JP2011020644A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire which improves both durability and lightweight further than before. <P>SOLUTION: A first belt layer of a first layer of a belt and a second belt layer of a second layer are arranged in the circumferential direction in parallel and are buried in a coating rubber making a bundle in which 5-7 mono-filament cords having a filament diameter of 0.18-0.26 mm are aligned as a unit. A rubber between belts is arranged between the first belt layer at the end of the second belt layer and the second belt layer. The gauge H<SB>E</SB>of the rubber layer between the mono-filament cords of the first belt layer at the end of the second belt layer and the second belt layer is 1.3-2.5 times a gauge H<SB>C</SB>at the central portion of a tire. The gauge G of the rubber between belts is less than 1.1 mm, and the width of the first belt layer is larger than the width of the second belt layer. When a half of the difference between the width of the first belt layer and the width of the second belt layer is S (mm), the expression: S (mm)+6.7×G (mm)>12 is satisfied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire (hereinafter, also simply referred to as “tire”), and more particularly, to a pneumatic radial tire that achieves higher durability and light weight than ever before.

  In recent years, there has been an increasing demand for weight reduction of tires in order to improve the fuel efficiency of automobiles. When considering weight reduction in a belt portion using a conventional twisted steel cord, assuming that a certain level of tensile strength is ensured, the steel belt layer can only be thinned.

  From such a viewpoint, a technique for using a metal monofilament as a cord for a belt without twisting has been developed, and various proposals have been made so far. For example, in Patent Document 1, for the purpose of improving fuel consumption and riding comfort, a bundle of three or four metal wires (monofilaments) arranged side by side in the width direction of the belt without being twisted is embedded in rubber as a unit. A pneumatic radial tire having a belt formed as described above has been proposed. Further, in Patent Document 2, in order to respond to the need for weight reduction of tires and to solve problems such as a decrease in durability due to breakage of metal wires, the belt layer is made of a metal monofilament in the belt ply width direction. A pneumatic radial tire composed of three belt plies arranged under conditions and embedded in a covered rubber has been proposed.

  Further, Patent Document 3 discloses that a second radial layer tire is obtained in order to obtain a pneumatic radial tire that suppresses the occurrence of belt end separation (BES) and achieves both improvement in belt durability and reduction in tire weight. A technique is disclosed in which the gauge between the monofilament cords of the first belt layer and the second belt layer at the end of the two belt layers is 1.3 to 3.0 times the gauge at the center of the tire. Furthermore, in Patent Document 4, the diameter of the metal monofilament is 0.18 m to 0.26 mm and the number of bundles is 5 to 7, and both durability and light weight are achieved at a high level.

  As proposed so far, by applying monofilament cords to the belt, even when the gauges between the cord centers are designed together, the rubber gauge between the layers can be secured, and the interlayer gauges are designed together This makes it possible to reduce the weight of the tire, but on the other hand, it has the following problems. First, since the cord interval in the tire radial direction is close, there is a problem that cracks from adjacent cords are likely to progress. Next, since the amount of steel cord used in the belt surface is large, the interlaminar shear strain increases. As a result of such problems, BES is more likely to occur in a belt using a monofilament cord than in the case of using a normal twist cord. Although the occurrence of BES is suppressed by increasing the gauge of the coating rubber, it naturally increases the weight, which is contrary to the intended weight reduction of the tire.

  According to the technique described in Patent Document 3 above, in a tire using a monofilament cord for the belt layer, the strain at the belt end is suppressed by increasing the gauge of the belt-to-belt rubber at the belt end that is the starting point of the BES. Thus, it is possible to improve the BES resistance. Moreover, according to the technique of patent document 4, the arrangement | sequence conditions of a monofilament cord can be controlled and BES resistance can be improved. However, in order to ensure the BES resistance, the rubber gauge at the end of the belt may have to be set thick, and the requirement for weight reduction has not been sufficiently satisfied.

  In addition, a technique for controlling physical properties of a rubber composition in order to improve BES resistance has been reported. For example, Patent Document 5 adjusts the tensile strength at 50% elongation, Patent Document 6 adjusts the dynamic elastic modulus, and Patent Document 7 adjusts the tensile strength at 100% elongation and the elongation at break to predetermined ranges. Thus, a technique for improving the BES resistance is disclosed.

  Further, in order to achieve both separation and durability, the structure of the tire has been studied. For example, Patent Document 8 discloses a technique for setting the belt width to 1.00 to 1.05 or less of the tread width. Patent Document 9 discloses a technique for preventing BES by defining the relationship between the step amount and the belt width and the relationship between the thickness of the wedge rubber layer and the step amount.

