JP2005112042A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the durability of a bead part. <P>SOLUTION: The pneumatic tire comprises one carcass ply 6A having a body part 6a and a return part 6b returned around a bead core 5, bead apex 8 and one reinforcement ply 9 of substantially U-shaped section. At the intermediate position KC of the line K to connect the maximum width position 5a outside the bead core 5 to an outer end 6be of the return part 6b, the rubber thickness A between the body part 6a and the return part 6b is 63-100% of the maximum width X of the bead core, the rubber thickness B between the body part 6a and the return part 6b at the outer end 6be of the return part 6b is 60-100% of the rubber thickness A, and the rubber thickness C from an outer end 9ie of an inner ply part 9i to an inner cavity surface 10 of the tire is 22-40% of the rubber thickness A. The rubber thickness of an insulation rubber 11 between the inner ply part 9i and the body part 6a is determined so that the height h from the bead base line BL is larger than the thickness below 69% in the range S of ≥ 69% of the outer end height Z of the inner ply part 9i. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heavy duty pneumatic tire capable of improving the durability of a bead portion.

  Heavy duty pneumatic tires used for trucks, buses and the like have a single carcass ply made of steel cord. The carcass ply usually includes a main body portion that extends in a toroidal shape between a pair of bead cores, and a folded portion that is continuous with the main body portion and is folded around the bead core from the inner side toward the outer side in the tire axial direction. Since heavy duty pneumatic tires are used under severe conditions such as high internal pressure and high load, large distortion tends to occur in the bead portion. If the vehicle runs continuously while receiving such distortion, the internal temperature of the bead portion rises, and as a result, damage such as peeling is likely to occur at the end portion of the folded portion having low adhesion to rubber.

  Conventionally, in order to prevent such damage to the bead portion, as shown in FIG. 4, a method of arranging a reinforcing ply a made of a steel cord or a nylon cord outside the carcass ply b (see Patent Document 1 below), A method for increasing the rubber volume of the bead portion, particularly a bead apex c disposed between the main body portion and the folded portion, and a method for regulating physical properties of these rubbers (see Patent Document 2 below), etc. Are known.

JP 2001-10312 A JP 2002-178724 A

  A certain degree of effect can be obtained by the above-described method for preventing the carcass ply b from peeling off at the folded portion b1. However, as a result of various experiments, it has been found that when the reinforcing ply a is provided, the outer end a1e of the inner ply portion a1 that is the inner portion of the reinforcing ply a in the tire axial direction is likely to be a new damage starting point. In order to prevent such damage, by increasing the thickness of the inner rubber portion e adjacent to the outer end a1e, the shearing force acting on the outer end a1e is alleviated, and absorption and bending rigidity are increased. It is possible.

  However, unnecessarily increasing the rubber thickness of the inner rubber portion e is not preferable because it increases tire weight and manufacturing cost. In particular, an increase in tire weight is not preferable because it causes further deterioration in fuel consumption in a truck or the like that consumes a large amount of fuel. Surprisingly, it has been found that the detachment of the outer end a1e cannot be effectively prevented by simply increasing the thickness of the inner rubber portion e.

  The present invention has been devised in view of the above problems, and defines the height of the folded portion of the carcass ply, the height of the inner ply portion of the reinforcing ply, the height of each outer end of the outer ply portion, and the like. In addition, on the basis of prescribing the rubber thickness between the carcass ply body and the folded portion, the peeling at the outer ends of the folded portion, the inner ply portion of the reinforcing ply, and the outer ply portion is performed over a long period of time. It is an object of the present invention to provide a heavy duty pneumatic tire that can be suppressed and improve the durability of the bead portion.

