JP2015155260A - pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing weight increase and improving stability.

SOLUTION: A pneumatic tire 1 comprises: a sidewall part 3 extending in a tire radial direction inside from a tread part 2; and a bead part 4 in which a bead core 10 is embedded. The pneumatic tire 1 further comprises a carcass 11 formed of a first side carcass 12A extending in a space between one side end part of a belt layer 6 and the bead core 10, and a second side carcass 12B extending in a space between the other side end part of the belt layer 6 and the bead core 10. The first side carcass 12A and second side carcass 12B are separated each other and the respective side carcass has a body part 14 extending from an outer end 13 of the tire radial direction toward an inner end 18 of the tire radial direction continuously, a folding part 15 on the belt side continuous to the outer end 13 and terminating by being folded, and a folding part 19 on the bead side continuous to the inner end 18 and terminating by being folded.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to a pneumatic tire capable of improving steering stability performance while suppressing an increase in mass.

  Generally, a pneumatic tire has a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both end portions thereof, and a bead portion provided at an inner end thereof, and a bead core embedded in the bead portion. It has a carcass that stretches across the toroid.

  On the other hand, recent pneumatic tires are required to improve steering stability performance while suppressing an increase in mass. For example, Patent Literature 1 proposes a pneumatic tire including so-called hollow carcasses separated from each other in a tread portion. In such a pneumatic tire, the carcass cord is reduced in the tread portion, thereby reducing the mass.

JP 2008-279820 A

  However, in the conventional pneumatic tire, the rigidity of the tread portion is greatly reduced by the hollow carcass. Further, in the conventional pneumatic tire, when the load is applied, the distance between the carcass cords tends to be large in the vicinity of both ends of the tread portion of the hollow carcass. For this reason, there is a problem in that the rigidity at both ends of the tread portion is lowered and the steering stability performance is deteriorated.

  The present invention has been made in view of the above problems, and has as its main object to provide a pneumatic tire that can improve steering stability performance while suppressing an increase in mass.

  Of the present invention, the invention according to claim 1 includes a tread portion in which a belt layer is disposed, a pair of sidewall portions extending inward in the tire radial direction from both end portions of the tread portion, and the respective sidewall portions. A pneumatic tire having a bead portion provided at an inner end of the tire and having a bead core embedded therein, and extending between one end portion of the belt layer and the bead core on one side of the tire equator A carcass comprising a first side carcass and a second side carcass extending between the other end of the belt layer and the bead core on the other side of the tire equator; The carcass and the second side carcass are separated from each other in the tread portion, and each side carcass is positioned inward in the tire radial direction of the belt layer. A main body portion extending continuously from the outer end to the inner end in the tire radial direction extending to the bead core; a belt-side turn-up portion that continues to the outer end of the main body portion and is turned back to the outer side in the tire axial direction; A bead-side turn-back portion that continues to the inner end of the main body and is turned back outward in the tire radial direction.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the folded portion on the belt side is provided between the main body portion and the belt layer.

  According to a third aspect of the present invention, in the tire meridian cross section including the tire rotation axis, the overlap length Li between the side carcass and the belt layer is 5 to 30 mm. The air according to the first or second aspect This is a tire.

  According to a fourth aspect of the present invention, the outer end in the tire axial direction of the folded portion on the belt side is located on the outer side in the tire axial direction with respect to the outer end of the belt layer. The pneumatic tire described in 1.

  The invention according to claim 5 is the pneumatic tire according to claim 4, wherein the length Lo from the outer end of the belt layer to the outer end in the tire axial direction of the folded portion on the belt side is 10 to 40 mm. is there.

  According to a sixth aspect of the present invention, in each side carcass, a reinforcing rubber layer having a complex elastic modulus of 4 to 10 MPa is disposed between the main body portion and the folded portion on the belt side. It is a pneumatic tire in any one of thru | or 5.

  In the invention according to claim 7, an outer end in the tire axial direction of the reinforcing rubber layer is located on an inner side in the tire axial direction of an outer end in the tire axial direction of the folded portion on the belt side, and the reinforcing rubber layer The pneumatic tire according to claim 6, wherein the length from the outer end in the tire axial direction to the outer end in the tire axial direction of the folded portion on the belt side is 2 to 10 mm.

