JP2001001724A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stability and controllability, riding comfort against vibration, and noise reduction by reinforcing a side wall portion with two layers of a composite of polyester fiber cords and rubber, and specifying total fineness and middle stretch of the polyester fiber cords. SOLUTION: A folding portion 51 of a carcass 5 extends outward in the radial direction of a tire along a carcass main body 50 with an end 52 thereof disposed between a belt 6 and the carcass main body 50 at a side end region of the belt 6. Accordingly, a two-layered structure composed of polyester fiber cords and rubber is formed in a side wall portion 3, which comprises the carcass main body 50 and folding portion 51. In this case, polyester fiber cords to be utilized have total fineness of 1000 to 2000 dtex and middle stretch of 5.0 to 10.0% under a stress of 19.9 mN/dtex when removed from a tire. With this configuration, stability and controllability as well as noise reduction during running can be compatibly achieved.

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, and more particularly, to a pneumatic radial tire having a low noise level and excellent driving characteristics and ride comfort.

[0002]

2. Description of the Related Art Pneumatic radial tires, especially pneumatic radial tires for passenger cars or light trucks,
A high modulus material is used for the carcass ply so as to improve the steering stability and prevent the unevenness at the joint portion of the carcass ply from adversely affecting the tire side appearance.

[0003] A low modulus carcass ply made of nylon is advantageous for improving the riding comfort and reducing noise, but is disadvantageous in terms of uniformity, steering stability and flat spot characteristics. , Its use has been suppressed. Here, the flat spot is
Deformation, such as plastic deformation, which is likely to occur on the contact surface of the tire after a long period of high-speed running.

[0004]

Here, if a high modulus ply material is used for the carcass, it is advantageous for steering stability and the like, but on the other hand, vibration riding comfort and noise generated during tire running tend to deteriorate. It is difficult to improve both of these performances.

For example, it is possible to use a cord made of polyester fiber having a relatively low modulus by heat treatment for a carcass ply, but this also impairs steering stability during tire running, tire side appearance, and the like. It is difficult to satisfy various performances. It is also conceivable to increase the diameter of the carcass ply cord and apply a heat treatment to the large-diameter cord to reduce the modulus to a relatively low value. It is difficult to improve at the level.

It is also effective to simplify the carcass to one ply as a structure contributing to the lower modulus of the carcass ply. On the other hand, this carcass structure contributes to the reduction of the weight of tires in order to reduce the fuel consumption of automobiles and to the improvement of productivity during tire production. But,
Simplification of the carcass naturally leads to insufficient strength of the side portion of the tire. Therefore, in order to maintain the strength and cut resistance of the side portion, a relatively large-diameter chemical fiber cord, for example, a fineness of 1100 dtex / 2 or more is used. Chemical fiber cords are used.

Similarly, Japanese Patent Application Laid-Open No. Hei 10-236106 discloses a tire in which a carcass is made into one ply. The tire includes a reinforcing layer formed by a cord which is reciprocated in a zigzag manner between the bottom of the belt and the bead along the side of the tire. The arrangement is described to improve steering stability and load durability.

However, in any case, the rigidity of the side wall portion becomes too high, and there is a problem that the riding comfort and the low noise are inferior.

As described above, with the conventional carcass structure, it has been difficult to satisfy all of the steering stability, the riding comfort and the low noise. Therefore, an object of the present invention is to propose a new method for satisfying both of these characteristics.

[0010]

SUMMARY OF THE INVENTION The inventor first studied in detail how to reduce the noise of a pneumatic radial tire. As a result, it was found that the lower the modulus of the carcass ply cord on the inner side of the tire belt in the radial direction, the lower the noise generation level during tire running.
That is, the noise generated from the tire is partly due to the noise generated when the running tire passes over the bumps in the unevenness of various road surfaces, and by lowering the modulus of the carcass ply cord, the energy at the time of riding over the bumps is reduced. It is presumed that the noise was reduced because the noise was easily absorbed.

