JPS5938102A - Radial tire - Google Patents

Abstract

PURPOSE:To improve the operating, driving and braking properties and stability of a very flat radial tire which is for a race and has a prescribed flatness ratio, by prescribing the elemental wire diameter, elemental wire number, break elongation, tensile strength and suppleness of the steel cord of the belt layer of the tire. CONSTITUTION:The steel cord of the belt layer 6 of a very flat radial tire 1, which is for a race and has a flatness ratio H/W of 0.25 to 0.75, is made by twisting together six to twenty-one elemental wires of 0.06 to 0.10mm. in diameter d. The break elongation lambda, tensile strength delta and suppleness S of the vey-small- diameter steel cord are set at 3% or less, 200kg/mm.<2> or more and 500mg.cm or less, respectively. According to this constitution, the durability and cornering operation stability of the tire 1 are improved, and its weight is reduced so that its driving and braking properties are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire, particularly an ultra-flat radial tire for high-speed running (for racing) in which the ratio of tire cross-sectional height to tire maximum cross-sectional width is in the range of 0.25 to 0.75. Regarding improvements.

In general, this type of ultra-flat tires for high-speed running are not used for long periods of time under mild conditions like tires for general passenger cars or trucks, but are used for extremely harsh conditions such as for racing. It is intended for use for a relatively short period of time. Therefore, this type of tire is required to have higher levels of characteristics such as maneuverability, stability, acceleration, and drivability, as well as durability during high-speed running. if,
If even one of these characteristics does not reach a certain level,
Severe destruction will occur in a short period of time.

Conventionally, various proposals have been made to improve the running performance of this type of tire. For example, various studies have been carried out on bias structures, but since they have matured considerably, characteristics such as cornering stability, braking, and drivability have to be improved compared to bias structures. The radial structure, which is superior in all aspects, has recently attracted attention.

However, adopting a radial structure does not lead to improved performance in all respects and poses major problems. In other words, this type of tire is required to reduce weight, but if a radial structure is used, the number of component parts increases compared to a bias structure, which increases the weight, which affects the tire's driving and braking performance. In addition, the radial structure has a characteristic drawback in that the behavior after the maximum cornering force is exceeded is unstable and sudden changes occur, making it difficult to control.

The latter cause is caused by a change in the ground contact area during cornering, as shown in FIGS. 1 and 2, or by a reduction in the ground contact area, which is larger than the bias. In addition, Fig. 1 shows the change in the set contact surface of a radial tire during cornering, and Fig. 1 (a) shows the deformed state in the first
Figure (1)) shows the ground contact shape. Figure 2 shows the changes in the set contact surface of the bias tire during cornering. represents the cornering state, Q represents the straight-ahead state, father represents the straight-ahead direction, and Y represents the cornering direction.

Various studies have been conducted to improve these shortcomings of radial tires, and the focus has been on how to increase the contact area with the road surface, that is, how to increase the contact area without decreasing it, in response to external force changes during load transfer. Narrowed down. For this reason, the following measures were adopted.

(+1) One way is to widen the tire width9 and use a tire shape with a flattened cross section to ensure ample ground contact area. There are limitations and it is not possible to improve the ground contact area change during cornering.

(2) The second is an attempt to increase the tire outer diameter and secure the ground contact area in the tire circumferential direction.
Like the former, this also has a limit due to the relationship with the car body, and it is not possible to drastically reduce the change in ground contact area during cornering.

(3) Thirdly, an attempt was made to lower the rigidity from the beat section to the zyde wall section to ensure familiarity with the road surface and secure ground contact area. Although this is confirmed to be effective against changes in the ground contact area during cornering, the cornering force decreases and the marginal performance decreases, and in order to compensate for this, changes in the suspension of the vehicle body (
This is not sufficient because the camber, toe-in is increased, and the spring is made harder), which reduces straight-line driving performance.

(4) The fourth approach is to reduce the rigidity of the tread surface so that the tire follows changes in external force, thereby increasing the contact area and reducing changes in the contact area during cornering.