The invention according to claim 1 of the present invention comprises a main body portion straddling a toroidal shape between a pair of bead cores, and a folded portion that is connected to the main body portion and folded around the bead core from the inner side to the outer side in the tire axial direction. A carcass composed of one carcass ply, a bead apex extending from the outer surface of the bead core in the tire radial direction, an inner ply portion disposed on the inner side in the tire axial direction of the main body portion in the bead portion, and a tire axial direction of the folded portion A reinforcing ply having a substantially U-shaped cross section having an outer ply portion arranged on the outer side and a joint portion connecting the inner ply portion and the outer ply portion, and includes the following a) to g) A heavy-duty pneumatic tire characterized by meeting the requirements.
a) The outer end height Z of the inner ply portion of the reinforcing ply is 18.4 to 29.5% of the tire cross-section height H.
b) The difference (W−Y) between the outer end height W of the folded portion of the carcass ply and the outer end height Y of the outer ply portion of the reinforcing ply is positive and the outer end height Y of the outer ply portion is 7. 0-86.0%
c) The outer end height W of the folded portion of the carcass ply is 56 to 86% of the outer end height Z of the inner ply portion of the reinforcing ply.
d) The rubber thickness A between the main body portion and the folded portion is equal to the maximum width X of the bead core at the middle position of the straight line connecting the maximum width position on the outer side of the bead core in the tire axial direction and the outer end of the folded portion of the carcass ply. 63-100%
e) The rubber thickness B between the main body portion and the folded portion at the outer end of the folded portion of the carcass ply is 60 to 100% of the rubber thickness A.
f) The rubber thickness C from the outer end of the inner ply portion to the tire cavity surface is 22 to 40% of the rubber thickness A.
g) The rubber thickness between the inner ply portion and the carcass ply main body portion is less than 69% when the height h from the bead base line is 69% or more of the outer end height Z of the inner ply portion. Greater than range thickness

  According to a second aspect of the present invention, the bead apex has a complex elastic modulus of 10 to 70 MPa, a loss tangent tan δ of 0.120 to 0.220, and an inner end side in a tire radial direction is connected to the bead apex. In addition, the complex elastic modulus of the packing rubber whose outer end extends in the tire radial direction along the main body portion of the carcass ply is 2.8 to 4.8 MPa, and the loss tangent tan δ is 0.050 to 0.120. Moreover, the complex elastic modulus of the small side packing rubber disposed between the packing rubber and the folded portion and the insulation rubber disposed between the main body portion and the inner ply portion is 8.0 to 14. The heavy-duty pneumatic tire according to claim 1, wherein the loss tangent tan δ is 0.0 MPa and 0.085 to 0.150.

  The complex elastic modulus and loss tangent tan δ are 4 mm wide × 30 mm long × 1.5 mm thick strip samples, using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., temperature 70 ° C., initial strain It is a value measured under the conditions of 10%, frequency 10 Hz, and dynamic strain 2%.

  The invention according to claim 3 is the heavy duty pneumatic tire according to claim 1 or 2, wherein the carcass is made of a steel cord and is attached to a 15 ° deep bottom rim.

  According to a fourth aspect of the present invention, at least a portion of the tire lumen surface includes 60 to 100 parts by weight of a halogenated butyl rubber and 0 to 40 parts by weight of a diene rubber among 100 parts by weight of a rubber polymer. The heavy duty pneumatic tire according to any one of claims 1 to 3, wherein a composition is disposed.

  The pneumatic tire of the present invention defines the height of the folded portion of the carcass ply, the inner ply portion of the reinforcing ply, the height of each outer end of the outer ply portion, and the like, and defines the main body portion and the folded portion of the carcass ply. By prescribing the rubber thickness, etc., it is possible to suppress peeling at the outer end of the folded portion, the inner ply portion of the reinforcing ply, and the outer ply portion over a long period of time, and the durability of the bead portion can be improved. .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view of a heavy load pneumatic tire 1 used for heavy vehicles such as trucks (including small trucks) and buses in a reference state, and FIG. 2 is a partially enlarged view of a bead portion 4 thereof. In this example, a tubeless type attached to a 15-degree deep rim is illustrated.

  The reference state is defined as an unloaded state in which a tire is assembled on a regular rim J and filled with a regular internal pressure. The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based, and is a standard rim for JATMA, “Design Rim” for TRA, For ETRTO, use “Measuring Rim”. In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure for JATMA and the table “TIRE LOAD LIMITS AT for TRA” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “INFLATION PRESSURE”.

