Tire for heavy load

Abstract

To provide a tire for a heavy load, which is configured so that sufficient fracture strength is imparted on a belt reinforcement layer to suppress a belt layer from being damaged due to an obstacle on a road.SOLUTION: A tire for a heavy load according to the present invention comprises, at a tread part, a belt made of one or more belt layers, and one or more belt reinforcement layers arranged outside in a tire radial direction of the belt. In the belt reinforcement layer, reinforcement cords are coated with rubber. Each of the reinforcement cords extends from one end to the other end of the belt reinforcement layer, and is cut at the one end and the other end. Each of the reinforcement cords is further divided at one or more positions between the one end and the other end. The cord driving count of the reinforcement cord is larger than the cord driving count of a belt cord of the belt.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heavy-duty tire.

Background Art

[0002] In a heavy-duty tire, a configuration is known in which a belt reinforcing layer is provided on the outer side in the tire radial direction of a belt layer in order to protect a belt layer having a hoop function from obstacles such as road debris and stones (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even when a belt reinforcing layer is provided, the belt layer may be damaged due to breakage of the belt reinforcing layer by an obstacle.

[0005] Therefore, an object of the present invention is to provide a heavy-duty tire capable of suppressing damage to the belt layer caused by road obstacles by giving sufficient breaking strength to the belt reinforcing layer.

Means for Solving the Problems

[0006] The gist configuration of the present invention is as follows. (1) A heavy-duty tire including a belt composed of one or more belt layers in a tread portion and one or more belt reinforcing layers disposed on the outer side in the tire radial direction of the belt, wherein the belt reinforcing layer has reinforcing cords rubber-coated, each of the reinforcing cords extends from one end to the other end of the belt reinforcing layer and is cut at the one end and the other end, Each of the reinforcing cords is further divided at one or more locations between the one end and the other end. A heavy-duty tire, characterized in that the number of driven reinforcing cords is larger than the number of driven belt cords of the belt.

[0007] (2) In a cross-sectional view in the tire width direction, The sum of the cross-sectional areas of the plurality of reinforcing cords with respect to the cross-sectional area of the belt reinforcing layer is equal to or greater than the sum of the cross-sectional areas of the plurality of belt cords of the outermost belt layer located outermost in the tire radial direction among the one or more belt layers. The heavy-duty tire according to (1).

[0008] (3) Each of the divided reinforcing cords has a width in the tire width direction of 6.25 to 50% of the width in the tire width direction of the belt reinforcing layer. The heavy-duty tire according to (1) or (2).

[0009] (4) Each of the divided reinforcing cords is in a state where at least a part of the divided surfaces is in contact with each other. The heavy-duty tire according to any one of (1) to (3).

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a heavy-duty tire capable of suppressing damage to the belt layer caused by road obstacles by giving sufficient breaking strength to the belt reinforcing layer.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be exemplified and described in detail with reference to the drawings.

[0013] Hereinafter, unless otherwise specified, dimensions and positional relationships refer to those in the reference state where a heavy-duty tire (hereinafter also simply referred to as "tire") is mounted on an application rim, filled with a specified internal pressure, and unloaded.

[0014] In this specification, the "application rim" is an industrial standard effective in the region where the tire is produced and used. In Japan, it is the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Association). In Europe, it is the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation). In the United States, it is the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) or the like that is described or will be described in the future, and refers to the standard rim in the applicable sizes (Measuring Rim in the STANDARDS MANUAL of ETRTO, Design Rim in the YEAR BOOK of TRA). (That is, the "rim" of the above "wheel" includes future industrial standards in addition to the current sizes.) BOOK, in Europe it is the ETRTO (The European Tyre and Ri m Technical Organisation)'s STANDARDS MANU AL, in the United States it is the TRA (The Tire and Rim Association, Inc.)'s YEAR BOOK, etc. described or to be described in the future, the applicable s izes of the standard rim (Measuring Rim in the ETRTO's STANDARDS MANUAL, Design Rim in the TRA's YEAR BOOK) (i.e ch, the "rim" of the above "wheel" includes future industrial standards in addition to the current sizes ​ including sizes that may be rare. Examples of "sizes described in the future" include ETRTO 20 described as "FUTURE DEVELOPMENTS" in the 2013 edition sizes. ). However, in the case of sizes not described in the above industrial standards, the rim refers to a rim with a width corresponding to the bead width of the tire . Also, the "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating described in the above JATMA, etc. In the case of sizes not described in the above industrial standards, the "specified internal pressure" shall refer to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted . Also, the "maximum load weight" described later shall refer to the load corresponding to the above maximum load capacity .

