JPH11291713A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve high-speed traveling performance of a racing tire. SOLUTION: This pneumatic tire comprises a toroidal carcass 6, a belt layer 7 disposed outside of the toroidal carcass 6 with its belt code arranged at an angle of 10-45 deg. to a tire equator C, and a band layer 9 disposed outside of the belt layer 7 in a tire radial direction. A tread surface 2a is formed with a small number of longitudinal grooves 10 extending in a tire circumferential direction and rib-like parts 12 arranged side by side in the tire axial direction. The band layer 9 comprises a high density part 9a disposed inside of the rib-like part 12a in the tire radial direction having a large number of band codes per tire axial length, and a low density part 9b disposed in side of the longitudinal groove 10 in the tire radial direction having a smaller number of band codes than the high density part 9a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire which can improve tread rigidity and can be suitably used for a racing tire having a vertical groove.

[0002]

2. Description of the Related Art Racing tires are mainly slick tires having no grooves on the tread surface. However, in recent years, due to race safety problems, the cornering speed of racing machines has been reduced. There is an increasing movement to introduce grooved tires for the purpose of lowering them.

[0003] As such a grooved type racing tire, for example, a small number of about 2 to 4 vertical grooves extending in the tire circumferential direction are provided on a tread surface, and between the vertical grooves or between the vertical grooves and the tread end. And a rib-shaped portion formed in the tire axial direction.

Meanwhile, a conventional slick tire has a radially structured carcass and a belt layer for loosening the tread portion of the carcass, and has a radially outer side of the belt layer in order to improve high-speed durability. Is provided with a band layer in which cords are arranged substantially parallel to the tire circumferential direction.

In order to ensure as uniform a ground contact pressure as possible, a band cord is spirally wound substantially along the circumferential direction of the tire, and the band layer per tire axial length is formed on the band layer of such a slick tire. An axially uniform jointless band structure having almost the same number of cords is often used.

However, when such an axial band layer is employed in the grooved tire, since the grooves are formed on the tread surface, the band layer forming region in the tread rubber has a groove depth or the like. During running at high speeds because the tread stiffness, especially the stiffness of the ribs, tends to be low due to the reduction of the tread area and the reduction of the road surface grip force due to the increase in the contact pressure. However, there is a problem that the cornering power is lowered and the durability of the tread rubber is lowered.

The present invention has been devised in view of such a problem, and the band layer has a plurality of band cords located inward of the rib-shaped portion in the tire radial direction and per tire axial length. A tread rigidity, especially a rib that is in contact with the road surface, based on the provision of a high-density portion having a large number and a low-density portion located inward of the longitudinal groove in the tire radial direction and having a smaller number of band cords than the high-density portion It is an object of the present invention to provide a pneumatic tire, in particular, a racing tire, which can increase the rigidity of the shape portion and improve the durability of tread rubber and the like.

[0008]

According to a first aspect of the present invention, there is provided a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, and is disposed inside the tread portion and radially outside the carcass. And a belt layer in which the belt cords are arranged at an angle of 10 to 45 degrees with respect to the tire equator C, and a band arranged radially outside of the belt layer and the band cords are arranged substantially in the tire circumferential direction. A pneumatic tire with a layer, provided on the tread surface a few longitudinal grooves extending in the tire circumferential direction,
A rib-shaped portion is formed between the longitudinal grooves or between the longitudinal groove and the tread end, and is arranged in the tire axial direction, and the band layer is located radially inward of the rib-shaped portion in the tire axial direction and in the tire axial direction. A high-density portion having a large number of band cords per length, and a low-density portion located inward of the longitudinal groove in the tire radial direction and having a smaller number of the band cords than the high-density portion. And

According to a second aspect of the present invention, the high-density portion increases the number of band cords per axial length in the tire axial direction by increasing the number of band plies of the band cord to be greater than the low-density portion. The pneumatic tire according to claim 1, wherein a depth from a tread surface of an outermost belt ply in a tire radial direction of the high-density portion is smaller than a depth of the vertical groove. .

