JPH10250320A - Heavy duty pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heavy duty pneumatic radial tire in which the separation resistance of a carcass is increased while a stability performance, side cutting resistance, and belt durability are held at high levels, respectively. SOLUTION: In a heavy duty pneumatic radial tire, a rubber reinforcement layer 7 of crescent-shape in cross-section is provided along the inner surface of a carcass 5 ranging from a side wall part 2 to a tread part 1, the inner side end 7LE of the rubber reinforcement layer 7 in tire radial direction is positioned within the range from a position 0.5 times a height to the maximum width of the carcass measured from a rim diameter line RL to the maximum width position A, and a tire outer side end in radial direction is positioned within the area which is surrounded by the extended line of a normal line VE extended downward from the innermost cord layer end of a belt (b) to the carcass and the extended line of the normal line VE extended downward from a tread surface upper position dividing, along the tread surface 1t, between the end edge of the tread part tread surface 1t and a tire equatorial plane to the carcass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for heavy loads, and more particularly to a radial tire for use in heavy vehicles such as construction vehicles and dump trucks, and particularly to non-paved roads and uneven terrain. Heavy load air with high stability stability and side cut resistance when traveling on roads, and improved separation resistance between the steel cord layers of the belt and the separation resistance of the carcass alone in the tread portion Radial tires.

[0002]

2. Description of the Related Art Heavy-duty pneumatic radial tires traveling on unpaved roads, uneven terrain, or rough terrain are particularly suitable for preventing loads caused by pitching or rolling of vehicles, for example, falling of crushed rocks and earth and sand. It is required to have the performance (vibration damping) and the protection structure against the side cut damage sometimes inevitably caused by rocks and other foreign substances scattered on the running road surface. It is known that a rubber reinforcing layer is arranged on the inner side of the carcass of the sidewall portion as an effective structure to satisfy the condition at the same time.

[0003]

Since the known rubber reinforcing layer only needs to consider both the stability performance and the side cut resistance, the radially inner end of the tire has a flange height of an applicable rim of the tire. Position from the vicinity of the tire position to the tire maximum width, and the tire radially outer end is in the area surrounded by the two normal lines extended down to the carcass from the tread edge and the innermost steel cord layer end of the belt, respectively. Stopped.

[0004] However, a comparative analysis of the results of using many of the tires with and without the rubber reinforcing layer shows that the former tire with the rubber reinforcing layer has more separation failures than the latter tire. Thus, it was found that the failure location was the separation of the carcass alone located near the outer side of the tire at the end of the innermost steel cord layer of the belt. Then, when it was further confirmed by an indoor durability test, the occurrence of carcass separation which was not seen in the latter tire and was similar to the actual use was observed. In this case, it cannot be said that the improvement effect of the stability performance and the anti-side cut property is advantageously used, and it has been found that it is urgently necessary to prevent the occurrence of separation failure of such a new carcass.

Therefore, the invention described in claim 1 or 2 of the present invention not only maintains the separation resistance of the belt to a high degree, but also maintains the conventional excellent stability performance and side cut resistance. Accordingly, an object of the present invention is to provide a pneumatic radial tire for heavy load capable of significantly improving the separation resistance of the carcass itself and exhibiting excellent separation durability as a whole from the belt to the carcass.

[0006]

Means for Solving the Problems To achieve the above object, the invention described in claim 1 of the present invention comprises a tread portion, a pair of side wall portions and a pair of bead portions connected to both sides of the tread portion. A carcass, which becomes a rubber coating of a one-ply radially arranged steel cord that reinforces each part between bead cores embedded in a bead part, and a belt made of four or more steel cord layers that reinforces a tread part around the perimeter of the carcass The heavy-duty pneumatic radial tire provided has a rubber reinforcing layer having a crescent cross section along the carcass inner surface extending from the sidewall portion to the tread portion, and the tire radially inner end of the rubber reinforcing layer was measured from the rim diameter line. The tire is positioned within a range from 0.5 times the height to the maximum width of the carcass to the maximum width position and the tire The radial outer end is extended from the innermost cord layer end of the belt to the carcass, and from the position on the tread which divides the line between the edge of the tread tread and the tire equatorial plane into two along the tread. It is characterized in that it is located in a region sandwiched between an extension of the normal drawn down to the carcass.

Here, the rubber reinforcing layer naturally forms a pair, and the rim diameter line is JATMA YEAR BOOK (1).
996 version) refers to a straight line that passes through the actual diameter (φD) position of the applicable rim determined according to the size and type of the tire and is parallel to the rotation axis of the tire, and does not use the nominal diameter of the rim.

[0008] To maintain excellent stability performance and side cut resistance due to the arrangement of the rubber reinforcing layer, to suppress the shear strain acting on the carcass during the rolling of the tire to an appropriate value, and to reduce the heat generation. In order to keep within a limit, it is desirable that the 100% modulus of the rubber of the rubber reinforcing layer is in the range of 15 to 40 kgf / cm ² as in the invention described in claim 2.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a diagrammatic left half cross-sectional view of a heavy-load pneumatic radial tire (hereinafter abbreviated as a tire) on a plane including a rotation axis, in which a tire is provided on a tread portion 1 and on both sides of the tread portion 1. A pair of side wall portions 2 (only one side is shown) and a pair of bead portions 3 (only one side is shown) are connected.
Is reinforced by a one-ply toroidal carcass 5 between the bead cores 4 embedded in the bead portion 3.
The belt 6 strengthens the tread portion 1 on the outer periphery of the belt.

The carcass 5 is formed of a rubber-coated ply of a radially arranged steel cord, and the belt 6 is formed by laminating four or more steel cord layers (five layers in the illustrated example). The illustrated belt 6 is a substantially inextensible steel cord layer (four layers) 6.
-1 to 6-4 are shown by solid lines, and the so-called high elongation steel cord layer (one layer) 6-5, which is more extensible than the steel cords of these layers, is shown by broken lines.

A rubber reinforcing layer 7 is arranged along the inner surface of the carcass 5 extending from the sidewall portion 2 to the tread portion 1 (the surface facing the inside of the tire). In other words, it is arranged between the carcass 5 and the inner liner 8. The rubber reinforcing layer 7 is particularly shown with diagonal lines, and is also arranged on the right half (not shown). The cross-sectional shape of the rubber reinforcing layer 7 is tapered in a radial direction (hereinafter, abbreviated as a radial direction) inward and outward from the central portion, and has a substantially crescent shape. The rubber reinforcing layer 7 is disposed in a region described below.

First, in FIG. 1, although not shown, the tire is mounted on a standard rim among the appropriate rims, and the tire rotates through a rim diameter (φD) position in a tire posture filled with air pressure corresponding to the maximum load capacity. Carcass 5 measured from rim diameter line RL which is a straight line parallel to the axis (not shown)
It relates the height h up to the maximum width position A of the radially inner end 7 _LE of rubber reinforcing layer 7, and the same manner as described above at a height H as measured in the range of 0.5 × h~1.0 × h Set to a certain height. The appropriate rim, the standard rim, the maximum load capacity and the air pressure corresponding to this capacity are JATMA YEAR
Follow the rules defined by BOOK (1996).

Next, as viewed in the cross section of FIG. 1, a position C (so-called 1/1) on the tread which halves the length along the arc between the edge TE of the tread 1t of the tread portion 1 and the equatorial plane E of the tire. 4
From the point) to the carcass 5, an extension of the normal V _C and the end 6-6 of the cord layer 6-1 of the belt 6 closest to the carcass 5.
1E from positioning the radially outer end 7 _UE reinforcing layer 7 in a region sandwiched between the extended line of a normal line V _E drawn down on the carcass 5. The width end 6-1 of the innermost cord layer 6-1 of the belt 6
E extends beyond the normal line V _C , and
Normal V _T and the normal V drawn from the edge TE in the carcass 5
_{And C.}

FIG. 1 shows the tread portion 1 and its vicinity.
Referring to FIG. 2, which shows a similar cross-section of the shape at the time of internal pressure filling indicated by the broken line and the shape immediately below the load indicated by the solid line, both sides of the tread portion 1 immediately below the load of the rolling tire and the vicinity thereof The carcass 5 at the end has a small change in curvature in a region where the belt 6 having a large bending rigidity exists, but is located outside the cord layer 6-1 of the belt 6 closest to the carcass 5 (a hatched portion surrounded by a round broken line). A large change in curvature occurs.

Due to this large change in curvature, a remarkably large shear strain is generated between the carcass 5 and the surrounding rubber, and this shear strain acts on the carcass 5 repeatedly over a long running period of the tire, and as a result, separation failure may occur. Many. The peripheral rubber referred to here means that at least the cord layer of the belt 6 near the carcass 5 has a substantially cylindrical shape,
A space rubber (or cushion rubber) that fills a gap between the belt 6 and the carcass 5 because the carcass 5 needs to be formed with a relatively small radius of curvature from around the quarter point while having a large radius of curvature in the tire cross section. That is.

[0016] However, since this change in curvature region of the large carcass 5 is present 1/4 points on the outside, cross-sectional crescent shape to a region sandwiched between the extension of the extension line and the normal V _C of the normal line V _E By extending the rubber reinforcing layer 7, the rigidity of the curvature changing region of the carcass 5 can be increased, and a sudden change in the rigidity can be reduced. As a result, the amount of curvature change of the carcass 5 in the curvature changing region can be reduced. Thus, the shear strain acting on the carcass 5 can be reduced, and the occurrence of separation failure can be suppressed.

The radial outer end 7 _UE of the rubber reinforcing layer 7 is set to 1 /
The reason for keeping the normal V _C from the four points is that the tread part 1 area from one quarter point to the other quarter point already has sufficiently high bending rigidity, This is because there is no point in arranging the reinforcing layer 7, and furthermore, the heat generation of the tread portion 1 generated due to the rolling of the tire increases, so that the separation resistance is deteriorated due to a higher temperature rise. When the position of the radial outer end 7 _UE of the rubber reinforcing layer 7 is changed variously, the shear strain acting on the carcass 5 and the normal line V _C
Table 1 shows the results of experiments on the heat generation (1/4 point heat generation) on the upper surface of the belt 6. The results shown in Table 1 are obtained by adjusting the radial inner end _7LE of the rubber reinforcing layer 7 to the height h.

[0018] In Table 1, the shear strain represents at index to 100 the value obtained kept to an extended line of a normal line V _T of the outer end 7 _UE from the edge TE of the tread surface 1t, the belt 6 on the surface of The heat generation is reduced by 100 at the intermediate position between the 1/4 point C on the tread surface 1t and the tread position B on the equatorial plane E, that is, the normal line V _1/8 (not shown) for the carcass 5 passing through the 1/8 point. In each case, the smaller the value, the better.

[0019]

[Table 1]

[0020] From Table 1, when the keep the radially outer end 7 _UE of the rubber reinforcing layer 7 to an extended line of a normal line V _E of the hump portion, 1
/ 4-point whereas fever is good, while there is melancholy separations occur shearing strain acting on the carcass 5 is too large, the carcass 5 through the law 1/8 points of the outer edge 7 _UE
If the extension of the normal line to V is extended to V _1/8, the heat generated at the 1/4 point becomes too large, causing the belt 6 to generate heat separation, and the shear strain reduction effect is reduced by the normal V _C. Since it is saturated, it turns out to be meaningless.

[0021] Major function of determining the original rubber reinforcing layer 7 is in the protection during improvement of the stability performance and sidecut injury as previously described, the radially inner end 7 _LE of rubber reinforcing layer 7 It should be kept within a range that sufficiently fulfills the above-mentioned functions, and within this range, a desirable region of the sidewall portion 2 having a small overall gauge makes sense. Table 2 shows the results of experimentally confirming the effects on stability performance and side cut resistance when the position of the radial inner end _7LE of the rubber reinforcing layer 7 is variously changed. Note the results shown in Table 2 are those fixed to an extension of the normal V _6-1E against the carcass 5 through the cord layer 6-1E radially outer end 7 _UE of the rubber reinforcing layer 7.

The first intermediate position shown in Table 2 is an intermediate position along the carcass 5 between an extension of the normal normal V _T lowered from the tread edge TE to the carcass 5 and the maximum width position A of the carcass 5. And the second intermediate position is an intermediate position along the carcass 5 between the first intermediate position and the maximum width position A of the carcass 5. The rim line is a small annular projection for centering at the time of assembling the rim, which is provided at a position radially outward of about 25 mm from a position corresponding to the flange height of the standard rim.

[0023]

[Table 2]

From Table 2, it can be seen that when the radial outer end _7UE of the rubber reinforcing layer 7 is in the first and second intermediate positions, the stability performance and the side cut resistance are insufficient, and the minimum width position of the carcass 5 is minimum. A, it is necessary to extend the outer edge 7 _UE to the rim line, while both performances have a height of 0.5
Since it is the same as h, it is understood that only the cost increases and is meaningless.