  In the figure, a heavy-duty pneumatic tire 1 is provided at a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and an inner end portion of each sidewall portion 3. Provided with a bead portion 4. The heavy-duty pneumatic tire 1 of the present embodiment is reinforced by a carcass 6, a belt layer 7, a bead apex 8 and a reinforcing ply 9.

  The carcass 6 includes a main body portion 6a straddling a pair of bead cores 5 and 5 in a toroidal shape, and a turn-up portion 6b which is connected to the main body portion 6a and is turned around the bead core 5 from the inner side to the outer side in the tire axial direction. It is composed of one carcass ply 6A. The carcass ply 6A is formed by a ply in which a carcass cord is covered with a topping rubber. For example, a radial structure in which the carcass cord is arranged at an angle of 80 to 90 ° (90 ° in this example) with respect to the tire equator C is employed. A steel cord is suitable for the carcass cord in order to support a high load.

  In this example, the belt layer 7 is formed by stacking four belt plies 4A, 4B, 4C and 4D each having a belt cord made of steel. As an example, the inner belt ply 7A disposed on the innermost side in the tire radial direction is disposed with the belt cord inclined with respect to the tire equator C at an angle of, for example, about 60 ± 10 °. Further, the belt plies 7B, 7C and 7D tilt the belt cord at a small angle of 15 to 30 ° with respect to the tire equator C, and at least two of the plies are arranged in a direction in which the belt cords cross each other. The Each belt ply has a different width in the tire axial direction. Such a configuration of the belt layer 7 is an example, and can be appropriately changed as necessary.

  The reinforcing ply 9 is constituted by a single ply formed by covering a steel cord with a topping rubber. Further, the reinforcing ply 9 is disposed along the main body portion 6a of the carcass ply 6A in the bead portion 4 and on the inner side in the tire axial direction, and along the folded portion 6b and on the outer side in the tire axial direction. It has an outer ply portion 9o, and an arc-shaped joint portion 9c that smoothly joins the inner ply portion 9i and the outer ply portion 9o along the bead core. Thereby, the reinforcement ply 9 is substantially U-shaped in the tire meridian cross section.

  The steel cord of the reinforcing ply 9 is desirably disposed at an angle θ of 45 to 80 degrees, more preferably 55 to 70 degrees with respect to the carcass cord, for example. If the angle θ is less than 45 degrees, the steel cord of the reinforcing ply 9 approaches parallel to the radial carcass cord, so that the bend portion is remarkably impaired and the ride quality tends to deteriorate. Conversely, when the angle θ exceeds 80 degrees, the effect of reinforcing the bending rigidity of the bead portion 4 tends to be reduced.

  In addition, the bead apex 8 is provided between the main body portion 6a and the turn-up portion 6b of the carcass ply 6A so as to taper from the outer surface of the bead core 5 to the outer side in the tire radial direction. The bead apex 8 preferably has a complex elastic modulus of 10 to 70 MPa, more preferably 15 to 60 MPa, and a loss tangent tan δ of 0.120 to 0.220, more preferably 0.135 to 0.200. It is desirable to be formed by. If the complex elastic modulus of the bead apex 8 is less than 10 MPa, it becomes difficult to give the bead portion 4 sufficient bending rigidity that can withstand a high load, and the rolling resistance tends to deteriorate. On the other hand, if it exceeds 70 MPa, the rigidity of the bead part 4 is excessively increased, a rigidity step is likely to occur between the side wall part 3 and the like, and the ride comfort tends to be remarkably deteriorated. Further, if the loss tangent tan δ of the bead apex 8 is less than 0.120, it is excellent in terms of low heat build-up, but it is not preferable because the tear resistance tends to decrease, and conversely if it exceeds 0.200. The heat generation of the bead apex 8 is increased and the durability tends to be lowered.