[0015] FIG. 1 is a cross-sectional view of the tire in the tire width direction showing the tread portion of the tire. This tire includes a pair of bead portions, a pair of sidewall portions continuous with the pair of bead portions, and a tread portion 1 continuous between the sidewall portions. Further, this tire further includes a carcass that extends toroidally between the pair of bead portions. Since the configurations of the bead portion and the carcass can be known configurations, detailed descriptions thereof are omitted

[0016] As shown in FIG. 1, the tread portion 1 includes a belt 2 composed of one or more belt layers (in the illustrated example, three belt layers 2a, 2b, 2c) and one or more (in the illustrated example, one layer) belt reinforcing layers 3 disposed on the outer side in the tire radial direction of the belt 2

[0017] ​Each of the belt layers 2a, 2b, and 2c has a belt cord rubber-coated. In this example, the belt layers 2a, 2b, and 2c are inclined belt layers where the belt cords cross each other between the layers. Each belt cord can be inclined at an inclination angle of, for example, 5 to 60° with respect to the tire circumferential direction, although not particularly limited. In the illustrated example, the width of the belt layer 2b in the tire width direction is the largest. On the other hand, the number of belt layers may be one or more, and the number of belt layers and the width of the belt layers in the tire width direction can be various. The belt cord is not particularly limited, but a steel cord can be used.

[0018] The belt reinforcing layer 3 has a reinforcing cord rubber-coated. Also, each of the reinforcing cords extends from one end to the other end of the belt reinforcing layer 3 and is cut at one end and the other end. That is, the reinforcing cord extends inclined with respect to the tire circumferential direction. The inclination angle of the reinforcing cord with respect to the tire circumferential direction is not particularly limited, but can be, for example, 5 to 60°. The reinforcing cord is not particularly limited, but it is preferable to use a cord of a material having sufficient breaking strength, and for example, a steel cord or an organic fiber such as nylon or aramid can be used.

[0019] FIG. 2 is a plan view of the belt reinforcing layer. As shown in FIGS. 1 and 2, each of the reinforcing cords is further divided at one or more locations between one end and the other end (in FIG. 1, the ones indicated by circles are the reinforcing cords at the non-divided locations, and the ones indicated by circles with vertical lines are the reinforcing cords at the divided locations). In this example, each of the divided reinforcing cords is in a state where at least a part of the divided surfaces is in contact.

[0020] Here, the number of the driven-in reinforcing cords 3 is larger than the number of the driven-in belt cords of the belt 2. Hereinafter, the operation and effect of the heavy load tire of the present embodiment will be described.

[0021] In the heavy load tire of the present embodiment, the belt reinforcing layer 3 is disposed on the outer side in the tire radial direction of the belt 2, and the belt reinforcing layer 3 functions as a protection for the belt 2. Here, FIG. 3A is a view showing a state in which the fiber 5 is laid on the rubber block 4 and the protrusion 6 is pushed in from above. FIG. 3B is a view showing the state of deformation of the rubber block 6 when the fiber 5 is laid on the rubber block 4 and the protrusion 6 is pushed in from above. Further, FIG. 4 is a view showing the relationship between the fiber length at that time and the tensile force of the fiber directly under the protrusion.

