JPH04356204A - Pneumatic radial tire and its combined unit - Google Patents

Abstract

PURPOSE:To improve high speed durability. CONSTITUTION:This is a tire having side edge portions of at least one cord ply of a carcass 14, which is composed of radially arranged cord plies of a toroid shape extending over a pair of bead portion 16, wound up from the inside to the outside of the tire around a bead core 18, and a belt 26, which is made of a plural number of cord arrangement layer, arranged on the outer circumferential side of a crown portion of the carcass 14. At least strip of an indent portion 32 continuously extending in the peripheral direction of the tire is provided between the vicinity of a shoulder portion and that of a bead portion on the outside surface of the tire.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a pneumatic radial tire with excellent high-speed durability and a combination thereof.

0002

[Prior Art] A pneumatic radial tire is equipped with a carcass consisting of radially arranged cord plies and a belt consisting of a plurality of cord arrangement layers disposed on the outer periphery of the crown portion of the carcass. "Taga"
As a result, compared to bias tires, the tread rubber that makes up the tread surface of the tire moves less, and has many advantages such as superior durability, wear resistance, and handling stability, and low rolling resistance. With the expansion and development of expressway networks in recent years, they have come to be installed on many vehicles.

On the other hand, pneumatic radial tires have also had their treads and beads reinforced in order to cope with high-speed driving as vehicle performance has improved in recent years. As a result, there is an even stronger need than ever for improvements in the high-speed durability of tires. Therefore, the number of cords that make up the carcass and belt,
Techniques have been proposed to suppress distortion and heat generation in areas where failures are likely to occur, and to increase the rigidity of tire cases, by changing the driving angle or adding new reinforcing members.

0004

[Problems to be Solved by the Invention] However, with such proposed technology, the rigidity of the tire case as a whole increases, or there are parts where the rigidity is increased more than necessary, which reduces the movement of the tire. This is not only unfavorable in terms of performance and ride comfort, but also has disadvantages such as an increase in the cost and weight of the tire due to the increase in the number of reinforcing members. The present invention aims to solve such problems, and provides a new pneumatic radial tire that can effectively improve high-speed durability even when applied to known tires, and a new pneumatic radial tire of the tire. The purpose is to provide a combination.

[0005]

[Means for Solving the Problems] The pneumatic radial tire of the present invention has a carcass consisting of a radially arranged cord ply extending across a pair of beads to form a toroidal shape, the side of at least one cord ply. The end portions are wound up around the bead core from the inside of the tire to the outside of the tire, and when a belt layer consisting of a plurality of cord arrangement layers is arranged on the outer circumferential side of the crown portion of the carcass, and the vicinity of the bead, the outer surface of the tire is provided with at least one recess that extends continuously in the tire circumferential direction and bulges out to the outside of the tire as the internal pressure applied to the tire increases. It is.

More preferably, the recessed portion is located adjacent to a circular arc portion having a center of curvature on the outside of the tire in the cross section in the width direction of the tire, and to the inside and outside of this circular arc portion in the tire radial direction, and The center of curvature is located inside the tire, and each circular arc portion is smoothly continuous with the center of curvature of the tire.

Preferably, when a tire mounted on a specified rim is filled with a specified internal pressure, the creepage length of the recessed portion is
The range is 4 to 25% of the tire creeping length from the tire equatorial plane to one bead base.

[0008] Also preferably, the bottom of the recess is
7 to 5 measured along the carcass line from the belt end position with the tire mounted on the specified rim filled with the specified internal pressure.
Position it within the range of 0mm.

More preferably, when the tire assembled on the specified rim is filled with an internal pressure of 0.3 kg/cm2, most of the carcass line corresponding to the recess is moved to the outer side of the tire within the cross section in the width direction of the tire. The carcass line corresponding to each adjacent inner and outer portion of the recess in the radial direction of the tire is formed into an arc shape with the center of curvature located inside the tire,

Alternatively, while most of the carcass line corresponding to the recess is straight in the cross section in the width direction of the tire, the carcass line corresponding to each of the inner and outer adjacent parts of the recess in the radial direction of the tire is The line is an arc with the center of curvature inside the tire,

Alternatively, most of the carcass line corresponding to the recess is formed into an arc shape with the center of curvature located inside the tire in the cross section in the width direction of the tire, and adjacent to the inside and outside of the recess in the radial direction of the tire. The carcass line corresponding to each part is also made into an arc shape with the center of curvature located inside the tire, and the radius of curvature of the arc-shaped carcass line part corresponding to the depression part corresponds to the part adjacent to the depression part. It should be at least 100 times that of the carcass line.