  The bead apex 8 has a height Ha from the bead base line BL of 10.0 to 35.0%, preferably 12.3 to 28.6%, more preferably 15.0 to 25% of the tire cross-section height H. 0.0% is desirable. If the height Ha is less than 10.0% of the tire cross-section height H, it tends to be difficult to ensure the bending rigidity of the bead portion 4, and conversely if it exceeds 35.0%, the bead portion 4. There is a tendency to excessively increase the bending rigidity of the vehicle and deteriorate the ride comfort.

  In addition, as shown in FIG. 2, the heavy load pneumatic tire 1 of the present embodiment is exemplified by one having a packing rubber 12 outside the bead apex 8 in the tire radial direction. The packing rubber 12 has an inner end in the tire radial direction connected to the bead apex 8 between the main body portion 6a and the folded portion 6b, and an outer end on the outer side in the tire radial direction along the main body portion 6a of the carcass ply 6A. Examples are those which extend in a tapered shape. Such a packing rubber 12 cooperates with the bead apex 8 to increase the bending rigidity of the bead portion 4, while giving appropriate flexibility to the sidewall portion 3, its complex elastic modulus is preferably 2.8. ˜4.8 MPa, more preferably 3.2 to 4.4 MPa, and loss tangent tan δ is preferably 0.050 to 0.120, more preferably 0.060 to 0.110. Further, the packing rubber 12 of this embodiment extends beyond the outer end of the folded portion 6b outward in the tire radial direction, and its height Hp is 23.6 to 45.6% of the tire cross-section height H, more preferably. It is desirable to set it as 26.0 to 42.0%.

  Moreover, the heavy duty pneumatic tire 1 of the present embodiment satisfies the following requirements a) to g). Hereinafter, it demonstrates in order.

  a) In the reinforcing ply 9, the outer end height Z of the inner ply portion 9i is 18.4 to 29.5% of the tire cross-sectional height H. The outer end height Z of the inner ply portion 9i is the height in the tire radial direction from the bead base line BL to the outer end 9ie of the inner ply portion 9i in the reference state. When there is no notice in particular, the height of each part is measured according to this. If the outer end height Z is less than 18.4% of the tire cross-section height H, the main body portion 6a of the carcass ply 6A cannot be effectively reinforced. Conversely, if it exceeds 29.5%, the inner ply Since the outer end 9ie of the portion 9i approaches the severely bent sidewall portion 3 or buttress portion, peeling or the like is likely to occur at an early stage. Particularly preferably, the outer end height Z is 19.0 to 25.0% of the tire cross-section height H, more preferably 20.0 to 24.0%.

  b) The difference (W−Y) between the outer end height W of the folded portion 6b of the carcass ply 6A and the outer end height Y of the outer ply portion 9o of the reinforcing ply 9 is positive and the outer end of the outer ply portion 9o. The height Y is 7.0 to 86.0%. By making the difference (W−Y) positive, the outer end 9 oe of the outer ply portion 9 o can be positioned on the inner side in the tire radial direction from the outer end 6 be of the turned-up portion 6 b. When the outer end 6be of the folded portion 6b and the outer ply portion 9o overlap each other, the overlapping portion tends to be a starting point of damage because of insufficient adhesive force. However, in the present invention, it is effective that such a portion is formed. Can be prevented.

  Further, when the difference (W−Y) is less than 7.0% of the outer end height Y, the outer end 6be of the folded portion 6b and the outer end 9oe of the outer ply portion 9o are close to each other. If it exceeds 86.0%, the outer end 9oe of the outer ply portion 9o is greatly separated from the outer end 6be of the folded portion 6b, and the folded portion 6b is reinforced. Effect is not sufficiently obtained, and the bead durability tends to decrease. It is particularly preferable that the difference (W−Y) is 10.0 to 50.0%, more preferably 20.0 to 50.0% of the outer end height Y of the outer ply portion 9o.

  c) The outer end height W of the folded portion 6b of the carcass ply 6A is 56 to 86% of the outer end height Z of the inner ply portion 9i of the reinforcing ply 9. If the outer end height W of the folded portion 6b is less than 56% of the outer end height Z of the inner ply portion 9i, the movement of the outer end 9io of the inner ply portion 9i during traveling increases, and the carcass ply 6A Separation is likely to occur due to stress concentration between the main body 6a and the outer end 9io, and if it exceeds 86%, the stress received from the wheel rim is received by the folded-back portion 6b and the effect of reinforcing cannot be sufficiently obtained. Therefore, none of them can be expected to improve bead durability. Particularly preferably, the outer end height W of the folded portion 6b is 59 to 81%, more preferably 63 to 77% of the outer end height Z of the inner ply portion 9i.

