JP2008018827A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire enabling improvement of both of high speed durability and driveability. <P>SOLUTION: In this tire, belts 21 and 22 have belt outside parts 25 and 26 located at the tire width direction outside and provided with belt cords 23 at a first angle θ1 with the tire peripheral direction, belt center parts 27 and 28 located at a tire width direction center adjacently to the belt outside parts 25 and 26 and provided with belt cords 23 at a second angle θ2 larger than the first angle θ1 with the tire peripheral direction, and belt inside parts 29 and 30 located at the tire width direction inside adjacently to the belt center parts 27 and 28 and provided with belt cords 23 at a third angle θ3 larger than the second angle θ2 with the tire peripheral direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire suitable for a tire having a low flatness ratio.

  Among recent pneumatic tires, so-called low flat pneumatic tires having a low flatness ratio are increasing from the viewpoint of handling stability and the like. Many of such pneumatic tires have a wide tread width, and the width of the belt layer is widened according to the widened tread width. Thereby, since tread bending rigidity becomes large, a cornering force improves and steering stability improves. In such a conventional pneumatic tire, at the time of limit cornering in high-speed traveling, both side portions in the tire width direction, which are usually outside the ground contact surface, so-called shoulder portions may be grounded. For this reason, the structure of the tire has a great influence on cornering performance and the like.

  For example, in the pneumatic tire described in Patent Document 1, the end portion of the belt cord made of organic fiber is curved, and the angle between the belt cord at the belt end portion and the equator of the tire is other than the belt end portion, that is, the center. The belt has a belt in which a belt cord disposed so as to be larger than the angle formed by the straight belt cord in the section and the equator of the tire is coated with a coating rubber. As a result, belt heat generation and rolling resistance are reduced while ensuring steering stability.

Japanese Patent Laid-Open No. 6-1515311

  However, some recent vehicles have significantly improved high-speed cruising performance. For pneumatic tires attached to such vehicles, durability at high speeds and steering stability at high speeds are important. It has become. In particular, in recent vehicles, there are many vehicles with a camber angle on the inner side of the vehicle, that is, vehicles with a camber angle of a negative camber. It has been very difficult to achieve both.

  Therefore, an object of the present invention is to provide a pneumatic tire that can improve both high-speed durability and steering stability.

  In order to achieve the above object, a pneumatic tire according to the first aspect of the present invention has a carcass layer spanned between a pair of bead cores, and a belt layer composed of a plurality of belts on the outer circumference in the tire radial direction of the carcass layer. In the pneumatic tire to be disposed, the belt is located on the outer side in the tire width direction, a belt outer portion provided with a belt cord at a first angle with respect to the tire circumferential direction, and a tire adjacent to the belt outer portion. A belt central portion, which is located in the center in the width direction and is provided with a belt cord at a second angle larger than the first angle with respect to the tire circumferential direction, and is positioned inward in the tire width direction adjacent to the belt central portion And a belt inner side portion provided with a belt cord at a third angle larger than the second angle with respect to the tire circumferential direction. That.

  In a pneumatic tire according to a second aspect of the present invention, the first angle is 22 degrees to 27 degrees, the second angle is 25 degrees to 30 degrees, and the third angle is 28 degrees to 33 degrees. It is set in the range of

  A pneumatic tire according to a third aspect of the present invention includes a tread groove formed in an asymmetric pattern with respect to the tire width direction on a tread surface disposed on a tire radial direction outer periphery of the belt layer, and the tread groove includes: The area of the groove located outside with respect to the center in the tire width direction when mounted on the vehicle is smaller than the area of the groove located inside.

  The pneumatic tire according to a fourth aspect of the present invention is configured so that the boundary between the belt outer portion and the belt center portion and the boundary between the belt inner portion and the belt center portion are obtained by incorporating the tire into a regular rim to obtain a regular internal pressure. It is located in the ground contact surface in a state where it is filled and a load of 60% of the normal load is applied.

  In the pneumatic tire according to the invention according to claim 5, the belt has a unit length of a belt center portion in which the number of belt cords per unit length of a belt shoulder portion located outside the ground contact surface is located within the ground contact surface. Fewer than the number of per-belt cords.

  The pneumatic tire according to a sixth aspect of the invention is characterized in that the belt cord of the belt shoulder portion is formed of an organic fiber material.

  The pneumatic tire according to a seventh aspect of the invention is characterized in that the belt outer portion, the belt center portion, and the belt inner portion are formed separately and are bonded together without any gap to form the belt.

  The pneumatic tire according to an eighth aspect of the invention is characterized in that the belt outer portion, the belt center portion, and the belt inner portion are integrally formed to form the belt.

  The pneumatic tire according to the invention according to claim 9 is characterized in that the flatness is less than 50%.

  According to the pneumatic tire of the invention according to claim 1, in the pneumatic tire in which the carcass layer is bridged between the pair of bead cores, and the belt layer including a plurality of belts is disposed on the outer periphery in the tire radial direction of the carcass layer. The belt is located on the outer side in the tire width direction, the belt outer side is provided with a belt cord at a first angle with respect to the tire circumferential direction, and the belt is located in the center in the tire width direction adjacent to the belt outer side. A belt central portion where the belt cord is provided at a second angle larger than the first angle with respect to the direction, and located inward in the tire width direction adjacent to the belt central portion, and second relative to the tire circumferential direction. A belt inner portion on which a belt cord is provided with a third angle larger than the angle.

  Therefore, a belt layer is formed by layering a plurality of belts in the tire radial direction, and this belt has a belt inner portion located inside the vehicle and a belt outer portion located outside the vehicle with the belt center portion interposed therebetween. In the belt central portion, the belt inner portion, and the belt outer portion, the angles of the belt cords with respect to the tire circumferential direction are different from each other: [first angle at the belt outer portion] <[second angle at the belt middle portion] < Since it becomes [the third angle at the belt inner side], the first angle of the belt outer side located on the vehicle outer side becomes relatively small, and the circumferential rigidity on the tire outer side becomes high. Will improve. On the other hand, the belt inner portion located inside the vehicle has a high ground pressure particularly when the camber angle is a negative camber. And since the rigidity of the circumferential direction inside a tire becomes low because the 3rd angle of the belt inner side part where this contact pressure becomes high becomes relatively large, high-speed durability improves. Further, by sandwiching the belt central portion between the belt inner portion and the belt outer portion, the angle difference between the first angle at the belt outer portion and the third angle at the belt inner portion is relieved at the belt central portion. Since there is no portion where the angle between the belt cord and the tire circumferential direction changes suddenly, it is possible to prevent a decrease in steering stability and high-speed durability, and therefore, high-speed durability and steering stability can be reduced. Both can be improved.

  According to the pneumatic tire of the invention according to claim 2, the first angle is 22 degrees or more and 27 degrees or less, the second angle is 25 degrees or more and 30 degrees or less, and the third angle is 28 degrees or more and 33 degrees or less. Set to range. Therefore, [1st angle at the belt outer side] <[second angle at the belt central part] <[third angle at the belt inner side], and 22 degrees ≦ first angle ≦ 27 degrees, 25 degrees ≦ second angle ≦ 30 degrees and 28 degrees ≦ third angle ≦ 33 degrees, which is preferable because both high-speed durability and steering stability can be balanced.

  According to the pneumatic tire of the invention according to claim 3, the tread surface formed on the tread surface disposed on the outer periphery in the tire radial direction of the belt layer is provided with a tread groove formed in an asymmetric pattern with respect to the tire width direction. The area of the groove located outside with respect to the center in the tire width direction when mounted on the vehicle is smaller than the area of the groove located inside. Therefore, since the area of the tread groove located on the outer side with respect to the center in the tire width direction is smaller than the area of the tread groove located on the inner side, the tire circumferential direction The steering stability can be effectively improved.

  According to the pneumatic tire of the invention according to claim 4, the boundary between the belt outer portion and the belt central portion and the boundary between the belt inner portion and the belt central portion are filled with a normal internal pressure by incorporating the tire into a normal rim. It is located within the ground plane in a state where 60% of the normal load is applied. Therefore, the boundary between the belt outer part and the belt center part and the boundary between the belt inner part and the belt center part, that is, the boundary where the angle between the belt cord and the tire circumferential direction changes is incorporated into the regular rim and the tire is It is located in the ground contact surface in a state where internal pressure is filled and a load of 60% of the normal load is applied, and this boundary part always receives a stable ground pressure, and the movement does not increase during running. Can be improved.

  According to the pneumatic tire of the invention according to claim 5, the belt has a unit length of the belt center portion in which the number of belt cords per unit length of the belt shoulder portion located outside the ground contact surface is located within the ground contact surface. Less than the number of belt cords. Therefore, the belt shoulder portion located outside the ground contact surface of each belt forming the belt layer is formed with fewer belt cords per unit length than the belt center portion located within the ground contact surface. Since both side portions in the tire width direction of each belt are softened, it is possible to prevent the belts from being separated from each other at both end portions in the tire width direction and to improve separation resistance.

