JP2016215831A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that allows the possible number of times of retread to increase by suppressing oxidation degradation of a belt layer and eventually elongating a casing lifetime as a regenerative tire.SOLUTION: In the pneumatic tire, a carcass layer 4 including a plurality of carcass cords is attached between a pair of bead parts 3 and 3, and a belt layer 9B is arranged at an outer periphery side of the carcass layer 4 in a tread part 1. As the carcass cords, steel cords 30 are used which have a structure in which at least nine wires 31 with wire diameters of 0.22 mm or less are twisted together, and in a shoulder region of the tread part 1 is provided at least one narrow hole 40 that extends from the vicinity of the belt layer 9B and the carcass layer 4 toward outside in a tire width direction and opens to an outer surface of the tire.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire provided with a carcass layer and a belt layer. More specifically, the present invention suppresses oxidative deterioration of the belt layer, thereby extending the casing life as a retreaded tire and increasing the number of possible retreads. The present invention relates to a pneumatic tire.

  For example, a heavy duty pneumatic tire used for trucks and buses has a carcass layer including a plurality of carcass cords between a pair of bead portions, and a belt layer on the outer periphery side of the carcass layer in the tread portion. It has an arranged structure. In the pneumatic tire having such a structure, the high-pressure air filled in the tire passes through the inner liner layer to reach the carcass layer, and further passes through the carcass layer to reach the belt layer. Oxygen oxidizes and degrades the belt layer coat rubber.

  When the oxidative deterioration of the belt layer occurs in this way, not only the durability of the pneumatic tire is lowered, but also the casing life as a retread tire is shortened, and there is a problem that the number of retreadable times is reduced.

  On the other hand, it has been proposed that an oxygen absorbent is blended in the inner liner layer and that the oxygen absorbent suppresses the arrival of oxygen to the belt layer and prevents oxidative deterioration of the belt layer (for example, patents). Reference 1). However, in this case, since the absorption effect by the oxygen absorbent is limited, the oxidative deterioration of the belt layer cannot be prevented over a long period of time.

  In addition, it has been proposed to prevent oxidative degradation of the belt layer by wrapping the belt layer with a thin film of a resin material (see, for example, Patent Document 2). However, in this case, since the adhesion between the thin film and the rubber layer in a state where the tread portion is heated is not necessarily guaranteed, a structure in which the belt layer is wrapped with a thin film of a resin material has not been put into practical use. .

JP 2011-20672 A JP 2009-279773 A

  An object of the present invention is to provide a pneumatic tire that suppresses oxidative degradation of a belt layer, and thus extends the casing life as a retread tire and increases the number of retreadable times.

  In order to achieve the above object, the pneumatic tire of the present invention has a carcass layer including a plurality of carcass cords mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion. In the pneumatic tire, a steel cord having a structure in which nine or more strands having a strand diameter of 0.22 mm or less are twisted as the carcass cord is used, and the belt layer and the shoulder layer in the shoulder region of the tread portion are used. It is characterized in that at least one fine hole is provided extending from the vicinity of the carcass layer toward the outer side in the tire width direction and opening on the outer surface of the tire.

  In the present invention, a steel cord having a structure in which nine or more strands having a strand diameter of 0.22 mm or less are twisted is used as the carcass cord. However, since such a carcass cord has poor rubber permeability, The air that has entered the inner space of the cord can move along the longitudinal direction of the carcass cord. On the other hand, the inner space of the carcass cord is provided by providing at least one fine hole extending in the tire width direction outside from the vicinity of the belt layer and the carcass layer in the shoulder region of the tread portion and opening on the outer surface of the tire. The air that has entered the tire is discharged to the outside of the tire through the pores. In particular, the shoulder region of the tread portion generates heat due to cyclic deformation during tire running, and the heat generation temperature is higher than that of other parts, so that air easily diffuses in the rubber. In order to secure the exhaust speed, it is optimal as a part where the pores are arranged.

  In the pneumatic tire according to the present invention, when the air filled in the tire passes through the inner liner layer and reaches the carcass layer, the air is discharged to the outside of the tire through an exhaust path including the carcass layer and pores. Therefore, the oxidative deterioration of the belt layer can be effectively suppressed over a long period of time. As a result, it is possible to increase the number of retreadables by extending the casing life as a retreaded tire.

  In the present invention, a gas permeation promoting layer made of a styrene-butadiene rubber compound is provided between the carcass layer and the pores, and the gas permeation promoting layer is disposed in contact with both the carcass layer and the pores. It is preferable to do. Styrene-butadiene rubber-based compounds are easier to permeate air (especially oxygen) than natural rubber in an exothermic state, and therefore a gas permeation promoting layer made of such a compound is interposed between the carcass layer and the pores. Thus, the air reaching the carcass layer can be effectively discharged outside the tire, and the oxidative deterioration of the belt layer can be effectively suppressed. Further, the gas permeation promoting layer is preferably arranged so as to continuously extend along the tire circumferential direction. In such an arrangement, the gas permeation promoting layer is promoted from the carcass cord of the carcass layer throughout the tire circumferential direction. Air can be taken into the layer and the air can be directed to the pores.