  The size of a pneumatic tire is increased by filling with internal pressure. At that time, the carcass ply 6A is pulled with the bead core 5 as a fulcrum. On the other hand, when a tire is loaded, the tire receives a falling force with the wheel rim as a fulcrum. In order to suppress this falling, it is effective to make the height Z of the inner ply portion 9i of the reinforcing ply 9 located on the main body side of the carcass ply 6A larger than the rim flange and the outer end 6be of the folded portion 6b. It is. That is, the height Z is preferably regulated in association with the height W. However, if the heights W and Z are excessively large, the cost increases, which is not preferable.

  d) Rubber thickness between the main body portion 6a and the folded portion 6b at an intermediate position KC of the straight line K connecting the maximum width position 5a on the outer side in the tire axial direction of the bead core 5 and the outer end 6be of the folded portion 6b of the carcass ply 6A. A is 63 to 100% of the maximum width X of the bead core 5. The maximum width position of the bead core 5 indicates the positions 5a and 5b at both ends of the maximum width X. Further, the maximum width X of the bead core 5 is measured only for the steel wire portion in the present example in which the bead core 5 is formed, and does not include a so-called wrapping rubber that wraps the steel core. The maximum width X of the bead core is not particularly limited, but is preferably 20 mm or more, more preferably 22 mm or more.

  The rubber thickness A is the rubber thickness between the carcass cord of the main body portion 6a and the carcass cord of the folded portion 6b (also measured for “rubber thickness B” described later). When the rubber thickness A is less than 63% of the maximum width X of the bead core 5, the rubber volume between the main body portion 6a and the folded portion 6b of the carcass ply 6A is insufficient, and the main body portion 6a and the folded portion 6b. It is not possible to effectively relieve and absorb the shearing force acting between the two, and conversely, if it exceeds 100%, the rubber volume will increase significantly, which will easily lead to an increase in tire weight and an increase in manufacturing costs. In addition, heat is easily generated inside the bead portion, which is disadvantageous in terms of durability. It is particularly preferable that the rubber thickness A at the intermediate position KC is 70 to 100%, more preferably 75 to 95% of the maximum width X of the bead core 5.

  e) The rubber thickness B between the main body 6a and the folded portion 6b at the outer end 6be of the folded portion 6b of the carcass ply 6A is 60 to 100% of the rubber thickness A. If the rubber thickness B is less than 60% of the rubber thickness A, the shearing force acting between the body portion 6a and the folded portion 6b of the carcass ply 6A cannot be effectively relaxed and absorbed. On the other hand, if it exceeds 100%, an increase in tire weight and an increase in manufacturing cost are likely to occur. Particularly preferably, the rubber thickness B is 65 to 100%, more preferably 85 to 95% of the rubber thickness A.

  f) The rubber thickness C from the outer end 9ie of the inner ply portion 9i to the tire lumen surface 10 is 22 to 40% of the rubber thickness A. The rubber thickness C is a rubber thickness that forms the shortest distance between the steel cord and the tire lumen surface 10 at the outer end 9ie of the inner ply portion 9i. When the rubber thickness C is less than 22% of the rubber thickness A, the shearing force acting on the outer end 9ie of the inner ply portion 9i cannot be sufficiently relaxed. Conversely, when the rubber thickness C exceeds 40%, It is not preferable because the rubber thickness is excessively increased, and the tire weight and the manufacturing cost are easily increased. Particularly preferably, the rubber thickness C is 25 to 36% of the rubber thickness A, and more preferably 30 to 36%.