  According to the pneumatic tire of the invention according to claim 6, the belt cord of the belt shoulder portion is formed of an organic fiber material. Accordingly, since the belt cord is formed of an organic fiber material at the belt shoulder portions on both sides in the tire width direction of each belt forming the belt layer, the both sides in the tire width direction of each belt are lightweight. Separation from each other at both ends in the width direction can be suppressed, and separation resistance can be improved.

  In the pneumatic tire according to the seventh aspect of the present invention, the belt outer portion, the belt center portion, and the belt inner portion are formed separately and bonded together without a gap to form a belt. Therefore, the belt is formed by forming the belt outer portion, the belt center portion, and the belt inner portion separately and bonding them together without any gaps. Therefore, the belt cord is not easily bent at the time of manufacture. Since the angle with the direction can be easily changed, the manufacturing efficiency can be improved.

  According to the pneumatic tire of the invention according to claim 8, the belt outer portion, the belt center portion, and the belt inner portion are integrally formed to form a belt. Therefore, the belt is formed by integrating the belt outer portion, the belt center portion, and the belt inner portion, so that there is no seam, thereby preventing a reduction in belt durability.

  Below, the example of the pneumatic tire concerning the present invention is described in detail based on a drawing. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a meridional cross-sectional view illustrating a main part of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a plan view illustrating a laminated structure of a belt of the pneumatic tire according to the embodiment of the present invention. 3 is a schematic view of a tread portion of a pneumatic tire according to an embodiment of the present invention. In the following description, the tire width direction means a direction parallel to the rotation axis of the pneumatic tire, the tire radial direction means a direction orthogonal to the rotation axis, and the tire circumferential direction means the rotation. The direction in which the axis rotates with the axis serving as the center of rotation.

  As shown in FIG. 1, the pneumatic tire 1 includes a tread portion 5 having a tread surface 6, left and right shoulder portions 8 continuous on both sides thereof, sidewall portions 7, and bead portions 16. . The carcass layer 11 is formed of a cord layer formed of an organic fiber covered with rubber, and forms a skeleton of the tire. The carcass layer 11 is formed from the both sides of the tread portion 5 around the equator plane 40 and the left and right shoulder portions 8 and It extends to the bead portion 16 through the sidewall portion 7. Here, the equator plane 40 is a plane orthogonal to the rotation axis and passing through the center of the width of the pneumatic tire 1. The carcass layer 11 is a strength member that serves as a pressure vessel when the pneumatic tire 1 is filled with air. The carcass layer 11 supports the load by its internal pressure and has a structure that can withstand a dynamic load during traveling. ing.

  On the inner side in the tire radial direction of the tread surface 6 that is the surface of the tread portion 5 and on the outer side in the tire radial direction of the carcass layer 11, a belt 21 and a belt 22 are arranged in order from the inside to form the belt layer 20. is doing. The belt layer 20 is a reinforcing layer attached in the circumferential direction of the tire. The belt layer 20 tightens the carcass layer 11 to increase the tread rigidity. The belt layer 20 alleviates the impact and causes trauma to the carcass layer 11. To prevent.

  As shown in FIG. 2, each belt 21 and belt 22 is formed by covering a plurality of belt cords 23 (for example, metal or organic fiber) with a base material 24 (coating rubber or the like). Further, the belt layer 20 is formed as a cross-ply belt. That is, the belt layer 20 is formed such that the belt cord 23 of the belt 21 and the belt cord 23 of the belt 22 intersect each other.

  As shown in FIG. 1, the tread surface 6 is provided with a plurality of tread grooves 6a for forming a tread pattern. The tread groove 6a includes four main grooves 6b formed continuously in the tire circumferential direction and a plurality of lug grooves 6c (see FIG. 3) extending in the tire width direction. The tread pattern of the tread groove 6a is an asymmetric pattern with respect to the tire width direction. That is, when the pneumatic tire 1 is mounted on the vehicle, it is on the outer side (or the inner side). Side) is specified. 1, 2, and 3, the right side is the side that is the outside of the vehicle. In the following description, unless otherwise specified, the side that is on the outer side with respect to the vehicle when mounted is referred to as “the tire width direction outer side”. Similarly, the side that is on the inner side with respect to the vehicle when mounted is referred to as “inner side in the tire width direction”.

  In the bead portion 16, a bead wire (not shown) as a highly rigid material is a steel wire, and a pair of bead cores 17 is formed by continuously winding the bead wire to form a ring shape. The bead core 17 supports the cord tension of the carcass layer 11 generated by the internal pressure of the pneumatic tire 1 and serves to fix the pneumatic tire 1 to a wheel rim (not shown). 11, functions as a strength member of the pneumatic tire 1 together with the belt layer 20 and the like.

