JP4326416B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire having improved steering stability while maintaining durability such as crack growth resistance in a sidewall portion.

  With recent improvements in vehicle performance and output, further improvements in handling stability are required for pneumatic radial tires. Therefore, it has been proposed to use a rubber material having a high modulus for the sidewall rubber to increase the sidewall rigidity.

  However, when the modulus of the side wall rubber is simply increased, the crack growth resistance required for the side wall rubber is lowered, resulting in a problem that the durability of the tire is impaired.

  Therefore, the present invention is based on the fact that the sidewall rubber has a two-layer structure of an inner layer portion and an outer layer portion, and the modulus ratio between the clinch rubber forming the bead outer shell and the inner layer portion and the outer layer portion is specified, and the sidewall rigidity is thereby determined. An object of the present invention is to provide a pneumatic radial tire that can be improved in a well-balanced manner and can improve steering stability while maintaining crack growth resistance in a sidewall portion.

JP 2003-31213 A

In order to achieve the above object, the invention of claim 1 of the present application is a pneumatic radial tire having a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion,
A sidewall rubber disposed on the outside of the carcass and forming the outer surface of the sidewall portion; and a clinching rubber for preventing a rim shift that forms an outer surface of the bead portion connected to an inner end of the sidewall rubber in the tire radial direction ; With
The sidewall rubber consists of an inner layer portion on the carcass side and an outer layer portion on the outer surface side ,
The inner end portion of the outer layer portion in the tire radial direction is connected to the clinch rubber, while the inner end portion of the inner layer portion in the tire radial direction is located on the outer side in the tire radial direction of the outer end of the clinch rubber in the tire radial direction. To separate the clinch rubber, and the 100% modulus MB of the inner layer portion is larger than 1.0 times and smaller than 1.5 times the 100% modulus MA of the outer layer portion,
Moreover, the 100% modulus MC of the clinch rubber is 1.5 times or more and 4.0 times or less of the 100% modulus MA of the outer layer part,
The thickness TB of the inner layer portion is characterized by being 0.3 to 0.8 times the total thickness T0 of the sidewall rubber.

  In the invention of claim 2, the clinch rubber is characterized in that the height HC in the radial direction from the bead base line at the upper end thereof is 20% or more and 60% or less of the tire cross-section height H0.

In the invention of claim 3, the height HB from the bead base line of the inner end in the radial direction of the inner layer portion is 70% or less of the tire cross-section height H0. Further, in the invention of claim 4, the height HB Is 60% or less of the tire cross-section height H0.

  In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in a normal internal pressure state in which a normal rim is assembled and a normal internal pressure is filled. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it means “INFLATION PRESSURE”, but in the case of passenger car tires, it is 180 kPa.

  Since the present invention is configured as described above, the sidewall rigidity can be improved in a well-balanced manner, and the steering stability can be improved while maintaining the crack growth resistance in the sidewall portion.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a case where the pneumatic radial tire of the present invention (excluding the configuration of an inner layer portion 13 of a side wall rubber 10 described later) is a passenger tire.

  1 and 2, a pneumatic radial tire 1 (hereinafter referred to as tire 1) includes a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inner side of the tread portion 2, A belt layer 7 disposed on the radially outer side of the carcass 6.

  The carcass 6 is formed of one or more radial structures in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire circumferential direction, in this example, one carcass ply 6A. As the carcass cord, an organic fiber cord such as polyester, nylon, or rayon is suitable, but a metal cord such as a steel cord can also be adopted if necessary.

  The carcass ply 6A includes a series of ply turn-up portions 6b on both sides of the toroid-like ply main body portion 6a straddling the bead cores 5 and 5 so that the bead core 5 is turned back from the inner side to the outer side in the tire axial direction. Further, a bead apex rubber 8 for bead reinforcement extending from the bead core 5 to the outer side in the tire radial direction is disposed between the ply main body portion 6a and the ply turn-up portion 6b. In this example, the ply turn-up portion 6b is exemplified by a low turn-up (LTU) that terminates at a lower position than the outer end of the bead apex rubber 8, but the outer end of the bead apex rubber 8 is A high turn-up (HTU) structure that terminates outward in the radial direction may be used.

