JP3192764B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having a carcass layer in which a number of cords substantially orthogonal to a tire equatorial plane are embedded.

[0002]

2. Description of the Related Art In general, a pneumatic radial tire is superior to a pneumatic bias tire in various characteristics such as abrasion resistance and cornering characteristics, but is somewhat inferior in vibration riding comfort. The reason is that, in a bias tire, the cord embedded in the carcass layer is inclined with respect to the tire equatorial plane. Therefore, when an external force is applied to the bias tire from the road surface, the cord is pantograph deformed and the external force is changed. (Vibration) is absorbed, but in the radial tire, the cord embedded in the carcass layer is substantially orthogonal to the tire equatorial plane, so that the carcass layer can hardly absorb the external force applied to the radial tire. Moreover, in the radial tire, since the belt layer having high bending rigidity is arranged outside the carcass layer, the external force applied from the road surface during traveling is transmitted to the carcass layer with almost no attenuation.

[0003] For this reason, conventionally, in order to improve the riding comfort of a radial tire, for example, a side rubber covering an axially outer side of a carcass layer is formed of non-foamed rubber having an extremely low elastic modulus, and the side rubber is formed by the side rubber. In order to absorb and attenuate the external force (vibration) that is transmitted, there has been proposed.

[0004]

However, such conventional pneumatic radial tires can absorb a certain amount of vibration, but in recent years, high occupancy performance has been required more and more with the sophistication of vehicles. As a result, the absorption effect has become insufficient.

An object of the present invention is to provide a pneumatic radial tire capable of effectively absorbing and attenuating an external force received from a road surface during running and improving the riding comfort.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toroidal carcass layer in which a number of cords substantially orthogonal to the tire equatorial plane are embedded, and a carcass layer disposed radially outside the carcass layer. In the pneumatic radial tire having a belt layer, a tread disposed radially outward of the belt layer, and a side rubber that covers the axial outside of the carcass layer, the side rubber is disposed on the inner side close to the carcass layer. A cushioning rubber layer made of foam rubber arranged,
And an outer rubber layer made of non-foamed rubber disposed outside the carcass layer.

[0007]

Assume that the tire according to the present invention is running on a road surface. At this time, if there is unevenness on the road surface, a radial external force is repeatedly applied to the tire from the road surface, and this external force is transmitted from the tread and the belt layer to the vehicle through the carcass layer and the side rubber. Here, since the side rubber has a cushion rubber layer made of foamed rubber disposed on the inner side close to the carcass layer, when the above-described external force (vibration) is received, the bubbles in the foamed rubber become high-performance air springs. And effectively absorbs and attenuates this external force (vibration) over a wide frequency band. As a result, external force (vibration) transmitted into the cabin of the vehicle is reduced, and the riding comfort is improved. In addition, the outer part of the side rubber may be damaged by contact with the curb etc. during running, but since this outer part is made of non-foamed rubber (outer rubber layer) with high breaking strength, crack resistance etc. It has the same performance as the tires.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 11 denotes a pneumatic radial tire. The tire 11 has at least one pair, in this embodiment, a pair of beads 13 in which a pair of beads 12 are buried, and substantially radially outward from the beads 13. And a pair of side wall portions 14 extending
A generally cylindrical crown portion 15 connecting the radially outer ends of 14
And The tire 11 has one bead portion.
It is reinforced by a toroidal carcass layer 21 extending from 13 to the other bead portion 13, and this carcass layer 21 is
It comprises at least one carcass ply 22 in which a number of organic fiber cords extending in the radial direction (meridian direction) are embedded, in this embodiment, one carcass ply 22. Both ends in the width direction of the carcass layer 21 are anchored to the bead 12 by being folded around the bead 12 from the inside in the axial direction to the outside in the axial direction. In addition, between the folded portion of the carcass layer 21 and the main body portion, a radially inner end of a filler 23 having a triangular cross section whose radially inner end is press-bonded to the bead 12 is disposed. It is made of hard rubber (for example, JIS hardness of 70 to 90 degrees). A belt layer 29 composed of at least two (two in this embodiment) belt plies 28 is disposed radially outside the carcass layer 21, and a number of steel cords embedded in the belt plies 28 are tires. They incline at a relatively small predetermined angle (for example, 22 degrees) with respect to the equatorial plane E, and intersect with each other by inclining at least two belt plies 28 in opposite directions. A tread 33 having grooves 32 such as lateral grooves is disposed radially outside the belt layer 29, and side rubbers 34 covering the carcass layer 21 are disposed axially outside both sides of the carcass layer 21. ing. Reference numeral 35 denotes an inner liner made of a thin non-foamed rubber disposed inside the carcass layer 21, and reference numeral 36 denotes a chafer made of rubber having a relatively high hardness and covering the carcass layer 21 in the bead portion 13 from the outside.

