JP2012046061A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing passage noise during vehicle traveling while flat spot performance and high-speed durability performance are secured.SOLUTION: In the pneumatic tire 10, a belt 12 is disposed in a tread forming position on the outside in the tire radial direction of a carcass 11, and a belt reinforcing layer 13 is formed by spirally winding a cord in the tire circumferential direction on the outside in the tire radial direction of the belt 12. The cord winding density of the belt reinforcing layer 13 is formed lower in the center in the tire width direction than the end in the tire width direction, and a distance in the tire radial direction from the surface of the belt 12 to the surface of the tread 14 is formed longer in the center in the tire width direction than in the end in the tire width direction.

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having a belt layer and a belt reinforcing layer covering a carcass.

  Conventionally, a carcass, a belt layer, and a band layer (belt reinforcement layer) made of a band ply formed by spirally winding a belt-shaped ply with a small width over the entire width of the belt layer on the outer side in the tire radial direction of the belt layer. Further, a “pneumatic radial tire” (see Patent Document 1) is known. In this “pneumatic radial tire”, the winding pitch of the belt-like ply is changed between the central portion and the outer portion of the tread in order to reduce road noise without deteriorating passing noise and rolling resistance.

  By the way, in a pneumatic tire, in order to improve the flat spot performance, that is, in order to make it difficult to generate a flat spot in which the ground contact portion with the road surface of the tire outer peripheral surface is deformed into a flat shape due to, for example, parking or storage. Therefore, in the conventional “pneumatic radial tire”, the belt-like ply forming the band layer is arranged at a pitch of 1.0 times the width of the belt-like ply. It was spirally wound in the direction.

JP 2003-182307 A

  However, when the belt layer is formed by spirally winding the belt-like ply in the tire circumferential direction to increase the tire circumferential rigidity of the belt, the deformation of the belt in the tire circumferential direction is suppressed, so that the tire The contact width between the outer peripheral surface and the road surface is increased. If the contact width between the tire outer peripheral surface and the road surface increases, the sound field characteristic formed between the tire and the road surface will be deteriorated, and as a result, the passing noise (external vehicle noise) will increase during vehicle travel. Is inevitable.

  Therefore, in order to suppress an increase in the contact width with the road surface of the tire outer peripheral surface, it is necessary to reduce the tire circumferential rigidity of the band ply formed by spirally winding the band cord in the tire circumferential direction. If the rigidity of the entire band ply is lowered, the rigidity necessary for the outer portion (tread shoulder portion) of the tread cannot be ensured, and the high-speed durability performance is lowered. For this reason, it has been impossible to reduce the passing noise when the vehicle is running while ensuring the required flat spot performance and high-speed durability performance.

  The object of the present invention is to reduce the passing noise when the vehicle is running while ensuring the flat spot performance and the high-speed durability performance required for the belt reinforcement layer formed by winding the cord-shaped belt-like ply spirally in the tire circumferential direction. It is to provide a pneumatic tire that can.

In order to achieve the above object, a pneumatic tire according to the present invention has a belt disposed at a tread formation position on the outer side in the tire radial direction of the carcass, and a cord is spirally formed in the tire circumferential direction on the outer side in the tire radial direction of the belt. In the pneumatic tire in which the belt reinforcing layer is formed by winding, the winding density of the cord of the belt reinforcing layer is formed lower in the center portion in the tire width direction than in the end portion in the tire width direction. The distance in the tire radial direction from the radially outermost surface to the tread surface is longer at the tire width direction center than at the tire width direction end. The belt reinforcement layer is wound by changing the pitch of the belt in which the cords are arranged, thereby changing the winding density (number per unit width) of the cords.
In the pneumatic tire according to another aspect of the present invention, the end portion in the tire width direction of the belt reinforcing layer has a two-layer structure in which the cords are stacked in the tire radial direction.

In the pneumatic tire according to another aspect of the present invention, the belt reinforcing layer is composed of a composite cord in which a high elastic filament and a low elastic filament are twisted together.
In the pneumatic tire according to another aspect of the present invention, the composite cord has a low elastic region from the origin of the load-elongation curve to the inflection point and a high elastic region beyond the inflection point. The elongation ratio with respect to the inner cord length is equal to or less than the elongation at the inflection point. Here, the inside of the tire is in the state of “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. . The inflection point is exceeded during high speed driving.
Further, in the pneumatic tire according to another aspect of the present invention, the expansion ratio at the time of vulcanization of the belt reinforcing layer is larger in the center portion in the tire width direction than in the end portion in the tire width direction.

  According to the pneumatic tire according to the present invention, the winding density of the cord of the belt reinforcing layer is formed lower in the tire width direction center than in the tire width direction end, and from the outermost surface of the belt in the tire radial direction. Since the distance in the tire radial direction to the tread surface is longer at the center in the tire width direction than at the end in the tire width direction, it is necessary for the belt reinforcement layer formed by spirally winding the cord in the tire circumferential direction. It is possible to reduce the passing noise during traveling of the vehicle while ensuring the flat spot performance and the high speed durability performance.

Further, according to the pneumatic tire according to another aspect of the present invention, the end of the belt reinforcing layer in the tire width direction has a two-layer structure in which the cords are stacked in the tire radial direction, so that the tension of the tread shoulder portion is increased. Sufficient tension can be secured, and sufficient high-speed durability can be provided.
Further, according to the pneumatic tire according to another aspect of the present invention, the expansion ratio at the time of vulcanization of the belt reinforcing layer is larger in the center portion in the tire width direction than in the end portion in the tire width direction, so that the flat spot performance and It is possible to more accurately achieve the reduction of passing noise during vehicle travel while ensuring high-speed durability performance.

It is explanatory drawing which shows typically the structure of the pneumatic tire which concerns on one embodiment of this invention. It is a cross-sectional explanatory drawing explaining the calculation method of the belt expansion rate at the time of the expansion change at the time of vulcanization in a hybrid layer belt structure.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view schematically showing a configuration of a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 1, a pneumatic tire 10 includes a radial structure carcass 11, a belt 12 disposed on the outer side in the tire radial direction of the carcass 11, a belt reinforcing layer 13 disposed on the outer side in the tire radial direction of the belt 12, and A tread 14 serving as a tire tread is disposed outside the belt reinforcing layer 13 in the tire radial direction.

The carcass 11 is constructed in a toroidal shape between a pair of left and right bead cores (not shown) having an annular structure to constitute a tire skeleton, and the belt 12 overlaps the tire radius direction of the carcass 11 at the tire crown. At least two belt layers (for example, the first belt 12a and the second belt 12b are illustrated) are configured.
The belt reinforcing layer 13 is formed by continuously winding a composite cord (cord width: about 6 mm) in which a high elastic fiber (high elastic filament) and a low elastic fiber (low elastic filament) are twisted in a spiral shape in the tire circumferential direction. It is formed by doing. As the high elastic fiber, for example, an aromatic polyamide fiber is used, and as the low elastic fiber, for example, a nylon fiber is used, and the composite cord is formed in a rubber-coated sheet shape to form a belt belt.

  This composite cord has a low elastic region from the origin of the load-elongation curve to the inflection point and a high elastic region exceeding the inflection point, and the elongation of the cord at the inflection point is 2 to 7%. In addition, the inside of the tire is in the state of “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. The elongation ratio with respect to the cord length is equal to or less than the elongation (2 to 7%) of the cord at the inflection point.

  The belt reinforcing layer 13 is a high-density portion in which the winding pitch when the belt-like belt is spirally wound in the tire circumferential direction is 1.0 to 1.1 times the width of the composite cord (cord width). And, the winding pitch is formed of two types of regions having different winding pitch densities in the tire width direction in the low density portion having a cord width of 1.4 to 1.7 times the cord width. That is, the length in the tire width direction (high density portion width W1) of the high density portion in which the winding pitch of the belt-like belt is 1.0 to 1.1 times the cord width is the entire region of the belt reinforcing layer 13 in the tire width direction. The belt end is set to a length, that is, a range of 16 to 28% of the entire belt width W. The outer portion in the tire width direction of the high-density portion, which is a part of the high-density portion of the belt reinforcing layer 13, is formed in a two-layer structure including a lower belt 13a and an upper belt 13b in which the composite cord overlaps in the tire radial direction. The belt width W2 of the upper belt 13b on the outer side in the tire radial direction is set to a range of 5 to 16% with respect to the total belt width W.

  Therefore, on the central portion of the belt reinforcing layer 13 in the tire width direction (near the tire equator CL), the composite cord with respect to the cord width is arranged in the tire circumferential direction as compared with the end portion in the tire width direction (tread shoulder portion) that is the belt end portion. The amount of movement in the tire width direction after one turn is increased.

  Further, when the belt 12 is constituted by two belt layers, the expansion rate at the time of reinforcing layer vulcanization at the end portion in the tire width direction of the second belt 12b overlapping the outer side in the tire radial direction of the first belt 12a is 0.5. ~ 0.95%, expansion rate at the time of reinforcing layer vulcanization at the center of the belt 12 in the tire width direction (tire equator CL) is less than 1.5 to 1.8% (previously 1.8 to 2.2%) And The expansion rate at the time of vulcanization layer vulcanization is the expansion rate of the belt reinforcement layer 13 when an unvulcanized tire is vulcanized by a vulcanization mold in the manufacturing process of the pneumatic tire 10.

In addition, the distance in the tire radial direction from the outermost surface in the tire radial direction of the belt 12 to the surface of the tread 14 in the tire width direction central portion (tire equator CL) is determined in the tire width direction of the composite cord forming the belt reinforcing layer 13. The tire diameter from the outermost surface in the tire radial direction of the belt 12 to the surface of the tread 14 at the end portion in the tire width direction where the movement amount is switched, that is, where the winding pitch is switched from the high density portion to the low density portion. The distance is 1.2 to 1.8 times the directional distance.
Thus, by increasing the thickness of the tread 14 at the center in the tire width direction (tire equator CL) as compared with the conventional one, the expansion rate during vulcanization of the belt reinforcing layer 13 at the center in the tire width direction is higher than before. As a result, the tension of the composite cord in the center portion in the tire width direction is lowered as compared with the conventional case.

  When the distance in the tire radial direction at the center in the tire width direction is less than 1.2 times the distance in the tire radial direction at the end in the tire width direction, the expansion ratio during vulcanization of the belt reinforcing layer 13 in the center in the tire width direction is 1. When it is less than 5 to 1.8%, it is difficult to secure an expansion rate of 0.5% or more of the belt reinforcing layer 13 at the end portion in the tire width direction at the time of vulcanization. When the radial distance exceeds 1.8 times the distance in the tire radial direction at the end in the tire width direction, the vulcanization expansion rate of the belt reinforcing layer 13 in the center in the tire width direction is less than 1.5 to 1.8%. This is because it is difficult to ensure an expansion rate of 0.95% or less during vulcanization of the belt reinforcing layer 13 at the end in the tire width direction. Here, the reason why the expansion rate during vulcanization is 0.5% or more is that if the expansion rate during vulcanization is less than 0.5%, the rigidity of the shoulder portion cannot be secured, so that high-speed durability cannot be secured. The reason why the expansion rate during vulcanization is 0.95% or less is that if the expansion rate during vulcanization exceeds 0.95%, problems in production occur.

The cord stress is 80.7 to 112.6 N / mm ² in the conventional pneumatic tire, whereas the pneumatic tire 10 according to the present invention is less than 48.4 to 80.7 N / mm ² in the cord stress. is there.
As described above, the high-density portion having a winding pitch of 1.0 to 1.1 times the composite cord width is provided with a double-layer structure, so that the winding pitch is equal to the composite cord width. This is because high-speed durability can be ensured even if it is not less than 1.0 times. On the other hand, if the winding pitch exceeds 1.1 times the composite cord width, the effect of securing the tension at the shoulder portion is reduced. This is because the high-speed durability decreases.

  In addition, the low density portion having a winding pitch of 1.4 to 1.7 times the composite cord width is provided because the tire of the belt reinforcing layer 13 is provided when the winding pitch is less than 1.4 times the composite cord width. When the winding pitch exceeds 1.7 times the composite cord width, air may enter between the cord gaps of the composite cord. This is because it becomes a defective product.

  The length of the high-density portion of the belt reinforcing layer 13 in the tire width direction (high-density portion width W1) is in the range of 16 to 28% of the total belt width W when it is less than 16% of the total belt width W. This is because the effect of securing the tension in the tread shoulder portion is reduced and the high-speed durability is lowered. When the belt width exceeds 28% of the total belt width W, the effect of lowering the tension in the low-density portion is reduced, and the tire outer peripheral surface. This is because the effect of reducing the contact width with the road surface cannot be sufficiently obtained.

  Further, the composite cord of the high density portion, which is a part of the belt reinforcing layer 13, is formed in a two-layer structure overlapping in the tire radial direction, and the belt width W2 of the upper belt 13b is 5 to 5 with respect to the total belt width W. The range of 16% is set because if the belt width W2 of the upper belt 13b is less than 5% of the total belt width W, the effect of securing the tension in the tread shoulder portion is reduced and the high-speed durability is lowered. If the belt width exceeds 16% of the total belt width W, the effect of lowering the tension in the low density portion is reduced, and the effect of lowering the contact width with the road surface of the tire outer peripheral surface cannot be sufficiently obtained.

  Further, the expansion rate at the time of reinforcing layer vulcanization at the end portion in the tire width direction of the second belt 12b constituting the belt 12, that is, the tread shoulder portion, is 0.5 to 0.95% when the reinforcing layer is vulcanized. If the expansion rate is less than 0.5%, the effect of securing the tension in the tread shoulder portion is small, so high-speed durability cannot be sufficiently ensured. If the expansion rate exceeds 0.95% when the reinforcing layer is vulcanized, the belt This is because there are inconveniences in tire manufacturing, such as cord touch between plies and unevenness in the belt.

  The expansion rate at the time of reinforcing layer vulcanization in the center portion of the belt 12 in the tire width direction, that is, the tread center (tire equator CL) is 1.5 to less than 1.8%. If it is less than 1.5%, sufficient flat spot performance cannot be ensured, and if the expansion rate during reinforcement layer vulcanization is 1.8% or more, the belt tension at the center in the tire width direction of the belt 12 is lowered. This is because there are few effects and the passage noise cannot be improved.

  The expansion rate during vulcanization of the reinforcing layer of the belt located on the tread shoulder is usually calculated at the hump (protrusion) position on the wheel to prevent bead detachment when the air pressure drops. In the case of a hybrid (HYBRID) layer belt structure including two types of belts having different physical properties such as the tire 10, the calculation is performed at the end portion e of the second belt 12b where the cord touch is likely to occur.

FIG. 2 is a cross-sectional explanatory view for explaining a method of calculating the belt expansion rate at the time of vulcanization expansion change in the hybrid layer belt structure. As shown in FIG. 2, the belt expansion rate of the tread center portion and the tread shoulder portion (second belt 12b end portion e) in the hybrid layer belt structure is calculated by the following equation.
Center part belt expansion ratio = ((mold inner diameter a−tire equator CL belt upper dimension b × 2) × φ / BT circumference−1)
Shoulder belt expansion ratio = ((mold inner diameter a− (second belt 12b end mold drop dimension c + second belt 12b end belt upper dimension d) × 2) × φ / BT circumference−1)
Here, φ is the circumference ratio, and BT circumference is the circumference of the drum to which the belt is attached.

  As described above, since the high-density portion of the end portion (tread shoulder portion) in the tire width direction of the belt reinforcing layer 13 is formed in two layers, the tension of the tread shoulder portion can be increased and sufficient tension can be secured. The required flat spot performance and high-speed durability can be provided. Further, by forming a low density portion in the center portion in the tire width direction (tire equator CL portion) of the belt reinforcing layer 13, by reducing the tension in the center portion in the tire width direction, the belt reinforcing layer 13 in the belt circumferential direction. The deformation of the tire is promoted, and the contact width between the tire outer peripheral surface and the road surface is suppressed from increasing, and noise can be reduced.

Next, the pneumatic tire 10 based on the specifications in Table 1 was tested for high speed durability performance, flat spot performance, and noise performance, and compared with a conventional tire.
The pneumatic tire 10 and the conventional tire have a tire size of 295 / 30ZR20, and the pneumatic tire 10 has a winding pitch of the low density portion set to 1.5 times the winding pitch of the conventional tire, and a high density portion. The width (W1) of the conventional tire was 21%, and the expansion ratio at the time of vulcanization of the belt center reinforcing layer was 1.80% compared to 2.20% of the conventional tire (see Table 1).

  The pneumatic tire 10 and the conventional tire are assembled to an applicable rim defined by JATMA (Japan Automobile Tire Association) standard according to the tire size to form a tire assembly (wheel), and the rim width is 11 J- The high-speed durability performance was compared by a stepped speed step maintained at a constant speed for a predetermined time under the conditions of 20, internal pressure of 260 kPa, load of 4.95 kN, and camber angle of 2.5 ° (see Table 2).

  Further, the pneumatic tire 10 and the conventional tire are assembled to an applicable rim defined by the JATMA standard according to the tire size to form a tire assembly (wheel), the rim width is 11J-20, the internal pressure is 220 kPa, Under the condition that the load is 5.0 kmN, the speed is increased stepwise from 20 km / h to 105 km / h and further to 150 km / h and then stepped from 150 km / h to 105 km / h and further to 20 km / h. And then continuously increased from 20 km / h to 150 km / h, then decreased from 150 km / h to 0 km / h at a stretch and maintained at 0 km / h for a certain period of time, then from 0 km / h to 20 km / H, further increased stepwise to 105 km / h, then maintained at a constant time of 105 km / h, then from 105 km / h to 20 km / h, further to 0 km / h The speed steps stepwise lowered, and compared the performance against the flat spot.

  Further, a tire assembly (wheel) of this pneumatic tire 10 and a conventional tire is formed, and noise is obtained under the conditions of a rim width of 11J-20, an internal pressure of 220 kPa, a load of 5.0 kN, and a speed of 60 km / h. Were compared (see Table 3).

Table 4 shows the results of the above test.
As shown in Table 4, the pneumatic tire 10 according to the present invention is a pneumatic tire having a radial structure including a belt reinforcing layer, and ensures high-speed durability performance and flat spot performance similar to those of conventional tires. On the other hand, with respect to noise, it was confirmed that the improvement effect of 2 points compared with the conventional tire, that is, the passing noise during vehicle running was reduced.

  According to the present invention, it is possible to reduce the passing noise during traveling of the vehicle while ensuring the flat spot performance and the high-speed durability performance required in the belt reinforcing layer formed by spirally winding the cord in the tire circumferential direction. Therefore, it is suitable for a pneumatic tire having a belt layer and a belt reinforcing layer covering the carcass.

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 11 Carcass 12 Belt 12a 1st belt 12b 2nd belt 13 Belt reinforcement layer 13a Lower belt 13b Upper belt 14 Tread CL Tire equator W Full belt width W1, W2 Belt width a Mold inner diameter b Tire equator belt upper dimension c Second belt end mold drop dimension d Second belt end belt upper dimension e End

Claims (5)

In a pneumatic tire in which a belt is disposed at a tread formation position on the outer side in the tire radial direction of the carcass, and a belt reinforcing layer is formed by spirally winding a cord in the tire circumferential direction on the outer side in the tire radial direction of the belt.
The winding density of the cord of the belt reinforcement layer is formed lower in the tire width direction center than in the tire width direction end,
The pneumatic tire is characterized in that the distance in the tire radial direction from the outermost surface in the tire radial direction of the belt to the tread surface is longer at the center in the tire width direction than at the end in the tire width direction.   2. The pneumatic tire according to claim 1, wherein the end portion in the tire width direction of the belt reinforcing layer has a two-layer structure in which the cords are stacked in a tire radial direction.   The pneumatic tire according to claim 1 or 2, wherein the belt reinforcing layer is made of a composite cord in which a high elastic filament and a low elastic filament are twisted together.   The composite cord has a low elastic region extending from the origin of the load-elongation curve to the inflection point and a high elastic region exceeding the inflection point, and the elongation ratio with respect to the cord length inside the tire is the elongation at the inflection point. The pneumatic tire according to any one of claims 1 to 3, wherein:   The pneumatic tire according to any one of claims 1 to 4, wherein an expansion rate during vulcanization of the belt reinforcing layer is larger in a tire width direction central portion than in a tire width direction end portion.

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