JP5331535B2 - Heavy duty pneumatic radial tire - Google Patents

Description

  The present invention relates to a heavy-duty pneumatic radial tire, and more particularly to a pneumatic radial tire for a construction vehicle, and more particularly to a heavy-duty pneumatic radial tire with reduced side-cut failure when a step such as a stone on a running road is stepped on. Is.

  The tire for a construction vehicle traveling on a rocky road such as an underground mine has a tire width in the side wall portion region as schematically shown in FIG. Due to large bulging deformation outward in the direction, stones and other projections that come in contact with the rolling make the area susceptible to side cuts, and if this side cut reaches the carcass of the tire, it will cause failure such as puncture There was a fear.

  Therefore, in the past, a bias tire having a thick cord crossing layer in which a carcass ply made up of a plurality of cord crossing layers is arranged has a side cut scratch that hardly penetrates to the inner surface of the tire, and is resistant to side problems. There was an advantage of excellent cutting properties.

  On the other hand, radial tires are advantageous in terms of manufacturing man-hours and costs, and are also excellent in terms of wear resistance, traction performance, weight, etc. The car tire ply made of, for example, steel cord is provided on the side wall of the radial tire. In many cases, the rubber thickness of the side wall portion is also reduced, so that there is a high possibility that the side cut easily penetrates the carcass and causes a failure.

  In order to suppress such a side cut failure, in the radial tire, the rubber thickness of the sidewall portion is increased, or as described in Patent Document 1, rubber having excellent cut resistance is disposed on the tire side rubber. Although a technology for improving the side cut resistance has been proposed, the side cut resistance has not yet been improved to the same level as the bias tire.

  Further, in order to make the side cut itself difficult to receive, for example, as described in Patent Document 2, the outer surface width of the tire is set within the width direction of the tire in a non-load normal state that is attached to an applied rim and filled with an internal pressure. And gradually increasing from the maximum width position of the carcass layer to a position in a range separated by 0.3 to 0.7 times the radial distance at the tread edge from the maximum width position of the carcass layer, and the range By gradually reducing the position from the position of the tread to the end of the tread, even when the sidewall portion bulges and deforms outward in the tire width direction due to heavy load, the sidewall portion is made substantially perpendicular to the road surface, Techniques for preventing the occurrence of side cuts have been proposed.

  However, in the tire described in Patent Document 2, the rubber thickness of the buttress that is located in the outer region in the tire width direction of the tread ground contact end is increased, and the calorific value is increased due to the thickness. There was a risk that the heat generation durability of the rubber would decrease.

Japanese Patent Laid-Open No. 06-328912 JP 2001-213114 A

  Accordingly, an object of the present invention is to provide a heavy-duty pneumatic radial tire in which the heat generation durability of the tire is enhanced without fear of a reduction in side cut resistance due to protrusions such as stones.

A heavy-duty pneumatic radial tire according to the present invention includes a tread portion, a pair of sidewall portions, a pair of bead portions, and at least one carcass ply extending in a toroid shape between bead cores in each bead portion. A radial carcass and a tread rubber on the outer peripheral side of the crown area of the carcass, assembled to the applicable rim and filled with the specified internal pressure in the widthwise cross section of the unloaded tire, The angle α on the acute angle plane side formed by the virtual line segment connecting the intersection of the virtual line segment parallel to the rim diameter line and the tire outer surface and the tire maximum width position passing through the substantial position is 73 °. ≦ α ≦ 83 ° is satisfied, and the radial distance h from the tread center to the tire maximum width position is 0.30SH ≦ h ≦ 0.35SH with respect to the tire cross-section height SH. Met, the tread rubber from the tread ground contact end, the tire width direction distance m1 of the inclined region inclined radially inwardly toward the outer side in the tire width direction is a 0.08SH ≦ m1 ≦ 0.10SH, also, the The angle β between the radial line segment passing through the tire maximum width position and the tire outer surface satisfies the relationship of 0.08SH ≦ m2 ≦ 0.10SH and the radial distance m2 of the inclined region is 5 ° ≦ β It is characterized by satisfying the relationship of ≦ 10 ° .