According to a third aspect of the present invention, the high density portion has three band plies, the low density portion has one band ply, and the high density portion has a tire radius. The depth of the outermost band ply in the direction from the tread surface is smaller than the groove depth of the vertical groove and 3.0 mm.
The pneumatic tire according to claim 2, wherein:

According to a fourth aspect of the present invention, the band layer is formed by spirally winding a band cord substantially along a tire circumferential direction. 2. The pneumatic tire according to 1.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In this embodiment, FIG. 1 shows a right half cross-sectional view of a pneumatic tire for racing, but the left half has a symmetric structure. In the figure, a pneumatic tire is provided with a carcass 6 forming a skeleton of the tire and a belt cord arranged inside the tread portion 2 and radially outside the carcass 6 and at an angle of 10 to 45 degrees with respect to the tire equator C. It has a belt layer 7 arranged at an angle and a band layer 9 arranged radially outside of the belt layer 7. For example, a ratio H / of a tire section height H and a tire section width W at the time of standard internal pressure filling is provided. W is 0.5 or less, preferably 0.4 or less,
In this example, a value of 0.35 is exemplified.

The carcass 6 is formed by applying a carcass cord made of an organic fiber cord such as nylon, rayon, polyester, or aramid to the tire equator by 70 to 90%.
It has a radial structure inclined at an angle of degrees.
The carcass plies 6A, 6B are formed.

The carcass 6 is, in this embodiment, a tread portion 2.
The carcass ply 6A is folded back from the inner side to the outer side in the tire axial direction around the bead core 5 of the bead part 4 through the side wall part 3 and the bead passing through the side wall part 3 from the tread part 2 and disposed outside thereof. Part 4
And a carcass ply 6 </ b> B that is folded back from the outside to the inside in the tire axial direction around the bead core 5.

The carcass 6 includes the bead core 5
, And is formed so as to extend outward in the tire radial direction and surround the bead apex 8 made of hard rubber.

The belt layer 7 is formed of two inner and outer belt plies 7A and 7B in the tire radial direction. In the present embodiment, the belt plies 7A and 7B are formed by tilting a belt cord made of steel with respect to the tire equator C at a relatively shallow angle of 10 to 45 degrees with respect to the tire equator C, and between plies overlapping in the tire radial direction. The belt cords are arranged to cross each other. Further, both end portions of the belt layer 7 extend to the tread end E in this example, and the carcass 6 having the radial structure is flared over almost the entire width of the tread portion 2 to reinforce it.

In the present embodiment, the band cord 9 is formed by helically winding the band cord 14 outside the belt layer 7 with fine leads, so that the band cord 14 is, for example, 5 degrees or less with respect to the tire circumferential direction. As an example, an arrangement formed substantially along the tire circumferential direction is shown. Such a band layer 9 does not generate a joint portion as compared with a layer in which wide plies are overlapped, and therefore can restrain the belt layer 7 with high strength, and greatly enhances high-speed durability. On the other hand, it is possible to prevent a decrease in the uniformity, prevent the occurrence of vibration during high-speed running, and improve grip performance. The band cord 14 is preferably a cord having a lower elasticity than the belt cord of the belt layer 7, and among them, an organic fiber cord is preferably used. In this example, a band cord using a nylon cord is shown.

In the pneumatic tire, a small number of vertical grooves 10 are provided on the tread surface 2a in the circumferential direction of the tire, and ribs are formed between the vertical grooves 10, or between the vertical grooves 10 and the tread end E. A part 12 is formed. In this embodiment,
The longitudinal grooves 10 extend linearly and continuously in the tire circumferential direction, and three longitudinal grooves 10 are arranged on the tread surface 2a. Thus, the four rib-like portions 12 are arranged on the tread surface 2a in the tire axial direction.

As shown in FIG. 2, the vertical groove 10 has a groove width GW on the tread surface 2a of, for example, about 10 to 20 mm, in this example, 14 mm, and a groove depth GD of, for example, 2.0 to 2.0 mm.
It is preferably 8.0 mm, and in this example, it is 4.5 mm. In addition, the groove wall surface 10a of the vertical groove 10 is formed of an inclined surface whose groove width is reduced inward in the tire radial direction. The number of the vertical grooves 10 is, for example, 2 to 5,
It is desirable that the number is preferably 2 to 4, more preferably 3.

In the present invention, the band layer 9 includes a high-density portion 9a which is located inside the rib-like portion 12 in the tire radial direction and has a large number of band cords 14 per tire axial length. One of the features is that a low-density portion 9b which is located inside the longitudinal groove 10 in the tire radial direction and in which the number of the band cords 14 is smaller than the high-density portion 9a is included.

