JPS609923B2 - Radial tires for small trucks - Google Patents

Description

Detailed Description of the Invention The present invention relates to a radial tire for type 4 trucks.Details: 0 is a radial tire for small trucks having two or more types of tread rubber layers for the purpose of improving heat generation durability, and is mainly used for so-called light van radial tires. It is related to tires.

As shown in Fig. 1, the radial tire for small trucks has a pair of bead wires 1, and organic fiber cords such as polyester, 6-nylon, 6-6 nylon, etc. fixed to the bead wires and arranged substantially parallel to the tire radial direction. a carcass 2 comprising a carcass 2, a tread 5 disposed astride between sidewalls 4, and at least one layer of steel cord or glass fiber cord or an aromatic polyamide fiber cord layer embedded in said tread. Consists of 3 breakers.

Passenger car tires mainly focus on vibration/ride comfort, handling stability, wet skid performance, and high-speed running performance, while large truck tires mainly focus on heat generation durability because of their heavy load burden.

Light truck tires are located between the above two,
In particular, light vans are used in the same way as passenger cars, so heat generation in the tires while driving is a problem.

The present invention improves the heat generation durability of the above-mentioned radial tire for light vans while maintaining vibration/riding comfort, steering stability, and wet skid performance.

That is, the tread rubber has a two-layer structure, and the cap tread uses rubber with good vibration, riding comfort, steering stability, and wet skid properties, and the paste tread rubber uses rubber with low heat generation. Since paste tread rubber is not exposed to the tire surface and makes contact with the ground even at the end of its life, we decided to use a rubber with low heat generation without considering the road surface characteristics.

2a and 2b show partial cross-sectional views of the tread portion of the radial tire according to the present invention, where 3 is the breaker, 5 is the tread groove, A is the cap tread rubber tB is the tread groove, and A is the cap tread rubber tB is the tread groove. - Stread rubber, 1 is the wear limit position (for example, according to JATMA (Japan Automobile Tire Association), the wear limit for small truck tires during high-speed driving is specified as 24 skins above the groove bottom. ，
This is the boundary surface of B.

At this time, the position of the boundary surface 0 of the two-layer tread is substantially closer to the breaker 3 than the wear limit position 1. Note that the above wear limit is determined so that if the remaining groove is less than this, the wet skid characteristics will be greatly deteriorated, so the product should not be used in such a state. In this way, even if the paste tread rubber is a compounded rubber that aims to produce significantly lower heat generation, the paste tread rubber will not be exposed to the surface if the wear level does not reach the wear limit. Since wet skids do not cause significant deterioration, there is no problem in terms of safety.

In the tire manufacturing process, it is not possible to clearly position the boundary surface due to rubber flow, but even if the top edge of the boundary surface exceeds the wear limit position, the maximum height h that exceeds the tread groove The depth shall not exceed 10% of the day.

That is, hSO. 1×day (see Figure 3). Note that the middle day in Figure 3 indicates the tread groove depth, and h indicates the maximum height at which the top edge of boundary surface 0 exceeds the wear limit position.Other figures 2 and a
The same reference numerals as in FIG. 2b indicate the same parts. Now, another characteristic required of paste tread rubber shoes to reduce heat generation is that the tread rubber should not cause cracks in the groove sole because it may be exposed on the groove sole surface. Therefore, the polymer used for penis tread rubber should contain at least 5 parts by weight of a polymer selected from the group of natural rubber, isoprene rubber, or butadiene rubber, alone or in a mixture, in order to exhibit low heat generation characteristics. A mixture with styrene-butadiene rubber or the like can also be used as the polymer.

In this case, in order to suppress cracks in the tread groove bottom, it is desirable to use a polymer blended with 15 parts by weight or more of butadiene rubber. If the amount of carbon black is less than 3 parts by weight, the effect of suppressing cracks at the bottom of the groove is small; if it is more than 4 parts by weight, the loss modulus E'' becomes large, which is not suitable.

On the other hand, cap tread rubber is intended for wear resistance, wet skid properties, and handling stability, and is usually made of natural rubber, isoprene rubber, butadiene rubber, or styrene-butadiene rubber alone or in combination. At least 45 parts by weight of carbon having a diameter of less than 35 h is blended with respect to 10 parts by weight of rubber.

