JP6805551B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire having a half radial structure in which an aromatic oxadiazole compound code is used for the carcass cord, and more particularly to a pneumatic tire having excellent high-speed steering stability and load durability.

In a pneumatic tire, a carcass layer forming the skeleton of the tire is arranged on the tread portion, a belt layer is arranged on the outside of the carcass, and a belt reinforcing layer is arranged on the outside thereof. The carcass layer is mounted on a pair of left and right bead portions. The carcass layer is a reinforcing cord coated with coding rubber.

Various carcass layer reinforcement cords have been studied according to the characteristics required for pneumatic tires such as high-speed steering stability and load durability, and various carcass layer reinforcement cords have been used. For example, Patent Document 1 describes 66-nylon as the material of the organic fiber cord of the carcass layer. Patent Document 2 describes that a single-twisted rayon cord is used for the carcass cord.

Japanese Unexamined Patent Publication No. 2011-251583 JP-A-2015-54680

When 66-nylon is used for the reinforcing cord of the carcass layer as shown in Patent Document 1, the heat resistance of 66-nylon is not sufficient, and heat sagging occurs due to heat generation during high-speed running, and high-speed steering is stable. There is a risk of deterioration of sex.
When a single-twisted rayon cord is used for the carcass cord of the carcass layer as shown in Patent Document 2, heat sagging due to heat generation during high-speed running can be suppressed, and heat resistance is sufficient. However, when the pneumatic tire has a structure in which the carcass layer called a half radial structure has a carcass turn-up portion, under severe driving conditions where twisting is applied during high-speed driving, the above-mentioned carcass turn-up portion causes compression fatigue. As a result, the carcass cord may be destroyed, and the load durability is not sufficient.

An object of the present invention is to solve the above-mentioned problems based on the prior art and to provide a pneumatic tire having excellent high-speed steering stability and load durability.

In order to achieve the above object, the present invention is a pneumatic tire having a half radial structure, characterized by having a carcass layer in which an aromatic oxadiazole compound code is used as a carcass cord. It provides tires.

The aromatic oxadiazole compound code has a heat resistant temperature of 400 ° C., and has a rigidity E (120 ° C.) of a rigidity E (120 ° C.) at a temperature of 120 ° C. and a rigidity E (25 ° C.) at a temperature of 25 ° C. It is preferable that E (25 ° C.) is 0.7 to 0.9 and the elongation at break is 10% or more.
The carcass layer has two layers, and the aromatic oxadiazole compound code of the carcass layer preferably has a code angle of 80 ° to 88 ° with respect to the tire circumferential direction.
The carcass cord of the carcass layer preferably has an upper twist coefficient of 1800 to 2200.

According to the pneumatic tire of the present invention, high-speed steering stability and load durability are excellent.

It is sectional drawing which shows the cross-sectional shape of the 1st example of the pneumatic tire of embodiment of this invention. It is a schematic cross-sectional view which shows the carcass layer of the pneumatic tire of embodiment of this invention. It is sectional drawing which shows the cross-sectional shape of the 2nd example of the pneumatic tire of embodiment of this invention.

The pneumatic tire of the present invention will be described in detail below based on the preferred embodiments shown in the accompanying drawings.

Hereinafter, the pneumatic tire of the present invention and a method for manufacturing the same will be described in detail based on the preferred embodiments shown in the accompanying drawings.
FIG. 1 is a cross-sectional view showing a cross-sectional shape of a first example of a pneumatic tire according to an embodiment of the present invention.

The pneumatic tire (hereinafter, also simply referred to as a tire) 10 shown in FIG. 1 has a tread portion 12, a shoulder portion 14, a sidewall portion 16, and a bead portion 18 as main constituent parts, and is a half. It is called a radial structure.
In the following description, as shown by arrows in FIG. 1, the tire width direction means a direction parallel to the tire rotation axis (not shown), and the tire radial direction is orthogonal to the rotation axis. Refers to the direction. Further, the tire circumferential direction means a direction of rotation with the rotation axis as the center of rotation.
Further, the inside of the tire means the lower side of the tire in FIG. 1 in the tire radial direction, that is, the inner surface side of the tire facing the cavity region R that gives a predetermined internal pressure to the tire, and the outer side of the tire means the upper side of the tire in FIG. That is, the side opposite to the inner peripheral surface of the tire, which is visible to the user. The reference numeral CL in FIG. 1 refers to the tire equatorial plane, and the tire equatorial plane CL is a plane orthogonal to the rotation axis of the pneumatic tire 10 and passing through the center of the tire width of the pneumatic tire 10.

The tire 10 includes a carcass layer 20, a belt layer 22, a belt auxiliary reinforcing layer 24, a bead core 28, a bead filler 30, a tread rubber layer 32 forming a tread portion 12, and a side forming a sidewall portion 16. It mainly has a wall rubber layer 34, a rim cushion rubber layer 36, and an inner liner rubber layer 38 provided on the inner peripheral surface of the tire.

The tread portion 12 is provided with a land portion 12b forming a tread surface 12a on the outer side of the tire and a tread groove 12c formed on the tread surface 12a, and the land portion 12b is partitioned by the tread groove 12c. The tread groove 12c has a main groove continuously formed in the tire circumferential direction and a plurality of lug grooves (not shown) extending in the tire width direction. A tread pattern is formed on the tread surface 12a by the tread groove 12c and the land portion 12b.
The maximum width Wm of the tire 10 in the tire width direction is a distance between the maximum width positions 39a, which is a position indicating the maximum length of the tire side 39 in the tire width direction. A region within a range of ± 30 (%) of the tire cross-sectional height SH in the tire radial direction about the maximum width position 39a of the tire is called a side tread.

The bead portion 18 is provided with a pair of left and right bead cores 28 that function to fold back the carcass layer 20 and fix the tire 10 to the wheel, and a bead filler 30 that is in contact with the bead core 28. Therefore, the bead core 28 and the bead filler 30 are sandwiched between the main body portion 20a and the folded-back portion 20b of the carcass layer 20.

The carcass layer 20 extends from the portion corresponding to the tread portion 12 to the bead portion 18 through the portion corresponding to the shoulder portion 14 and the sidewall portion 16 in the tire width direction to form the skeleton of the tire 10. ..
The carcass layer 20 has a one-layer structure, and the end portion A of the folded-back portion 20b is on the tread surface 12a side of the maximum width position 39a, for example, on the shoulder portion 14. The carcass layer 20 is turned up at the bead portion 18, the carcass layer 20 is overlapped and laminated at the side portion 19, and the carcass layer 20 has a two-layer structure at the side portion 19. The carcass layer 20 has a carcass turn-up portion that is turned up by the bead portion 18.
As described above, the end A of the folded portion 20b does not necessarily have to be on the shoulder portion 14, and the end A of the folded portion 20b of the carcass layer 20 may be provided on the side portion 19.
Here, the side portion 19 of the tire 10a is a region from the bead portion 18 to the sidewall portion 16.

The carcass layer 20 is folded back from the inside of the tire to the outside of the tire by a pair of left and right bead cores 28, and forms an end portion A in the region of the sidewall portion 16. It is composed of. That is, the carcass layer 20 is mounted between one layer and a pair of left and right bead portions 18.
Further, the carcass layer 20 may be composed of one sheet material or a plurality of sheet materials. When composed of a plurality of sheet materials, the carcass layer 20 has a joint portion (splice portion).
The carcass layer 20 has a structure in which the carcass cord is coated with a cord-coated rubber, and an aromatic oxadiazole compound cord is used as the carcass cord. The carcass layer 20 will be described in detail later.