When the vehicle travels on a road surface with such a radial tire 11, the tire 11
Tread 33 repeatedly receives an external force in the radial direction. Here, since the tire 11 has a belt layer 29 in which a steel cord is embedded in the crown portion 15, the crown portion 15
As a result, the external force is transmitted from the tread 33 to the carcass layer 21 via the belt layer 29 with little attenuation, and the carcass layer 21 to which the external force is transmitted is Since the cord embedded in the tire 11 is substantially perpendicular to the tire equatorial plane E, the external force can hardly be absorbed, and the external force (vibration) received by the tire 11 is attenuated to a large extent. Without being transmitted to the passenger compartment through the carcass layer 21 and the side rubber 34, the ride comfort is deteriorated. Therefore, in this embodiment,
The side rubber 34 includes a cushion rubber layer 38 made of foamed rubber disposed on the inner side adjacent to the carcass layer 21, and a carcass layer
And an outer rubber layer 39 made of non-foamed rubber, which is disposed on the outside and is separated from 21. Here, since the cushion rubber layer 38 is made of foamed rubber having a large number of bubbles inside, when the above-described external force (vibration) is received, the bubbles inside the foamed rubber are much larger than the rubber when the foamed rubber is deformed. Acts as a high-performance air spring. As a result, the external force (vibration) is effectively absorbed over a wide frequency band and is reliably attenuated. As a result, the external force (vibration) transmitted to the interior of the vehicle through the sidewall portion 14 is reduced, and the vibration is reduced. Comfort is improved. In addition, the outer portion of the side rubber 34 may be damaged by contact with a curb or the like during traveling, but since the outer portion is made of the same type of non-foamed rubber (outer rubber layer 39) as the tread 33 having high breaking strength, With respect to crack resistance and the like, it has the same performance as a conventional tire.

Here, the buffer rubber layer 38 and the outer rubber layer 39
Is changed in a wave form toward the meridian direction, whereby the buffer rubber layer 38 and the outer rubber layer 39
Is preferably repeatedly changed in the radial direction between large and small. The reason is that when the thickness of the cushion rubber layer 38 is changed as described above, thick portions of the cushion rubber layer 38 repeatedly appear, and the thick portions absorb external force (vibration) in a wide range. Because you can. The volume ratio of the buffer rubber layer 38 to the side rubber 34 is preferably in the range of 20% to 70%. The reason is that if the volume ratio is less than 20%, the effect of absorbing the external force described above is not sufficient.
%, The strength of the entire side rubber 34 decreases, and crack resistance and the like decrease. Further, it is preferable that the outer end of the buffer rubber layer 38 which is close to the belt layer 29 does not reach the belt layer 29 and is slightly away from the belt layer 29. The reason is that a large shear strain is generated in the vicinity of the belt end of the belt layer 29 during running, but when the outer end of the cushioning rubber layer 38 is in contact with the vicinity of the belt end of the belt layer 29, breakage occurs due to the shear strain. The outer end of the cushion rubber layer 38 made of foam rubber having low strength may be easily broken, which may cause belt end separation, and furthermore, heat generated by the shear strain is stored and the temperature rises. Because.
The buffer rubber layer 38 usually has a JIS hardness of 40.
A foamed rubber having a foaming rate V in the range of 10% to 80% is used. Here, the foaming ratio V is a value calculated by the following equation. V = (ρ ₀ / ρ ₁ over 1) × 100 (%) where, [rho ₀ is the density of the rubber solid phase portion of the foamed rubber (g / cm ^3),
[rho ₁ is the density of the foamed rubber (g / cm ^3). Further, the cells in the foamed rubber constituting the buffer rubber layer 38 may be open cells, but are preferably closed cells. The reason is that the closed-cell foamed rubber has a higher breaking strength than the open-cell foamed rubber.

Next, test examples will be described. In this test, the conventional rubber having only the same type of non-foamed rubber as the side rubber of the tread, and the side rubber having a foaming rate V of
A test tire was prepared comprising a buffer rubber layer made of foamed rubber having 40%, a volume ratio to the side rubber of 50%, and cells having closed cells, and an outer rubber layer made of non-foamed rubber of the same type as the tread. Where the size of each tire is 175 /
65 R14, and the compounding ratio of the rubber constituting the cushioning rubber layer (foam rubber) is natural rubber (glass transition temperature -72
℃) is 60.0 parts by weight, and polybutadiene rubber (glass transition temperature -100 ℃) is 40.0 parts by weight, totaling 100 parts by weight,
70.0 parts by weight of carbon black, 30.0% of process oil
Parts by weight, 1.0 parts by weight of wax, 2.0 parts by weight of stearic acid, 1.5 parts by weight of aging, 3.0 parts by weight of zinc white, 1.5 parts by weight of vulcanizing agent, 1.5 parts by weight of sulfur, blowing agent (dinitroso-pentane) Methylene tetraamine) was 4.0 parts by weight. Next, after filling each tire with an internal pressure of 1.8 kg / cm ² , it was mounted on a domestic 3000 cc class car and ran on a winding road. Was good. In addition, after mounting the tires on the fixed shaft of a commercially available protruding vibration tester, the load fluctuation on the fixed shaft was measured when the truncated quadrangular pyramid-shaped protrusion was passed at 50 km / h while applying a load of 485 kg. did. As a result, assuming that the conventional tire has an index of 100, the test tire has an index of 85, indicating that the riding comfort is improved.

[0012]

As described above, according to the present invention, it is possible to effectively absorb and attenuate the external force received from the road surface during traveling, thereby improving the riding comfort.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view of a tire showing one embodiment of the present invention.

[Explanation of symbols]

 11 ... pneumatic radial tire 21 ... carcass layer 29 ... belt layer 33 ... tread 34 ... side rubber 38 ... cushion rubber layer 39 ... outer rubber layer E ... tire equatorial plane

Claims (1)

(57) [Claims] 1. A toroidal carcass layer in which a number of cords substantially orthogonal to the tire equatorial plane are embedded, a belt layer disposed radially outside the carcass layer, and a radius of the belt layer. A tread arranged on the outside in the direction,
A side rubber covering the outside in the axial direction of the carcass layer, a pneumatic radial tire comprising:
A pneumatic radial, comprising: a buffer rubber layer made of foamed rubber disposed on the inner side adjacent to the carcass layer; and an outer rubber layer made of non-foamed rubber disposed on the outer side separated from the carcass layer. tire.