Here, the method of reducing the modulus of the carcass ply cord is to (1) reduce the modulus of the cord material itself, and (2) reduce the thickness of the cord to substantially reduce the modulus on the radially inner side of the tire belt. (3) It is conceivable to reduce the number of carcass ply cords to be driven to substantially lower the modulus of the tire inside the belt in the radial direction. The method (1) degrades the steering stability of the tire, and the methods (2) and (3) not only degrade the steering stability, but also lacks the strength of the tire side portion. Therefore, the safety factor in terms of strength is also reduced.

In view of the above, the inventors of the present invention have made intensive studies to solve these problems, and by devising the structure of the carcass ply according to the material of the carcass ply of the tire, it has been possible to improve the steering stability of the tire and reduce the tire running noise. Were found to be compatible, and the present invention was completed.

That is, the gist of the present invention is as follows. (1) A carcass body composed of one ply of a rubber-coated cord extending in the radial direction across both bead portions, both sidewall portions, and a crown portion between a pair of bead cores, and the ply around each bead core from the inside of the tire. A pneumatic radial tire having, as a skeleton, a carcass comprising a folded portion which is wound outward and extended outward in the tire radial direction, and at least two layers of belts are arranged radially outward of a crown portion of the carcass; The wall portion is reinforced with at least two layers of a composite made of a polyester fiber cord and rubber, and the polyester fiber cord has a total fineness of 1000 to 2000 dtex,
And 19.9mN / dt of the cord taken out of the tire
A pneumatic radial tire having an intermediate elongation at the time of ex of 5.0 to 10.0%.

(2) The pneumatic radial tire according to the above (1), wherein the composite is a carcass body and a folded portion thereof.

(3) The pneumatic radial tire according to the above (1) or (2), wherein the terminal of the folded portion of the carcass is extended to the crown portion of the carcass.

(4) In the above (1), (2) or (3),
A pneumatic radial tire, wherein the composite is a carcass body and an insert.

(5) The pneumatic radial tire according to (4), wherein the insert is made of the same cord as the carcass ply cord.

(6) The pneumatic radial according to any one of the above (1) to (5), wherein the twist number of the polyester fiber cord is 30 to 70 turns / 10 cm for both the twisting and the lower twisting. tire.

(7) The pneumatic radial tire according to any one of the above (1) to (6), wherein the polyester fiber cord is polyethylene terephthalate or polyethylene-2,6-naphthalate.

(8) The pneumatic radial tire according to any one of the above (1) to (7), wherein the polyester fiber cord is subjected to a heat treatment after an adhesive is applied.

(9) The pneumatic radial tire according to any one of the above (1) to (8), wherein the number of polyester fiber cords to be driven into the crown portion of the carcass is 30 to 60/50 mm. .

[0022]

FIG. 1 illustrates a specific example of a radial tire for a passenger car according to the present invention. The tire has a carcass 5 formed by a single ply of a rubber-coated cord extending in a radial direction across both bead portions 2, both sidewall portions 3 and a crown portion 4 between a pair of bead cores 1, and a tire diameter of a crown portion of the carcass 5. The belt 6 includes at least one layer, two layers in the illustrated example, and a tread 7 disposed radially outward of the belt 6.

The carcass 5 includes a carcass body 50 in which one ply of a polyester fiber cord extending in the radial direction is stretched between the bead cores 1 in a toroidal shape, and both end portions of the carcass body 50 are outside the tire by the bead cores 1. And a folded back portion 51 extending outward in the tire radial direction.

Here, the side wall portion 3 is made of at least two of a composite made of polyester fiber cord and rubber.
It is important that the layers are reinforced. In the example shown in FIG. 1, the folded portion 51 of the carcass 5 is
Along the tire radially outward, and turn back
By arranging the terminal 52 of the belt 51 between the belt 6 and the carcass main body 50 in the side end area of the belt 6, the carcass main body 50 and the folded portion 51 are formed in the side wall portion 3.
A two-layer structure of a composite of polyester fiber cord and rubber consisting of Here, the sidewall portion indicates a region from the flange of the rim to the width end of the belt 6 exposed when the tire is incorporated into a standard rim.

That is, since the tire according to the present invention has a simplified carcass structure consisting of one ply, the modulus of the carcass on the radially inner side of the belt can be reduced, which is particularly advantageous for reducing noise. It is. However, in the simplified carcass structure, the rigidity of the tire side portion tends to be insufficient. In order to compensate for the insufficient rigidity, the sidewall portion 3 has a two-layer structure of a composite. In one example, the carcass body 50
The two-layer structure of the folded portion 51 imparts rigidity to the tire side portion.

As described above, if the rigidity of the tire side portion is too high, ride comfort and low noise performance will be impaired. Need to be examined. As a result, the polyester fiber cord had a total fineness of 1000 to 2000 dtex, and the cord taken out from the tire was 19.9 mN / dtex.
A medium elongation of 5.0 to 10.0% was used.

If the total fineness of the polyester fiber cord is less than 1000 dtex, the strength of the side wall portion is insufficient, and the durability, particularly the cut resistance, is reduced. On the other hand, the total fineness of the cord is 2000 dtex
Exceeding the limit results in excessively high tire side rigidity, which impairs ride comfort. Similarly, if the intermediate elongation of the cord is less than 5.0%, the riding comfort deteriorates, and if it exceeds 10.0%, the steering stability deteriorates and the carcass ply is caused by the joint portion. The unevenness on the outside of the tire becomes large, and the appearance of the tire is impaired.

In particular, as shown in FIG. 1, in a structure in which the folded portion of the carcass is extended to the belt area,
By using the above-mentioned polyester fiber cord, the carcass ply cord inside the belt is made thinner and lower in modulus, and the modulus of the carcass ply cord inside the belt can be made as small as possible as a whole, so that the noise generation level during tire running is extremely low. It becomes possible to suppress to the level.

FIG. 1 shows a structure in which the folded portion of the carcass is extended below the belt. As shown in FIG. 2, the terminal 52 of the folded portion 51 of the carcass 5 is connected to the inside of the side wall portion on the bead portion side. It may be a structure that stops at. However, in this case, it is 5 to 15 mm from the folded portion 51 of the carcass and the terminal 52.
By providing the insert 8 which overlaps by about the length and extends near the radially inner side of the width end of the belt 6, the two-layer structure of the composite body including the insert 8 and the carcass body 50 in the sidewall portion 3 is provided. Is important. At that time, it is preferable to use a ply in which the same specifications as the carcass, that is, the same polyester fiber cords are buried in the rubber with the same number of driving, are applied to the inserts 8 under the application of the polyester fiber cords under the above conditions.

Here, it is preferable that the twist number of the polyester fiber cord is 30 to 70 times / 10 cm for both the upper twist and the lower twist. That is, when the number of twists is less than 30 turns / 10 cm, the modulus of the cord is increased, and the rigidity of the sidewall portion is increased, so that the riding comfort is deteriorated.
On the other hand, if the number of twists exceeds 70/10 cm, the cord may become untwistable, causing the cord to rotate, resulting in tangling, which may make cord production substantially impossible. Further, there is a disadvantage that the modulus of the cord becomes too low, and the steering stability of the tire is deteriorated.

Further, the polyester fiber cord is particularly advantageous when the main component of the skeleton molecular structure of the polymer molecular chain is polyethylene terephthalate or polyethylene naphthalate. Because polyethylene terephthalate and polyethylene naphthalate are produced as general-purpose materials for industrial use, they are advantageous in terms of price, and can be easily used by selecting the thickness of the cord and selecting appropriate heat treatment conditions. There is also an advantage that the performance can be obtained.

At the same time as the application of the adhesive, the polyester fiber cord is subjected to a heat treatment for maintaining the temperature in a temperature range of 230 to 250 ° C. for 80 to 180 seconds, and further, a tension is applied to obtain necessary physical properties. Thereby, the intermediate elongation can be adjusted to the above range.