As the cord coating rubber of the carcass layer 20, one or a plurality of types of rubber selected from natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR) are preferably used. .. Further, these rubbers are terminal-modified with a functional group containing an element such as nitrogen, oxygen, fluorine, chlorine, silicon, phosphorus, or sulfur, for example, amine, amide, hydroxyl, ester, ketone, siloxy, or alkylsilyl. Those that have been terminally modified with epoxy or those that have been terminally modified with epoxy can be used.
The carbon black to be blended into these rubbers, for example, an iodine adsorption amount 20~100 (g / kg), preferably 20~50 (g / kg), DBP absorption amount is 50~135 ^(cm 3 / 100g ), preferably 50~100 ^(cm 3 / 100g), and CTAB adsorption specific surface area of 30 to 90 ^(m 2 / g), preferably those which are 30~45 ^(m 2 / g) is used.
The amount of sulfur used is, for example, 1.5 to 4.0 parts by mass, preferably 2.0 to 3.0 parts by mass with respect to 100 parts by mass of rubber.

The belt layer 22 is attached in the tire circumferential direction and is a reinforcing layer for reinforcing the carcass layer 20. The belt layer 22 is provided on the outside of the carcass layer 20 in the tire radial direction. The belt layer 22 is provided in a portion corresponding to the tread portion 12, and has an inner belt layer 22a and an outer belt layer 22b.
The inner belt layer 22a and the outer belt layer 22b include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. The inner belt layer 22a and the outer belt layer 22b are configured such that the reinforcing cord is, for example, a steel cord and is coated with the above-mentioned cord-coated rubber or the like.
The inner belt layer 22a and the outer belt layer 22b have a cord angle of the reinforcing cord with respect to the tire circumferential direction, for example, 24 to 35 °, preferably 27 to 33 °, with respect to the belt layer 22. Thereby, high-speed durability can be improved.

The inner belt layer 22a and the outer belt layer 22b of the belt layer 22 are not limited to the reinforcing cord being a steel cord, and a steel belt may be applied to only one of them, or at least one of them. May be a conventionally known reinforcing cord made of an organic fiber cord made of polyester, nylon, aromatic polyamide or the like.

On the tire 10, a belt auxiliary reinforcing layer 24 for reinforcing the belt layer 22 is provided on the outer belt layer 22b, which is the uppermost layer of the belt layer 22, that is, outside the belt layer 22 in the tire radial direction, in the tire circumferential direction. Have been placed.
As a reinforcing cord, the belt auxiliary reinforcing layer 24 is, for example, a band-shaped member in which one or a plurality of organic fiber cords are aligned and coated with the above-mentioned cord-coated rubber or the like. The belt auxiliary reinforcing layer 24 is a belt auxiliary reinforcing layer in the tire circumferential direction, which is formed by spirally winding a band-shaped member in the tire circumferential direction. The belt auxiliary reinforcing layer 24 is arranged spirally in the tire circumferential direction.

The belt auxiliary reinforcing layer 24 shown in FIG. 1, for example, includes the end portion 22e of the belt layer 22, and covers the belt layer 22 from end to end in the tire width direction, so-called full cover. The belt auxiliary reinforcing layer 24 may have a configuration in which a plurality of full covers are laminated, or may have a configuration in which an edge shoulder and a full cover are combined.
The organic fiber cord of the belt auxiliary reinforcing layer 24 includes, for example, nylon 66 (polyhexamethylene adipamide) fiber, aramid fiber, composite fiber composed of aramid fiber and nylon 66 fiber (aramid / nylon 66 hybrid cord), PEN. Fibers, POK (aliphatic polyketone) fibers, heat-resistant PET fibers, rayon fibers and the like are used.

Next, the carcass layer 20 will be described in detail. FIG. 2 is a schematic cross-sectional view showing the carcass layer of the pneumatic tire according to the embodiment of the present invention.
As shown in FIG. 2, the carcass layer 20 has a rubber layer 50 and a plurality of carcass cords 52 as reinforcing cords, and the plurality of carcass cords 52 are aligned and arranged and coated on the rubber layer 50. It is a strip-shaped member. For example, the rubber layer 50 is composed of the above-mentioned cord-coated rubber. At least one carcass code 52 is required.
The carcass code 52 is composed of an aromatic oxadiazole compound code. The composition of the aromatic oxadiazole compound code is not limited to one (single yarn), and may be a plurality of twisted yarns.

