JP5342366B2 - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new pneumatic tire allowing improvement of various kinds of characteristics (high speed durability, road noise and rolling resistance, etc.) of the tire without accompanying adhesion deterioration of a cord of a belt and rubber buried with the cord therein. <P>SOLUTION: This pneumatic tire is constituted of at least two layers of a first belt 7 in which a belt layer 6 is located at the outermost side of a tire radial direction and a second belt 8 arranged inside the first belt 7. The first belt 7 is made to have a close cord array reduced with an inter-layer gauge by including the steel cords 7a and bringing a group of the cords 7a located just under the groove bottom of a groove 3a close to the second belt 8. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire suitable for mounting on a general vehicle such as a passenger car, and in particular, peeling (adhesion) between a belt cord and a rubber in which the cord is embedded due to water penetration into the rubber. Degradation) is effectively avoided.

  For tires mounted on ordinary vehicles such as passenger cars, further improvements in high-speed durability, further reduction in road noise, and further reduction in rolling resistance are required.To that end, the circumferential direction of the tire is the outermost layer of the belt. It is effective to provide a spiral layer wound with a steel cord having an angle with respect to substantially 0 ° to increase the rigidity of the belt. As a prior art regarding this point, a tire disclosed in Patent Document 1 It has been known.

JP 2006-69338 A

  By the way, when steel cord is applied to the outermost belt, when water penetrates into the inside of the tire through the groove bottom formed in the tread portion of the tire, rust is generated in the steel cord due to this. However, there is a concern that the adhesion with the surrounding rubber is likely to deteriorate. In order to eliminate such problems with steel cords, it may be possible to leave the steel cord in place and thicken the tread, but in this case the tire mass will increase, and the fuel efficiency of the passenger car will increase. Also, it is not preferable from the viewpoint of reducing the rolling resistance of the tire. On the other hand, when the steel cord is moved inward with the tread and groove depths kept unchanged, the distance from other cords arranged further inside the steel cord becomes shorter. Since the area where rubber can be deformed between the two cords becomes narrow, when a load or lateral force is applied to the tire, separation between the belt where the steel cords are arranged and the belt where the other cords are arranged At present, there is no pneumatic tire that can deal with such a problem.

  An object of the present invention is to provide a novel air that can improve various characteristics (high-speed durability, road noise, rolling resistance, etc.) of a tire without accompanying deterioration of the adhesion between the cord and rubber as described above. The purpose is to provide tires.

The present invention has a tread portion having a plurality of land portions partitioned by at least one groove portion, and extends in a toroidal shape from the tread portion to the bead portion through the sidewall portion, and is disposed in the bead portion. In a pneumatic tire provided with at least one carcass ply whose end portion is wound from the inside to the outside around the bead core, and a belt layer disposed between the carcass ply and the tread portion,
The belt layer is composed of at least two layers of a first belt located on the outermost side in the radial direction of the tire and a second belt disposed on the inner side of the first belt,
The first belt includes a steel cord and has a cord group in which a group of cords located immediately below the groove bottom of the groove portion is brought close to the second belt to reduce the interlayer gauge. It is characterized by this.

  In the tire configured as described above, it is desirable that the cord of the first belt is a circumferential cord that extends substantially parallel to the equator of the tire.

  In the tire configured as described above, it is preferable that the circumferential cord is a spiral cord wound spirally.

A tire as constituted above, the first belt and the interlayer gauge between the second belt and g _2, g ₁ interlayer gauge between the first belt and the second belt in small areas of the interlayer gauge In this case, it is desirable that the relationship between g ₂ and g ₁ satisfies the condition of 0.2 <g ₂ / g ₁ <0.9.

  Since the group of steel cords of the first belt located immediately below the groove bottom of the groove portion is brought close to the second belt, and the proximity cord arrangement is made such that the interlayer gauge is reduced, The distance to the cord becomes longer, and the rust of the steel cord due to water penetration can be suppressed. Further, in the area other than the adjacent code arrangement, it is possible to sufficiently secure the arrangement interval between the two codes, so that the occurrence of separation between the belt layers can be suppressed. On the other hand, the distance between the two cords is narrow in the adjacent cord arrangement region, but the groove is not grounded to the road surface and is not directly affected by the load from the tread, so the rubber distortion between the belt layers is reduced. In this region, the occurrence of separation is suppressed.

  In general, the groove portion formed in the tread portion is a groove in the circumferential direction parallel to the equator of the tire (hereinafter referred to as a rib groove) is deeper than a groove in the width direction orthogonal to the equator of the tire (hereinafter referred to as a lug groove). The distance to the steel cord is the shortest immediately below the bottom of the rib groove. By using the cord of the first belt as the circumferential cord, it becomes easy to form the proximity cord array for the rib groove where rust is most likely to occur.

  By making the circumferential cord into a spiral cord wound spirally, the rigidity of the belt increases, and even if the number of belts constituting the belt layer is reduced, the required strength can be satisfied, and the reduced space allows It becomes easy to secure the distance from the groove bottom to the spiral cord.

By setting the relationship between the interlayer gauges g ₁ and g ₂ to be a condition of 0.2 <g ₂ / g ₁ <0.9, it is possible to suppress adhesion deterioration without impairing high-speed durability. An optimal proximity coding sequence can be formed.

It is the figure which showed the tire meridian cross section about the half part of a tire about embodiment of the pneumatic tire according to this invention. It is the enlarged view of FIG. 1, Comprising: It is the figure which showed the structure of the rib groove part periphery of a tread. It is the figure which showed the definition of the interlayer gauge. It is an enlarged view of a tire circumferential direction cross section, and is a view showing a structure around a lug groove portion of a tread. It is the figure which showed other embodiment of the pneumatic radial tire according to this invention, (a) is the figure which showed the tread pattern of the tire which formed the groove | channel connected diagonally with respect to the equator S of a tire, (b) FIG. 6 is a diagram showing an XX section in FIG. 5A, and FIG. 6C is a diagram showing a YY section in FIG. g 2 _/ g ₁ and adhesive degradation are diagrams showing the relationship between high-speed durability.

  Hereinafter, the present invention will be described more specifically with reference to the drawings.

  FIG. 1 is a diagram showing a tire meridian cross section of a tire half according to an embodiment of a pneumatic tire according to the present invention, and FIG. 2 is an enlarged view of FIG. FIG. 3 is a view showing the definition of an interlayer gauge, and FIG. 4 is an enlarged view of a tire circumferential section, showing a structure around a lug groove portion of a tread.

  In FIG. 1, 1 is a pair of bead portions connected in the circumferential direction of the tire, 2 is a pair of sidewall portions extending from the bead portions 1 toward the outer side in the radial direction of the tire, and 3 is these It is a tread portion that is connected across the extending end of the sidewall portion 2 and forms a toroidal shape.

  The tread portion 3 has at least one groove portion 3a and a land portion 3b partitioned by the groove portion 3a. The groove 3a may be a rib groove parallel to the equator S of the tire or a lug groove orthogonal to the equator S of the tire, and the tread pattern formed by the groove 3a and the land 3b can be freely changed. Is possible.

  Reference numeral 4 denotes a pair of bead cores disposed in the bead portion 1, and the bead cores 4 extend in the circumferential direction of the tire to form a ring shape.

  Reference numeral 5 denotes at least one carcass ply connected across the pair of bead cores 4. The carcass ply 5 has its end portion wound around each bead core 4 from the inside to the outside. In the carcass ply 5, a reinforcing cord is arranged. This cord may be extended at any angle with respect to the tire equator S, but in general, in order to satisfy various performances required for the tire, the direction is substantially perpendicular to the tire equator S. Is preferred. Here, the term “substantially orthogonal” specifically means that the angle of the tire with respect to the equator S is in the range of 85 ° to 95 °, and takes into account manufacturing errors. This cord can be selected in various ways, and is adopted from, for example, organic fibers such as aramid, polyethylene, and nylon, glass fibers, and steel.

  Reference numeral 6 denotes a belt layer arranged on the outer side in the radial direction of the tire with respect to the carcass ply 5. The belt layer 6 includes at least two layers of a first belt 7 located on the outermost side of the belt layer 6 and a second belt 8 disposed on the radially inner side of the tire with respect to the first belt 7. In the illustration of FIG. 1, it is displayed as being composed of three layers including a third belt 9 inside the second belt 8.

  The first belt 7 includes a steel cord 7a. Although the cord 7a may extend at any angle with respect to the equator S of the tire, the rib groove is generally the deepest groove, and water can easily penetrate from directly below the rib groove. It is preferable that the circumferential cord extends substantially parallel to the equator S of the tire. Here, “substantially parallel” specifically means that the angle is in the range of 0 ° to 5 ° with respect to the equator S of the tire, and takes into account manufacturing errors. A plurality of circumferential cords may be arranged in parallel with the equator plane S of the tire, or may be constructed as a spiral cord wound in a spiral.

