JPS632704A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the steering stability and durability of a pneumatic tire for car by specifying relational equations between the filament diameter of metal cords constituting a belt ply, the number of filaments, and the total number of buried metal cords. CONSTITUTION:Each of metal cords 17 constituting a belt ply 16 is made by twisting multiple filaments 19. In this case, the diameter Ri (in mm) of the filament 19, the number (m) of filaments constituting one cord 17, and the total number (n) of cords 17 buried in a belt layer 14 are set so as to satisfy Equation I and Equation II. According to this constitution, the metal cords are made easy to be bent, and even if the metal cords tend to fall due to drift, they are pulled back by the inter-layer rubber and deformed, thus the interlayer shearing strain is suppressed and separation is prevented. Accordingly, the steering stability and durability of a tire can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION 9-1) The present invention relates to pneumatic tires, particularly small tires for passenger cars, light trucks, pans, etc., and relates to a tire that is compatible with handling stability and belt layer durability.

In general, as shown in Figure 10.11, when a load is applied to a pneumatic tire l, the vicinity of the shoulder portion of the pneumatic tire l deforms from the state shown by the solid line to the state shown by the broken line. And the grounding part 2! Since the tire is F-bearing, the outer diameter T of the tire in other parts is expanded and the belt layer 3 in the part is stretched in the circumferential direction.

As a result, the reinforcing cords 5 of the belt ply 4 constituting the belt layer 3 fall down from the state shown by the solid line in FIG. Here, since the reinforcing cords 5 of the adjacent belt plies 4 are inclined in opposite directions with respect to the tire equatorial plane 6, the belt ply 4 on the outer layer side is reinforced. The cord 5 and the reinforcing cord 5 of the belt ply 4 on the inner layer side are displaced in the circumferential direction, and as a result, shear strain is generated in the interlayer rubber 7 between these reinforcing cords 5, as shown by hatching in FIG. Ta. This interlayer shear strain is caused by the belt layer 3
The closer the belt layer 3 is to both ends in the width direction, the larger it becomes. In order to prevent such separation, conventional methods have been to narrow the width of the belt layer 3, reduce the number of reinforcing cords 5 per unit width of the belt layer 3, or reduce the number of reinforcing cords 5 in the belt layer 3. The crossing angle with respect to the tire equatorial plane 6 is set to a relatively large value, and furthermore, the tread radius is increased to help limit the turning portion of the belt layer 3.

However, as mentioned above, if the width of the belt layer 3 is narrowed or the intersection angle of the reinforcing cord 5 of the belt layer 3 with respect to the tire equatorial plane 6 is set to a relatively large value, the pneumatic tire There is a problem that the side force during turning decreases, which significantly deteriorates the steering stability.In addition, if the number of reinforcing cords inserted in the middle part of the belt layer 3 is reduced, the pneumatic tire Not only does the side force of the belt decrease and the steering stability deteriorate significantly, but also the strength per medium width of the belt layer 3 decreases.

There is a problem in that the durability (safety factor) against shocks applied when climbing over protrusions, etc., deteriorates. moreover,
If you increase the tread radius and make the belt layer 3 flat,
′! There are problems in that A construction is expensive and tends to cause abnormal wear of the tread. In this way, when attempting to prevent separation using conventional methods,
There is a problem in that the maneuverability and durability of the tire are reduced.

This problem can be solved by overlapping two belt plies reinforced with a large number of metal cords so that the metal cords are alternately inclined in opposite directions with respect to the tire equatorial plane. In a pneumatic tire having a belt layer configured, the diameter of the filament constituting each metal cord is Ri (m), the number of filaments constituting one metal cord is m, and the metal driven into the belt layer is When the total number of cords is n, this problem can be solved by making sure that the belt layer satisfies both the following equations: Σ Ri2>0.48 i=1.

1" If the belt layer satisfies the above two formulas, compared to a conventional belt layer with the same strength per unit width,
Since the buried metal cord becomes easier to bend, even if the metal cord tries to fall due to the above-mentioned deviation, the metal cord is pulled back by the living room rubber and deforms to some extent, which alleviates the interlayer shear strain and bends both ends of the belt layer. The goal is to provide a tire that prevents separation that occurs in the parts, and that has a cost commensurate with its performance.

1 presentation 1 Hereinafter, one embodiment of the present invention will be described based on the drawings.

In Fig. 1.2.3, 11 is a pneumatic radial tire, and this tire 11 has a carcass layer 12 deformed into a toroidal shape, and a pair of carcass layers 12 whose inner ends in the radial direction are folded back and moored together. a bead core 13; a belt layer 14 disposed on the radially outer side of the carcass layer 12;
Carcass layer 12. It has a tread 15 disposed on the radially outer side of the belt layer 14. The belt layer 14
is composed of two belt plies 16 superimposed on each other, and each belt ply 16 is reinforced with a large number of parallel metal cords 17 made of steel or the like. The intersecting angles of these metal cords 17 with respect to the tire equatorial plane 18 are constant, and the metal cords 17 in adjacent belt plies 16
The direction of inclination with respect to the tire equatorial plane I8 is opposite. As shown in FIG. 4, each metal cord 17 is composed of a plurality of filaments 19 twisted together, and the diameter of each filament 13 is the same, Ri (am).
After filling such a tire 11 with, for example, a regular internal pressure,
When the belt layer 14 is grounded by applying an appropriate load, the belt layer 14 is expanded as described above, and a large shear strain is generated at both ends of the belt layer 14 in the width direction. Here, conventionally,
The durability of the belt layer 14 caused by living room shear strain has been considered by focusing on the rigidity of a single belt ply 16 or the behavior of the belt ply 16 caused by the arrangement direction of the metal cords 17. I couldn't explain the durability well from the points. Therefore, the inventor conducted various experiments,
As a result of repeated reasoning, we found that the effective cord diameter index, tensile stiffness index, and bending stiffness index of the metal cord 17 have a large influence on the living room shear strain in the two-layer belt layer 14! It was found that it gave Therefore, after further research, Akira Kimitsu devised a method of applying to the tire 11 a belt layer 14 that uses a filament 19 that satisfies the following two equations.

i=1 i-1 ...Formula 1 Here, m is the number of filaments (19) constituting one metal cord 17, and n is the metal cord driven into the belt layer 14. It means the total number of 17. therefore.

is the effective cord diameter of one metal cord 17, that is, the small wire metal cord 17 when a single single wire metal cord 17 is temporarily formed by integrating a large number of filaments 19.
It is an index of the diameter of Also.

i Wealth l is an index of the bending rigidity of each metal cord 17.

i=1 is an index of the tensile stiffness of each metal cord 17, and as a result, the latter half of the left side of equation 1 is the ratio of the bending stiffness index and the tensile stiffness index of the metal cord 17. And the smaller the value of formula l, the more metal cord 17
The metal cord 1 becomes easy to bend due to the above-mentioned deviation.
Even if the metal cord 17 tries to fall down, the interlayer rubber 2
0, it is pulled back and curved to some extent as shown by the imaginary lines in Figures 2 and 3, and the shear strain in the living room is reduced. Moreover, if the value is 5.25 or more, as shown in FIG. 5, the belt layer! The cracks that appear on both ends of 4 suddenly become large d.
Since re-separation occurs, the above value is 5°25.
where the result shown in Figure 5 shows that the normal internal pressure is filled and the size is t75/7GS R1
3, a large number of radial tires for passenger cars with a belt layer composed of two belt plies were examined, and the normal load was 20.
80Ktm on the drum while applying 0% load
This was determined by running the tires over 30,000 layers and measuring the size of cracks at the ends of the belt layer in the width direction, with the condition that the strength per belt layer of each tire is the same. There is. Furthermore, assuming that the strength per Φ width is the same, the smaller the cross-sectional area of the metal cords 17, the more the number of metal cords 17 to be driven increases, and the manufacturing cost of the belt layer 14 increases. Because of the metal cord! The cross-sectional area of the metal cord 17 must not be less than a certain limit, provided that the value of equation 2, that is, the cross-sectional area index of the metal cord 17, is 0.
If it is less than 48, the manufacturing cost will increase rapidly as shown in Figure 6, and the rate of improvement in tire performance will slow down relative to the rate of increase in cost, so the value must exceed 0.48. .

