.

[0004]

However, in recent years, as the size of the vehicle has increased, the compressive force acting on the tire has also increased, and two plies e1 as shown in FIGS. , E2 are also superposed to form a bead reinforcing layer.

[0005] By superposing the two plies e1 and e2 in this manner, it becomes possible to cross the cords of the respective plies e1 and e2, thereby exhibiting a tag effect and compressing the bead reinforcing layer. The rigidity is significantly improved.

On the other hand, when the bead reinforcing layer is formed by using a ply, as shown in FIG. 11, an overlapping portion d is formed in which both sides f of the plies e1 and e2 overlap, and the overlapping portion d is formed.
As the number of plies increases, the total thickness 2w in the overlapping portion d increases in proportion to the number of plies.

As the thickness 2w increases, the bead portion a
The unevenness of the thickness of the bead rubber j forming the outer surface of the tire increases, so-called a defect in which the outer surface is distorted by the vulcanization molding, so that the appearance quality of the tire is reduced and the durability of the bead portion is reduced. At the same time, driving performance such as steering stability and riding comfort is inferior.

As a measure for reinforcing the bead portion, for example, Japanese Patent Application Laid-Open No. 63-166607 proposes that the inner winding end of the reinforcing layer be bent to be reinforced,
As disclosed in No. 10213, proposals have been made to form a reinforcing layer using a steel cord.

The former is a measure against the tensile force on the side of the bead portion facing the bore of the tire, and the latter is aimed at improving the rim assembling performance of the tire. Improvement is a different proposal and does not solve the problem of the present application.

The inventor has conducted further studies to reduce the thickness of the bead reinforcing layer without lowering the compression resistance thereof. As a result, the inclination directions of the cords in one ply were mutually changed. The inventors have found that a thin bead reinforcing layer can be formed by simultaneously topping two inverted code strings, and have completed the present invention.

The present invention provides a pneumatic tire capable of improving the durability and improving the appearance quality of a tire by preventing the occurrence of a defect in a bead portion while maintaining running performance such as steering stability and riding comfort. It is an object.

[0012]

SUMMARY OF THE INVENTION According to the present invention, there is provided a hoist having a main body extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a hoist portion for winding the bead core outwardly in the tire axial direction. A pneumatic tire comprising a carcass including a ply, a belt layer disposed inside a tread portion and radially outside of the carcass, and a bead reinforcing layer disposed outside the winding portion in the tire axial direction at a bead portion. The bead reinforcing layer includes a first cord row using a low-elasticity organic fiber cord that is inclined in a certain direction with respect to the tire radial line and is arranged in the circumferential direction, and a reinforcing cord of the first cord row. And a second cord row using low-elasticity organic fiber cords intersecting with the reinforcing cords of the first cord row and being arranged in the circumferential direction by inclining in the opposite direction with respect to the tire radius line. A pneumatic tire characterized by being formed with a reinforcing ply together covered with a topping rubber.

Preferably, the low elasticity organic fiber cord is a nylon cord. The reinforcing cord is preferably inclined at an angle of 20 to 70 degrees with respect to the tire radial line at the tire radially inner edge of the bead reinforcing layer.

[0014]

The bead reinforcing layer uses a cord made of a low elastic organic fiber. When formed using a steel cord as in the above-described prior art, the compression rigidity of the bead portion increases, but the distortion of the bead reinforcing layer itself during molding increases, and the bead portion is easily damaged during tire running, resulting in durability. Will be inferior.

On the other hand, when a high elasticity organic fiber such as an aromatic polyamide fiber is used, the high elasticity organic fiber has a high tensile strength but a buckling performance as compared with a low elasticity organic fiber such as nylon. Will be reduced.

Therefore, the reinforcing layer provided on the outward surface side of the bead portion on which a large compressive force is repeatedly applied during running of the tire is made of a steel cord or an aromatic polyamide fiber which aims to increase the strength as described above. Also, organic fiber cords such as nylon having low elasticity characteristics are more suitable.

Further, the reinforcing cords of the first cord row and the reinforcing cords of the second cord row are inclined in directions opposite to each other with respect to the tire radial line, so that each of the reinforcing cords between the first and second cord rows is different. The reinforcement cords cross. As a result, the reinforcing cords of the first and second cord rows exhibit a hoop effect, increase the rigidity of the bead reinforcing layer while maintaining low elasticity, and repeatedly compressive force acting on the bead portion during tire running And the tire durability can be increased.

In the reinforcing ply forming the bead reinforcing layer, the first cord row and the second cord row are both covered with topping rubber, so that the reinforcing cord between the first and second cord rows is formed. Can be shortened. Therefore, the thickness of the reinforcing ply is smaller than that of a conventional reinforcing ply in which two cord plies each covered with a topping rubber as shown in FIGS.

As a result, when the tire is molded and vulcanized, the thickness of the reinforcing ply is significantly reduced even at the overlapping portion where both ends of the reinforcing ply overlap, and the bead rubber which forms the outer surface of the bead portion is exposed to the bare rubber generated at the time of vulcanization. This prevents the occurrence of defects due to the above-mentioned factors, improves the durability of the bead portion, and improves the appearance of the bead portion of the finished tire.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. 1 to 6, a pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3, 3 extending inward in the tire radial direction from both sides thereof, and a bead portion 4 extending inward of the sidewall portion 3. Have.

Further, the pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 to the bead portion 4 through the sidewall portion 3 and a belt ply disposed outside the carcass 6 and inside the tread portion 2. And a bead reinforcing layer 12 disposed on the bead portion 4.

The carcass 6 is wound around the bead core 5 on a main body 9a extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4, and the winding portion 1 is cut off at the tip.
0a and a first winding ply 6A extending outside the first winding ply 6A and a main body 9b extending along the first winding ply 6A around the bead core 5 inside the first winding ply 6A. A second winding ply 6B having a winding portion 10b wound up by the first winding ply 6B, and the first winding ply 6 extending from the tread portion 2 outside the second winding ply 6B.
A ply 6C is formed by three plies including a hanging ply 6C which reaches the vicinity of the bead core 5 through the outside of the winding portion 10a of A in the tire axial direction.

In this embodiment, a bead apex 8 made of hard rubber having a triangular cross section is provided radially outward of the bead core 5 and between the main body 9b and the winding portion 10b of the second winding ply 6b. Has started up. In addition,
The leading end of the winding portion 10a of the first winding ply 6A is located radially outward of the leading end of the bead apex 8, so that the carcass 6 in this embodiment is formed as a 2-1 HTL structure. .

The first, second, and third plies 6A, 6
B and 6C are made of organic fibers such as nylon, polyester, rayon, and aromatic polyamide. Carcass cords are arranged in a radial or semi-radial arrangement in which the carcass cords are juxtaposed at an angle of 75 to 90 ° with respect to the tire equatorial plane C, and the carcass cords are arranged in directions intersecting each other between the plies. .

In the present embodiment, the belt layer 7 is composed of two belt plies which are superposed inside and outside, and each belt ply is made of organic fiber such as nylon, polyester, rayon, aromatic polyamide or steel. The belt cords are inclined at an angle of 10 to 70 degrees with respect to the tire equatorial plane C, and are arranged in a direction intersecting with each other between the belt plies, so that the tread portion 2 has an increased rigidity.

The bead reinforcing layer 12 is formed in the bead portion 4 by a single reinforcing ply disposed outside the winding portion 9 of the carcass 6 in the tire axial direction, in this embodiment, along the outward surface of the hanging ply 6C. 13.

The lower end of the reinforcing ply 13 is located at substantially the same position as the downward surface of the bead core 5, and the upper end thereof has a height h5 from the heel end in the radial direction of 0.2 to 0.5 times the tire section height H. In the present embodiment, the reinforcing ply is positioned between the tip of the bead apex 8 and the winding end of the first winding ply 6A, and the reinforcing ply circulates in the tire circumferential direction along the outer wall surface of the bead portion 4. are doing.

The reinforcing ply 13 is made of the organic fiber cord 1
A first cord row 15 in which the fibers 4 are circling in the circumferential direction and a second cord row 16 in which the organic fiber cords 14 are circling in the circumferential direction in the same manner as the first code row 15 are provided by a topping rubber 17. It is formed by coating both and simultaneously.

The organic fiber cord 14 is formed using low-elasticity organic fibers such as nylon and polyester. When using aromatic polyamide fiber or a cord with high elasticity such as steel cord, the rigidity of the reinforcing ply becomes excessive, and there is a risk of increasing distortion when molded as a tire. Since it has a strong property against tensile strength but has poor buckling performance, a material having low elasticity is preferable for reinforcing against compressive force. In particular, nylon is most suitable among nylon cords among low elastic materials.

