JP2008179255A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the rolling resistance of a pneumatic tire 1 by reducing the strain energy loss of a tread rubber constituting a tread part 15 while sufficiently ensuring the cut resistance of the pneumatic tire 1. <P>SOLUTION: The intersection width BW of an intersection belt 27 is ≥1.05 times the ground contact width GW of a tread part 15. The decreasing quantity δ at a ground contact end Pg of a tread part 15 with respect to the height Pc at the center position in the tire width direction Dw on a tread of the tread part 15 is 0.12 to 0.25 H, where H denotes the tire sectional height. The tensile strength per unit width of a carcass ply 11 is ≥14 kgf/mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that can reduce rolling resistance while sufficiently securing cut resistance.

  In general, rolling resistance of a pneumatic tire causes energy loss and hinders improvement in fuel consumption of the vehicle. In addition, most of the rolling resistance of pneumatic tires is due to strain energy loss of the tread rubber that constitutes the tread part. From the results of recent research, mainly in the tire circumferential direction near the center of the tread part (including the center). It is known that a strain energy loss of the tread rubber is caused mainly by shear deformation in the tire width direction in the vicinity of the ground contact end (including the ground contact end) of the tread portion due to the shear deformation (known knowledge). And the applicant of this invention has already developed the pneumatic tire (refer patent document 1) which can reduce rolling resistance based on a well-known knowledge.

That is, in the pneumatic tire according to this prior art, the intersection width of the intersection belt is made shorter than the contact width of the tread portion, and the tread portion has a height relative to the height of the center position in the tire width direction on the tread surface. By increasing the amount of shoulder descent at the ground end, the deflection near the ground end of the tread is increased, increasing eccentric deformation near the center of the tread, and shearing in the tire circumferential direction near the center of the tread. Deformation is suppressed. In addition, by making the crossing width of the crossing belt shorter than the contact width of the tread, in other words, by preventing the crossing belt from being positioned on the inner side in the tire radial direction near the grounding end of the tread, Shear deformation in the tire width direction in the vicinity of the contact end of the tread portion due to shrinkage in the tire width direction is suppressed. Thereby, in the pneumatic tire according to the prior art, the strain energy loss of the tread rubber is reduced, and the rolling resistance is reduced.
JP 2006-1360 A

  By the way, in the pneumatic tire according to the prior art, as described above, there is no cross belt positioned on the inner side in the tire radial direction in the vicinity of the grounding end of the tread portion, or in the vicinity of the grounding end of the tread portion in the crossing belt. Since there are few parts located inside the tire radial direction, if the shoulder region near the contact edge of the tread part is stepped on, for example, a nail or a bolt, the carcass ply is likely to have a cord cut (carcass cord cut). There is a problem that the cut resistance of the resin deteriorates. That is, in the pneumatic tire according to the prior art, there is a problem that it is extremely difficult to reduce rolling resistance while sufficiently securing cut resistance.

  Then, an object of this invention is to provide the pneumatic tire of a novel structure which can solve the above-mentioned problem.

  As a result of repeating various experiments in order to solve the above-mentioned problems, the inventor of the present invention has (i) the crossing width of the crossing belt is 1.05 times or less of the ground contact width of the tread portion. (Ii) When the tire cross-section height is H, the shoulder descent amount δ of the tread portion with respect to the center position in the tire width direction on the tread surface is 0.12H to 0.25H. If the tensile strength per unit width of the carcass ply is set to 14 kgf / mm or more on condition that the two requirements are satisfied, the impact energy of 1500 J acts on the shoulder region near the grounded end of the tread portion. However, a novel finding that cord breakage (carcass cord breakage) hardly occurs in the carcass ply can be obtained, and the present invention has been completed. Note that the impact energy of 1500 J is used as an index indicating an acceptable level of cut resistance in the market.

  According to a first aspect of the present invention (the invention described in claim 1), a pair of bead portions each having a bead core, and a plurality of carcasses anchored so as to be folded back to the bead core at the corresponding bead portions. A toroidal carcass ply formed by rubberizing a cord, a tread portion provided on an outer surface of a crown portion of the carcass ply, the tread portion on an outer surface of the carcass ply and one of the bead portions And a plurality of belts provided between the tread portion and the other bead portion, and between the carcass ply and the tread portion and extending in a direction inclined in the tire circumferential direction. A belt layer of two or more layers formed by rubberizing a cord, and before at least two of the two or more belt layers The belt layer constitutes an intersecting belt extending in a direction in which the belt cords intersect with each other, the intersecting width of the intersecting belt is 1.05 times or less of the contact width of the tread portion, and the tire cross-section height is H In this case, the shoulder descent amount δ of the grounding end of the tread portion with respect to the height of the center position in the tire width direction on the tread surface of the tread portion is 0.12H to 0.25H, and the carcass ply The gist is that the tensile strength per unit width is 14 kgf / mm or more.

  Here, the amount of shoulder descent δ at the ground contact end of the tread portion is set to 0.12H or more. When the amount of shoulder descent δ is less than 0.12H, the eccentric deformation near the center of the tread portion is increased. This is because it becomes difficult. On the other hand, the shoulder descent amount δ of the grounding end of the tread portion is set to 0.25H or less because when the shoulder descent amount δ exceeds 0.25H, it is difficult to ensure a sufficient ground contact area of the tread portion. Because it becomes.

  In the specification and claims, the dimensions of each part of the pneumatic tire are such that the pneumatic tire is mounted on an applicable rim described in JATMA or a standard equivalent thereto and filled with the maximum air pressure specified in the standard. After that, it is measured in a no-load state. However, the ground contact width must be set to the rim after the pneumatic tire is mounted and filled with the highest air pressure, and then placed perpendicular to the flat plate, and the maximum load load (for example, in the case of a passenger car pneumatic tire, the maximum The maximum length in the tire width direction of the contact surface with the flat plate in a state where a load corresponding to 100% of the load capacity) is applied.

  According to the first feature of the present invention, the crossing width of the crossing belt is 1.05 times or less of the grounding width of the tread portion, and the shoulder drop amount δ of the grounding end of the tread portion is 0.12H. Since it is ˜0.25H, the deflection in the vicinity of the ground contact end of the tread portion is increased, the eccentric deformation near the center of the tread portion is increased, and the tire circumferential direction in the vicinity of the center of the tread portion is increased. Shear deformation can be suppressed. In addition, since the intersecting width of the intersecting belt is 1.05 times or less of the contact width of the tread portion, in other words, the intersecting belt is crossed on the inner side in the tire radial direction near the contact end of the tread portion. The tire near the grounding end of the tread portion due to the shrinkage of the crossing belt in the tire width direction due to the fact that the belt is not positioned or the portion of the crossing belt located in the tire radial direction near the grounding end of the tread portion is small. Shear deformation in the width direction can be suppressed.

  The crossing width of the crossing belt is 1.05 times or less of the grounding width of the tread part, and the shoulder descent amount δ of the grounding end of the tread part with respect to the height of the center position in the tire width direction on the tread surface of the tread part. Is 0.12H to 0.25H, and the tensile strength per unit width of the carcass ply is 14 kgf / mm or more, so that it is close to the grounding end of the tread portion in consideration of the above-mentioned new knowledge Even when an impact energy of 1500 J is applied to the shoulder region, the carcass ply is hardly broken (the carcass cord is broken).

  The second feature of the present invention (feature of the invention described in claim 2) is that, in addition to the first feature, the intersection width of the intersection belt is shorter than the ground contact width of the tread portion. And

  The third feature of the present invention (the feature of the invention described in claim 3) is that, in addition to the first feature or the second feature, a rubber gauge (rubber thickness) from the folded end of the carcass ply to the tire outer surface. ) Is 5 mm or less.

  According to a fourth feature of the present invention (a feature of the invention described in claim 3), in addition to any one of the first to third features, the height of the folded end of the carcass ply is The gist is that it is 0.20H or more.

  According to a fifth feature (feature of the invention described in claim 5) of the present invention, in addition to any one of the first feature to the fourth feature, the carcass cord is made of polyketone fiber. It is a summary.

  According to a sixth feature of the present invention (a feature of the invention described in claim 6), in addition to any one of the first to fourth features, the carcass cord is made of polyethylene terephthalate fiber. The gist of the present invention is that the thickness of the carcass cord is 1100 dtx / 2 or more.

  The seventh feature of the present invention (the feature of the invention described in claim 7) is the first feature or the second feature in addition to any one of the first feature to the fourth feature. In addition, the gist of the present invention is that the carcass cord is made of rayon fiber, and the thickness of the carcass cord is 1100 dtx / 2 or more.

  According to the invention described in any one of claims 1 to 7, even if an impact energy of 1500 J acts on a shoulder region near the ground contact end of the tread portion, a cord breakage occurs in the carcass ply. It hardly occurs and can suppress shear deformation in the tire circumferential direction in the vicinity of the center of the tread part and shear deformation in the tire width direction in the vicinity of the ground contact end of the tread part. It is possible to reduce the rolling resistance of the pneumatic tire by reducing the strain energy loss of the tread rubber constituting the tread portion while sufficiently securing the property.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

  Here, FIG. 1 is a cross-sectional view of a pneumatic tire according to an embodiment of the present invention, FIG. 2 is a developed plan view showing a relationship between a cross belt and a carcass ply according to an embodiment of the present invention, and FIG. It is sectional drawing of the pneumatic tire of another aspect which concerns on embodiment of invention.

  As shown in FIGS. 1 and 2, the pneumatic tire 1 according to the embodiment of the present invention includes a pair of annular bead portions 5 that can be fitted to an applicable rim 3, and each bead portion 5 includes a bead core. 7 and a bead filler 9 disposed outside the bead core 7 in the tire radial direction Dr. Further, one end of a toroid-shaped carcass ply 11 is moored to the bead core 7 in one bead portion 5, and the bead core 7 in the other bead portion 5 is in addition to the carcass ply 11. The ends are moored so that they are folded back. In other words, both end portions of the carcass ply 11 are moored so as to be folded back to the bead core 7 in the corresponding bead portion 5. Here, the carcass ply 11 is formed by rubber drawing a plurality of carcass cords 13 extending in the radial direction, and details of the carcass ply 11 will be described later.

  A tread portion 15 is provided on the outer peripheral surface of the crown portion of the carcass ply 11, and a plurality of circumferential main grooves 17 extending in the tire circumferential direction Dc are formed in the tread portion 15. Further, sidewall portions 19 are provided between the tread portion 15 and the one bead portion 5 and between the tread portion 15 and the other bead portion 5 on the outer surface of the carcass ply 11. Furthermore, an inner liner 21 is provided on the inner side surface of the carcass ply 11 to prevent air leakage.

  Between the carcass ply 11 and the tread portion 15, a so-called two-layer belt layer 23 exhibiting an effect is provided, and the belt layer 23 extends in a direction inclined with respect to the tire circumferential direction Dc. The belt cord 25 is made of rubber, and the belt cord 25 is made of steel fiber. The belt layer 23 is not limited to two layers, and may be two or more layers.

  Next, the characteristic part of the pneumatic tire 1 which concerns on embodiment of this invention is demonstrated.

The two belt layers 23 constitute a cross belt 27 that extends in a direction in which the belt cords 25 cross each other. The cross width BW of the cross belt 27 is shorter than the ground contact width GW of the tread portion 15. Specifically, it is 0.6 GW to 0.85 GW. The belt width of one of the two belt layers 23 may be longer than the ground contact width GW of the tread portion 15.
When two or more belt layers 23 are provided, at least two belt layers 23 of the three or more belt layers 23 may constitute the cross belt 27. Further, even if the cross width BW of the cross belt 27 is not shorter than the ground contact width GW of the tread portion 15, the cross width BW of the cross belt 27 is 1.05 of the ground width GW of the tread portion 15 as shown in FIG. If it is less than double, the rolling resistance can be reduced as compared with a pneumatic tire having no such configuration.

  As shown in FIGS. 1 and 2, when the tire cross-sectional height is H, the center position in the tire width direction Dw on the tread surface of the tread portion 15 (in other words, the tread portion 15 tread surface and the tire equatorial surface S are The position δ of the ground contact end Pg of the tread portion 15 with respect to the height of Pc is 0.12H to 0.25H. Here, the amount of shoulder descent δ of the ground contact end Pg of the tread portion 15 is set to 0.12H or more. If the amount of shoulder descent δ is less than 0.12H, the eccentric deformation near the center of the tread portion 15 increases. It is because it becomes difficult. On the other hand, the shoulder drop amount δ of the ground contact end Pg of the tread portion 15 is set to 0.25H or less. If the shoulder drop amount δ exceeds 0.25H, it is difficult to ensure a sufficient ground contact area of the tread portion 15. Because it becomes.

  Further, a predetermined intermediate position on the tread surface of the tread portion 15 with respect to the height of the center position Pc in the tire width direction Dw on the tread surface of the tread portion 15 (a position away from the tire equator surface S by 0.125 GW outward in the tire width direction Dw). The shoulder drop amount λ of Ps is 0 to 0.02H. Here, the shoulder drop amount λ at the predetermined intermediate position Ps is set to 0 or more because when the shoulder drop amount λ is less than 0, the distance between the center position Pc on the tread surface of the tread portion 15 and the predetermined intermediate position Ps. This is because there is a portion that does not contact with the ground. On the other hand, the shoulder drop amount λ at the predetermined intermediate position Ps is set to 0.02H or less because when the shoulder drop amount λ exceeds 0.02H, shear deformation in the tire circumferential direction Dc near the center of the tread portion 15 is large. Because it becomes.

  The tensile strength per unit width of the carcass ply 11 (the breaking strength of the carcass cord 13 × the number of driving of the carcass cord 13 per 1 mm width) is 14 to 50 kgf / mm. As a result of repeating various experiments, (i) the crossing width BW of the crossing belt 27 is 1.05 times or less of the ground contact width GW of the tread part 15, and (ii) the tread part 15 on the tread surface. Such a condition is that the two requirements that the shoulder fall amount δ of the ground contact end Pg of the tread portion 15 with respect to the height of the center position Pc in the tire width direction Dw is 0.12H to 0.25H are satisfied. The pneumatic tire can reduce the rolling resistance, but when the cut resistance is insufficient in the shoulder region near the grounded end of the tread portion, the tensile strength per unit width of the carcass ply 11 is 14 kgf / mm or more. Even if an impact energy of 1500 J (an index indicating an acceptable level of cut resistance) is applied to the shoulder region near the ground contact edge of the tread portion 15, the carcass plastic That cord-cut (cutting of the carcass cord 13) is not that most occur 11, be based on the novel finding, this novel finding is that obtained by repeating various experiments or the like. The tensile strength per unit width of the carcass ply 11 is set to 50 kgf / mm or less because when the tensile strength per unit width of the carcass ply 11 exceeds 50 kgf / mm, the carcass cord 11 becomes thicker and heavier. This is because it is difficult to sufficiently reduce the weight of the pneumatic tire 1.

  Then, as a specific configuration mode of the carcass cord 13, any one of the following three configuration modes is used. That is, in the first configuration mode, the carcass cord 13 is made of polyketone fiber, and the thickness of the carcass cord 13 is 1100 dtx / 2 or more. Further, in the second configuration mode, the carcass cord 13 is made of polyethylene terephthalate fiber, and the thickness of the carcass cord 13 is 1100 dtx / 2 or more (preferably, 1670 dtx / 2 or more). . Further, in the third configuration mode, the carcass cord 13 is made of rayon fiber, and the thickness of the carcass cord 13 is 1100 dtx / 2 or more (preferably, 1670 dtx / 2 or more).

  Further, the rubber gauge (rubber thickness) from the turn-up end 11t of the carcass ply 11 to the tire outer surface is 5 mm or less, and preferably 1.5 mm or more. Here, the reason that the rubber gauge is 5 mm or less from the turn-up end 11t of the carcass ply 11 to the outer surface of the tire is that if the rubber gauge exceeds 5 mm, the longitudinal strain at the time of load application decreases, and the eccentricity near the center of the tread portion 15 occurs. This is because deformation is suppressed and the rolling resistance reduction effect is reduced. The rubber gauge from the folded end 11t of the carcass ply 11 to the outer surface of the tire is 1.5 mm or more when a crack occurs at the folded end 11t of the carcass ply 11 if the rubber gauge is less than 1.5 mm. This is because cracks may extend due to running vibration, leading to bursts.

  Furthermore, the height of the turn-up end 11t of the carcass ply 11 is 0.20H or more. Here, the height of the turn-up end 11t of the carcass ply 11 is set to 0.20H or more because if the height of the turn-up end 11t of the carcass ply 11 is less than 0.20H, the pullout resistance of the carcass ply 11 is reduced. This is because it is difficult to ensure sufficient.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  Since the intersecting width BW of the intersecting belt 27 is shorter than the ground contact width GW of the tread portion 15 and the shoulder drop amount δ of the ground end Pg of the tread portion 15 is 0.12H to 0.25H, the ground contact of the tread portion 15 is achieved. By increasing the deflection near the end Pg, the eccentric deformation near the center of the tread portion 15 can be increased, and the shear deformation in the tire circumferential direction Dc near the center of the tread portion 15 can be suppressed. Further, since the intersecting width BW of the intersecting belt 27 is shorter than the contact width GW of the tread portion 15, in other words, the intersecting belt 27 is not located inside the tire radial direction Dr near the contact end Pg of the tread portion 15. Therefore, shear deformation in the tire width direction Dw in the vicinity of the ground contact end Pg of the tread portion 15 due to shrinkage of the cross belt 27 in the tire width direction Dw can be suppressed.

  The intersection width BW of the intersection belt 27 is shorter than the ground contact width GW of the tread portion 15, and the shoulder drop amount δ of the ground contact end Pg of the tread portion 15 is 0.12H to 0.25H. Since the tensile strength per unit width is 14 kgf / mm or more, considering the above-mentioned new knowledge, even if an impact energy of 1500 J acts on the shoulder region near the grounded end of the tread portion 15, the carcass There is almost no cord breakage (carcass cord 13 breakage) in the ply 11.

  Therefore, according to the embodiment of the present invention, the rolling resistance of the pneumatic tire 1 is reduced by reducing the strain energy loss of the tread rubber constituting the tread portion 15 while sufficiently securing the cut resistance of the pneumatic tire 1. Can be reduced.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, In addition, it can implement in a various aspect. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

  A pneumatic tire using the first configuration mode (carcass cord is polyketone fiber, carcass cord thickness is 1100 dtx / 2, and tensile strength per unit width is 20 kgf / mm) for the carcass ply is invented product 1, carcass ply. A pneumatic tire using the second configuration (the carcass cord is rayon fiber, the thickness of the carcass cord is 1100 dtx / 2, and the tensile strength per unit width is 14 kgf / mm) for the ply is the invention product 2, and the carcass ply A pneumatic tire using the second configuration (carcass cord is polyethylene terephthalate fiber, carcass cord thickness is 1670 dtx / 2, and tensile strength per unit width is 18 kgf / mm) is an invention product 3, and a carcass ply 2nd configuration aspect (carcass cord is polyethylene terephthalate fiber) Thickness is 1100dtx / 2 of the carcass cord, the tensile strength per unit width as the invention product 4 a pneumatic tire using the 14 kgf / mm), was fabricated under the tire size 235 / 35R19. In addition, a pneumatic tire using another configuration mode for the carcass ply (the carcass cord is polyethylene terephthalate fiber, the thickness of the carcass cord is 880 dtx / 2, and the tensile strength per unit width is 11 kgf / mm) is the same as a comparison product. Prototype under the tire size.

  Subsequently, an impact test is performed on the inventive products 1 to 4 and the comparative product by colliding a pendulum having a conical tip protrusion with a shoulder region near the ground contact edge of the tread portion of the inventive products 1 to 4 and the comparative product. I do. The results of this impact test are summarized as shown in Table 1 below.

Here, in Table 1, the impact index is an index of impact energy, and the larger the impact index, the greater the impact energy. The impact index 100 as a reference is an index of the impact energy 1700J. Even if the pendulum collides with the shoulder region near the grounding end of the tread portion with the impact energy 1700J, the shoulder near the grounding end of the tread portion. If there was no swelling in the region, it was determined that the cut resistance of the pneumatic tire was sufficiently secured. When the bulge is generated in the shoulder region near the ground contact end of the tread portion, the carcass ply often has a cord cut.

  That is, as shown in Table 1, it was confirmed that when the tensile strength per unit width of the carcass ply is 14 kgf / mm or more, the cut resistance of the pneumatic tire can be sufficiently secured.

It is sectional drawing of the pneumatic tire which concerns on embodiment of this invention. It is an expansion | deployment top view which shows the relationship between the cross belt and carcass ply which concern on embodiment of this invention. It is sectional drawing of the pneumatic tire of another aspect which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3 Applicable rim 5 Bead part 7 Bead core 9 Bead filler 11 Carcass ply 11t Folding end 13 Carcass cord 15 Tread part 19 Side wall part 23 Belt layer 25 Belt cord 27 Cross belt

Claims (7)

A pair of bead portions each having a bead core, a toroid-shaped one-layer carcass ply formed by rubberizing a plurality of carcass cords that are anchored so as to be folded back to the bead core at the corresponding bead portions; A tread portion provided on the outer surface of the crown portion of the carcass ply, and a portion between the tread portion and one of the bead portions on the outer surface of the carcass ply and between the tread portion and the other bead portion. A sidewall portion, and two or more belt layers formed by rubberizing a plurality of belt cords provided between the carcass ply and the tread portion and extending in a direction inclined in the tire circumferential direction,
Of the two or more belt layers, at least two of the belt layers constitute a cross belt extending in a direction in which the belt cords cross each other, and the crossing width of the cross belts is 1.. It is less than 05 times,
When the tire cross-sectional height is H, the shoulder descent amount δ of the ground contact end of the tread portion with respect to the height of the center position in the tire width direction on the tread surface of the tread portion is 0.12H to 0.25H. And
A pneumatic tire characterized by having a tensile strength per unit width of the carcass ply of 14 kgf / mm or more.   The pneumatic tire according to claim 1, wherein an intersection width of the intersection belt is shorter than a contact width of the tread portion.   The pneumatic tire according to claim 1 or 2, wherein a rubber gauge from the folded end of the carcass ply to the outer surface of the tire is 5 mm or less.   The pneumatic tire according to any one of claims 1 to 3, wherein a height of a folded end of the carcass ply is 0.20H or more.   The pneumatic tire according to any one of claims 1 to 4, wherein the carcass cord is made of polyketone fiber.   The said carcass cord consists of a polyethylene terephthalate fiber, Comprising: The thickness of the said carcass cord is 1100 dtx / 2 or more, The claim in any one of Claims 1-4 characterized by the above-mentioned. The described pneumatic tire.   The said carcass cord consists of rayon fiber, Comprising: The thickness of the said carcass cord is 1100 dtx / 2 or more, The claim in any one of the Claims 1-4 characterized by the above-mentioned. Pneumatic tires.

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