  The end portion of the carcass layer 11 is folded outward from the equator surface 40 side of the pneumatic tire 1 around the bead core 17 so that the inner side in the tire radial direction of the belt layer 20 and the side wall portion 7. Are continuously provided on the equatorial plane 40 side. The bead portion 16 is configured by filling the space between the carcass layer 11 and the bead core 17 with a bead filler 18. That is, the bead filler 18 is disposed on the outer circumference side of the bead core 17 in the tire radial direction, so that the carcass layer 11 is fixed to the bead core 17 and the shape of the portion is adjusted, thereby increasing the rigidity of the entire bead portion 16. An inner liner 15 is formed along the carcass layer 11 inside the carcass layer 11.

  By the way, in the pneumatic tire 1 according to the present embodiment, as shown in FIG. 2, the belt outer portions 25 and 26 that are located on the outer side in the tire width direction when the tire is mounted on the vehicle, The belt center portions 27 and 28 located in the center of the tire width direction adjacent to the portions 25 and 26, and the belt inner portions 29 and 30 located in the tire width direction adjacent to the belt center portions 27 and 28 are divided into the respective parts. By varying the angle of the belt cord 23 with respect to the tire circumferential direction, both high-speed durability and steering stability are improved.

  Specifically, in the belt outer portions 25 and 26, the belt cord 23 is provided with an outer portion angle θ1 as a first angle with respect to the tire circumferential direction (that is, the equatorial plane 40). The belt cord 23 is provided with a central portion angle θ2 as a second angle with respect to the tire circumferential direction, and the belt inner portions 29 and 30 have an inner portion angle θ3 as a third angle with respect to the tire circumferential direction. A belt cord 23 is provided. The central portion angle θ2 is larger than the outer portion angle θ1, and the inner portion angle θ3 is larger than the central portion angle θ2, that is, [outer portion angle θ1] <[central portion angle θ2] <[inner portion. The belts 21 and 22 are formed so as to have an angle θ3]. Here, the outer portion angle θ1, the central portion angle θ2, and the inner portion angle θ3 are angles on the acute angle side with respect to the tire circumferential direction. That is, [outer part angle θ1] <[center part angle θ2] <[inner part angle θ3] is a magnitude relationship in the angle on the acute angle side with respect to the tire circumferential direction.

  As a result, since [outside portion angle θ1] <[center portion angle θ2] <[inside portion angle θ3], the belt cord 23 has a tire circumference more than the belt center portions 27 and 28 in the belt outer portions 25 and 26. The outer side angle θ1 of the belt outer side portions 25, 26 that are arranged so as to intersect at a shallow angle with respect to the direction and are located outside when the vehicle is mounted is relatively small, and the circumferential rigidity on the outer side in the tire width direction is high. As a result, the handling stability is improved. On the other hand, the belt cord 23 is disposed so that the belt inner portions 29 and 30 intersect at a deeper angle with respect to the tire circumferential direction than the belt center portions 27 and 28. For example, when the camber angle is a negative camber, Since the inner side angle θ3 of the belt inner parts 29 and 30 where the pressure is increased is relatively large and the rigidity in the circumferential direction on the inner side in the tire width direction is reduced, high-speed durability is improved.

  Further, by sandwiching the belt central portions 27 and 28 between the belt outer portions 25 and 26 and the belt inner portions 29 and 30, the outer portion angle θ1 of the belt outer portions 25 and 26 and the inner portions of the belt inner portions 29 and 30 are increased. The angle difference from the portion angle θ3 can be reduced at the belt central portions 27 and 28, and there is no portion where the angle between the belt cord 23 and the tire circumferential direction changes suddenly.

  Each belt 21 and belt 22 is formed by laminating belt outer portions 25 and 26, belt central portions 27 and 28, and belt inner portions 29 and 30 formed separately, without gaps. Thus, the belt 21 and the belt 22 can be formed after the belt outer portions 25 and 26, the belt central portions 27 and 28, and the belt inner portions 29 and 30 are formed separately. Since the belt cord is not easily bent during the manufacture of the belt 22 and the angle between the belt cord and the tire circumferential direction is easily changed, the manufacturing efficiency can be improved.