Also, the loss modulus of elasticity of cap tread rubber is 7 to 15.
It is in the range of k9 style. If the weight is less than 7kg, wear resistance, wet skid property, etc. will be impaired, while if the weight is less than 15kg/
In the case of more than , the heat generation performance is not satisfactory.

The loss modulus E is the viscoelasticity of paste red rubber.
'' shall have a value of 20 to 50% of the cap tread rubber.

Further, the value of the loss compliance E''/(E*)2 of the paste tread rubber is 60% or less of the loss compliance E''/(E*)2 of the cap tread rubber.

Examples will be described below.

Example 1 A steel flaker tire with 18 stations, 1 mountain, and T-spot R was manufactured with the tread composition shown in Table 2 and the combinations shown in Table 1, and this was carried out under conditions of a speed of 80 items/h and a load of 850 kg. When a drum running test was carried out and the saturation temperature was measured, the tire of Comparative Example 1 had a temperature of 80°C, whereas the tire of Comparative Example 1 had a saturation temperature of 80°C.
Example 1, which is a layered tread, had a heat resistance of 66.0, and the heat generation property was significantly improved.

In Table 1, the paste tread rubber of Example 1 was used in an amount of 4% by volume based on the total tread rubber.

Table 2 Note 1) The dynamic properties of rubber were measured using an Iwamoto Seisakusho viscoelastic spectrometer with a sample length of 3 mm, sample width of 4 mm, and sample thickness of 1.5 mm.
Measurements were made under the following conditions: 10Hz frequency, 2% amplitude, and 10% initial strain.

Furthermore, the wear amount at the tread center position of the tires of Comparative Example and Example 1 is expressed as a relative value after approximately 30,000 short runs on an actual road, with the value of Comparative Example being 100, and the value of Example 1 is 100. It was equivalent to the example.

In addition, when braking distance was measured in an actual military braking test, when the value of the comparative example was taken as 100 and expressed as a relative value, Example 1 had a distance of 1.
00, and no deterioration in wet skid property was observed.

According to the radial tire for light vans of the present invention as described above, heat generation durability can be improved without impairing vibration riding ground, wet skid property, and steering stability.

0 Brief explanation of drawings Figure 1 is a cross-sectional view of a radial tire for a light van, Figure 2 is a cross-sectional view of a radial tire for a light van.
Both figures are cross-sectional views of the tread portion of the radial tire for light vans according to the present invention. In the case where the boundary surface between the layers is on the tread groove surface, FIG. 3 illustrates a partial cross-sectional view of the case where the boundary surface between the two layers of the tread is not flat.

1... Beat wire 1, 2... Carcass, 3... 0... Breaker, 4... Side wall, 5... Tread, 6...
...Tread groove, A... Cap tread rubber, B... Paste tread rubber, 1... Wear limit position, D...
...Boundary surface of two-layer tread, H...Tread groove depth, h...Height at which the top of the boundary surface of two-layer tread exceeds the wear limit position.

oh! Zusaba 2 (of Mulberry 2 (b) Figure 3

Claims (1)

[Scope of Claims] 1. A pair of bead wires, a tread arranged between a carcass and a sidewall consisting of an organic fiber coat fixed to the bead wires and arranged substantially parallel to the tire radial direction, and a tread between the carcass and the tread. In a tire comprising a breaker including at least one steel cord layer, glass fiber cord layer or aromatic polyamide fiber cord layer embedded therebetween, the tread is comprised of two layers: a cap tread rubber and a base tread rubber. , the loss modulus E'' of the cap lead rubber is 7 to 15.
kg/cm^2, and the loss modulus E'' of the base tread rubber is equal to the loss modulus E'' of the cap tread rubber.
The loss compliance of the base tread rubber E″/(E*)^2 is in the range of 20 to 50% of the loss compliance of the cap tread rubber E″/(E*)
A radial tire for small trucks characterized by being 60% or less of ^2. 2 Base tread rubber is natural rubber, isoprene rubber,
The radial tire for small trucks according to claim 1, comprising 50 parts by weight or more of a polymer selected from the group of butadiene rubbers, alone or in a mixture. 3. The radial tire for small trucks according to claim 1 or 2, wherein the base tread rubber contains 30 to 40 parts by weight of reinforcing carbon black having an average particle diameter of less than 35 mμ. 4. The radial tire for small trucks according to claim 1, wherein the boundary between the two layers of cap tread rubber and base tread rubber is located substantially closer to the breaker than the wear limit position.