JP5415719B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can reduce the weight of the tire while ensuring the steering performance of the tire in a configuration having a split carcass structure.

  In recent pneumatic tires, in order to reduce the weight of the tire, a configuration in which the carcass layer is divided and separated in the tire width direction in the center region of the tread portion is adopted (divided carcass structure). As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known.

Japanese Patent Laid-Open No. 11-11109

  However, in a pneumatic tire having a split carcass structure, there is a risk that the rigidity of the sidewall portion is lowered and the steering performance of the tire is deteriorated.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire that can reduce the weight of the tire while ensuring the steering performance of the tire in the configuration having the split carcass structure.

In order to achieve the above object, a pneumatic tire according to the present invention includes a pair of left and right bead cores, a bead filler disposed on the outer side in the tire radial direction of the bead core, and a carcass layer disposed between the pair of left and right bead cores. And a belt layer disposed on the outer side in the tire radial direction of the carcass layer and having at least a pair of belt plies laminated to form a cross-ply structure, and divided in the tire width direction in the tread portion center region A pneumatic tire in which the carcass layer is configured by laminating a separated first carcass ply and a second carcass ply having a single structure spanned between a pair of left and right bead cores, When the narrowest belt width of the plurality of belt plies is referred to as a belt width Wb, A split width D and the belt width Wb is have a relationship of 0.60 ≦ D / Wb ≦ 0.90, both end portions of the second carcass ply located in the bead portion, the strength coefficient of the first carcass ply It is larger than the strength coefficient of the second carcass ply, and the number of cords driven in the first carcass ply is larger than the number of cords driven in the second carcass ply .

In this pneumatic tire, (1) since the first carcass ply has a split structure, the weight of the tire can be reduced as compared with a configuration in which the first carcass ply has a single structure. Further, (2) by arranging the second carcass ply having a single structure, the rigidity of the sidewall portion is ensured as compared with the configuration in which only the first carcass ply having the divided structure is arranged. In addition, (3) the ratio D / Wb between the division width D of the first carcass ply and the belt width Wb is optimized, so that the balance between the weight reduction of the tire and the rigidity of the sidewall portion is improved. Moreover, (4) Since the both ends of the second carcass ply are located in the bead portion, the bead portion is reduced in weight as compared with the configuration in which the second carcass ply is wound back at the bead portion. Accordingly, in the configuration having the split carcass structure, there is an advantage that the weight of the tire can be reduced while ensuring the steering performance of the tire.
Further, this pneumatic tire has an advantage that the weight of the tire can be further reduced by increasing the number of cords (end number) of the first carcass ply while decreasing the number of cords of the second carcass ply. Moreover, there is an advantage that the range of rigidity tuning is expanded.

  In the pneumatic tire according to the present invention, the first carcass ply is wound back while wrapping the bead core and the bead filler.

  In this pneumatic tire, since the sidewall portion is reinforced by the rolled-up portion of the first carcass ply, there is an advantage that the steering performance of the tire is improved.

  In the pneumatic tire according to the present invention, the length t of the winding portion of the first carcass ply on the outer side in the tire radial direction than the bead filler is in the range of t ≧ 10 [mm].

  In this pneumatic tire, the wrap amount (length t) between the portion on the split end portion side and the portion on the winding end portion side of the first carcass ply is optimized. Thereby, there exists an advantage which the rigidity of a sidewall part increases and the steering performance of a tire is ensured appropriately.

  In the pneumatic tire according to the present invention, when the first carcass ply includes a plurality of carcass cords, an inclination angle of the carcass cord with respect to the tire circumferential direction is 70 [deg] or more and 88 [deg] or less. It is in the range.

  In this pneumatic tire, when the carcass cord of the first carcass ply has an appropriate inclination angle, the portion 413 (423) and the winding end 412 (422) on the split end portion 411 (421) side of the first carcass ply are provided. A cross-ply structure is formed at the overlapping portion with the side portion 414 (424). Thereby, there exists an advantage which the rigidity of a sidewall part increases and the steering performance of a tire is ensured appropriately.

  In the pneumatic tire according to the present invention, (1) since the first carcass ply has a split structure, the weight of the tire can be reduced as compared with the configuration in which the first carcass ply has a single structure. Further, (2) by arranging the second carcass ply having a single structure, the rigidity of the sidewall portion is ensured as compared with the configuration in which only the first carcass ply having the divided structure is arranged. In addition, (3) the ratio D / Wb between the division width D of the first carcass ply and the belt width Wb is optimized, so that the balance between the weight reduction of the tire and the rigidity of the sidewall portion is improved. Moreover, (4) Since the both ends of the second carcass ply are located in the bead portion, the bead portion is reduced in weight as compared with the configuration in which the second carcass ply is wound back at the bead portion. Accordingly, in the configuration having the split carcass structure, there is an advantage that the weight of the tire can be reduced while ensuring the steering performance of the tire.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a diamond meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an explanatory view showing a modification of the pneumatic tire shown in FIG. FIG. 3 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

[Pneumatic tire]
The pneumatic tire 1 includes a bead core 2, a bead filler 3, a carcass layer 4, and a belt layer 5 (see FIG. 1). The bead core 2 has an annular structure and is configured as a pair of left and right. The bead filler 3 is disposed on the outer periphery of the bead core 2 in the tire radial direction and reinforces the bead portion of the pneumatic tire 1. The carcass layer 4 is composed of a plurality of carcass plies 41 to 43 in which organic fiber or steel fiber carcass cords are arranged in a comb shape. The carcass layer 4 is bridged in a toroidal shape between the left and right bead cores 2 and 2 to form a tire skeleton. The belt layer 5 includes a plurality of stacked belt plies 51 and 52, and is disposed on the outer periphery in the tire radial direction of the carcass layer 4. For example, in this embodiment, the belt layer 5 includes a pair of belt plies 51 and 52 laminated. Each belt ply 51, 52 intersects the belt cord inclination direction to form a cross ply structure. Further, the belt width (periphery length) of the belt ply 52 on the outer side in the tire radial direction is narrower than the belt width of the belt ply 51 on the inner side in the tire radial direction. In this embodiment, the belt width of the narrower belt ply 52 is Wb (see FIG. 1).

[Divided carcass structure]
In the pneumatic tire 1, the carcass plies 41 and 42 having a divided structure and the carcass ply 43 having a single structure are laminated to form the carcass layer 4 (see FIG. 1). For example, in this embodiment, the first carcass plies 41, 42 that are divided into two in the tire width direction and separated in the center region of the tread portion, and a bridge between the pair of left and right bead cores 2, 2 having a single structure. The carcass layer 4 is configured by laminating the second carcass ply 43 arranged in this manner. Therefore, the carcass layer 4 has a two-layer structure in the sidewall portion, and also has a single-layer structure in the tread portion center region.

  Here, the narrowest width among the plurality of belt plies 51 and 52 constituting the belt layer 5 is referred to as a belt width Wb (see FIG. 1). At this time, the division width D of the first carcass plies 41 and 42 and the belt width Wb have a relationship of 0.60 ≦ D / Wb ≦ 0.90. Further, the first carcass plies 41 and 42 are wound and arranged in the tire width direction while wrapping the bead core 2 and the bead filler 3. On the other hand, both end portions 431 and 432 of the second carcass ply 43 are positioned in the bead portion. Therefore, the first bead portion is lighter than the configuration in which the first carcass ply is wound up at the bead portion and reaches the sidewall portion. As a result, the weight of the tire is reduced while maintaining the rigidity of the sidewall portion.

  In addition, the division width D of the first carcass plies 41 and 42 and the belt width Wb of the belt layer 5 are measured in a state where the tire is mounted on the specified rim and applied with the specified internal pressure and is in an unloaded state. Here, the prescribed rim refers to “applied rim” prescribed in JATMA, “Design Rim” prescribed in TRA, or “Measuring Rim” prescribed in ETRTO. The specified internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in the case of a tire for a passenger car, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

  Further, both end portions 431 and 432 of the second carcass ply 43 may be sufficient as long as they are located at the bead portion, and may have a linear shape in a sectional view in the diamond meridian direction (see FIG. 1). Further, it may be wound up so as not to reach the sidewall portion (not shown).

[effect]
As described above, in the pneumatic tire 1, (1) the first carcass plies 41 and 42 have a split structure, so that the weight of the tire is reduced compared to the configuration in which the first carcass ply has a single structure. Is planned. Further, (2) the second carcass ply 43 having a single structure is arranged, so that the rigidity of the sidewall portion is ensured as compared with the configuration in which only the first carcass ply having a divided structure is arranged. . Further, (3) the ratio D / Wb between the divided width D of the first carcass plies 41 and 42 and the belt width Wb is optimized, so that a balance between weight reduction of the tire and securing of the rigidity of the sidewall portion is good. It becomes. For example, when D / Wb <0.60, there is a problem that the effect of reducing the weight of the tire is small. Further, when 0.90 <D / Wb, there is a problem that the rigidity of the sidewall portion is not sufficiently ensured because the restraining force of the belt layer with respect to the carcass layer is weak. Moreover, (4) Since the both ends of the second carcass ply 43 are located in the bead portion, the bead portion is reduced in weight as compared with the configuration in which the second carcass ply is wound back at the bead portion. Accordingly, in the configuration having the split carcass structure, there is an advantage that the weight of the tire can be reduced while ensuring the steering performance of the tire.

[Modification]
In the pneumatic tire 1, the first carcass plies 41 and 42 are preferably wound back while wrapping the bead core 2 and the bead filler 3 (see FIG. 1). In such a configuration, the sidewall portion is reinforced by the rolled-up portions 414 and 424 of the first carcass plies 41 and 42, so that there is an advantage that the safety performance of the tire is improved.

  Moreover, in said structure, it is preferable that the length t of the winding-up part of the 1st carcass ply 41 (42) in the tire radial direction outer side than the bead filler 3 exists in the range of t> = 10 [mm] (refer FIG. 1). ). In such a configuration, the amount of wrap (length t) between the portion 413 (423) on the split end 411 (421) side and the portion 414 (424) on the winding end 412 (422) side of the first carcass ply 41 (42). ) Is optimized. Thereby, there exists an advantage which the rigidity of a sidewall part increases and the steering performance of a tire is ensured appropriately.

  Further, in the pneumatic tire 1, the inclination angles θ and φ of the carcass cords in the first carcass plies 41 and 42 with respect to the tire circumferential direction are preferably in the range of 70 [deg] to 88 [deg] (FIG. 2). In this configuration, when the carcass cords of the first carcass plies 41 and 42 have an appropriate inclination angle, the portion 413 (423) on the split end 411 (421) side of the first carcass ply 41 (42) and the winding end A cross-ply structure is formed at the overlapping portion with the portion 414 (424) on the part 412 (422) side. Thereby, there exists an advantage which the rigidity of a sidewall part increases and the steering performance of a tire is ensured appropriately.

In the pneumatic tire 1, the strength coefficient of the first carcass plies 41 and 42 is preferably larger than the strength coefficient of the second carcass ply 43. Usually, the carcass width (periphery length) of the second carcass ply 43 is larger than the carcass width of the first carcass plies 41, 42. Therefore, there is an advantage that the weight of the tire can be further reduced by increasing the number of cords driven (end number) of the first carcass plies 41 and 42 while decreasing the number of cords driven of the second carcass ply 43. Moreover, there is an advantage that the range of rigidity tuning is expanded. The strength coefficients of the carcass plies 41 to 43 are defined by the following mathematical formula (1).
Strength coefficient [N / mm · kPa] = Number of cords to be driven [lines / mm] × Strengthening cord strength [N] / Maximum air pressure [kPa] (1)

[performance test]
In this example, (1) a performance test related to driving performance and (2) measurement of tire mass are performed for a plurality of pneumatic tires having different conditions (see FIG. 3). The carcass width shown in FIG. 3 is the peripheral length of the carcass layer.

  (1) In the performance test regarding the steering performance, a pneumatic tire having a tire size of 215 / 45R17 87W was assembled to a rim size of 17 × 7JJ (applicable rim defined by JATMA), and this pneumatic tire had a displacement of 2.0 [L]. Installed on domestic sedan. Further, a maximum internal pressure of 230 [kPa] and a maximum load specified by JATMA are applied to the pneumatic tire. The test vehicle travels on a test course having a flat circuit around 60 [km / h] to 100 [km / h]. Then, the test driver performs sensory evaluation on the steering performance at the time of race change and cornering and the stability at the time of straight traveling. This evaluation is performed by index evaluation using the conventional example as a reference (100), and the larger the value, the better.

  (2) In the measurement of the tire mass, an index evaluation based on the conventional example as a reference (100) is performed based on the measurement result of the tire mass. In this evaluation, the smaller the numerical value, the lighter the tire and the better.

  In a conventional pneumatic tire, a pair of carcass plies having a single structure is laminated to form a carcass layer (not shown). Further, the winding end of one carcass ply is at a position of 50 [mm] in the tire radial direction from the winding position in the bead core, and the winding end of the other carcass ply is 16 in the tire radial direction from the winding position in the bead core. [Mm] position. The carcass width of each carcass ply is set to 470 [mm] and 390 [mm].

  In the pneumatic tire 1 of Invention Example 1 and Invention Example 2, the carcass layer 4 is configured by laminating the first carcass plies 41 and 42 having a split structure and the second carcass ply 43 having a single structure. (See FIG. 1). Further, the ratio D / Wb between the division width D of the first carcass plies 41 and 42 and the belt width Wb is set to D / Wb = 0.90. Further, both end portions 431 and 432 of the second carcass ply 43 are located in the bead portion. Further, the carcass width of the first carcass ply is set to 120 [mm], and the carcass width of the second carcass ply is set to 340 [mm].

  As shown in the test results, it can be seen that the pneumatic tires of Invention Example 1 and Invention Example 2 ensure (or improve) the steering performance of the tire and reduce the weight of the tire. In addition, when Invention Example 1 and Invention Example 2 are compared, the difference in the material (strength) of the first carcass plies 41 and 42 and the material of the second carcass ply 43 improves the steering performance of the tire. I understand that Further, when Invention Example 2 and Invention Example 3 are compared, it can be seen that the steering performance of the tire is improved by optimizing the carcass angle of the carcass layer 4 (the inclination angle θ, φ of the carcass cord).

  As described above, the pneumatic tire according to the present invention is useful in that the weight of the tire can be reduced while securing the tire steering performance in the configuration having the split carcass structure.

It is sectional drawing of the diamond meridian direction which shows the pneumatic tire concerning the Example of this invention. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is a graph which shows the result of the performance test of the pneumatic tire concerning the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead core 3 Bead filler 4 Carcass layer 5 Belt layer 41, 42 First carcass ply 43 Second carcass ply 51, 52 Belt ply 411, 421 Split end part 412, 422 Winding end part

Claims (4)

A pair of left and right bead cores, a bead filler disposed on the outer side in the tire radial direction of the bead core, a carcass layer disposed between the pair of left and right bead cores, and at least a pair of belt plies that are stacked to form a cross-ply structure And a belt layer disposed on the outer side in the tire radial direction of the carcass layer, and divided between the first carcass ply and the pair of left and right bead cores divided in the tire width direction in the center region of the tread portion. A pneumatic tire in which the carcass layer is configured by laminating a second carcass ply having a single structure spanned between,
When the narrowest width of the plurality of belt plies is called a belt width Wb, the division width D of the first carcass ply and the belt width Wb have a relationship of 0.60 ≦ D / Wb ≦ 0.90. And
Both end portions of the second carcass ply located in the bead portion,
The strength coefficient of the first carcass ply is greater than the strength coefficient of the second carcass ply;
A pneumatic tire characterized in that the number of cords driven in the first carcass ply is greater than the number of cords driven in the second carcass ply .   The pneumatic tire according to claim 1, wherein the first carcass ply is wound back while wrapping the bead core and the bead filler.   The pneumatic tire according to claim 2, wherein a length t of the winding portion of the first carcass ply on the outer side in the tire radial direction from the bead filler is in a range of t ≧ 10 [mm].   The inclination angle of the carcass cord with respect to the tire circumferential direction when the first carcass ply is composed of a plurality of carcass cords is in a range of 70 [deg] to 88 [deg]. The pneumatic tire according to any one of the above.

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