  In addition, it is preferable to provide an air storage cavity that swells more than the pores in an intermediate portion in the longitudinal direction of the pores. By providing such an air accumulating cavity, a pumping effect by the air accumulating cavity can be obtained when the shoulder region of the tread portion is deformed, so that the discharge of air from the carcass layer can be promoted.

  In the present invention, it is preferable to arrange the pores so that the shortest distance Db from the belt layer to the fine pores is 8 mm or less and the shortest distance Dc from the carcass layer to the fine pores is 2 mm or less. Thereby, the air which reached | attained the carcass layer can be discharged | emitted effectively outside a tire, and the oxidative degradation of a belt layer can be suppressed effectively.

The inner diameter of the pores is preferably 1 mm to 3 mm. Thereby, the air discharge path can be formed without adversely affecting the tire performance. In particular, when a check valve that allows the passage of fluid to the outside of the tire is inserted into the pores, in addition to being able to effectively exhaust the air inside the pores to the outside of the tire, an air exhaust path is formed. In doing so, it is possible to prevent water from entering the pores.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a side view which shows the pneumatic tire of FIG. It is a cross-sectional view which shows an example of the steel cord used for the pneumatic tire of FIG. It is a cross-sectional view which shows the other example of the steel cord used for the pneumatic tire of FIG. It is a cross-sectional view showing still another example of the steel cord used in the pneumatic tire of FIG. It is sectional drawing which expands and shows the principal part of the pneumatic tire of FIG. It is sectional drawing which shows the principal part of the pneumatic tire which consists of other embodiment of this invention. It is a side view which shows the pneumatic tire of FIG. It is sectional drawing which shows the principal part of the pneumatic tire which consists of further another embodiment of this invention. It is sectional drawing which shows the principal part of the pneumatic tire which consists of further another embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 show a heavy duty pneumatic tire according to an embodiment of the present invention. Although FIG. 1 shows only a portion on one side of the tire center line CL, this pneumatic tire has a structure corresponding to the other side of the tire center line CL.

  As shown in FIGS. 1 and 2, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions that are disposed on both sides of the tread portion 1. 2 and 2 and a pair of bead portions 3 and 3 disposed on the inner side in the tire radial direction of the sidewall portions 2.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is wound around the bead core 5 disposed in each bead portion 3 from the tire inner side to the outer side. Each bead portion 3 includes a cord reinforcing layer 6 extending along the carcass layer 4 so as to wrap the bead core 5, and cord reinforcing layers 7 and 8 positioned on the outer side in the tire width direction from the rolled-up portion of the carcass layer 4. Buried.

  A plurality of belt layers 9A, 9B, 9C, and 9D are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 9A to 9D include a plurality of belt cords inclined with respect to the tire circumferential direction, and are arranged so that the belt cords cross each other between the layers. In the belt layers 9A to 9D, the inclination angle of the belt cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 60 °. Steel cords are preferably used as the belt cords of the belt layers 9A to 9D.

  The tread portion 1 includes a tread rubber layer 11 positioned on the outer peripheral side of the belt layers 6A to 6D, a belt edge cover rubber layer 12 that covers the belt edge portion, and a belt edge cushion rubber layer 13 that supports the belt edge portion. Is arranged. A side rubber layer 14 located on the outer side in the tire width direction of the carcass layer 4 is disposed on the sidewall portion 2. In the bead portion 3, a lower bead filler 15 located on the outer peripheral side of the bead core 5, an upper bead filler 16 located on the outer peripheral side of the lower bead filler 15, and a first portion that comes into contact with the rolled-up portion of the carcass layer 4. A rim cushion rubber layer 17, a second rim cushion rubber layer 18 positioned on the outer side in the tire width direction of the cord reinforcing layers 7 and 8, and a third rim cushion rubber layer 19 positioned on the outer surface of the tire are disposed. Further, an inner liner layer 20 is disposed along the carcass layer 4 on the tire inner surface.