[0025] Here rubber 100% modulus of the rubber of the reinforcement layer 7 (hereinafter referred to as M ₁₀₀₎ is that in the range of 15~40kgf / cm ² meet the objects of the present invention. The radially inner end 7 _LE of rubber reinforcing layer 7 fit to the height h, the extended line of a normal line V _6-1E against the carcass 5 through the cord layer 6-1E radially outer end 7 _UE of the rubber reinforcing layer 7 per combined tire, when the various changing the M ₁₀₀ of the rubber of the rubber reinforcing layer 7,
The shear strain acting on the carcass 5 and the heat generation (1/4 point heat generation) on the surface of the belt 6 at the position of the normal line V _C were measured.

The measurement results show that M ₁₀₀ of the rubber reinforcing layer 7 is 10
The shear strain when kgf / cm ² is set to 100 is represented by an index, and M ₁₀₀ is set to 55 kgf / cm ² when the 1/4 point heat generation is set to 100. The results are shown in Table 3. . The smaller the value, the better.

[0027]

[Table 3]

[0028] From Table 3, M ₁₀₀ of the rubber reinforcement layer 7 is 10kg
In the case of f / cm ^2, the 1/4 point heat generation is good, but the shear strain is large and it is an incompatible rubber. On the other hand, in the case of 55 kgf / cm ² , the shear strain tends to be good. 4
Is incompatible rubber point heating is increased, thus rubber M ₁₀₀ of the rubber reinforcing layer 7 fits in the range of 15~40kgf / cm ^2.

[0029]

EXAMPLE A construction vehicle tire with a size of 37.00R5
The height h at the maximum width position A of the carcass 5 is 470 mm according to the configuration shown in FIG. The １ ／ point of the tread 1t has an arc length from the equatorial plane E of 198 mm, and thus the arc length up to the tread edge TE is 198 × 2 = 396 mm. The length of the arc along the cord layer up to the end 6-1E of the steel cord layer of the nearest belt 6 is 330 mm.

First, Examples 1 to 4 subjected to a drum durability test
3 and Comparative Examples 1 to 4 were prepared. Implementation
Radial outer side of rubber reinforcing layer 7 in tires of Examples 1 to 3
End 7 _UEIn Examples 1 and 3, the normal V_CExtension of and implementation of
Example 2 is normal V_CExtension and Normal V_EIn the middle of the extension of
Was located. Also radial inner end 7_LEAbout height H
Is the height h of the maximum width position A of the carcass 5 in the first and third embodiments.
235 mm, which is 0.5 times as large as 0.5 times,
282 mm.

On the other hand, the rubber reinforcing layers of Comparative Examples 1 to 4
Radial outer end 7 of_UEComparative Example 1 starts from the tread edge TE.
Normal V_TOn the extension of the above, the comparative example 2 is a method from 1/8 point.
Line V _1/8And Comparative Examples 3 and 4 are both normals.
V_CAre located on the extension of
End 7_LEHeight H is set to 235 mm, 0.5 times the height h
Was. M of rubber reinforcing layer 7₁₀₀For the value of Example 1,
2 is 30kgf / cm^TwoIn Example 3, 23 kgf / cm^TwoAnd the ratio
Comparative Examples 1 and 2 are the same as Examples 1 and 2, 30 kgf / cm^TwoAnd
Comparative Examples 3 and 4 significantly deviated vertically from the above values.
Is 10kgf / cm^TwoComparative Example 4 was 50 kgf / cm^TwoIt is. this
Examples 1 to 3 and Comparative Examples 1 to 4 are all except for the above points.
Identical. Each tire of Examples 1-3 and Comparative Examples 1-4
Drum durability test using the following test method as a test tire
Was carried out.

Filling internal pressure 7.0 kgf / cm ² , applied load 5
The vehicle travels straight at 1.5 tons at a speed of 25 km / h. After 100 hours from the start of the test, the temperature on the surface of the belt 6 at the 1/4 point is measured, and then the vehicle is driven until a separation failure occurs. This is a method of measuring the running time. Table The results of these tests with radial end position and M ₁₀₀ value of the rubber reinforcing layer 7 in the Example 4
Shown in BLB described in the failure mode in Table 4 indicates the separation between the steel cord layers of the belt 6 by the carcass SEP. Is the steel cord layer end 6-1E of the belt 6.
The carcass separation in the vicinity is shown respectively.

[0033]

[Table 4]

From Table 4, it can be seen that in Examples 1 to 3, the temperature at the 1/4 point was maintained within an appropriate range, and the failure mode was such that the carcass separation failure did not occur and the running time was sufficient to satisfy the demands of the market. It can be seen that only the BLB failure has occurred, and as a result, the belt to the carcass as a whole have excellent separation durability.

