JPH03220002A - Pneumatic radial tire for irregular ground running heavy-load vehicle - Google Patents

Abstract

PURPOSE:To secure the excellent envelope property and durability by forming a belt with the outermost layer, a protective layer and a master layer made of specific steel cords respectively, and setting the breaking elongation and breaking load of the individual steel cords to specific relations respectively. CONSTITUTION:A belt 6 for reinforcing a tread 2 is constituted of the outermost layer 11, a protective layer 12 and a master layer 13 in sequence from the tread 2 side. The outermost layer 11 is made of steel cords A twisted with filaments with the diameter 0.3-0.5 mm and the tensile apparent elongation within the range 0.4-1.2. The protective layer 12 is made of steel cords B twisted for high elongation. The master layer 13 is made of nonexpansive steel cords C. Characteristics of the steel cords A, B, C are set to satisfy the following relations, i.e., breaking elongation (%): B>A>C, breaking load (kg): C>B>A.

Description

[Detailed Description of the Invention] (Industrial Application Field) Heavy-duty vehicles that travel on rough terrain, such as self-propelled construction machines, use air pumps that are subject to harsh operating conditions under heavy loads on rough terrain. Regarding radial tires, we have improved cut resistance, which is particularly important for this type of tire, along with force resistance and separation properties, and improved belt structure that can improve belt edge separation resistance. The objective is to improve the reliability of pneumatic radial tires for heavy-duty vehicles.

Here, cut resistance refers to the resistance of this type of tire to cuts (ruptures) in or near the tread caused by stepping on sharp, rough protrusions on the ground or sharp fractured edges of rocks. Cut separation is caused by the above cut or by peeling of the tread and belt, which occurs when a part of the red reinforcing belt is reached, due to rust caused by moisture that has entered around the steel cord.
Tread leaving Breaker
(or Belt): TLB) resistance and belt edge separation resistance respectively mean resistance to peeling due to excessive strain or stress near the width end of the belt.

(Prior art) In order to improve the cut resistance of pneumatic radial tires for construction vehicles, a layer of high elongation steel cord, so-called Hi-Eron twisted cord, which has a significantly high elongation at break, is used as a tread reinforcing belt. By placing it on the outermost layer of the ground, when the tread rides on protrusions or rock formations scattered on the ground surface, the ground contact behavior wraps around them (this is called enveloping property).
This arrangement is also useful for protecting the backbone layer of the belt and helps prevent belt edge separation.

However, if there is an impact that exceeds the limit of the enveloping property, or if a small cut flaw occurs even locally, moisture can enter from the ground surface and travel through the high elongation cord, causing rust. This may lead to a decrease in the adhesion between the cord and the rubber, which may lead to cut separation, that is, the above-mentioned TLB.

On the other hand, as a countermeasure against such cut separation, as described in Japanese Patent Application Laid-Open No. 116504/1983 as a "sealed type penetration type cord", there is a method to eliminate the flow of moisture transmitted along the cord. Four attempts were made to use a layer of steel cord as the outermost layer of the belt.

In this case, even if the cut separation is reduced and □, such a steel cord will elongate 1.・Since the amount is much smaller than that of high elongation cord, it is inevitable that the enveloping property is inferior, but the depth of damage caused by cut flaws increases, and the cut penetration resistance worsens.

Furthermore, the outermost layer of the belt disclosed in this publication is set to be narrower than the tread width (62%), and both ends of the main layer of the belt are not protected at all, so belt edge separation also occurs. It is easy to use and may not be practical depending on the conditions of use.

(Problem to be solved by the invention) While properly reinforcing the tread with a belt, it is possible to appropriately secure its enveloping property, improve cut separation resistance under inevitable cut flaws, and furthermore, improve belt edge resistance. It is an object of the present invention to propose a pneumatic ral tire for heavy-duty vehicles running on rough terrain, which has an improved belt structure so as to have separation properties.

(Means for Solving the Problems) The present invention includes a carcass for body reinforcement consisting of a radially arranged rubber-coated steel cord layer spanning a pair of bead cores in a toroidal manner, and a crown portion of this carcass. In a pneumatic radial tire, the pneumatic radial tire is provided with a tread reinforcing belt which is surrounded by a tread reinforcing belt having at least four layers of rubber-coated steel cords, the belt having a wire diameter of 0.
．． Consisting of a single-layer open-stranded cord consisting of multiple filaments with a mark of 3 to 0.5 twisted together, each cord is subjected to stress that occurs under the action of tension, resulting in a virtual stress burden on the filaments that make up the cord. Tensile apparent elongation (PL
E) an outermost layer using steel cord (A) having a content of 0.4 to 1.2%, and at least one layer of high elongation twisted cord adjacent to the outermost layer on the inside in the tire radial direction. A protective layer using steel cords (B) in which the cords of the layer directly in contact with the outermost layer are arranged at an angle opposite to the cords of the outermost layer across the equator of the tire;
A main layer using a steel cord (C) consisting of at least two layers of substantially non-extensible cords adjacent to the protective layer on the inner side in the tire radial direction, and a steel core layer that occupies the maximum width of the main layer. The cord (C) layer has a width narrower than that of the protective layer or the wider steel cord (B) layer, and is arranged so that the cords in that layer and the tire are inclined in the same direction with respect to the equator. Code (A).

(B) and (C') have the following relationship regarding elongation at break and load at break: elongation at break (%) (B) > (A) > (C) load at break (kg) (C) > (B) > (A ) is a pneumatic radial tire for heavy-duty vehicles running on rough terrain.

Here, the tensile apparent elongation (PLE; Pre Load Elongat) is calculated for the outermost steel cord (A).
This is because this cord is made of single-layer open strands, so when tensile force is applied to it, the filaments do not bear any tensile stress until the filaments that make up the steel cord come into contact with each other due to the twisting. This refers to the elongation that occurs in the cord without occurring, and for example, for a steel cord (A) of 1 x 5 and the difference in elongation under a tension of 0.25 kg or the same <
37.00 For R57, steel cord ('A
) can be easily determined by taking the difference in elongation under tension of 15 kg and 0.25 kg in an open-stranded structure of 1 x 5 x 0.5 mm.

The outermost layer of steel cord (A) must be IX5 or 1×4 single layer twisted as described above, and the outermost layer must have an arrangement width of 50 to 80% of the tread width in the tire cross section. Delicious.

Now, the main structure of a pneumatic radial tire for heavy-duty vehicles traveling on rough terrain according to the present invention is shown in FIG. 1 in a sectional view of only the left half.

In the figure, 1 is the body of the tire, 2 is the tread of the tire, 3 is the bead of the tire, 4 is a bead core buried inside the bead 3, and 5 is between a pair of peed cores 3 (the right side is not shown). A carcass for reinforcing the body 1 consisting of radially arranged rubber-coated steel cord layers spanning a toroidal shape, and 6 surrounding the crown portion of the carcass 5 and having at least four rubber-coated steel cord layers. This is a reinforcing belt for the tread 1, which is made of laminated layers.

For the carcass 5, follow the convention. For example, in a tire with a size of ORR18,0OR25, the twisted structure (I X 3 +9 +15) Xo, 23
mm+ I Xo, 15 breaking load 280kg/1
Main elongation at break 2.5% For example, in a tire with a size of ORR37,00R57, the twisted structure (I X a +9 +15)X 7 Xo,
18mm+I XO', 18mm breaking load 1200k
It consists of a rubber coating layer of a steel cord with an elongation at break of 2.5% per piece. is approximately 50% of the tire cross-sectional height SH, and a so-called wire chafer 7 is provided in the winding region along this from the inside of the tire to the outside, and a winding region is placed on the upper core 4 of the tire. Filler rubbers 8 and 9 are respectively arranged to fill the inside of the tube.

Note that 10 in the figure indicates a rim compatible with beat 3.

The belt 6 is a laminate of at least four rubber-coated steel cord layers surrounding the crown of the carcass, or
In particular, in this invention, in order from the tread side, the outermost layer 11
, a protective layer 12 and a main layer 13, and are composed of one or three types of hybrid layers.

The outermost layer 11 of the uni is a single-layer open twisted cord made of steel filaments with a wire diameter of 0.3 to 0.5 mm, which are twisted together.
E) or 0.4 to 1. ．． A steel cord (A) within the range of 2% is used.

Next, the protective layer 12 includes at least one layer of Hi-Eron Keno twist cord arranged adjacent to the inner side of the outermost layer 11 in the tire radial direction, and in particular, the cord of the layer directly in contact with the outermost layer 11 is the steel cord of the outermost layer 11. (A) and steel cords (B) that are arranged in an opposite direction across the tire equator.
Use.

The main layer 13 uses a steel cord (C) which is adjacent to the protective layer 12 on the inner side in the tire radial direction and is composed of two layers of substantially non-stretchable cord.

The steel cord (C) layer that occupies the maximum width W among at least two layers (four-layer configuration in the illustrated example) of the main layer I3 is:
Protective layer 12 or its wide steel cord (B)
The width is narrower than the width HW of the layer, and the cords in that layer are arranged in the same direction as the inclined arrangement with respect to the equator of the tire.

In the illustrated example, the arrangement width W of the steel cord layer of the outermost layer 11 is 74% of the width of the tread 2.

Regarding each steel cord (A), (B), and (C) mentioned above, the following relationship regarding elongation at break and breaking load (%) (B) > (A) > (C)
Breaking load (kg/piece) (C)>(B)> (
A) shall be satisfied.

(Function) In the present invention, the outermost layer 11 of the Pel l-6 can pass through the cut flaws even when the tread 2 inevitably receives cut flaws and develops to the belt 6 while the tire is running on rough ground. This single-layer oven-twisted cord is made by twisting multiple steel filaments with wire diameters of 0.3 to 0.5, which plays the role of preventing rust caused by moisture on the ground surface entering through the cord. The penetration of the cord-coated comb during tire vulcanization is increased by applying a twist such that the apparent tensile elongation PLE is within the range of 0.4 to 1.2"6. It is necessary to have two or more cables made of so-called compene train cords that have sufficiently adjusted the optical fibers.

In this case, if the steel filament is thinner than 0.3 mm, it tends to cause force...1/penetration, and if it is thicker than 0.5 mm, there may be production problems such as uneven twisting.

If the tensile strength is less than 0.4%, there is a problem of rubber entering the inside of the cord or being insufficient.
On the other hand, if it is greater than 1.2%, the rubber will invade more than necessary, resulting in disadvantages in workability and quality, such as uneven implantation during rubber coating.

Next, the protective layer 12 is located below the outermost layer 11, and has the flexibility of the belt 6 to wrap around the tread 2 when the tire runs over a protrusion on the ground surface while running on rough ground. In addition to ensuring the so-called enveloping property, it is useful to improve belt edge separation resistance by reducing distortion near the edge of the main layer 13, and for this purpose, the outermost layer I+ is It must consist of high elongation stranded cords arranged adjacently.

This is because the rubber penetration cord of the outermost layer 11 has a limited elongation at break due to production due to the twisted structure mentioned above, and the elongation at break is smaller than that of high elongation twisted cord, especially the cord. Because the rubber penetrates between the filaments in the interior, it is even more difficult to stretch. This is because when the main layer 13 made of substantially non-extensible steel cord is arranged to bear the tension load of the tread 2, the tread 2 is frequently cut because it hardly provides any cushioning effect. be. In addition, from the point of view of the buffering effect, it is possible to consider interposing a rubber sheet, for example, but since it is disadvantageous in terms of the cut penetration resistance of the entire layer of the heald 6, it is originally unnecessary. However, there are disadvantages in terms of heat generation due to the addition of rubber, and separation occurs there.

accompanied by a problem.

Therefore, the elongation at break is the largest among the three types of steel cords constituting the belt 6, and the breaking load is also the highest in the outermost layer 11.
Is it higher than the rubber penetration code of main layer 1?
By arranging the protective layer 12 made of cord with high elongation twist, which is lower than the steel cord in No. 3, between the outermost layer +1 and the main layer 12, 1.) Reducing cut damage while ensuring envelopability. 2.) Increase the resistance of the belt 6 as a whole to cut penetration (such as reaching the main layer 13); 3.) Protective layer 1
4.) In addition, the width end of the belt 6 (especially the maximum width main layer) ) is useful for alleviating distortion.

Here, the rubber penetration cord of the outermost layer 11 and the high elongation twisted cord of the protective layer 12 that is in direct contact with it are arranged at opposite angles across the equator of the tire because of the cut that reaches the outermost layer 11. In order to suppress moisture-proof rubber penetration cords or high-elongation stranded cords in their intersection areas even under scratches, moisture penetration along the high-elongation stranded cords and the resulting resistance to corrosion such as rusting can be prevented. This is because deterioration of cut separation properties can be advantageously prevented.

The widest layer of the main layer 13 serves as tread reinforcement for this type of tire, and therefore has an array width W corresponding to approximately 65 to 90% of the tread width TV, or is a single layer in the example of FIG. When the protective layer 12 shown in the above case or a plurality of layers is formed, the width HW of the largest layer is
Wider than the maximum array width W of
Exceeding 20% is probably due to the enhancement of the effect (because it would become meaningless).

Second, it is necessary that the direction of the inclined arrangement of the cords in the main layer 13 with the largest width and the protective layer 12 or with the largest width of the layers is the same, and they are in different directions. This is because the shear strain becomes excessive near those edges, which goes against the purpose of reducing or alleviating the strain at the belt edges.

The various steel cords used for the outermost layer 11, the protective layer 12, and the main layer 13 are arranged within a range of 20 to 30 degrees with respect to the equator of the tire, and generally follow the customary cord arrangement of Hekuto.

The above-mentioned various steel cords (A) (B) are used for the belt 6.
) and (C) relate to elongation at break, and code (A) is 4.
0~6.0! %, code (B) is about 4.5 to B, 0%, and code (C) is about 1.5 to 3.0%, and the relationship is (B) > (A) > (C). Regarding load, cord (A) is 140 to 190 kg/piece, cord (B
) is 170-275 kg/piece, code (C) is 280
~2000 kg/piece, the relationship (C) > (B), > (A) is established, especially in terms of strength balance as the belt 6.
The (A)/(B) ratio of breaking load is 0 from the point of view of cut resistance.
．． 5 or more, and 0.83 or less in terms of enveloping property, same < (B)/(C) ratio, 0.12 or more in terms of cut resistance protection function, and 0.83 or less in terms of enveloping property.
It seems like it should be 69 or less.

As for the comb penetration cord as steel cord (A), I have already mentioned the disclosure in Japanese Patent Application Laid-Open No. 116504/1983. During vulcanization molding, the vulcanization pressure applied to the steel cord, which is the main layer with the maximum width of the belt, is high, and the time that the tread rubber and cord covering rubber are in a fluid state is extremely short. However, the rubber is not sufficiently penetrated into the inside of the cord by being crushed toward the center of the cord, especially when the tread gauge is thick like the tire of this invention, which belongs to the category of large off-throttle tires. The molding pressure during vulcanization molding is significantly relaxed, and at the same time, the vulcanization molding time is long when trend rubber and coating rubber are in a fluid state, so PLE or 0.
As long as a single-layer open strand cord with a concentration of 4 to 1.2% is used, there will be no problem with rubber penetration into the interior of the cord.

Figures 2(a) and (bj) illustrate here a cross-section of this type of cord, and Figures 3(at and (b)) show a filament which serves to produce almost complete com-penetration into the interior of the cord. This diagram illustrates how an inflow gap is generated between the two.

(Example) Example 1 According to the above, tire size 0RR18
,00R25 steel radial tires were prototyped in the following manner.

The carcass specifications are steel cord, twisted structure (IX
3+9+15)XO123mm +IXO,15m
m Breaking elongation 2.5 layer% Breaking load 280 kg/ 1 drive (center of crown part) 12 150 mm,
Regarding the belt configuration, steel cord (C) (I
X 3 + 9 + 15) Xo, 23mm + I
X0915mm steel cord (breaking elongation 2.5%,
Breaking load 280 kg/piece), driving 25 pieces 150 pieces
aun, and the steel cord (B) has (3
X7）
A) is I X 5 Xo, 38 m + n single layer open twisted cord (PLE: 0.7%, twist angle 1
8°, elongation at break: 4.6%, load at break: 140 kg
/piece) were placed in an array of 19 pieces 750 mm, each with 10 pieces.
A rubber coating with 40 kg/cm2 of 0% mossulus was carried out. Regarding the breaking load in this example, A)/(B)
The ratio is 0.82 same < (B) / (C) ratio is 0.61
Met.

The test tire 1 according to the present invention is shown in FIG.
A total of six layers of belt 6, consisting of a single steel cord (B) and a steel cord (A) superimposed on four layers of steel cord (C), serve as tread reinforcement, and each layer has an inclination relative to the tire's equator. With an arrangement angle of 23 degrees, in order from the bottom side, that is, the carcass side, R1 upper right sushi,
On the main layer 13 of upper right R1 and upper left L, the protective layer 12 of upper left L, and the outermost layer 11 of right upper R are sequentially laminated.

In this example, the tread width TW is 430mm, the maximum width of the main layer 13 is 300mu (0,7・TW), the width of the protective layer 12 is 360mu (1,2・W), or the width of the outermost layer 11 is 33mm.
5 mm (0.78・TW).

On the other hand, according to the conventional technique, as shown in FIG.
Main layer 13 with a laminated structure almost similar to that listed above
A conventional tire 1 was prepared as a control, having the same structure as the test tire except that a layer using the steel cord (B) described above was also laminated to replace the outermost layer 11.

Further, according to the conventional technique, a conventional tire 2 was also prepared in which only a layer of steel cord (A) was applied instead of the steel cord (B) used in the conventional tire 1, as shown in FIG. 5(b).

Furthermore, for reference, a layer of steel cord (A) is placed on the main layer 13 having a similar laminated structure as shown in FIG. Comparative tires 1 are stacked in reverse order, and similar stacking results in a modification in which the steel cord (A) layer is wide and the steel cord (B) layer is narrow, as shown in Fig. 6(b). Comparison tire 2 was prepared.

These tires were subjected to the following tests.

Cut resistance test A steel wedge-shaped cutter sharpened with a cutting edge angle of 60°,
Based on the trend of a tire inflated with an internal pressure of 7 kgf/cm2, it is pressed at four locations on the circumference at 0° to the equator, and the size of the pushing load on the cutting edge when it penetrates into the cutting edge or tread 2. Control (conventional tire 1)
Performance was compared using an index with the value of 100.

Cut separation resistance test A cut wound was made from the surface of the tread 2 until one of the outer layers of the belt 6 was separated, and the same amount of water was poured through the wound, and then a drum test with an outer diameter of 5 m was performed. While running at a speed of 30 km/h under the conditions of tire internal pressure 7 kgf/cm2 and load 9160 kg, the time until cut separation occurred was compared using an index display with control performance as 100. .

Cut separation resistance test Each tire prepared separately was subjected to a drum testing machine with an outer diameter of 5 m, and the internal pressure was 7 kgf/cm2, the speed was 301 an/h, and the load was a two-step funnel (100% load: 9160 kg: 80
%. 100%. 1101%, 120%. The time required for belt edge separation to occur under conditions of 30 minutes on/off) was compared using an index, with the control performance being set as 100.

The results are shown in Table 1.

Table 1 Large Index Good Next, as shown in Figure 4 (b), among the main layers 13 in Figure (a), the steel cord (
Remove layer C) and replace it with steel cord (B)
A modification is carried out in which the protective layer 12 is particularly made into a two-layer structure by adding a further layer and overlapping the cord and the original steel cord (B) layer in the direction of the cord inclination that intersects the tire equator. In addition, as shown in Fig. 4 fcl and (d), various simplified modified embodiments of the main layer 13 having a three-layer or two-layer structure were fabricated and tested. It was shown that the results were similar to those of Heta.

Example 2 A steel radial tire with a tire size of 37.00 R57 was manufactured as a trial in accordance with the following requirements and as described in Example 1.

■Carcass (I x3 +9 +15) X7XO, 28mm+
I .25n
Un breaking load: 1,400 kg/Elongation at break, 2.7% Driving, 7 pieces 150 mm (B) Steel cord (B) (4x 7) xo, 23 work Breaking load: 275 kg/Elongation at break = 6. 2% Driving: 15 strands 150mm (c) Steel cord (A) IX5X0.5mm PLE: 0.894 Twisting angle/20° Breaking load: 160 kg/strand elongation at break 4.8% Driving, 20 strands 150mm (d) Steel cord tension ratio (A) / (B) = 0.58 (B) / (C) -0,20 Other specifications of this trial tire are as follows.

