JPS602963Y2 - Bias pneumatic tires for small trucks - Google Patents

Description

[Detailed description of the invention] This invention relates to a bias pneumatic tire for light trucks, and in particular aims to prevent separation between carcass plies and improve ride comfort in light truck tires equipped with a bias carcass made of polyester cord. .

Light-duty truck tires are a type of heavy-duty tires to which high internal pressure and high loads are applied, and in accordance with the above-mentioned requirements, nylon cords, which are extremely strong, have traditionally been used as tire carcass reinforcing materials.

However, in recent years, as paved roads have become complete and expressways have developed, opportunities for driving at high speeds have increased, and the problem of poor riding comfort due to the flat spots peculiar to nylon carcass has been pointed out.

A flat spot is when the temperature of a tire increases significantly (100-140'C) due to the heat generated by the tire itself when the tire is running at high speed. As a result, the carcass cord held in a relaxed (contracted) state, especially within the contact patch, is locally set, creating a flat portion on the circumference of the tire with a length corresponding to the contact patch, which is a known phenomenon.

This flat spot will eventually disappear naturally as the tire temperature rises while driving, but during the period leading up to its disappearance, abnormal vibrations will occur and cause discomfort to the driver, and this is due to the large stretch of the cord. This is a phenomenon specific to tires that use nylon cord for the carcass.

In order to eliminate the deterioration of riding comfort caused by such abnormal vibrations,
Polyester cords with low cord elongation, that is, high tensile modulus, have recently attracted attention as carcass reinforcement materials. However, when polyester cords are used in bias structure carcass for heavy loads, the deformation of the carcass During pantograph movement of adjacent ply cords crossing in different directions (a phenomenon in which the included angle of the cords that cross each other changes in proportion to the amount of deformation), the coating rubber interposed between the plies is affected due to the high modulus of the cords. The burden of absorbing strain (shear strain between plies) becomes high, and therefore separation failure between the plies due to coating rubber fatigue is likely to occur, particularly in the crown portion of the carcass.

This invention proposes a bias pneumatic tire for light trucks that advantageously improves the disadvantages peculiar to bias structure tires using such polyester cords in the carcass.

This idea is based on a pair of bead parts, a side part that runs between both bead parts, and a tread part that spans between both side parts, and each of these parts is made of multiple plies made of polyester cords that are crossed and overlapped. In a carcass-reinforced tire, each of the above cord plies has a 100% elongation modulus of 20 to 50 kg/al! 1 for test pieces according to JISK6301.
(It has physical properties such that the crack length velocity does not exceed 5 x 10-4 m/cycle when a stretching energy of P9/mm is applied periodically, and is 30 to 60% of the cord diameter of the ply.
This is a bias pneumatic tire for small trucks that is coated with coating rubber of a corresponding gauge to suppress and prevent pantograph movement between overlapping cross plies that occurs when the tire is deformed under load.

Regarding the crack growth rate, the periodic tensile conditions of the test piece are in the range of 300 to 5 strokes per minute, the temperature condition is room temperature, and as an initial cut, a cut of 1 mm length is made at one end in the center of the test piece in the tensile direction. shall be applied across the entire thickness of the test piece.

This will be explained below using the drawings.

FIG. 1 is a cross-sectional view of a pneumatic tire according to this invention.

The tire 1 consists of a pair of bead parts 2, a side part 3 connected to both bead parts, and a tread part 4.

For convenience, only the outline is shown in the right half of the figure, but it goes without saying that it is symmetrical with respect to the equatorial plane 0-0.

5 in the figure is a shoulder.

Each of the above-mentioned parts of the tire is reinforced with a carcass 6, which in this example comprises three inner plies 6-1 of the four 1500 d/2 polyester cord layers that constitute the carcass 6.
6-2 and 6-3 are wound around the bead wire 7 from the inside to the outside, and the remaining outer ply 6-
4 is an end stop at the inner tip position of the bead portion 4.

Each carcass ply has cords that are inclined in the range of 25° to 45° with respect to the equatorial plane 〇-〇, and intersect in different directions between adjacent plies.

Each of the carcass plies 6-1 to 6-4 is coated with a coating rubber C having a gauge corresponding to 30% to 60% of the cord diameter on both sides so that the cords do not contact each other when overlapped. In the case of 1500d/2 code, there is an interposition of 0.27a to 0.4rIrlft (twice the above value between the plies).

In this invention, this coating rubber C is 100%
The tensile modulus is in the range of 20 to 50 kg/cwt and 1σg/cwt is applied to the test piece according to JIS K6301.
The material shall have physical properties such that the crack growth rate does not exceed 5 x 10-'/cycle when rigid elongation energy is applied periodically.

A rubber having such physical properties has an average iodine adsorption amount of 4 parts per 100 parts by weight of natural rubber with at least 3 parts of natural rubber.
0 to 90yny/f/ and average DBP oil absorption of 60
20 to 8 parts of furnace carbon black of ~140J/100!7 and other softeners according to compounding conventions,
It is vulcanized by adding an organic vulcanization accelerator, sulfur, etc.

FIG. 2 shows a more preferred embodiment in which squeegee rubber S is additionally arranged between the carcass plies in the crown portion of the carcass 6 extending between both shoulders 5.

Each squeegee rubber Sl, S2. and S3 are shown with dashed lines for convenience of identification, but these squeegees have cord diameters of 0.3 to 0. It is more preferable to use a sheet-like rubber having a hollow gauge and continuous within the cross section of the tire, and having the same physical properties and composition as the carcass coating rubber.

Note that numeral 8 in the figure indicates a breaker that is preferably used in this type of tire, but it may be omitted in some cases.

Since the tire of this invention uses polyester cord as a carcass reinforcement material, it is completely free from the effects of flat spots that impair the ride quality during the initial period of driving after parking, and is unprecedented for this type of tire. By using a coating that has relatively high modulus and excellent physical properties in terms of tear resistance, separation failure between the plies of the carcass centered on the crown part of the carcass can be effectively suppressed, and sufficient durability can be achieved. It is possible to do so.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a tire showing an embodiment of this invention, and FIG. 2 is a sectional view of a modified example. 2... Bead part, 3... Curved side part, 4... Curved tread part, 6... Curved carcass, 6-1.6-2.6-
3.6-4... Cord ply, C...
coating rubber.

Claims (1)

[Claims for Utility Model Registration] From a pair of bead parts, a side part extending between both bead parts, and a tread part spanning between both sides,
In a tire in which each of these parts is reinforced with a carcass consisting of a plurality of overlapping plies with polyester cords crossed between the plies, each of the above cord plies has a 100% elongation modulus of 9/ai of 20 to 50. Within the range, JISK63
When a tensile energy of 102 fl/m was applied periodically to the test piece according to 01, the crack growth rate was 5 x 1.
It has physical properties not exceeding 0-'mm/cycle and is coated with a coating rubber of a gauge equivalent to 30 to 60% of the cord diameter of the ply to suppress pantograph movement between the overlapping cross plies that occurs when the tire is deformed under load. A bias pneumatic tire for small trucks characterized by the following: