JPS61287804A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve both durability and control stability by configurating a device in such a way that the height of a center point of a reinforced layer is specified, and furthermore the said layer below the said center point is in the inner side of the tire cross section, and the said layer above the said center point is in the outer side of the tire cross section in a tire having a carbon fiber reinforce bead section. CONSTITUTION:The height H of a center of an area N of a carbon fiber reinforced layer 8 where the area is sandwiched by both an upper and lower bead filler 7 and 6 in the cross section of a tire, is made to be higher than the height R of a rim flange 9, and is set to be within 2.5R. And the said area is arranged in such a way that it is in the inner side of the tire cross section at the bead section (1) side in the area under the center point height H, and is in the outer side of the tire cross section at the tread section 3 in the area above the center point height H simultaneously. This configuration is capable of improving such performance as durability, control stability, and resistance to high speed.

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 reinforcement layer made of cord to reinforce the bead and reinforcing the bead, it is possible to keep the force applied to the carbon fiber reinforcement layer relatively on the tensile side, thereby increasing its durability. The present invention relates to a pneumatic radial tire having a bead structure that significantly increases handling stability and high-speed durability without impairing ride 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, and there is no end in sight.

For example, HR tires that can run faster than SR tires,
Furthermore, there are demands for VR tires that can run at higher speeds, and flat tires that have better handling stability.

However, from the vehicle perspective, due to the tire housing, there is a demand for tires that can run at high speeds with the same profile ratio as before, and that also have 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 a material similar to that of 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 was also heavy, 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 strengthen the bead without compromising riding comfort. Carbon fiber has the advantage of being much lighter than steel cord, compared to organic fiber.

On the other hand, reinforcing the area around the bead is to suppress the movement of the bead and to increase the rigidity of the area around the bead.This will suppress the movement around the bead during high-speed driving, for example, and will allow you to stand up while riding. 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, and these tires include a carbon fiber reinforcing layer 8 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, the carbon fiber reinforcing layer 8 is provided outside the lower bead filler 6.

In addition, in the above figure, IA 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, as shown in FIGS. Although it is extremely strong, it is weak against compression, which has the disadvantage of significantly inferior 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, the rim flange 9
If the bead portion 1 is subjected to bending deformation using the carbon fiber cord as a fulcrum, compression will be applied to the carbon fiber cord, which will reduce durability, which is undesirable.

In addition, when arranged as shown in Figure 3, the side part 2 of the tire
However, there is a drawback in that bending deformation opposite to that of the bead portion 1 is applied around the maximum width of the tire as a fulcrum, reducing durability for the same reason as the bead portion 1.

[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, the pneumatic radial tire of the present invention is a pneumatic radial tire having a bead portion provided with a carbon fiber reinforcing layer made of carbon fiber cord, in which the carbon fiber reinforcing layer is sandwiched between an upper bead filler and a lower bead filler. The center point height of the region 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 set at a bead portion higher than the center point height of the pinching region. It is configured by arranging it on the inner side of the tire cross section on the side, and on the outer side of the tire cross section on the tread side from the center point height.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a front cross-sectional view of essential parts of a pneumatic radial tire for a passenger car according to an embodiment of the present invention, and FIG. 2 is an enlarged front cross-sectional view of an example in which the carcass is one layer according to an embodiment of the present invention. It is a diagram.

This pneumatic radial tire for passenger cars is composed of a pair of bead wires IA, a pair of side parts 2, and a belt layer 5 connected to these and disposed between a tread part 3 and a carcass layer 4. There is.

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 in the figure.

The carbon fiber cord used for the carbon fiber reinforcing layer 8 reinforcing the above-mentioned dowel portion 1 has a tensile strength of 100 k.
g/mm2 or more, a tensile modulus of 5000 kg/mm2 or more, preferably a tensile strength of 200 kg/mm2 or more, and a tensile modulus of 15000 kg/mm2 or more, and 10% of the weight per unit length of the fiber. from 5
After applying 0% adhesive, twist was added to the twist coefficient expressed by the formula of K = Tf stone so that the value was in the range of O≦≦1800, and the twisted structure was made up of several strands. The structure may be a so-called mono-twisted structure in which each of the carbon fibers is first twisted, and then several of them are combined and a final twist is added, or it may be a single-twisted structure in which only one carbon fiber thread is twisted. good.

In the above equation for the twist coefficient, 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 abbreviated as RFL), and drying it. After that, it is created by adding a predetermined twist.

If the amount of adhesive RFL attached to carbon fiber is less than 10%, not only will the adhesion with rubber be insufficient, but the bending fatigue resistance of carbon fiber will not be improved;
If it exceeds 20%, the thickness of the adhesive layer will not only dry insufficiently during drying heat treatment, but also air bubbles will form in the adhesive layer, making it difficult to obtain a uniform cord. % to 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 in an open state. 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, it is preferable that the twist coefficient K is in the range of 300≦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 to be higher than the height R of the rim flange 9. , and is set within 2.5 times the height R of the rim flange 9, and furthermore, this carbon fiber reinforcing layer 8 is set to the inner side of the tire cross section on the one door portion 1 side from the center point height H of the pinch area N. In addition, the carbon fiber reinforcing layer 8 is disposed on the outside of the tire cross section on the side of the tread portion 3 from the center point height H, and by arranging the carbon fiber reinforcing layer 8 as described above, the carbon fiber reinforcing layer 8 is provided in the most favorable manner against external forces. This makes it possible to create a suitable arrangement state.

