JPH0585364B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pneumatic radial tire mainly for passenger cars, which has excellent durability and excellent ride comfort, handling stability, and high speed. By appropriately arranging the carbon fiber reinforcing layer made of cords to reinforce the bead, it is possible to keep the force applied to the carbon fiber reinforcing layer relatively on the tensile side, making it durable. The present invention relates to a pneumatic radial tire having a bead structure that significantly improves performance and improves handling stability and high-speed durability without impairing riding comfort.

[Prior art]

In recent years, with the improvement of expressway networks and the improvement of the performance of passenger cars, the performance requirements for tires have become more sophisticated and diversified without stopping.

For example, there is a demand for HR tires that can run at higher speeds than SR tires, a demand for VR tires that can run even faster, and a demand for flat tires that have better handling stability.

However, from the vehicle's perspective, due to the tire housing, it is possible to drive at high speeds with the same flatness as before.
Moreover, there is also a demand for tires with excellent handling stability.

Therefore, conventional tire manufacturers have attempted to address various improvement requests by adding a reinforcing sheet made of organic fiber cords such as nylon to the tire bead, called a bead reinforcing layer. Merely adding a reinforcing layer made of the same material as conventional carcass materials to the bead portion of the tire was insufficient due to its low rigidity.

Later, in response to the fact that materials similar to carcass materials were insufficient in rigidity, a bead reinforcement layer made of steel cord with sufficient tensile and bending rigidity was proposed, improving high-speed performance and handling stability. However, the deterioration in riding comfort caused by the high bending rigidity of the steel cord was intolerable, and the weight increased, so further improvements were necessary.

Under the above circumstances, carbon fiber cords, which have significantly higher tensile rigidity than organic fibers and significantly lower bending rigidity than steel cords, have been attracting attention.

This carbon fiber has sufficient tensile rigidity compared to conventional organic fibers, and has significantly lower bending rigidity than steel cord, so it can reinforce the bead without impairing riding comfort. Carbon fiber also has the advantage of being much lighter than steel cord and comparable in weight to organic fiber.

On the other hand, reinforcing the area around the bead is to suppress the movement of the bead and increase the rigidity of the area around the bead.By this, for example, when driving at high speed, the movement around the bead can be suppressed and the standing By eliminating the generation of waves and increasing lateral rigidity, it is possible to improve the steering stability of the vehicle.

Therefore, FIGS. 3 and 4 show conventional pneumatic radial tires, in which a carbon fiber reinforcing layer 8 is provided along the lower bead filler 6 in the carcass layer 4 of the bead portion 1. In FIG. 3, the carbon fiber reinforcing layer 8 is provided inside the lower bead filler 6, and in FIG. 4, it is provided outside the lower bead filler 6.

In addition, in the above figure, 1A is a bead wire, 2 is a side part, and 9 is a rim flange.

As described above, even when the bead portion 1 is reinforced with the carbon fiber reinforcing layer 8, in the same arrangement as the conventional reinforcing layer as shown in FIGS. 3 and 4, the carbon fiber has extremely high tensile strength due to its crystal structure. Due to its characteristics of being strong but weak against compression, it had the disadvantage of being significantly inferior in durability.

Therefore, when a carbon fiber reinforcing layer is placed on a tire in the same way as the conventional bead reinforcing layer as shown in Fig. 4,
If the bead portion 1 is subjected to bending deformation using the rim flange 9 as a fulcrum, compression will be applied to the carbon fiber cord, which will reduce durability, which is not preferable.

In addition, when arranged as shown in Figure 3, the side part 2 of the tire undergoes bending deformation opposite to that of the bead part 1, with the vicinity of the tire's maximum width as a fulcrum, and for the same reason as the bead part 1, the durability is reduced. The disadvantage is that it reduces the

[Purpose of the invention]

Therefore, the present invention was made to eliminate the above-mentioned conventional drawbacks, and improves the durability of a pneumatic radial tire whose bead portion is reinforced with a carbon fiber reinforcing layer, and also improves maneuverability without impairing riding comfort. This provides a pneumatic radial tire with improved stability and high-speed durability.

[Structure of the invention]

That is, in the pneumatic radial tire of the present invention, the bead filler constituting the bead portion is divided into upper and lower parts, and carbon fibers made of carbon fiber cords are inserted into the bead portion so as to pass through at least the pinched area between the upper bead filler and the lower bead filler. A reinforcing layer is provided, and the carbon fiber cord is made of carbon fiber with a tensile strength of 100 Kg/mm ² or more and a tensile modulus of 5000 Kg/mm ² or more, and the 100% modulus of the coated rubber is 30
~70Kg/ ^cm2 , furthermore, the center point of the pinch area in the tire cross-sectional direction is set higher than the rim flange height and within 2.5 times the rim flange height, and the carbon fiber reinforcing layer is beaded from the pinch area. The part extending to the tread side is arranged along the carcass layer in the maximum tensile area on the inside of the tire cross section, and the part extending to the opposite tread part side is arranged along the carcass layer in the maximum tensile area on the outside of the tire cross section. The present invention is characterized in that the height of the tread portion side end of the carbon fiber reinforcing layer is lower than the maximum width position of the tire.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view of a main part of a pneumatic radial tire for a passenger car according to an embodiment of the present invention.
FIG. 2 shows an embodiment of the present invention in which the carcass is one
FIG. 3 is an enlarged front cross-sectional view of an example layer.

This pneumatic radial tire for passenger cars includes a pair of bead wires 1A, a pair of side parts 2,
A belt layer 5 is disposed between the tread portion 3 and the carcass layer 4 in connection therewith.

Incidentally, as the material of the cord of the carcass layer 4, organic fibers such as nylon and polyester are generally used in passenger car tires.

Furthermore, although steel cords are mainly used as cords for the belt layer 5, aramid cords can also be used. A nylon cover has also been inserted to improve high-speed performance.

Next, the bead portion 1 of this pneumatic radial tire is reinforced with a carbon fiber reinforcing layer 8 made of carbon fiber cord, and this carbon fiber reinforcing layer 8 is sandwiched between an upper bead filler 7 and a lower bead filler 6. It has a pincer area indicated by N.

The carbon fiber cord used for the carbon fiber reinforcing layer 8 reinforcing the bead portion 1 has a tensile strength of 100 Kg/mm ² or more, a tensile modulus of 5000 Kg/mm ² or more,
Preferably tensile strength 200Kg/mm ² or more, tensile modulus
After applying an adhesive of 10% to 50% of the weight per unit length of the fiber to a carbon fiber having a property of 15000Kg/mm2 or ^more , the twist coefficient K value expressed by the formula K=T√ is The twist is added so that the range of 0≦K≦1800 is achieved, and the twisting structure is as follows: First, a first twist is applied to each of several carbon fibers, and then a final twist is added to the several carbon fibers. A so-called double-twisted structure may be used, or a single-twisted structure in which a single carbon fiber thread is simply twisted.

In the above formula for the twist coefficient K, T is the number of twists of the cord (twists/10 cm), and D is the total denier of the cord.

In addition, the method for manufacturing the carbon fiber cord described above involves impregnating untreated carbon fiber yarn with a mixture of an adhesive, a resorcinol/formalin initial condensate, and rubber latex (hereinafter referred to as RFL), and drying it. , by adding a predetermined twist.

The amount of adhesive RFL attached to carbon fiber is 10
If it is less than 50%, not only will the adhesion with rubber be insufficient, but the bending fatigue properties of carbon fibers cannot be improved. On the other hand, if it exceeds 50%, the adhesive layer will be Due to the thickness, not only does it dry insufficiently, but also air bubbles form in the adhesive layer, making it difficult to obtain a uniform cord, so the amount of adhesive applied should be 20% or less.
40% is preferred.

In addition, when applying adhesive, it is important to sufficiently impregnate the carbon fiber filament with the adhesive to improve bending fatigue, and for this reason, it is necessary to impregnate the carbon fiber filament with the adhesive while it is open. preferable.