On the other hand, Comparative Examples 1 and 2 have desirable M ₁₀₀
Even if a rubber reinforcing layer having a value of is arranged, the outer end in the radial direction is out of the proper position, so that the comparative example 1 has insufficient traveling despite the １ ／ point temperature being within the proper range. The carcass separation failure occurred in time, and in Comparative Example 2, the 1/4 point temperature was too high because the radially outer end of the rubber reinforcing layer was too deep into the tread portion. It can be seen that a BLB failure has occurred at an early stage.

The shortage also the value of M _{10 0} of Comparative Examples 3 and 4 rubber reinforcing layer be disposed rubber reinforcing layer in a proper position much trouble is too low or too high, significantly both durable travel time and, in particular it demonstrated that the carcass separation failure as the value of M ₁₀₀ is seen in Comparative example 3 too low occurs.

Further, in order to evaluate the side cut resistance in actual use in the market and to check the stability performance when the vehicle is mounted on an actual vehicle and run, a radial outer end 7 _{UE of the} rubber reinforcing layer 7 is used. Examples 4 and 5 in which was positioned on the extension of the normal line V _C and the radial inner end _7LE was changed respectively.
And the tires of Comparative Examples 5 and 6 were prepared. Comparative Example 5,
The outer end 7 _{UE of} 6 was the first intermediate position and the second intermediate position mentioned above.

The evaluation of the side cut resistance is based on the waste rate (%) of the side cut in the market, and the stability performance is checked from the time when a load of the same weight is temporarily loaded on a dump truck equipped with 37.00R57. The time (second) until the vibration of the sample stopped was measured. The waste rate by side cut (%) is the percentage of tires that are scrapped due to side cuts among many tires scrapped at the same use site. These results are shown in Table 5 together with the position of the radial inner end _7LE .

[0039]

[Table 5]

From Table 5, it can be seen that Examples 4 and 5 have significantly better performances than Comparative Examples 5 and 6 in terms of vibration damping time and side cut resistance, which are representative substitutes for stability performance. .

[0041]

According to the invention described in claim 1 or 2 of the present invention, while maintaining the separation resistance of the belt at a high level, the belt has superior stability performance and side cut resistance superior to the conventional tire. It is possible to provide a long-life pneumatic radial tire for heavy loads that can exhibit the separation resistance of the carcass itself significantly and exhibit excellent separation durability as a whole from the belt to the carcass.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of occurrence of carcass separation.

[Explanation of symbols]

Reference Signs List 1 tread portion 1t tread surface 2 sidewall portion 3 bead portion 4 bead core 5 radial carcass 6 belt 6-1E belt cord layer end closest to carcass 7 rubber reinforcing layer 7 _UE rubber reinforcing layer radial outer end 7 _LE rubber reinforcing layer Radial inner end 8 Inner liner E Tire equatorial plane A Carcass maximum width position B Position on equatorial plane of tread C 1/4 point on tread TE TE tread edge V _E Normal line from innermost cord layer end of belt to carcass height from V _C 1/4 point from the normal V _T tread edge to the carcass from the normal RL rim diameter line h rim diameter line to the carcass to carcass maximum width position

Claims (2)

[Claims] 1. A rubber coating of a one-ply radially arranged steel cord comprising a tread part, a pair of sidewall parts and a pair of bead parts connected to both sides thereof, and reinforcing these parts between bead cores embedded in the bead part. And a heavy-duty pneumatic radial tire having a belt made of four or more steel cord layers for reinforcing the tread portion at the outer periphery of the carcass, wherein a crescent cross section along the inner surface of the carcass from the sidewall portion to the tread portion is provided. Having a rubber-like reinforcement layer in the shape of a tire, the tire radially inner end of the rubber reinforcement layer is positioned within a range from the position 0.5 times the height to the carcass maximum width measured from the rim diameter line to the maximum width position. Extension of the normal where the tire is positioned and the outer radial end of the tire is lowered from the innermost cord layer end of the belt to the carcass. Characterized in that it is located in a region sandwiched between an edge of the tread portion tread surface and an elongation line of the normal from the position on the tread surface which divides the tire equatorial surface into two along the tread surface from the position on the tread surface. Pneumatic radial tire for heavy loads. ^2. The tire according to claim 1, wherein a 100% modulus of the rubber of the rubber reinforcing layer is in a range of 15 to 40 kgf / cm ² .