JPH0261189A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire reinforced with a steel cord composed of a steel material having carbon content and toughness higher than respective specific levels, resistant to breakage of the cord even in the driving on a rough way of in the case of steep turn and having excellent durability and safety. CONSTITUTION:The objective pneumatic tire is at least partly reinforced with a steel cord having a toughness of >=135 (defined as a product of the strength and the areal contraction of the strand) and containing a steel material having a carbon content of 0.80-0.95% as the major part of the strand constituting the steel cord. The steel cord is preferably used as the belt layer or carcass layer of tire.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates in particular to improvements in steel cord reinforced pneumatic tires.

[Prior Art] In recent years, pneumatic tires reinforced with steel cords have been used for high-speed mass transportation or construction vehicles, but the steel cords have a high specific gravity, which increases the weight of the tires. There was a problem that fuel consumption increased.

Conventionally, as a countermeasure against this problem, it has been proposed to increase the strength of the steel cord by increasing its carbon content, thereby reducing the amount of steel cord used and obtaining a tire with low rollover (Japanese Patent Application Laid-open No. 57-51502 and Japanese Unexamined Patent Publication No. 1983-
No. 128902).

[Problems to be solved and attempted by the invention] However, in order to make steel cords highly strong, strong wire drawing processing is required, and strong wire drawing processing often causes wire breakage during processing, so it is actually difficult to avoid wire breakage. Therefore, it became necessary to lower the wire drawing speed, which was unfavorable in terms of productivity. In addition, the strong wire drawing process causes the steel cord to lose its toughness, and has the disadvantage that the steel cord can break if the tire is driven on rough roads or repeatedly turns sharply. Furthermore, a decrease in tenacity was observed in the steel cord itself, and the aperture 6a
Therefore, when designing tires, the outermost belt layer, etc.
There was a problem with parts that were difficult to use because they were subject to large deformations during use.

Therefore, the purpose of this invention is to provide even higher toughness while maintaining the high strength of conventional steel cords, increase productivity, and prevent breakage even when driving on rough roads or sharp turns, and the outermost belt layer Another object of the present invention is to provide a pneumatic tire reinforced with steel cords that can be applied to parts that undergo large deformations during use.

[Means for Solving the Problems] The present invention provides a pneumatic tire at least partially reinforced with steel cords, in which most of the strands forming the steel cords have a carbon content of 0.80 to 0.95%. The toughness expressed as the product of wire strength and aperture is 13.
5 or more.

In other words, since it is necessary for the steel cord to achieve the same high strength as the conventional steel cord, in this invention, most of the strands forming the steel cord are made of carbon having a higher carbon content than the conventional steel cord. Contains io, s
It was composed of iron material containing 0 to 0.95%.

Although it is possible to achieve a strength exceeding 300g7mm'' even with a carbon content of 0.80% or less, it requires wire drawing to achieve the strength as described above, resulting in a low-toughness steel cord with a low reduction of area. Neither the desired productivity improvement nor high toughness nor high resistance to large deformation can be obtained. If it exceeds 0.85%, the toughness will decrease due to the composition, but the liquid level ratio during wire drawing can be reduced.
Instead of having an area reduction rate of up to 97% as in the past,
If the liquid level ratio is as low as 94 to 96%, high toughness and productivity can be ensured.

Therefore, the present invention is characterized in that high strength is maintained by adjusting the iron composition, and high toughness is ensured by reducing the strength and paper area. Therefore, in this invention, both the characteristics of high strength and high toughness are expressed by wire strength and drawing precision, and the degree of their coexistence is evaluated as toughness expressed by wire strength x drawing precision. It uses steel cord with a coefficient of 135 or more. Note that the wire strength here is the value obtained by dividing the breaking load kg by the cross-sectional area of the wire in a tensile test of the wire (
kg/ll1112), and the aperture is the value obtained by dividing the difference between the tensile test fracture area and the original cross-sectional area by the original cross-sectional area.

