JP5465990B2 - Heavy duty pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a heavy-duty pneumatic radial tire suitable for use in a construction vehicle, and suppresses occurrence of side cut failure when stepping on a protrusion such as a stone on a running road, and a tread. The present invention relates to a heavy-duty pneumatic radial tire in which the heat generation amount of rubber is suppressed.

  The heavy-duty pneumatic tire used for construction vehicles that run on rocky roads such as underground mines is shown in FIG. The portion 22 is greatly bulged and deformed outward in the tire width direction. For this reason, there is a high possibility that a side cut will occur in the sidewall portion 22 due to protrusions such as stones that come into contact with the rolling of the tire, and if this side cut reaches the carcass of the tire, a failure such as puncture may occur. was there.

  Therefore, conventionally, for 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, in a bias tire having a thick cord crossing layer, side cut scratches do not easily penetrate to the inner surface of the tire, and there is an advantage of excellent side cut resistance.

  On the other hand, radial tires are advantageous in terms of manufacturing man-hours and cost, and are excellent in terms of wear resistance, traction performance, weight, etc., but in this type of heavy-duty pneumatic radial tire, in the sidewall portion, For example, in many cases, only one carcass ply made of steel cord is arranged, and along with this, the rubber thickness of the side wall portion is also reduced, so there is a risk that the side cut can easily penetrate the carcass and cause a failure. it was high.

  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 technique for improving the side cut resistance has been proposed, the side cut resistance has not yet been improved to the same level as that of the bias tire.

  Moreover, in order to make it difficult to receive the side cut itself, for example, as described in Patent Document 2, the outer surface width of the tire is set within the cross section in the width direction of the unloaded normal tire that is attached to the applied rim and filled with the internal pressure. , Gradually increasing from the maximum width position of the carcass layer to a position in the range separated by 0.3 to 0.7 times the radial distance from the tread edge, and between the position of the range and the tread edge By gradually decreasing, even when the sidewall portion bulges outward in the tire width direction due to heavy load, the technology that prevents the occurrence of side cuts by making the sidewall portion substantially perpendicular to the road surface Proposed.

  However, in the tire described in Patent Document 2, the thickness of the buttress rubber in the outer region in the tire width direction of the tread grounding end is increased, the rubber volume is increased, and the heat generation amount of the tread rubber is increased, whereby the tread rubber is increased. There was a risk that the durability of the steel would decrease.

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

  Therefore, the present invention reduces the heat generation amount of the tread rubber without reducing the side cut resistance to the projections such as stones during traveling, and can reduce the durability of the tread rubber. An object is to provide a heavy duty pneumatic radial tire.

  The inventors have been diligently studying a way to develop a heavy-duty pneumatic radial tire in which the above-mentioned side-cut resistance and low heat generation are compatible at a high level. The inventors have found that it is effective to design the tire by optimizing the arrangement of the base rubber, and have completed the present invention. Therefore, the gist configuration of the present invention for solving the above-described problems is as follows.

(1) A tread portion, a pair of sidewall portions, a pair of bead portions, a radial carcass composed of at least one carcass ply extending in a toroid shape between bead cores in each bead portion, and a crown region of the carcass In a pneumatic radial tire including a tread rubber formed by sequentially arranging a base rubber and a cap rubber from the inner peripheral side on the outer peripheral side
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,
Parallel to the tire equator plane, the straight line connecting the intersection of the virtual straight line parallel to the rim diameter line passing through the carcass maximum width position and the tire outer surface and the tire maximum width position located outside the tire radial direction from the intersection The inclination angle α with respect to a straight line is 0 ° <α ≦ 30 °,
An inclination angle β of a straight line connecting the tire maximum width position and the tread ground contact edge with respect to a straight line parallel to the tire equator plane is 0 ° ≦ β <30 °,
The tire radial direction distance h from the tread center to the tire maximum width position is 0.20SH ≦ h ≦ 0.40SH with respect to the tire cross-section height SH,
A straight line drawn from the outermost position in the tire radial direction of the boundary line between the base rubber and the cap rubber to the intersection with the tread side surface of the boundary line in the outermost region obtained by dividing the tread contact width into four equal parts. The inclination angle γ with respect to a virtual straight line parallel to the rim diameter line is 0 ° ≦ γ ≦ 20 °, and the rebound resilience of the base rubber is 1.42 to 2.0 times the rebound resilience of the cap rubber A pneumatic radial tire characterized by being.

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.) It shall mean the rim specified in YEAR BOOK, etc.
The “specified internal pressure” refers to the maximum air pressure 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 extending is referred to. In the case of a plurality of carcass plies, the maximum width position of the outermost carcass ply is referred to.

“Tire cross section height SH” refers to ½ of the difference between the outer diameter of the tire and the rim diameter.
“Tread contact width” refers to the flat plate when the tire is mounted on the applicable rim, filled with the specified internal pressure, placed perpendicular to the flat plate, and loaded with a load corresponding to the maximum load capacity specified in JATMA standards. The maximum distance in the tire axial direction on the contact surface shall be said.

  “Rebound resilience (%)” refers to a numerical value measured according to a test method of a rebound resilience test specified in JIS K6255.

(2) The pneumatic radial tire according to (1), wherein the inclination angle α is 5 ° ≦ α ≦ 10 °.

(3) The pneumatic radial tire according to (1) or (2), wherein the inclination angle β is 5 ° ≦ β ≦ 10 °.

(4) The pneumatic radial tire according to any one of (1) to (3), wherein the distance h is 0.28SH ≦ h ≦ 0.36SH.

(5) The pneumatic radial tire according to any one of (1) to (4), wherein a rebound resilience of the base rubber is 1.56 times a rebound resilience of the cap rubber.

  FIG. 1 shows the pneumatic radial tire of the present invention in a state where a load corresponding to a specified mass is applied. The pneumatic radial tire has a shape in which the buttress 8 protrudes outward in the tire width direction and reaches the tire maximum width position in the cross section in the tire width direction in an unloaded state. On the inner side in the direction, the tire width is gradually reduced. For this reason, when the inner portion in the tire radial direction of the sidewall portion 2 bulges outward in the tire width direction due to the action of the load, as shown in FIG. 1, it extends from the buttress to the lower portion of the sidewall portion 2 with respect to the road surface. It will take an almost vertical posture and it is difficult to receive side cuts.

  Further, in the pneumatic radial tire of the present invention, the inclination angle α is set to 30 ° or less, whereby the rubber thickness of the buttress of the tire is increased and the rubber volume is increased while exhibiting the effect of suppressing the side cut. Is prevented from increasing. That is, it is possible to suppress an increase in the amount of heat generated by the tread rubber due to an increase in the rubber volume of the buttress.

  Further, by setting the inclination angle β to 30 ° or less and the tire radial distance h to 0.40 SH or less, it is possible to prevent the buttress rubber thickness of the tire from becoming too thin and to reduce the tire tread contact width. This prevents the wear resistance from decreasing.

  On the other hand, since the tire radial distance h is not less than 0.20, the tire volume of the buttress of the tire does not increase so much that the amount of heat generated by the tread rubber does not increase.

  In consideration of the balance between the side cut resistance and the buttress rubber volume, the inclination angle α is preferably in the range of 5 ° ≦ α ≦ 10 °. Thereby, it is possible to more effectively suppress an increase in the heat generation amount of the tread rubber while improving the side cut resistance.

  Further, in order to achieve compatibility with various tire performances such as wear resistance, the inclination angle β is preferably 5 ° ≦ β ≦ 10 °, and by setting β to 5 ° or more, the rubber volume of the buttress is increased. By reducing the heat generation amount of the tread rubber more effectively, and by making β less than 10 °, it is possible to more effectively prevent a decrease in the tread contact surface of the tire, for example, wear resistance. It is possible to prevent the influence on various tire performances.

  The pneumatic tire of the present invention further effectively obtains the effect of improving the side cut resistance and the effect of reducing the calorific value of the tread rubber by making the tire radial distance h 0.36 SH or less. Is possible.

  In the tires described above, when the impact resilience of the base rubber is 1.56 times the resilience resilience of the cap rubber, various performances such as wear resistance and side cut resistance are balanced in the most balanced manner. It is possible to make it.

The pneumatic radial tire according to the present invention is assembled to an applicable rim, filled with a specified air pressure, and schematically shown when it is rolled by applying a load corresponding to a specified mass. FIG. FIG. 2 is a cross-sectional view in the width direction of a half portion of the tire showing a state in which the pneumatic radial tire of the present invention is assembled to an applied rim, filled with a prescribed air pressure, and brought into an unloaded state. FIG. 3 is an enlarged cross-sectional view of a main portion centering around a tread portion of the pneumatic radial tire of FIG. 2. It is a width direction sectional view showing the case where a conventional tire is assembled to an applicable rim, filled with a specified air pressure, and rolled by applying a load corresponding to a specified mass.

The heavy duty radial tire of the present invention will be described in detail below with reference to the drawings.
In FIG. 2, 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 is a radius of each sidewall portion 2. Each bead portion continues inward in the direction.

  The illustrated pneumatic radial tire includes at least one radial carcass 5 composed of at least one carcass ply extending in a toroidal shape between bead cores 4 in each bead portion 3, and at least the outer peripheral side of the crown region of the carcass 5. A belt 6 composed of two steel belt layers, and a tread rubber 7 composed of a base rubber 7a and a cap rubber 7b arranged sequentially on the outer peripheral side of the belt 6.

  Here, in the illustrated pneumatic tire, a hypothesis parallel to the rim diameter line passing through the maximum width position of the carcass 5 in the cross-section in the width direction of the unloaded tire that is assembled to the applicable rim R and filled with the prescribed internal pressure. The inclination angle α of the straight line b connecting the intersection point p between the straight line a and the tire outer surface and the tire maximum width position 9 located on the outer side in the tire radial direction with respect to the straight line c parallel to the tire equatorial plane CL, 0 ° <α ≦ 30 °.

  Further, here, the inclination angle β of the straight line connecting the tire maximum width position 9 and the tread ground contact edge 10 to the inner side in the tire width direction with respect to the straight line d parallel to the tire equatorial plane CL is 0 ° ≦ β <30 °. The outermost region where the tire radial distance h from the tread center to the tire maximum width position 9 is 0.20SH ≦ h ≦ 0.40SH with respect to the tire cross-section height SH, and the tread ground contact width TW is divided into four equal parts. In G, a straight line e drawn from the outermost position A in the tire radial direction of the boundary line BL between the base rubber 7a and the cap rubber 7b to the intersection with the tread side surface of the boundary line BL is parallel to the rim diameter line. An inclination angle γ inward in the tire radial direction with respect to the imaginary straight line f is 0 ° ≦ γ ≦ 20 °, and the rebound resilience of the base rubber 7a is 1.42 to the rebound resilience of the cap rubber 7b. 2.0 times It is important to

  In the illustrated example, the radial carcass 5 of a pneumatic tire has a main body portion 5a extending in a toroidal shape between bead cores 4 having a hexagonal cross section embedded in each bead portion 3, and a side portion 5b. The side portion 5b can be folded around the bead core 4 from the outer side toward the inner side in the tire width direction. is there.

  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. Further, the side portion 5b of the carcass can be extended to a range of 0.30 to 0.46% of the tire cross-section height SH as measured from the rim diameter line.

  The belt 6 is formed of four layers of cord crossing belts in the figure, and a plurality of transverse grooves extending in the tread width direction are formed on the surface of the tread rubber 7 although not shown in the figure. .

Hereinafter, the configuration characterizing the present invention will be described in more detail.
Conventionally, when a tire for a construction vehicle travels on a rocky road such as an underground mine, as in the example shown in FIG.

  On the other hand, in order to prevent the side cut while suppressing the increase in the rubber volume of the buttress of the tire, it is first necessary to set the inclination angle α to be greater than 0 °. That is, when the inclination angle is 0 ° or less, when the tire receives a load and the sidewall portion 2 bulges, the buttress 8 can protect the sidewall portion 2 from protrusions such as stones on the runway. This is because it disappears.

On the other hand, as the inclination angle α is increased, the rubber volume of the buttress of the tire increases, and the amount of heat generated by the tread rubber 7 tends to increase. Therefore, the inclination angle α is 30 ° or less. There is a need.
If the inclination angle α is 30 ° or less, the amount of heat generated by the tread rubber 7 does not increase so much.

In the present invention, when the inclination angle β is too large, the rubber thickness of the buttress 8 becomes too thin to ensure sufficient side cut resistance, and the tread contact width of the tire is reduced. Doing so may affect the wearability.
Therefore, the inclination angle β needs to be smaller than 30 °. Therefore, the inclination angle needs to satisfy 0 ° ≦ β <30 °.

By the way, since it is the area | region away 0.40SH or more from the tire contact surface center area | region in the tire radial direction inside that a tire receives a side cut, the said distance h needs to be 0.40SH or less. . On the other hand, if h is less than 0.20SH, the buttress rubber volume increases too much and the amount of heat generated by the tread rubber 7 increases.
Therefore, the distance h needs to satisfy 0.20SH ≦ h ≦ 0.40SH with respect to the tire cross-section height SH.

  In the present invention, from the outermost position in the tire radial direction of the boundary line BL between the base rubber 7a and the cap rubber 7b in the outermost region G obtained by equally dividing the tread contact width TW into four, Further ensuring the wear resistance of the tire by setting the inclination angle γ of the straight line e drawn at the intersection with the side surface of the tread with respect to the virtual straight line f parallel to the rim diameter line to 0 ° ≦ γ ≦ 20 °. Can do.

Usually, in the tread rubber 7 of a tire, it is common to use a material with a small amount of heat generation for the base rubber 7a, and a material having excellent wear resistance for the cap rubber 7b. Therefore, as shown in FIGS. 2 and 3, when the inclination angle γ of the straight line e that forms the boundary of each rubber with respect to the virtual straight line f parallel to the rim diameter line is less than 0 °, wear resistance is ensured. The unobtainable base rubber 7a is exposed to the tread contact surface at an early stage of wear, and the wear resistance of the tire is impaired. On the other hand, when the inclination angle γ exceeds 20 °, the effect of reducing the amount of heat generated when compared with the conventional product cannot be sufficiently obtained.
Therefore, the inclination angle γ needs to satisfy 0 ° ≦ γ ≦ 20 °.

  In the tire according to the present invention, the rebound resilience of the base rubber 7a is 1.42 to 2.0 times the rebound resilience of the cap rubber 7b.

  When the rebound resilience of the base rubber 7a is less than 1.42 times the rebound resilience of the cap rubber 7b, the amount of heat generated by the tread rubber 7 cannot be reduced to an effective level. By the way, rubber having a high impact resilience is generally inferior to other performance such as wear resistance. Therefore, when the resilience resilience of the base rubber 7a exceeds 2.0 times the resilience resilience of the cap rubber 7b, Not suitable for actual use. Therefore, the rebound resilience of the base rubber 7a needs to be 1.42 to 2.0 times the rebound resilience of the cap rubber 7b.

In the tire having the above configuration, the inclination angle α is more preferably 5 ° ≦ α ≦ 10 °.
If the inclination angle α is within the above range, the balance between the suppression of the heat generated by the buttress and the side cut resistance of the tire can be further enhanced.

Furthermore, in this tire, the inclination angle β is preferably 5 ° ≦ β ≦ 10 °.
Similarly to the above-described case, by setting the inclination angle β within the above range, it is possible to achieve both balance between the suppression of the amount of heat generated by the buttress and the side cut resistance of the tire in a balanced manner.

In this tire, the distance h is preferably 0.28SH ≦ h ≦ 0.36SH.
According to this, while suppressing generation | occurrence | production of the cut to buttress itself, the increase in the emitted-heat amount of the tread rubber 7 can be suppressed more effectively by making the said distance 0.28 or more. it can.

In the tire as described above, it is preferable that the rebound resilience of the base rubber 7a is 1.56 times the rebound resilience of the cap rubber 7b.
When the rebound resilience of the base rubber 7a is 1.56 times the rebound resilience of the cap rubber 7b, the tire wear resistance and the low heat build-up can be achieved with the best balance.

  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 temperature of the tread rubber were measured.

(Side cut resistance)
50 tires of each of the example tires and the comparative example tires were put on the market, the tires after one year were sampled, and the number of cut failures / number of test tires was investigated. The evaluation results are shown in Table 1.

(Exothermic temperature)
Each of the example tire and the comparative example tire was assembled on a rim of 22.00 / 3.0, the internal pressure was 650 kPa, the load weight was 18500 kg, and the drum was tested for 24 hours at a test speed of 5 km / h. The temperature on the point P shown in FIG. 3 was measured and evaluated. The evaluation results are shown in Table 1. The point P is a point on the vertical line 1.5 mm away from the intersection of the perpendicular line drawn from the tread end to the thickness center line of the radial carcass 5 and the surface of the carcass on the cross section in the width direction of the tire. .

  From Table 1, the heat generation temperature of the tread rubber of the comparative example tire is as high as 116 ° C., whereas in the tires 1 to 3 of the present invention, all of the heat generation temperatures are as low as 111 ° C. or less. Recognize. Here, if the heat generation temperature of the tread rubber is 112 ° C. or less, there is no problem due to the heat generation, and it can be said that there is no problem in the market.

  In addition, the Example tires 1 to 3 are superior to the comparative example tire 1 in terms of side cut resistance. Therefore, from the above results, it can be said that the Example tires 1 to 3 have improved side-cut resistance without increasing the heat generation temperature of the tread rubber compared to the comparative tires 1 and 2.

CL equatorial plane 1 tread portion 2 sidewall portion 3 bead portion 4 bead core 5 radial carcass 5a body portion 5b folded portion 6 belt 7 tread rubber 7a base rubber 7b cap rubber 8 buttress TW tread ground width SH tire cross-section height BL base rubber and Boundary line with cap rubber R Applicable rim

Claims (5)

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 in which a base rubber and a cap rubber are sequentially arranged from the inner peripheral side,
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,
Parallel to the tire equator plane, the straight line connecting the intersection of the virtual straight line parallel to the rim diameter line passing through the carcass maximum width position and the tire outer surface and the tire maximum width position located outside the tire radial direction from the intersection The inclination angle α with respect to a straight line is 0 ° <α ≦ 30 °,
An inclination angle β of a straight line connecting the tire maximum width position and the tread ground contact edge with respect to a straight line parallel to the tire equator plane is 0 ° ≦ β <30 °,
The tire radial direction distance h from the tread center to the tire maximum width position is 0.20SH ≦ h ≦ 0.40SH with respect to the tire cross-section height SH,
A straight line drawn from the outermost position in the tire radial direction of the boundary line between the base rubber and the cap rubber to the intersection with the tread side surface of the boundary line in the outermost region obtained by dividing the tread contact width into four equal parts. The inclination angle γ with respect to a virtual straight line parallel to the rim diameter line is 0 ° ≦ γ ≦ 20 °, and the rebound resilience of the base rubber is 1.42 to 2.0 times the rebound resilience of the cap rubber A pneumatic radial tire characterized by being.   The pneumatic radial tire according to claim 1, wherein the inclination angle α is 5 ° ≦ α ≦ 10 °.   The pneumatic radial tire according to claim 1, wherein the inclination angle β is 5 ° ≦ β ≦ 10 °.   The pneumatic radial tire according to claim 1, wherein the distance h is 0.28SH ≦ h ≦ 0.36SH.   The pneumatic radial tire according to any one of claims 1 to 4, wherein a rebound resilience of the base rubber is 1.56 times a rebound resilience of the cap rubber.

Images