Note that the adhesive-treated carbon fiber yarn has enough adhesive adhering to it, so it maintains its cohesiveness even when it is not twisted, but it is preferable to add some twist to it from the viewpoint of cohesiveness. , therefore, the above twist coefficient K
is preferably in the range of 300≦K≦1500.

Next, as described above, the center point height H in the tire cross-sectional direction of the pinch area N where the carbon fiber reinforcing layer 8 is sandwiched between the upper bead filler 7 and the lower bead filler 6 is set higher than the height R of the rim flange 9, and It is set within 2.5 times the height R of the rim flange 9,
Furthermore, this carbon fiber reinforcing layer 8 is arranged on the inner side of the tire cross section on the bead portion 1 side from the center point height H of the pinch area N, and on the outer side of the tire cross section on the tread portion 3 side than the center point height H. By arranging the carbon fiber reinforcing layer 8 as described above, it becomes possible to put the carbon fiber reinforcing layer 8 in the most favorable arrangement state against external forces.

That is, by arranging the carbon fiber reinforcing layer 8 in the bead portion 1 away from the rim flange 9 that is the fulcrum of bending, it is placed in the tensile region caused by bending, and on the other hand, the carbon fiber reinforcing layer 8 is placed in the tensile region caused by bending, and the carbon fiber reinforcing layer 8 is placed in the tensile region that is generated by bending. In this case, it becomes possible to conveniently arrange the carbon fiber reinforcing layer 8 on the tire surface side on the outside of the bending, that is, on the tensile area caused by the bending.

Therefore, the pincer region N is smaller than the height of the lower bead filler 6, but preferably 80% or less of the lower bead filler height F in order to improve the arrangement of the carbon fiber reinforcing layer 8.

Furthermore, by setting the center point height H of the pinch area N in the tire cross-sectional direction to be higher than the height R of the rim flange 9 and lower than 2.5 times the height R of the rim flange 9, It becomes possible to arrange the inflection point of the carbon fiber reinforcing layer 8 itself near the inflection point of the bending deformation of the bead portion 1 and the side portion 2 at the center point height H of .

Therefore, even if an extreme overload is applied, it exhibits good load durability that can sufficiently withstand it.

Note that arranging 1.5R≦H≦2R is the most preferable relationship for improving durability.

On the other hand, if the modulus of the carbon fiber cord used for the carbon fiber reinforcing layer 8 is less than 30 kg/cm ² , the elasticity of the carbon fiber reinforcing layer 8 in the bead portion 1 will decrease, and the reinforcing effect cannot be exhibited. If it exceeds 70 kg/ ^cm2 , the coated rubber will become too hard and productivity will deteriorate, and for example, heat generation during coating will cause a scorch phenomenon, so-called burning, which is undesirable. Make sure to use one with a 100% modulus of ^cm2 to 70Kg/ ^cm2 .

In addition, the number of carbon fiber cords to be inserted is
If the number of cords exceeds 60 per 5 cm when measured in the perpendicular direction, the penetration of the coated rubber between the cords will be inhibited.
5 cm is undesirable as it leads to a decrease in adhesive strength, and if it is less than 20, the reinforcing effect will be insufficient.
20 to 60 carbon fiber cords per cord are preferred.

Furthermore, by intersecting the carcass cords of the carcass layer 4 at an angle of 20° to 70°, the carbon fiber reinforcing layer 8 of the bead portion 1 is reinforced in order to firmly bind each carcass cord. The effect is significantly exhibited, and the above-mentioned high-speed durability and handling stability can be improved.

If the above-mentioned intersection angle is more than 70°, the workability will deteriorate and it will not only be difficult to cut, but also wrinkles will easily occur during the work, which is undesirable. If it is less than 20°, the binding force of each carcass cord will decrease, which is not desirable. do not have.

Further, the height C of the carbon fiber reinforcing layer 8 in the tire cross-sectional direction is set lower than the tire maximum width position. If the height C in the cross-sectional direction of the tire is higher than the tire maximum width position, the carbon fibers are likely to break at the ends of the carbon fiber reinforcing layer 8, which is not preferable.

