JP2000177308A - Tubeless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To greatly reduce the weight and improve the productivity while keeping control stability and comfortableness balanced and maintaining actual performance. SOLUTION: A topping rubber for a carcass ply 6A has an inside topping portion, defining a tire cavity face S, only formed of butyl based rubber. The height (ha) of a bead apex is 10-20 mm and the turnaround height (hb) of a ply turnaround portion 6b is 0.3-0.7 time the sectional height H of a tire. The ply turnaround portion 6b has a proximity area 15 formed in proximity to a ply mainbody portion 6a outward of the outward end 8t of an apex rubber 8. A ply turnaround portion 15 is curved at a radius of curvature R of 5-15 mm in proximity to the outward end 8t. A rubber thickness Tb between the ply mainbody portion 6a and the ply turnaround portion 6b in the proximity area 15 is 0.3-0.8 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tubeless tire capable of significantly reducing weight and improving productivity while maintaining a balance between steering stability and ride comfort.

[0002]

2. Description of the Related Art In recent years, with the recent strong demand for resource saving and low fuel consumption, further reduction in the weight of tubeless tires has been desired. Figure 6 shows a typical tubeless tire.
As shown in FIG. 1, an inner liner b made of butyl rubber having excellent air impermeability is adhered to the inner surface of the carcass a facing the tire cavity in order to prevent leakage of the internal pressure air. Attempts have been made to reduce the tire weight by omitting the liner b. In the drawing, reference numeral a1 denotes a ply folded portion, and c denotes a bead apex rubber.

For example, JP-A-8-113007 discloses that
In the carcass ply, it has been proposed to form only the topping rubber on the inner side of the tire out of the topping rubber covering both sides of the carcass cord with butyl rubber. In such a tubeless tire, since the carcass ply also has the function of the inner liner, the conventional inner liner can be eliminated, and reduction in weight and improvement in productivity can be achieved.

[0004]

However, butyl rubber has low rebound resilience and is inferior in characteristics as a rubber elastic body to diene rubber which is generally used as a topping rubber. Therefore, this butyl rubber was used as a topping rubber. In such a case, there arises a problem of deteriorating the performance of the actual vehicle such as deteriorating the balance between the steering stability and the riding comfort.

The present invention has been devised in view of the above problems. In a tire in which only the inner topping portion of the carcass ply is formed of butyl rubber, the height of the bead apex rubber is 10 to 20 mm. The balance between steering stability and ride comfort is maintained on the basis of setting the carcass ply main body and the folded end close to the outside of the outer end of the bead apex rubber. It is an object of the present invention to provide a tubeless tire that can significantly improve weight reduction and productivity while maintaining actual vehicle performance.

[0006]

According to a first aspect of the present invention, there is provided a tubeless tire comprising: a ply body portion extending from a tread portion to a sidewall portion to a bead core of a bead portion; A carcass ply of a radial arrangement having a ply folded portion integrally formed with a ply turn-back portion which is continuous with the ply portion and turned from the inside to the outside in the tire axial direction around the bead core, and wherein the ply body portion forms a tire cavity surface, And a bead apex rubber extending in a radially outward direction from the bead core in a tire radial direction passing between a ply body portion and a ply turn-over portion of the carcass, wherein the carcass ply is a cord in which carcass cords are arranged in parallel with each other. An array body and a topping rubber covering both sides of the code array body; The rubber is a butyl rubber containing only 10 parts by weight of butyl rubber or a derivative thereof in 100 parts by weight of a rubber base material, and only an inner topping portion provided in the range forming the ply body and forming the inner surface of the tire. The ply turn-up portion is formed of rubber, and the ply turn-up portion has a proximity area in which the ply turn-up portion comes close to the ply body portion by projecting outward from a radially outer end of the apex rubber. In a state where the rim is assembled to the rim and filled with the normal internal pressure, the ply folded portion is curved with a radius of curvature of 5 to 15 mm near a radially outer end of the apex rubber, while the ply folded portion is The turning height hb from the bead base line at the radially outer end is defined as 0.3 to less than the tire section height H.
0.7 times, and the bead apex height ha from the bead base line at the radially outer end of the bead apex rubber to 10 to 20 mm, the carcass cord of the ply body portion and the tire cavity surface The rubber thickness Ta between the cords is 0.3 to 0.8 mm, and the inter-cord rubber thickness Tb between the carcass cord of the adjacent ply body and the carcass cord of the ply turn-back portion in the adjacent area.
Is 0.3 to 0.8 mm.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tubeless tire 1 of the present invention (hereinafter, sometimes simply referred to as “tire 1”).
Illustrates a case where the tire 1 is formed as a radial tire for a passenger car. In the state of FIG.
5 shows a meridional section in a no-load state, which is mounted on a, and filled with a normal internal pressure.