  Here, the outer portion angle θ1 is preferably set in the range of 22 degrees to 27 degrees, the central portion angle θ2 is set in the range of 25 degrees to 30 degrees, and the inner portion angle θ3 is set in the range of 28 degrees to 33 degrees. This is because [outside part angle θ1] <[center part angle θ2] <[inside part angle θ3], 22 degrees ≦ outer part angle θ1 ≦ 27 degrees, 25 degrees ≦ center part angle θ2 ≦ 30 degrees, This is because by satisfying 28 ° ≦ inner portion angle θ3 ≦ 33 °, both high-speed durability and steering stability can be balanced.

  Further, as shown in FIG. 2, the boundaries 31 and 32 between the belt outer portions 25 and 26 and the belt center portions 27 and 28 in the belts 21 and 22 and the belt inner portions 29 and 30 and the belt center portions 27 and 28. The boundaries 33 and 34 are preferably located within the ground contact surface in a state where the tire is assembled in a normal rim, the normal internal pressure is filled, and a load 60% of the normal load is applied. This is because the boundaries 31, 32 and the boundaries 33, 34 always receive a stable contact pressure when the vehicle is mounted, and the boundaries 31, 32 and the boundaries 33, 34 do not increase in movement during travel. This is because the belt durability can be improved.

  The regular rim means “applied rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

  Further, as shown in FIG. 3, the tread groove 6a formed on the tread surface 6 which is the surface of the tread portion 5 is located outside with the equator surface 40 at the center in the tire width direction as a boundary in a state where the tire is mounted on the vehicle. It is preferable to make the groove area of the outer tread portion 35 to be smaller than the groove area of the inner tread portion 36 located inside. Here, the groove areas of the tread outer portion 35 and the tread inner portion 36 are the sum of the projected areas of the main groove 6b and the lug groove 6c which are the tread grooves 6a in the respective portions. This is because tread grooves formed on the tread surface 6 of the belt outer portions 25 and 26, that is, the tread outer portion 35, where the rigidity in the tire circumferential direction increases as the angle between the belt cord 23 and the tire circumferential direction becomes smaller. Since the area of 6a is smaller than the area of the tread groove 6a formed on the tread surface 6 of the tread inner portion 36, the rigidity in the tire circumferential direction on the outer side in the tire width direction is further increased, thereby improving steering stability. This is because it can be improved.

  Further, in each of the belts 21 and 22, it is preferable that the number of ends of the belt shoulder portion 37 positioned outside the ground contact surface shown in FIG. 2 is smaller than the number of ends of the belt center portion 38 positioned within the ground contact surface. This is because the belt shoulder portions 37 located outside the ground contact surfaces of the belts 21 and 22 forming the belt layer 20, that is, at both sides in the tire width direction, are located within the ground contact surface, that is, at the center portion in the tire width direction. Since the number of ends is smaller than that of the center portion 38, both side portions in the tire width direction of the belts 21 and 22 are softened. Therefore, the belts 21 and 22 are separated from each other at both end portions in the tire width direction. (So-called belt edge separation) can be suppressed, and separation resistance can be improved.

  The number of ends indicates the unit length of the belts 21 and 22, here, the number of belt cords 23 per 50 mm. Further, the boundary between the belt shoulder portion 37 and the belt center portion 38, and the boundaries 31, 32, 33, 34 between the belt outer portions 25 and 26, the belt center portions 27 and 28, and the belt inner portions 29 and 30 described above, and Does not necessarily match.

  The belt cord 23 of the belt shoulder portion 37 is preferably formed of an organic fiber material. This is because the belt cord 23 is formed of an organic fiber material in the belt shoulder portions 37 of the belts 21 and 22 forming the belt layer 20, so that both side portions in the tire width direction of the belts 21 and 22 are light weight. This is because the belt edge separation can be suppressed and the separation resistance can be improved.

  Further, the pneumatic tire 1 preferably has a flatness ratio of less than 50%. Here, as shown in FIG. 1, the flatness ratio represents the tire height H with respect to the tire width W as a ratio, and when the flatness ratio becomes low, the thickness when the pneumatic tire 1 is viewed from the side. Becomes thinner. When the flatness of the pneumatic tire 1 is less than 50%, the width of the tread surface 6 is widened, and the width of the belt layer 20 is also widened accordingly. Thereby, since tread bending rigidity becomes large, a cornering force improves. Here, at the time of limit cornering in high-speed driving, the portions that are usually out of the ground contact surface, that is, both side portions in the tire width direction are grounded. Become. Therefore, in each of the belt outer portions 25 and 26, the belt central portions 27 and 28, and the belt inner portions 29 and 30 forming the belts 21 and 22, the angles of the belt cord 23 with respect to the tire circumferential direction are set to [outer portion angle θ1] < In the pneumatic tire having a flatness ratio of less than 50%, the present invention that [center portion angle θ2] <[inner portion angle θ3] has the advantage that both high-speed durability and steering stability can be remarkably improved. There is.

