JP5680881B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  FIG. 3 is a cross-sectional view showing a part of a conventional pneumatic tire 2. The tire 2 has a substantially bilaterally symmetric shape with a one-dot chain line CL in FIG. 3 as the center. 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, and a belt 12. The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4.

  The bead 8 is located inside the sidewall 6 in the radial direction. The bead 8 includes a core 14 and an apex 16 located on the radially outer side of the core 14. The core 14 is formed by winding a non-stretchable wire. The apex 16 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a carcass ply 18. The carcass ply 18 is folded around the core 14 from the inner side to the outer side in the axial direction.

  The belt 12 is laminated with the carcass 10 on the radially inner side of the tread 4. The belt 12 includes an inner layer 20 and an outer layer 22. The end 24 of the inner layer 20 is located on the inner side in the axial direction of the end 26 of the outer layer 22. The inner layer 20 has a width that is smaller than the width of the outer layer 22.

  Thus, the tire 2 is configured by combining a number of members. Specifications and the like of these members are adjusted, and rigidity, mass, production cost, productivity, and the like are controlled. A study example regarding reduction of production cost is disclosed in Japanese Patent Laid-Open No. 2001-180222. In this tire, the configuration of the belt is reviewed.

JP 2001-180222 A

  From the viewpoint of reducing the production cost, the apex 16 may be removed from the bead 8 as a constituent member of the tire 2. As described above, the carcass ply 18 is folded back by the core 14 of the bead 8. For this reason, a space may be formed when the carcass ply 18 is folded back in the manufacture of the tire 2. In this case, air may remain in the bead 8 of the tire 2. Such a bead 8 affects the quality of the tire 2.

  In order to suppress the formation of the space, the configuration of the core 14 may be reviewed. In this case, the review of the configuration may affect the constant of the camber spring, and may cause excessive rigidity to the tire 2. Excessive rigidity hinders ride comfort.

  In the tire described in the above publication, the belt includes two equal width plies. These plies are arranged such that the respective center positions in the width direction are shifted from the equator plane. In the tire equator region, the plies overlap in the radial direction. In the tire shoulder region, these plies do not overlap. The belt's axially outer portion is more flexible than its inner portion. This belt reduces the constant of the camber spring. This decrease in constant leads to insufficient rigidity in the tire. Insufficient stiffness affects steering stability.

  An object of the present invention is to provide a pneumatic tire that can achieve a reduction in production cost without impairing performance.

  The pneumatic tire according to the present invention includes a pair of beads, a carcass spanned between both beads, and a belt located on the outer side in the radial direction of the carcass. Each of the beads has a core including a wire extending in the circumferential direction. The number of strands of this core is 2 or more. The number of turns of the core is more than three times the number of strands. The belt includes a first ply and a second ply. The center of the width of the first ply is spaced apart from the center of the width of the second ply in the axial direction. When the tire is mounted on a regular rim having a flange, the radially outer position of the wire is radially inward from the radially outer end of the flange.

  Preferably, in the pneumatic tire, the first ply and the second ply overlap in the radial direction. The ratio of the width of the overlapping portion to the width of the belt is 30% or more and 90% or less. Preferably, in this pneumatic tire, the first ply has a width equivalent to the width of the second ply. Preferably, in this pneumatic tire, the ratio of the cross-sectional area of the wire to the cross-sectional area of the bead is 70% or more. Preferably, in the pneumatic tire, the number of strands is two. Preferably, in this pneumatic tire, the number of turns is eight.

  In the pneumatic tire according to the present invention, reduction in production cost can be achieved without impairing the performance.

FIG. 1 is a cross-sectional view illustrating 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. FIG. 3 is a cross-sectional view showing a part of a conventional pneumatic tire.

