JP2009113741A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire 2 having excellent appearance quality without impairing the steering stability and the ride quality. <P>SOLUTION: The pneumatic tire 2 comprises a pair of beads 8, a carcass 10 stretched between the beads 8, and an interposition layer 18 extending in the radial direction along the carcass 10. The bead 8 has a core 24 and an apex 26. The carcass 10 has a first ply 28 and a second ply 30. The interposition layer 18 is located between the first ply 28 and the second ply 30. A part of an inner end 52 of the interposition layer 18 overlaps a portion of a fore end 50 of the apex 26. The ratio of the height in the radial direction from a bead base line to an outer end 48 of the interposition layer 18 to the tire height is ≥0.25 and ≤0.8. The overlapping length of the interposition layer 18 and the apex 26 is ≥5 mm and ≤25 mm. The thickness of the interposition layer 18 is ≥0.5 mm and ≤2.5 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire.

  The lateral rigidity of the tire can contribute to steering stability. The longitudinal rigidity of the tire affects the ride comfort. The balance between the lateral stiffness and the longitudinal stiffness is adjusted by examining the specifications and combinations of the rubber members constituting the tire. This balance adjustment achieves both steering stability and ride comfort.

Japanese Laid-Open Patent Publication No. 7-186609 discloses a tire in which the weight of the tire is reduced and the rolling resistance is reduced while maintaining steering stability and riding comfort. In this tire, a protective rubber layer is provided between the carcass and the inner liner. This protective rubber layer contains short fibers oriented in the circumferential direction.
JP-A-7-186609

  In some cases, an intervening layer is provided between the carcass and the apex of the bead in a tire formed of a ply in which the carcass is folded at the core of the bead from the viewpoint of handling stability and riding comfort. In this case, a step is formed by the contact between the ply of the portion folded back by the core and extending outward in the radial direction, and the intervening layer. The presence of this step can induce bear generation. This bear deteriorates the appearance quality of the tire and affects the productivity of the tire.

  An object of the present invention is to provide a tire having excellent appearance quality without impairing steering stability and riding comfort.

  The pneumatic tire according to the present invention includes a pair of beads, a carcass bridged between both beads, and an intervening layer extending in the radial direction along the carcass. The bead includes a core and an apex that extends radially outward from the core. The carcass includes a first ply and a second ply. The intervening layer is located between the first ply and the second ply. The inner end portion of the intervening layer and the apex tip portion overlap each other. The ratio of the height in the radial direction from the bead base line to the outer end of the intervening layer to the tire height is 0.25 or more and 0.8 or less. The length of the overlap between the intervening layer and the apex is 5 mm or more and 25 mm or less. The thickness of this intervening layer is 0.5 mm or more and 2.5 mm or less.

  Preferably, in the tire, the first ply is folded at the core. The second ply is folded at this core. The ratio of the height in the radial direction from the bead base line to the end of the first ply to the tire height is not less than 0.3 and not more than 0.7. The ratio of the height in the radial direction from the bead base line to the end of the second ply to the tire height is 0.1 or more and 0.6 or less. The ratio of the height in the radial direction from the bead base line to the tip of the apex to the tire height is 0.05 to 0.35.

  In this tire, the intervening layer can appropriately contribute to the rigidity of the tire. This intervening layer can increase the lateral rigidity while suppressing an increase in the longitudinal rigidity. This tire is excellent in ride comfort and handling stability. Since the inner end portion of the intervening layer and the apex tip portion overlap each other, a portion having rigidity specific to the tire is not formed. This tire is excellent in ride comfort and handling stability. Since the intervening layer is located between the first ply and the second ply, the intervening layer does not contact the end portion of the first ply. This intervening layer does not contact the end portion of the second ply. In this tire, the occurrence of bears can be suppressed. This tire is excellent in appearance quality.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view showing a part of a pneumatic tire 2 according to an embodiment of the present invention. In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The tire 2 has a substantially left-right symmetric shape centered on a one-dot chain line CL in FIG. This alternate long and short dash line CL represents the equator plane of the tire 2. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, an inner liner 14, a chafer 16, and an intervening layer 18. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  The tread 4 is made of a crosslinked rubber having excellent wear resistance. The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 20. The tread surface 20 is in contact with the road surface. A groove 22 is carved in the tread surface 20. The groove 22 forms a tread pattern. The groove 22 may not be cut in the tread 4.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Furthermore, the sidewall 6 prevents the carcass 10 from being damaged.

  The bead 8 is located substantially inward of the sidewall 6 in the radial direction. The bead 8 includes a core 24 and an apex 26 that extends radially outward from the core 24. The core 24 has a ring shape. The core 24 includes a plurality of non-stretchable wires (typically steel wires). The apex 26 is tapered outward in the radial direction. The apex 26 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a first ply 28 and a second ply 30. The first ply 28 and the second ply 30 are bridged between the beads 8 on both sides, and extend along the inside of the tread 4 and the sidewall 6.

  Although not shown, the first ply 28 and the second ply 30 are composed of a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass 10 having a bias structure may be employed.

  In the tire 2, the first ply 28 is folded around the core 24 from the inner side to the outer side in the axial direction. The first ply 28 includes a first main portion 32 that extends from the equator plane toward the core 24, and a first folded portion 34 that is folded back by the core 24 and extends radially outward. . The first main portion 32 is located outside the inner liner 14. The radially inner portion of the first main portion 32 is located on the inner side in the axial direction of the apex 26. The first folded portion 34 is located outside the first main portion 32 in the axial direction. The first folded portion 34 is located outside the apex 26 in the axial direction. An end 36 of the first folded portion 34 is an end of the first ply 28.

  In the tire 2, the second ply 30 is folded around the core 24 from the inner side in the axial direction to the outer side. The second ply 30 includes a second main portion 38 that extends from the equator plane toward the core 24, and a second folded portion 40 that is folded back by the core 24 and extends radially outward. . The second main portion 38 is located outside the first main portion 32. The radially inner portion of the second main portion 38 is located on the axially inner side of the apex 26. This portion is located between the first main portion 32 and the apex 26. The second folded portion 40 is located outside the second main portion 38 in the axial direction. The second folded portion 40 is located outside the apex 26 in the axial direction. The second folded portion 40 is located between the apex 26 and the first folded portion 34. An end 42 of the second folded portion 40 is an end of the second ply 30. In the tire 2, the end 42 of the second folded portion 40 is located on the radially inner side of the end 36 of the first folded portion 34. The end 42 of the second folded portion 40 may be located radially outside the end 36 of the first folded portion 34.

  The belt 12 is located on the radially outer side of the carcass 10. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes an inner layer 44 and an outer layer 46. Although not shown, each of the inner layer 44 and the outer layer 46 is composed of a plurality of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is not less than 10 ° and not more than 35 °. The cord inclination direction of the inner layer 44 is opposite to the cord inclination direction of the outer layer 46. The inner layer 44 and the outer layer 46 constitute a so-called cross-ply structure. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The inner liner 14 is joined to the inner peripheral surface of the carcass 10. The inner liner 14 is made of a crosslinked rubber. The inner liner 14 is made of rubber having excellent air shielding properties. The inner liner 14 plays a role of maintaining the internal pressure of the tire 2.

  The chafer 16 is located in the vicinity of the bead 8. When the tire 2 is incorporated into the rim, the chafer 16 comes into contact with the rim. By this contact, the vicinity of the bead 8 is protected. The chafer 16 is usually made of a cloth and a rubber impregnated in the cloth. A chafer 16 made of a single rubber may be used.

  The intervening layer 18 is located inside the sidewall 6 in the axial direction. The intervening layer 18 extends in the radial direction along the carcass 10. An end 48 (outer end) located on the radially outer side of the intervening layer 18 is located on the radially outer side of the tip 50 of the apex 26. An end 52 (inner end) located on the radially inner side of the intervening layer 18 is located on the radially inner side of the tip 50 of the apex 26.

  The intervening layer 18 is made of a crosslinked rubber. The intervening layer 18 can contribute to the rigidity of the tire 2. As will be described later, the intervening layer 18 can adjust the balance between the longitudinal rigidity and the lateral rigidity of the tire 2 by adjusting the thickness, the length, and the like. In the tire 2, the intervening layer 18 can increase the lateral rigidity while suppressing the increase in the longitudinal rigidity. The tire 2 is excellent in ride comfort and handling stability.

  In the tire 2, the intervening layer 18 is located on the outer side in the axial direction of the first main portion 32. The intervening layer 18 is located on the inner side in the axial direction of the second main portion 38. The intervening layer 18 is located between the first main portion 32 and the second main portion 38. In other words, the intervening layer 18 is located between the first ply 28 and the second ply 30. For this reason, the intervening layer 18 does not come into contact with the first folded portion 34. In other words, the intervening layer 18 does not come into contact with the end 36 portion of the first ply 28. In the tire 2, the intervening layer 18 does not come into contact with the second folded portion 40. In other words, the intervening layer 18 does not come into contact with the end 42 portion of the second ply 30. In the tire 2, the outer end 48 of the intervening layer 18 and the end 36 of the first ply 28 directly overlap each other, or the outer end 48 of the intervening layer 18 and the end 42 of the second ply 30 overlap directly. Absent. In the tire 2, the generation of bears can be suppressed. The tire 2 is excellent in appearance quality.

  As described above, in the tire 2, the inner end 52 of the intervening layer 18 is located on the radially inner side of the tip 50 of the apex 26. In the tire 2, the inner end 52 portion of the intervening layer 18 and the tip 50 portion of the apex 26 overlap. In the tire 2, a portion having unique rigidity is not formed in the portion from the bead 8 to the sidewall 6. The tire 2 can be excellent in ride comfort and handling stability.

  In the tire 2, the outer end 48 of the intervening layer 18, the end 36 of the first folded portion 34, and the end 42 of the second folded portion 40 are dispersed in the radial direction. A portion having specific rigidity is not formed in the portion of the sidewall 6 of the tire 2. The tire 2 is excellent in ride comfort and handling stability. As shown in the figure, in the tire 2, the outer end 48 of the intervening layer 18 is located radially inward of the end 36 of the first folded portion 34, and the radial direction of the end 42 of the second folded portion 40. Located on the outside. The outer end 48 is located between the end 36 of the first folded portion 34 and the end 42 of the second folded portion 40. The outer end 48 may be positioned on the radially outer side of the end 36 of the first folded portion 34 and the end 42 of the second folded portion 40.

  FIG. 2 is an enlarged cross-sectional view showing a part of the tire 2 of FIG. In FIG. 2, a double arrow line TA represents the thickness of the intervening layer 18. The double arrow line LA represents the length of the portion where the intervening layer 18 and the apex 26 overlap.

  In the tire 2, the thickness TA is not less than 0.5 mm and not more than 2.5 mm. By setting the thickness TA to 0.5 mm or more, the intervening layer 18 can effectively contribute to the balance adjustment between the longitudinal rigidity and the lateral rigidity of the tire 2. The tire 2 is excellent in handling stability and ride comfort. In this respect, the thickness TA is more preferably 1 mm or more. By setting the thickness TA to 2.5 mm or less, excessive rigidity of the tire 2 can be suppressed. In the tire 2, the riding comfort is not impaired. In this respect, the thickness TA is more preferably 2 mm or less.

  In the tire 2, the length LA is not less than 5 mm and not more than 25 mm. By setting the length LA to be 5 mm or more, it is possible to suppress excessive rigidity of the overlapping portion. Since a portion having a specific rigidity is not formed in a portion from the bead 8 to the sidewall 6 of the tire 2, the riding comfort of the tire 2 is not impaired. In this respect, the length LA is more preferably 10 mm or more. By setting the length LA to 25 mm or less, the rigidity of the tire 2 can be appropriately maintained. The riding comfort and steering stability of the tire 2 are not impaired. From this viewpoint, the length LA is more preferably 20 mm or less.

  In FIG. 1, a solid line BBL is a bead base line. This bead base line is a line that defines the rim diameter (see JATMA) of the rim on which the tire 2 is mounted. A double arrow line H0 represents the height in the radial direction from the bead base line to the equator plane. The radial height H0 is the tire 2 height. A double arrow line HA represents the height in the radial direction from the bead base line to the outer end 48 of the intervening layer 18. A double arrow line H <b> 1 represents the height in the radial direction from the bead base line to the end 36 of the first folded portion 34. A double arrow line H <b> 2 represents the radial height from the bead base line to the end 42 of the second folded portion 40. A double arrow line H <b> 3 represents a radial height from the bead base line to the tip 50 of the apex 26.

  In the tire 2, the ratio of the radial height HA to the radial height H0 is 0.25 or more and 0.8 or less. By setting this ratio to be 0.25 or more, the intervening layer 18 can effectively contribute to the balance adjustment between the longitudinal rigidity and the lateral rigidity of the tire 2. The tire 2 is excellent in handling stability and ride comfort. In this respect, the ratio is more preferably 0.45 or more. By setting this ratio to 0.8 or less, excessive rigidity of the tire 2 can be suppressed. In the tire 2, the riding comfort is not impaired. In this respect, the ratio is more preferably equal to or less than 0.7.

  In the tire 2, the ratio of the radial height H1 to the radial height H0 is preferably 0.3 or more and 0.7 or less. By setting this ratio to 0.3 or more, the rigidity of the tire 2 can be appropriately maintained. In the tire 2, excellent riding comfort and steering stability can be maintained. From this viewpoint, the ratio is more preferably 0.4 or more. By setting this ratio to 0.7 or less, excessive rigidity of the tire 2 can be suppressed. In the tire 2, the riding comfort is not impaired. In this respect, the ratio is more preferably equal to or less than 0.6.

  In the tire 2, the ratio of the radial height H2 to the radial height H0 is preferably 0.1 or more and 0.6 or less. By setting this ratio to 0.1 or more, the rigidity of the tire 2 can be appropriately maintained. In the tire 2, excellent riding comfort and steering stability can be maintained. In this respect, the ratio is more preferably equal to or greater than 0.2. By setting this ratio to 0.6 or less, excessive rigidity of the tire 2 can be suppressed. In the tire 2, the riding comfort is not impaired. In this respect, the ratio is more preferably equal to or less than 0.5.

  In the tire 2, the ratio of the radial height H3 to the radial height H0 is preferably 0.05 or more and 0.35 or less. By setting this ratio to 0.05 or more, the rigidity of the tire 2 can be appropriately maintained. In the tire 2, excellent riding comfort and steering stability can be maintained. In this respect, the ratio is more preferably equal to or greater than 0.1. By setting this ratio to 0.35 or less, excessive rigidity of the tire 2 can be suppressed. In the tire 2, the riding comfort is not impaired. In this respect, the ratio is more preferably equal to or less than 0.3.

  In the tire 2, the hardness of the intervening layer 18 is preferably 75 or more and 98 or less. By setting the hardness to 75 or more, the intervening layer 18 can effectively contribute to the balance adjustment between the longitudinal rigidity and the lateral rigidity of the tire 2. The tire 2 is excellent in handling stability and ride comfort. In this respect, the hardness is more preferably equal to or greater than 80. By setting the hardness to 98 or less, excessive rigidity of the tire 2 can be suppressed. In the tire 2, the riding comfort is not impaired. From this viewpoint, the hardness is more preferably 90 or less.

  In the present invention, the hardness is measured by a type A durometer according to JIS-K6253. This hardness is measured under conditions where the temperature is 23 ° C. For this measurement, a test piece formed by crosslinking the rubber composition constituting the intervening layer 18 is used. This test piece is obtained by holding the rubber composition in a mold having a temperature of 160 ° C. for 10 minutes.

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in the JATMA standard, “maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “INFLATION PRESSURE” in the ETRTO standard are normal internal pressures. For convenience, the internal pressure of the passenger car tire 2 is set to 180 kPa.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A pneumatic tire of Example 1 having the basic configuration shown in FIG. 1 and having the specifications shown in Table 1 below was obtained. The tire size is 225 / 50R17. The intervening layer is sandwiched between the first main portion of the first ply and the second main portion of the second ply. The thickness TA of this intervening layer is 1.0 mm. The length LA of the portion where the intervening layer and the apex overlap is 10 mm. The ratio HA / H0 of the radial height HA from the bead base line to the outer end of the intervening layer with respect to the tire height H0 is 0.45. The ratio H1 / H0 of the radial height H1 from the bead base line to the end of the first folded portion with respect to the tire height H0 is 0.5. The ratio H2 / H0 of the radial height H2 from the bead base line to the end of the second folded portion with respect to the tire height H0 is 0.35. The ratio H3 / H0 of the radial height H3 from the bead base line to the tip of the apex with respect to the tire height H0 is 0.2.

[Comparative Example 4 and Examples 4 to 5]
Tires were obtained in the same manner as in Example 1 except that the thickness TA was as shown in Tables 1 and 2 below.

[Comparative Examples 3 and 5 and Examples 3 and 6]
Tires were obtained in the same manner as in Example 1 except that the length LA was as shown in Tables 1 and 2 below.

[Comparative Examples 2 and 6 and Examples 2 and 7 to 9]
Tires were obtained in the same manner as in Example 1 except that the ratio HA / H0 was as shown in Tables 1 and 2 below.

[Examples 10 to 17]
Tires were obtained in the same manner as in Example 1 except that the ratios HA / H0, H1 / H0, H2 / H0, and H3 / H0 were as shown in Tables 2 and 3 below.

[Comparative Example 1]
A tire was obtained in the same manner as in Example 1 except that no intervening layer was provided.

[Comparative Example 7]
Except that the intervening layer is disposed outside the second main portion in the axial direction and the inner end portion of the intervening layer is sandwiched between the second main portion and the apex tip portion, the same as in the first embodiment. Got a tire. In this tire, the outer end portion of the intervening layer is in direct contact with the end portion of the first folded portion and the end portion of the second folded portion.

[Sensory evaluation of tires]
The prototype tire was mounted on a passenger car (FR car) having a displacement of 2000 cc. The internal pressure of this tire was 210 kPa. The size of the wheel is 17 × 6.5J. This passenger car was subjected to a running test on an asphalt road surface, and a driver's sensory evaluation was performed on handling stability and riding comfort. This result is expressed as an index value with Comparative Example 1 as 100. Larger values indicate better results. The results are shown in Table 1, Table 2 and Table 3 below.

[Appearance evaluation]
The appearance quality of the prototype tire was visually observed to confirm the presence or absence of bears. The results are shown in Table 1, Table 2, and Table 3 below, where A is a case where no bear is observed and B is a bear occurrence.

  As shown in Tables 1, 2 and 3, the tires of the examples are excellent in handling stability, riding comfort and appearance quality. From this evaluation result, the superiority of the present invention is clear.

  The tire according to the present invention can be mounted on various vehicles.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the tire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Tire 4 ... Tread 6 ... Side wall 8 ... Bead 10 ... Carcass 12 ... Belt 14 ... Inner liner 16 ... Chafer 18 ... Intervening layer 20 ... Tread surface 22 ... Groove 24 ... Core 26 ... Apex 28 ... First ply 30 ... Second ply 32 ... First main part 34 ... First turn Part 38 ... second main part 40 ... second folded part 44 ... inner layer 46 ... outer layer

Claims (2)

A pair of beads, a carcass spanned between both beads, and an intervening layer extending radially along the carcass,
The bead includes a core and an apex extending radially outward from the core,
This carcass has a first ply and a second ply,
The intervening layer is located between the first ply and the second ply;
The inner end portion of this intervening layer and the apex end portion of this apex overlap.
The ratio of the height in the radial direction from the bead baseline to the outer end of the intervening layer to the tire height is 0.25 or more and 0.8 or less,
The overlap length between this intervening layer and this apex is 5 mm or more and 25 mm or less,
The pneumatic tire whose thickness of this intervening layer is 0.5 mm or more and 2.5 mm or less. The first ply is folded at the core;
The second ply is folded at this core,
The ratio of the height in the radial direction from the bead baseline to the end of the first ply to the tire height is 0.3 or more and 0.7 or less,
The ratio of the radial height from the bead baseline to the end of the second ply to the tire height is 0.1 or more and 0.6 or less,
The tire according to claim 1, wherein a ratio of a height in a radial direction from a bead base line to a tip of the apex with respect to the tire height is 0.05 or more and 0.35 or less.

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