Although the reduced area ratio ensures high toughness,
For carbon content of 0.95% or more, 300Kg/mn+”
However, even if the area reduction rate of the strands is adjusted, the strands become brittle and tend to break when bent, so most of the strands that form steel cords have a carbon content of 0. A preferable range is 80 to 0.95% iron material.

If the carbon content is around 0.80%, it is difficult to exhibit high strength while maintaining high toughness, so it is recommended to add additional elements such as silicon and nickel to the iron material composition in an amount of 1% or less. More preferred.

[Function] Since the present invention has the above-described structure, there is no need for strong wire drawing, and productivity is improved and toughness is improved. Therefore, the cord will not break even when driving on rough roads or making sharp turns, and can be applied to areas where large deformations occur in tires, expanding the range of uses.

[Example] (Example 1) First, four types of iron materials shown in Table 1 were prepared.

Steel symbols A and B are iron materials of the present invention, C is 5WR382^ and iron material equivalent to JP-A No. 57-51502, and D is Sga R372.
It is an iron material.

Table 1 (Note) Unit is element weight%.

Next, after wire drawing and heat treatment of these 4II types, Ct165%,
5 (+/! II electroplating with 35% Zn and brass plating by thermal diffusion. Wire diameter is 1.50 to 1.9
Finish with 5-. Table 2 shows the results of wet wire drawing, and the finished wire diameter is 0.35 m. Steel symbols C and D
The wire was drawn at a drawing speed of 600 m/ein because die wear and wire breakage were severe at a drawing speed of 800 w/sin.

Table 2 From Table 2, the finished wire of any steel type is 0.35
The strength of the strand of mn+ diameter is 330g/open2, but compared to steel types C and D, the iron materials of steel types A and B of the present invention have higher toughness. The productivity was about 33% higher.

Next, make a wire with a diameter of 0.20 mm from 6 steel in the same manner as above, and use a double twist type puncher stranding machine to 3X
A steel cord of 0.20+6X0.35+1111 was prototyped. Table 3 shows the results and physical properties of the cord.

(Left space below) This is due to the fact that Table 3 is strongly shaped so that it can be solved, but in the present invention, this does not occur and the strength is ensured.

Manufacture of Tires> Using each steel cord as a reinforcing cord for the belt layer,
A pneumatic tire with a tire size of 1000R20 was manufactured as a prototype.

It is recognized that the cord according to the present invention is excellent in terms of breakage and strength of the stranded wire in Table 4. As mentioned above, the steel cord SD using 5WR372 has the same wire strength as the others.
330K (1/II2), but if it is made of steel cord, it has lower strength than others.

This is because the drawing area reduction rate is large, so the strands become rigid, and if the shaping during twisting is not strong, each steel cord will be made of the compounded rubber shown in Table 4 above, with a thickness of 1.911 mm.
I topped it with 10. Each topping sheet is 13 ends/2.5 CII. This topping sheet is cut diagonally to form four belt layers. 1st bell l
- is 965 degrees to the upper right.

The second belt is at 918 degrees at the top left, the third belt is at 918 degrees at the top right, and the fourth belt is at 18 degrees at the top left.

Naori - Separately for the waste layer 3+9+15XO, 17
5+1 steel cord with 13 ends/2.5cm, 9
It was used at 0 degrees.

Next, these tires were attached to the idlers of the trailer, and with the lumber loaded, the truck drove along a rear-end coastal road with sharp left and right curves.

The results are shown in Table 5.

(Left below) Table 5 The TSA and TSB tires could not be driven after 100,000km and were removed midway. When the cause of the failure was investigated, it was discovered that the steel cord of the first belt had broken on both sides at a position approximately 5 CIs from the belt end, which caused part of the shoulder to swell. In contrast, the TSA
, TSB tires exhibit high durability and can withstand the large side force that is exerted on the tires when driving around such sharp curves.

Next, the same tires were attached to a dump truck driving on rough roads for a driving test. The results are shown in Table 6.

