JP2017056813A - Heavy duty tire - Google Patents

Abstract

It has durability. A heavy-duty tire including a belt layer composed of a plurality of belt plies. The belt layer 7 includes a cross belt ply pair 14 where the belt cord 7c intersects. The cross belt ply pair 14 includes a first region R1 in which a distance between cords, which is a distance between belt cords between belt plies, is constant, and a distance between cords is larger than the distance and substantially constant in distance. And a third region R3 in which the distance between cords is larger than the distance and gradually increases toward the outer side in the tire axial direction. The second region R2 is located inside the shoulder main groove 12 in the tire radial direction. [Selection] Figure 2

Description

  The present invention relates to a heavy duty tire having durability performance.

  The tread portion of the heavy duty tire is provided with a carcass and a belt layer disposed on the outer side of the carcass in the tire radial direction. The belt layer includes a first belt ply in which a belt cord is inclined to one side with respect to a tire circumferential direction, and a belt cord that is overlapped with the first belt ply and inclined in the opposite direction to the first belt ply. A cross belt ply pair including a second belt ply. Such a belt layer exerts a large tagging effect on the tread portion.

  However, since such a cross belt ply pair is subjected to a large shearing force at the outer portion in the tire axial direction where deformation at the time of rolling of the tire is large, a separation that is a peeling damage between the plies on the outer side in the tire axial direction of the belt ply. Could occur.

  In order to suppress such separation, for example, it is conceivable to reduce the shearing force by increasing the thickness of the rubber covering the belt layer as a whole. However, in such a belt layer, the rubber volume increases, and the amount of heat generated by rolling the tire increases, so the topping rubber covering the rubber and belt cord changes in physical properties (thermal degradation), thus suppressing separation. There was a problem that I could not.

JP-A-4-252705

  The present invention has been devised in view of the actual situation as described above, and has as its main purpose to provide a heavy-duty tire having excellent durability performance by suppressing separation on the basis of improving the belt layer. Yes.

  The present invention is a heavy duty tire comprising a belt layer comprising a plurality of belt plies in a tread portion, wherein the belt layer has a belt cord inclined to one side with respect to the tire circumferential direction. A cross belt ply pair comprising a belt ply and a second belt ply overlapped with the first belt ply in a tire radial direction and having a belt cord inclined in a direction opposite to the first belt ply, The cross belt ply pair is adjacent to a first region in which a distance between cords, which is a distance between belt cords between belt plies, is substantially constant at a distance ta, and to the outer side in the tire axial direction of the first region. A second region in which a distance between cords between the belt plies is larger than the distance ta and is substantially constant at the distance tb, and adjacent to the outer side in the tire axial direction of the second region A third region in which a distance between cords between the belt plies is larger than the distance tb and gradually increases toward the outer side in the tire axial direction, and a shoulder main groove extending in the tire circumferential direction is provided in the tread portion, The second region is located on the inner side in the tire radial direction of the shoulder main groove.

  In the heavy duty tire according to the present invention, the belt layer has an outermost belt ply arranged on the outermost side in the tire radial direction, and an outer end of the outermost belt ply in the tire axial direction is the shoulder main groove. It is desirable to be located in the tire axial direction inside.

  In the heavy load tire according to the present invention, the inner end in the tire axial direction of the second region is located on the inner side in the tire axial direction of the inner edge in the tire axial direction of the groove edge on the inner side in the tire axial direction of the shoulder main groove. Is desirable.

  In the heavy duty tire according to the present invention, the maximum inter-cord distance between the belt plies in the second region is 1.5 to 3 times the maximum inter-cord distance between the belt plies in the first region. The maximum inter-cord distance between the belt plies in the third region is preferably 3.5 to 6.5 times the maximum inter-cord distance between the belt plies in the first region.

  In the heavy duty tire according to the present invention, the maximum inter-cord distance between the belt plies in the second region is 1.0 to 2.0 mm, and the maximum inter-cord between the belt plies in the third region The distance is preferably 2.5 to 4.5 mm.