  In this embodiment, in order to ensure durability with the rubber thickness C described above, 60-100 parts by weight of halogenated butyl rubber and 0 parts of diene rubber are added to the tire lumen surface 10 out of 100 parts by weight of the rubber polymer. The thing with which the inner liner 14 which consists of a rubber composition containing -40 weight part was distribute | arranged is illustrated. Such a rubber composition is useful for maintaining the air pressure in the tire lumen while maintaining durability as described above.

  g) The rubber thickness t between the inner ply portion 9i and the main body portion 6a of the carcass ply 6A is a range S in which the height h from the bead base line is 69% or more of the outer end height Z of the inner ply portion 9i. (69-100%) is greater than a thickness in the range of less than 69%. Such a distribution of the rubber thickness t increases the ability to relieve the distortion of the outer end 9ie of the inner ply portion 9i, further preventing the looseness and the like and further improving the durability. As shown in FIG. 3 which is a DD cross section of FIG. 2, in the present embodiment, a small thickness of the insulation rubber 11 is disposed between the inner ply portion 9i and the main body portion 6a. Therefore, the rubber thickness t is the sum of the thicknesses of the topping rubber and the insulation rubber 11 of each ply. Further, if the rubber thickness t is too large, the tire weight is increased, and if it is too small, rubber peeling is likely to occur. Therefore, the rubber thickness t is preferably 0.5 to 3.0 mm, more preferably 1.0 to 2.0 mm. It is desirable to do.

  Further, the rubber thickness between the inner ply portion 9i and the main body portion 6a of the carcass ply 6A is larger than 1.0 times and 1.5 times the rubber thickness t outside the range S in the tire radial direction. The following rubber thickness is set. In the present embodiment, in the region outside the range S in the tire radial direction, the rubber thickness gradually increases. As a result, bending and shear stress generated at the outer end 9ie of the inner ply portion 9i can be relaxed and absorbed, and damage at the outer end 9ie can be effectively prevented.

  In the heavy-duty pneumatic tire 1 of the present embodiment, the outer end 9ie of the inner ply portion 9i of the reinforcing ply 9 and the outer end 9oe of the outer ply portion 9o are covered with a ply edge cover rubber 15, respectively. Further, between the packing rubber 12 and the folded portion 6b of the carcass ply 6A, a side packing rubber 16 having a small thickness is disposed at least partially. Inner side wall rubbers 18 and 19 are disposed between the side packing rubber 16 and the hard clinch rubber 17 in contact with the rim. This prevents the outer end 6be of the folded portion 6b and the outer end 9oe of the outer ply portion 9o from coming into direct contact with the clinch rubber 17.

  Since the insulation rubber 11, the ply edge cover rubber 15, the side packing rubber 16, and the inner side wall rubbers 18 and 19 are all provided adjacent to the ply end or the like having low adhesiveness, the rubber material having excellent adhesiveness. It is good to compose from. Specifically, a rubber material containing natural rubber or natural rubber as a main component, for example, an adhesive such as carbon black, silica, a vulcanization aid, a cobalt salt, or a vulcanizing agent such as sulfur or a vulcanization accelerator. Are preferably used, both of which have a complex elastic modulus of 8.0 to 14.0 MPa, more preferably 9.0 to 12.0, and a loss tangent tan δ of 0.085 to 0.150, more preferably 0.100. It is desirable to form with a rubber composition of ~ 0.140.

  A heavy-duty pneumatic radial tire with a five-rib pattern having the basic structure shown in FIG. 1 and a tire size of 315 / 80R22.5 was manufactured, and the bead durability test, tire weight, manufacturing cost, etc. were compared (Example, comparison). Example). All tires have the same structure and the same rubber composition except for the bead portion. As common specifications, the carcass ply and the reinforcement ply both employ steel cords, and the bead core is formed in a hexagonal shape with a horizontally long cross section by winding a steel wire 75 times. The test procedure is as follows.

<Bead durability test>
The test tire was assembled into a rim (size 9.00 × 22.5) compliant with JATMA standard, filled with normal internal pressure, filled with 260% of the normal load, and a drum durability test was performed at a speed of 20 km / h. Evaluation measured the running time until a tire destroyed. The larger the value, the better.