The reason for this is that the higher the height, the closer the end of the carbon fiber reinforcing layer 8 is to the tire shoulder, that is, the area where bending deformation is large during driving, which significantly reduces durability. be.

Next, in the embodiment of the present invention shown in FIGS. 1 and 2 having the above configuration, the conventional example shown in FIGS. 3 and 4, and the comparative example shown in FIGS. 5 and 6, tire size 185 The results of an indoor load durability test using an actual pneumatic radial tire of /70HR14 and comparing the tires shown in each drawing will be described below.

The cords of the carbon fiber reinforcing layer 8 in the pneumatic radial tire used in this test were arranged at an intersection angle of 30° with respect to the carcass cords of the carcass layer 4, and the thickness was 1.5 mm.
100% modulus is 45Kg/ ^cm2 per 5cm of rubber
Forty carbon fiber cords with a 1800d/2 structure and a twist of 10 ^S x 10 ^Z (twists/10 cm) were arranged, and the adhesive coverage was 30%.

In addition, the carcass layer 4 has a 2-layer structure in which 1000d/2 polyester cord layers are arranged in a radial carcass shape, and 1×5 (0.25) steel cords are intersected with each other at 20 degrees to the tire circumferential direction as the belt layer. I used the one from

On the other hand, in the pneumatic radial tire according to the embodiment of the present invention, the height C of the carbon fiber reinforcing layer 8 shown in FIG.
is 45% of the tire cross-sectional height T, the pinch area N is 40% of the height F of the lower bead filler 6, and the midpoint height H in the tire cross-sectional direction is the height R of the rim flange 9.
1.5 times, and the carbon fiber reinforcing layer 8 is arranged on the inner side of the tire cross section on the bead portion 1 side from H, and on the outer side of the tire cross section on the tread portion 3 side from H. FIG. 2 shows an example in which one carcass layer of 1500 d/2 polyester cord layers is arranged in a radial carcass shape, and the end of the carcass layer 4 is elevated so as to embrace the carbon fiber reinforcing layer 8.

Next, in the conventional pneumatic radial tire shown in FIG. 3, the carbon fiber reinforcing layer 8 is arranged inside the tire cross section, and its height C is set to C=
In the other conventional example shown in FIG. 4, the carbon fiber reinforcing layer 8 is arranged on the outside of the tire cross section, and its height C is set to C=0.45T.

Further, the upper bead filler is not provided, and only the lower bead filler is used, making the bead filler height equivalent to that of the present invention.

Furthermore, in the pneumatic radial tire in the comparison example shown in FIG. 5, which is compared with this embodiment, the pinch area N=
0.5F, the height of the center point in the cross-sectional direction of the tire is H=R, and the other arrangement is the same as the embodiment shown in FIG. 1, C=
0.45T, and in the other comparison example in Figure 6, the pincer area N = 0.4F, the height of the center point in the cross-sectional direction of the tire H = 3R, and the other arrangement is C = 0.7T. This is similar to the embodiment shown in FIG.

The indoor load durability tests conducted using the tires shown in Figures 1 and 3 to 6 above were conducted using an indoor drum testing machine (diameter 1707 mm), and the test conditions were as follows.

(1) Rim: 5J×14 (2) Speed: 81Km/Hr constant (3) Load: From 475Kg, the load was increased by 60Kg every 4 hours until failure occurred.

The test results are shown in Figures 7 and 8, and are expressed as an index with the embodiment of the present invention in Figure 1 set as 100, and a larger value indicates better performance. It can be seen from FIGS. 7 and 8 that the structure of the example of the present invention exhibits better load durability than the conventional and comparative tires.

In addition, in the case of the tire of this embodiment in FIG. 7, the entire carbon fiber reinforcing layer 8 was destroyed, whereas in the conventional example tire of FIG. The conventional tire shown in the figure is characterized in that the carbon fiber reinforcing layer 8 at the end of the rim flange 9 breaks.

Furthermore, even in FIG. 8, the carbon fiber reinforcing layer 8 at the end of the rim flange 9 in the tire of the comparative example shown in FIG. In addition, in the tire of the comparison example shown in Fig. 6, the damage at the end on the tread side was relatively large, and this was due to the fact that H = 3R. It has been demonstrated that it is necessary to make the height R higher than R and within 2.5 times the height R of the rim flange 9, that is, H<2.5R.

That is, the above test results also show that in the examples of the present invention, the entire carbon fiber reinforcing layer 8 functions effectively and the load durability is significantly improved.

〔Effect of the invention〕

As described above, the present invention divides the bead filler constituting the bead portion into upper and lower parts, and provides the bead portion with a carbon fiber reinforcing layer made of carbon fiber cords so as to pass through at least the pinched area between the upper bead filler and the lower bead filler. The carbon fiber cord has a tensile strength of 100Kg/mm2 or ^more and a tensile modulus of 5000.
It is composed of carbon fibers of Kg/mm ² or more, the 100% modulus of the coated rubber is 30 to 70 Kg/cm ² , and the center point of the pinch area in the cross-sectional direction of the tire is higher than the rim flange height, and the rim flange height is higher than the rim flange height. of
The carbon fiber reinforcing layer is set within 2.5 times, and the part of the carbon fiber reinforcing layer extending from the pinch area to the bead part side is placed along the carcass layer in the maximum tensile area on the inside of the tire cross section, and the part extending from the pinch area to the bead part side is placed along the carcass layer, and the part extending from the pinch area to the bead part side is placed along the carcass layer. The extending portion is arranged along the carcass layer in the maximum tensile area outside the cross section of the tire, and the height of the end of the tread portion of the carbon fiber reinforcing layer is lower than the maximum width position of the tire. In cored radial tires, the carbon fiber reinforcing layer is arranged to effectively avoid compressive loads, which are the weak point of carbon fiber cords, so the load durability can be significantly improved.

As a result, we have developed an air-conditioning system for passenger cars in which the bead area is reinforced with a carbon fiber reinforcement layer, which provides better ride comfort than conventional steel cord bead reinforcement layers, and superior handling stability and high-speed durability than organic fiber reinforcement layers. This has the effect of being able to provide a radial tire with a radial tire.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of main parts of a pneumatic radial tire for a passenger car according to an embodiment of the present invention, and FIG.
The figure is an enlarged cross-sectional view of an example of the present invention in which the carcass is one layer, Figures 3 and 4 are cross-sectional views of essential parts of the bead portion of the conventional example, and Figures 5 and 6 are 7 and 8 are cross-sectional views of the main parts of the bead portion of the comparison example compared to the field in Figure 2, Figures 2, 3, 4, and 5.
FIG. 7 is a diagram illustrating the results of an indoor load durability test comparing the pneumatic radial tires shown in FIG. 6 and FIG. 6. FIG. 1...Bead portion, 3...Tread portion, 6...Lower bead filler, 7...Upper bead filler, 8...
...Carbon fiber reinforcement layer, 9...Rim flange, H...
Center point height, N: Pincer area, R: Height of rim flange.

Claims (1)

[Claims] 1 The bead filler constituting the bead portion is divided into upper and lower parts, and a carbon fiber reinforcing layer made of carbon fiber cord is provided in this bead portion so as to pass through at least the pinched area between the upper bead filler and the lower bead filler, and the carbon fiber cord is Tensile strength 100Kg/mm ²
or more and has a tensile modulus of 5000Kg/mm2 ^or more, and the coated rubber has a 100% modulus.
30 to 70 Kg/ ^cm2 , and furthermore, the center point of the pinch area in the cross-sectional direction of the tire is higher than the rim flange height,
and within 2.5 times the rim flange height, and the portion of the carbon fiber reinforcing layer extending from the pinch region to the bead portion side is arranged along the carcass layer in the maximum tension region inside the tire cross section, and The portion extending to the opposite tread portion side is arranged along the carcass layer in the maximum tensile area outside the tire cross section, and the height of the end of the carbon fiber reinforcing layer on the tread portion side is lower than the maximum width position of the tire. A pneumatic radial tire that is characterized by: