JPS58161605A - Radial tire for heavy vehicle - Google Patents

Abstract

PURPOSE:To improve the unbalanced abrasion resistance by providing two tread rubber layers made of rubber components with different tangential losses and by using a specific size of the main groove of the tread in a radial tire provided with two breaker layers and a carcass layer. CONSTITUTION:Two tread rubber layers are arranged around at least two breaker layers 14 crossing with each other at a small angle in relation to the peripheral direction of a tire. At least one zigzag main groove 1 is formed on the cap tread portion of these rubber layers, and the groove width 9 of this main groove 1 is made 2-10% of the tread width, the amplitude 10 is made 15-50% of the groove width 9, and the pitch length 11 is made 60-220% of the groove width. A bubber component with the maximum extension of 490% or more when it is broken at 100 deg.C is used for the cap tread portion, and a rubber component with a lower tangent loss as compared with said rubber is used fro a base tread portion 12, and a rubber component with a further lower tangent loss is used for the cushion rubber 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic radial tire for heavy vehicles such as trucks and buses that has improved uneven wear resistance.

Pneumatic tires for vehicles have many advantages over bias tires, such as wear resistance, wet resistance, and puncture resistance, so they are ideal for paved roads and expressways. Therefore, its use has been rapidly expanding in recent years.

For such high-speed roads, riff-type tires are used in which the tire tread surface has a zigzag pattern rift in the circumferential direction, taking into account traction, braking performance, general wear resistance, and heat resistance. I'm in the middle of the day.

Such ribs are normally continuous in the circumferential direction of the tire, but sometimes they are separated by grooves along the width direction of the tire, making them discontinuous in the circumferential direction.

It has become known that when pneumatic radial rib type tires for heavy vehicles are continuously driven in a straight line over long distances at high speeds, uneven wear, that is, railway wear, which has never been seen before, occurs. This railway wear refers to the convex portion of the circumferential rib 2 that extends in the width direction of the tire T toward the tread main groove 1 that extends in a zigzag shape along the circumferential direction of the tire T trend, as shown in Fig. 1. Uneven wear occurs locally from area A near the apex of No. 3, and this is promoted until a step with width W appears in the cross section as shown in Fig. 6, and this uneven wear area > 2 After that, A gradually increases as the mileage (number of houses) increases, and eventually connects with the adjacent area A and continues on the circumference of the tire T, and the step and width W further increase as the mileage increases. Such uneven wear is generally called railway wear, and the resulting shoulder sagging of the tread main groove 1 not only makes the overall appearance of the tire T unsightly, but also damages the ridgeline of the rib 2 divided by the tread main groove 1. This uneven wear occurs only near the top of the convex part 3 of the circumferential rib 2 which forms a zigzag shape. The concave corner 4 of the circumferential rib 2 facing in the width direction of the tire T is not the starting point, but as uneven wear progresses, eventually the corner 4
The railway will also be affected by railway wear.

This railway wear is a peculiar phenomenon that occurs when 5 + J type tires are used for continuous high-speed running, using metal cords with extremely high rigidity as belt reinforcement materials, and are unique to low-speed and intermittent running such as on general roads. Due to the fact that this phenomenon is less likely to occur when the vehicle is used on rough roads with a high degree of wear, the cause of this is that the convex portion 3 side of the circumferential rib 2 that extends in the width direction of the tire T toward the tread main groove 1. It is said that this is due to the fact that the area near the peak of the vehicle is fully concentrated in stress during continuous high-speed running.

From this point of view, attempts have been made to improve the shape of the tread pattern.

For example, a method of reducing the amplitude and circumferential pitch of the main grooves arranged in a zigzag manner in the circumferential direction of the tire, that is, reducing the shape of the main grooves to be close to straight grooves, is a method for treading as described in Japanese Patent Application Laid-Open No. 52-44904. A method of providing a thin stress relaxation groove 5 independent of the groove in the circumferential rib as shown in FIG. Nearby, the third
As shown in the figure, there is a method of attaching a stress relieving rib 7 that forms the entire part of the tread together with the circumferential rib across a separation groove 6 that is substantially parallel to the rib ridgeline near the apex.

However, improving the tread pattern shape such as the stress relief grooves 5 and the stress relief ribs 7 alone cannot completely reduce railway wear.Also, railway wear can be improved by making the tread pattern closer to a straight groove shape, but the tire At present, this method cannot be implemented because the wet performance, which is one of the most important required characteristics, deteriorates.

In view of the current situation, the present inventors conducted detailed research from both the compounding and tread pattern aspects in order to completely sacrifice the wet performance of heavy-duty radial tires, and found that when a natural rubber compound composition is applied to tread rubber. Tread pattern shape (zigzag shape other than straight groove)
Although railway wear occurs regardless of the conditions, the SBR blend composition can effectively prevent railway wear within a certain tread pattern shape range, and the object of the present invention can be advantageously achieved. Ta.

That is, the single-load pneumatic radial tire of the present invention is a radial tire reinforced with at least two layers of breakers and at least one carcass layer that intersect with each other at a relatively small angle with respect to the tire circumferential direction. , the tread rubber layer disposed outside the one layer of the player is composed of two layers, and the cap tread section disposed outside the crown section has at least one zigzag-shaped main groove continuous in the tire circumferential direction on its tread surface. As shown in FIG. 4, the groove width 9 of the main groove is 2 to 10 inches of the tire tread width, the amplitude 10 is 15 to 50% of the main groove width 9, and the pitch length 11 is 2 to 10 inches of the tire tread width. The width is in the range of 60 to 220% of the width 9, and the cap tread portion contains 30 to 70 parts by weight of the styrene-butadiene copolymer out of 100 parts by weight of the rubber component, and the extracted amount is 10% by weight or less. A rubber composition having a maximum elongation at break at ℃ of 490% or more is disposed, and a composition having a lower breakage loss than the cap tread rubber, preferably 70%, is placed in the base rubber part inside the cap tread part. A composition having the following loss cut-off is arranged so as to cover the entire outer width of the breaker layer in the tire radial direction, and a cushion rubber having a loss cut-off lower than that of the rubber layer constituting the breaker layer, preferably 50% It is characterized by arranging cushion rubber having the following loss cut.

Furthermore, as the compounding composition of the cap tread rubber part, the styrene-butadiene copolymer is 40 to 60 parts by weight out of 100N parts of the rubber component, and the extracted amount of vulcanized rubber is 8 parts by weight.
In the following, it is more preferable that the maximum elongation at break at 100° C. is 510% or more.

Natural rubber (N
R) and styrene-butadiene! ! Combined rubber (SBR
) When the amount of SBR in the blend is 30 parts by weight or more based on 1001 parts of the rubber component, railway abrasion properties are significantly improved. Moreover, this effect can be achieved by using some or all of natural rubber or other diene rubbers such as polybutadiene rubber, polyisofrene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene-diene terpolymer copolymers. The effect can also be achieved by substituting one or more types. This SBR is 30 parts by weight or more (hereinafter referred to as S
Although it is not clear why railway wear is rapidly improved when using a BR blend composition, one factor may be that the state of dispersion of SBH in the rubber changes. The amount of SBH to be blended is 70 parts by weight or less in order to suppress heat generation, which will be described later.

In addition, suppressing the amount of cap tread rubber extracted also contributes to improving railway wear.

However, the railway wear improvement effect obtained by reducing the extraction amount to 10% by weight or less is exhibited only when 5BRk is blended as described above. In the present invention, the carbon black used for the cap tread is lA30.
(q/f), a furnace black with a DBP of 100 (m//100 f) or more is preferable, and an IA of 120 (
(2)/f) or more is even more preferable.