(Left below) Table 6 TSC and TSD tires have poor toughness, so if they run over protrusions scattered on a rough road, the cord will break immediately, and while this is repeated, damage will accumulate in the belt layer. There was no belt breakage in the TSA and TSB tires of the present invention, which had undergone berthing.

<Example 2) As in Example 1, 4w of A, B, C, and D were used as raw steel.
Four types were used to make wires with diameters of 0.175 as shown in the table below.

Table 7 Table 8 Similar to Example 1, steel types C and D are 1000 m/+min
In the above method, low-speed wire drawing has to be performed due to die wear and wire breakage, and the toughness of the obtained wire is low.

Next, from these wires, 3+9+15xQ, 175 steel cord is twisted into tubular type! Made with fi. The production results and physical properties of the steel cord are as shown in the following formula.

Manufacture of tires> These steel cords are made of 13 ends/2°5 CIl.
l, used as a carcass reinforcement cord under 90 degree conditions,
A prototype pneumatic tire of 295/75R22,514PR was manufactured. The belt cord used was the steel cord with the symbol SA of Example 1, and the conditions of the belt layer were the same as in Example 1.

Table 9 shows the results of the drum running test.

The test conditions were that the air pressure of each prototype tire was 2.5 kg/cm, which is extremely lower than normal, and the load was 2.5 kg/cm.
The weight was set at 5 tons. This is a durability test that assumes a situation where air pressure suddenly decreases due to stepping on a nail, etc. while driving under a heavy load.

The ninth example is when you notice a lack of tire pressure while driving on the highway.
While it is questionable whether TSC' and TSD' tires can reach nearby interchanges and service areas, the TSA' and TSB' tires of the present invention use steel cords with excellent toughness and are Due to its good durability, it can reach interchanges, etc., and tires can be changed, making it extremely safe.

(Example 3) As in Example 1, A, B, C, and D are used as original f4w4.
The 0-order table shows the results and physical properties of a steel cord of 1X2XO135 made using four types of steel and a wire with a diameter of 0.35111111.

(Left below) All tires eventually broke due to metal fatigue of the steel wire, but as is clear from the table above, there is a noticeable difference in mileage. Therefore, Example Table 10 shows the results.

Table 11 Next, these cords were topped with an end number of 20/2.5cm and a topping gauge of 1.45u, and two pieces were used as belts at an angle of 23 degrees, P195/75 R14
We prototyped a radial tire for passenger cars. Naori-Cass is polyester 1500d/2, number of ends 23/2.5cI
11.2 layers, 90 degrees.

Table 11 shows the figure 8 turning test (Note) for these tires: Pass or fail is determined by 800 figure 8 turns.

The figure 8 turning durability, which involves repeatedly making sharp turns and traveling in a figure 8 pattern, is
Only the tire of the present invention exceeded the passing line of 800 times. This shows that even though the tires have the same strand strength, there is a large difference in toughness, so the tires of the present invention are both excellent in both strength and toughness and have good durability.

[Effects of the Invention] As described above, this invention maintains high strength by making the steel cord have an iron composition with a higher carbon content of 0.8 to 0.95% compared to the conventional steel cord. , - This is a pneumatic tire with high strength and high toughness steel cord, which has developed toughness by reducing the surface area of the paper.
Productivity can be improved as there is no need for strong wire drawing as in the past, and since it is made of high-strength steel, it has improved toughness, so the steel cord will not break even when driving on rough roads or making sharp turns. Furthermore, it is a tire with excellent durability and safety, as it can be used in areas where large deformations occur in the tire.

Claims (3)

[Claims] (1) In a pneumatic tire at least partially reinforced with steel cords, most of the wires forming the steel cords are made of iron material with a carbon content of 0.80 to 0.95%, and the wire strength and aperture are The toughness expressed as the product of is 135
A pneumatic tire characterized by: (2) A pneumatic tire which is a radial tire using the steel cord according to claim 1 in a belt layer. (3) A pneumatic tire which is a radial tire using the steel cord according to claim 1 in its carcass layer.