  The heavy duty tire according to the present invention includes a carcass disposed from the tread portion to the bead cores of the bead portions on both sides through the side wall portions on both sides, and disposed on the inner side in the tire radial direction of the belt layer. The innermost belt ply disposed on the innermost side in the tire radial direction, and the inter-cord distance between the carcass cord of the carcass and the belt cord of the innermost belt ply gradually increases toward the outer side in the tire axial direction. desirable.

  In the heavy duty tire according to the present invention, the maximum inter-cord distance between the carcass cord of the carcass and the belt cord of the innermost belt ply is an inner side in the tire radial direction of the first region. It is desirable to be 1.5 to 3.0 times the maximum distance between cords between plies.

In the heavy-duty tire according to the present invention, a second rubber that includes a tire equator and extends on both sides in the tire axial direction is adjacent between the carcass and the innermost belt ply, on the outer side in the tire axial direction of the second rubber. A cushion rubber having a triangular cross section is disposed, and in the second region, a first rubber is disposed between the belt plies, a complex elastic modulus E * 2 of the second rubber, and a complex elastic modulus E * of the cushion rubber. 3 and the complex elastic modulus E * 1 of the first rubber preferably satisfies the following formula (1).
E * 1 ≧ E * 2> E * 3 (1)

  In the heavy duty tire according to the present invention, it is desirable that a tire axial width of the second rubber is 40% or more of a tread contact width.

  The heavy duty tire according to the present invention includes a first belt ply in which a belt cord is inclined to one side with respect to a tire circumferential direction, a first belt ply and a first belt ply that are superimposed in a tire radial direction, and the belt cord is a first belt ply. A belt layer is provided that includes a cross belt ply pair consisting of a second belt ply that is inclined opposite to the belt ply. Such a pair of crossed belt plies exhibits a large tagging effect on the tread portion.

  The cross belt ply pair includes a first region, a second region adjacent to the outer side in the tire axial direction of the first region, and a third region adjacent to the outer side in the tire axial direction of the second region. The first region is a region in which a distance between cords, which is a distance between belt cords between belt plies, is substantially constant at a distance ta. The second region is a region where the cord distance between the belt plies is larger than the distance ta and is substantially constant at the distance tb. The third region is a region in which the cord distance between the belt plies is larger than the distance tb and gradually increases toward the outer side in the tire axial direction. Thereby, the rigidity of the cross belt ply pair increases toward the outer side in the tire axial direction. For this reason, it is possible to effectively suppress the separation of the outer portion in the tire axial direction of the pair of crossed belt plies, in which a particularly large shear force is likely to occur. In addition, the rubber volume in the vicinity of the tire equator of the pair of crossed belt plies that hardly generates a large shearing force can be kept small. For this reason, the separation resulting from the heat generation of the topping rubber of each belt ply is effectively suppressed.

  The second region is located on the inner side in the tire radial direction of the shoulder main groove. That is, the inner side in the tire radial direction of the shoulder main groove on which a large strain acts is supported by the second region having high rigidity. Thereby, since distortion is greatly relieved, separation that tends to occur on the inner side in the tire radial direction of the shoulder main groove is effectively suppressed.

1 is a tire meridian cross-sectional view showing an embodiment of a heavy duty tire of the present invention. It is the elements on larger scale of the tread part of FIG. (A) is a partially enlarged view of the first region, (b) is a partially enlarged view of the second region, and (c) is a partially enlarged view of the third region. It is the elements on larger scale of a carcass ply and the 1st belt ply. It is the elements on larger scale of the tread part of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a meridional section of the right half of a heavy duty tire (hereinafter sometimes simply referred to as “tire”) 1 including a tire rotation axis (not shown). The normal state is a no-load state in which the tire 1 is assembled on the normal rim and filled with the normal internal pressure. FIG. 1 shows the groove width and the like measured in the normal state for convenience. In this specification, unless otherwise specified, dimensions and the like of each part of the tire are indicated by values measured in a normal state. The tire 1 of the present embodiment is suitably used for trucks, buses and the like, for example.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA. For ETRTO, "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, and is “maximum air pressure” for JATMA, and “TIRE” for TRA. The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  In the tread portion 2 of the tire 1 of the present embodiment, a pair of center main grooves 11 that are arranged on both sides of the tire equator C and extend continuously in the tire circumferential direction, and the tire axial direction outside of the center main grooves 11 A pair of shoulder main grooves 12 extending continuously in the circumferential direction are provided.

  The center main groove 11 and the shoulder main groove 12 can extend in various shapes such as a linear shape and a zigzag shape. The groove width Ws of the center main groove 11 and the shoulder main groove 12 is preferably 3% to 9% of the tread ground contact width TW. Further, the tire axial direction distance La between the groove center line 11c of the center main groove 11 and the tire equator C is preferably 5% to 15% of the tread contact width TW. The tire axial direction distance Lb between the groove center line 12c of the shoulder main groove 12 and the tire equator C is preferably 20% to 40% of the tread contact width TW.

  The “tread contact width” TW is the distance between the tread ends Te and Te, which is the contact position on the outermost side in the tire axial direction when a normal load is applied to a tire in a normal state and contacted to a flat surface with a camber angle of 0 degrees. It is determined as the distance in the tire axial direction.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “maximum load capacity”, TRA is “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The tire 1 of the present embodiment includes a carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2. Layer 7.

  In the present embodiment, the carcass 6 is constituted by a single carcass ply 6A. The carcass ply 6 </ b> A includes a main body portion 6 a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 embedded in the bead portion 4, and a folded portion 6 b that continues to the main body portion 6 a and is folded around the bead core 5. It is out. A bead apex 9 is provided between the main body 6a and the turn-up portion 6b. The bead apex 9 extends from the bead core 5 to the outer side in the tire radial direction.

  The carcass ply 6A includes, for example, steel carcass cords 6c that are inclined and arranged at an angle of 80 to 90 degrees with respect to the tire circumferential direction, and a topping rubber 6t that covers an array of the carcass cords 6c (shown in FIG. 4). ). The topping rubber 6t of the carcass ply 6A preferably has a complex elastic modulus E * a of, for example, 5.5 to 9.0 MPa. Such a topping rubber 6t can maintain high adhesion to the carcass cord 6c while increasing the rigidity of the tread portion 2.

In the present specification, “complex elastic modulus E *” is a value measured using a “viscoelastic spectrometer” manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions shown below in accordance with the provisions of JIS-K6394. .
Initial strain: 10%
Amplitude: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  The belt layer 7 is composed of, for example, a plurality of belt plies in which an array of steel belt cords 7c is covered with a topping rubber 7t (shown in FIG. 3). In the present embodiment, the belt layers 7 overlap each other in the tire radial direction. It is composed of four first to fourth belt plies 7A to 7D. The belt cords 7c of the first to fourth belt plies 7A to 7D are arranged and inclined at an angle of, for example, 10 to 70 ° with respect to the tire circumferential direction.

  It is desirable that the topping rubber 7t of each belt ply 7A to 7D has a complex elastic modulus E * b of, for example, 6.2 to 10.2 MPa. When the complex elastic modulus E * b of the topping rubber 7t is less than 6.2 MPa, the rigidity of the tread portion 2 may be reduced. When the complex elastic modulus E * b of the topping rubber 7t exceeds 10.2 MPa, the rigidity of the belt layer 7 is excessively increased, and the durability may be deteriorated by breaking other rubber members.

  In the present embodiment, the belt cord of the second belt ply 7B is inclined to one side with respect to the tire circumferential direction. Further, the belt cord of the third belt ply 7C is inclined in the opposite direction to the belt cord of the second belt ply 7B. Thus, the second belt ply 7B and the third belt ply 7C form a cross belt ply pair 14 where the belt cords intersect. Such a cross belt ply pair 14 exerts a great reinforcing effect (tag effect) because the belt cords restrain each other. Note that the cross belt ply pair 14 is not limited to the one formed by the second and third belt plies 7B and 7C. For example, the first and second belt plies 7A and 7B are used. Other belt plies may be used.

  As shown in FIG. 2, the cross belt ply pair 14 includes a first region R1 extending on both sides in the tire axial direction including the tire equator C, and a second region adjacent to the outer side in the tire axial direction of the first region R1. R2 and 3rd area | region R3 adjacent to the tire axial direction outer side of 2nd area | region R2 are included. FIG. 3A is an enlarged view of the first region R1. In the first region R1, the inter-cord distance, which is the distance between the belt cords between the belt plies 7B and 7C, is substantially constant at the distance ta. FIG. 3B is an enlarged view of the second region R2. In the second region R2, the distance between cords between the belt plies 7B and 7C is larger than the distance between cords in the first region R1, and is substantially constant at the distance tb. FIG. 3C is an enlarged view of the third region R3. In the third region R3, the distance between cords between the belt plies 7B and 7C has a distance tc larger than the distance between cords in the second region R2, and gradually increases toward the outer side in the tire axial direction. Thus, the cross belt ply pair 14 has a distance between cords that increases toward the outer side in the tire axial direction, so that the rigidity of the tread portion 2 increases toward the outer side in the tire axial direction and the rubber volume on the tire equator C side. Can be reduced. Thereby, since the separation between the belt plies is suppressed, the durability performance is greatly improved. The “inter-code distance is substantially constant with distance” means a distance in which the difference between the minimum value and the maximum value of the inter-code distance does not exceed 50% of the minimum value in each of the regions R1 and R2.

  The maximum inter-code distance in the second region R2 (hereinafter sometimes simply referred to as “second inter-code distance t2”) is the maximum inter-code distance in the first region R1 (hereinafter simply referred to as “first inter-code distance t1”). It may be 1.5 to 3 times as large as "." The maximum inter-code distance in the third region R3 (hereinafter sometimes simply referred to as “third inter-code distance t3”) is 3.5 to 6.5 times the first inter-code distance t1. desirable. Thereby, while increasing the rigidity of the tread portion 2 in a more balanced manner along the tire axial direction and suppressing an increase in the rubber volume and suppressing excessive heat generation, the durability performance is further improved.

  In order to effectively exhibit the above-described operation, the second inter-cord distance t2 is preferably 1.0 to 2.0 mm. The third inter-cord distance t3 is preferably 2.5 to 4.5 mm. Furthermore, it is desirable that the first inter-cord distance t1 is 0.3 to 1.3 mm.

  The tire axial direction width W1 of the first region R1 is preferably 35% to 550% of the tread contact width TW. The tire axial direction width W2 of the second region R2 is preferably 8% to 16% of the tread contact width TW. The tire axial direction width W3 of the third region R3 is preferably 10% to 16% of the tread contact width TW. Thereby, since the shear force of a magnitude | size different in a tire axial direction can be relieved with sufficient balance, the separation between belt plies is further suppressed.

  In the present embodiment, the first rubber 15 is disposed between the belt plies 7B and 7C in the second region R2 and the third region R3. The complex elastic modulus E * 1 of the first rubber 15 is preferably 6.2 to 10.2 MPa. Thereby, since the rigidity of 2nd area | region R2 and 3rd area | region R3 can be improved more effectively, a separation is suppressed.

  The first rubber 15 includes a first portion 15a disposed between the belt plies 7B and 7C in the second region R2, a second portion 15b disposed between the belt plies 7B and 7C in the third region R3, and a second portion. It includes a third portion 15c arranged on the outer side in the tire axial direction than the portion 15b. The first portion 15a has a substantially constant thickness d1 (shown in FIG. 3A). The second portion 15b has a thickness d2 (shown in FIG. 3B) that gradually increases outward in the tire axial direction. The third portion 15c has a thickness d3 that is the same as the maximum value of the thickness d2 of the second portion 15b, and is substantially constant. The third portion 15c extends to the vicinity of the outer end 7i in the tire axial direction of the second belt ply 7B. “Substantially constant” refers to a thickness in which the difference between the minimum value and the maximum value does not exceed 50% of the minimum value.

  The second region R2 is located inside the shoulder main groove 12 in the tire radial direction. Thereby, since the rigidity of the cross belt ply pair 14 at the position in the tire radial direction of the shoulder main groove 12 in which a large strain occurs is reliably increased, the strain can be effectively reduced and the separation can be greatly suppressed. Therefore, the tire 1 of the present embodiment has excellent durability performance.

  The inner end 20 in the tire axial direction of the second region R2 is located on the inner side in the tire axial direction from the inner end 12i in the tire axial direction of the groove edge 12a on the inner side in the tire axial direction of the shoulder main groove 12. As a result, the shoulder main groove 12 can be supported by the second region R2 over the tire axial direction, so that the strain is alleviated more effectively. In order to exhibit such an action more effectively, the outer end 21 in the tire axial direction of the second region R2 is a tire axis than the outer end 12e in the tire axial direction of the groove edge 12b on the outer side in the tire axial direction of the shoulder main groove 12. It is desirable to be located outside the direction.

  The fourth belt ply 7D has an outer end 7b in the tire axial direction located on the inner side in the tire axial direction than the shoulder main groove 12. That is, the tire axial direction width of the fourth belt ply 7D is made smaller than those of the first to third belt plies 7A to 7C, thereby suppressing an excessive increase in rigidity of the belt layer 7. Thus, in the tire 1 of the present embodiment, the second region R2 is arranged on the inner side in the tire radial direction of the shoulder main groove 12, and the outer end 7b of the fourth belt ply 7D is disposed on the tire shaft more than the shoulder main groove 12. It is located inside the direction. Thereby, the rigidity between the belt plies at the groove bottom portion of the shoulder main groove 12 is improved in a well-balanced manner. From this point of view, the outer end 7b of the fourth belt ply 7D is the outer end 11e in the tire axial direction of the inner edge 20 in the tire axial direction of the second region R2 and the groove edge 11b on the outer side in the tire axial direction of the center main groove 11. It is desirable to be located between.

  In the present embodiment, the first belt ply 7A and the carcass ply 6A include the fourth region R4 including the tire equator C and extending on both sides in the tire axial direction, and the fifth region R4 adjacent to the outer side in the tire axial direction of the fourth region R4. Region R5 is formed. In the fourth region R4 of the present embodiment, the distance between the cords of the belt cord 7c of the first belt ply 7A and the carcass cord 6c of the carcass ply 6A is substantially constant at a distance td (shown in FIG. 4). Yes. The fifth region R5 of the present embodiment includes a portion where the distance between cords is larger than the distance td (not shown) and gradually increases toward the outer side in the tire axial direction. Such a fifth region R5 maintains the stable rolling of the tire 1 while increasing the rigidity of the outer portion in the tire axial direction of the tread portion 2 and suppressing the separation between the first belt ply 7A and the carcass ply 6A. . “Substantially constant” means that the difference between the minimum value and the maximum value of the inter-cord distance between the belt cord 7c of the first belt ply 7A and the carcass cord 6c of the carcass ply 6A exceeds 50% of the minimum value. Say no distance.

  FIG. 4 is an enlarged view of the carcass 6 and the first belt ply 7A on the inner side (fourth region R4) in the tire radial direction of the first region R1. The maximum cord distance t4 between the carcass cord 6c and the belt cord 7c of the first belt ply 7A on the inner side in the tire radial direction of the first region R1 is preferably 1.5 to 3 times the first cord distance t1. It is desirable that Thereby, when the load is not large, in the first region R1 where a high contact pressure acts, the sudden carcass ply 6A and the first belt ply 7A due to thermal deterioration and oxygen deterioration of the topping rubbers 6t and 7t Separation can be suppressed.

  As shown in FIG. 2, between the carcass ply 6A and the first belt ply 7A, a second rubber 16 that includes the tire equator C and extends outward in the tire axial direction, and an outer side in the tire axial direction of the second rubber 16 And a cushion rubber 17 having a triangular cross section adjacent to each other. In the present embodiment, the second rubber 16 is disposed in the fourth region R4, and the cushion rubber 17 is disposed in the fifth region R5. The outer end 16e of the second rubber 16 in the tire axial direction is in contact with the inner end 17i of the cushion rubber 17 in the tire axial direction.

  Since the second rubber 16 is provided in a region where the distance between the cords is substantially constant, the shearing force due to the cord angle difference between the first belt ply 7A and the carcass ply 6A is reduced. .

  The cushion rubber 17 has a maximum thickness d5 at the outer end 7i in the tire axial direction of the second belt ply 7B, and along the outer surface of the carcass 6 while gradually decreasing the thickness from the outer end 7i to the outer side in the tire axial direction. It is arranged inside and outside the tire axial direction. Such a cushion rubber 17 can effectively suppress damage due to contact of the first belt ply 7A with the carcass ply 6A.

It is desirable that the complex elastic modulus E * 1 of the first rubber 15, the complex elastic modulus E * 2 of the second rubber 16, and the complex elastic modulus E * 3 of the cushion rubber 17 satisfy the following formula (1). .
E * 1 ≧ E * 2> E * 3 (1)
That is, the complex elastic modulus E * 2 of the second rubber 16 is equal to or less than the complex elastic modulus E * 1 of the first rubber 15, and the complex elastic modulus E * 3 of the cushion rubber 17 is the complex elastic modulus of the second rubber 16. It is smaller than E * 2. Thereby, since the excessive increase in the rigidity of the tread part 2 and a rigidity level | step difference are suppressed, the rubber | gum fracture of the topping rubbers 6t and 7t and the tread rubber 2G of a tread part can be suppressed, suppressing a separation.

  From such a viewpoint, it is desirable that the complex elastic modulus E * 2 of the second rubber 16 is, for example, 6.2 to 10.2 MPa. Further, the complex elastic modulus E * 3 of the cushion rubber 17 is preferably 2.8 to 4.8 MPa, for example.

  The tire rubber axial width W4 of the second rubber 16 is preferably 40% or more of the tread contact width TW. Thereby, sudden separation of the carcass ply 6A and the first belt ply 7A in the vicinity of the tire equator C is effectively suppressed. When the tire axial direction width W4 of the second rubber 16 is excessively large, the rubber volume of the cushion rubber 17 becomes small, and the rigidity of the outer portion in the tire axial direction of the tread portion 2 becomes excessively high. There is. For this reason, it is desirable that the tire axial direction width W4 of the second rubber 16 is 70% or less of the tread ground contact width TW.

  As mentioned above, although embodiment of this invention was explained in full detail, it cannot be overemphasized that this invention is not limited to illustrated embodiment, and can be deform | transformed and implemented in a various aspect.

A heavy-duty tire of size 12R22.5 having the basic structure of FIG. 1 was prototyped based on the specifications in Table 1, and the durability performance of each sample tire was tested. The main common specifications and test methods for each sample tire are as follows.
Complex elastic modulus E * a of carcass ply topping rubber: 7.3 MPa
Complex elastic modulus E * b of belt ply topping rubber: 8.2 MPa
Complex elastic modulus of the first rubber E * 1: 8.2 MPa
Complex elastic modulus of the second rubber E * 2: 8.2 MPa
Complex elastic modulus of cushion rubber E * 3: 3.8 MPa
Position of the groove center line 12c of the shoulder main groove from the tire equator (Lb / TW): 25 to 40%
First region tire axial width (W1 / TW): 40%
Width in the tire axial direction of the second region (W2 / TW): 12%
Width in the axial direction of the third region (W3 / TW): 13%
Tire axial width of the fourth region (second rubber) (W4 / TW): 52%

<Durability>
Using a drum testing machine having a drum diameter of 1.7 m, each sample tire was run under the following conditions, and the running time until the tire was damaged due to separation was measured. The result is an index with the running time of Comparative Example 1 as 100, and the larger the value, the better the durability performance. The upper limit of the travel time is 2.3 times the travel time of Comparative Example 1. Each sample tire used was a rim assembled, filled with air of 80 to 85% by mass of oxygen at a normal internal pressure, and put into an oven at 60 ° C. for 6 weeks.
Load: Maximum load capacity x 140%
Internal pressure: 1000kPa
Speed: 80km / h
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the durability of the tire of the example was improved as compared with the comparative example. Moreover, although the tire which changed the complex elastic modulus and tire axial direction width | variety of the 1st rubber | gum, the 2nd rubber | gum, and the cushion rubber in the preferable range was tested, the same tendency as the result of this test was seen.

DESCRIPTION OF SYMBOLS 1 Heavy duty tire 7 Belt layer 7c Belt cord 12 Shoulder main groove 14 Cross belt ply pair R1 1st area | region R2 2nd area | region R3 3rd area | region

Claims (9)

In the tread portion, a heavy duty tire having a belt layer composed of a plurality of belt plies,
The belt layer includes a first belt ply in which a belt cord is inclined on one side with respect to a tire circumferential direction, and the belt cord is overlapped with the first belt ply in a tire radial direction, and the belt cord is the first belt ply. A cross belt ply pair consisting of a second belt ply that is inclined opposite to the ply;
The cross belt ply pair is adjacent to a first region in which a distance between cords, which is a distance between belt cords between belt plies, is substantially constant at a distance ta, and to the outer side in the tire axial direction of the first region. A second region in which a distance between cords between the belt plies is larger than the distance ta and is substantially constant at a distance tb; and a cord between the belt plies adjacent to the outer side in the tire axial direction of the second region. A third region having an inter-distance larger than the distance tb and gradually increasing toward the outside in the tire axial direction,
The tread portion is provided with a shoulder main groove extending in the tire circumferential direction,
The heavy duty tire, wherein the second region is located inside the shoulder main groove in the tire radial direction. The belt layer has an outermost belt ply disposed on the outermost side in the tire radial direction,
2. The heavy duty tire according to claim 1, wherein an outer end of the outermost belt ply in the tire axial direction is located on an inner side in the tire axial direction of the shoulder main groove.   3. The heavy load according to claim 1, wherein an inner end in the tire axial direction of the second region is located on an inner side in the tire axial direction with respect to an inner end in the tire axial direction of a groove edge on the inner side in the tire axial direction of the shoulder main groove. Heavy tire.   The maximum cord distance between the belt plies in the second region is 1.5 to 3 times the maximum cord distance between the belt plies in the first region, and the belt ply in the third region. The heavy load tire according to any one of claims 1 to 3, wherein a maximum inter-cord distance is 3.5 to 6.5 times a maximum inter-cord distance between the belt plies in the first region.   The maximum cord distance between the belt plies in the second region is 1.0 to 2.0 mm, and the maximum cord distance between the belt plies in the third region is 2.5 to 4.4. The heavy-duty tire according to any one of claims 1 to 4, wherein the tire is 5 mm. From the tread part to the side wall parts on both sides to the bead cores on both side bead parts, including a carcass arranged on the inner side in the tire radial direction of the belt layer,
The belt layer includes an innermost belt ply arranged on the innermost side in the tire radial direction,
The heavy duty tire according to any one of claims 1 to 5, wherein a distance between cords of the carcass cord of the carcass and a belt cord of the innermost belt ply gradually increases toward the outer side in the tire axial direction.   The maximum inter-cord distance between the carcass cord of the carcass and the belt cord of the innermost belt ply on the inner side in the tire radial direction of the first region is the maximum inter-cord distance between the belt plies of the first region. The heavy-duty tire according to claim 6, wherein the tire is 1.5 to 3.0 times. Between the carcass and the innermost belt ply, a second rubber including the tire equator and extending on both sides in the tire axial direction and a cushion rubber having a triangular cross section adjacent to the outer side in the tire axial direction of the second rubber are arranged. And
The second region has a first rubber disposed between the belt plies,
The complex elastic modulus E * 2 of the second rubber, the complex elastic modulus E * 3 of the cushion rubber, and the complex elastic modulus E * 1 of the first rubber satisfy the following formula (1). Or the heavy duty tire according to 7.
E * 1 ≧ E * 2> E * 3 (1)   The heavy duty tire according to claim 8, wherein a tire axial width of the second rubber is 40% or more of a tread contact width.

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