JP5405992B2 - Heavy duty pneumatic radial tire - Google Patents

Description

  The present invention relates to a heavy-duty pneumatic radial tire, and more particularly to a heavy-duty pneumatic radial tire suitable for use in construction vehicles, and relates to a heavy-duty with reduced side-cut failure when stepping on protrusions such as stones on a runway. The present invention relates to a heavy duty pneumatic radial tire.

  Tires for construction vehicles traveling on rocky roads such as underground mines, as shown schematically in FIG. 4 in the width direction cross section at the time of load rolling of the tire, the side wall region is the tire width. 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, conventionally, in order to cope with such a problem, a bias tire in which a carcass ply composed of a plurality of cord crossing layers is arranged has been widely used.
This is because a bias tire having a thick cord crossing layer is advantageous in that side cut scratches hardly penetrate to the inner surface of the tire and has excellent side cut resistance.

  On the other hand, radial tires are advantageous in terms of manufacturing man-hours and cost, and are superior to bias tires in terms of wear resistance, traction performance, weight, etc., but in the sidewall portion of the radial tire, For example, a carcass ply made of a steel cord is often arranged in a single layer, and the rubber thickness of the side wall portion is accordingly reduced. Therefore, there is a high possibility that the side cut easily penetrates the carcass to cause 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 volume of the buttress rubber in the outer region in the tire width direction of the tread ground contact end is increased, and the heat generation amount is increased due to the volume, and the heat generation durability of the tread rubber is increased. There was a risk of lowering.

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 capable of effectively suppressing the amount of heat generated by the tread rubber while eliminating the possibility of a decrease in side cut resistance due to protrusions such as stones. It is in.

  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 disposed on the outer peripheral side of the crown region of the carcass, assembled in an applicable rim, and within a cross-section in the width direction of the unloaded tire filled with a specified internal pressure, The distance m in the radial direction from the tread center at the end of the inclined region of the tread rubber that is inclined inward in the radial direction from the tread grounding end toward the outer side in the tire width direction is 0.06SH to the tire cross-section height SH. A bending point is provided at a position of 0.20SH, and the maximum tire width position is located on the outer side in the tire width direction from the maximum carcass width position and the bending point. The angle α on the acute side with respect to the straight line in the radial direction connecting the intersection of the line segment passing through the maximum width position of the carcass to the tire outer surface parallel to the tire axis and the maximum position of the tire width is 0 <α ≦ The tire maximum satisfying the relationship of 30 °, the radial distance h from the tread center to the tire maximum width position satisfies the relationship of 0.20SH to 0.40SH with respect to the tire cross-section height SH, and passes through the tire maximum width position. The angle β of the acute angle plane with respect to the radial line segment connecting the position and the bending point satisfies the relationship 0 ≦ β <30 °, and passes through the bending point, and the radial direction of the straight line connecting the bending point and the tread contact edge The angle γ on the acute angle surface side with respect to the line segment satisfies the relationship of 35 to 75 °.

Here, “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, and in Europe, ETRTO (European Tire and Rim Technical Organization). STANDARDDS MANUAL, in the United States, the rim specified in TRA (THE TIRE and RIM ASSOCATION INC.) YEAR BOOK etc.
The “specified internal pressure” refers to the maximum air pressure specified by JATMA or the like.
“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. This refers to the maximum width position in the tire width direction cross section of one extending carcass, and when the carcass is composed of a plurality of carcass plies, it refers to the linear distance between the outermost carcass plies.
“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.
“Tire cross-section height SH” refers to a length that is 1/2 of the difference between the outer diameter of the unloaded tire and the rim diameter when the tire is mounted on an applicable rim and has a prescribed air pressure.

In such a tire, it is more preferable that the radius of curvature R between the bending point and the tread contact end satisfies 0.08SH to ∞.
Here, the curvature radius ∞ means that the surface is not a curve but becomes a linear plane.

  The pneumatic radial tire of the present invention is particularly directed to the outer side in the tire width direction from the tread grounding end of the tread rubber 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 maximum distance of the tire is provided at the end of the inclined region inclined inward in the radial direction by providing a bending point where the radial distance m from the tread center is 0.06 SH to 0.20 SH with respect to the tire cross-section height SH. Is located on the outer side in the tire width direction from the carcass maximum width position and the bending point, and passes through the carcass maximum width position, a straight line connecting the intersection point to the tire outer surface parallel to the tire axis and the tire maximum width position The angle α on the acute surface side with respect to the radial line segment satisfies the relationship 0 <α ≦ 30 °, and the radial distance h from the tread center to the tire maximum width position is the tire cross-section height. The angle β on the acute angle side with respect to the straight radial line segment that satisfies the relationship of 0.20SH to 0.40SH with respect to H and passes through the tire maximum width position and connects the tire maximum position and the bending point is 0 ≦ β < By satisfying the relationship of 30 ° and passing through the bending point, the angle γ on the acute surface side with respect to the straight line in the radial direction connecting the bending point and the tread grounding end satisfies the relationship of 35 to 75 °. In a state where a corresponding load is applied, as shown in FIG. 1, the buttress located in the outer region in the tire width direction of the tread ground contact end protrudes from the sidewall portion to the outer side in the tire width direction. Because the sidewall region bulges outward in the width direction of the tire and does not become wider than the buttress, even if a step such as a stone is stepped on, the side cut itself is not easily received in that region. Together, it is possible to reduce the amount of rubber will be positioned buttress. As a result, the side cut resistance of the tire and the suppression of the calorific value can be achieved at a high level.

  That is, when the angle α exceeds 30 °, the amount of buttress rubber increases, which may increase the amount of heat generated in the region.

  Further, when the distance h is less than 0.20SH, the amount of rubber that is positioned at the buttress increases, so that the rubber volume increases and the heat generation amount increases. On the other hand, when the distance h exceeds 0.40SH, the side cut There is a possibility that the side cut resistance cannot be improved in a region that is susceptible to damage, particularly in a region located radially inward of the buttress.

  If the angle β is 30 ° or more, the side cut resistance may not be improved.

  When the radial distance m is less than 0.06SH, the amount of rubber that will be positioned at the buttress increases, so the rubber volume increases and heat generation durability decreases, and when it exceeds 0.20SH, the side cut resistance is improved. It may not be possible.

  Also, if the angle γ is less than 35 °, the amount of rubber that will be positioned at the buttress increases, resulting in an increase in rubber volume and reduced heat generation durability. If the angle γ exceeds 75 °, the tread tread has a concave shape. In addition, the wear resistance may be deteriorated.

An embodiment of a heavy-duty radial tire is assembled with an applied rim, filled with a specified air pressure, and a half-section of a width direction cross section during load rolling in a state where a load corresponding to a specified mass is applied. FIG. It is a figure which shows the tire width direction cross section of a no-load state which assembled | assembled one embodiment of the radial tire for heavy loads to the application rim, and was filled with the regular air pressure about the half part of a tire. It is a figure which shows the tire width direction cross section of a no-load state which assembled other embodiment of the radial tire for heavy loads to the application rim, and was filled with the regular air pressure about the half part of a tire. FIG. 6 is a diagram schematically showing a half section of a cross section in a width direction during load rolling in a state where a conventional tire is assembled to an applicable rim, filled with a specified air pressure, and a load corresponding to a specified mass is applied. is there.

The heavy duty radial tire of the present invention will be described in detail below with reference to the drawings.
In FIG. 2, which shows an embodiment of a heavy duty radial tire, in the figure, 1 is a tread portion, 2 is a pair of sidewall portions extending radially inward continuously to the respective side portions of the tread portion 1, and 3 Indicates bead portions continuous inward in the radial direction of the sidewall portion 2.

The heavy-duty radial tire shown in the figure has a main 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 5b. A radial carcass 5 made of a single carcass ply is provided around the bead core 4 and folded back from the inside in the tire width direction toward the outside.
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 folded portion 5b extends from 0.41 to 0.53% of the tire cross-section height SH as measured from the rim diameter line.

Further, in the figure, a belt 6 and a tread rubber 7 composed of four cord crossing belt layers are sequentially arranged on the outer peripheral side of the crown region of the carcass 5, and from the tread contact width end position E to the tire maximum width position B. Let the area be a buttress 8.
Although not shown in the drawing, a plurality of lateral grooves extending in the tread width direction are formed on the surface of the tread rubber 7.
The “tread contact width” means contact with the flat plate when a tire is mounted on the applicable rim, set to the specified air pressure, placed in a stationary state perpendicular to the flat plate, and a load corresponding to the specified mass is applied. It shall be the maximum linear distance in the tire axial direction on the surface.

  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 disposed along the outer surface thereof.