゛That is, by arranging the carbon fiber reinforcing layer 8 in the bead portion 1 away from the rim flange 9, which is the fulcrum of bending, the carbon fiber reinforcing layer 8 is placed in the tensile region caused by bending, and on the other hand, in the side portion 2 on the tread portion 3 side. 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 fill area N of the fill area N is smaller than the height of the lower bead filler 6, but preferably the lower bead filler height F
80% or less is desirable in order to improve the arrangement of the carbon fiber reinforcing layer 8.

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

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 carbon fiber cord used for the carbon fiber reinforcing layer 8 has a modulus of less than 30 kg/aJ, the elasticity of the carbon fiber reinforcing layer 8 in the bead portion 1 will decrease, and the reinforcing effect cannot be exhibited, resulting in It is preferable to use 30 kg/ci or more, as this will lead to a decrease in stability, and if it exceeds 70 kg/ci, the coated rubber will become too hard and productivity will deteriorate. It is better to use one with a 100% modulus of 70 kg/ci from cffl.

In addition, if the number of carbon fiber cords to be implanted exceeds 60 per 5C11 when measured in the perpendicular direction of the cord, the infiltration of the coated rubber between the cords will be inhibited, resulting in a decrease in adhesive strength, which is undesirable; Since the reinforcing effect would be insufficient in this case, it is preferable to use 20 to 60 carbon fiber cords per 5 cm.

Furthermore, by intersecting the carcass cords of the carcass layer 4 at an angle of 20° to 70°, the carbon fiber cords firmly bind each carcass cord, so that the reinforcing effect of the carbon fiber reinforcing layer 8 of the bead portion 1 is enhanced. This makes it possible to improve the high-speed durability and handling stability.

If the above-mentioned intersection angle is more than 70 degrees, 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, and if it is less than 20 degrees, the binding force of each carcass cord will decrease. Undesirable.

Further, the height C of the carbon fiber reinforcing layer 8 in the tire cross-sectional direction is preferably 70% or less of the tire cross-sectional height T, preferably lower than the tire maximum width position, and if it is too high, the carbon fiber reinforcing layer 8
This is not preferable because the carbon fibers tend to break at the terminals.

The reason for this is that the higher the height, the closer the end of the carbon fiber reinforcing layer 8 is to a part of 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, the conventional example shown in FIGS. 3 and 4, and the comparative example shown in FIGS. 5 and 6, the tire size is 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.

Note that 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. 40 pieces of 180 per 5 cm in a rubber with a 100% modulus of 45 kg/-
A carbon fiber cord with a 0d/2 structure and a twist of 10'Xl02 (turns/10cm) was placed, and the adhesive coverage was 30%.

In addition, in the carcass layer 4, 1000d/2 polyester cord layers are arranged in a radial carcass shape, and as a belt layer, steel cords I x 5 (0,25) are intersected at 20 degrees with respect to the tire circumferential direction. A two-layer structure was used.

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. 1 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 in the tire cross-sectional direction is H is 1.5 times the height R of the rim flange 9, and the carbon fiber reinforcing layer 8 is arranged on the inner side of the tire cross section on the side of the bead part 1 from H, and on the outside of the tire cross section on the side of the tread part 3 from H. ing. 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 raised 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
is C=0.45T with respect to the tire cross-sectional height T, and in the other conventional example shown in FIG. It is set to .45T.

Further, the upper bead filler is not used, 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.
The center point height in the cross-sectional direction of the tire is set as H=R, and the other arrangement is set as C=0.457 as in the embodiment shown in FIG.
Another comparative example, shown in FIG. 6, has a pincer area N=0.
4F, the height of the center point in the cross-sectional direction of the tire H = 3R,
The arrangement is the same as the embodiment shown in FIG. 1 except that C=0.77.

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

(11 rims: 5JX14 (2) Speed: 81 km/Hr constant (3) Load:
The load was increased from 475 kg by 60 kg 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 tire of the conventional example shown in 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, as shown in FIG. 8, the carbon fiber reinforcing layer 8 at the end of the rim flange 9 in the comparative tire shown in FIG. In addition, in the tire of the comparison example shown in FIG. 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 provides a pneumatic radial tire having a bead portion provided with a carbon fiber reinforcing layer made of carbon fiber cords, in which the sandwiched region where the carbon fiber reinforcing layer is sandwiched between an upper bead filler and a lower bead filler is provided. The center point height in the cross-sectional direction of the tire is set higher than the rim flange height and within 2.5 times the rim flange height,
The carbon fiber reinforcing layer is arranged on the inner side of the tire cross section on the bead part side from the center point height of the pinch area, and on the outer side of the tire cross section on the trend part side from the center point height, so that the pneumatic radial tire of the present invention In this case, the carbon fiber reinforcing layer is arranged to effectively tear the compressive load, which is the weak point of the carbon fiber cord, 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 vertical sectional front view of essential parts of a pneumatic radial tire for a passenger car according to an embodiment of the present invention, FIG. 3
5 and 6 are sectional views of the main parts of the bead part of the conventional example, FIGS. 2 is a graph showing the results of an indoor load durability test comparing the pneumatic radial tires shown in FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6. DESCRIPTION OF SYMBOLS 1... Bead part, 3... Tread part, 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] In a pneumatic radial tire having a bead portion provided with a carbon fiber reinforcing layer made of carbon fiber cord, the center point height in the cross-sectional direction of the tire in the pinch area where the carbon fiber reinforcing layer is sandwiched between an upper bead filler and a lower bead filler. be higher than the rim flange height, and 2.
The carbon fiber reinforcing layer is set within 5 times, and the carbon fiber reinforcing layer is arranged on the inner side of the tire cross section on the bead part side from the center point height of the pinch area, and on the outer side of the tire cross section on the tread part side from the center point height. A pneumatic radial tire.