JP5429982B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire (hereinafter also simply referred to as “tire”), and more particularly, to a pneumatic radial tire that maintains or improves road noise performance while reducing rolling resistance.

  In general, in a pneumatic radial tire during high-speed running, a belt reinforcing layer that covers at least both ends of the belt layer is disposed outside the belt layer in the radial direction. This belt reinforcing layer suppresses the belt squeezing caused by the centrifugal force at the time of high-speed rotation by the tagging effect and enhances the high-speed durability of the tire.

  In recent years, with the upgrading of vehicles and the improvement in quality, especially in passenger cars, the reduction in vehicle vibration and improvement in ride comfort are rapidly progressing. The use of a polyketone cord, which is more elastic than the conventionally used aliphatic polyamide cord, for the cord of the belt reinforcing layer (hereinafter, also simply referred to as “cord”) further raises the belt. Studies such as increasing the suppression effect have been made.

  Furthermore, there has been great social interest in the recent rise in the price of petroleum resources, low fuel consumption from the viewpoint of environmental conservation, and reduction of risks to the global environment. In order to achieve these problems, many researches and proposals have been made on tire structures and tire reinforcing materials. For example, Patent Document 1 discloses a tire that uses a single-strand structure having only one strand as a band cord. Further, in Patent Document 2, by appropriately setting the twist coefficient, elongation rate, residual tension of the band cord, the number of cords to be corded, etc., the band layer tightening force is increased and the cost is reduced. In addition, a pneumatic radial tire has been disclosed that achieves improved steering stability, high-speed durability, and road noise performance during high-speed driving while achieving low weight.

Japanese Patent Publication No.59-1601 JP 2002-154304 A

  However, in order to improve high-speed durability and reduce road noise, adopting a method that applies a cord with higher strength and elasticity than the nylon cord mainly used as the cord of the belt reinforcement layer, on the other hand, In some cases, such as when driving in urban areas, rolling resistance in a relatively low speed region deteriorates.

  Accordingly, an object of the present invention is to provide a pneumatic radial tire that maintains or improves road noise performance while reducing rolling resistance in a relatively low speed region.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the magnitude of the rolling resistance in a relatively low speed region such as when traveling in an urban area is that of the cord of the belt reinforcing layer corresponding to the belt end vicinity. It has been found that there is a correlation with the magnitude of the tension in the tire, that is, the higher the tension of the cord of the belt reinforcing layer, the smaller the rolling resistance. In general, in the vulcanization process of a tire, the degree of expansion at the time of molding (vulcanization) is larger at the center part and the end part is smaller than the center part at the center part and the end part of the belt reinforcing layer. Yes. Thereby, the slack of the cord fiber is generated at the belt end portion, and as a result, the rolling resistance is deteriorated. Therefore, in a pneumatic radial tire in which a belt reinforcement layer is disposed at least at both ends of the belt layer, a cord of the belt reinforcement layer having a high dry heat shrinkage at the vulcanization temperature is relatively difficult to expand or compressive strain is reduced. Used for the belt layer reinforcement cord near the belt end, which is easy to receive, and found a technique to increase the cord tension at both ends near the belt end of the belt reinforcement layer in the tire by heat shrinkage of the belt layer reinforcement cord, and completed the present invention It came to do.

That is, the pneumatic radial tire of the present invention is disposed at least one or more pairs on the outer side in the radial direction of the crown portion of the carcass ply, a pair of right and left bead portions, a carcass ply extending from the crown portion to both bead portions via both side portions In a pneumatic radial tire comprising a belt, a belt reinforcing layer and a tread arranged on the outer side in the crown portion radial direction of the belt,
The value _{S Sho} and the following formula values _{S CL} and belt end vicinity portion in the tire width direction center portion of the 177 ° C. dry heat shrinkage value of the code of the belt reinforcing layer (I) ~ (III),
0.2 ≦ S _CL / S _Sho <1.0 (I)
1.3% ≦ S _Sho ≦ 6.0% (II)
1.0% ≦ S _CL <6.0% (III)
It is characterized by satisfying the relationship represented by

  In the pneumatic radial tire of the present invention, the boundary between the center portion in the tire width direction of the belt reinforcing layer and the vicinity of the belt end has the maximum belt width when the total width of the belt having the maximum belt width is 100. It is preferably within 15 from the end of the belt inward in the tire width direction, and the cord of the belt reinforcing layer is at least one of aliphatic polyamide, polyethylene terephthalate, polyethylene naphthalate, aramid, and polyketone fibers. It is preferably made of fibers, and the total fineness per cord is preferably in the range of 500 to 5000 dtex, and the dip cord of the cord of the belt reinforcing layer has an elongation at a load of 44 N of 0.5 to 8. It is preferable to be within the range of 0%, and furthermore, per unit width of the cord of the belt reinforcing layer Over de number is preferably from 40 to 70 present / 50 mm.

  According to the present invention, it is possible to provide a pneumatic radial tire that maintains or improves road noise performance while reducing rolling resistance in a relatively low speed region.

1 is a cross-sectional view in the width direction showing a pneumatic radial tire according to an embodiment of the present invention. (A), (b) is a schematic explanatory drawing which shows the other example of arrangement | positioning of the belt reinforcement layer which concerns on this invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view in the width direction of a pneumatic radial tire according to an example of the present invention. As shown in the figure, the tire of the present invention includes a bead core 1 provided at a pair of left and right bead portions, a carcass ply 2 extending from the crown portion to both bead portions via both side portions, and the crown portion radial outer side of the carcass ply 2. The belt 3 is arranged at least one layer, and the belt reinforcing layer 4 and the tread are arranged on the outer side of the belt 3 in the radial direction of the crown portion.

In the present invention, the belt reinforcing layer 4 extends over the maximum belt width in the tire cross-section equator direction, and the cord constituting the belt reinforcing layer 4 is wound at least one layer substantially in the tire circumferential direction. the value _{S Sho} and the following formula values _{S CL} and belt end vicinity portion 4B in the tire width direction center portion 4A of 177 ° C. dry heat shrinkage value of code layers (I),
0.2 ≦ S _CL / S _Sho <1.0 (I)
It is important to satisfy the relationship expressed by

By using the cord of the belt reinforcing layer, which has a high thermal shrinkage rate at the vulcanization temperature and high thermal shrinkage stress, as the cord of the belt end vicinity 4B that is relatively difficult to be expanded at the time of molding or is susceptible to compression strain, Thus, the cord tension in the belt end vicinity portion 4B can be effectively increased, and the rolling resistance can be suppressed. If S _CL / S _Sho is less than 0.2, the thermal contraction rate in the belt end vicinity 4B becomes excessive, and depending on the elastic modulus of the cord, vulcanization failure or performance degradation, for example, the belt end vicinity 4B and the belt There is a possibility that the interlayer gauge in the product 3 is lost and the running durability is deteriorated. On the other hand, if S _CL / S _Sho is 1.0 or more, it becomes impossible to obtain the effect of reducing rolling resistance, which is the effect of the present invention. In order to obtain the effect of the present invention satisfactorily,
0.2 ≦ S _CL / S _Sho <0.8
It is preferable to satisfy the relationship represented by these.

In the present invention, among the belt layer reinforcing cords constituting the belt reinforcing layer 4, the 177 ° C. dry heat shrinkage value S _{Sho of} the cord disposed in the belt end vicinity 4B is expressed by the following formula (II).
1.3% ≦ S _Sho ≦ 6.0% (II)
It is also important to satisfy the relationship expressed by When the 177 ° C. dry heat shrinkage value S _Sho exceeds 6.0%, the heat shrinkage rate in the belt end vicinity 4B becomes excessive, and depending on the elastic modulus of the cord, vulcanization failure and performance deterioration, for example, The belt end vicinity 4B and the belt 3 have no interlayer gauge in the product, and the running durability may be deteriorated. On the other hand, if it is less than 1.3%, the rolling resistance reduction effect that is the effect of the present invention cannot be sufficiently obtained.

Furthermore, in the present invention, among the belt reinforcement cords constituting the belt reinforcement layer 4, the 177 ° C. dry heat shrinkage value S _{CL of} the cord disposed in the tire width direction central portion 4A is represented by the following formula (III),
1.0% ≦ S _CL <6.0% (III)
It is also important to satisfy the relationship expressed by When the 177 ° C dry heat shrinkage value _SCL is 6.0% or more, the tightening of organic fibers during vulcanization increases, and the interlayer gauge with the steel cord in the center 4A of the tire width direction at the time of becoming a product Can not be secured, and is likely to become the core of early failure when the vehicle is mounted. On the other hand, when it is less than 1.0, when the vehicle is mounted on a vehicle and travels in an actual vehicle, the tire center portion has less suppression force against heat generated by travel, and the traveling tire has a load on the center portion 4A in the tire width direction. Concentrate and cause premature failure. In addition, due to the same phenomenon, the rolling resistance is expected to deteriorate due to an increase in strain in the tire width direction central portion 4A.

Here, the 177 ° C. dry heat shrinkage is a value obtained by performing the dry heat treatment in an oven at 177 ° C. for 30 minutes, measuring the fiber length before and after the heat treatment with a load of 50 g, and using the following formula. .
Dry heat shrinkage (%) = {(Lb−La) / Lb} × 100
However, Lb is the fiber length before heat treatment, and La is the fiber length after heat treatment.

  Further, in the present invention, when the boundary between the tire width direction central portion 4A and the belt end vicinity portion 4B of the belt reinforcing layer 4 is 100, the total width of the belt 3 having the maximum belt width is 100, the belt having the maximum belt width. A region within 15 from the end to the inside in the tire width direction is preferable, and a region of 5 to 12 is more preferable.

  In the present invention, the type of fiber forming the cord of the belt reinforcing layer 4 is not particularly limited, but aliphatic polyamide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aramid, polyketone (PK) It is preferable to be composed of at least one fiber among the fibers. For example, a PK fiber cord may be used in the tire width direction central portion 4A, and an aliphatic polyamide fiber cord may be used in the belt end vicinity portion 4B. As the aliphatic polyamide used for the cord of the belt reinforcing layer 4, 6,6-nylon or 6-nylon is suitable.

  The total fineness per cord of the belt reinforcing layer 4 is preferably in the range of 500 to 5000 dtex, more preferably 1100 to 4500 dtex. If the total fineness is less than 500 dtex, the cord diameter becomes small and the bending rigidity becomes remarkably small, which causes a problem that workability at the time of tire manufacture is deteriorated. On the other hand, if it exceeds 5000 dtex, the thickness of the belt reinforcing layer 4 becomes excessive, and the amount of rubber used increases, so that not only does the tire increase in weight and rolling resistance deteriorates, but also the belt reinforcing layer cords May become narrow, and high-speed durability may be reduced.

  Furthermore, the cord forming the belt reinforcing layer 4 is preferably a dip cord having an elongation at a load of 44 N in the range of 0.5 to 8.0%. In order to not only reduce road noise reliably but also more reliably prevent vulcanization failure during tire molding, the same elongation is 0.5 to 2.0% at the center 4A of the tire width direction, and the belt end In the vicinity 4B, it is practical to be 2.0 to 6.0%.

  Furthermore, the number of cords per unit width (the number of driven-in cords) forming the belt reinforcing layer 4 is preferably 40 to 70/50 mm, and more preferably 45 to 65/50 mm. If the number of cords is less than 40/50 mm, the tagging effect cannot be sufficiently obtained and high-speed durability and road noise are deteriorated. On the other hand, if it exceeds 70/50 mm, not only does the tire weight increase and the rolling resistance deteriorates, but the spacing between the belt reinforcing layer cords becomes narrow and the high-speed durability may be reduced. The number of belt reinforcement layers 4 to be driven need not be constant in the tire width direction, and can be adjusted as necessary.

  Note that the belt reinforcing layer 4 does not have to be composed of at least one full cover type disposed in the equator direction beyond the maximum belt width, as shown in FIG. 2, an edge that reinforces only the belt end vicinity 14B. At least one or more cover types may be arranged. Also in this case, for each of the two belt reinforcing layers 14a and 14b, the material of the organic fiber cord to be used is determined so that the center portion 14A in the tire width direction and the belt end vicinity portion 14B satisfy the above-described conditions. is necessary.

  In the pneumatic radial tire of the present invention, the belt reinforcing layer 4 is particularly limited except that the belt reinforcing layer 4 is provided so as to satisfy the above-described conditions for each of the center part 4A in the tire width direction and the belt end vicinity part 4B. is not. For example, although not shown, an inner liner is usually disposed in the innermost layer of the tire, and a tread pattern is appropriately formed on the tread surface. Further, in the pneumatic tire of the present invention, as the gas filled in the tire, normal or changed oxygen partial pressure, or inert gas such as nitrogen can be used.

  In the tire of the present invention, a cord / rubber composite formed by rubberizing different organic fiber cords satisfying the above conditions is applied to each of the center part 4A in the tire width direction and the belt end vicinity part 4B of the belt reinforcing layer 4. It can be produced by a conventional method. In this case, in particular, a ribbon-like sheet obtained by rubberizing one or more reinforcing elements having a width smaller than the width of the belt reinforcing layer 4 is spirally wound a plurality of times in the tire width direction until a predetermined width dimension is reached. A method of forming the belt reinforcing layer 4 by turning it can be preferably used. By forming the reinforcing layer 4 by spirally winding the ribbon-like sheet, a joint portion does not occur in the tire circumferential direction, and the belt 3 can be uniformly reinforced.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Examples 1-8, Comparative Examples 1-5)
Tires having a tire size of 235 / 55R17 and composed of two layers of belts and one full-cover type belt reinforcing layer which are inclined with respect to the tire circumferential direction and intersect each other were produced according to the specifications shown in Tables 1 and 2 below. The carcass ply includes a fiber cord made of rayon fiber and a coating rubber that covers the rayon fiber, and the belt includes a steel cord and a coating rubber that covers the steel cord. The number of cords used for the belt reinforcing layer was fixed at 50/50 mm without depending on the tire width direction. The boundary between the center in the tire width direction and the vicinity of the belt end was fixed at a position corresponding to 8 from the belt end, with the total width of the belt having the maximum width being 100. In the examples, 6,6-nylon was used as the aliphatic polyamide fiber. Then, rolling resistance and road noise were evaluated for each of the obtained test tires according to the following procedure. A result is combined with Tables 1-3 and shown.