  According to the pneumatic tire 1 according to the embodiment of the present invention described above, each of the belts 21 and 22 is located on the outer side in the tire width direction in a state where the tire is mounted on the vehicle, with respect to the tire circumferential direction. The belt outer portions 25 and 26 where the belt cord 23 is provided with the outer portion angle θ1 and the belt outer portions 25 and 26 are adjacent to the belt outer portions 25 and 26 at the center in the tire width direction and are larger than the outer portion angle θ1 with respect to the tire circumferential direction. The belt central portions 27 and 28 where the belt cord 23 is provided with a central portion angle θ2 and the belt central portions 27 and 28 are located adjacent to the belt central portions 27 and 28 in the tire width direction and larger than the central portion angle θ2 with respect to the tire circumferential direction. It has belt inner portions 29 and 30 where the belt cord 23 is provided with an inner portion angle θ3.

  Accordingly, the belt outer portions 25 and 26, the belt center portions 27 and 28, and the belt inner portions 29 and 30 have different angles of the belt cord 23 with respect to the tire circumferential direction, and [outer portion angle θ1] <[center portion angle θ2]. ] <[Inner portion angle θ3], the outer portion angle θ1 of the belt outer portions 25 and 26 located outside the vehicle is relatively small, and the circumferential rigidity on the outer side in the tire width direction is increased. Steering stability is improved. On the other hand, since the inner side angle θ3 of the belt inner parts 29 and 30 is relatively large, the rigidity in the circumferential direction on the inner side in the tire width direction is reduced, and thus high-speed durability is improved. Further, by sandwiching the belt central portions 27, 28 between the belt outer portions 25, 26 and the belt inner portions 29, 30, there is no portion where the angle of the belt cord 23 with respect to the tire circumferential direction changes suddenly. A reduction in stability and high-speed durability can be prevented, and therefore both high-speed durability and steering stability can be improved.

  In the above-described embodiment, the belt outer portions 25 and 26, the belt center portions 27 and 28, and the belt inner portions 29 and 30 are formed separately and are bonded together without gaps to form the belts 21 and 22. However, the belt outer portions 25 and 26, the belt center portions 27 and 28, and the belt inner portions 29 and 30 may be formed integrally to form the belts 21 and 22, respectively. In this case, for example, by bending the belt cord 23 at the boundaries 31, 32, 33, 34, the belts 21, 22 are integrated with the belt outer portions 25, 26, the belt central portions 27, 28 and the belt inner portions 29, 30. As a result, the seam is eliminated, so that the belt durability can be prevented from being lowered. In the above-described embodiment, the belt layer 20 is described as being configured by the two-layer belts 21 and 22. However, more belts may be used.

  Next, examples of the present invention will be described. The pneumatic tire 1 according to the embodiment described above was prototyped, and an evaluation test of performance between the pneumatic tire 1 and a conventional pneumatic tire was performed. The performance evaluation test was conducted on three items: DRY steering stability, high-speed durability with CA, and belt separation durability. The prototype pneumatic tire is 295 / 35R21 107Y. Each test was performed by mounting this pneumatic tire on a rim having a rim size of 21 × 10 J and applying an air pressure of 250 kPa.

  The evaluation method of each test item was performed by mounting the pneumatic tire 1 to be tested on a four-wheel drive vehicle and running on a test course having a total length of 2 km with the four-wheel drive vehicle. Evaluation of the test was performed by sensory evaluation by a driver. The evaluation result is indicated by an index with the evaluation result of Comparative Example 1 described later as 100, and the larger the index, the better the DRY steering stability.

  The high speed durability with CA was performed using a drum having a drum diameter of 1707 mm in a state where the camber angle was set to -2 degrees, that is, in a negative camber state. The test was evaluated until the pneumatic tire was damaged, and the evaluation was based on the damaged speed. The evaluation results are indicated by an index with the evaluation result of Comparative Example 1 described later as 100, and the higher the index, the better the high-speed durability with CA.

  Regarding the belt separation durability, in the four-wheel drive vehicle to be tested, a = 18 m ± 2 m at the Remni skate curve r = a√ (cos 2θ), and 0.86 ± 0. The belt separation amount of the tire after running to 05G and making 1000 revolutions was indicated by an index. The evaluation result of Comparative Example 1 to be described later is indicated by an index of 100, and the larger the index is, the better the belt separation durability is.