Furthermore, the tire combination of the present invention preferably has at least one strip extending continuously in the tire circumferential direction on the outer surface of the tire between the vicinity of the shoulder portion and the vicinity of the bead portion of each tire. A recessed portion is provided, and the creeping length of this recessed portion when the tire is assembled to a specified rim and filled with the specified internal pressure is 4 to 25 of the tire creeping length from the tire equatorial plane to one bead base. % range, the ratio of the height from the bead base of the bottom of the recess of the tire mounted on the front axle to the tire cross-sectional height is the ratio of the bottom of the recess of the tire mounted on the rear axle.
It is larger than the similar height ratio.

[0013]

[Function] In the pneumatic radial tire of the present invention, for example, a single depression formed on the outer surface of the tire between the vicinity of the shoulder portion and the vicinity of the bead portion increases as the internal pressure applied to the tire increases. The tire bulges particularly outwardly, and as a result, the carcass portion corresponding to the dent also bulges greatly in the same direction. The tension load on the corresponding carcass part will also increase, resulting in an increase in the tire stiffness in the part where the depression has been formed and, in particular, in the part adjacent to the depression. will be effectively increased without substantial deformation of .

[0014] Therefore, the parts located adjacent to the recesses that can increase the stiffness of the tire without causing substantial deformation of the carcass, such as belt end parts, parts near the tire maximum width position, etc. By locating the tire in this position, it can be used under high tire rigidity without causing cord end separation or other inconveniences due to carcass deformation.
The high-speed durability of tires can be effectively improved.

[0015] Here, the reason why the recess is formed between the vicinity of the shoulder part and the vicinity of the bead part of the tire is that if the recess is located in the tread part beyond the vicinity of the shoulder part, Belt separation is likely to occur due to increased distortion of the rubber due to the outward bulge of the tire in the corresponding carcass area. This is because it has high rigidity, so providing a recess near the bead core is ineffective.

By the way, when this tire is mounted on a specified rim and filled with a specified internal pressure, the creepage length of the recessed portion is calculated as the tire creepage length from the tire equatorial plane to one bead base. When it is within the range of 4 to 25%, the above-mentioned function of the recessed portion can be more effectively exhibited.

In other words, if it is less than 4%, the creepage length of the recessed portion becomes too short, so when filling the internal pressure into the tire assembled on the rim, the recessed portion must not expand sufficiently toward the outside of the tire. As a result, it is not possible to sufficiently increase the tension of the carcass corresponding to the depression and the adjacent parts, and if the tension exceeds 25%, the tire Since a corresponding portion of the carcass is bulged outward and the tension acting on the carcass is dispersed, it is not possible to increase the tension load on a desired portion to the desired extent.

[0018] Here, if the recessed part is formed in the cross section in the width direction of the tire by two circular arc parts, one having its center of curvature on the outside of the tire and the other having its center of curvature on the inside of the tire, The amount of expansion of the recessed portion can be increased more actively, and the tension load acting on the carcass can be further increased.

In addition to this, when the bottom of the recess is located within a range of 7 to 50 mm as measured along the carcass line from the belt end position while the tire is filled with the specified internal pressure. In this way, it is possible to sufficiently increase the tire rigidity in the required portion from the belt end to the tread portion.

In other words, if the distance between the bottom of the recess and the end of the belt is less than 7 mm, the strain of the rubber at the end of the belt will increase excessively as the tension load on the carcass corresponding to the recess increases. If the distance exceeds 50 mm, the recess will be too close to the bead core in the bead, and as mentioned above, the carcass will be damaged. , the effect contributing to the tension load at the belt end is small, and the degree of improvement in steering stability is small.

[0021] In addition, a tire with at least one recessed portion is installed on a specified rim, and a tire of 0.3 km is attached to the specified rim.
When filled with an internal pressure of g/cm2, most of the carcass line corresponding to the recess is shaped into an arc with the center of curvature on the outside of the tire in the cross section in the width direction of the tire. When the carcass line corresponding to the adjacent inner and outer parts in the radial direction is formed into an arc shape with the center of curvature inside the tire, filling the tire with internal pressure will cause the carcass part corresponding to the hollow part to reach natural equilibrium. As the tire bulges outward to approximate its shape, the arcuate shape of the carcass part effectively promotes the bulging deformation, reducing the tension in the carcass part corresponding to the depression and in each carcass part adjacent to it. This further increases the load, and therefore, it is possible to more fully increase the rigidity of the required portions of the tire, thereby effectively improving both high-speed running performance and high-speed durability.

In this case, by making the carcass line corresponding to the portion adjacent to the recess into an arc shape with the center of curvature located inside the tire, arcs with different curvatures are smoothly connected, and one point of the recess is formed. Damage to the carcass due to stress concentration can be prevented.

[0023] By the way, these things mean that most of the carcass line corresponding to the recessed part is made straight in the cross section in the width direction of the tire, and that the recessed part corresponds to the inner and outer adjacent parts of the tire in the radial direction. If the carcass line is shaped like an arc with the center of curvature on the inside of the tire, and if most of the carcass line corresponding to the depression is shaped like an arc with the center of curvature on the inside of the tire in the cross section in the width direction of the tire. and the radius of curvature of the arc is 1 of the radius of curvature of the carcass line corresponding to the part adjacent to the depression.
The same holds true in all cases where the ratio is 00 times or more. In the latter case, the radius ratio is set to 100 times or more because if it is less than 100 times, a sufficiently large tension cannot be applied to the carcass portion corresponding to the depression.

[0024] Moreover, no matter which carcass line shape is selected as described above, the tire internal pressure is set to 0.3.
When the internal pressure is increased from kg/cm2 to the specified internal pressure, the outer surface diameter expansion at the belt ends becomes larger than that at the tire equatorial plane, so the tire rigidity at the belt ends increases particularly. As a result, the tire's ground contact performance is improved, and as a result, the tire's high-speed durability, cornering performance and other handling performance, uneven wear resistance, etc. are greatly improved.

Furthermore, the tire combination of the present invention provides excellent handling performance to the front tires and high torque bearing capacity to the rear tires, among the tires installed on the same vehicle. This was done for other purposes, and in particular, it was made to calculate the ratio of the height of the bottom of the recess of a tire mounted on the front axle from the bead base to the cross-sectional height of the tire mounted on the rear axle. By making the height ratio of the bottom of the tire depression larger than the similar height ratio, the front tire has an increase in the rigidity of the belt end portion, and the rear tire has an increase in the rigidity of the sidewall portion, thereby achieving the above. Make it possible to achieve your goals.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on illustrated examples. FIG. 1 is a diagram showing a cross section in the width direction of a tire according to the present invention, and shows a state in which a tire 10 is assembled to a specified rim 12 and filled with an internal pressure of 0.3 kg/cm2. Here, the carcass 14 is constituted by a radially arranged cord ply having a toroidal shape spanning a pair of bead portions 16 located apart in the axial direction of the tire. In the illustrated example, the carcass 14 is composed of a single cord ply, and each side end portion of the cord ply is wound around a bead core 18 provided in the bead portion 16 from the inside of the tire to the outside. Although it has an up structure,
The carcass 14 can also be composed of a plurality of cord plies depending on the specifications of the tire. In this case, at least one cord ply is connected to the bead core 18.
around it, roll it up as described above.

A bead filler 20 and a reinforcing layer 22 are provided between the main body portion of the carcass 14 and its turn-up portion 14a, respectively, so that the bead portion 16 and the sidewall portion of the tire are reinforced. do. Note that the number and placement positions of the reinforcing layers 22 are not limited to the embodiments, and can be appropriately selected as required.