The carcass code 52 (aromatic oxadiazole compound code) preferably has an upper twist coefficient K of 1800 to 2200. When the upper twist coefficient K is 1800 to 2200, the fatigue resistance is further improved and the load durability can be improved, which is preferable.
If the upper twist coefficient K exceeds 2200, the rigidity is lowered and the steering stability is lowered. On the other hand, when the upper twist coefficient K is less than 1800, the fatigue resistance of the aromatic oxadiazole compound cord deteriorates, so that the durability of the tire decreases.
The upper twist coefficient K is represented by K = N × D ^1/2 . Here, N is the number of twists (times / 10 cm), and D is the total fineness (dtex). The unit of the upper twist coefficient K is (times (dtex) ^1/2 ) / 10 cm.

The carcass cord 52 of the carcass layer 20 preferably has a cord angle of 80 ° to 88 ° with respect to the tire circumferential direction. When the cord angle is 80 ° to 88 °, fatigue resistance can be ensured, which is preferable.

The tire 10 has a half-radial structure, and by using an aromatic oxadiazole compound cord for the carcass cord 52 of the carcass layer 20, steering stability at high speeds is ensured, and load durability is ensured. be able to.

Next, a second example of the pneumatic tire will be described.
FIG. 3 is a cross-sectional view showing a cross-sectional shape of a second example of the pneumatic tire according to the embodiment of the present invention.
In FIG. 3, the same components as the pneumatic tire 10 shown in FIG. 1 and the carcass layer 20 shown in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.
The pneumatic tire 10a of FIG. 3 (hereinafter, simply referred to as a tire 10a) has a two-layer structure of the carcass layer 40, and other configurations are the same as those of the pneumatic tire 10 shown in FIG. The tire 10a has a half radial structure like the tire 10 described above (see FIG. 1).

The tire 10a has a two-layer structure in which the carcass layer 40 is a first carcass layer 42 and a second carcass layer 44. The first carcass layer 42 is inside the tire and the second carcass layer 44 is outside the tire.
Both the first carcass layer 42 and the second carcass layer 44 have the same configuration as the carcass layer 20 shown in FIG. 1 described above. The cord angle is preferably 80 ° to 88 °. The first carcass layer 42 and the second carcass layer 44 are arranged so that the carcass cords 52 (see FIG. 2) intersect each other between layers. The orientation of the carcass code 52 (see FIG. 2) with respect to the tire circumferential direction is different between the first carcass layer 42 and the second carcass layer 44.
Similar to the carcass layer 20 shown in FIG. 1 above, the carcass layer 40 is folded back from the inside of the tire to the outside of the tire by a pair of left and right bead cores 28, and forms an end portion A in the region of the sidewall portion 16, and the bead core. It is composed of a main body portion 40a and a folded portion 40b with 28 as a boundary. That is, the carcass layer 40 having a two-layer structure is mounted between the pair of left and right bead portions 18.

The tire 10a can obtain the same effect as the tire 10 shown in FIG. Further, in the tire 10a, the carcass layer 40 having a two-layer structure is formed, and the carcass cords 52 of the first carcass layer 42 and the second carcass layer 44 are arranged so as to intersect each other between the layers to increase the rigidity of the tire 10a. It can be increased and the fatigue resistance can be further improved. Also in the tire 10a, an aromatic oxadiazole compound code is used as the carcass code 52 of the first carcass layer 42 and the second carcass layer 44.

Next, the aromatic oxadiazole compound code, which is the carcass code 52, will be described. The aromatic oxadiazole compound code also includes aromatic oxadiazole compound yarns.
The aromatic oxadiazole compound code is composed of an oxadiazole aromatic represented by the following general structural formula.

The heat resistant temperature of the aromatic oxadiazole compound code is preferably 400 ° C. When the heat resistant temperature is 400 ° C., sufficient heat resistance can be obtained, and a decrease in rigidity due to heat generation of the tire during high-speed running is suppressed, which is preferable.
The aromatic oxadiazole compound code has a rigidity ratio E (120 ° C.) / E (25 ° C.) of rigidity E (120 ° C.) at a temperature of 120 ° C. and rigidity E (25 ° C.) at a temperature of 25 ° C. It is preferably 7 to 0.9. By setting the rigidity ratio E (120 ° C.) / E (25 ° C.) to 0.7 to 0.9, steering stability during high-speed driving can be ensured.
The rigidity E (120 ° C.) at a temperature of 120 ° C. and the rigidity E (25 ° C.) at a temperature of 25 ° C. are the same measurement conditions except for the temperature, and the strength (cN / dtex) and elongation of the aromatic oxadiazole compound code are increased. It can be obtained by finding the relationship of. Based on the relationship between the strength (cN / dtex) of the aromatic oxadiazole compound code and the elongation, the maximum strength at a temperature of 25 ° C. is the rigidity E (25 ° C.), and the maximum strength at a temperature of 120 ° C. is the rigidity E. (120 ° C.).

The aromatic oxadiazole compound code preferably has a breaking elongation of 10% or more. If the elongation at break is 10% or more, fatigue resistance can be ensured. On the other hand, if the elongation at break is less than 10%, the fatigue resistance may deteriorate.
The aramid fiber has a breaking elongation of about 3%.
Regarding the elongation at break, when determining the relationship between the strength (cN / dtex) and the elongation of the aromatic oxadiazole compound code at a temperature of 20 ° C., the strength until the aromatic oxadiazole compound code breaks is determined. As a result, breaking elongation can be obtained.

The initial rigidity ratio represented by the ratio Eo / En of the rigidity Eo of the aromatic oxadiazole compound and the rigidity En of nylon in the region where the elongation is 0 to 2% is preferably 4.5 or more. By setting the initial rigidity ratio to 4.5 or more, high-speed durability can be ensured.
For the initial rigidity ratio, the relationship between strength (cN / dtex) and elongation is determined for each of the aromatic oxadiazole compound cord and nylon cord under the same measurement conditions. Using the relationship between the strength (cN / dtex) of the aromatic oxadiazole compound cord and the nylon cord and the elongation, the rigidity Eo of the aromatic oxadiazole compound and the nylon in the region where the elongation is 0 to 2% Find the rigidity En. The stiffness Eo and stiffness En correspond to the strength (cN / dtex) in the region where the elongation is 0 to 2%. The nylon cord is made of nylon 66.

The present invention is basically configured as described above. Although the pneumatic tire of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and it goes without saying that various improvements or changes may be made without departing from the gist of the present invention. Is.

Hereinafter, examples of the pneumatic tire of the present invention will be specifically described.
In this example, Examples 1 to Example 3 and Comparative Examples 1 to 3 and a reference having a half-radial structure having two layers of carcass layers in which a plurality of organic fiber cords are arranged and having a configuration shown in Table 1 below. An example pneumatic tire (hereinafter, simply referred to as a tire) was produced, and high-speed steering stability and load durability were evaluated for each tire. The evaluation results of high-speed steering stability and load durability are shown in Table 1 below.

In Examples 1 to 3, Comparative Examples 1 to 3, and the reference example, the tire size was 240 / 40R18. The arrangement of the aromatic oxadiazole compound cords in the carcass layers of Examples 1 to 3 was all the same, and the driving density was 33 lines / 50 mm. Further, the arrangement of the rayon cord of the carcass layer of Comparative Examples 1 to 3 and the arrangement of nylon 66 of the carcass layer of the reference example are the same as those of the aromatic oxadiazole compound code, and the driving density is 33 lines / 50 mm. And said.

The material of the organic fiber cord of the carcass layer is shown in the column of "Organic fiber cord material" in Table 1 below.
In the column of "organic fiber cord structure" in Table 1 below, "/ 2" indicates that two fibers are twisted.
The column of "Carcass structure" in Table 1 below shows the structure of the carcass layer, and the carcass layer has a two-layer structure. For this reason, two layers are described in the "Carcass structure" column.