  The second belt 8 is provided with a cord 8a, and the cord 8a is substantially parallel to the ground contact surface of the tread portion 3 in both the circumferential direction and the width direction, like a belt cord of a tire that is normally used. It is arranged. The cord 8a can be selected from various materials such as organic fibers such as aramid, polyethylene, and nylon, glass fibers, and steel. Although the cord 8a may extend at any angle with respect to the tire equator S, the cord of the carcass ply 5 is used in order to obtain a pantograph effect necessary to ensure flexibility in the tire radial direction. The first belt cord 7a is preferably arranged so that the angle with respect to the equator S of the tire is different.

  When the belt layer 6 is composed of three layers, the cord 8a of the second belt 8 and the cord 9a of the third belt 9 are inclined at angles symmetric with respect to the equator S of the tire. It is preferable that the cross belt is stretched.

  FIG. 3 is a diagram showing the definition of an interlayer gauge. The shortest distance from the outer shape of two cords arranged substantially in parallel is defined as an interlayer gauge.

As shown in FIG. 2, the cord 7 a of the first belt 7 has a proximity cord arrangement in which a group of cords located immediately below the groove bottom of the groove portion 3 a approaches the second belt 8. The region M in the proximity code arrangement is an interlayer gauge g ₁ (hereinafter referred to as a narrow interlayer gauge g ₁ ) with respect to the interlayer gauge g ₂ between the first belt 7 and the second belt 8. For this reason, the cord 7a has a cross-sectional shape having a concave portion immediately below the groove bottom, and the dimension b from the code 7a to the groove bottom of the groove 3a in the region M where the adjacent code array is located is more than in the case where no adjacent code array is provided. Also gets longer.

The width A ₁ of the proximity coding sequence codes 7a is also narrower than the width A ₂ of the groove bottom of the groove 3a, although in some proximity coding sequence are effective in that it can increase the size b, the width A _A width larger than 2 is more preferable because the dimension b can be extended over the entire adjacent code arrangement.

  The region M is not limited to the case where the groove portion 3a and the cord 7a extend in parallel like the rib groove and the circumferential cord shown in FIG. 2, and the groove portion 3a like the lug groove and the circumferential cord shown in FIG. Even when the cords 7a are orthogonal, the shape can be formed.

For example, as shown in FIG. 5A, the region M is a groove (zigzag groove) continuously connected while changing the direction obliquely with respect to the equator S of the tire. represented as in FIG. 5 showing the (b) Figure 5 shows a and Y-Y cross section (c), widen a ₁ proximity coding sequence and constant width, one groove bottom width a ₁ It may be included in the part. By doing in this way, it is not necessary to combine adjacent code arrangements in a complicated manner corresponding to the shape of the groove of the tread portion, and a simpler shape can be obtained.

  The region M is formed so as to correspond to the position and depth of the concave portion of the cord 7a by partially changing the thickness and hardness of the belt rubber when the cord 7a is arranged on the first belt 7. Alternatively, the belt may be formed by manufacturing a belt in which the cords 7a are arranged in a row in the same manner as a normal corded belt, and by attaching the belt to the shape having the concave portion.

  The dimension b is preferably in the range of 1.5 mm to 3 mm so that the cord 7a is not exposed from the groove 3a and the interlayer gauge in the region M is not too short.

When the narrow interlayer gauge g ₁ becomes extremely short with respect to the interlayer gauge g _2, it is due to variation in manufacturing is concerned that two codes are in contact. Also if almost narrow interlayer gauge g ₁ is the interlayer gauge g _2, the effect of suppressing the adhesion deterioration code is reduced. For this reason, the narrow interlayer gauge g ₁ satisfies the relationship of 0.2 <g ₂ / g ₁ <0.9 with respect to the interlayer gauge g ₂ , thereby suppressing adhesion deterioration without impairing high-speed durability. More preferably.

  A tire of size 225 / 45R17 having the structure shown in FIG. 1 and having the first belt and the second belt shown in Table 1 (one carcass ply is used, and the carcass ply cord is a twist of polyethylene) The first belt uses a steel spiral cord that is perpendicular to the tire equator and extends substantially parallel to the tire equator, and the second and third belts are the tire equator. Steel cords that were inclined at an angle of 30 degrees with each other and crossed each other were used, and the tire mass, rolling resistance, adhesion deterioration, and high-speed durability (ability) were investigated for each tire. The results are also shown in Table 1. Note that a in Table 1 indicates the total thickness of the tire in the tread portion as shown in FIG.

The total thickness a of the tire, the dimension b from the groove portion to the cord of the first belt, and interlayer gauges g ₁ and g ₂ between the cords were measured by cutting the tire and measuring the respective dimensions. Measurements were made at three locations in the circumferential direction of the tire, and the average value was calculated and shown in Table 1.

  As for the mass of the tire, a conventionally used tire is used as a reference tire, and the mass of each tire is shown as an index in Table 1 with the mass of the reference tire being 100. The smaller the number, the lighter.