[0008] In this specification, the "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based.
Standard rim for ATMA, "Design R for TRA
im "or" Measuring Rim "in the case of ETRTO." Normal internal pressure "is the air pressure that is defined for each tire in the standard system including the standard on which the tire is based. If the highest air pressure,
For TRA, see the table "TIRE LOAD LIMITS AT VARIOUSCOLD
The maximum value described in "INFLATION PRESSURES" is "INFLATIONPRESSURE" for ETRTO, but is 180 kPa when the tire is for a passenger car.

In FIG. 1, the tire 1 has a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a pair of beads located at an inner end of each sidewall portion 3. And part 4.

The tire 1 has a carcass 6 extending over the bead portions 4, and a carcass 6 disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2.
A belt layer 7 composed of a plurality of steel belt plies 7A and 7B, and a bead apex rubber 8 made of hard rubber and extending outward from the bead core 5 in the tire radial direction.

The carcass 6 includes a ply body 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3, and a ply body portion 6a extending from the ply body portion 6a and extending around the bead core 5 from the inside in the tire axial direction. It is composed of one carcass ply 6A integrally having a ply folded portion 6b folded outward.

The carcass ply 6A forms a tire bore surface S by the ply body 6a. That is, the tire 1 of the present application does not hold an inner liner that has been generally used in the past, and the ply main body 6a itself of the carcass ply 6A forms the tire cavity surface S.

As shown in FIG. 2, the carcass ply 6A comprises a code array 10 in which a plurality of carcass cords 10A are arranged, and a topping rubber 11 covering both sides of the code array 10. You. As the carcass cord 10A, an organic fiber cord such as nylon, rayon, polyester, aromatic polyamide, or vinylon is preferable. Further, the tire 1 of the present example has a radial structure in which the carcass cords 10A are arranged at an angle of 75 to 90 degrees with respect to the tire equator C.

The topping rubber 11 is provided only in the area where the ply main body 6a is formed, and only the inner topping 11i forming the tire cavity surface S is covered with the rubber base material 10a.
It is made of butyl rubber containing 10 parts by weight or more of butyl rubber or its derivative in 0 parts by weight. Butyl rubber (IIR) is a copolymer of isobutylene and a small amount of isoprene. Derivatives thereof include, for example, chlorinated butyl rubber, brominated butyl rubber, and the like, which are obtained by reacting the butyl rubber with chlorine, bromine, or the like to improve moldability. Halogenated butyl rubber.

The butyl rubber contains natural rubber (NR) and / or butadiene rubber (B
R) and a diene rubber such as styrene butadiene rubber (SBR). In addition, a filler such as a reinforcing agent such as carbon black, a vulcanizing agent, a vulcanization accelerator, and a softening agent can be added to the rubber base material in the same manner as a general topping rubber.

On the other hand, a rubber portion other than the inner topping portion 11i of the topping rubber, in this example, the outer topping portion 11o, is, as in the prior art, contained in 100 parts by weight of the rubber substrate.
90 parts by weight or more, preferably 10 parts by weight,
A non-butyl rubber containing 0 parts by weight is used.

As described above, the inner topping portion 11i made of butyl rubber, which is hardly permeable to air, surrounds the tire cavity, so that the carcass ply 6A can have the function of a conventional inner liner. The conventional inner liner provided separately can be eliminated, and the weight of the tire is reduced.