Here, the treatment of the adhesive can be broadly classified into a two-bath treatment method and a one-bath treatment method. That is, when the treatment is performed in two baths, a treatment with a reactive adhesive is performed first, and then a treatment with a resorcinol-formaldehyde-rubber latex (hereinafter, referred to as RFL) is performed. As a reactive adhesive,
For example, an epoxy type or a blocked isocyanate type can be used. The condition of the treatment with the adhesive is as follows: about 0.5 to 1.5% by weight of the adhesive is attached to the fiber weight, and the fiber is dried at 100 to 150 ° C. for about 2 minutes.
A heat treatment is performed at ~ 250 ° C for 60-80 seconds. At this time, the tension applied to the cord is suitably about 1.6 mN / dtex.

Next, in the treatment with RFL, after adhering 4 to 5% of RFL, holding at 230 to 250 ° C. for 60 to 80 seconds is performed under a tension of about 0.3 mN / dtex.
The polyester fiber cord thus subjected to the adhesive treatment preferably has an intermediate elongation at 19.9 mN / dtex in the range of 5.0 to 10.0.

The one-bath treatment is carried out by adding 2 to the RFL adhesive.
6-bis (2,4-dihydroxyphenylmethyl) -4
A mixture of clophenol, a condensate of sulfur monochloride and resorcinol, a mixture of resorcinol-formalin condensate, and the like is used as an adhesive. In this case, about 4 to 6% by weight per fiber weight is applied, dried at 150 to 180 ° C. for 2 minutes, and kept at 230 to 250 ° C. for 60 to 80 seconds.
Perform under a tension of about 1.6 mN / dtex.
Hold at 30-250 ° C for 60-80 seconds at 1.6 mN / dtex
By carrying out under a certain degree of tension, a desired cord can be obtained.

It is advantageous that the number of the polyester fiber cords to be driven into the carcass crown is 30 to 60/50 mm. In other words, if the number of driving of the polyester fiber cord is less than 30/50 mm, both the strength and rigidity of the carcass side portion are insufficient, resulting in a decrease in cut resistance due to insufficient strength and a decrease in steering stability due to a decrease in rigidity. On the other hand, if the number of shots exceeds 60 / 50mm,
The intervals between the cords are too small, and the cords may overlap in some parts. Depending on the level of the middle elongation of the cords, the rigidity becomes too high, and the ride comfort is deteriorated.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A code having the specifications shown in Tables 1 and 2 was applied to a composite (carcass and insert) of a radial tire for a passenger car having the structure shown in FIGS.
70R14 or 205 / 70R15 tires were prototyped. Also,
The first belt is disposed on the carcass 5 in such a direction that a steel cord having a 1 × 3 × 0.30 (mm) structure is inclined at an angle of 68 ° to the left with respect to the equatorial plane of the tire. The second belt is arranged so that the steel cord is inclined at an angle of 68 ° to the right with respect to the equatorial plane of the tire. The number of belt cords to be driven was 30/50 mm.

The cord applied to the composite was prepared as follows. First, using a polyethylene terephthalate raw yarn 840 dtex, apply a twist of 49 times / 10 cm and twist the two yarns, and apply a twist of 49 times / 10 cm in the opposite direction (primary twist 49Z direction, upper twist 49S direction), and a twin twist cord 840 dtex. / 2 was produced. Next, an interdigital tire cord fabric was manufactured by a usual method so that the number of shots was 33/5 cm. Here, the total strength of the carcass was appropriately adjusted so that the total strength of the carcass became equal to that of the comparative example so that the number of shots could be compared. The thus obtained tire cord fabric was subjected to an adhesive application and a heat treatment so as to have predetermined physical properties. That is, the processing temperature of the heat setting zone and the normalizing zone is set to 240 to
250 ° C., the treatment time was 45 to 80 seconds in each zone, and the cord tension in the heat setting zone was 2.65 mN /
dtex ~ 13.3 mN / dtex and the cord tension of the normalizing zone are set to 0.53 mN / dtex ~
The treatment was carried out by adjusting to a range of 0.88 mN / dtex.