  The belt layer 7 is formed by two or more belt plies 7A and 7B in which high-strength belt cords such as steel cords are arranged at, for example, about 10 to 35 ° with respect to the tire circumferential direction. The Each belt ply 7A, 7B enhances belt rigidity by crossing the belt cords between the plies, and reinforces substantially the entire width of the tread portion 2 with a tagging effect. In addition, a band layer 9 in which band cords of organic fibers such as nylon are arranged at an angle of 5 degrees or less with respect to the circumferential direction is provided on the outer side in the radial direction of the belt layer 7 for the purpose of improving high-speed durability. be able to.

  Next, in the tire 1, as is well known, the side wall rubber 10 disposed outside the carcass 6 and forming the outer side surface 3 </ b> S of the side wall part 3, and the bead part 4 connected to the lower end of the side wall rubber 10. The rim slip preventing clinch rubber 11 forming the outer side surface 4S of the rim is disposed.

  Here, the clinch rubber 11 is made of a relatively hard rubber excellent in wear resistance, rises from the bead heel portion 4e, and is exposed to the outer surface 4S at least in a region in contact with the rim flange. This prevents bead damage due to rim displacement. In this example, the case where the bottom surface of the bead is formed by the chafer 15 made of canvas cloth, rubber sheet, or the like is illustrated. However, instead of the chafer 15, the base portion extending along the bottom surface of the bead to the clinch rubber 11 ( (Not shown) may be extended.

  The radial height HC from the bead base line BL at the upper end of the clinch rubber 11 is in the range of 20% to 60% of the tire cross-section height H0. In this example, the height of the bead apex rubber 8 is The preferable case which made it larger than H1 is illustrated.

  The sidewall rubber 10 extends radially outward from an inner end portion 10i connected to the clinch rubber 11, and the outer end portion 10o in this example includes the outer end portion 7E of the belt layer 7, the carcass 6 and the like. It is pinched | interposed into the gap | interval part P, and it terminates.

In this embodiment, the sidewall rubber 10 is formed in a two-layer structure including an outer layer portion 12 on the outer side surface 3S side and an inner layer portion 13 on the carcass 6 side made of rubber having higher elasticity than the outer layer portion 12. ing. The inner end portion of the outer layer portion 12 in the tire radial direction is connected to the clinch rubber 11. Further, the 100% modulus MB of the inner layer portion 13 is set to a range larger than 1.0 times and smaller than 1.5 times the 100% modulus MA of the outer layer portion 12, and the 100% modulus MC of the clinch rubber 11. Is set in the range of 1.5 times to 4.0 times the 100% modulus MA of the outer layer portion 12.

By comprising in this way, sidewall rigidity can be improved with sufficient balance and steering stability can be improved, ensuring the outstanding riding comfort . The inner layer portion 13 can also function as a protector for preventing cut flaws received on the sidewall portion 3 from reaching the carcass 6, and for this purpose, it is preferably formed over the entire region.

  Further, the outer layer portion 12 is formed of a low elastic rubber like the conventional sidewall rubber, so that it can be flexibly flexed following the tire deformation, and the occurrence of cracks on the outer surface 3S and the growth of cracks can be prevented. Can be suppressed. In this example, the outer layer portion 12 is interposed in the gap portion P between the belt layer 7 and the carcass 6 to relieve stress concentration at the outer end of the inner belt ply 7A. Damage can also be suppressed.

In order to fully exert such effects, as described above, 100% modulus MA, MB, MC is
1.0MA <MB <1.5MA
1.5MA ≦ MC ≦ 4.0MA
Is necessary. If MB is 1.0 MA or less, the inner layer portion 13 has low elasticity and the steering stability cannot be maintained. When the MB is 1.5 MA or more, the MC is less than 1.5 MA, and the MC is greater than 4.0 MA, the rigidity balance is lost, and excellent handling stability and ride comfort are ensured. I can't do that. Therefore, the lower limit value of MB is preferably 1.05 MA or more, and the upper limit value is preferably 1.45 MA or less. Further, the lower limit value of MC is preferably 1.5 MA or more, and the upper limit value is preferably 4.0 MA or less. At this time, the MA preferably has a range of 1.0 MPa to 4.0 MPa in order to exhibit crack growth resistance and the like. The 100% modulus MA, MB, and MC indicate the tensile stress at the time of 100% elongation of the test piece measured according to “How to obtain vulcanized rubber and thermoplastic rubber-tensile characteristics” according to JIS K6251.

  In order to achieve the above-described effects, it is necessary that the thickness TB of the inner layer portion 13 is not less than 0.3 times and not more than 0.8 times the total thickness T0 of the sidewall rubber 10. If it is less than 0.3 times, a satisfactory steering stability improvement effect such as insufficient reinforcement effect by the inner layer portion 13 cannot be obtained, and conversely if it exceeds 0.8 times, ride comfort is reduced. .