(Conventional example)
A tire was produced in the same manner as in the example except that the central part in the tire width direction and the belt end vicinity were made of the same material (6,6-nylon), and the obtained test tire was evaluated for rolling resistance and road noise. . The results are also shown in Table 1.

(Cord production conditions)
The physical properties of the code are controlled by appropriately changing the dip conditions. As the dip condition, increasing the temperature and tension tends to increase the cord strength and decrease the cord elongation. Further, when the temperature or the exposure time is increased, the cord strength tends to decrease and the elongation of the cord tends to decrease. Therefore, the physical properties of the cord can be controlled as desired by adjusting these dip conditions in an appropriate combination.

(177 ° C dry heat shrinkage)
Each test tire was subjected to a dry heat treatment at 177 ° C. for 30 minutes in an oven, and the fiber length before and after the heat treatment was measured by applying a load of 50 g and obtained by the following formula.
Dry heat shrinkage (%) = {(Lb−La) / Lb} × 100
However, Lb is the fiber length before heat treatment, and La is the fiber length after heat treatment.

(Rolling resistance)
Each test tire was assembled on a rim of size 7.5J-18, filled with an internal pressure of 250 kPa, pressed against a drum surface having a diameter of 1.7 m with a load of 595 kg, and conditioned for 30 minutes at a speed of 80 km / h. After that, coasting was performed from 240 km / h to 18 km / h, and the rolling resistance value was calculated from the required time. The numerical values in the table below are index indications when the rolling resistance value of the tire of the conventional example is set to 100, and the larger the index value, the smaller the rolling resistance.

(Road noise)
Attach each test tire to a sedan type passenger car with a displacement of 2000 cc and ride all four wheels, drive on the road noise evaluation road test course at a speed of 60 km / h, and the center of the backrest of the driver's seat The total sound pressure (decibel) with a frequency of 100 to 500 Hz and 300 to 500 Hz was measured with a sound collecting microphone attached to, and road noise was evaluated from the measured values. The results were calculated so that the road noise of the conventional example was 100, and the exponent value was 100 or more in the (good) direction in which the road noise is reduced.

(durability)
On a drum testing machine, the time until a failure occurred after running at 80 km / h with a specified internal pressure and a specified load was measured. The results are shown in Tables 1 to 3 below using an index with the time until failure of the conventional tire as 100. It shows that it is excellent in durability, so that this index value is large.

  As is apparent from Tables 1 to 3, by adopting the configuration of the present invention, it is possible to obtain a tire that maintains or improves road noise performance while reducing rolling resistance in a relatively low speed region. It was confirmed that there was.

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass ply 3 Belt 4, 14a, 14b Belt reinforcement layer 4A, 14A Tire width direction center part 4B, 14B Belt end vicinity part

Claims (5)

A pair of left and right bead portions; a carcass ply extending from the crown portion to both bead portions through both side portions; a belt disposed at least one layer radially outward of the crown portion of the carcass ply; and a radial direction of the crown portion of the belt In a pneumatic radial tire comprising a belt reinforcing layer and a tread disposed on the outside,
The value _{S Sho} and the following formula values _{S CL} and belt end vicinity portion in the tire width direction center portion of the 177 ° C. dry heat shrinkage value of the code of the belt reinforcing layer (I) ~ (III),
0.2 ≦ S _CL / S _Sho <1.0 (I)
1.3% ≦ S _Sho ≦ 6.0% (II)
1.0% ≦ S _CL <6.0% (III)
A pneumatic radial tire characterized by satisfying the relationship expressed by:   When the total width of the belt having the maximum belt width is 100, the boundary between the central portion of the belt reinforcing layer in the tire width direction and the vicinity of the belt end is defined as 100 toward the inside in the tire width direction from the end of the belt having the maximum belt width. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is 15 or less.   The cord of the belt reinforcing layer is composed of at least one fiber selected from aliphatic polyamide, polyethylene terephthalate, polyethylene naphthalate, aramid, and polyketone fiber, and the total fineness per cord is in the range of 500 to 5000 dtex. The pneumatic radial tire according to claim 1 or 2.   The pneumatic radial tire according to any one of claims 1 to 3, wherein the dip cord of the cord of the belt reinforcing layer has an elongation at a load of 44 N in a range of 0.5 to 8.0%.   The pneumatic radial tire according to any one of claims 1 to 4, wherein the number of cords per unit width of the cord of the belt reinforcing layer is 40 to 70/50 mm.

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