The organic fiber cord 14 has a fineness of 4
It is preferable to set the length from 00d / mono to 1250d / 2, and the end when arranging the first and second code strings 15 and 16 is preferably 40 to 60 per 5 cm. In arranging the organic fiber cords, the arranged organic fiber cords 14 are connected to each other with weft yarns to form a fabric.

The first and second code strings 15, 16 are:
When arranging the organic fiber cords 14 as shown in FIG.
The array is inclined at angles α and β defined in the 0 degree range.

In order to manufacture the reinforcing ply 13, for example, the following procedure is performed. As shown in FIG. 6, the first code row 15 and the second code row 16 are opposed to each other with a gap therebetween, and the code is topped in the gap between the first and second code rows 15 and 16. And an outer topping rubber material 22 along the outward faces of the first and second cord rows 15 and 16, respectively.

At the time of superposition, the first and second code rows 15 and 16 are superposed so that the inclinations of the cords 14 with respect to the transverse line Y are opposite to each other.

Each of the intermediate and outer topping rubber materials 2
Reference numerals 1, 22, 22 are formed using a sheet body having a rubber composition substantially the same as the rubber composition of the bead rubber 23 forming the outer wall surface of the bead portion 4, and are disposed in an unvulcanized state. The intermediate topping rubber material 21 has a rubber thickness t2.
0.3 to 1.0 mm, preferably 0.3 to 0.6 mm, and the outer topping rubber material 22 has a rubber thickness t1, t1 of 0.2 to 0.5 mm, preferably 0.2 to 0.3 mm. Should be set to.

The first and second cord rows 15, 16 and the middle and outer topping rubber materials 21, 22, 22 are overlapped and heated and pressurized in a vulcanizing or semi-vulcanizing operation. The members are integrated, and the first and second cord rows 15, 16 are topped by heating and deforming the topping rubber members 21, 22, 22 to form a belt-like reinforcing ply 13.

The belt-shaped reinforcing ply 1 thus formed
Numeral 3 is circulated around the outside of the carcass 6 of the bead portion 4 at the time of vulcanization molding of the tire, and is integrally formed with the bead portion at the time of tire molding by the vulcanization molding machine, and the bead reinforcing layer 12 is formed.

The reinforcing ply 13 makes the bead portion 4 make a full circumference in the circumferential direction so that the ends of the ply ends 13a and 13b on both sides are wrapped. The lap allowance E is preferably 5 to 15 mm. The end faces of the ply ends 13a and 13b are adapted to the inclination of the organic fiber cord 14 of one of the first and second cord rows 15 and 16 to prevent the peeling of the organic fiber cord 14. Can be suppressed.

The bead reinforcing layer 12 is formed by the above-described manufacturing process, so that the first and second cord rows 1 are formed.
Between 5 and 16, the organic fiber cords 14 are inclined in opposite directions to the tire radius line R, and the respective inclination angles α and β are in the range of 20 to 70.

The inclination angles α and β are less than 20 degrees or 70
Exceeding the degree, when a compressive load is applied to the bead portion 4 during running of the tire, the reaction force against the load becomes small, and improvement in bead durability cannot be achieved. Therefore, it is more preferable to set the inclination angles α and β in the range of 40 to 55 degrees.

The bead reinforcing layer 12 is formed by subjecting the intermediate and outer topping rubber members 21, 22, 22 to the first and second cord rows 1
Organic fiber cords 14, 14 in each of 5, 16
The gaps g enter the gaps, cover the entire peripheral surface of the organic fiber cord 14 over the entire circumference, and topping, and the gaps g reduce the total thickness T of the bead reinforcing layer 12 to form a thin body.

The intermediate topping rubber material 21 regulates the thickness t2 to at least 0.3 mm, and the outer topping rubber materials 22 regulate the thicknesses t1 and t1 to 0.2 mm or more. In molding, the first and second
The organic fiber cords 14 and 14 can be prevented from contacting between the cord rows 15 and 16, and the organic fiber cords can be prevented from being exposed on the outer surface of the bead reinforcing layer 12.

On the other hand, the rubber thickness t2 of the intermediate topping rubber material 21 is larger than 1.0 mm, and the rubber thicknesses t1, t1 of the outer topping rubber materials 22, 22 are larger than 0.5 mm. In this case, the total thickness T of the vulcanized bead reinforcing layer 12 becomes excessively large in the wrap portion E, and the bead portion 4
There is a risk that defects will occur on the outer wall surface.

The bead reinforcing layer 12 may be provided between the winding portion 10a of the first winding ply 6A and the hanging ply 6C, and the carcass 6 is formed by one winding ply. The present invention can be modified into various embodiments.