  In the radial tire for heavy loads, the radial distance m from the tread center at the end of the inclined region 9 of the tread rubber 7 inclined radially inward from the tread ground end E toward the outer side in the tire width direction is the tire. A bending point T is provided at a position of 0.06 SH to 0.20 SH, preferably 0.06 to 0.10 with respect to the cross-section height SH, and the tire maximum width position is the tire width from the carcass maximum width position and the bending point T. The angle α on the acute surface side with respect to the radial line segment of the straight line connecting the intersection A to the tire outer surface of the line segment parallel to the tire axis and passing through the carcass maximum width position, which is located on the outer side in the direction and the tire maximum width position Satisfies the relationship 0 <α ≦ 30 °, preferably 5 ° ≦ α ≦ 10 °, and the radial distance h from the tread center C to the tire maximum width position is relative to the tire cross-section height SH. .20SH to 0.40SH, preferably 0.28SH to 0.36SH, on the acute angle plane side with respect to the straight radial line segment connecting the tire maximum position and the bending point T passing through the tire maximum width position B Angle β satisfying the relationship of 0 ≦ β <30 °, preferably 5 ° ≦ β ≦ 10 °, passing through the bending point T, an acute angle surface with respect to the straight line segment connecting the bending point T and the tread ground contact E The angle γ on the side satisfies the relationship of 35 to 75 °, preferably 50 to 70 °.

FIG. 3 is a view showing a tire width direction cross section in a no-load state with respect to a half portion of the tire by assembling another embodiment of the heavy-duty radial tire of the present invention to an applicable rim and filling a prescribed air pressure. .
In addition, the same code | symbol is attached | subjected to the element similar to the tire shown in previous FIG. 2, and the description is abbreviate | omitted.
In this embodiment, the radius of curvature R between the bending point T and the tread ground contact edge E preferably satisfies 0.08SH to ∞.

  If the radius of curvature R is less than 0.08SH, a sufficient heat generation reduction effect cannot be obtained, and if a recess is formed between the bending point T and the tread grounding end E, the side-cut property may be reduced.

Next, tires having a structure as shown in FIGS. 2 and 3 and having a size of 26.5R25VSMS were manufactured as prototypes. For each tire, the side cut resistance and 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 Example Tires 1 and 2 and Comparative Example Tire is assembled on a 22.00 / 3.0 rim, the internal pressure is 650 kPa and the load mass is 18500 kg. Each tire after a year was sampled and evaluated by the number of failures / 50. The evaluation results are shown in Table 2.

(Heat generation durability)
Each of Example Tires 1 and 2 and Comparative Example Tire was assembled on a 22.00 / 3.0 rim, the internal pressure was 650 kPa, the load mass was 18500 kg, and the test speed was 5 km / h with a drum tester. Traveling for a while, measured from the tread center C, and assuming a position Q up to ¼ of the distance TW between the tread center C and the turning point T, the virtual straight line descending perpendicular to the carcass from this position Q The temperature at a position P of 1.5 mm was measured on the tread surface side of the outer belt layer, and the evaluation results are shown in Table 2.

From Table 2, the example tires 1 and 2 were able to improve the side cut resistance by 30% with respect to the comparative example tire.
Moreover, from Table 2, the heat generation durability of Example tires 1 and 2 was equivalent to that of the comparative tire.

  From the above results, Example Tires 1 and 2 were able to improve the side cut resistance without lowering the heat generation durability compared to the Comparative Example Tire.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Radial carcass 5a Body part 5b Folding part 6 Belt 7 Tread rubber 8 Buttress 9 Inclined area

Claims (2)

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 a pneumatic radial tire comprising a tread rubber arranged,
In the width direction cross section of the unloaded tire that is assembled to the applicable rim and filled with the specified internal pressure, the tread rubber has an inclined region that inclines radially inward from the tread grounding end toward the outside in the tire width direction. A bending point is provided at a position where the radial distance m from the tread center is 0.06 SH to 0.20 SH with respect to the tire cross-section height SH,
The maximum tire width position is located outside the carcass maximum width position and the bending point in the tire width direction,
The angle α on the acute angle side with respect to a straight line in the radial direction connecting the intersection of the line parallel to the tire axis and the tire outer surface passing through the carcass maximum width position and the tire maximum width position is 0 <α ≦ 30 Meet the relationship of °
The radial distance h from the tread center to the tire maximum width position satisfies the relationship of 0.20 SH to 0.40 SH with respect to the tire cross-section height SH, and connects the tire maximum position and the bending point passing through the tire maximum width position. The angle β on the acute surface side with respect to the straight radial line segment satisfies the relationship of 0 ≦ β <30 °,
A pneumatic radial tire characterized in that the angle γ on the acute angle side with respect to a straight line in a radial direction connecting the bending point and the tread grounding end passing through the bending point satisfies a relationship of 35 to 75 °.   The pneumatic radial tire according to claim 1, wherein a radius of curvature R between the bending point and the tread ground contact end satisfies 0.08SH to ∞.

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