  In the pneumatic tire, as a carcass cord constituting the carcass layer 4, a steel cord 30 having a structure in which nine or more strands 31 having a strand diameter of 0.22 mm or less are twisted together (see FIGS. 3 to 5). ) Is used. In particular, the steel cord 30 preferably has a multi-layer twisted structure, and preferably has an internal space (a portion into which rubber does not permeate) continuous in the longitudinal direction in a state after tire vulcanization. The steel cord 30 may have a close-packed structure. If the wire diameter is larger than 0.22 mm, the flexibility of the carcass cord deteriorates. If the number of strands 31 to be twisted is less than 9, the rubber easily penetrates into the cord during vulcanization, so that the internal space is reduced. It becomes difficult to form. More preferably, the strand diameter is 0.17 mm to 0.22 mm, and the number of strands 31 to be twisted is 9 to 30. 3 shows a 3 + 7 structure, FIG. 4 shows a 3 + 9 structure, and FIG. 5 shows a 1 + 18 structure. In addition, for example, a 3 + 6 structure and a 3 + 9 + 15 structure are adopted. Is possible.

  In the pneumatic tire described above, the shoulder region of the tread portion 1 includes a plurality of fine openings that extend from the vicinity of the widest belt layer 9B and the carcass layer 4 toward the outer side in the tire width direction and open to the outer surface of the tire. A hole 40 is formed. As shown in FIG. 2, the plurality of pores 40 are arranged at equal intervals along the tire circumferential direction. As shown in FIG. 6, the pores 40 are arranged such that the shortest distance Db from the belt layer 9B to the pores 40 is 8 mm or less and the shortest distance Dc from the carcass layer 4 to the pores 40 is 2 mm or less. Has been. By arranging the pores 40 at positions that satisfy such distances Db and Dc, the air that has reached the carcass layer 4 can be effectively discharged outside the tire. If the shortest distance Db from the belt layer 9B to the pores 40 is too large, the air diffusion effect due to heat generation is reduced, and if the shortest distance Dc from the carcass layer 4 to the pores 40 is too large, the air from the carcass layer 4 The effect of discharging is reduced.

  According to the pneumatic tire described above, the steel cord 30 having a structure in which nine or more strands 31 having a strand diameter of 0.22 mm or less are twisted is used as the carcass cord constituting the carcass layer 4. When the high-pressure air filled in the tire passes through the inner liner layer 20 and reaches the carcass layer 4, the air that has entered the inner space of the carcass cord can move along the longitudinal direction of the carcass cord. On the other hand, the shoulder region of the tread portion 1 is provided with at least one pore 40 that extends from the vicinity of the belt layer 7B and the carcass layer 4 toward the outer side in the tire width direction and opens to the outer surface of the tire. The air that has entered the interior space of the carcass cord is discharged to the outside of the tire through the pores 40. In particular, the shoulder region of the tread portion 1 generates heat when the tire is running, and since the heat generation temperature is higher than that of other portions, air easily diffuses in the rubber of the belt edge cushion rubber layer 13. It becomes easy to move toward the pore 40.

  In the pneumatic tire described above, when the air filled in the tire passes through the inner liner layer 20 and reaches the carcass layer 4, the air is passed through the exhaust path including the carcass layer 4 and the pores 40 to the outside of the tire. Since it can discharge | emit, permeation of the air to belt layer 9A-9D can be reduced, and the oxidative degradation of belt layer 9A-9D can be suppressed effectively over a long period of time. As a result, for example, in a heavy-duty pneumatic tire used for trucks and buses, it is possible to increase the number of retreadables by extending the casing life as a retreaded tire.

  In the pneumatic tire, the inner diameter of the pores 40 is preferably set to 1 mm to 3 mm. Thereby, the air discharge path can be formed without adversely affecting the tire performance. If the inner diameter of the pores 40 is too small, the air cannot be effectively discharged. Conversely, if the pores are too large, water easily enters or cracks are likely to occur.

  7 and 8 show a pneumatic tire according to another embodiment of the present invention. In FIG. 7, a gas permeation promoting layer 41 made of a styrene-butadiene rubber (SBR) compound is provided between the carcass layer 4 and the pores 40. It arrange | positions so that it may contact with respect to both the pores 40. FIG. Since the SBR compound is more easily permeable to air (particularly oxygen) than the natural rubber in the heat generation state, the gas permeation promoting layer 41 made of such a compound is interposed between the carcass layer 4 and the pores 40. Thus, the air reaching the carcass layer 4 can be effectively discharged to the outside of the tire, and the oxidative degradation of the belt layers 9A to 9D can be effectively suppressed.

  The SBR compound means a compound in which 50% by weight or more of the polymer component is SBR, and other rubbers may be blended in the compound as a polymer component as long as this blending amount is satisfied. Of course, in addition to the polymer component, a compounding agent such as a filler, a crosslinking agent, a softening agent, an anti-aging agent, and a processing aid can be appropriately added to the compound.

  As shown in FIG. 8, the gas permeation promoting layer 41 is disposed so as to continuously extend along the tire circumferential direction. In such an arrangement, air can be taken into the gas permeation promoting layer 41 from the carcass cord of the carcass layer 4 in the entire region in the tire circumferential direction, and the air can be guided to the pores 40 arranged intermittently. The gas permeation promoting layer 41 preferably extends continuously along the tire circumferential direction, but may extend intermittently along the tire circumferential direction.