However, the belt material conventionally used for this type of tire consists of steel wires with diameters of 0.22, 0.25, 0.15, etc. in a configuration of 1 x 5.3 x 4. Therefore, tires using steel belts made of these strips have high tread rigidity (belt rigidity) and have the above-mentioned drawbacks. In addition, methods such as reducing the number of cords have been adopted as a means of setting the tread rigidity (belt rigidity) low with current belt materials, but there are problems with durability, and there is no way to solve the aforementioned drawbacks. Although this is a positive trend, the effect is small.

In addition to steel, materials used as belt materials for general tires, such as aromatic polyamide fibers and rayon, were also used, but due to their low elastic modulus, tire deformation was large at high speeds, and there were also problems with durability. Yes, if the outer diameter grows thicker, maneuverability at high speeds1. The disadvantage is that the drive performance is reduced.

Therefore, the present invention has been made by focusing on the fourth means described above, and is a steel cord with a small wire diameter (0.06 to 0.10 mm, 1% constant) as a belt base for a tire with a radial structure. By using a radial tire, we can improve maneuverability and stability during cornering, which is the biggest drawback of this type of tire, and also reduce the weight required for this type of tire, in other words, improve driving and braking performance. The purpose is to provide tires.

For this purpose, the present invention comprises a pair of left and right bead parts, a pair of left and right sidewall parts connected to the bead parts, and a tread part located between the pair of left and right sidewall parts, and a tread part located between the pair of left and right sidewall parts. A carcass layer is installed between the parts,
In the radial tire in which a belt layer made of steel cord is provided on the carcass layer of the tread portion, the steel cord is composed of 6 to 21 strands with a strand diameter of 0.06 to 0.10 mm, and , elongation at break is 3% or less, tensile strength is 200K9/mi or more, bending resistance S is so
omy-α or less.

Hereinafter, the present invention will be described in detail with reference to the drawings. In addition,
This example is an example of a radial tire for high-speed running (for racing).

As shown in the meridional cross-sectional view of FIG. 3, the radial tire 1 for high-speed running includes a pair of left and right bead portions 2゜2', and a pair of left and right sidewall portions 6 connected to the bead portions 2, 2'.
, 6', and a substantially cylindrical tread portion 4 located between the pair of left and right zyde wall portions 6, 6'. A pair of left and right bead wires 7 arranged at the bead portion 2°2'
．． A rubber filler is sandwiched between the bead wires 7 and 7' and is located on the bead wires 7 and 7'. Tread section 40 carcass layer 5
A belt layer 6 is provided on top.

The radial tire 1 has an aspect ratio (tire cross-sectional height H/tire maximum width W) of 0.25 to 0.75, and is extremely flat. If H/w is less than 0.25, molding becomes difficult;
If H/w exceeds 0.75, it is difficult to ensure lateral rigidity and handling stability is not improved, which is not desirable.

The carcass layer 5 is composed of at least one layer, and is made of rubberized reinforcing cords such as nylon cords, polyester cords, rayon cords, and aromatic polyamide fiber cords having an angle of 70° to 90° with respect to the tire circumferential direction. ing. However, the cord angle with respect to the tire circumferential direction is
When the carcass layer is one layer, it is approximately 9σ, and when there are two layers, it is 7σ.
0' to 90''.

The rubber filler 8 preferably has a Shore A hardness of 65° to 95°. If the angle is less than 65°, the lateral rigidity will decrease and the steering stability will not be improved, and if it exceeds 95°, the straightness of the bead portion will decrease and the extrusion processability will also deteriorate, which are both undesirable.

The belt layer 6 is constructed such that two layers of rubberized steel cords inclined at an angle of 15° to 30' with respect to the tire circumferential direction intersect with each other.

Additional layers may be provided at the end of the belt layer or on the entire belt layer, or
Alternatively, it is also possible to have three or more layers.

The steel cord constituting the belt layer 6 is important for improving steering stability and driving/braking performance.
Consisting of 21 strands twisted together, this ultra-fine steel cord has physical properties such as elongation at break λ of 3% or less, tensile strength δ of 200 KV/, d or more, and bending strength S of 500 m19・α
These are as follows. If the diameter d of the strands is less than 0.06, a large number of strands will be required to ensure the required strength as a belt material, resulting in a decrease in durability, which is undesirable. If the number n' of strands is less than 6, it is not preferable because the wires tend to break due to insufficient strength and the durability decreases. Then, the wire diameter d and the number of wires n are each 0.10+n
If the number exceeds 21, the steering stability during cornering will deteriorate, the weight will increase, and driving and braking performance will deteriorate, which is not preferable.

Furthermore, if the elongation at break λ exceeds 3, the maneuverability and drivability during high-speed running will decrease, and durability will also decrease, which is undesirable. If the tensile strength δ is less than 200 KVmr/r, the wire may break. This is undesirable because the durability of the Sievert layer, which tends to occur, is reduced, and the bending resistance S is 500111p.
If it exceeds -cm, the flexibility of the belt layer will be lost and the steering stability during cornering will deteriorate, which is not preferable. The bending resistance S is a standard that indicates the flexibility of the steel cord (the smaller the value, the more flexible it is), and is based on JIS L 107.
9 (1976) using the following formula.

Bending resistance 5- RG X (aWa+bWb+cWc) x J2X O,
306 (m9.cm), RG: Scale values a, b, c when measured with a Gurley tester: Distance between the load attachment hole and the fulcrum (crn) W
a, Wb, WC: Each load applied to the mounting hole (7)
l: Length of test piece (steel coat) Crn) Measure with one test piece.

When the number of strands n is 9, this steel coat is, for example, 3
It is preferable to use a structure in which three strands made by interchanging three wires are further twisted together as shown by ×3.

And the number of cords of this steel cord is 30~
70 pieces 15Qmm (measured at right angles to the cord direction.

) is preferable. If the number is less than 30, the strength of the belt layer will decrease, and the wires will easily break, which will not only reduce durability but also reduce steering stability. This is not preferable because it tends to occur and the durability decreases.

Examples are illustrated below.

Example The physical properties of the cord material of the belt layer were compared.

The results are shown in Table 1 below.

(Margins below this page) As shown in Table 1 above, it can be seen that the steel cord used in the present invention has the flexibility of a fiber material, and maintains the strength of a general steel wire.

Next, Table 3 shows the static ground contact profile evaluation results for the radial tire according to the present invention (Example 1) and conventional radial tires (Conventional Examples 1 to 4) having the configurations shown in Table 2 below. , Table 4 shows the evaluation results of the ground contact shape set during cornering indoors, Table 5 shows the actual vehicle evaluation results of ramp time and failure status on the circuit, and the driver's feeling results on the circuit (actual vehicle evaluation results)
are shown in Table 6.

(Margins below this page) As is clear from the above results, the radial tire of the present invention has improved characteristics near the limit, which is a drawback of this type of tire, compared to the conventional tire.

That is, cornering stability near the limit is improved without significantly reducing the ground contact area, and furthermore, the weight reduction and driving/braking performance required for this type of tire are achieved.

Therefore, the present invention is applicable not only to high-speed racing radial tires but also to radial tires for general passenger cars.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the change in the set contact patch during cornering of a conventional radial tire, Fig. 2 is an explanatory diagram showing the change in the set contact patch during cornering of a conventional bias tire, and Fig. 3 is an explanatory diagram showing the change in the set contact patch during cornering of a conventional radial tire. It is a meridional cross-sectional view of an example of a tire. P... Cornering state, Q... Straight going state, X...
- Straight direction, Y... Cornering direction, 1... Radial tire for high speed running, 2. 2'... Bead portion, 3.
3'...Side wall part, 4...Tread part, 5
...Carcass layer, 6...Belt layer, 7,7'...
Bead wire, 8, 8'...Rubber filler. Agent: Patent Attorney Makoto Ogawa − Patent Attorney: Ken Noguchi Patent Attorney: Kazuhiko Saishita

Claims (1)

[Claims] A carcass layer is installed between a pair of left and right bead portions, a pair of left and right bead portions, a pair of left and right sidewall portions connected to the bead portions, and a tread portion located between the pair of left and right sidewall portions. In a radial tire in which a belt layer made of steel cord is provided on the carcass layer of the tread portion, the steel cord has a wire diameter of 0.
06~0.10mm wire 6~. Consisting of 21 pieces,
And elongation at break is 3% or less, tensile strength 200 K9
A radial tire characterized by having a bending strength S of Ald or more and a bending strength S of 5 oomg-crrt or less.