  FIG. 4 is a diagram showing the results of a performance test of a pneumatic tire according to an example of the present invention. Eight kinds as examples of the present invention and three kinds as comparative examples to be compared with the present invention are tested by the above method. In the first to eighth embodiments, as described above, the belt cord 23 with respect to the tire circumferential direction in the belt outer portions 25 and 26, the belt central portions 27 and 28, and the belt inner portions 29 and 30 forming the belts 21 and 22, respectively. These are pneumatic tires with different angles. On the other hand, Comparative Example 1 is a conventional pneumatic tire in which the angle of the belt cord 23 with respect to the tire circumferential direction is constant in the entire belt, and Comparative Example 2 is in the tire width direction inner side and the tire width direction inner side with substantially the center of the belt as a boundary. Conventional pneumatic tires having different angles, Comparative Example 3, is a conventional pneumatic tire having different angles at the center in the tire width direction and at both sides in the tire width direction.

  Here, the number of belt sections in FIG. 4 indicates the number of belts that are sectioned in the tire width direction with a portion where the angle of the belt cord 23 with respect to the tire circumferential direction changes as a boundary. The cord angle indicates the magnitude relationship of the angle of the belt cord 23 with respect to the tire circumferential direction. In Example 1 to Example 8, [outside part angle θ1] <[center part angle θ2] <[ The inner portion angle θ3], which is a more specific value. Comparative Example 1 is not described because the angle is constant, and Comparative Example 2 and Comparative Example 3 show only the magnitude relationship.

  The inner / outer groove area means the groove area ratio of the tread groove 6a formed on the tread surface 6 of the tread inner portion 36 (see FIG. 3) and the groove area ratio of the tread outer portion 35 (see FIG. 3), respectively. It is shown. The boundary position indicates whether the boundaries 31, 32, 33, and 34 (see FIG. 2) where the angle of the belt cord 23 is changed are inside the ground plane or outside the ground plane. The number of Ce / Sh ends indicates the number of ends in the belt center portion 38 (Ce) of each belt 21 and 22 and the number of ends in the belt shoulder portion 37 (Sh). The Sh cord material indicates the material of the belt cord 23 in the belt shoulder portion 37 (Sh) of each of the belts 21 and 22. In the present embodiment, a metal cord is used for the belt cord 23 in the belt center portion 38 (Ce) of each belt 21 and 22.

  As is clear from FIG. 4, the pneumatic tires shown in “Comparative Example 2” and “Comparative Example 3” improve the high-speed durability with CA as compared with the pneumatic tire shown in “Comparative Example 1”. On the other hand, it can be seen that the DRY steering stability is lowered, that is, it is difficult to achieve both high-speed durability with CA and DRY steering stability.

  On the other hand, the pneumatic tire 1 shown in “Example 1” to “Example 8” is compared with the pneumatic tire shown in “Comparative Example 1”, belt outer portions 25 and 26, belt center portion 27, 28, and the belt inner portions 29 and 30, the angle of the belt cord 23 with respect to the tire circumferential direction is made different so that [outer portion angle θ1] <[center portion angle θ2] <[inner portion angle θ3]. In the embodiment, both the high-speed durability with CA and the DRY steering stability can be improved.

  In particular, the pneumatic tire 1 shown in “Example 1” is 22 degrees ≦ outer part angle θ1 ≦ 27 degrees and 25 degrees compared to the pneumatic tire 1 shown in “Example 2” and “Example 3”. Since the outer part angle θ1 = 25 degrees, the central part angle θ2 = 28 degrees, and the inner part angle θ3 = 32 degrees so that the central part angle θ2 ≦ 30 degrees and 28 degrees ≦ the inner part angle θ3 ≦ 33 degrees are satisfied. The high-speed durability with CA and the DRY steering stability can be balanced.

  Further, the pneumatic tire 1 shown in “Example 1” has a groove area of the tread groove 6a formed in the tread surface 6 as compared with the pneumatic tire 1 shown in “Example 4” and “Example 5”. However, since the tread outer portion 35 is smaller than the tread inner portion 36, the rigidity in the tire circumferential direction on the outer side in the tire width direction is further increased, so that steering stability can be improved more effectively. Yes.

  Compared with the pneumatic tire 1 shown in "Example 1", the pneumatic tire 1 shown in "Example 6" has boundaries 31, 32, 33, 34 (where the angle of the belt cord 23 with respect to the tire circumferential direction changes). Since the boundary 31, 32, 33, and 34 always receive a stable ground pressure, the belt durability can be improved. .