  The tire rolling resistance test is a drum test in which each tire is assembled on a rim of 7.5 J × 17 size specified by JATMA (THE Japan Automobile Tires Associations, Inc.) and has a steel plate surface with a diameter of 1.7 m. The rolling resistance of the axle was calculated using a machine. The speed was 80 km / h, and the internal pressure was 230 kPa. The rolling resistance of the reference tire was set to 100, and the rolling resistance of each tire was displayed as an index in Table 1. Smaller numbers indicate less rolling resistance and better performance.

  The tire adhesion deterioration test was confirmed by assembling each tire on the rim, setting the internal pressure to 230 kPa, and mounting it on a 2500 cc class passenger car, running 50000 km in a hot and humid area. Four spiral cords, which are the first cords, were peeled from the rubber with a length of 30 cm from the tire after running, and the amount of rubber remaining on the cords was measured. The amount of rubber attached to each tire was shown as an index in Table 1 with the amount of rubber attached to the reference tire set to 100. Larger numbers indicate higher adhesion and better performance.

  In the tire high speed durability test, each tire was assembled on the rim, the internal pressure was set to 300 kPa, and the step speed method was confirmed according to the test method of JATMA standard. The speed at the time of failure of the reference tire was set to 100, and the high speed durability speed of each tire was displayed in Table 1 as an index.

  As a result, in the tire (comparative tire 1) in which the total tire thickness in the tread portion is larger than that of the reference tire and the distance from the groove portion to the first cord is increased, the mass and rolling resistance increase, and the tire in the tread portion increases. As the total thickness of the plate increases, the temperature tends to rise during high-speed running, and the high-speed durability is slightly reduced, so that the requirements cannot be satisfied. Further, the tire (comparative tire 2) in which the first cord is brought close to the second cord over the entire area and the distance from the groove portion to the first cord is increased (comparative tire 2) has a narrow region where the rubber can be deformed between the two cords. Therefore, the belt temperature rises during high-speed running, and the high-speed durability is greatly reduced, making it impossible to satisfy the requirements.

The tires (applicable tires 1 to 7) in which the first cord located immediately below the groove bottom is brought close to the second belt and arranged as a proximity cord have the same tire mass and rolling resistance as the reference tire, and improve adhesion deterioration. It was confirmed that it would lead to The tire (applicable tire 7) in which the first cord is too close to the second cord in the proximity code array region can significantly improve the adhesion deterioration. The two cords might come into contact with each other, and the high-speed durability decreased. The first code when the value of g _{2 /} g ₁ hardly approached the second code is close to 1, as shown in FIG. 6, the effect of suppressing the adhesion deterioration is reduced. When the ratio of the interlayer gauge g ₂ for narrowing the interlayer gauge g ₁ is to satisfy 0.2 <g 2 / g _{1 <0.9,} it is possible to suppress the adhesion deterioration without impairing the high-speed durability, it is confirmed more preferred (Applicable tires 1 to 6).

  According to the present invention, various characteristics (high-speed durability, road noise, rolling resistance, etc.) of a tire are improved without accompanying deterioration of adhesion between the cord and the rubber due to water penetration into the rubber. Can be stably supplied with a new pneumatic tire.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Bead core 5 Carcass ply 6 Belt layer 7 1st belt 7a 1st cord 8 2nd belt 8a 2nd cord 9 3rd belt 9a 3rd cord S Tire Equator

Claims (4)

A tread portion having a plurality of land portions partitioned by at least one groove portion, and a toroidal shape extending from the tread portion to the bead portion through the sidewall portion, and around the bead core disposed in the bead portion In a pneumatic tire comprising at least one carcass ply with its end rolled back from the inside and a belt layer disposed between the carcass ply and the tread portion,
The belt layer is composed of at least two layers of a first belt located on the outermost side in the radial direction of the tire and a second belt disposed on the inner side of the first belt,
The first belt includes a steel cord and has a cord group in which a group of cords located immediately below the groove bottom of the groove portion is brought close to the second belt to reduce the interlayer gauge. A pneumatic tire characterized by that.   The pneumatic tire according to claim 1, wherein the cord of the first belt is a circumferential cord extending substantially parallel to the equator of the tire.   The pneumatic tire according to claim 2, wherein the circumferential cord is a spiral cord wound spirally. Said first belt and the interlayer gauge between the second belt and g _2, the interlayer gauge between the first belt and the second belt in small areas of the interlayer gauge when the g _1, and g ₂ The pneumatic tire according to claim _{1, wherein} the relationship of g ₁ satisfies a condition of 0.2 <g ₂ / g ₁ <0.9.

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