As described above, the high-density portion 9a of the band layer in which the number of the band cords 14 per the length in the tire axial direction is provided inside the rib-like portion 12 of the tread surface 2a in the tire radial direction. It is possible to increase the rigidity of the rib-shaped portion 12 and prevent a decrease in cornering power. Further, the high-density portion 9a can suppress lifting of the belt layer 7 due to a large centrifugal force acting on this portion, thereby improving high-speed durability of the tire. In addition, since the weight of rubber is small and the centrifugal force at the time of running is smaller than that of the rib-like portion 12, the low-density portion 9b in which the number of the band cords 14 is small can be arranged in the portion of the vertical groove 10.

In the present embodiment, the high-density portion 9a of the band layer 9 includes the band ply P1 of the band cord 14,
The example in which the number of band cords 14 per tire axial direction length is increased by increasing the number of P2... In this example, the high-density portion 9a is composed of three band plies P1 to P3,
The low-density portion 9b is composed of one band ply P1.

Such a band layer 9 has a thickness of, for example, 2 to 10
A small number of band cords 14, more preferably about 2 to 8, are spirally wound in parallel using a narrow and long band-like ply covered with topping rubber, and the tire of the rib-shaped portion 12 is used. It can be formed by reducing the winding pitch at a position radially inward and increasing the winding pitch at a position of the longitudinal groove 10 radially inward in the tire. At this time, if the winding is performed by one movement from one tread end E to the other tread end E, the productivity is good. However, the winding may be performed by moving between the tread ends E and E a plurality of times.

Further, the band layer 9 may be formed by coating a single band cord 14 with topping rubber and spirally winding the band cord outside the belt layer 7. In this case,
The band layer 9 makes the winding pitch of the band cords 14 uniform, and provides a difference in the number of superposed band plies P1, P2,... To provide a difference in the number of band cords 14 per length in the tire axial direction. Can be. In this case, fine adjustment of the number of arrangements and the pitch of the band cords 14 is particularly easy, and the molding accuracy of the band layer 9 can be particularly improved.

The band layer 9 includes the high-density portion 9a
, The depth from the tread surface 2a of the outermost belt ply P3 in the tire radial direction, in other words, the rubber thickness TH of the rib-like portion 12 is smaller than the depth GD of the vertical groove 10.

As described above, the high-density portion 9a of the band layer is
The rubber thickness TH of the rib-like portion 12 is increased by increasing the number of overlapping band plies to be greater than the number of overlapping band plies in the low-density portion 9b, while increasing the tread rigidity. Depth G without being restricted by
It can be set smaller than D. Alternatively, conversely, the groove depth GD can be set without being restricted by the thickness of the band layer 9 or the like.

For this reason, even during continuous high-speed running during a race, the heat dissipation of the tread rubber and the like of the rib-shaped portion 12 can be enhanced, and the rubber compounding and rubber tearing due to the boiling of the rubber compound due to overheating can be suitably prevented. This is preferable because the durability of the tread portion or the tread rubber can be improved.

The rubber thickness TH of the rib portion 12
It is particularly preferable to secure 3.0 mm or more in consideration of a practical wear amount and a continuable running distance while making the groove depth GD smaller than the groove depth GD of the vertical groove 10.

The number of band cords per tire axial length is, for example, 20 in the high-density portion 9a.
The density is preferably 30 to 30 / cm, more preferably 25 to 30 / cm, and in the low density portion 9b, 5 to 10 / cm, more preferably 5 to 8 / cm.

Although the embodiment of the present invention has been described in detail above, the vertical groove 10 may be formed by vulcanization molding using a groove molding projection provided on a die, and may be formed by positioning the low-density portion 9a of the band layer 9. By determining in advance at the time of tire molding, after the vulcanization molding as a slick tire having no groove, a vertical groove can be formed by a method other than vulcanization, for example, by pressing a cutting tool while rotating the tire. Thus, the flute 10
Is preferable in that the arrangement of the band cords 14 can be effectively prevented from being disturbed by the pressing force of the groove forming projections provided on the mold and the flow of rubber during vulcanization.

The racing tire having such a groove is used even in fine weather due to racing rules.
It can be used preferably even in rainy weather. In such a case, as shown in FIG. 3, the first horizontal groove 15 connecting between the vertical grooves 10 and the outermost vertical groove 10 to the tread end E side. A second lateral groove 16 that extends can be provided.

The first and second lateral grooves are inclined at a predetermined angle with respect to the circumferential direction of the tire. In the present embodiment, the first and second lateral grooves are arranged symmetrically with respect to the tire equator C, and have an inclination angle θ1.
Is set to 60 degrees and the inclination angle θ2 is set to 70 degrees.