JP-A-11-208210 (Claims etc.) JP 2001-334810 A (Claims etc.) JP 2005-349999 A (Claims etc.) JP 2007-302203 A (Claims etc.) Japanese Patent Laid-Open No. 5-124129 (Claims etc.) Japanese Patent Laid-Open No. 7-251605 (claims, etc.) Japanese Patent No. 2971484 (claims, etc.) Japanese Patent No. 3666912 (claims, etc.) JP-A-6-320907 (Claims etc.)

  As described above, many technologies related to tire weight reduction and BES resistance have been reported, but the demand for weight reduction of tire weight and improvement of BES resistance has further increased, and more advanced compatibility has been demanded. .

  Accordingly, the object of the present invention is to solve the above-mentioned problems in the prior art and to reduce the weight of the tire while suppressing the occurrence of BES, thereby achieving both higher durability and light weight than ever before. The object is to provide a pneumatic radial tire.

  As a result of intensive studies to solve the above problems, the inventor has improved the BES resistance by satisfying a predetermined relationship between the rubber gauge at the belt end and the widths of the first belt layer and the second belt layer. As a result, the present inventors have found that the above-mentioned problems can be solved and have completed the present invention.

That is, the pneumatic radial tire of the present invention is disposed on the outer side in the tire radial direction of a carcass composed of at least one radial carcass layer straddling a toroidal shape between a pair of left and right bead cores, and a crown region of the carcass. A pneumatic radial tire comprising: a tread portion that forms a ground contact portion; and a belt that is disposed between the tread portion and the crown region of the carcass and that forms a reinforcing portion, and includes at least two belt layers. In
The first belt layer of the first layer and the second belt layer of the second layer of the belt are each a bundle of 5-7 monofilament cords having a filament diameter of 0.18 to 0.26 mm. It is juxtaposed in the circumferential direction and embedded in the coating rubber, and an inter-belt rubber is disposed between the first belt layer and the second belt layer at the end of the second belt layer, and the end of the second belt layer gauge H _E of the rubber layer between the monofilament cord of the second belt layer and the first belt layer is a 1.3 to 2.5 times the gauge H _C in the tire center portion of, the inter-belt rubber The value of the gauge G is less than 1.1 mm, the first belt layer width is larger than the second belt layer width, and half the difference between the belt layer widths of the first belt layer and the second belt layer. Where S (mm)
S (mm) + 6.7 × G (mm)> 12
It is characterized by satisfying the relationship represented by Thereby, it is possible to provide a pneumatic radial tire in which durability and light weight are both made higher than ever before.

  In the present invention, the value of G is preferably less than 0.6 mm. Thereby, the effect of this invention can be acquired more favorably. The value of S is preferably 15 mm or less. Thereby, partial wear property can also be improved. Further, the distance in the belt width direction between the monofilament cord bundles is preferably more than 0.4 mm and less than 1.2 mm. Thereby, BES resistance can be improved more. Furthermore, the number of driven monofilament cord bundles is preferably 18 to 32 bundles / 50 mm. Thereby, favorable tensile strength can be ensured.

  According to the present invention, it is possible to provide a pneumatic radial tire in which durability and light weight are more highly balanced than ever before.

It is a half sectional view showing a pneumatic radial tire of one suitable example of the present invention. It is an expanded partial sectional view showing the edge part neighborhood of a belt layer.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a side sectional view showing a pneumatic radial tire according to a preferred embodiment of the present invention. The illustrated tire includes a tread portion 1 that is disposed in a crown region of the carcass and forms a ground contact portion, and a pair of sidewall portions 2 that extend continuously inward in the tire radial direction on both sides of the tread portion 1; A bead portion 3 is provided on the inner peripheral side of each sidewall portion 2.

  The tread portion 1, the sidewall portion 2, and the bead portion 3 are reinforced by a carcass 4 including a single carcass layer extending in a toroidal shape from one bead portion 3 to the other bead portion 3. Further, the tread portion 1 is reinforced by a belt including at least two layers arranged in the tire radial direction outside of the crown region of the carcass 4, and in the illustrated example, two layers of the first belt layer 5a and the second belt layer 5b. ing. Here, a plurality of carcass layers of the carcass 4 may be used, and an organic fiber cord extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 ° can be suitably used.

  In FIG. 2, the cross section of the width direction of the belt edge part in the tire of this invention is expanded and shown. As shown in the drawing, in the tire of the present invention, both the first belt layer 5a and the second belt layer 5b have 5 to 7 monofilament cords having a filament diameter of 0.18 to 0.26 mm (six in the illustrated example). The inter-belt rubber is arranged between the first belt layer 5a and the second belt layer 5b at the end of the second belt layer 5b. 7 is provided. By disposing the inter-belt rubber 7, distortion at the belt end, which is the starting point of the BES, is suppressed, and the BES resistance is improved.