[0022] The tensile force generated in the reinforcing cord, which causes the breakage of the reinforcing cord, is the sum of the shearing forces of the rubber generated along the reinforcing cord (schematically shown by small squares in FIG. 3B for shear deformation). As shown in FIG. 4, when the fiber is shortened, the sum of the shearing forces of the rubber generated along the fiber can be reduced. In the present embodiment, since each of the reinforcing cords is further divided at one or more locations between one end and the other end, the sum of the shearing forces of the rubber generated along the reinforcing cord can be reduced, and the reinforcing cord can be made difficult to break. As a result, the belt reinforcing layer 3 is made difficult to break, so that the protection function of the belt reinforcing layer 3 for the belt 2 (for example, from obstacles such as falling objects and stones) can be sufficiently exerted. Further, since the number of driving of the reinforcing cord 3 is larger than the number of driving of the belt cord of the belt 2, the protection function of the belt reinforcing layer 3 for the belt 2 can be made more sufficient. As described above, according to the heavy load tire of the present embodiment, by providing the belt reinforcing layer with sufficient breaking strength, damage to the belt layer due to road obstacles can be suppressed.

[0023] Here, in a cross-section view in the tire width direction, the sum of the cross-sectional areas of the plurality of reinforcing cords with respect to the cross-sectional area of the belt reinforcing layer (the sum of the cross-sectional area of the reinforcing cords and the cross-sectional area of the covering rubber) is preferably not less than the sum of the cross-sectional areas of the plurality of belt cords of the outermost belt layer (belt layer 2c in the illustrated example) located outermost in the tire radial direction among one or more belt layers with respect to the cross-sectional area of the outermost belt layer (the sum of the cross-sectional area of the belt cords and the cross-sectional area of the covering rubber). This is because the belt reinforcing layer 3 can be provided with a more sufficient protective function against the belt 2.

[0024] Each of the divided reinforcing cords preferably has a width in the tire width direction of 6.25 to 50% of the width in the tire width direction of the belt reinforcing layer 3. By setting it to 50% or less, the effect of improving the breaking strength of the reinforcing cords can be made more sufficient. On the other hand, by setting it to 6.25% or more, it is possible to prevent the reinforcing cords from being too short and instead losing the protective function due to the reinforcing cords being pulled out, and to suppress a decrease in productivity during manufacturing.

[0025] Each of the divided reinforcing cords is preferably in a state where at least a part of the dividing surfaces are in contact with each other (in the example shown in FIG. 2, at all dividing surfaces, at least a part (the entire surface in the illustrated example) of the dividing surfaces are in contact). This is because obstacles can be prevented from penetrating the voids that occur when the cut ends are separated from each other. FIG. 5 is a plan view of a first modified example of the belt reinforcing layer. As shown in FIG. 5, the divided reinforcing cords may have the dividing surfaces separated from each other. FIG. 6 is a plan view of a second modified example of the belt reinforcing layer. As shown in FIG. 6, the divided reinforcing cords may be a mixture of those in a state where at least a part of the dividing surfaces are in contact with each other and those in a state where the dividing surfaces are separated from each other. Note that the state where at least a part of the dividing surfaces are in contact with each other includes a state where they are in contact with each other by overlapping in the radial direction and a state where they are in contact with each other by overlapping in the circumferential direction.

[0026] Here, the width of the belt reinforcing layer 3 in the tire width direction is preferably 30% or more of the tread width. Also, the ends of the belt reinforcing layer 3 are preferably located on the inner side in the tire width direction than the tread ends. By setting the width of the belt reinforcing layer 3 in the tire width direction to 30% or more of the tread width, the width direction range in which the belt reinforcing layer protects the belt can be widened, and the protection function can be enhanced. Also, by positioning the ends of the belt reinforcing layer 3 on the inner side in the tire width direction than the tread ends, an increase in the weight of the belt reinforcing layer (and thus an increase in the weight of the tire) can be suppressed. Here, the "tread end" refers to both ends in the tire width direction of the tread surface of the tread portion that will come into contact with the road surface when the tire is mounted on the application rim, filled with the specified internal pressure, and loaded with the maximum load. Also, the "tread width" refers to the distance in the tire width direction between both tread ends in the unloaded state.

