TECHNICAL FIELD

The present technology relates to a pneumatic tire provided with a partial tie rubber layer selectively disposed on a portion between a carcass layer and innerliner layer, and particularly relates to a pneumatic tire capable of reducing tire weight and rolling resistance while maintaining handling stability on a dry road surface.

BACKGROUND ART

In general, for a pneumatic tire, when an unvulcanized tire is inflated when manufacturing a tire, a tie rubber layer is disposed between a carcass layer and innerliner layer in order to prevent a carcass cord from biting into the innerliner layer.

In recent years, for this tie rubber layer, using a partial tie rubber layer selectively disposed on a portion and not an entire region between the carcass layer and innerliner layer has been proposed in order to achieve a reduction in tire weight and rolling resistance (for example, refer to Japan Patent No. 5239507). This partial tie rubber layer is disposed on at least a shoulder region (site where engaging of the carcass cord easily occurs when inflating due to a large curvature), and therefore, a sufficient effect can be achieved as compared to a conventional tie rubber layer (full tie rubber layer) disposed on an entire region between the carcass layer and innerliner layer.

However, simply removing a portion of the full tie rubber layer to achieve a partial tie rubber layer has problems where rigidity is reduced as compared to a conventional tire using a full tie rubber layer, and thus sufficiently maintaining handling stability performance (dry handling stability) is difficult. Therefore, when reducing tire weight and rolling resistance using a partial tie rubber layer, further improvement for preventing reduction in dry handling stability performance is required.

SUMMARY

The present technology provides a pneumatic tire with a partial tie rubber layer selectively disposed on a portion between a carcass layer and innerliner layer, which is capable of reducing tire weight and rolling resistance while maintaining handling stability on a dry road surface.

A pneumatic tire of a first technology includes: an annular-shaped tread portion where a mounting direction with regard to a vehicle is specified, and that extends in a tire circumferential direction; a pair of sidewall portions disposed on both sides of the tread portion; a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions; a carcass layer bridging between the pair of bead portions; a belt layer being disposed on an outer circumferential side of the carcass layer in the tread portion; an innerliner layer being disposed on a tire inner surface along the carcass layer; and partial tie rubber layers being selectively disposed between the carcass layer and innerliner layer in a region on both sides in a tire width direction excluding a center region of the tread portion; wherein end portions of the partial tie rubber layers on a tire equator side are disposed within a range of 10 mm to 25 mm on the inner side in the tire width direction from an end portion on an outermost side in the tire width direction of the belt layers; a rubber thickness t1of an inner tie rubber layer disposed on a vehicle inner side being one of the partial tie rubbers differs from a rubber thickness t2of an outer tie rubber layer disposed on a vehicle outer side being the other of the partial tie rubbers; and the rubber thickness t2of the outer tie rubber layer is from 120% to 200% of the rubber thickness t1of the inner tie rubber layer.

A pneumatic tire of a second technology includes: an annular-shaped tread portion where a mounting direction with regard to a vehicle is specified, and that extends in a tire circumferential direction; a pair of sidewall portions disposed on both sides of the tread portion; a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions; a carcass layer bridging between the pair of bead portions; a belt layer being disposed on an outer circumferential side of the carcass layer in the tread portion; an innerliner layer being disposed on a tire inner surface along the carcass layer; and partial tie rubber layers being selectively disposed between the carcass layer and innerliner layer in a region on both sides in a tire width direction excluding a center region of the tread portion; wherein end portions of the partial tie rubber layers on a tire equator side are disposed within a range of from 10 mm to 25 mm on the inner side in the tire width direction from an end portion on an outermost side in the tire width direction of the belt layers; a periphery length x1of an inner tie rubber layer disposed on a vehicle inner side being one of the partial tie rubbers differs from a periphery length x2of an outer tie rubber layer disposed on a vehicle outer side being the other of the partial tie rubbers; and a difference Δx between the periphery length x2of the outer tie rubber layer and the periphery length x1of the inner tie rubber layer is 0.25 times or less a periphery length X along a tire inner surface from a bead toe to a tire equator.

A pneumatic tire of a third technology includes: an annular-shaped tread portion where a mounting direction with regard to a vehicle is specified, and that extends in a tire circumferential direction; a pair of sidewall portions disposed on both sides of the tread portion; a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions; a carcass layer bridging between the pair of bead portions; a belt layer being disposed on an outer circumferential side of the carcass layer in the tread portion; an innerliner layer being disposed on a tire inner surface along the carcass layer; and partial tie rubber layers being selectively disposed between the carcass layer and innerliner layer in a region on both sides in a tire width direction excluding a center region of the tread portion; wherein end portions of the partial tie rubber layers on a tire equator side are disposed within a range of 10 mm to 25 mm on the inner side in the tire width direction from an end portion on an outermost side in the tire width direction of the belt layers; a rubber hardness h1of an inner tie rubber layer disposed on a vehicle inner side being one of the partial tie rubbers differs from a rubber hardness h2of an outer tie rubber layer disposed on a vehicle outer side being the other of the partial tie rubbers; and the rubber hardness h2of the outer tie rubber layer is 105% to 150% of the rubber hardness h1of the inner tie rubber layer.

In the present technology, a partial tie rubber layer is used, and therefore, tire weight and rolling resistance can be reduced as compared to a conventional pneumatic tire having a full tie rubber layer. At this time, rubber thickness (first technology), periphery length (second technology), and rubber hardness (third technology) vary for an inner tie rubber layer disposed on a vehicle inner side and an outer tie rubber layer disposed on a vehicle outer side, and increase on the outer tie rubber layer more than the inner tie rubber layer, and therefore, the rigidity of a sidewall portion on the vehicle outer side can be increased, and dry handling stability can be maintained at a high degree.

The first technology, second technology, and third technology can be combined with each other. In other words, in the first technology (when setting the rubber thickness), a periphery length x1of an inner tie rubber layer differs from a periphery length x2of an outer tie rubber layer, and a difference Δx between the periphery length x2of the outer tie rubber layer and the periphery length x1of the inner tie rubber layer is 5 mm or greater and 0.25 times or less a periphery length X of a tire inner surface from a bead toe to a tire equator. Thereby, the rigidity of the sidewall portion on the vehicle outer side can be further enhanced, which is advantageous in enhancing dry handling stability. Note that in the present technology, “periphery length” refers to a length measured along an extension direction of tire components (outer tie rubber layer, inner tie rubber layer, tire inner surface) in a tire meridian cross section.

Furthermore, in the first technology (when setting the rubber thickness) or second technology (when setting the periphery length), a rubber hardness h1of an inner tie rubber layer differs from a rubber hardness h2of an outer tie rubber layer, and the rubber hardness h2of the outer tie rubber layer is preferably from 105% to 150% of the rubber hardness h1of the inner tie rubber layer. Thereby, the rigidity of the sidewall portion on the vehicle outer side can be further enhanced, which is advantageous in enhancing dry handling stability. Note that “rubber hardness” in the present technology refers to a hardness (referred to as JIS-A hardness) measured at 23° C. by a type A durometer in accordance with JIS (Japanese Industrial Standard) K 6253.