In the present invention, the width of the first belt layer 5a is larger than the width of the second belt layer 5b, and half the difference between the belt layer widths of the first belt layer 5a and the second belt layer 5b is S (mm). When the gauge of the rubber 7 between the belts is G (mm),
S (mm) + 6.7 × G (mm)> 12,
Satisfies the relationship expressed by By satisfying the above relational expression, the BES resistance can be ensured without increasing the thickness of the gauge at the belt end, and a lighter tire can be obtained.

In the present invention, the gauge H _E of the rubber layer between the monofilament cord in the first belt layer 5a and the second belt layer 5b in the second belt layer 5b ends of the gauge H _C in the tire center portion 1.3 to 2 .5 times. Thereby, it becomes possible to make the weight reduction of the tire and the belt durability more highly compatible. If this value is less than 1.3 times, the effect of BES resistance cannot be obtained satisfactorily. On the other hand, if it exceeds 2.5 times, the weight of the tire cannot be said to be sufficient.

  In the present invention, in order to obtain better BES resistance, the gauge G of the inter-belt rubber 7 is preferably larger than 0.20 mm. Moreover, in order to fully obtain the light weight effect of a tire, it is less than 1.1 mm, Preferably, it is less than 0.6 mm.

  Furthermore, in the present invention, the half value S of the difference in belt layer width between the first belt layer 5a and the second belt layer 5b is preferably 15 mm or less. This is because if the value S, which is half the difference between the belt layer widths of the first belt layer 5a and the second belt layer 5b, is greater than 15 mm, the uneven wear property is deteriorated.

  Furthermore, in the present invention, when the distance in the tire width direction between the cords, that is, the cord interval w is as dense as 0.4 mm or less, cracks are easily connected between adjacent cords, and only the effect of the inter-belt rubber 7 is obtained. However, the BES resistance may be inferior to conventional codes. Further, even when the cord interval w is extremely sparse as 1.2 mm or more, the crack progress along the cord is fast, which may result in poor BES resistance. Therefore, in the present invention, a bundle of 5 to 7 monofilament cords 6 is applied to the belt, and while maintaining the total strength, the cord interval w is secured in an appropriate range, and good BES resistance is obtained. It is a thing. Therefore, for the reasons described above, in the present invention, the belt width direction distance w between the monofilament cord bundles is preferably more than 0.4 mm and less than 1.2 mm.

  In the present invention, considering the belt foldability, the filament diameter of the monofilament cord 6 needs to be 0.18 to 0.26 mm, preferably 0.20 to 0.24 mm. If the filament diameter is smaller than 0.18 mm, the buckling wavelength during the turn of the figure 8 is shortened, the surface distortion generated at that time is increased, and the belt folding property may be deteriorated. On the other hand, if it is larger than 0.26 mm, the surface distortion becomes large, and there is a possibility that the belt bendability may deteriorate.

Further, the tensile strength of the monofilament cord 6 is preferably 2700 N / mm ² or more. As the monofilament cord having a high tensile strength, one containing at least 0.7% by mass, particularly at least 0.8% by mass of carbon can be suitably used.

  In the present invention, the number of driven monofilament cord bundles is preferably 18 to 32 bundles / 50 mm. If the number of driving is too small, it will be difficult to ensure the tensile strength, and if it is too large, it will be difficult to ensure the cord interval, which is not preferable.

  The pneumatic radial tire of the present invention relates to the improvement of the belt structure, and other structures and materials are not particularly limited, and known structures and materials can be appropriately employed. For example, in the carcass 4, polyester fiber, nylon fiber, aramid fiber, polyketone fiber, etc., which are organic fiber cords extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 °, are preferably used. Can do.

Hereinafter, the present invention will be described more specifically with reference to examples.
(Examples 1-11, Comparative Examples 1-8)
A pneumatic radial tire having a structure including a two-layer steel belt of the type shown in FIG. 1 was manufactured under the conditions shown in Tables 1 to 3 below. The tire size was 185 / 70R14, the tread width was 130 mm, and the driving angles of the monofilament cords 6 of the first belt layer 5a and the second belt layer 5b were + 22 ° and −22 °, respectively, with respect to the tire circumferential direction.