  Further, in the pneumatic tire 1 shown in “Example 7”, the number of ends of the belts 21 and 22 is more in the belt shoulder portion 37 than in the belt center portion 38 as compared with the pneumatic tire 1 shown in “Example 6”. Therefore, the belt edge separation can be suppressed and the separation resistance can be further improved. In the pneumatic tire 1 shown in “Example 7”, compared with the pneumatic tire 1 shown in “Example 6”, the high-speed durability with CA is slightly lowered, while the DRY steering stability is slightly It has improved.

  Further, the pneumatic tire 1 shown in “Example 8” is different from the pneumatic tire 1 shown in “Example 6” in the belt cords in the belt shoulder portions 37 of the belts 21 and 22 forming the belt layer 20. Since 23 is formed of an aromatic polyamide fiber as an organic fiber material, here, a Kevlar (registered trademark) material, belt edge separation can be suppressed and separation resistance can be further improved. In the pneumatic tire 1 shown in “Example 8”, the DRY steering stability is slightly lowered as compared with the pneumatic tire 1 shown in “Example 6”, while the high-speed durability with CA is slightly lower. It has improved.

  As described above, the pneumatic tire according to the present invention improves the high-speed durability and the handling stability by changing the angle of the belt cord with respect to the tire circumferential direction at the outer portion, the central portion, and the inner portion of the belt. In particular, it is suitable to be applied to a tire having a low aspect ratio, but it is useful to be applied to any pneumatic tire regardless of whether the aspect ratio is high or low.

It is meridional sectional drawing which shows the principal part of the pneumatic tire which concerns on embodiment of this invention. It is a top view which shows the laminated structure of the belt of the pneumatic tire which concerns on embodiment of this invention. It is the schematic of the tread part of the pneumatic tire which concerns on embodiment of this invention. It is a figure which shows the result of the performance test of the pneumatic tire which concerns on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 5 Tread part 6 Tread surface 6a Tread groove 11 Carcass layer 15 Inner liner 16 Bead part 17 Bead core 20 Belt layers 21, 22 Belt 23 Belt cord 25, 26 Belt outer side parts 27, 28 Belt center parts 29, 30 Belt Inner part 31, 32, 33, 34 Boundary 35 Tread outer part 36 Tread inner part 37 Belt shoulder part 38 Belt center part θ1 Outer part angle θ2 Central part angle θ3 Inner part angle

Claims (9)

In a pneumatic tire in which a carcass layer is bridged between a pair of bead cores, and a belt layer composed of a plurality of belts is disposed on the outer circumference in the tire radial direction of the carcass layer,
The belt is
A belt outer portion located on the outer side in the tire width direction and provided with a belt cord at a first angle with respect to the tire circumferential direction;
A belt center portion adjacent to the belt outer side portion and located at the center in the tire width direction and provided with a belt cord at a second angle larger than the first angle with respect to the tire circumferential direction;
And a belt inner side portion that is located on the inner side in the tire width direction adjacent to the belt center portion and in which a belt cord is provided at a third angle larger than the second angle with respect to the tire circumferential direction. To
Pneumatic tire. The first angle is set in a range from 22 degrees to 27 degrees, the second angle is set in a range from 25 degrees to 30 degrees, and the third angle is set in a range from 28 degrees to 33 degrees,
The pneumatic tire according to claim 1. A tread groove formed in an asymmetric pattern with respect to the tire width direction on the tread surface disposed on the tire radial direction outer periphery of the belt layer,
The tread groove is characterized in that the area of the groove located on the outer side with respect to the center in the tire width direction is smaller than the area of the groove located on the inner side when mounted on the vehicle.
The pneumatic tire according to claim 1 or claim 2. The boundary between the belt outer portion and the belt central portion and the boundary between the belt inner portion and the belt central portion were loaded with a normal internal pressure by incorporating a tire into a normal rim, and a load of 60% of the normal load was applied. Located in the ground plane in the state,
The pneumatic tire according to any one of claims 1 to 3. The belt is characterized in that the number of belt cords per unit length of the belt shoulder portion located outside the ground contact surface is smaller than the number of belt cords per unit length of the belt center portion located within the ground contact surface. To
The pneumatic tire according to claim 4. The belt cord of the belt shoulder portion is formed of an organic fiber material,
The pneumatic tire according to claim 5. The belt outer portion, the belt center portion, and the belt inner portion are formed separately, and are bonded together without a gap to form the belt,
The pneumatic tire according to any one of claims 1 to 6. The belt outer part, the belt center part and the belt inner part are integrally formed to form the belt,
The pneumatic tire according to any one of claims 1 to 6. The aspect ratio is less than 50%,
The pneumatic tire according to any one of claims 1 to 8.

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