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

  The tire 28 shown in FIG. 1 includes a tread 30, a sidewall 32, a bead 34, a carcass 36, a belt 38, and an inner liner 40. The tire 28 is a tubeless type. 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 28 has a substantially bilaterally symmetric shape with the one-dot chain line CL in FIG. 1 as the center. This alternate long and short dash line CL represents the equator plane of the tire 28. The tire 28 is attached to a two-wheeled vehicle. In the tire 28, the vicinity of the equator plane is referred to as an equator region.

  The tread 30 is made of a crosslinked rubber having excellent wear resistance. The tread 30 has a shape protruding outward in the radial direction. The tread 30 includes a tread surface 42. The tread surface 42 is in contact with the road surface. A groove 44 is carved on the tread surface 42. The groove 44 forms a tread pattern. The groove 44 may not be cut in the tread 30. In FIG. 1, what is indicated by a point PL is an end of the tread 30 (hereinafter, tread end PL). What is indicated by a point PR is the other end of the tread 30 (hereinafter, tread end PR). In the tire 28, the vicinity of the tread ends PL and PR is referred to as a shoulder region.

  The sidewall 32 extends substantially inward in the radial direction from the tread 30. The sidewall 32 is made of a crosslinked rubber. The sidewall 32 absorbs an impact from the road surface by bending. Further, the sidewall 32 prevents the carcass 36 from being damaged.

  The bead 34 is located substantially inward of the sidewall 32 in the radial direction. The bead 34 includes a core 46. The core 46 has a ring shape.

  The carcass 36 includes a carcass ply 48. The carcass ply 48 is bridged between the beads 34 on both sides, and extends along the inside of the tread 30 and the sidewall 32. The carcass ply 48 is folded around the core 46 from the inner side to the outer side in the axial direction. The end 50 of the carcass ply 48 is located radially outside the bead 34. In the tire 28, the bead 34 is surrounded by the carcass ply 48.

  Although not shown, the carcass ply 48 includes 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 36 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 36 having a bias structure may be employed.

  The belt 38 is located on the radially outer side of the carcass 36. The belt 38 is laminated on the carcass 36. The belt 38 reinforces the carcass 36. The belt 38 includes a first ply 52a and a second ply 52b. Each of the ply 52a and the ply 52b includes 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 direction of inclination of the cord of the ply 52a is opposite to the direction of inclination of the cord of the ply 52b. From the viewpoint of weight reduction, cords made of organic fibers are preferably used. Examples of the organic fiber include polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber. From the viewpoint of having high strength, an aramid fiber is preferable.

  In the tire 28, the ply 52a has a width equivalent to the width of the ply 52b. For this reason, the belt 38 is configured by combining the ply 52a and the ply 52a having the opposite sides. The belt 38 is configured by combining the ply 52b and the ply 52b having the opposite sides. In the tire 28, the belt 38 can be formed by preparing either the ply 52a or the ply 52b at the time of manufacture. Such a belt 38 can contribute to improvement of productivity and reduction of production cost.

  In FIG. 1, what is indicated by a point F1 is the end of the ply 52a. What is indicated by a point F2 is the other end of the ply 52a. What is indicated by a point S1 is the end of the ply 52b. What is indicated by a point S2 is the other end of the ply 52b.

  As illustrated, the end F1 of the ply 52a is located in the vicinity of the tread end PL. The end F1 is located outside the end S1 of the ply 52b in the axial direction. In the tire 28, the end F1 is the end of the belt 38. The end F2 of the ply 52a is located inside the end S2 of the ply 52b in the axial direction. The end F2 is located on the radially inner side of the ply 52b. The end F2 overlaps with the ply 52b in the radial direction.

  The end S1 of the ply 52b is located inside the end F1 of the ply 52a in the axial direction. The end S1 is located on the radially outer side of the ply 52a. The end S1 overlaps the ply 52a in the radial direction. The end S2 of the ply 52b is located in the vicinity of the tread end PR. The end S2 is located outside the end F2 of the ply 52a in the axial direction. In the tire 28, the end S2 is the other end of the belt 38.

  In FIG. 1, the double arrow W1 represents the width of the ply 52a. The width W1 is obtained by measuring the distance from the end F1 to the end F2 along the belt 38. What is indicated by a point P1 is the center of the width W1. In the tire 28, the center P1 of the width W1 of the ply 52a is located between the equator plane and the tread end PL. The ply 52a is disposed such that its center P1 is displaced from the equator plane in the axial direction.

  In FIG. 1, a double-headed arrow W2 represents the width of the ply 52b. The width W2 is obtained by measuring the distance from the end S1 to the end S2 along the belt 38. What is indicated by a point P2 is the center of the width W2. In the tire 28, the center P2 of the width W2 of the ply 52b is located between the equator plane and the tread end PR. The ply 52b is disposed such that its center P2 is displaced from the equator plane in the axial direction.

  In the tire 28, the equator plane is located between the center P1 and the center P2. The center P1 is spaced apart from the center P2 in the axial direction.

  In the tire 28, the ply 52a and the ply 52b overlap in the radial direction in a portion of the belt 38 from the end S1 of the ply 52b to the end F2 of the ply 52a. In the portion from the end F1 of the ply 52a to the end S1 of the ply 52b, the ply 52a does not overlap the ply 52b. In the portion from the end F2 of the ply 52a to the end S2 of the ply 52b, the ply 52b does not overlap the ply 52a. In the tire 28, the ply 52a partially overlaps the ply 52b. The ply 52b partially overlaps the ply 52a. The belt 38 including the ply 52a and the ply 52b is referred to as an offset breaker.

  In the tire 28, the belt 38 is lighter than the belt 12 of the conventional tire 2. This belt 38 can contribute to weight reduction of the tire 28. In the tire 28, the axially outer portion of the belt 38 is more flexible than the axially inner portion. This belt 38 reduces the constant of the camber spring.

  In FIG. 1, a double arrow WA is the width of the belt 38. The width WA is obtained by measuring the distance from the end F1 of the ply 52a to the end S2 of the ply 52b along the belt 38. What is indicated by a double-pointed arrow WB is the width of the portion where the ply 52a and the ply 52b overlap. The wrap width WB is obtained by measuring the distance from the end S1 of the ply 52b to the end F2 of the ply 52a along the belt 38.

  In the tire 28, the ratio of the wrap width WB to the width WA of the belt 38 is appropriately adjusted. From the viewpoint of reducing the weight of the tire 28 and reducing the production cost by reducing the amount of ply used to constitute the belt 38, this ratio is preferably 90% or less, more preferably 83% or less, and 75% or less. Is more preferable, and 67% or less is particularly preferable. From the viewpoint that the belt 38 can contribute to rigidity, the ratio is preferably 30% or more, more preferably 33% or more, further preferably 42% or more, and particularly preferably 50% or more.

  FIG. 2 shows a part of the tire 28 of FIG. FIG. 2 shows a bead 34 portion of the tire 28 located on the right side of FIG. Although not shown, the bead 34 of the tire 28 located on the left side of FIG. 1 has a configuration equivalent to that of the right side bead 34.

  In FIG. 2, the tire 28 is mounted on a regular rim 54 (hereinafter referred to as a rim). The rim 54 is an MT type deep bottom rim defined by the JATMA standard. The rim 54 has a bead sheet 56 extending in the axial direction and a flange 58 extending radially outward from the bead sheet 56.

  As described above, the bead 34 includes the core 46. The tire 28 is not provided with the apex 16 made of a highly hard crosslinked rubber unlike the conventional tire 2. The bead 34 can contribute to weight reduction of the tire 28, improvement of productivity, and reduction of production cost.

  The core 46 includes a wire 60 and a topping rubber 62 extending in the circumferential direction. The wire 60 is non-stretchable. The material of the wire 60 is steel.

  As shown in the drawing, the cross sections of the 16 wires 60 are aligned in two rows and eight columns. In the present specification, the number of rows of cross-sections arranged horizontally is referred to as the number of strands of the core 46. In the tire 28, the number of strands of the core 46 is two. In the present specification, the number of steps of the cross section arranged vertically is the number of turns of the core 46. In the tire 28, the number of turns of the core 46 is eight. In the tire 28, the number of cross sections of the wire 60 included in the core 46 is indicated by the product of the number of strands and the number of turns. In the drawing, the radially outer position of the wire 60 included in the core 46 is indicated by a point PA.

  In the tire 28, the wires 60 included in the core 46 are appropriately aligned and the rigidity is adjusted. This proper alignment can contribute to a reduction in the amount of rubber contained in the beads 34. This reduction in the amount of use can contribute to the weight reduction and production cost reduction of the tire 28. From this viewpoint, the ratio of the cross-sectional area of the wire 60 to the cross-sectional area of the bead 34 (hereinafter referred to as area ratio) is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more. From the viewpoint of durability, the area ratio is preferably 98% or less. The cross-sectional area of the wire 60 is the sum of the cross-sectional areas of the wire 60 included in the cross-section of the core 46. In the tire 28, the bead 34 includes the core 46, and thus the cross-sectional area of the core 46 corresponds to the cross-sectional area of the bead 34. The cross-sectional area of the core 46 includes the cross-sectional area of the topping rubber 62 constituting the core 46. When the bead 34 includes an apex, the cross-sectional area of the bead 34 includes the cross-sectional area of the apex.

  When the tire 28 is attached to the rim 54, the tire 28 abuts against the bead seat 56 and the flange 58. In this mounted state, the radially outer position PA of the wire 60 included in the core 46 is radially inward of an end 64 (hereinafter, radially outer end) located on the radially outer side of the flange 58. The bead 34 including the core 46 can appropriately contribute to rigidity. The tire 28 is excellent in responsiveness during turning.

  In the tire 28, the number of turns is three times or more the number of strands. In other words, the ratio of the number of turns to the number of strands is 3 or more. The bead 34 whose ratio is set to 3 or more improves the rigidity. If this ratio is excessive, the outer position PA of the wire 60 will be radially outward from the radially outer end 64 of the flange 58. In this case, the responsiveness at the time of turning will be inhibited. In the tire 28, the ratio is preferably 5 or less from the viewpoint that the response at the time of turning can be appropriately maintained. This ratio is more preferably 4 from the viewpoint that improvement in rigidity, improvement in productivity, and reduction in production cost can be achieved.

  In the tire 28, the number of strands is preferably 2 or more from the viewpoint of improving the rigidity. The number of strands is particularly preferably 2 from the viewpoint that improvement in rigidity, improvement in productivity, and reduction in production cost can be achieved. From the viewpoint that the bead 34 can effectively contribute to rigidity, the number of turns is preferably 6 or more. From the viewpoint of improving productivity and reducing production cost, the number of turns is preferably 8 or less. From the viewpoint that improvement in rigidity, improvement in productivity, and reduction in production cost can be achieved, the number of turns is particularly preferably 8. As described above, in the tire 28, the number of strands is 2 and the number of turns is 8. The beads 34 of the tire 28 can contribute to improvement in rigidity, improvement in productivity, and reduction in production cost.

  In the tire 28, the bead 34 can contribute to improvement in rigidity. This bead 34 raises the constant of the camber spring. As described above, the belt 38 of the tire 28 reduces the constant of the camber spring. In the tire 28, the rigidity is appropriately maintained by the combination of the bead 34 and the belt 38. The tire 28 has appropriate rigidity. The tire 28 is excellent in handling stability.

  As described above, the belt 38 can contribute to weight reduction. The bead 34 can also contribute to weight reduction. In the tire 28, further weight reduction is achieved by the synergistic effect of the belt 38 and the bead 34.

  As described above, the belt 38 can contribute to an improvement in productivity. The bead 34 can also contribute to the improvement of productivity. In the tire 28, the productivity is further improved by the synergistic effect of the belt 38 and the beads 34.

  As described above, the belt 38 can contribute to a reduction in production cost. The bead 34 can also contribute to a reduction in production cost. In the tire 28, the production cost is further reduced by the synergistic effect of the belt 38 and the beads 34.

  In the present invention, the size and angle of each member of the tire 28 are measured in a state where the tire 28 is incorporated in the regular rim 54 and the tire 28 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 28. In the present specification, the regular rim 54 means a rim defined in a standard on which the tire 28 is based. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims 54. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 28 depends. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  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 tire of Example 1 having the basic configuration shown in FIG. 1 and the specifications shown in Table 1 below was obtained. This tire is a front tire. The size of this tire is “120 / 60ZR17”. The carcass of this tire consists of a carcass ply. The cord included in the carcass ply was a nylon fiber. The fineness of the cord was 1400 dtex. The angle formed by the cord with respect to the equator plane was 90 °. The tire belt includes a first ply and a second ply. A cord made of aramid fibers was used for each of the first ply and the second ply. The fineness of this cord was 1110 dtex. The width W1 of the first ply was 100 mm. The width W2 of the second ply was 100 mm. The belt width WA was 120 mm. The wrap width WB between the first ply and the second ply was 80 mm. Therefore, the ratio (WB / WA) of the width WB to the width WA is 67%. In this tire bead, the number of strands of the core was two. The number of core turns was set to 8. The ratio of the core cross-sectional area to the bead cross-sectional area was 92%. When this tire is mounted on a rim (size = MT3.50 × 17), the bead is Configured.

[Example 2-9]
Tires were obtained in the same manner as in Example 1 except that the ratio (WB / WA) was changed as shown in Table 1 below by changing the width W1, the width W2, and the width WB.

[Comparative Example 1]
Comparative Example 1 is a conventional tire that is commercially available. This comparative example 1 has the basic configuration shown in FIG. This tire is a front tire. The size of this tire is “120 / 60ZR17”. The carcass of this tire consists of a carcass ply. The cord included in the carcass ply was a nylon fiber. The fineness of the cord was 1400 dtex. The angle formed by the cord with respect to the equator plane was 90 °. The tire belt is composed of an inner layer having a width of 115 mm and an outer layer having a width of 130 mm. The center of the inner layer width and the center of the outer layer width overlap in the equatorial plane. The width of the portion where the inner layer and the outer layer overlap in the radial direction is 115 mm. Each of the inner layer and the outer layer includes a cord made of an aramid fiber. The fineness of this cord is 1110 dtex. A bead consists of a core and an apex. This core has 4 strands and 3 turns.

[Comparative Example 2]
A tire was obtained in the same manner as in Example 1 except that the belt configuration was the same as that of Comparative Example 1.

[Comparative Example 3]
A tire was obtained in the same manner as in Example 1 except that the bead configuration was the same as that of Comparative Example 1.

[Running test]
Prototype tires were mounted on the front wheels of a commercial two-wheeled vehicle (4-cycle) with a displacement of 400 cc. The rim was MT3.50 × 17, and the tire air pressure was 225 kPa. A commercially available conventional tire (rear tire) is attached to the rear wheel. The tire size of this rear wheel was set to “160 / 60ZR17”. The rim was MT5.00 × 17, and the air pressure inside the tire was 250 kPa. On a circuit course composed of dry asphalt roads, riders performed running tests on turning performance, responsiveness, limit performance and absorbency. This result is shown as an index with a maximum of 10 points. Larger values indicate better results. The results are shown in Table 1 below.

[Evaluation of mass]
The mass of the tire was measured. The measurement results are shown in the following Table 1 as index values with Comparative Example 1 as 100. The smaller this value, the lighter the weight.

[High-speed durability]
The tire was mounted on the rim (size: MT3.50 × 17) of the test machine, and the prototype tire was filled with gas, and the internal pressure of the prototype tire was 225 kPa. After gas filling, the prototype tire was left for 3 hours in a temperature atmosphere of 20 ° C to 30 ° C. After leaving, the prototype tire was refilled with gas, and the internal pressure was set to the predetermined pressure. The outer diameter Da of the prototype tire was measured in a state where no load was applied. After the measurement, a predetermined load (1500 N) was applied to the prototype tire, and the prototype tire was grounded to the road surface of the test drum. The road surface of this test drum was smooth, and the outer diameter of this test drum was 1.7 m. After touching down, a running test with a testing machine was started. In 20 minutes from the start of the test, the test speed of the prototype tire was set to 230 km / h (start step). The test speed was held at this speed (230 km / h) for 10 minutes (step 1). After holding, the test speed was reached (240 km / h) and held for another 10 minutes (step 2). The test speed was reached (250 km / h) and held for another 10 minutes (step 3). This test speed was reached (260 km / h) and held for another 10 minutes (step 4). The step of increasing the test speed by 10 km / h and holding it for 10 minutes was repeated until the tire broke down. The results are shown in Table 1 below as index values based on the test speed and time at the time when the tire broke down, with Comparative Example 1 taken as 100. Larger values indicate better (higher speed durability).

[durability]
The tire was assembled in a rim (size: MT3.50 × 17), and the tire was filled with air to adjust the internal pressure to 225 kPa. This tire was mounted on a drum-type running test machine, and a longitudinal load of 1.75 kN was applied to the tire. This tire was run on a drum having a radius of 1.7 m at a speed of 80 km / h. The travel distance (maximum 13000 km) until the tire broke was measured. The results are shown in Table 1 below as an index. A larger numerical value is preferable.

[Evaluation of camber spring constant]
A tire was mounted on a rim (MT3.50 × 17) of a tire static evaluation test apparatus. The internal pressure of the tire was 250 kPa. A load-longitudinal deflection curve was obtained when the tire was tilted to a camber angle of 45 ° and compressed, and a constant of the camber spring was obtained from the slope at a reference load of 1.30 kN. This evaluation result is represented by an index value in which the tire of Comparative Example 1 is taken as 100. A larger value indicates higher rigidity.

  As shown in Table 1, the tire of the example has a higher evaluation than the tire of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The method described above can also be applied to pneumatic tires mounted on various vehicles.

2, 28 ... Tire 4, 30 ... Tread 6, 32 ... Sidewall 8, 34 ... Bead 10, 36 ... Carcass 12, 38 ... Belt 14, 46 ... Core 16 ... Apex 18, 48 ... Carcass ply 52a, 52b ... Ply 54 ... Rim 58 ... Flange 60 ... Wire

Claims (6)

A tire comprising a pair of beads, a carcass spanned between both beads, and a belt positioned radially outward of the carcass,
Each of the beads has a core including a wire extending in the circumferential direction,
The number of strands of this core is 2 or more,
The number of turns of this core is more than three times the number of strands,
This belt consists of a first ply and a second ply,
The center of the width of the first ply is spaced apart from the center of the width of the second ply in the axial direction,
The ratio of the cross-sectional area of the wire to the cross-sectional area of the bead is 70% or more and 98% or less,
When this tire is mounted on a regular rim with a flange,
A pneumatic tire in which the radially outer position of the wire is radially inner than the radially outer end of the flange. The first ply and the second ply overlap in the radial direction,
The pneumatic tire according to claim 1, wherein a ratio of a width of the overlapping portion to a width of the belt is 30% or more and 90% or less.   The pneumatic tire according to claim 2, wherein a ratio of a width of the overlapping portion to a width of the belt is 67% or more and 75% or less.   The pneumatic tire according to any one of claims 1 to 3, wherein the first ply has a width equivalent to a width of the second ply. The pneumatic tire according to any one of claims 1 to 4 , wherein the number of strands is two. The pneumatic tire according to claim 5 , wherein the number of turns is eight.

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