  The pneumatic tire of the present invention includes a first side carcass extending between one end of the belt layer and the bead core on one side of the tire equator, and the belt layer on the other side of the tire equator. Of the second side carcass extending between the bead core and the second side carcass, wherein the first side carcass and the second side carcass are in the tread portion, The main body portions that are separated from each other and extend continuously from the outer end located inward in the tire radial direction of the belt layer to the inner end in the tire radial direction reaching the bead core, and the main body portion A belt-side folded portion that is connected to the outer end of the tire and is folded outwardly in the tire axial direction and is connected to the inner end of the main body and is folded outward in the tire radial direction. It has been and a folded portion of the bead-side terminating.

  Since the pneumatic tire of the present invention has a so-called hollow carcass in which the first side carcass and the second side carcass are separated from each other, for example, compared with a pneumatic tire having a toroidal carcass Reduced weight. Therefore, in the pneumatic tire of the present invention, an increase in mass can be suppressed.

  In the pneumatic tire of the present invention, the rigidity of both end portions of the tread portion is enhanced by the main body portion of each side carcass and the folded portion on the belt side. Furthermore, since the main body portion and the folded portion overlap each other, the distance between the carcass cords of each side carcass can be maintained when a load is applied. Therefore, in the pneumatic tire of the present invention, the rigidity of the tread portion is improved and the steering stability performance can be improved.

It is a tire meridian sectional view of a pneumatic tire of an embodiment of the present invention. FIG. 2 is a developed plan view of an internal state of a tread portion in FIG. 1. FIG. 2 is an enlarged view of the vicinity of a tread grounding end in FIG. 1. It is an expansion | deployment top view of the internal state of the tread part of other embodiment. It is an enlarged view near the tread grounding end of other embodiments.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, a pneumatic tire of the present embodiment (hereinafter simply referred to as “tire”) in a normal state in which a normal rim (not shown) is assembled with a rim, is filled with a normal internal pressure, and is unloaded may be described. 1) A tire meridian cross-sectional view including the tire rotation axis is shown. In the present embodiment, a tire for a passenger car is shown.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA and “Design Rim” for TRA. For ETRTO, use "Measuring Rim".

  The “regular internal pressure” is an air pressure defined by each standard for each tire in a standard system including a standard on which the tire is based. The maximum value listed in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  In this specification, when there is no notice in particular, the dimension of each part of the tire 1 shall be a value in a normal state.

  As shown in FIG. 1, the tire 1 of the present embodiment includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and an inner portion of each sidewall portion 3. And a bead portion 4 provided at one end. Further, the tire 1 has a tread grounding width TW that is a distance between the tread grounding ends Te and Te of the tread portion 2.

  The “tread grounding end” is the outermost end in the tire axial direction of the tread grounding surface when a normal load is applied to the tire in the normal state and grounded on a flat surface with a camber angle of 0 °.

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. For example, “maximum load capacity” is indicated for JATMA, and is indicated for TRA. The maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

  FIG. 2 shows a plan development view of the internal structure of the tread portion 2. As shown in FIG. 1 or FIG. 2, the tread portion 2 is provided with a belt layer 6 arranged over the entire region in the tire axial direction.

  The belt layer 6 is formed of, for example, at least one belt ply 6A and 6B in which steel belt cords 8 are arranged at an angle of 10 to 35 degrees with respect to the tire equator C, and in this embodiment, two inner and outer belt plies. ing. In the belt ply 6A, the outer ends 6e, 6e in the tire axial direction are positioned outward in the tire axial direction from the outer ends in the tire axial direction of the belt ply 6B. Therefore, the outer end 6e of the belt ply 6A is the outer end of the belt layer 6.

  Such belt plies 6A and 6B are desirably arranged in different directions so that the belt cords 8 cross each other in order to increase the rigidity of the tread portion 2. For the belt cords 8 of the belt plies 6A and 6B, for example, highly elastic organic fiber cords such as rayon and aromatic polyamide can be used as necessary.