Here, in order for the carcass ply 6A to exhibit sufficient internal pressure holding performance, the content of butyl rubber or a derivative thereof in the butyl rubber is required to be 10 parts by weight or more as described above. It is preferable that the content be 30 parts by weight or more in order to further enhance the air impermeability.

Also, as shown in FIG.
In 1i, the rubber thickness Ta from the carcass cord 10A to the tire lumen surface S needs to be in the range of 0.3 to 0.8 mm. This rubber thickness Ta is 0.3mm
If it is less than the above range, it becomes difficult to maintain the same level of internal pressure holding performance as that of a conventional tire. The rubber thickness Ta is 0.8mm
In addition to the above, in addition to causing unnecessary increase in tire weight, it is difficult to sufficiently improve the balance between steering stability and ride comfort because butyl rubber has poor rubber elastic properties as described above. Become.

As shown in FIG. 3A, the critical surface E between the inner topping portion 11i and the outer topping portion 11o passes through the code array 10 and is formed, for example, on the center line N of the carcass cord 10A. In addition, as shown in FIG. 7B, it may be formed so as to be deviated to the outside of the tire from the center line N or to the inside of the tire as shown in FIG. From the viewpoint of the balance between the steering stability and the ride comfort or the adhesiveness to the carcass cord 10A, the upper limit of the rubber thickness T from the tire lumen surface S to the critical surface E of the inner topping portion 11i is: When the diameter of the carcass cord is D, it is preferable to be Ti + 0.5D or less and 1.5 mm or less.

In the present application, in the tire having such a carcass ply 6A, the height ha of the bead apex rubber 8 is set to be extremely small, while the carcass ply 6A has a high turn-up folded structure, and The ply folded portion 6b and the ply main body 6a form a proximity region 15.

As a result, the influence of the butyl rubber is suppressed, the balance between steering stability and ride comfort is maintained, and the actual vehicle performance is maintained, while further reducing the weight and further improving the productivity.

More specifically, the bead apex rubber 8 has a tapered cross section passing between the ply body 6a and the folded portion 6b, and has a JISA hardness of 65-95 °, more preferably 70-90 °. Made of relatively hard rubber. The bead apex height ha of the outer end 8t of the bead apex rubber 8 from the bead base line BL is set in a range of 10 to 20 mm.
The “bead base line BL” is defined as a tire axial line passing through a rim diameter position defined by a standard based on the tire.

Further, the carcass 6 has a high turn-up folded structure in which the ply folded portion 6b protrudes outward from the outer end 8t of the bead apex rubber 8, and the carcass 6 has a radially outer side of the outer end 8t. In addition, an adjacent area 15 in which the ply turn-up portion 6b and the ply body portion 6a are close to each other is formed.

With such a structure, the height a of the bead apex is substantially the same as the height Jf of the flange Jf of the regular rim J. Therefore, the rubber volume of the bead apex rubber 8 is greatly reduced, and the weight is reduced. Further promoted.

In the ply turn-up portion 6b, the inner topping portion 11i of butyl rubber having poor adhesive strength is in direct contact with the sidewall rubber 3G and the chafer rubber 4G for preventing rim displacement. Separation is likely to occur starting from the outer end 6t. However, in the present application, almost all of the ply turn-up portion 6b that is radially outside the flange Jf is
To approach the neutral line (neutral axis) side of the deformation,
The stress and the amount of deformation acting on the ply folded portion 6b are greatly reduced, and the separation is effectively suppressed. In particular, in the proximity area 15, the ply body 6
a and the ply folded portion 6a are substantially integrated with each other and restrained from each other, so that local movement at the outer end 6t can also be suppressed.

Further, the bead apex height ha
The decrease in lateral rigidity caused by reducing the size of the ply body is caused by the substantially integrated ply body 6a and the ply turn-up portion 6a, the use of a high turn-up fold structure, and the use of butyl rubber in the inner topping portion 11i. Thus, actual vehicle performance, in particular, steering stability and ride comfort can be improved in a well-balanced manner.

Moreover, the bead apex height ha
As shown in FIG. 5, conventionally, as shown in FIG. 5, conventionally, in forming a green tire, when the carcass ply 6 </ b> A is folded back, a step K of previously bending the tip of the bead apex rubber 8 along the former F is necessary. However, when the height a of the bead apex is in the range of 10 to 20 mm as in the present application, the bending step K becomes unnecessary, and further improvement in productivity can be achieved together with elimination of the inner liner.

Here, the folded height hb of the outer end 6t of the ply folded portion 6a from the bead base line BL.
Is 0.3 to 0.7 times the tire section height H. As shown in FIG. 4, the rubber thickness Tb between cords between the carcass cord 10A of the adjacent ply main body 6a and the carcass cord 10A of the ply turn-up portion 6b in the adjacent area 15 is 0.3 to 0.8 mm. It is.

If the turning height hb is less than 0.3 × H, the range of the proximity area 15 becomes too small, lateral rigidity cannot be sufficiently secured, and steering stability is significantly reduced.
Beyond this, the lateral stiffness increases with the longitudinal stiffness and the ride comfort is reduced, for example, greatly impairing the balance between steering stability and ride comfort. Therefore, the turning height hb is preferably 0.40 × H to 0.55 × H. If the inter-cord rubber thickness Tb is less than 0.3 mm, the carcass cords 10A and 10A may come into contact with each other in the proximity area 15 and cause damage. In addition, the effect of suppressing separation is impaired, and the merit of weight reduction such as unnecessarily increasing the weight is impeded.

The bead apex height ha is 10
If it is less than mm, tire production becomes difficult. Conversely 20mm
When the value exceeds the above, the stress acting on the ply turn-up portion 6b increases, so that the separation cannot be sufficiently suppressed, and the bending step K (shown in FIG. 5) of the bead apex rubber 8 cannot be eliminated. Therefore, the bead apex height ha is preferably 15 mm ± 2 mm.
Range.

On the other hand, when the bead apex height ha is reduced to the range of 10 to 20 mm, the ply turn-up portion 6b is sharply bent in the vicinity of the outer end 8t, which may deteriorate durability. In addition, during vulcanization molding, there is a danger that air may accumulate at the outer end 8t. For this purpose, the ply turn-up portion 6b needs to be curved with a radius of curvature R of 5 to 15 mm near the outer end 8t. If the radius of curvature R is less than 5 mm, the durability deteriorates. If the radius of curvature R is more than 15 mm, it is difficult to regulate the bead apex height ha to 20 mm or less. Therefore, the radius of curvature R is preferably 10 mm ± 2.
mm.

Although the present embodiment has been described in detail, such tires are not limited to those for passenger cars and can be preferably formed for motorcycles, small trucks, and the like.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Tire size is 175 / 70R13 and FIG.
A prototype of a tubeless tire for a passenger car having the structure shown in Table 1 was manufactured based on the specifications in Table 1, and the tire weight, air permeability, productivity, durability, and actual vehicle performance (steering stability and ride comfort) of each sample tire were tested. Tested. For comparison, a tire having an inner liner was tested as a conventional example, and performance was compared. The test conditions are as follows.

(1) Tire Weight The weight per tire was measured, and was shown as an index with the conventional example being 100. The smaller the value, the lighter.

(2) Air Permeation Resistance The tire is assembled on a specified rim (5JJ × 13), filled with a specified internal pressure (200 kPa), and allowed to stand in an oven at 80 ° C. for 15 days. The rate of decrease was measured, and the reciprocal thereof was indicated by an index with the conventional example being 100. The larger the value, the better the air permeation resistance.

(3) Productivity The process time required to form a green tire was indicated by an index with the conventional example being 100. The smaller the value, the better the productivity.

(4) Actual Car Performance Tires are assembled on a specified rim (5JJ × 13) and a passenger car (1600 cc / F) is set at a specified internal pressure (200 kPa).
F) was mounted on all wheels, and ran on the test course. At this time, characteristics relating to steering wheel responsiveness, rigidity, grip and the like were indicated as steering stability by a ten-point evaluation by a sensory evaluation by a driver. The larger the value, the better the steering stability. On a step road, a Beljaso road (cobblestone road surface), a Bitzman road (a road surface covered with pebbles) and the like on a test course, a sensation of ruggedness, pushing up, and damping were evaluated as a ride comfort, and a ten-point evaluation was given by a sensory evaluation of a driver. . The larger the value, the better the ride comfort.