[0027] Also, the split positions of the respective reinforcing cords preferably have a shift in the tire width direction from the circumferential main grooves. This is because when the grooves are formed by the mold part during the vulcanization molding of the green tire, pressure is applied to the reinforcing cords, suppressing the movement of the cut end positions and enabling the protection function for the belt to be more reliably exerted. The method of splitting the reinforcing cords is not particularly limited, but as an example, the belt before the tire vulcanization molding can be made into a plurality of narrower widths.

[0028] [Arrangement Example of Communication Device] FIG. 8 is a diagram showing an example of the arrangement of communication devices. The tire may be provided with an RF tag as the communication device 100. The RF tag includes an IC chip and an antenna. The RF tag may be arranged, for example, sandwiched between a plurality of members of the same or different types constituting the tire. By doing so, it is easy to attach the RF tag during tire production, and the productivity of the tire provided with the RF tag can be improved. In this example, the RF tag may be arranged, for example, sandwiched between a bead filler and another member adjacent to the bead filler. The RF tag may be embedded in any member constituting the tire. By doing so, the load applied to the RF tag can be reduced as compared with the case where it is arranged sandwiched between a plurality of members constituting the tire. Thereby, the durability of the RF tag can be improved. In this example, the RF tag may be embedded in a rubber member such as tread rubber or side rubber, for example. The RF tag is preferably not arranged at a position that becomes the boundary between members having different rigidities in the peripheral length direction, which is the direction along the outer surface of the tire in a cross-sectional view in the tire width direction. By doing so, the RF tag is not arranged at a position where distortion is likely to concentrate due to the rigidity step. Therefore, the load applied to the RF tag can be reduced. Thereby, the durability of the RF tag can be improved. In this example, the RF tag is preferably not arranged, for example, at a position that becomes the boundary between the end of the carcass and a member (such as side rubber) adjacent to the end of the carcass in a cross-sectional view in the tire width direction. The number of RF tags is not particularly limited. The tire may be provided with only one RF tag or may be provided with two or more RF tags. Here, as an example of the communication device, an RF tag is illustrated and described, but a communication device different from the RF tag may also be used.

[0029] The RF tag may be disposed, for example, in the tread portion of the tire. By doing so, the RF tag will not be damaged by a side cut of the tire. The RF tag may be disposed, for example, at the center of the tread in the tire width direction. The center of the tread is a position where deflection is less likely to concentrate in the tread portion. By doing so, the load applied to the RF tag can be reduced. Thereby, the durability of the RF tag can be improved. Also, it is possible to suppress a difference in communication performance with the RF tag from both outer sides of the tire in the tire width direction. In this example, the RF tag may be disposed, for example, within a range of 1 / 2 of the tread width centered on the tire equatorial plane in the tire width direction. The RF tag may be disposed, for example, at the tread end in the tire width direction. When the position of the reader that communicates with the RF tag is predetermined, the RF tag may be disposed, for example, at the tread end on one side closer to this reader. In this example, the RF tag may be disposed, for example, within a range of 1 / 4 of the tread width with the tread end as the outer end in the tire width direction.

[0030] The RF tag may be disposed on the inner cavity side of the tire, for example, from a carcass including one or more carcass plies straddling between bead portions. By doing so, it becomes difficult for the RF tag to be damaged against impacts applied from the outside of the tire and damages such as side cuts and punctures. As an example, the RF tag may be disposed in close contact with the surface on the inner cavity side of the carcass. As another example, when there is another member on the inner cavity side of the tire from the carcass, the RF tag may be disposed, for example, between the carcass and another member located on the inner cavity side of the tire from this carcass. Examples of another member located on the inner cavity side of the tire from the carcass include, for example, an inner liner forming the inner surface of the tire. As another example, the RF tag may be attached to the inner surface of the tire facing the inner cavity of the tire. By configuring the RF tag to be attached to the inner surface of the tire, it becomes easy to attach the RF tag to the tire and to inspect and replace the RF tag. That is, the attachability and maintainability of the RF tag can be improved. Further, by attaching the RF tag to the inner surface of the tire, it is possible to prevent the RF tag from becoming the core of tire failure as compared with a configuration in which the RF tag is embedded in the tire. Further, when the carcass includes a plurality of carcass plies and there is a position where the plurality of carcass plies are overlapped, the RF tag may be disposed between the overlapped carcass plies.

[0031] The RF tag may be disposed, for example, on the tread portion of the tire, radially outside of a belt including one or more belt plies. As an example, the RF tag may be disposed in close contact with the belt, radially outside of the belt in the tire radial direction. Further, it may be disposed in close contact with the belt layer, radially outside of the belt reinforcing layer in the tire radial direction. As another example, the RF tag may be embedded in the tread rubber, radially outside of the belt reinforcing layer. By disposing the RF tag on the tread portion of the tire, radially outside of the belt, communication with the RF tag from the outside of the tire in the tire radial direction is less likely to be inhibited by the belt. Therefore, the communication performance with the RF tag from the outside of the tire in the tire radial direction can be improved. Further, the RF tag may be disposed, for example, on the tread portion of the tire, radially inside of the belt. By doing so, since the outside of the RF tag in the tire radial direction is covered by the belt, the RF tag is less likely to be damaged by impacts from the tread surface or punctures. As an example of this, the RF tag may be disposed between the belt and the carcass located radially inside of the belt in the tread portion of the tire. Further, when the belt includes a plurality of belt plies, the RF tag may be disposed between any two belt plies in the tread portion of the tire. By doing so, since the outside of the RF tag in the tire radial direction is covered by one or more belt plies, the RF tag is less likely to be damaged by impacts from the tread surface or punctures.

[0032] The RF tag may be disposed, for example, sandwiched between the cushion rubber and the tread rubber or between the cushion rubber and the side rubber. By doing so, the impact on the RF tag can be mitigated by the cushion rubber. Therefore, the durability of the RF tag can be improved. Further, the RF tag may be embedded in the cushion rubber, for example. Furthermore, the cushion rubber may be composed of a plurality of adjacent rubber members of the same or different types. In such a case, the RF tag may be disposed sandwiched between the plurality of rubber members constituting the cushion rubber.

