JPS632703A - 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 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. Acoording 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. Accordingly, the inter-layer shearing strain is mitigated and separation is suppressed, thus the steering stability and durability of a tire can be improved.

Description

[Detailed description of the invention] Spicy ′)! The present invention relates to pneumatic tires, particularly small tires for passenger cars, light trucks, pans, etc., and relates to tires that are compatible with handling stability and belt layer durability.

In addition, pneumatic tires are generally used as shown in Figure 11.12.
When a load is applied to l, the vicinity of the shoulder of the pneumatic tire l deforms from the state shown by the solid line to the state shown by the broken line, and the pneumatic tire l deforms into the state shown by the broken line. ! Since the portion 2 serves as a support, the other portion outside the tire 13T expands and the belt layer 3 in this portion is stretched in the circumferential direction. As a result, the reinforcing cord 5 of the belt ply 4 constituting the belt layer 3 is
From the state shown in the solid line to the state shown in the virtual line! Fall down to the calm,
The intersection angle with respect to the tire equatorial plane 6 becomes small (the extending direction is inclined so that it is parallel to the tire equatorial plane 6). Here, since the reinforcing cords 5 of the adjacent belt plies 4 have opposite inclination directions with respect to the tire equatorial plane 6, the reinforcing cords 5 of the belt ply 4 on the outer layer side and the reinforcing cords 5 of the belt ply 4 on the inner layer side shifts in the circumferential direction, and as a result,
As shown by hatching in FIG. 14, a large shear strain had occurred in the living room rubber 7 between these reinforcing cords 5. Since this living room shear strain increases as it approaches both ends of the belt layer 3 in the width direction, separation between the belt plies 4 may occur at both ends of the belt layer 3.

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 intersection angle with respect to the tire equatorial plane 6 is set to a relatively large value, and the tread radius is also increased to make the belt layer 3 as flat as possible.

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 in that the side force during turning is reduced, which significantly deteriorates steering stability. Furthermore, if the number of reinforcing cords per unit width of the belt layer 3 is reduced, the side force of the pneumatic tire decreases as described above, and the steering stability not only deteriorates significantly, but also the number of reinforcing cords per unit width of the belt layer 3 decreases. The strength of the power decreases.

There is a problem in that the durability (safety factor) against shocks applied when climbing over protrusions, etc., deteriorates. moreover,
If the tread radius is increased and belt layer 3 becomes moored,
There are problems in that the manufacturing cost is high and it is likely to cause abnormal wear of the tread. As described above, the conventional method has a problem in that when attempting to prevent separation, the tire's dynamic performance or durability deteriorates.

These problems with IELMi aging can be solved by overlapping two belt plies reinforced with multiple metal cords so that the metal cords are alternately inclined in opposite directions with respect to the tire equatorial plane. In a pneumatic tire with a belt layer composed of each metal cord? When the diameter of the filament is Ri (mm), 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 is This can be solved by satisfying both of the following expressions: Σ Ri<3.15 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,
The buried metal cord becomes easy to bend, so 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 living room shear strain and causes the belt layer to bend. This prevents separation from occurring at both ends.

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

In Figs. 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 tethered carcass layers with the inner end of the carcass layer 12 folded back in the radial direction. a bead core 13; a belt layer 14 disposed on the radially outer side of the carcass layer 12;
Carcass layer 12. A tread 15 disposed radially outward 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 18 is opposite. As shown in FIG. 4, each metal cord 17 is composed of a plurality of filaments 19 twisted together, and each filament 18 has the same diameter Ri (mffi). When the belt layer 14 is brought into contact with the ground by applying an appropriate load after being filled with the material, 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. Therefore, the inventor of the present invention repeatedly conducted various experiments and inferences in order to reduce this interlaminar shear strain.

It has been found that the filament (19) constituting the metal cord (17) embedded in the belt layer (14) has a large effect on the shear strain in the living room. Therefore, the inventor of the present invention conducted further research and devised a method of applying to the tire 11 a belt layer 14 using a filament 19 that satisfies the following two equations.

i=1 i2Σ Ri<3.15 ・・・・・・
Equation 2 Here, m means the number of filaments 19 constituting one metal cord 17, and n means the total number of metal cords 17 driven into the belt layer 14. Therefore, is the index of the bending rigidity of each metal cord 17, and i=1 is the index of the tensile rigidity of each metal cord 17. Therefore, Equation 1 is the ratio of the bending stiffness index and the tensile stiffness index of the metal cord 17. The smaller this value is, the easier the metal cord 17 is to bend. Therefore, even if the metal cord 17 is about to fall due to the above-mentioned deviation, the metal cord 17 is held in place by the interlayer rubber 20.
．． As shown by the imaginary line in Figure 3, it is pulled back and curved to some extent, reducing the interlayer shear strain. Also, if the value is 0
．． If the value is 0.031 or more, as shown in FIG. The results shown in Figure 5 were obtained by preparing a large number of passenger car radial tires filled with the normal internal pressure, size 1757705 R13, and having a belt layer composed of two belt plies, and applying a load of 200% of the normal load. Drum L was driven for 30,000 km at 60 Ka while
This was determined by running the tire for a long time and measuring the size of cracks at the ends of the belt layer in the width direction, with the condition that the strength per unit width of the belt layer of each tire is the same. Also.

In Equation 2, if the value is 3.15 or more, the bending stiffness index per metal cord 17 increases rapidly as shown in FIG. 6, and the shear strain in the living room becomes significantly large. Must be less than 3.15.

Moreover, it is preferable that the filament 19 of each metal cord 17 satisfies the following formula 3.

i=1 The reason is that, as shown in FIG. 7, the value of interlayer shear strain increases outside this range.

Next, the test results will be explained with reference to Figures 8.9.10. The tires used in this test were the same as those described in FIG. 5 above. The test tire to which the present invention was applied was made of a single wooden steel cord with a diameter Ri of 0.15 (
mm), and as a result, i=I 1=1 i=1 i=1.On the other hand, the comparative tire l is made by twisting one steel cord with a diameter Ri of 0. It is composed of five filaments of .23 (Ilm) twisted together, and in i = ] i = 1 i = 1.The other configurations are the same as the test tire, especially:
The strength per unit width is the same, 494 Kg/Cm. In addition, Comparative Tire 2 was also used in this test, and the difference between Comparative Tire 2 and Comparative Tire 1 is that Comparative Tire 2
The belt layer is 5 (■) wider than the belt layer width of comparative tire 1.
Everything else is exactly the same except that it is narrower. Figure 8 is a graph showing the relationship between the load acting on the tire and the interlaminar shear strain between adjacent belt plies, and Figure 9 is a graph showing the tire skidding when turning with a load of 400 kg applied. It is a graph showing the relationship between angle (degree) and side force. 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 interlaminar shear strain decreases in the comparative tire 1, and the side force decreases in the comparative tire 2. It's getting worse. FIG. 10 is a graph showing the results of a comparative test on the size of cracks at the ends of the belt layer in the width direction under the same conditions as in FIG. From this figure, it can be seen that the interlaminar shear strain of the test tire was significantly improved compared to Comparative Tire 1.2.

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

As explained above, according to the present invention, interlaminar shear strain can be reduced without reducing the pressure performance and durability performance of the tire.

[Brief explanation of drawings]

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. Fig. 6 is a graph showing the relationship between the bending stiffness index of the metal cord and the ratio of the tensile stiffness index of the metal cord, and Fig. 7 is a graph showing the relationship between the bending stiffness index of the metal cord and the ratio of the metal cord diameter index. A graph showing the relationship between strain index and tensile stiffness index of metal cord,
Figure 8 is a graph showing the relationship between interlaminar shear strain and load acting on the tire, Figure 9 is a graph showing the relationship between side force and sideslip angle during turning, and Figure 10 is a graph showing the relationship between side force and sideslip angle when turning. A graph showing the relationship between the size of cracks and mileage. Fig. 11 is a side view of a conventional pneumatic tire. Fig. 12 is a meridian cross-sectional view of the tire. Fig. 13 is a partial plan view of the belt layer. Fig. 14 is a graph showing the relationship between crack size and mileage. 14 is a sectional view taken along the line n-■ in FIG. 13. FIG. 14...Bell) 5 1B...Belt ply 1
7... Metal cord 18... Tire equatorial plane 19
...Filament patent applicant Brideston Co., Ltd. Agent Patent attorney: 1) Toshio Figure 1 14... Belt layer 16... Belt ply 17... Metal cord 18... Tire equatorial plane Figure 2 Figure 3 Figure 4 Figure 5 Figure 60 l Figure 7 ΣR12- 1 = 1 Figure 8 □ Test tire - - Comparison tire 1 Load (s) □ Sideslip angle n) - 0 Test tire mileage (h )□ Figure 13 Figure 14

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^4/^m ^×^nΣ
_i_=_1Ri^2<0.031 and the formula ^mΣ_i_=_1Ri<3.15. A pneumatic tire characterized by satisfying both of the following.