Table 1 shows the results of the test, and Table 2 shows rubber compounding examples of the topping rubber of the carcass ply.

[0040]

[Table 1]

[0041]

[Table 2]

As a result of the test, the tire of Example 1 can exhibit the same air permeation resistance as the conventional example, and eliminates the inner liner provided separately from the conventional carcass.
And, by reducing the size of the bead apex rubber, weight reduction and improvement in productivity can be largely achieved. Furthermore, the use of butyl rubber as the topping rubber, the miniaturization of the bead apex rubber, and the adoption of a high turn-up structure are organically combined, and can improve the actual vehicle performance, especially the steering stability and ride comfort in a well-balanced manner. .

If the bead apex rubber is as high as the conventional example as in Comparative Example 1, the influence of the butyl rubber in the topping rubber acts greatly, and the steering stability is improved, but the riding comfort is improved. The balance between the two is greatly impaired.

Conversely, when the bead apex rubber in the tire with the inner liner is reduced in size as in Comparative Example 2, the lateral stiffness is reduced along with the vertical stiffness, so that the riding comfort is improved, but the steering stability is improved. The balance between the two is greatly impaired.

[0045]

As described above, according to the present invention, in a tire using butyl rubber as a topping rubber, the height of the bead apex is set to an extremely small value of 10 to 20 mm, and a carcass is provided outside the bead apex rubber. Since the area between the ply body and the end of the ply is formed close to each other, the balance between steering stability and ride comfort is maintained and actual vehicle performance is maintained, while weight reduction and productivity improvement are greatly improved. Can.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is a perspective view showing a structure of a carcass ply.

FIGS. 3A to 3C are cross-sectional views showing a state of a critical surface of an inner topping portion in the topping rubber.

FIG. 4 is a cross-sectional view illustrating the thickness of the rubber between cords.

FIG. 5 is a diagram illustrating a process of forming a raw tire, which is one of the effects of the present invention.

FIG. 6 is a cross-sectional view illustrating a conventional tire.

[Description of Signs] 2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 6A Carcass ply 6a Ply main body portion 6b Ply turnback portion 8 Bead apex rubber 10 Cord array 10A Carcass cord 11 Topping rubber 11i Inner topping portion 15 Proximity Area, BL Bead Baseline J Regular Rim S Tire Lumen Surface

Claims (1)

[Claims] 1. A ply body portion extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a ply turn-up portion connected to the ply body portion and turned around from the bead core to an inner side and an outer side in the tire axial direction. A carcass ply consisting of one carcass ply in a radial array having a carcass ply formed by the ply body portion and a tire cavity surface, and a tire radius from the bead core passing between the ply body portion of the carcass and the ply turnover portion. The carcass ply comprises a cord array in which carcass cords are arranged in parallel with each other and a topping rubber covering both sides of the cord array, and the topping rubber. Is attached to the area forming the ply body and forms the tire cavity surface. Only the side topping portion is formed of butyl rubber containing 10 parts by weight or more of butyl rubber or a derivative thereof in 100 parts by weight of the rubber base material, and the ply turn-up portion is more than the radially outer end of the apex rubber. By projecting outward, the ply turn-up portion has a proximity area close to the ply body portion, and in a state where the tire is rim-assembled to the normal rim and filled with the normal internal pressure, the ply turn-up portion is the apex rubber. In the vicinity of the radially outer end of the ply, it is curved with a radius of curvature of 5 to 15 mm. .3
~ 0.7 times, and while the bead apex height ha from the bead base line at the radially outer end of the bead apex rubber is 10 to 20 mm, the carcass cord and tire bore surface of the ply body portion Is between 0.3 and 0.8 mm, and the inter-cord rubber thickness Tb between the carcass cord of the adjacent ply body and the carcass cord of the ply turn-back portion is 0.3 to 0.8 mm. A tubeless tire having a diameter of about 0.8 mm.