  FIG. 9 shows a pneumatic tire according to still another embodiment of the present invention. In FIG. 9, an air accumulation cavity 42 swelled more than the pore 40 is locally formed in an intermediate portion in the longitudinal direction of the pore 40. When the air accumulating cavity 42 is provided in the middle of the pore 40, the pumping effect by the air accumulating cavity 42 is obtained when the shoulder region of the tread portion 1 is deformed as the tire travels. Emission can be promoted.

  FIG. 10 shows a pneumatic tire according to still another embodiment of the present invention. In FIG. 10, a check valve 43 is inserted into the pore 40. The check valve 43 is a directional valve having a structure that allows only fluid (gas and liquid) to pass outside the tire and prohibits passage of fluid from the outside of the tire. By installing such a check valve 43 in the pore 40, the air in the pore 40 can be effectively exhausted to the outside of the tire. Intrusion of moisture into 40 can be prevented. When moisture enters the pores 40 and the moisture reaches the belt edge portion, it causes rusting in the belt edge portion. However, the installation of the check valve 43 can effectively prevent rusting. it can.

  In a pneumatic tire in which a carcass layer including a plurality of carcass cords is mounted between a pair of bead portions with a tire size of 11R22.5 and a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion, A steel cord having a structure (elementary wire diameter: 0.20 mm) is used, and a plurality of cords that extend from the vicinity of the belt layer and the carcass layer toward the outer side in the tire width direction and open to the outer surface of the tire in the shoulder region of the tread portion Tires of Examples 1 to 4 were prepared, which had the same structure as shown in FIG. 6, FIG. 7, FIG. 9, or FIG. 10. At that time, the pores were arranged so that the shortest distance Db from the belt layer to the fine pores was 8 mm and the shortest distance Dc from the carcass layer to the fine pores was 2 mm.

  For comparison, a conventional tire having the same structure as Example 1 was prepared except that no pores were provided in the shoulder region of the tread portion.

  For the tires of these conventional examples and Examples 1 to 4, the peel strength of the belt layer was evaluated by the following evaluation method, and the results are shown in Table 1.

The peel strength of the belt layer:
A test tire is mounted on a drum testing machine, and a running test is performed under the conditions of an air pressure of 800 kPa, a load of 27.5 km, and a speed of 60 km / h. After running for 20000 km, each test tire is collected and a specific belt layer is adjacent to it. The peeling force when peeling from other belt layers was measured. The evaluation results are shown as an index with the conventional example being 100. A larger index value means that the peel strength of the belt layer is larger, that is, less oxidative deterioration of the belt layer.

  As can be seen from Table 1, in each of the tires of Examples 1 to 4, the peel strength of the belt layer was large in comparison with the conventional example. That is, in Examples 1 to 4, the shoulder region of the tread portion is provided with pores that extend from the vicinity of the belt layer and the carcass layer toward the outer side in the tire width direction and open to the outer surface of the tire. Oxidative degradation was reduced.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 9A, 9B, 9C, 9D Belt layer 30 Steel cord 31 Strand 40 Pore 41 Gas permeation promotion layer 42 Air storage cavity 43 Check valve

Claims (7)

  In a pneumatic tire in which a carcass layer including a plurality of carcass cords is mounted between a pair of bead portions, and a belt layer is disposed on the outer peripheral side of the carcass layer in a tread portion, the wire diameter of the carcass cord is 0. A steel cord having a structure in which nine or more strands of 22 mm or less are twisted together is used, and the shoulder region of the tread portion extends from the vicinity of the belt layer and the carcass layer toward the outside in the tire width direction. A pneumatic tire characterized in that at least one fine hole opened on the outer surface of the tire is provided.   A gas permeation promoting layer made of a styrene-butadiene rubber compound is provided between the carcass layer and the pores, and the gas permeation promoting layer is disposed so as to be in contact with both the carcass layer and the pores. The pneumatic tire according to claim 1, wherein   The pneumatic tire according to claim 2, wherein the gas permeation promoting layer is disposed so as to continuously extend along a tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 3, wherein an air storage cavity that is larger than the pores is provided at an intermediate portion in a longitudinal direction of the pores.   The short pore distance Db from the belt layer to the fine pore is 8 mm or less, and the fine pore is arranged so that the shortest distance Dc from the carcass layer to the fine pore is 2 mm or less. The pneumatic tire according to any one of 1 to 4.   The pneumatic tire according to claim 1, wherein an inner diameter of the pore is 1 mm to 3 mm.   The pneumatic tire according to claim 1, wherein a check valve that allows passage of fluid to the outside of the tire is inserted into the pore.

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