[0033] The RF tag may be disposed, for example, at the position of the sidewall portion or the bead portion of the tire. The RF tag may be disposed, for example, at the sidewall portion or the bead portion on one side closer to the reader capable of communicating with the RF tag. By doing so, the communication performance between the RF tag and the reader can be enhanced. As an example, the RF tag may be disposed between the carcass and the side rubber, or between the tread rubber and the side rubber. The RF tag may be disposed, for example, in the tire radial direction between the position where the tire has its maximum width and the position of the tread surface. By doing so, compared with the configuration in which the RF tag is disposed inside the tire in the tire radial direction from the position where the tire has its maximum width, the communication performance between the RF tag and the outside of the tire in the tire radial direction can be enhanced. The RF tag may be disposed, for example, inside the tire in the tire radial direction from the position where the tire has its maximum width. By doing so, the RF tag is disposed in the vicinity of the bead portion with high rigidity. Therefore, the load applied to the RF tag can be reduced. Thereby, the durability of the RF tag can be improved. As an example, the RF tag may be disposed at a position adjacent to the bead core in the tire radial direction or the tire width direction. It is difficult for distortion to concentrate in the vicinity of the bead core. Therefore, the load applied to the RF tag can be reduced. Thereby, the durability of the RF tag can be improved. In particular, it is preferable that the RF tag be disposed inside the tire in the tire radial direction from the position where the tire has its maximum width and outside the bead core of the bead portion in the tire radial direction. By doing so, the durability of the RF tag can be improved, and the communication between the RF tag and the reader is less likely to be inhibited by the bead core, and the communication performance of the RF tag can be enhanced. Also, when the side rubber is composed of a plurality of rubber members of the same or different types adjacent to each other in the tire radial direction, the RF tag may be disposed sandwiched between the plurality of rubber members constituting the side rubber. The RF tag may be disposed sandwiched between the stiffener and the member adjacent to the stiffener. By doing so, the RF tag can be disposed at a position where it is difficult for distortion to concentrate due to the disposition of the stiffener. Therefore, the load applied to the RF tag can be reduced. Thereby, the durability of the RF tag can be improved.The RF tag may be disposed, for example, sandwiched between a stiffener and a side rubber. Also, the RF tag may be disposed, for example, sandwiched between a stiffener and a carcass. The portion of the carcass that sandwiches the RF tag together with the stiffener may be located on the outer side in the tire width direction with respect to the stiffener, or may be located on the inner side in the tire width direction. When the portion of the carcass that sandwiches the RF tag together with the stiffener is located on the outer side in the tire width direction with respect to the stiffener, the load applied to the RF tag can be further reduced due to impacts and damages from the outer side of the tire in the tire width direction. Thereby, the durability of the RF tag can be further improved. The stiffener may include a portion disposed adjacent to a rubber chafer. In such a case, the RF tag may be disposed sandwiched between the stiffener and the rubber chafer. The stiffener may include a portion adjacent to the hat rubber on the outer side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the stiffener and the hat rubber. The stiffener may be composed of a plurality of rubber members having different hardnesses. In such a case, the RF tag may be disposed sandwiched between the plurality of rubber members constituting the stiffener. The RF tag may be disposed sandwiched between the hat rubber and a member adjacent to the hat rubber. The RF tag may be disposed, for example, sandwiched between the hat rubber and a carcass ply. By doing so, the impact on the RF tag can be mitigated by the hat rubber. Therefore, the durability of the RF tag can be improved.

[0034] The RF tag may be disposed, for example, sandwiched between a rubber chafer and a side rubber. By doing so, the RF tag can be disposed at a position where distortion is less likely to concentrate by disposing the rubber chafer. Therefore, the load applied to the RF tag can be reduced. Thereby, the durability of the RF tag can be improved. The RF tag may be disposed, for example, sandwiched between a rubber chafer and a carcass. By doing so, the load applied to the RF tag can be reduced due to the impact or damage applied from the rim. Therefore, the durability of the RF tag can be improved.

[0035] The RF tag may be disposed sandwiched between a nylon chafer and another member adjacent to the outer or inner side of the nylon chafer in the tire width direction. By doing so, when the tire is deformed, the position of the RF tag is less likely to fluctuate. Therefore, the load applied to the RF tag when the tire is deformed can be reduced. Thereby, the durability of the RF tag can be improved. The nylon chafer may include, for example, a portion adjacent to the rubber chafer on the outer side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the nylon chafer and the rubber chafer. The nylon chafer may include, for example, a portion adjacent to the side rubber on the outer side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the nylon chafer and the side rubber. The nylon chafer may include, for example, a portion adjacent to the stiffener on the inner side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the nylon chafer and the stiffener. Also, the nylon chafer may include, for example, a portion adjacent to the hat rubber on the inner side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the nylon chafer and the hat rubber. Further, the nylon chafer may include, for example, a portion adjacent to the carcass on the inner side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the nylon chafer and the carcass. Further, the nylon chafer may include, for example, a portion adjacent to the wire chafer on the inner side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the nylon chafer and the wire chafer. Thus, the RF tag may be disposed sandwiched between a nylon chafer and another member adjacent to the outer or inner side of the nylon chafer in the tire width direction. In particular, since the outer side of the RF tag in the tire width direction is covered by the nylon chafer, the load applied to the RF tag due to impact or damage from the outside of the tire in the tire width direction can be further reduced. Therefore, the durability of the RF tag can be further improved.