[0028] Also, the tread portion 2 forming the tire tread surface
4, a belt 26 made of a plurality of cord arrangement layers is disposed on the outer peripheral side of the crown portion of the carcass 14, and a known high-speed radial tire is installed around the end portion of the belt 26 in the tire width direction. Similarly, it is reinforced by a reinforcing layer 28.

According to the present invention, the tread portion 2
At least one recess that is recessed toward the inner surface of the tire 10 and extends continuously in the circumferential direction of the tire 10 between the vicinity of the shoulder portion located adjacent to the tire 10 and the vicinity of the bead portion. 32 is provided.

In the pneumatic radial tire constructed as described above, as the tire is filled with the specified internal pressure, the outer contour line of the tire changes to the outer side of the tire at the portion including the recessed portion 32, as shown in FIG. As a result, the carcass 14 expands from the portion corresponding to the recessed portion 32 to the respective portions adjacent to the inner and outer sides of the recessed portion 32 in the tire radial direction, for example, the tire maximum width portion W and Since a large tension is applied to the part corresponding to the shoulder part S, the tire rigidity near the maximum tire width position and the tire rigidity at the belt end are both effectively increased, and at the same time, the belt end As a result, the movement of the tread rubber at certain points is effectively suppressed, and as a result, the high-speed durability of the tire can be sufficiently increased without any additions or changes to the tire's constituent materials, and the handling stability can still be improved. can be effectively improved.

[0031] Here, the reason why the recessed part 32 is formed between the vicinity of the shoulder part and the vicinity of the bead is to eliminate the fear of separation at the end of the belt, and also to form the recessed part between the vicinity of the shoulder part and the vicinity of the bead. This is to ensure sufficient effectiveness.

More preferably, in such a tire, the creepage length of the recessed portion 32 is preferably 4 to 25% of the tire creepage length when the tire is mounted on a specified rim and is filled with a specified internal pressure. Select a range of 10% to 20%. Here, the tire creepage length is the curved length measured along the tire outer contour line from the tire equatorial plane In the case where a groove exists on the tread surface, the length is defined as the length passing through a line segment connecting the surfaces of adjacent land areas across the groove. Also, the creepage length of the recess is
As shown by distance P in the enlarged cross-sectional view of FIG. 3, when a straight line is drawn that circumscribes both the inner and outer parts of the tire in the radial direction, with the recessed part 32 in between. The length of the curve measured along the tire outer contour line from one point of contact with the straight line to the other point of contact with the straight line.

When the creepage length P of the recessed portion 32 is selected in this manner, the above-mentioned effects derived from the recessed portion 32 can be made even more remarkable. In other words, the creepage length P of the recessed portion 32 is 4% of the tire creepage length L.
If it is less than 25%, as mentioned above, the amount of bulge of the recessed part 32 to the outside of the tire will be small, making it impossible to increase the tension load on the carcass as expected, and if it exceeds 25%, the bulge will increase. This also occurs due to the area becoming too large.
The required tension load on the carcass part cannot be increased as desired.

By the way, in this tire, in particular, by locating the recess bottom 32d within a range of 7 to 50 mm as measured along the carcass line from the belt side end position 26a, the distance from the belt end to the tread portion is improved. Increase the rigidity of the necessary parts in between.

In other words, if it is less than 7 mm, the recessed portion 32 will be too close to the belt 26, resulting in an increase in the tension burden on the carcass portion corresponding to the recessed portion 32, that is, a bulging displacement of the carcass portion. As a result, the rubber distortion at the belt end increases, making it easy to cause separation or other failures at the belt end.
If it exceeds m, the recessed portion 32 will come too close to the bead core 18, and the effect of the carcass contributing to the tension burden at the end of the belt will be small, and the degree of improvement in steering stability will be reduced.

Furthermore, in this tire, the outline of the recessed portion 32 in the cross section in the width direction of the tire is formed by three mutually smoothly continuous circular arc portions 32a, 32b, and 32c, thereby making it more The amount of expansion of the recessed portion 32 can be actively increased, and the tension load acting on the carcass can be further increased.