  In addition, it is desirable that the tread portion 2 is provided with a band layer 9 that covers at least the outer ends 6e and 6e of the belt ply 6B on the outer side in the radial direction of the belt layer 6, for example. The band layer 9 can suppress lifting of the belt layer 6 associated with high-speed running and improve the high-speed running performance of the tire 1. The band layer 9 is preferably arranged, for example, with low-elasticity organic fiber cords at a small angle of 0 to 5 degrees with respect to the tire equator C.

  As shown in FIG. 1, the bead portion 4 includes a ring-shaped bead core 10 including a steel wire, and a reinforcing bead that tapers outward from the outer surface in the tire radial direction of the bead core 10 in the tire radial direction. An apex rubber 20 is provided. The bead apex rubber 20 is preferably made of hard rubber having a rubber hardness of about 70 to 90 °, for example. In addition, rubber hardness is durometer A hardness measured in a 23 degreeC environment by durometer type A based on JIS-K6253.

  The tire 1 includes, on one side of the tire equator C, the first side carcass 12A extending between the outer end 6e on one side of the belt layer 6 and the bead core 10, and the belt layer 6 on the other side of the tire equator C. The carcass 11 including the outer end 6e on the other side and the second side carcass 12B extending between the bead core 10 is provided.

  The carcass 11 is formed in a so-called hollow shape in the tread portion 2 in which the first side carcass 12A and the second side carcass 12B are separated from each other. Such a carcass 11 can suitably reduce the weight of the tire 1.

  In the tread portion 2, the separation distance W1 between the first side carcass 12A and the second side carcass 12B is preferably 60 to 80% of the tread ground contact width TW, for example. If the separation distance W1 is less than 60% of the tread ground contact width TW, it may be difficult to reduce the weight of the tire 1. On the contrary, when the separation distance W1 is larger than 80% of the tread contact width TW, the rigidity of the tread portion 2 is likely to be lowered, and the steering stability performance of the tire 1 may not be improved. From such a viewpoint, the separation distance W1 is more preferably 65 to 75% of the tread ground contact width TW.

  Each of the side carcass 12A, 12B is formed of one or more carcass plies in which a plurality of carcass cords 16 are arranged at an angle of 70 to 90 ° with respect to the tire circumferential direction, for example, one carcass ply in this embodiment. The carcass ply is preferably formed, for example, by cutting one carcass ply prepared for non-hollow shape into two, from the viewpoint of ease of formation, and one cut ply is Desirably, the first side carcass 12A is used, and the other ply is used for the second side carcass 12B.

  The carcass cords 16 are arranged in parallel at a preset interval L1. For the carcass cord 16, for example, a well-known organic fiber cord such as nylon, polyester, rayon or the like is preferably used.

  The first side carcass 12A and the second side carcass 12B have the same configuration in this embodiment. For this reason, only the first side carcass 12A on one side will be described in detail below, and the detailed description on the second side carcass 12B on the other side will be omitted.

  The first side carcass 12 </ b> A (hereinafter sometimes simply referred to as “side carcass 12”) is an inner side in the tire radial direction from the outer end 13 positioned inward in the tire radial direction of the belt layer 6 to the bead core 10. A main body portion 14 extending continuously to the end 18, a belt-side turn-back portion 15 that is connected to the outer end 13 of the main body portion 14, is turned back outward in the tire axial direction, and is connected to an inner end 18 of the main body portion 14. And a bead-side folded portion 19 that is folded outwardly in the tire radial direction and terminates.

  As described above, the tire 1 of the present embodiment is suitably reduced in weight by the hollow carcass 11. For this reason, an increase in mass due to the folded portion 15 on the belt side of the side carcass 12 can be suppressed.

  Further, in the tire 1 of the present embodiment, the rigidity of both end portions of the tread portion 2 is enhanced by the main body portion 14 of the side carcass 12 and the folded portion 15 on the belt side. In addition, since the carcass cord 16 overlaps or intersects when the main body portion 14 and the turn-back portion 15 overlap, the distance L1 between the carcass cords 16 of the side carcass 12 can be maintained when a load is applied, and the tread portion 2 The rigidity of both ends is maintained. Therefore, in the tire 1, the rigidity of the tread portion 2 is greatly improved, and the steering stability performance can be improved.

  The tire 1 is desirably provided with, for example, an inner liner rubber 21 that forms a lumen surface. For example, the inner liner rubber 21 can suppress the side carcass 12 from being peeled from the outer end 13 side on the belt side toward the inner cavity side of the tire 1.