The groove width 9, amplitude 10, and pitch length 11 of the tread main groove 1 when the SBR Friend blended composition is applied to the tread rubber will be described in detail below.

If the groove width 9 is less than 2% of the tread width, it will be difficult to drain water when wet, and it will be 10%? If it exceeds 2 to 10% of the tread width, uneven ground pressure will occur between the rib end facing the main groove and the center of the rib, causing uneven wear noise and further reducing wear resistance. , more preferably within 4 to 8 inches of the trend width.

Next, amplitude 10 and pitch length 11 are also superimposed, and if amplitude 10 is less than 15% of main groove width 9 or pitch length 11 exceeds 220% of main groove width, the main groove will have a shape close to a straight groove. This reduces traction and braking performance in wet conditions. - If the universal amplitude lO exceeds 50% of the main groove width 9 or the pitch length 11 becomes less than 60% of the main groove width, railway wear is no longer avoidable even when an SBR blend composition is applied, and therefore it is not an invention. In this case, the amplitude is set to 1 of the main groove width.
5 to 50%, and the pitch length to 60 to 220%. Furthermore, if the main groove width 9 is 4 to 8% of the tire tread width, the amplitude 10 is 25 to 40 inches of the main groove 9, and the pitch length is 100 to 180 inches of the main groove width, the vehicle Even at particularly high running speeds, railway wear can be completely prevented, making it even more useful.
It is advantageous. By arranging one or more narrow grooves between the main grooves or substantially parallel to the main grooves, the wet performance of the tire is improved and the number of main grooves can be reduced.

When applying the above-mentioned uninvented configuration to a radial tire for a single vehicle, the base rubber inside the cap tread part has a pressure loss cutoff compared to the cap tread rubber, so that the tire can handle high speed running. A composition with a low
Moreover, it is necessary to arrange a cushion rubber having a lower pressure loss than the rubber layer that is formed above the breaker.

This is because when using the SBR blend compound composition Citred, it is inferior in heat generation compared to natural rubber compound, and there is a concern that heat-separation may occur. Therefore, it is necessary to prevent heat generation completely. Is required.

In addition to the above, 5BR1r of SBR blend distribution composition
r70! In addition, simply adding 1k of 5BR to the SBR blend composition applied to the cap tread lowers the maximum elongation at break at high temperature, and the above-mentioned in the present invention Within the range of the tread pattern, lift may occur due to driving on rough roads, etc.
(rib melting phenomenon) may occur, so the temperature of the SBR blend composition used for the cap tread should be
It is also important that the maximum elongation at break 't is 49096 or more, preferably 510% or more. This maximum elongation t
Methods to increase the amount of sulfur include (1) slightly reducing the amount of sulfur than the amount normally used, (2) adding softeners and resins, and (3)
Some of the 1S B R warehouses have low molecular weight (viscosity average molecular
・5. (10(1-200.(100, substituted with 15BH, Misaki Kao 2-1°) This will be explained in more detail with reference to Examples below.

]”11 The 9 types in Table 1 as compounding compositions of cap tread rubber,
Various tires shown in Table 4 were made using the rubber composition AIO shown in Table 2 as the coating rubber for the breaker layer and the rubber between the breaker layers, and the 4 types shown in Table 3 as the compounding compositions of the base tread rubber and cushion rubber. . The pace rubber was arranged so as to cover the entire width of the breaker layer outward in the tire radial direction.

The tires are rib-type steel radial tires shown in FIG. 5 with size 10.00R2014PR tire width 180-.Table 4 shows the results of all performance tests performed on these tires.

IA of carbon black HAF used in Tables 1 to 3
is 80(q/f), DBP is 104(d/10(1)
There is. Here, IA refers to the amount of iodine adsorbed by carbon black (unit: yny/l), and the measurement method is JIiSK6.
According to 221. DBP is the carbon black diptyl phthalate (DBP) absorption value (unit: -71009) measured according to the method described in ASTM D-2424.
).