Next, the test results will be explained with reference to FIG. 7.8.9. The tires used in this test were the same as those described in FIG. 5 above. A test tire to which the present invention was applied was constructed using one steel cord with a diameter Ri of 0.23 (
am) is composed of 11 filaments twisted together.

Σ R12 = 0.5819 i = 1 iJ i = 1. On the other hand, the comparative tire l is constructed by twisting one steel cord with six filaments with a diameter Ri of 0.38 (layered sole). Ori.

■ Σ R42= 0.8884 i=1! Snow 1 i=1, and the other configurations are the same as the test tire, especially:
The strength per medium width is 494Kg/C weight, which is the same. In addition, Comparative Tire 2 was also used in this test, and the difference between Comparative Tire 2 and Comparative Tire I is that Comparative Tire 2
The width of the belt layer of Comparative Tire 1 is 5 (
■) is narrower, but everything else is exactly the same. Figure 7 is a graph showing the relationship between the load acting on the tire and the shear strain between adjacent belt plies, and Figure 8 is a graph showing the relationship between the load acting on the tire and the shear strain between adjacent belt plies.
3 is a graph showing the relationship between the sideslip angle (degrees) and side force of a tire when turning with a load of g applied thereto. As can be seen from these figures, the test tire reduces the interlaminar shear strain while maintaining the side force at a high value, but the comparison tire 1 has a living room shear strain, and the comparison tire 2 has a side force. It's getting worse. Figure 9 shows the size of cracks at the ends of the belt layer in the width direction.
It is a graph showing the results of a comparative test under the same conditions as the figure. From this figure, it can be seen that the test tire has significantly improved living room shear strain compared to comparative tires 1 and 2.

Note that the present invention may be applied to belt layers having reinforcing materials such as caps and layers.

1L1j As described above, according to the present invention, interlaminar shear strain can be reduced without deteriorating the tire's motion performance and durability performance, and a tire with a cost commensurate with a resilient moat can be provided.

[Brief explanation of the drawing]

FIG. 1 is a meridian cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a partial plan view of the belt layer, Figure 3 is a cross-sectional view taken along the line I-I in Figure 2, Figure 4 is a cross-sectional view of one metal cord, and Figure 5 is a crack that has occurred at both ends of the belt layer. 6 is a graph showing the relationship between the manufacturing cost index of the belt layer and the value of equation 2, and FIG. 7 is a graph showing the relationship between the magnitude of the belt layer and the value of the equation 2, and FIG. Graph showing the relationship with load, Figure 8 is a graph showing the relationship between side force during turning and sideslip angle, Figure 9 is a graph showing the relationship between the size of cracks that occur at both ends of the belt layer and travel distance. , Fig. 10 is a side view of a conventional pneumatic tire, Fig. 11 is a meridian sectional view thereof, Fig. 12 is a partial plan view of the belt layer, and Fig. 13 is a sectional view taken along the nn arrow in Fig. 12. be. 14...Belt layer 1B...Belt ply 1
7... Metal cord 18... Tire equatorial plane 18
...Filament patent applicant Brideston Co., Ltd. Agent Patent attorney Ta 1) Toshio Figure 1 14... Belt layer 16... Belt ply 17... Metal cord 18... Tire equatorial plane Figure 2 Figure 3 Figure 4 19...Filament Figure 5 Figure 7 □ Test tire load ('y) - sideslip angle (degrees) □ Figure 9 O Test tire travel distance (h) □

Claims (1)

[Scope of Claims] A belt layer constructed by stacking two belt plies reinforced with a large number of metal cords such that the metal cords are alternately inclined in opposite directions with respect to the tire equatorial plane. In a pneumatic tire, the diameter of the filament constituting each metal cord is Ri (mm),
When the number of filaments constituting one metal cord is m, and the total number of metal cords driven into the belt layer is n, the belt layer has the formula √(^m^×^nΣ_i_=_1Ri^2) /n+30
(^m^×^nΣ_i_=_1Ri^4/^m^×^n
Σ_i_=_1Ri^2)<5.25 and the formula ^mΣ_i_=_1Ri^2>0.48 A pneumatic tire characterized by satisfying both of the following.