FIG. 4 is a cross-sectional view of a main part showing another example in which the carcass line is improved in relation to the recess formed on the outer surface of the tire. This is due to the expansion of the recessed portion 32 provided on the outer surface of the tire toward the outside of the tire.
The expansion of the carcass in the same direction is sufficiently smoothed, and for example, the tire rigidity is increased at the belt end and near the tire maximum width position, thereby more effectively improving high-speed running performance and high-speed durability performance. In order to do this, the carcass, which is a structural member for reinforcing the tire, is naturally embedded in the recess 32 and has a much higher elastic modulus than the rubber constituting the outer surface of the tire. This was done based on the knowledge that it is preferable to make the curvature of the carcass line of a portion significantly different from that of the carcass line corresponding to the inner and outer adjacent portions of the recessed portion 32 in the tire radial direction. .

[0038] In the example shown in Fig. 4(a), the tire is mounted on the specified rim and the internal filling pressure is set to 0.3k.
g/cm2, most of the carcass line corresponding to the recessed part 32 is made into a circular arc shape with a radius R with the center of curvature located on the outside of the tire in the tire width direction cross section, and the recessed part 32 is , the carcass line corresponding to each adjacent inner and outer part of the tire in the radial direction,
Radius RA and RB with center of curvature inside the tire
It is shaped like an arc.

Further, in the example shown in FIG. 4(b), the recessed portion 32
Most of the carcass line corresponding to the tire is made straight in the cross section in the width direction of the tire, and the carcass line corresponding to each of the adjacent inner and outer parts of the recessed part in the tire radial direction is made to have a curvature on the inside of the tire. centered, radius R
A and RB are arcuate, as shown in Figure 4(c).
In the example shown in , most of the carcass line corresponding to the recessed portion 32 is formed into an arc shape with a radius RO with the center of curvature inside the tire in the cross section in the tire width direction, and the recessed portion 32
The carcass line corresponding to each part adjacent to , with the center of curvature on the inside of the tire,
In the arc shape of B, the radius R0 is 100 times or more of each of the radii RA and RB.

According to these facts, when the recessed portion 32 of the tire expands toward the outside of the tire due to the filling of internal pressure into the tire, the carcass portion corresponding to the recessed portion 32 has a so-called natural equilibrium shape. This means that the bulge deformation is performed to approach the shape of the carcass, and the bulge changes of the carcass portion directly and indirectly of the recessed portions are effectively promoted. Therefore, by selecting the location and dimensions of the recess 32, it is possible to increase the tension load in the required carcass part in a desired manner, for example to increase the tire stiffness in the belt end part and in the vicinity of the maximum width position of the tire. By doing so, the high-speed running performance and high-speed durability of the tire can be sufficiently improved. In addition, Figure 4
In the example shown in (c), radius R0 is defined as radius RA,
To make it 100 times more than RB is to make it 100 times more than RB.
This is because when it is less than double, the tension load on the carcass portion corresponding to the recessed portion 32 and the portions adjacent thereto cannot be sufficiently increased.

Moreover, according to the tire of this example, when the tire internal pressure is increased from 0.3 kg/cm2 to the specified internal pressure, as shown in FIG. ΔS is larger than the amount of outer diameter bulge ΔL at the tread center, which not only increases the tire rigidity at the tread edge, but also improves the tire's ground contact, which improves the tire's high-speed durability. In addition to this, it is also possible to effectively improve maneuverability, including cornering performance, and uneven wear resistance.

When actually applying the tires described above to a vehicle, the tires mounted on the front axle should have excellent handling performance, and the tires mounted on the rear axle should have excellent torque. Since durability is required in each case, a tire combination that fully satisfies these requirements is provided here.

FIG. 6 is a schematic diagram partially illustrating the outer contour of the tire combination, and FIG.
(b) shows the outer contour of each rear tire mounted on the rear axle. Here, the ratio (h
F /HF) is the height hR of the bottom 32d of the recess 32 from the bead base in the rear tire 10R.
to the tire cross-sectional height HR (hR /HR
) by making the front tire 10F larger.
The position of the recess bottom 32d of the rear tire 10R is positioned relatively close to the belt end, while the recess bottom 32d of the rear tire 10R is positioned relatively close to the belt end.
2d is located relatively close to the bead portion.

Therefore, in the front tire 10F, the rigidity of the portion near the belt end is increased, and the steering performance of the tire is improved as expected, and in the rear tire 10R, the rigidity of the sidewall portion is increased, This results in improved traction and braking performance of the tire.

FIG. 7 is a displacement diagram of the tire contour line showing this. In the front tire shown in FIG. 7(a), as the filling internal pressure increases, the amount of expansion of the tire near the shoulder portion is particularly large. In the rear tire shown in FIG. 7(b), the amount of tire bulge is particularly large at a portion slightly closer to the shoulder than the tire maximum width position. In any of these tires, the recessed portion 32 is located between the vicinity of the shoulder portion and the vicinity of the bead portion, more preferably between the vicinity of the tire maximum width position, and the creepage length P of the recessed portion 32 is , is within the range of 4 to 25% of the tire creeping length L, so that the effects specific to the tire according to the present invention can be fully achieved.

[Test Example 1] A comparative test regarding high-speed durability between the invention tire and the comparative tire will be explained below. ◎Tire with a test tire size of 255/40ZR 17 / Invention tire This tire has the basic structure shown in the cross-sectional view in Figure 1. In addition, in the case shown in FIG. 1, the radial carcass is made up of one piece of radially arranged cord ply, but here, the radial carcass is composed of one sheet of cord ply arranged in a radial arrangement. A radial carcass was constructed from two radially arranged cord plies made of 66 nylon cord having a thickness of 1260 d/2. Of these two cord plies, the end of the ply located inside the tire,
The ends of the ply located on the outside of the tire were rolled up around the bead core from the inside of the tire to the outside, and from the outside of the tire to the inside.

[0047] Also, between the turn-up part of the carcass rolled up from the inside to the outside of the tire and the bead filler arranged on the outer peripheral side of the bead core, and between the turn-up part and other carcass located outside the tire. A reinforcing layer was placed between each section. These reinforcing layers are composed of aromatic polyamide cords with a thickness of 1500 d/2 arranged at an angle of approximately 30 degrees to the tire circumferential direction, and their maximum height measured from the bead base is 43 mm. did. The belt is made of aromatic polyamide cord with a thickness of 1500 d/2 and is made of aromatic polyamide cord with a thickness of approximately 3
It has a two-layer structure diagonally intersecting each other at an angle of 5 degrees, and the auxiliary layer is a thick layer that is wound in the tire circumferential direction and reinforces the end portion of the belt in the tire width direction over approximately 30% of the width. Constructed from 66 nylon cord with a length of 1260d/2.

[0048] Furthermore, regarding the hollow part, the tire was assembled on the specified rim (9 x 17) and the specified internal pressure (2.5 kg/cm) was applied.
2) When filled, its bottom is located at approximately 68.6% of the tire cross-sectional height from the bead base, and its creeping length P is the tire creeping length L (= 210 mm
) was approximately 9.5%.

Comparison Tire A tire having the same structure as Invention Tire 1 except that it does not have a recessed part ◎Test method A tire is pressed against a drum with a diameter of 2 m with a force of about 500 kg, and the peripheral speed of the drum is increased to 150 km/h. 10km from h
A high-speed durability drum test was conducted in which the speed was increased stepwise by /h and each speed was maintained for 10 minutes, and the failure occurrence rate and failure condition were investigated. ◎Test Results Table 1 shows the test results for each tire.

[0050]

[Table 1] According to this Table 1, according to the invention tire,
It is clear that the durability speed can be effectively improved compared to the comparative tires.

[Test Example 2] A comparative test regarding high-speed durability between an inventive tire and a comparative tire in which carcass lines corresponding to the recessed portion and its vicinity were selected will be described below. ◎Tire with a test tire size of 255/40 ZR 17/Invention Tire 1 A tire having the same configuration as Invention Tire 1 described in Test Example 1, with a carcass line corresponding to the depression and its vicinity. , with the shape shown in Figure 4(a). Here, when filling with an internal pressure of 0.3 kg/cm2, the radius of curvature R is 100 mm, and the radius of curvature RA is 40 m.
m, and the radius of curvature RB was set to 40 mm. Furthermore, the bottom of the depression provided on the outer surface of the tire is placed on the specified rim (
9 x 17) and maintain the specified internal pressure (2.5 kg/cm2).
) was placed at a height of approximately 68.6% of the tire cross-sectional height H (=102 mm) from the bead base.

- Inventive Tire 2 The carcass line corresponding to the depression and its vicinity was shaped as shown in FIG. 4(b), and the radius of curvature RA was 40 m.
A tire having the same structure as Invention Tire 1 except that the radius of curvature RB was 40 mm. - Inventive tire 3 The carcass line corresponding to the depression and its vicinity was shaped as shown in Fig. 4(c), and the radius of curvature R0 was 500.
A tire having the same structure as Invention Tire 1 except that the radius of curvature RA was 40 mm and the radius of curvature RB was 40 mm.

- Comparative Tire 1 This is the same as Invention Tire 1 except that the depressions on the outer surface are omitted. Comparison Tire 2 Inventive Tire 3, with radius of curvature R0 being 80 times the other radii of curvature RA and RB.

◎Test Method A test similar to the high speed durability drum test described in Test Example 1 was conducted. ◎Test Results Table 2 shows the test results for each tire.

[0055]

[Table 2] According to this Table 2, it is clear that all of the invention tires can significantly improve the durability speed compared to the comparative tires.

[Test Example 3] A comparative test regarding high-speed durability, handling stability, and lap time between a tire combination according to the present invention and a comparative tire combination will be described below. ◎Test Tire The front tire size was 205/50 ZR 17, and the rear tire size was 255/40 ZR 17.

- The basic structure of the invention tire was the same as that of invention tire 1 in Test Example 1,
Each of the front and rear tires was assembled onto a specified rim (7 x 17, 9 x 17), and each tire was filled with the specified internal pressure (2.5 kg/cm2). For front tires, the bottom of the recess is measured from the bead base to the tire cross-sectional height H (=103mm
), and the creepage length P of the recessed portion is set to the tire creepage length L (=185mm
), and for rear tires, the bottom of the recess is measured from the bead base to the tire cross-sectional height H (
= 102 mm), and the creepage length P of the recessed portion is set to the tire creepage length L (= 2
10 mm).

- Comparative Tire Both the front tire and the rear tire had the same structure as the invention tire except that they did not have any recesses.

◎Test method High-speed durability was evaluated by conducting a test similar to the high-speed durability drum test described in Test Example 1 for the rear tires of the invention tire and comparative tire, and the handling stability and Each lap time was evaluated based on the feeling of driving on a circuit course with front and rear tires mounted on an actual vehicle and the time required to go around the circuit. The steering stability is evaluated using the comparative tire as a control using an index value, and the larger the index value, the better the result.

◎Test Results Of these tests, the high-speed durability is shown in Table 3, and the handling stability and lap time are shown in Table 4.

[0061]

[Table 3]

[0062]

[Table 4]

It is clear from Table 3 that the high-speed durability of the invention tire can be effectively improved compared to the comparative tire, and the failure condition is not as serious as that of the comparative tire. According to the above, it is clear that the invented tire can significantly improve both lap time and handling stability compared to the comparative tire.

[0064]

Effects of the Invention As is clear from the above description, according to the tire of the present invention, in particular, at least one recessed portion is provided between the vicinity of the shoulder portion and the vicinity of the bead portion on the outer surface of the tire. By doing so, the high-speed durability of the tire can be effectively improved. Furthermore, according to the tire combination of the present invention, in addition to high-speed durability,
It is also possible to sufficiently improve handling stability and lap time.

[Brief explanation of drawings]

FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a bulging state of a tire contour line.

FIG. 3 is a diagram showing the creepage length of a recessed portion.

FIG. 4 is a diagram showing an example of an improved carcass line.

FIG. 5 is a schematic diagram showing a difference in the amount of diameter expansion.

FIG. 6 is a diagram showing the position of the bottom of a recess in the tire assembly.

FIG. 7 is a diagram showing the relationship between the position of the bottom of the recess and the bulge position.

[Explanation of symbols]

10 Tire 12 Rim 14 Carcass 14a Turn-up portion 16 Bead portion 18 Bead core 20 Bead filler 22 Reinforcement layer 24 Tread portion 26 Belt 26a Side end position 28 Auxiliary layer 32 Recessed portions 32a, 32b, 32c Arc portion 32d
Bottom L Tire Creepage Length P Recess Creepage Length H Tire Section Height h Recess Bottom Height X-X Tire Equatorial Plane

Claims (8)

[Claims] Claim 1: In a carcass consisting of a radial array of cord plies extending across a pair of bead portions and forming a toroidal shape, the side end portion of at least one cord ply is extended from the inside of the tire to the outside around the bead core. The tire is a tire in which a belt consisting of a plurality of cord arrangement layers is arranged on the outer circumference side of the crown part of the carcass, and the belt is wound on the outer surface of the tire between the shoulder part and the bead part. At least one recess extending continuously in the circumferential direction is provided, and the depth of the bottom of this recess is set to be lower than that under an internal pressure of 0.3 kg/cm2 when the tire is assembled on a specified rim. A pneumatic tire that is made shallower under the specified internal pressure. [Claim 2] 0.3 to the tire assembled on the specified rim.
Under filling with an internal pressure of kg/cm2, the recessed portion is located adjacent to a circular arc portion having a center of curvature on the outside of the tire in the cross section in the width direction of the tire, and to the inside and outside of this circular arc portion in the tire radial direction. 2. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is formed of circular arc portions that are smoothly continuous to the circular arc portion, with the center of curvature located inside the tire. 3. When the tire is assembled on a specified rim and filled with a specified internal pressure, the creeping length of the recessed portion is set to 4 to 4 of the tire creeping length from the tire equatorial plane to one bead base. A pneumatic tire according to claim 1, wherein the pneumatic tire is in the range of 25%. 4. The bottom of the recessed portion is located within a range of 7 to 50 mm as measured along the carcass line from the belt end position while the tire assembled on the specified rim is filled with a specified internal pressure. The pneumatic radial tire according to claim 1, comprising: [Claim 5] 0.3 to the tire assembled on the specified rim.
Under filling with an internal pressure of kg/cm2, most of the carcass line corresponding to the recessed portion is
In addition to having an arc shape with the center of curvature on the outside of the tire,
2. The pneumatic radial tire according to claim 1, wherein carcass lines corresponding to respective inner and outer adjacent portions of the recessed portion in the tire radial direction are arcuate with a center of curvature located inside the tire. [Claim 6] 0.3 to the tire assembled on the specified rim.
Under filling with an internal pressure of kg/cm2, most of the carcass line corresponding to the recess is made straight in the cross section in the width direction of the tire, and each of the inner and outer adjacent parts of the recess in the tire radial direction 2. The pneumatic radial tire according to claim 1, wherein the carcass line corresponding to the portion has a circular arc shape with the center of curvature located inside the tire. [Claim 7] 0.3 to the tire assembled on the specified rim.
Under filling with an internal pressure of kg/cm2, most of the carcass line corresponding to the recessed portion is
In addition to having an arc shape with the center of curvature inside the tire,
The carcass lines corresponding to the inner and outer adjacent parts of the recess in the tire radial direction are also arcuate with the center of curvature located inside the tire, and the radius of curvature of the arc-shaped carcass line corresponding to the recess is 100 of that of the carcass line corresponding to the part adjacent to the depression.
The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is more than twice as large. 8. In a carcass consisting of a radial array of cord plies extending across a pair of bead portions and forming a toroidal shape, the side end portion of at least one cord ply is moved from the inside of the tire to the outside around the bead core. It is a combination of pneumatic radial tires that are installed on each of the front and rear axles of a vehicle, with a belt made of multiple cord arrangement layers arranged around the outer circumference of the crown of the carcass. On the outer surface of each tire, between the shoulder area and the bead area,
At least one recess extending continuously in the circumferential direction of the tire is provided, and the creeping length of this recess when the tire is assembled to a specified rim and filled with a specified internal pressure is determined from one bead base from the tire equator plane. 4 to 25% of the tire creepage length up to
and the ratio of the height of the bottom of the recess of the tire mounted on the front axle from the bead base to the tire cross-sectional height is the same as that of the bottom of the recess of the tire mounted on the rear axle. A combination of pneumatic radial tires that are larger than the height ratio.