Here, the “applicable rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK is used. In Europe, ETRTO (European Tire and Rim Technical Organization) is used. ) Standard MANUAL, in the United States, TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK, etc.
The “specified internal pressure” and “specified mass” refer to the maximum air pressure and maximum load capacity specified by JATMA or the like.
“Tire maximum width position” refers to the tire width direction when the tire is assembled to the applicable rim specified in JATMA, etc., and filled with the maximum air pressure specified in accordance with the tire size in the standard of JATMA, etc. The maximum width position in the cross section shall be said.
“Maximum width position of carcass” refers to a toroidal shape in which the tire is assembled to the applicable rim specified in JATMA, etc., and filled with the maximum air pressure specified according to the tire size in the standard of JATMA, etc. The maximum width position in the cross section of the tire width direction of at least one carcass ply that extends, and in the case of a plurality of carcass plies, the length of the outermost carcass ply.

  Also preferably, an imaginary line parallel to the rim diameter line and the outer surface of the tire passing through the maximum width position of the carcass in the cross-section in the width direction of the unloaded tire that is assembled to the applicable rim and filled with the specified internal pressure. A recess is formed between the intersection with the tire maximum width position.

  By the way, it is assembled to the applicable rim, filled with the specified internal pressure, and with the load corresponding to the specified mass applied, the carcass in the widthwise cross section of the unloaded tire filled with the specified internal pressure. The angle γ on the acute surface side formed by the virtual line segment connecting the intersection of the virtual line segment parallel to the rim diameter line passing through the maximum width position and the tire outer surface and the tire maximum width position is 70 °. ≦ γ ≦ 90 °.

  In particular, the pneumatic radial tire of the present invention is a virtual straight line connecting the intersection of an imaginary line segment parallel to the rim diameter line and the outer surface of the tire passing through the maximum width position of the carcass and the maximum tire width position. The angle α on the acute surface side formed with the line segment satisfies the relationship of 73 ° ≦ α ≦ 83 °, and the radial distance h from the tread center to the tire maximum width position is 0.30SH ≦ with respect to the tire cross-section height SH. By satisfying the relationship of h ≦ 0.35SH, in a state where a load corresponding to the specified mass is applied, as shown in FIG. 1, the buttress located in the outer region in the tire width direction of the tread contact end is The intersection of the imaginary line segment parallel to the rim diameter line and the outer surface of the tire that passes through the maximum width position of the carcass from the maximum tire width position when there is no load Until It is structured to incline in the tire width direction with respect to the road surface, and even if a step such as a stone is stepped on, the side rubber bulges outward in the tire width direction and does not become wider than the buttress, making it difficult to receive side cuts In addition, by defining the range of the angle α, it is possible to reduce the amount of rubber that will be positioned at the buttress. As a result, both the side cut resistance and the heat generation durability of the tire can be achieved.

  That is, when the angle α is less than 73 °, the amount of rubber of the buttress increases, so that the heat generation durability of the region decreases. On the other hand, when the angle α exceeds 83 °, a load corresponding to the specified mass is applied. In this state, the inner portion of the tire radius protrudes outward in the tire width direction from the buttress, which may reduce the side cut resistance.

  Also, if the distance h is less than 0.30SH, the amount of rubber that will be positioned at the buttress increases, so that the rubber thickness increases and the heat generation durability decreases. On the other hand, if the distance h exceeds 0.35SH, side cuts are likely to occur. There is a possibility that the side cut resistance in the region, particularly in the region located inward in the radial direction of the buttress cannot be improved.

The embodiment of the radial tire for heavy load of the present invention is assembled to an applicable rim, filled with a prescribed air pressure, and a load corresponding to a prescribed mass is applied. FIG. FIG. 3 is a diagram showing a tire width direction cross-section of a tire half portion in an unloaded state by assembling an embodiment of a heavy-duty radial tire of the present invention to an applied rim and filling a prescribed air pressure. It is a figure which shows the tire width direction cross section of the state which applied the load corresponding to a prescription | regulation mass to the tire of FIG. 1 about the half part of a tire. An embodiment of a conventional heavy-duty radial tire is assembled to an applicable rim, filled with a specified air pressure, and a load corresponding to a specified mass is applied. It is a figure shown typically.

The heavy duty radial tire of the present invention will be described in detail below with reference to the drawings.
FIG. 2 is a diagram showing a tire width direction cross section in a no-load state with respect to a half portion of the tire by assembling an embodiment of a heavy-duty radial tire of the present invention to an applicable rim and filling a prescribed air pressure.

  In the figure, 1 is a tread portion, 2 is a pair of side wall portions extending radially inward continuously to the respective side portions of the tread portion 1, and 3 is continuously inward in the radial direction of the sidewall portion 2. Each bead portion is shown.

The heavy-duty radial tire shown in the figure has a body portion 5a extending in a toroidal shape between a pair of bead portions 3 and a bead core 4 having a hexagonal cross section embedded in each bead portion 3, and each side portion is a bead core. 4 is provided with a radial carcass 5 made of a single carcass ply and having a folded portion 5b folded from the inner side to the outer side in the tire width direction.
Here, the carcass ply can be formed of, for example, a steel cord or an organic fiber cord extending in a direction orthogonal to the tire circumferential direction.
The carcass folding portion 5b extends to 0.30 to 0.46% of the tire cross-section height SH.

Further, in the figure, a belt 6 and a tread rubber 7 composed of four layers of cord crossing belts are sequentially arranged on the outer peripheral side of the crown region of the carcass 5, and a buttress 8 is provided in a region of 100 to 140% of the tire ground contact width. Although not shown in the drawing, a plurality of circumferential grooves and the like extending in the tire circumferential direction are formed on the surface of the tread rubber 7.
The “tire contact width” refers to a linear distance between both ends of a tread pattern of a tire in a no-load state with a tire mounted on an applicable rim and a specified internal pressure.

  In the sidewall portion 2 and the bead portion 3, the outer side in the tire width direction of the carcass 5 is covered with a side rubber 9 disposed along the outer surface thereof.

  In this heavy-duty radial tire, the virtual line of the virtual straight line connecting the intersection of the imaginary line segment r parallel to the rim diameter line s and the outer surface of the tire passing through the maximum width position of the carcass 5 and the tire maximum width position is described above. The angle α on the acute surface side formed with the line segment satisfies the relationship of 73 ° ≦ α ≦ 83 °, and the radial distance h from the tread center c to the tire maximum width position is 0.30SH with respect to the tire cross-section height SH. ≦ h ≦ 0.35SH is satisfied.

  In such a pneumatic tire, the tire width direction distance m1 of the tread rubber 7 that is inclined inward in the radial direction from the tread contact end toward the outer side in the tire width direction is preferably 0.08SH ≦ m1 ≦. A radial line segment passing through the tire maximum width position, a radial distance m2 of the inclined region satisfying a relationship of 0.08SH ≦ m2 ≦ 0.10SH, and a tire outer surface; Satisfies the relationship of 5 ° ≦ β ≦ 10 °.

  With this configuration, it is possible to chamfer the rubber of the buttress 8 that is less likely to be side-cut compared to the sidewall portion 2, and to achieve both side-cut resistance and heat-resistant durability.

Preferably, the recess 10 is formed between the tire maximum width position and the intersection of the imaginary line segment passing through the maximum width position of the carcass 5 and parallel to the rim diameter line s and the tire outer surface.
With this configuration, even when the sidewall portion 2 is overloaded, it is possible to reduce bulging deformation outward in the tire width direction.

Preferably, the radius of curvature of the recess 10 is in the range of SH to 0.5SH.
By setting it as this range, the side wall part 2 can be prevented from bulging outward in the tire width direction.

  That is, if it is less than 0.5 SH, a part of the side rubber 9 where the concave portion 10 is formed has an acute angle, which may reduce cut resistance. On the other hand, if it exceeds SH, Tend to bulge.

  FIG. 3 is a cross-sectional view in the tire width direction in a state where one embodiment of a radial tire for heavy loads according to the present invention is assembled to an applicable rim, filled with a specified internal pressure, and a load corresponding to a specified mass is applied. It is a figure shown about the half part.

  By the way, as shown in FIG. 3, an imaginary line segment r parallel to the rim diameter line passing through the maximum width position of the carcass 5 and the tire outer surface in the cross section in the width direction of the unloaded tire filled with a prescribed internal pressure. It is preferable that the angle γ on the acute angle surface side formed by the virtual line segment of the virtual straight line connecting the intersection of the tire and the tire maximum width position satisfies the relationship of 70 ° ≦ γ ≦ 90 °.