Tread width TW: 850 Maximum width of main layer 13: 680 mm (0.8 TW)
Width of protective layer 12: 780 mm (1,15W) Width of outermost layer 11 600 mm (0,70TW) The results under the following test conditions are as shown in Table 2 (Notsu I+0 ■, cut resistance test cutter Blade edge angle 60° Tire internal pressure 7kgf/cm2 Blade edge direction 0° relative to the equator 2) Cut-resistant separation lane test Tire internal pressure 7kgfz'cm2, load 51500k
g speed 10km/h 8, held resistant end separation lane test internal pressure 7kgf/cm2, speed 10km/h 100%
Load: 51,500 kg Table 2 (Effects of the Invention) According to the present invention, when a pneumatic radial tire for a heavy-load vehicle traveling on rough terrain runs over sharp protrusions scattered on a rough ground surface, the tire can wrap around the sharp protrusions scattered on the rough ground surface. Due to the deformation of the tread, the tread retains excellent cut resistance under sufficient emperotubularity to effectively prevent cut damage caused by the protrusions, and moisture caused by cut damage that is inevitable due to long-term use of the tire. By effectively suppressing TLB damage caused by rust caused by the infiltration of tires, and by improving the belt structure with excellent belt edge separation resistance, we have significantly improved the durability and reliability of this type of tire. I can't contribute but 0

[Brief explanation of drawings]

Fig. 1 is a left half cross-sectional view of a construction vehicle tire according to the present invention, Fig. 2 (al, fb) is a standard cross-sectional view of a single-layer open stranded cord, and Fig. 3 (1al) is a longitudinal cross-sectional view of a tire for a construction vehicle. 4 (al to ld+ are schematic diagrams showing how to stack a belt according to the present invention, and FIG. 3 1al and tbl are schematic diagrams showing an example of belt stacking according to the conventional technology. Figures 6+a+ and tbl are schematic diagrams showing the state of belt lamination in reference examples for comparison. 4... Bead core 5... Carcass 6...
11...Outermost layer 12...Protective layer 13...Main layer A...Single layer open twisted steel cord B...High elongation twisted steel cord C...Substantially inextensible steel Code patent applicant Bridgest Co., Ltd.

Claims (1)

[Claims] 1. Straddling a pair of bead cores in a toroidal manner;
A pneumatic radial comprising: a carcass for body reinforcement consisting of radially arranged rubber-coated steel cord layers; and a tread-reinforcing belt surrounding the crown portion of the carcass and comprising at least four laminated layers of rubber-coated steel cords. In tires, the above-mentioned belt is made of a single-layer open twisted cord made by twisting together a plurality of filaments with a wire diameter of 0.3 to 0.5 mm, and under the action of tension, the filaments constituting the cord are effectively burdened with stress. The outermost layer uses steel cords (A) whose tensile apparent elongation (PLE) that occurs in each cord is within the range of 0.4 to 1.2%, and the inner side of this outermost layer in the tire radial direction. at least 1 adjacent to
A protective layer made of steel cords (B) consisting of high elongation twisted cords, in which the cords in the layer directly in contact with the outermost layer are arranged at an angle opposite to the cords in the outermost layer across the equator of the tire; A main layer using a steel cord (C) consisting of at least two layers of substantially non-extensible cords adjacent to the protective layer on the inner side in the tire radial direction, and a steel core layer that occupies the maximum width of the main layer. The cord (C) layer has a width narrower than that of the protective layer or the wider steel cord (B) layer, and is arranged so that the cords in that layer and the tire are inclined in the same direction with respect to the equator. Codes (A), (B) and (C) have the following relationship regarding elongation at break and load at break: elongation at break (%) (B) > (A) > (C) load at break (kg) (C) > (B )>(A) A pneumatic radial tire for heavy-load vehicles running on rough terrain, characterized by satisfying the following. 2. (A)/(B) ratio per breaking load is 0.5 to 0.8
3. The pneumatic radial tire for heavy-duty vehicles traveling on rough terrain according to claim 1, wherein (B)/(C) is 0.12 to 0.69. 3. The outermost layer of steel cord (A) is 1x4 or 1x5
The pneumatic radial tire for heavy-duty vehicles running on rough terrain according to claim 1 or 2, which is a single-layer strand of. 4. The outermost layer is 5% relative to the tread width in the tire cross section.
The pneumatic radial tire for heavy-duty vehicles traveling on rough terrain as set forth in claim 1, 2, or 3, having an arrangement width of 0 to 80%.