  FIG. 3 shows an enlarged view of the vicinity of the tread grounding end Te on one side of FIG. As shown in FIG. 3, the folded portion 15 on the belt side of the side carcass 12 is desirably provided between the main body portion 14 and the belt layer 6, for example.

  In the tire meridian section, the overlap length Li in the tire axial direction between the side carcass 12 and the belt layer 6 is preferably, for example, 5 to 30 mm. When the overlap length Li is less than 5 mm, the rigidity of both end portions of the tread portion 2 cannot be sufficiently secured, and the steering stability performance of the tire 1 may not be improved. On the other hand, when the overlap length Li is larger than 30 mm, the mass of the side carcass 12 is increased, and the rolling performance of the tire 1 may be deteriorated. From such a viewpoint, the overlap length Li is preferably 10 to 25 mm.

  The outer end 22 in the tire axial direction of the folded portion 15 on the belt side of the side carcass 12 is located on the outer side in the tire axial direction with respect to the outer end 6 e of the belt layer 6. The first protrusion length Lo from the outer end 6e of the belt layer 6 to the outer end 22 in the tire axial direction of the folded portion 15 on the belt side is preferably, for example, 10 to 40 mm. When the first protrusion length Lo is less than 10 mm, it is difficult to improve the rigidity on the tread ground contact Te side, and it is difficult to improve the steering stability performance of the tire 1. On the contrary, when the first protrusion length Lo is larger than 40 mm, not only the mass of the side carcass 12 is increased, but also the rigidity of the sidewall portion 3 is excessively increased, and the sidewall portion 3 having a large displacement is cracked. May be caused. The first protrusion length Lo is measured along the arc shape of the folded portion 15, and the outer end of the folded portion 15 starts from the position where the normal line standing on the folded portion 15 contacts the outer end 6 e of the belt layer 6. It is the distance to 22.

  FIG. 4 shows a plan development view of the internal structure of the tread portion 2 of another embodiment. In the embodiment of FIG. 4, a reinforcing rubber layer 23 is disposed between the main body portion 14 of the side carcass 12 and the folded portion 15 on the belt side. The reinforcing rubber layer 23 can further increase the rigidity of both end portions of the tread portion 2, and can further improve the steering stability performance of the tire 1.

  The complex elastic modulus of the reinforcing rubber layer 23 is preferably 4 to 10 MPa, for example. When the complex elastic modulus is less than 4 MPa, it is difficult to increase the rigidity of both end portions of the tread portion 2, and it is difficult to improve the steering stability performance of the tire 1. On the contrary, when the complex elastic modulus is larger than 10 MPa, the rigidity of both end portions of the tread portion 2 is excessively increased, and there is a possibility that cracks are generated at both end portions of the tread portion 2. From such a viewpoint, the complex elastic modulus of the reinforcing rubber layer 23 is preferably 5.5 to 8.5 MPa.

  FIG. 5 shows an enlarged view of the vicinity of the tread grounding end Te of the tread portion 2 of another embodiment. As shown in FIG. 5, the outer end 24 in the tire axial direction of the reinforcing rubber layer 23 is, for example, a belt-side folded portion 15 in order to suppress the occurrence of cracks in the sidewall portion 3 due to the outer end 24. It is desirable to be located on the inner side in the tire axial direction than the outer end 22 in the tire axial direction.

  The second protrusion length L2 from the outer end 24 in the tire axial direction of the reinforcing rubber layer 23 to the outer end 22 in the tire axial direction of the folded portion 15 on the belt side is preferably 2 to 10 mm, for example. When the second protrusion length L2 is less than 2 mm, it is difficult to cover the outer end 24 of the reinforcing rubber layer 23 with the side carcass 12, and there is a risk of causing a crack in the sidewall portion 3. On the contrary, when the second protrusion length L2 is larger than 10 mm, the width of the reinforcing rubber layer 23 in the tire axial direction becomes small, and there is a possibility that the effect of increasing the rigidity of both end portions of the tread portion 2 cannot be exhibited sufficiently.