  The thickness TB of the inner layer portion 13 is gradually reduced in a tapered shape at the radially outer end portion and the inner end portion. Therefore, in the intermediate region of the inner layer portion 13 excluding the range of 10% of the length of the inner layer portion 13 (the length along the curved shape of the inner layer portion 13) from the outer end and inner end of the inner layer portion 13, respectively. The thickness TB is 0.3 to 0.8 times the total thickness T0.

FIG. 3 shows a sidewall rubber 10 according to an embodiment of the present invention. In FIG. 3, the inner end portion in the tire radial direction of the inner layer portion 13 is separated from the clinch rubber 11 by being positioned on the outer side in the tire radial direction with respect to the outer end in the tire radial direction of the clinch rubber 11. Further, by setting the height HB from the bead base line BL at the radially inner end of the inner layer portion 13 to 70% or less, preferably 60% or less, more preferably 30% or less of the tire cross-section height H0, At least the rigidity of the sidewall upper region 3U radially outward from the tire maximum width position M is increased, and the steering stability is improved. In this case, riding comfort can be improved by the separated portion Q between the inner layer portion 13 and the clinch rubber 11.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A passenger car tire having a tire size of 195 / 65R15 having the internal structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the handling stability and riding comfort of the sample tire were tested. The specifications are the same except for those in Table 1. Table 2 shows the rubber composition of the inner layer portion, the outer surface, and the clinch rubber. The inner layer portion and the outer surface have different values of 100% modulus MA and MB depending on the amount of carbon black (N550). .

(1) Steering stability:
A sample tire is mounted on four wheels of a passenger car (2000 cc) with a rim (15 × 6JJ) and internal pressure (210 kPa). The steering stability characteristics concerning the grip and the like were evaluated by index display with the conventional example 1 as 100 by sensory evaluation of the driver. The larger the value, the better the steering stability.

(2) Ride comfort:
In the above test running, the ride comfort was evaluated by index display with the conventional example 1 being 100 by sensory evaluation of the driver. The larger the value, the better the ride comfort.

表の如く実施例品は、優れた乗り心地性を維持しながら、操縦安定性を向上しうるのが確認できる。

As shown in the table, it can be confirmed that the example products can improve steering stability while maintaining excellent ride comfort.

It is sectional drawing which shows one Example of the pneumatic tire (however, except the structure of sidewall rubber) of this invention. It is sectional drawing which expands and shows the bead part. It is sectional drawing which shows embodiment of sidewall rubber .

Explanation of symbols

2 Tread part 3 Side wall part 3S Outer side face of side wall part 4 Bead part 4S Outer side face of bead part 5 Bead core 6 Carcass 10 Side wall rubber 11 Clinch rubber 12 Outer layer part 13 Inner layer part

Claims (4)

A pneumatic radial tire having a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion,
A sidewall rubber disposed on the outside of the carcass and forming the outer surface of the sidewall portion; and a clinching rubber for preventing a rim shift that forms an outer surface of the bead portion connected to an inner end of the sidewall rubber in the tire radial direction ; With
The sidewall rubber consists of an inner layer portion on the carcass side and an outer layer portion on the outer surface side ,
The inner end portion of the outer layer portion in the tire radial direction is connected to the clinch rubber, while the inner end portion of the inner layer portion in the tire radial direction is located on the outer side in the tire radial direction of the outer end of the clinch rubber in the tire radial direction. To 100% modulus MB of the inner layer portion is larger than 1.0 times and smaller than 1.5 times the 100% modulus MA of the outer layer portion,
Moreover, the 100% modulus MC of the clinch rubber is 1.5 times or more and 4.0 times or less of the 100% modulus MA of the outer layer part,
A pneumatic radial tire characterized in that the thickness TB of the inner layer portion is 0.3 times or more and 0.8 times or less of the total thickness T0 of the sidewall rubber.   2. The pneumatic radial tire according to claim 1, wherein the clinch rubber has a radial height HC from a bead base line at an upper end of 20 to 60% of a tire cross-section height H0. The pneumatic radial tire according to claim 1 or 2 , wherein a height HB from a bead base line at a radially inner end of the inner layer portion is 70% or less of a tire cross-sectional height H0 . The pneumatic radial tire according to claim 1 or 2 , wherein a height HB from a bead base line at a radially inner end of the inner layer portion is 60% or less of a tire cross-sectional height H0 .

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