<Tire weight>
The tire weight was measured by the weight per tire and displayed as an index with Example 1 as 100. A smaller number indicates a lighter weight.

<Tire manufacturing cost>
The cost required for one tire was expressed as an index with Example 1 as 100. The smaller the value, the lower the cost.
Table 1 shows the test results.

  As a result of the test, it can be confirmed that the example has improved the bead durability as compared with the comparative example. It can also be confirmed that there is substantially no increase in tire weight, cost, or the like.

It is sectional drawing of the reference | standard state which shows embodiment of this invention. It is an expanded sectional view of the bead part. It is DD sectional drawing of FIG. It is an expanded sectional view of the bead part of the conventional heavy duty pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heavy load pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Carcass ply main part 6b Carcass ply turn part 7 Belt layer 8 Bead apex 9 Reinforcement ply 10 Tire inner surface 11 Insulation rubber 12 Packing rubber 13 Side packing rubber 14 Inner liner

Claims (4)

A carcass composed of a single carcass ply comprising a main body portion straddling a pair of bead cores in a toroidal shape, and a turn-back portion connected to the main body portion and folded around the bead core from the inner side to the outer side in the tire axial direction;
A bead apex extending outward in the tire radial direction from the outer surface of the bead core; an inner ply portion disposed on the inner side in the tire axial direction of the main body portion in the bead portion; and an outer ply portion disposed on the outer side in the tire axial direction of the folded portion; A heavy load characterized by comprising one reinforcing ply having a substantially U-shaped cross section having a joint portion connecting the inner ply portion and the outer ply portion, and satisfying the following requirements a) to g): Heavy duty pneumatic tire.
a) The outer end height Z of the inner ply portion of the reinforcing ply is 18.4 to 29.5% of the tire cross-section height H.
b) The difference (W−Y) between the outer end height W of the folded portion of the carcass ply and the outer end height Y of the outer ply portion of the reinforcing ply is positive and the outer end height Y of the outer ply portion is 7. 0-86.0%
c) The outer end height W of the folded portion of the carcass ply is 56 to 86% of the outer end height Z of the inner ply portion of the reinforcing ply.
d) The rubber thickness A between the main body portion and the turned-up portion is equal to the maximum width X of the bead core at an intermediate position between the maximum width position of the bead core on the outer side in the tire axial direction and the outer end of the turned-up portion of the carcass ply. 63-100%
e) The rubber thickness B between the main body portion and the folded portion at the outer end of the folded portion of the carcass ply is 60 to 100% of the rubber thickness A.
f) The rubber thickness C from the outer end of the inner ply portion to the tire cavity surface is 22 to 40% of the rubber thickness A.
g) The rubber thickness between the inner ply portion and the carcass ply main body portion is less than 69% when the height h from the bead base line is 69% or more of the outer end height Z of the inner ply portion. Greater than range thickness The bead apex has a complex elastic modulus of 10 to 70 MPa and a loss tangent tan δ of 0.120 to 0.220,
And the complex elastic modulus of the packing rubber whose inner end side in the tire radial direction is connected to the bead apex and whose outer end tapers outward in the tire radial direction along the main body portion of the carcass ply is 2.8 to 4.8 MPa. The loss tangent tan δ is 0.050 to 0.120, and the small side packing rubber disposed between the packing rubber and the folded portion and the main body portion and the inner ply portion are disposed. 2. The heavy duty pneumatic tire according to claim 1, wherein the complex elastic modulus of the insulation rubber is 8.0 to 14.0 MPa and the loss tangent tan δ is 0.085 to 0.150.   The heavy duty pneumatic tire according to claim 1 or 2, wherein the carcass is a tubeless type made of a steel cord and attached to a 15 ° deep bottom rim. A rubber composition comprising 60 to 100 parts by weight of a halogenated butyl rubber and 0 to 40 parts by weight of a diene rubber among 100 parts by weight of a rubber polymer is disposed on at least a part of the tire lumen surface. The heavy duty pneumatic tire according to any one of 1 to 3.

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