  Further, for example, when the mounting direction of the tire 1 with respect to the vehicle is specified, the reinforcing rubber layer 23 may be disposed only on either the vehicle inner side of the tire 1 or the vehicle outer side of the tire 1. The reinforcing rubber layer 23 is preferably disposed only on the vehicle outer side of the tire 1 from the viewpoint of, for example, increasing the rigidity of the vehicle outer side of the tread portion 2 and improving the steering stability performance of the tire 1 more effectively. .

  As mentioned above, although this embodiment was explained in full detail, this invention is not limited to these embodiment, It can deform | transform into a various aspect and can be implemented.

  Pneumatic tires were prototyped based on the specifications in Table 1, and the tire mass, tire radial stiffness and tire axial stiffness were evaluated.

For comparison, a pneumatic tire (Comparative Example 1) having a carcass extending in a toroidal shape between bead cores was manufactured and evaluated in the same manner as in the Examples.
The main common specifications are as follows.

tire:
Size: 195 / 65R15
Internal pressure: 230 kPa
Rim width: 15 × 6J
The evaluation method is as follows.

<Tire mass>
The mass per tire was measured.

<Tire radial stiffness>
After each tire was assembled to the rim, a longitudinal load of 4.24 ± 1 kN was applied, and the amount of vertical deflection of the tire was measured. Then, the rigidity in the tire radial direction was approximately obtained by dividing the load of 4.24 ± 1 kN by the amount of vertical deflection.

<Tire axial rigidity>
After each tire was assembled to the rim, a longitudinal load of 4.24 kN and a lateral load of 0.5 ± 0.5 kN were applied, and the amount of lateral deflection of the tire was measured. Then, the rigidity in the tire axial direction was approximately obtained by dividing the load 0.5 ± 0.5 kN by the lateral deflection amount.

  As shown in Table 1, it can be confirmed that the tires of the examples can increase the rigidity while suppressing an increase in mass, and the steering stability performance can be improved.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 6 Belt layer 10 Bead core 11 Carcass 12A 1st side carcass 12B 2nd side carcass 13 Outer end 14 Main part 15 Inner end 19 Inner end 19 Bead Side turn-up part C Tire equator

Claims (7)

A tread portion in which a belt layer is arranged, a pair of sidewall portions extending inward in the tire radial direction from both ends of the tread portion, and a bead provided at an inner end of each sidewall portion and having a bead core embedded therein A pneumatic tire having a portion,
One end of the belt layer on one side of the tire equator, a first side carcass extending between the bead cores, and the other end of the belt layer on the other side of the tire equator; A carcass composed of a second side carcass extending between the bead cores;
The first side carcass and the second side carcass are separated from each other in the tread portion,
Each side carcass is
A main body portion continuously extending from an outer end located inward in the tire radial direction of the belt layer to an inner end in the tire radial direction reaching the bead core;
A belt-side folded portion that continues to the outer end of the main body and is folded back to the outside in the tire axial direction;
A pneumatic tire comprising: a bead-side folded portion that continues to the inner end of the main body and is folded outwardly in a tire radial direction.   The pneumatic tire according to claim 1, wherein the belt-side folded portion is provided between the main body portion and the belt layer.   The pneumatic tire according to claim 1 or 2, wherein an overlap length Li between each side carcass and the belt layer is 5 to 30 mm in a tire meridian section including a tire rotation axis.   The pneumatic tire according to any one of claims 1 to 3, wherein an outer end in the tire axial direction of the folded portion on the belt side is located on an outer side in the tire axial direction with respect to the outer end of the belt layer.   The pneumatic tire according to claim 4, wherein a length Lo from the outer end of the belt layer to an outer end in the tire axial direction of the folded portion on the belt side is 10 to 40 mm.   The pneumatic tire according to any one of claims 1 to 5, wherein each side carcass is provided with a reinforcing rubber layer having a complex elastic modulus of 4 to 10 MPa between the main body portion and the folded portion on the belt side. tire. The outer end in the tire axial direction of the reinforcing rubber layer is located on the inner side in the tire axial direction than the outer end in the tire axial direction of the folded portion on the belt side,
The pneumatic tire according to claim 6, wherein a length from an outer end of the reinforcing rubber layer in the tire axial direction to an outer end of the folded portion on the belt side in the tire axial direction is 2 to 10 mm.

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