  With this configuration, even if a step such as a stone is stepped on, as shown in FIG. 1, the side rubber 9 does not bend outward in the tire width direction, so that it is difficult to receive the side cut itself. As a result, the side cut resistance of the tire can be improved.

That is, in it is less than 70 °, the tire section width is increased, tires from the vehicle there is a risk to undergo side cut out seen, while when it exceeds 90 °, the side rubber 9 is the outer side in the tire width direction at the time of load application It tends to bulge out and prevent side cuts.

Next, tires having a structure as shown in FIGS. 2 and 3 and having a size of 26.5R25VSMS were prototyped, and as shown in Table 1, the tires of the example and the comparative example were changed. For each of these, the side cut resistance and the heat generation durability were measured.
In addition, since the comparative example tire does not require modification about structures other than the tread part and the sidewall part, it was assumed to be in conformity with the example tire.

(Side cut resistance)
Each of the example tire and the comparative example tire is assembled to a rim of 22.00 / 3.0, the internal pressure is 650 kPa, the load mass is 18500 kg, and the test speed is 5 to 10 km / h in the field until it becomes a waste tire. It was run and measured by the number of cut faults / the number of inputs, and evaluated.

  From the test results, the example tire was able to improve the side cut resistance by 30% compared to the comparative example tire.

(Heat generation durability)
Each of the example tire and the comparative tire was assembled on a rim of 22.00 / 3.0, the internal pressure was 650 kPa, the load mass was 18500 kg, and the drum was tested for 24 hours at a test speed of 5 km / h. The temperature on the belt was measured and evaluated.

  From the test results, the example tires had the same heat generation durability as the comparative tires.

  From the above results, the example tires improved the side cut resistance without reducing the heat generation durability compared to the comparative example tires.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Radial carcass 5a Main body part 5b Folding part 6 Belt 7 Tread rubber 8 Buttress 9 Side rubber 10 Concave part R Applicable rim

Claims (3)

A tread portion, a pair of sidewall portions, a pair of bead portions, a radial carcass made of at least one carcass ply extending in a toroid shape between bead cores in each bead portion, and an outer peripheral side of a crown region of the carcass In pneumatic radial tires with tread rubber,
An intersection of an imaginary line parallel to the rim diameter line and the outer surface of the tire passing through the maximum width position of the carcass within the cross-section in the width direction of the unloaded tire filled with the specified internal pressure and assembled to the applied rim, The angle α on the acute surface side formed by the virtual line segment of the virtual straight line connecting the tire maximum width position satisfies the relationship of 73 ° ≦ α ≦ 83 °,
The radial distance h from the tread center to the tire maximum width position satisfies the relationship of 0.30SH ≦ h ≦ 0.35SH with respect to the tire cross-section height SH ,
The tire width direction distance m1 of the inclined region inclined inward in the radial direction from the tread contact edge of the tread rubber toward the outer side in the tire width direction is 0.08SH ≦ m1 ≦ 0.10SH. Is equal to 0.08SH ≦ m2 ≦ 0.10SH, and the angle β between the radial line segment passing through the tire maximum width position and the tire outer surface is 5 ° ≦ β ≦ 10. A pneumatic radial tire characterized by satisfying the relationship of ° . An imaginary line parallel to the rim diameter line, the tire outer surface, and the maximum tire width passing through the maximum width position of the carcass within the cross section in the width direction of the unloaded tire that is assembled to the applicable rim and filled with the specified internal pressure. The pneumatic radial tire according to claim 1, wherein a concave portion is formed between an intersection with a position. The maximum width of the carcass in the cross section in the width direction of the unloaded tire filled with the specified internal pressure while being mounted on the applicable rim and filled with the specified internal pressure and with a load corresponding to the specified mass The angle γ on the acute surface side of the virtual line connecting the intersection of the virtual line segment parallel to the rim diameter line passing through the position and the tire outer surface and the tire maximum width position is 70 ° ≦ γ The pneumatic radial tire according to claim 1 or 2 , satisfying a relationship of ≤90 °.

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