[0033]

EXAMPLE A racing tire (size: 250 / 640R18 without lateral grooves) based on the specifications shown in FIG. 1 and Table 1.
Was prototyped, and a test run was conducted on the Suzuka Circuit (5.86 km per lap, weather: sunny) to check its performance. The test was carried out on a rear wheel of a rear-wheel drive type domestic passenger car modified for racing competition, and the lap time (average value of 3 laps) and the state of wear on the tread surface after running (5 grade evaluation, Good =
5) was evaluated. A test was also performed on a tire (conventional example) having a conventional band structure in which the band cords were uniformly spirally wound so that the number per band length in the tire axial direction was substantially the same (20 lines / cm). . Table 1 shows the test results.

[0034]

[Table 1]

As a result of the test, it was confirmed that the tires of the examples, particularly the examples 3 and 4, had a significantly improved lap time and good wear resistance.

Next, in rainy weather, the conventional example and the fourth embodiment were used.
As shown in FIG. 3, a test run was performed on the Fuji Speedway with both the tires having and not having the lateral grooves, and the lap time (average value after three laps) and the wear state (5 Grade evaluation, good = 5) was evaluated. Table 2 shows the test results.

[0037]

[Table 2]

As a result of the test, it was confirmed that the tire of Example 3 had improved lap time and good wear resistance even in rainy weather.

[0039]

As described above, according to the first aspect of the present invention, the band layer having a large number of band cords per length in the tire axial direction is provided inside the rib-like portion of the tread surface in the tire radial direction. By providing the high-density portion, it is possible to increase the rigidity of the rib-shaped portion and prevent a decrease in cornering power. Further, the high-density portion can suppress the lifting of the belt layer due to a large centrifugal force acting on this portion, and can improve the high-speed durability of the tire.

According to the second and third aspects of the present invention, the high-density portion of the band layer is formed by increasing the number of band plies, thereby increasing the tread rigidity and reducing the rubber thickness of the rib-shaped portion by the longitudinal groove. Without being restricted by the groove depth of the vertical groove. Therefore, even during continuous high-speed running during a race, it is possible to enhance the heat dissipation of the tread rubber in the rib-shaped portion, and it is possible to suitably prevent rubber rubbing due to boiling of the rubber compound due to overheating and rubber tearing. Thus, the durability of the tread portion or the tread rubber can be improved.

[Brief description of the drawings]

FIG. 1 is a meridional section of a right half molecule of a tire showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view of the vicinity of the vertical groove.

FIG. 3 is a plan view of a tread pattern provided with a lateral groove.

[Explanation of symbols]

 Reference Signs List 2 tread portion 2a tread surface 3 sidewall portion 4 bead portion 5 bead core 6 carcass ply inside carcass 6A carcass ply outside 6B 7 belt layer 9 band layer 9a high density portion 9b low density portion 14 band cord

Claims (4)

[Claims] 1. A carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, and a belt cord disposed inside the tread portion and radially outside of the carcass and having a belt cord of 10 to 45 degrees with respect to the tire equator C. A pneumatic tire comprising a belt layer arranged at an angle and a band layer arranged radially outside of the belt layer and having band cords arranged substantially in a tire circumferential direction, wherein a tire is provided on a tread surface. A small number of vertical grooves extending in the circumferential direction are provided, and rib-like portions are arranged in the tire axial direction between the vertical grooves or between the vertical grooves and the tread ends. A high-density portion located radially inward in the tire radial direction and having a large number of band cords per tire axial length; and the band located radially inward of the longitudinal groove in the tire radial direction. A pneumatic tire characterized by number of over soil and a small low-density portion than the high-density portion. 2. The high-density portion increases the number of band cords per length in the tire axial direction by increasing the number of overlapping band plies of the band cord than the low-density portion. 2. The pneumatic tire according to claim 1, wherein a depth of the outermost belt ply in the tire radial direction from a tread surface is smaller than a depth of the vertical groove. 3. The high-density part has three band plies, the low-density part has one band ply, and the high-density part has a radially outermost band ply. The pneumatic tire according to claim 2, wherein the depth from the tread surface is smaller than the groove depth of the vertical groove and 3.0 mm or more. 4. The pneumatic tire according to claim 1, wherein the band layer is formed by spirally winding a band cord substantially in a tire circumferential direction. .