  Moreover, as rubber compounding of the rubber 7 between belts, natural rubber 100 mass parts, carbon black (N330) 50 mass parts, cobalt salt (cobalt naphthenate) 1.0 mass part, zinc oxide 10 mass parts, vulcanization accelerator (N, N′-dicyclohexyl-2-benzothiazolylsulfenamide, NOCELLER DZ manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1.0 part by mass, sulfur 6.0 parts by mass, bismaleimide (N, N′- (4,4′-diphenylmethane bismaleimide)) A composition consisting of 2.0 parts by mass was used. The obtained tire was evaluated for BES resistance, uneven wear resistance and light weight according to the following procedure.

<Evaluation of BES resistance>
Each test tire is mounted on a regular rim specified by JATMA, filled with 220 kPa of internal pressure and mounted on a test passenger car. After running on the BES drum with lateral force with a constant side force (SF) The tire was dissected and the length of cracks occurring at the end of the belt layer was measured. The crack length of each test tire was indicated by an index with the crack length of the tire of Comparative Example 1 as 100. The smaller the index value, the better the BES resistance. Moreover, the case where the crack length of the tire was less than 50 was evaluated as ◎, the case of 100 to 50 as ◯, and the case where it exceeded 100 as ×. The results are shown in Tables 1-3.

<Uneven wear>
Each test tire was mounted on a 2000CC FF vehicle, traveled for 20000 km, and then the wear amount of the tire center portion and the wear amount of the shoulder portion were measured, and the uneven wear amount was calculated according to the following formula.
Uneven wear amount = ((shoulder portion wear amount) − (center portion wear amount)) / center portion wear amount The obtained numerical values are shown as an index with the tire of Comparative Example 1 as 100. The larger the value, the greater the uneven wear. Moreover, the case where the amount of uneven wear was 200 or less was rated as “◯”, and the case where it exceeded 200 was marked as “X”. The results are shown in Tables 1-3. The center wear amount and the shoulder wear amount were determined by the following methods.

<Center wear>
The distance between the groove bottom of the center portion and the tread surface was measured, and the difference from the distance at the time of a new article was defined as the amount of wear. The measurement was performed at six locations on the circumference, and the average value was calculated.

<Shoulder wear amount>
The distance between the groove bottom of the 10 mm portion from the tread grounding end and the tread surface was measured, and the difference from the new one was taken as the amount of wear. The measurement was performed on the inner and outer sides at the time of wearing at six locations on the circumference, and the average was obtained.

<Lightweight>
In comparison with Comparative Example 1, 0.200 kg or more was reduced by ◎, 0.16 kg or more by ○, and less than 0.16 kg by ×. The results are shown in Tables 1-3.

※１：比較例１と比較したベルトゴムおよびベルト間ゴムの減少量

* 1: Reduction amount of belt rubber and inter-belt rubber compared to Comparative Example 1.

  From Tables 1 to 3, it can be seen that the pneumatic radial tire of the present invention is highly compatible with durability and light weight. Moreover, it turns out that the partial wear property is also improving.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5a 1st belt layer 5b 2nd belt layer 6 Monofilament cord 7 Interbelt rubber 8 Coating rubber

Claims (5)

A carcass composed of at least one radial carcass layer straddling between a pair of left and right bead cores, a tread portion disposed on the outer side in the tire radial direction of the crown region of the carcass to form a ground contact portion, and the tread A pneumatic radial tire comprising: a belt composed of at least two belt layers disposed between a portion and a crown region of the carcass to form a reinforcing portion;
The first belt layer of the first layer and the second belt layer of the second layer of the belt are each a bundle of 5-7 monofilament cords having a filament diameter of 0.18 to 0.26 mm. It is juxtaposed in the circumferential direction and embedded in the coating rubber, and an inter-belt rubber is disposed between the first belt layer and the second belt layer at the end of the second belt layer, and the end of the second belt layer gauge H _E of the rubber layer between the monofilament cord of the second belt layer and the first belt layer is a 1.3 to 2.5 times the gauge H _C in the tire center portion of, the inter-belt rubber The value of the gauge G is less than 1.1 mm, the first belt layer width is larger than the second belt layer width, and half the difference between the belt layer widths of the first belt layer and the second belt layer. Where S (mm)
S (mm) + 6.7 × G (mm)> 12
A pneumatic radial tire characterized by satisfying the relationship expressed by:   The pneumatic radial tire according to claim 1, wherein the value of G is less than 0.6 mm.   The pneumatic radial tire according to claim 1 or 2, wherein the value of S is 15 mm or less.   The pneumatic radial tire according to any one of claims 1 to 3, wherein a distance in the belt width direction between the monofilament cord bundles is more than 0.4 mm and less than 1.2 mm.   The pneumatic radial tire according to any one of claims 1 to 4, wherein the number of driving of the monofilament cord bundle is 18 to 32 bundles / 50 mm.

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