The tire cord fabric which has been subjected to the adhesive and heat-treated is topped with rubber according to a usual tire processing method, and cut into a predetermined width in accordance with the tire size to obtain a carcass ply or an insert material. Next, after bonding the carcass ply and the insert on the forming drum, the side rubber, two steel belts, and the tread rubber are sequentially placed, and vulcanization and post cure inflation are performed under predetermined conditions to produce a prototype tire. Produced.

The cord used in the comparative example was made of 1100 dtex of polyester tire cord, and was twisted by 47 twists of Z twist and 47 twists of S twist, and was additionally twisted to give a double twisted cord ( 1100dtex / 2)
Was prepared. Next, the interwoven fabric was produced in the same manner as the cord of the invention example, so that the number of shots was 50 pieces / 5 cm. An adhesive was applied and a heat treatment was performed thereon so as to have predetermined physical properties. The heat treatment conditions were changed to the hot zone of 4.0 mN / dtex and the normalizing zone of 2.0 mN / dtex only for the cord tension at the time of the heat treatment in comparison with the invention example, and a cord having a high modulus was obtained. In addition, cords of other thicknesses and materials of the invention examples and the comparative examples were produced by adjusting the cord tension at the time of applying an adhesive and heat-treating them in a similar manner so as to have predetermined physical properties.

With respect to the tire thus obtained, the running noise, vibration riding comfort, and steering stability of the tire were examined. Table 1 also shows the results of these surveys. The elongation of the cord was determined by carefully scraping off excess rubber adhering around the cord taken out of the carcass or insert of the tire with scissors and then using an autograph according to JIS L1017 at room temperature (25 ± 2 ° C.). ) And pull 1
Elongation (%) under a load of 9.9 mN / dtexdtex was determined.

The number of dtex is the original yarn dtex before twisting.
Was used. The reason for this is to avoid complication caused by a change in dtex based on a change in cord length due to twisting, bonding, shrinkage during vulcanization of the tire, and the like. For example, 10
For a 200dtex two-strand cord, this is 2000d
It was displayed as tex.

Here, the tire running noise was measured by JAS
A test on a single tire base was performed in accordance with O (Automobile Engineering Society) C606-81. The outline of the test according to JASO C606-81 is shown below. In this test, a 3 m diameter with a flat surface and a coarse-grained surface with a high coefficient of friction was used as a substitute road surface.
A testing machine equipped with a drum and a tire loading device was used. The test was performed in a test room equipped with soundproofing so that noise from the tester and the outside was minimized. The tire load and the air pressure were the maximum load specified in JIS D 4202 and the air pressure corresponding thereto. Rim is also JIS D
The standard rim specified in 4202 was used.

Then, a microphone was installed at a position 1 m away from the tire, and the preparatory running was performed at 60 km / h for 30 minutes.
/ H, 80 km / h, and 100 km / h, the noise level (dB (A)) was measured, and the average noise level (d
B (A)) was calculated.

The vibration comfort is 2000 mm in outer diameter.
Iron projections (upper bottom 19 mm, lower bottom 3
8mm, height 9.5mm), internal pressure 166.7k
The test tire adjusted to pa was loaded with a load of 3920N,
After preliminarily running at a speed of 80 km / h for 20 minutes, readjust the internal pressure at 166.7 kpa under no load, adjust the speed to 20 km / h, adjust the load 3920 N, and thereafter increase the speed every 5 km / h At each speed, an average waveform of the variation in the load on the fixed shaft of the tire at the time of the overshoot of the protrusion is determined, and the difference between the peak maximum value and the peak minimum value of the determined waveform (pp
Value) was calculated.

The direction in which the load on the tire fixed shaft fluctuates when moving over the protrusion is the direction of travel of the tire (front and rear springs).
In the speed range of ４０40 km / h, the so-called front-rear splash constant is maximum. Therefore, the pp value (N) in this speed range was calculated. In addition, the indexing was performed using the control tire of Comparative Example 1 as 1
00 was obtained by the following equation. Index = 100 ÷ [100 × ｛(Control tire p−
(p value)-(test tire pp value) / (control tire pp value)] This index is such that the smaller the pp value is, the larger the exponent is. It shows that the comfort is good.

In the steering stability test, each tire was mounted on a standard rim, adjusted to an air pressure corresponding to the maximum load capacity, and then mounted on a passenger car having a displacement of 2500 ml.
Sensory tests were performed on items such as straight running stability, turning stability, and handling properties when traveling at a speed of 00 km / hour. The evaluation is indicated by an index using the score in Comparative Example 1 as a reference 100, and the higher the numerical value, the higher the performance.

[0048]

[Table 1]

[0049]

[Table 2]

As shown in Tables 1 and 2, Invention Examples 1 to 7
By reducing the modulus of the tire carcass ply cord as shown in FIG. 1 to make the arrangement of the ply cord an envelope structure, or by providing inserts as shown in Invention Examples 8 to 10, the sidewall portion is formed of two layers. It can be seen that the tire with the reinforced structure does not decrease the strength of the tire side part (without lowering the carcass safety factor) and drastically lowers the noise level when running while maintaining the same or higher steering stability . Similarly, the vibration ride comfort index was equal to or higher than the above. On the other hand, as shown in Comparative Examples 2 and 3, it can be seen that simply increasing the intermediate elongation of the cord and decreasing the modulus of the carcass cord does not not only lower the noise level but also greatly deteriorates the steering stability.

[0051]

According to the present invention, it is possible to provide a high-performance tire in which various performances are highly balanced because the steering stability, the riding comfort and the low noise level are all improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section in the width direction of a tire according to the present invention.

FIG. 2 is a diagram showing a cross section in the width direction of another tire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead core 2 Bead part 3 Side wall part 4 Crown part 5 Carcass 50 Carcass body 51 Folding part 52 Terminal 6 Belt 7 Carcass 8 Insert

Claims (9)

[Claims] 1. A carcass body composed of one ply of a rubber-coated cord extending in a radial direction across both bead portions, both sidewall portions, and a crown portion between a pair of bead cores; A pneumatic radial tire in which at least two layers of belts are arranged radially outside of a crown portion of the carcass, with a carcass comprising a folded portion extending from the inside to the outside and extending outward in the tire radial direction as a skeleton, The sidewall portion is reinforced with at least two layers of a composite made of a polyester fiber cord and rubber, and the polyester fiber cord has a total fineness of 1,000 to 2,000.
dtex and 19.9 of the cord taken out of the tire
A pneumatic radial tire having an intermediate elongation at mN / dtex of 5.0 to 10.0%. 2. The pneumatic radial tire according to claim 1, wherein the composite is a carcass body and a folded portion thereof. 3. The pneumatic radial tire according to claim 1, wherein a terminal of the turn-back portion of the carcass is extended to a crown portion of the carcass. 4. The pneumatic radial tire according to claim 1, wherein the composite is a carcass body and an insert. 5. The pneumatic radial tire according to claim 4, wherein the insert is made of the same cord as the carcass ply cord. 6. The method according to claim 1, wherein
The pneumatic radial tire, wherein the number of twists of the polyester fiber cord is 30 to 70 turns / 10 cm for both the first twist and the second twist. 7. The method according to claim 1, wherein
A pneumatic radial tire, wherein the polyester fiber cord is polyethylene terephthalate or polyethylene-2,6-naphthalate. 8. The method according to claim 1, wherein
A pneumatic radial tire, wherein the polyester fiber cord is subjected to a heat treatment after adhering an adhesive. 9. The method according to claim 1, wherein
A pneumatic radial tire, wherein the number of driving of polyester fiber cords in a carcass crown is 30 to 60/50 mm.