[0044]

[Specific Example] A tire having a tire size of 7.50 R16 and having the configuration shown in FIGS. 1 and 7 was prototyped according to the specifications shown in Table 1 (Examples 1 and 2), and its performance was tested. A test was also performed on a tire having a conventional configuration (conventional example) to compare the performance. The test method is as follows.

1) Bead durability Each test tire was mounted on a 6.00 GS × 16 rim, and was subjected to an internal pressure of 6.50 kgf / cm ² using a drum tester.
The vehicle was run at a speed of 20 km / H under a load of 878 kgf, and the running distance until damage to the bead portion was represented by an index with the conventional example being 100. The higher the value, the better.

2) Defect Generation Method 100 tires are molded and vulcanized, and the percentage of tires with visible bears is defined as the defect generation rate. The smaller the defect occurrence rate, the better.

3) Actual vehicle performance (steering stability and riding comfort) Built into the same rim as in 1) above, mounted on all wheels of a 3.5 ton flat body truck under an internal pressure of 6.5 kgf / cm ^2. The truck was run on a dry pavement road, and the sensory evaluation of the driver was carried out. The higher the value, the better. Table 1 shows the test results.

[0048]

[Table 1]

As a result of the test, in Example 1, the bead durability was increased, the defect occurrence rate was reduced, and the tire weight could be reduced, while maintaining the performance of the actual vehicle as compared with the conventional example.

In the case of Example 2, the bead durability was remarkably increased as compared with that of the conventional example and the defect occurrence rate could be reduced even though the total thickness was larger than that of the conventional example. .

[0051]

As described above, the pneumatic tire of the present invention has the following features.
By providing the bead portion with the bead reinforcing layer having the above-described configuration, the riding comfort, the steering stability is maintained, the durability of the bead portion is increased, the occurrence of defects in the bead portion is suppressed, and the appearance quality of the tire is improved. Can be enhanced.

[Brief description of the drawings]

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

FIG. 2 is a plan view showing an arrangement of organic fiber cords of the bead reinforcing layer.

FIG. 3 is a sectional view showing the reinforcing ply.

FIG. 4 is a plan view showing the overlapping portion.

FIG. 5 is a sectional view thereof.

FIG. 6 is a sectional view showing the molding.

FIG. 7 is a sectional view showing a bead portion according to another embodiment.

FIG. 8 is a sectional view showing an operation of a bead portion.

FIG. 9A is a cross-sectional view of a bead portion showing a conventional technique, and FIG. 9B is a plan view illustrating a bead reinforcing layer disposed in the bead portion.

FIG. 10 is a sectional view showing the bead reinforcing layer.

FIG. 11 is a perspective view showing a state of wrapping at an end of the bead reinforcing layer.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 9a, 9b Body part 10a, 10b Winding part 11 Belt layer 12 Bead reinforcement layer 13 Reinforcement ply 14 Organic fiber cord 15 First cord row 16 Second cord row 17 Topping rubber α, β Tilt angle of organic fiber cord R Tire radius line

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-229809 (JP, A) JP-A-47-42441 (JP, A) JP-A-61-193904 (JP, A) JP-A-61-193904 81208 (JP, A) JP-A-6-255322 (JP, A) JP-A-4-183618 (JP, A) JP-A-4-154410 (JP, A) Japanese Utility Model Publication No. 57-6606 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 15/06

Claims (3)

(57) [Claims] A carcass and a tread portion including a winding ply having a winding portion extending from a tread portion through a sidewall portion to a bead core of a bead portion and extending around a bead core toward an outer side in a tire axial direction. A pneumatic tire including a belt layer disposed inside and radially outside of the carcass and a bead reinforcing layer disposed outward in the tire axial direction of the winding portion in the bead portion, wherein the bead reinforcing layer includes: A first cord row using low-elasticity organic fiber cords inclined in a fixed direction with respect to the tire radius line and arranged in the circumferential direction, and a reinforcing cord of the first cord row are opposite to the tire radius line. By using topping rubber, the reinforcing cords of the first cord row intersect with the second cord row using low-elasticity organic fiber cords which are arranged in the circumferential direction and are crossed by tilting in the direction of A pneumatic tire formed using a reinforcing ply coated on a tire. 2. The pneumatic tire according to claim 1, wherein the low elasticity organic fiber cord is a nylon cord. 3. The pneumatic tire according to claim 1, wherein the reinforcing cord is inclined at an angle of 20 to 70 degrees with respect to the tire radial line.