[0036] The RF tag may be disposed sandwiched between a wire chafer and another member adjacent to the inside or outside of the wire chafer in the tire width direction. By doing so, when the tire deforms, the position of the RF tag becomes difficult to fluctuate. Therefore, the load applied to the RF tag when the tire deforms can be reduced. Thereby, the durability of the RF tag can be improved. Another member adjacent to the wire chafer on the inside or outside in the tire width direction may be, for example, a rubber member such as a rubber chafer. Also, another member adjacent to the wire chafer on the inside or outside in the tire width direction may be, for example, a carcass.

Example

[0037] (Example 1) In order to simulate the behavior of the tire breaking due to the protrusion, a simulation is performed using a rubber piece on which a cord is laid. When the size of the rubber piece is kept constant and the fiber length (and thus the number of divisions and the cord length) is varied, the tensile force applied to the cord up to a certain displacement of pressing the protrusion is shown in FIG. 4 (although the numerical value is small, the smaller the tensile force, that is, the shorter the cord, the smaller the tensile force when the same displacement is applied, so it is less likely to break and is excellent as a function of the protective layer).

[0038] (Example 2) When the ratio of the divided width to the width in the tire width direction of the belt reinforcing layer was varied in various ways (conventional example and four others), a tire for trucks and buses with a tire size of 275 / 80R22.5 was mounted on a rim with a rim size of 22.5×8.25J and filled with an internal pressure of 900 kPa. Then, using a blade with a blade width of 46 mm and a blade tip angle of 60°, with the blade width in the rotation axis direction, a load was applied in the tire radial direction until the position where the tire broke. The evaluation results of the tire breaking energy (shown in Table 1 and FIG. 7 in an index display with the conventional example set to 1.00, and the larger the numerical value, the larger the tire breaking energy) are shown. Here, the tire breaking energy is an approximate value obtained by multiplying the load at the break point by the radial displacement amount from the position where the blade contacted the tire to the broken position and 1 / 2.

[0039]

Table 1

[0040] As shown in Table 1, it can be seen that in Comparative Examples 1 to 4, the tire breaking energy is large compared to the conventional example in all cases.

[0041] As shown in FIG. 7, it can be seen that since the belt reinforcing layer is divided at one or more locations, a larger tire breaking energy is required compared to the conventional example.

[0042] The heavy-duty tire of the present disclosure is particularly suitable for truck and bus tires. Alternatively, it can also be used for extra-large tires such as construction vehicle tires.

Explanation of Signs

[0043] 1: Tread portion, 2: Belt, 3: Belt reinforcing layer, 4: Rubber block, 5: Fiber, 6: Projection

Claims

1. A heavy-duty tire comprising a belt composed of one or more belt layers in a tread portion and one or more belt reinforcing layers disposed outside the belt in the tire radial direction, wherein the belt reinforcing layer has reinforcing cords rubber-coated, each of the reinforcing cords extends from one end to the other end of the belt reinforcing layer and is cut at the one end and the other end, each of the reinforcing cords is further divided at one or more locations between the one end and the other end, and the number of the reinforcing cords driven in is larger than the number of the belt cords of the belt, characterized in that it is a heavy-duty tire.

2. In a cross-section view in the tire width direction, the sum of the cross-sectional areas of the plurality of reinforcing cords with respect to the cross-sectional area of the belt reinforcing layer is equal to or greater than the sum of the cross-sectional areas of the plurality of belt cords of the outermost belt layer located outermost in the tire radial direction among the one or more belt layers, the heavy-duty tire according to claim 1.

3. Each of the divided reinforcing cords has a width in the tire width direction of 6.25 to 50% of the width in the tire width direction of the belt reinforcing layer, the heavy-duty tire according to claim 1 or 2.

4. Each of the divided reinforcing cords is in a state where at least a part of the dividing surfaces are in contact with each other, the heavy-duty tire according to claim 1 or 2.

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