High-speed steering stability was measured and evaluated as follows.
After assembling each tire of Example 1 to Example 3, Comparative Example 1 to Comparative Example 3 and Reference Example into a rim having a rim size of 18 × 8 1 / 2J at an internal pressure of 250 kPa, each test tire is used in a passenger car having a displacement of 2500 cc. Five trained drivers were installed and ran a test course to evaluate the feeling.
The results were scored by the 5-point method based on the following criteria in relative comparison with the reference example, and expressed as an average score. The numerical value in the column of "high-speed steering stability" shown in Table 1 below is based on 3.0, and the closer it is to 5.0, the better the high-speed steering stability.
Judgment criteria 5: Excellent, 4: Excellent, 3.5: Somewhat excellent, 3: Equivalent to the standard, 2.5: Somewhat inferior (practical lower limit), 2: Inferior, 1: Greatly inferior

Next, load durability and high-speed steering stability will be described.
The load durability was measured and evaluated as follows.
After assembling each tire of Example 1 to Example 3, Comparative Example 1 to Comparative Example 3 and Reference Example to a rim having a rim size of 18 × 8 1 / 2J, rear wheel drive with a displacement of 2500 cc in a deflated state I attached it to the right side of the rear wheel of the car. In this state, the test driver traveled counterclockwise at a speed of 90 km / h on an elliptical circuit course, and the test driver felt abnormal vibration due to a tire failure and measured the mileage until the vehicle stopped traveling. The load durability was evaluated by an index value with the reference example as 100.
The numerical value in the column of "load durability" shown in Table 1 below means that the larger the numerical value, the better the load durability.

As shown in Table 1 above, in Examples 1 to 3, an aromatic oxadiazole compound code was used as the carcass code, and good results were obtained in both high-speed steering stability and load durability. Was done. Of Examples 1 to 3, Example 2 had an upper twist coefficient of 2000, which was in an appropriate range, and even better results were obtained with respect to load durability. In Example 3, the top twist coefficient was 2600, and even better results were obtained with respect to load durability, but the high-speed steering stability was about the standard example.

The reference example shown in Table 1 above uses nylon 66 fiber for the carcass cord.
In Comparative Example 1, a rayon cord was used as the carcass cord, and the high-speed steering stability was good, but the load durability was poor.
In Comparative Example 2, a rayon cord is used as the carcass cord, and the rigidity ratio is higher than that of Comparative Example 1. Comparative Example 2 was good for high-speed maneuvering stability, but had poor load durability.
In Comparative Example 3, a rayon cord is used as the carcass cord, and the upper twist coefficient is larger than that of Comparative Example 1. Comparative Example 3 was good for high-speed maneuvering stability, but had poor load durability.

10, 10a Pneumatic tires (tires)
12 Tread part 14 Shoulder part 16 Side wall part 18 Bead part 20 Carcass layer 22 Belt layer 22a Inner belt layer 22b Outer belt layer 24 Belt auxiliary reinforcement layer 28 Bead core 30 Bead filler 32 Tread rubber layer 34 Side wall rubber layer 36 Rim cushion rubber Layer 38 Inner liner rubber layer 50 Rubber layer 52 Carcass cord

Claims (3)

A pneumatic tire with a half radial structure
It has a carcass layer in which an aromatic oxadiazole compound code is used as the carcass code.
The carcass cord of the carcass layer is a pneumatic tire having an upper twist coefficient of 1800 to 2200 . The aromatic oxadiazole compound code has a heat resistant temperature of 400 ° C., and has a rigidity E (120 ° C.) of a rigidity E (120 ° C.) at a temperature of 120 ° C. and a rigidity E (25 ° C.) at a temperature of 25 ° C. The pneumatic tire according to claim 1, wherein / E (25 ° C.) is 0.7 to 0.9 and the elongation at break is 10% or more. The pneumatic tire according to claim 1 or 2, wherein the carcass layer has two layers, and the aromatic oxadiazole compound code of the carcass layer has a code angle of 80 ° to 88 ° with respect to the tire circumferential direction.