The measurement methods for the evaluation items listed in Tables 1 to 4 are as follows.

<Extracted amount> The tread rubber was cut into cubes of approximately 1 side and weighed approximately 19 cm, and then extracted with acetone continuously for 24 hours using a Soxhlet extractor. /AX100 (! quantity chi).

<Maximum elongation at break> After slicing the tread rubber into approximately 2cm thick, DIN-
It was punched into the shape of No. 3, and all tensile tests were carried out in an atmosphere of 100℃ using an Instron type tensile tester, and the maximum elongation at failure was indicated as "chi". A viscoelastic spectrometer (manufactured by Iwafu Seisakusho) was prepared by simply slicing or punching out a sheet with a thickness of about 2 cm by cutting out the rubber between each layer of the flake, and then punching it into a total length of 20 mm and width of 5 mm. V
iscoelastic Spectrometer T
ype VESA77239) under test conditions: initial strain of 5%, dynamic amplitude of 2%, frequency of 50 Hz, and 25°C.

Wet resistance> 7.25Ky/lr for the test tire? After setting the internal pressure at full strength and installing it on a large truck and adjusting the load so that the wheel load is 2,425 to 4, it is placed on an asphalt pavement for 1 to 2 m.
Sprinkle water in an amount that creates a water film of 500 m, and then
Sudden braking was applied at a speed of Km/H, and the distance until the vehicle stopped, ie, the braking distance, was measured.

It was expressed as an index using the following formula. The higher the index value, the better the braking distance of the test tire (Rail Uniel Wear) 7.25Ky/lr for the test tire? Filled with the internal pressure of
m/h, 40,000 Krn at a vehicle speed of 40 km/h on general roads.
After running, the degree of railway wear was completely measured.

The left and right positions of the tires were changed every 5,000 km. Railway wear occurrence #@ is evaluated by the difference in level (false) as shown in Figure 6) and the railway wear width (b).
It was expressed as an index as shown in the following formula. The smaller the index value, the better.

hO: Step difference WO of tire A1: Railway wear width of tire flat 1 h: Step W of test tire: Railway wear width of test tire (heat resistance) After running for 100,000 km under severe running conditions (internal pressure 7,25 Ky/cd, load @ 2,425 initial +30%), the belt was dissected and cracks at the belt edges were compared.

The index of the results was calculated using the following formula.

Here, the larger the index, the better.

Table 3 Length of belt end cracks in test tires Table 4 Knotted shape and SB with non-inventive configuration
It can be understood that the synergistic effect in reducing railway wear is exhibited only by changing the R blend composition range.

Improving the pattern shape alone has little effect on reducing Lewey wear, but when combined with an SBR blend composition, the effect increases dramatically. (Tire shop 1.2.3
．． 5. Even if the SBR blend composition is applied to the cap tread, increasing the main groove width and amplitude and shortening the pitch length will greatly change the mechanical input to the tread rubber, which will reduce the effectiveness of the SBR rubber. If the heel groove width is decreased, the amplitude is decreased, and the pitch length is increased, the wet skid resistance will be impaired. (Tire width 1°4, see 5.6.) Looking at tires A7 to A12, in order to achieve both railway wear resistance, wet resistance, and heat resistance, the SBR distribution @bond amount is 30 to 7ON. It can be confirmed that this is the department.

Tire & Cap tread is S in the example of 9.13.17
This shows that in the case of a BR blend composition, the effect of the amount of extraction contributing to rail and 7-ray wear cannot be ignored.

Next, fill each of the five tires (Tire A9.10.11.12.17) with an internal pressure of 7.25 Kg/crl, install them on a large truck, and adjust the load so that the wheel weight is 2,425 to 9. After running the test tire at 50,000 m on a semi-rough road, we observed the size of cracks that occurred in the ribs of the tire tread and the condition of the ribs to confirm the durability. The results were evaluated based on the length of cracks that occurred in the tread ribs.

Tires with high maximum elongation at break at 100°C jp6.
9.10.17. The three types of tires had no cracks at all, and Tire A 11 also had a small average crack length of 51,111 mm, but Tire Shop 12 had cracks with an average length of 40+ m, and some ribs were peeled off.

Tire flatness 9.10.11.17. Excellent railway abrasion durability can be achieved only when the maximum elongation at high temperature fracture is 490% or more, such as f1. An FC high-speed rib type radial tire can be obtained without sacrificing other performance.

As described above, by the present invention, for the first time, a dramatic improvement in railway wear, which was considered difficult in the past, has been achieved.

[Brief explanation of drawings]

Fig. 1 is a partial plan view of a conventional pneumatic radial rib tire for one vehicle; Figs. 2 a - d are explanatory views of stress relief grooves independent from the main grooves arranged in a zigzag pattern on the tread of the tire; Fig. 3 is an explanatory diagram of separation grooves and stress relief ribs independent of the tread grooves of the tire, Fig. 4 is a partial plan view of the tire to explain the trend grooves of the uninvented tire, and Fig. 5 is an illustration of the uninvented tire's trend grooves. A cross-sectional view of the left half of m tires, and Fig. 6 is an explanatory diagram of one occasion when railway wear occurs. 1... Tread main groove 2... Circumferential rib 3...
Overhanging convex portion 4... Corner 5... Stress relaxation groove
6... Separation groove 7... Stress relaxation rib 8... Narrow groove 9... Main groove width 10... Amplitude 11... Pitch length 12-Base tread rubber 13... Cushion rubber 14 ...One layer of breaker 15...Rubber between one layer of breaker h...Step W...Railway wear width Patent applicant Brideston Tire Co., Ltd. Representative Patent Attorney Hide Kume - Representative Patent Attorney Etsu Suzuki Figure 1 Figure 2 a b c d Figure 3 Figure 4 Figure 5 Figure 4

Claims (1)

[Claims] 1. Reinforced by at least two breaker layers intersecting each other at a relatively small angle to the tire circumferential direction and at least one carcass layer disposed at substantially 90° to the tire circumferential direction. In a radial tire, there are two tread rubber layers arranged outside the one layer of the breaker.
The cap tread portion, which is arranged on the outside of the crown portion, has at least one zigzag-shaped main groove continuous in the tire circumferential direction on its tread surface, and the groove width of the main groove is 2 to 10 times the width of the tire tread. %, and the amplitude is 15 to 5 of the main groove width.
0% and the pitch length is in the range of 60 to 220% of the main groove width, and the cap trend portion contains 30 to 701 parts by weight of the styrene-butadiene copolymer out of 100 parts by weight of the rubber component. A rubber composition having an extraction amount of 101% or less and a maximum elongation at break of 490% or more at 100°C is placed on the base rubber part inside the cap tread part compared to the cap tread rubber. The breaker layer is composed of a composition having a low pressure loss and is arranged so as to cover the entire outer width in the radial direction of the tire, and a cushion rubber having a pressure loss that is lower than that of the rubber layer constituting the breaker layer is further arranged. 1
Pneumatic radial tires for vehicles. 2. Apply 100% of the rubber component to the cap tread rubber part.
ii The styrene-butadiene co-N@ body is 40~
60]ii parts, the extraction amount is 8% by weight or less, and 10
A rubber composition having a maximum elongation at break of 510% or more at 0° C. is entirely disposed, and the rubber layer surrounding both end portions of the breaker is 50% or less compared to the rubber layer constituting the breaker. A nitrogen-filled tire for a vehicle according to claim 1, characterized in that a rubber layer having a pressure loss of . 3. At least one narrow groove is disposed between the main grooves and/or between the main groove and the tread edge, the groove width being such that the grooves come into contact with each other during load transfer and being substantially parallel to the main groove. A pneumatic tire for a vehicle as described in Scope 1.