JP2010126074A - Pneumatic radial tire for passenger car, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a passenger car, capable of improving the lightweight property, economy and high-speed durability while ensuring the fatigue resistance, and to provide a method for manufacturing the same. <P>SOLUTION: In the pneumatic radial tire for the passenger car, at least one carcass layer 4 is stretched between a pair of right and left bead parts 3, 3, and at least two belt layers 7 including reinforcing cords inclined with respect to the tire circumferential direction, and a belt reinforcing layer 8 including reinforcing cords circulated in the tire circumferential direction are arranged on the outer circumferential side of the carcass layer 4 at a tread part 1, a flat single twist cord C in which the total size is in a range of 900-5,000 dtex, and fiber bundles including thermoplastic multi-filaments are twisted in one direction, its sectional shape is flat and the ratio a/b of the major diameter a to the short diameter b is in a range of 1.1-3.5 is used for the reinforcing cord of the belt reinforcing layer 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire for a passenger car in which a belt reinforcing layer including a reinforcing cord that circulates in the tire circumferential direction is arranged on the outer peripheral side of a carcass layer in a tread portion, and a method for manufacturing the same, and more particularly, ensuring fatigue resistance. The present invention relates to a pneumatic radial tire for passenger cars and a method for manufacturing the same, which can improve lightness, economy, and high-speed durability.

  Conventionally, in passenger car pneumatic radial tires that require high-speed durability, in addition to at least two belt layers including reinforcing cords that are inclined with respect to the tire circumferential direction on the outer peripheral side of the carcass layer in the tread portion, A belt reinforcing layer including a reinforcing cord that circulates in the tire circumferential direction is disposed. As a reinforcing cord for such a belt reinforcing layer, a polyamide fiber cord is preferably used.

Normally, the polyamide fiber cord used for the belt reinforcing layer is a so-called double twisted cord in which a polyamide fiber bundle is twisted and a plurality of lower twisted yarns are bundled and an upper twist is applied in the opposite direction to the lower twisted yarns. is there. This double-twisted cord has good shape stability and excellent workability, but as the cord diameter increases, the thickness of the belt reinforcing layer increases, the tire weight increases, and the lower twisting process In addition, since a two-stage process called an upper twisting process is required, there is a disadvantage that the cost is inferior. As a method for solving these disadvantages, it has been proposed to use a single twisted cord having a specific twist coefficient as the reinforcing cord of the belt reinforcing layer (see, for example, Patent Documents 1 to 3). However, the single twisted cord has a problem that it is inferior in fatigue resistance due to poor convergence of the filament.
JP 2002-154304 A Japanese Patent No. 2005-239069 Japanese Patent No. 2007-191832

  An object of the present invention is to provide a pneumatic radial tire for a passenger car and a method for manufacturing the same that can improve lightness, economy, and high-speed durability while ensuring fatigue resistance.

  In order to achieve the above object, a pneumatic radial tire for a passenger car according to the present invention includes at least one carcass layer mounted between a pair of left and right bead portions, and the outer circumferential side of the carcass layer in the tread portion with respect to the tire circumferential direction. In a pneumatic radial tire for a passenger car in which at least two belt layers including a reinforcing cord inclined and a belt reinforcing layer including a reinforcing cord that circulates in the tire circumferential direction are disposed, the total fineness is used as the reinforcing cord of the belt reinforcing layer. Is a single twisted cord obtained by twisting a fiber bundle containing a thermoplastic multifiltrate in one direction, the cross-sectional shape thereof is flat, and the major axis a and minor axis b thereof are in the range of 900 dtex to 5000 dtex. A flat piece twisted cord having a ratio a / b in a range of 1.1 to 3.5 is used.

  On the other hand, in the method for producing a pneumatic radial tire for passenger cars of the present invention for achieving the above object, the total fineness is in the range of 900 dtex to 5000 dtex, and a fiber bundle containing a thermoplastic multifiltrate is twisted in one direction. After processing the flat twisted cord in which the ratio a / b of the major axis a to the minor axis b is in the range of 1.1 to 3.5 by shaping the single twisted cord so that the cross-sectional shape becomes flat by heating, A strip material covered with rubber is formed using the flat twisted cord as a reinforcing cord, a belt reinforcing layer is formed by circularly circulating the strip material, and at least one carcass layer is mounted between a pair of left and right bead portions. And at least two belt layers including reinforcing cords inclined with respect to the tire circumferential direction on the outer peripheral side of the carcass layer in the tread portion, and a belt in which the belt reinforcing layer is disposed. Molding the Ntaiya, it is characterized in that vulcanizing the green tire.

  In the present invention, as a reinforcing cord of the belt reinforcing layer, by using a flat piece twisted cord in which the total fineness and the flatness ratio a / b are defined in a specific range, the convergence property of the filament in the single twisted cord is enhanced and the belt reinforcement Since the distortion of the cord surface when bending deformation occurs in the layer is reduced, the fatigue resistance of the belt reinforcing layer can be improved. Moreover, the flat piece twisted cord is advantageous in terms of lightness because it can suppress an increase in the thickness of the belt reinforcing layer even if the total fineness is increased. In addition, the flat piece twisted cord is easier to manufacture than the double twisted cord and is more economical, and contributes to the improvement of high-speed durability when used in the belt reinforcing layer. Therefore, by using the flat piece twisted cord for the belt reinforcing layer, it is possible to improve lightness, economy, and high-speed durability while ensuring fatigue resistance of the pneumatic radial tire for passenger cars.

In this invention, it is preferable that the twist coefficient K represented by the following Formula (1) of the flat piece twisted cord which comprises a belt reinforcement layer exists in the range of 800-1200. Thereby, the effect which improves lightweight property, economical efficiency, and high-speed durability can be fully acquired, ensuring fatigue resistance.
K = T√D (1)
T: Number of twisted cords (times / 10cm)
D: Total fineness of cord (dtex)

  Moreover, it is preferable that ratio a / b of the major axis a of the flat piece twisted cord which comprises a belt reinforcement layer, and the minor axis b exists in the range of 1.2-3.0. Thereby, fatigue resistance and light weight can be improved effectively.

  The flat piece twist cord constituting the belt reinforcing layer is treated with an adhesive (RFL) composed of a mixture of resorcin / formaldehyde initial condensate (RF) and rubber latex (L), and rubber latex is made of vinylpyridine, styrene, It contains 75% by weight or more of butadiene terpolymer latex, and the weight ratio (L / RF) of the solid content of the rubber latex to the solid content of the resorcin / formaldehyde initial condensate is in the range of 100/20 to 100/30. preferable. Thus, by using vinyl pyridine / styrene / butadiene / terpolymer latex having high heat resistance and high cohesive force as rubber latex and increasing the amount of RFL resin, a flat piece twist cord having excellent durability can be obtained. .

  The twisting direction of the flat piece twisted cord constituting the belt reinforcing layer is preferably the same as the inclination direction of the reinforcing cord of the belt layer adjacent to the belt reinforcing layer with respect to the tire circumferential direction. By adopting such an arrangement, it becomes possible to enhance the price tear of the tire and effectively suppress the steering wheel flow on the general road surface.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention, where 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A single carcass layer 4 including a plurality of reinforcing cords extending in the tire radial direction is mounted between the pair of left and right bead portions 3 and 3, and an end portion of the carcass layer 4 extends around the bead core 5 from the inside of the tire. It is folded outside. A bead filler 6 made of a rubber composition having a high hardness is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the carcass layer 4. The JIS-A hardness of the bead filler 6 is desirably in the range of 65 to 97.

  A plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. A belt reinforcing layer 8 formed by winding a reinforcing cord in the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7 in order to enhance high-speed durability. The belt reinforcing layer 8 preferably has a jointless structure in which at least one reinforcing cord is aligned and rubber-coated strip material is continuously wound substantially at 0 ° with respect to the tire circumferential direction. .

  The belt reinforcement layer 8 can select the arrangement | positioning area | region suitably according to the speed range of a tire. For example, the belt reinforcing layer 8 is disposed over the entire belt layer 7, the belt reinforcing layer 8 is disposed only in both shoulder regions corresponding to both widthwise ends of the belt layer 7, or both widthwise ends of the belt layer 7 It is also possible to have two belt reinforcing layers 8 in both shoulder regions corresponding to 1 and one belt reinforcing layer 8 in the center region between them. In the center region, the belt reinforcing layer 8 may be disposed between the carcass layer 4 and the belt layer 7.

  In the pneumatic radial tire, as a reinforcing cord of the belt reinforcing layer 8, the total fineness is in a range of 900 dtex to 5000 dtex, and a single twisted cord obtained by twisting a fiber bundle containing a thermoplastic multifillant in one direction, A flat piece twisted cord C having a flat cross-sectional shape and a ratio a / b of the major axis a to the minor axis b in the range of 1.1 to 3.5 is used. The flat piece twisted cord C is preferably applied to all the reinforcing cords constituting the belt reinforcing layer 8, but may be applied to only a part of the reinforcing cords.

  2 and 3 are cross-sectional views each illustrating a flat piece twisted cord. The flat piece twisted cord C may have an elliptical cross-sectional shape as shown in FIG. 2, or may have a flat shape as shown in FIG. These flat piece twisted cords C are embedded in the belt reinforcing layer 8 so that the major axis direction is the surface direction of the belt reinforcing layer 8. That is, the thickness of the belt reinforcing layer 8 is determined based on the minor axis b of the flat piece twisted cord C.

  Thus, by using the flat piece twisted cord C as the reinforcing cord of the belt reinforcing layer 8, the convergence of the filament in the piece twisted cord can be enhanced. In addition, when the belt reinforcing layer 8 is bent, the flat shape is small and the cord surface is less distorted. Therefore, the fatigue resistance of the belt reinforcing layer 8 can be improved. Moreover, since the flat piece twisted cord C can suppress an increase in the thickness of the belt reinforcing layer 8 even if the total fineness is increased, it is advantageous in terms of lightness. Therefore, by using the flat piece twisted cord C for the belt reinforcing layer 8, it is possible to improve lightness, economy, and high-speed durability while ensuring fatigue resistance of the pneumatic radial tire for passenger cars.

  The flat piece twisted cord C has a total fineness in the range of 900 dtex to 5000 dtex. If the total fineness is less than 900 dtex, the number of cords driven in the belt reinforcing layer 8 increases and the productivity deteriorates. On the other hand, if it exceeds 5000 dtex, the number of cords driven decreases and the productivity is improved. Since the twisted cord C becomes thicker and the belt reinforcing layer 8 becomes thicker, the lightness is reduced. From the viewpoint of productivity and lightness, it is desirable that the range be 1400 dtex to 4000 dtex.

  The flat piece twisted cord C is obtained by twisting a fiber bundle containing a thermoplastic multifillant in one direction. Of course, all the fibers contained in the fiber bundle may be a thermoplastic multifillant. If the flat piece twisted cord C does not contain a thermoplastic multifillant, it is difficult to flatten by heating. Examples of the multifilament having no thermoplasticity include aramid fiber and rayon fiber. As the thermoplastic multifillant, fibers such as nylon 66, nylon 46, polyethylene terephthalate, and polyethylene naphthalate may be used. The single yarn thickness of these fibers is preferably in the range of 5 dtex to 8 dtex in order to facilitate flattening. If the single yarn is too thin, the filament strength is reduced, and filament breakage is likely to occur when the tire is used. Conversely, if the yarn is too thick, it tends to be damaged during molding, resulting in reduced fatigue resistance. In particular, nylon 66 or nylon 46 is preferably used in terms of adhesiveness.

  In the flat piece twisted cord C, the ratio a / b between the major axis a and the minor axis b is in the range of 1.1 to 3.5. If the aspect ratio a / b is less than 1.1, the effect of reducing the weight is reduced, and at the same time, the effect of improving fatigue resistance is reduced. Conversely, if the ratio is more than 3.5, the filament is locally damaged during molding. Since it becomes easy, fatigue resistance falls. In particular, the aspect ratio a / b is preferably in the range of 1.2 to 3.0. The major axis “a” and the minor axis “b” of the flat piece twisted cord C are dimensions measured at the tire meridian section when the belt portion including the belt reinforcing layer 8 is cut along the tire meridian with a diamond cutter.

In the flat piece twisted cord C, the twist coefficient K represented by the following formula (1) is preferably in the range of 800 to 1200.
K = T√D (1)
T: Number of twisted cords (times / 10cm)
D: Total fineness of cord (dtex)

 By prescribing the twist coefficient K in this way, it is possible to sufficiently obtain the effect of improving lightness, economy, and high-speed durability while ensuring fatigue resistance. Here, when the twisting coefficient K is less than 800, the convergence of the filament in the single twisted cord is lowered, so that it becomes difficult to control the flattening ratio in particular during flattening, and at the same time, the filaments easily open. Therefore, the adhesive layer is easily broken. On the other hand, if the twist coefficient is too small, the fatigue resistance deteriorates and the durability of the tire decreases. On the other hand, when the twisting coefficient K exceeds 1200, the untwisting torque of the cord increases and the cord is likely to rotate. Therefore, the cord is apt to be twisted in the belt reinforcing layer 8, and the cord breaks easily at the twisted portion. Become. Moreover, the rotation of the cord also deteriorates the workability at the time of manufacturing the tire. Furthermore, if the twisting coefficient is too large, the elastic modulus of the cord is lowered, so that the effect of improving the high-speed durability is lowered, or the convergence by twisting becomes too high, and a sufficient flat ratio cannot be obtained. As a result, the cord thickness increases and the weight reduction effect also decreases.

  The flat piece twisted cord C is preferably treated with an adhesive (RFL) made of a mixture of resorcin / formaldehyde initial condensate (RF) and rubber latex (L). Here, the rubber latex contains 75% by weight or more of vinylpyridine / styrene / butadiene / terpolymer latex, and the weight ratio (L / RF) of the solid content of the rubber latex to the solid content of the resorcin / formaldehyde initial condensate is 100. It shall be in the range of / 20-100 / 30. In this way, vinyl pyridine styrene butadiene terpolymer latex, which has higher heat resistance and cohesion than natural rubber and SBR, is used as the rubber latex, and the amount of RFL resin is increased to increase the inter-filament between high pressure treatments. It is possible to suppress a decrease in adhesiveness and a variation between filaments. As a result, a flat piece twisted cord having excellent durability can be obtained.

  FIG. 4 shows an essential part of the belt portion extracted from the pneumatic radial tire according to the embodiment of the present invention. In FIG. 4, the flat piece twisted cord C is depicted to be relatively thick for easy understanding. As shown in FIG. 4, the twist direction of the flat piece twisted cord C constituting the belt reinforcing layer 8 is the same as the inclination direction of the reinforcing cord C ′ of the belt layer 7 adjacent to the belt reinforcing layer 8 with respect to the tire circumferential direction. Has been. That is, when the reinforcing cord C 'of the belt layer 7 is downwardly inclined as shown in the drawing, the flat piece twisted cord C of the belt reinforcing layer 8 is S-twisted. Further, when the reinforcing cord C ′ of the belt layer 7 is inclined downward to the left, the flat piece twisted cord C of the belt reinforcing layer 8 is Z-twisted.

  The flat piece twisted cord C is stronger in the rotation of the cord itself than the double twisted cord. Therefore, it is possible to enhance the price tear by aligning the twisting direction of the flat piece twisted cord C with the orientation direction of the reinforcing cord C ′ of the belt layer 7 adjacent to the belt reinforcing layer 8, and handle flow on a general road surface. Can be effectively suppressed. For example, when left-hand traffic is assumed, the road surface is inclined so as to descend from the center toward the left side, and the handle flow toward the left side tends to occur, so the outermost belt layer is arranged to be lowered to the right. In this case, the flat piece twisted cord C of the belt reinforcing layer 8 is S twisted. When right-hand traffic is assumed, the configuration is the reverse of the above. Moreover, when the orientation direction of the fiber filament of the flat piece twisted cord C and the belt cord is the same as described above, the effect of reducing the interlaminar shear between the belt layer 7 and the belt reinforcing layer 8 and improving the durability is also achieved. I can expect.

  Next, the manufacturing method of the pneumatic radial tire mentioned above is demonstrated. First, a flat piece twisted cord C used for the belt reinforcing layer 8 is prepared prior to the tire molding step. That is, a single twisted cord obtained by twisting a fiber bundle containing a thermoplastic multifillant in one direction with a total fineness in a predetermined range is molded with a heating and pressing roll so that the cross-sectional shape is flat, and further a cooling roll The flat piece twisted cord C in which the ratio a / b of the major axis a to the minor axis b is in a predetermined range is processed. Here, it is preferable that the heating temperature is 180 ° C. or higher, and the mold is cooled with the fiber glass transition temperature or less immediately after molding with a heating and pressurizing roll in view of shape retention. The flat shape can be set as appropriate based on the cord tension and the pressurizing condition during pressurization.

  Next, one or a plurality of flat piece twisted cords C are aligned and covered with rubber to form a strip material. In the tire molding process, a belt reinforcing layer is formed by circularly wrapping a strip material including a flat piece twisted cord C as a reinforcing cord, and at least one carcass layer is mounted between a pair of left and right bead portions and a tread. A green tire is formed in which at least two belt layers including a reinforcing cord that is inclined with respect to the tire circumferential direction and the belt reinforcing layer are arranged on the outer peripheral side of the carcass layer in the portion. After forming the green tire in this way, the green tire is vulcanized in a mold.

  When the flat piece twisted cord C is treated with an adhesive made of a mixture of resorcin / formaldehyde initial condensate and rubber latex, the piece twisted cord is subjected to an adhesion treatment after the piece twisting step. Here, the content of vinyl pyridine / styrene / butadiene / terpolymer latex in the rubber latex is 75% by weight, and the weight ratio of the solid content of the rubber latex to the solid content of the resorcin / formaldehyde precondensate is 100/20 to 100. By setting the ratio to / 30, even if the single twisted cord is subjected to die-molding by heating in the next step, it is possible to suppress a decrease in adhesion between filaments and a variation between filaments.

  A two-layer belt layer having a tire size of 205 / 55R16 and including a reinforcing cord inclined with respect to the tire circumferential direction on the outer peripheral side of the carcass layer in the tread portion, with one carcass layer mounted between the pair of left and right bead portions. In a pneumatic radial tire in which a belt reinforcing layer including a reinforcing cord that circulates in the tire circumferential direction is used, a single twisted cord is used as a reinforcing cord for the belt reinforcing layer, and the material of the single twisted cord, the cord structure, the total fineness, Driving density (lines / 50 mm), major axis a, minor axis b, flatness ratio, number of twists (times / 10 cm), twist coefficient K, blending of adhesive, and reinforcing cord of outer belt layer adjacent to belt reinforcing layer The pneumatic radial tires of Comparative Examples 1 to 4 and Examples 1 to 10 in which the inclination directions of the tires were set as shown in Tables 1 and 2 were manufactured.

  In addition, the major axis a and the minor axis b of the single twisted cord are obtained by cutting the belt portion including the belt reinforcing layer with a diamond cutter along the tire meridian, and measuring the dimension of the cord section in the tire meridian section at ten locations. The average value is obtained.

  The composition of the adhesive is as shown in Table 3. As shown in Table 3, the weight ratio of vinylpyridine / styrene / butadiene / terpolymer latex (Vp) to natural rubber latex (NR), and the solid content of the rubber latex (L) and the resorcin / formaldehyde initial condensate ( RF), two types of adhesives A and B having different weight ratios with the solid content were prepared.

  These test tires were evaluated for lightness, high-speed durability, fatigue resistance, and handle flow by the following evaluation methods, and the results are also shown in Tables 1 and 2.

Lightweight:
The weight of the belt reinforcing layer of each test tire was measured. The evaluation result was shown by the index | exponent which sets Comparative Examples 1-3 to 100. Comparative Example 1 is a reference for Example 1, Comparative Example 2 is a reference for Example 2, and Comparative Example 3 is a reference for Examples 3 to 10 and Comparative Example 4. A smaller index value means a lighter weight.

High speed durability:
For each test tire, after carrying out a high-speed durability test in accordance with JIS D4230, the running test is continued, the speed is increased by 8 km / h every 30 minutes, and the running distance until a failure occurs in the tire is determined. Measured. The evaluation result was shown by the index | exponent which sets Comparative Examples 1-3 to 100. Comparative Example 1 is a reference for Example 1, Comparative Example 2 is a reference for Example 2, and Comparative Example 3 is a reference for Examples 3 to 10 and Comparative Example 4. Higher index values mean better high-speed durability.

Fatigue resistance:
Each test tire is mounted on a test vehicle with a rim size of 16 × 6 · 1/2 J wheel, and the air pressure is 240 kPa. The asphalt pavement has a radius of 7.5 mm and a lateral acceleration of 0. After running repeatedly in a right turn and a left turn so as to be 8 ± 0.1 G, the tread rubber of each test tire was peeled over the entire circumference, and the number of cord breaks in the belt reinforcing layer was measured. The evaluation result was shown by the index | exponent which sets the comparative examples 1-3 to 100 using the reciprocal number of the measured value. Comparative Example 1 is a reference for Example 1, Comparative Example 2 is a reference for Example 2, and Comparative Example 3 is a reference for Examples 3 to 10 and Comparative Example 4. A larger index value means better fatigue resistance.

Handle flow:
Each test tire is assembled to a wheel with a rim size of 16 × 6 · 1/2 J and mounted on the test vehicle. The air pressure is 240 kPa, and the road surface is inclined at a slope of 1 ° toward the left side of the vehicle at a speed of 50 km / h. Then, the lateral flow amount of the vehicle was measured when the vehicle traveled for 100 m. The evaluation result was shown by the index | exponent which sets Comparative Examples 1-3 to 100. Comparative Example 1 is a reference for Example 1, Comparative Example 2 is a reference for Example 2, and Comparative Example 3 is a reference for Examples 3 to 10 and Comparative Example 4. A smaller index value means less handle flow.

＊１：スミカノール７００（７５％）、住友化学（株）製
＊２：Ｎｉｐｏｌ２５１８ＦＳ（４０％）、日本ゼオン（株）製
＊３：天然ゴムラテックス（６０％）

* 1: Sumikanol 700 (75%), manufactured by Sumitomo Chemical Co., Ltd. * 2: Nipol 2518FS (40%), manufactured by Nippon Zeon Co., Ltd. * 3: Natural rubber latex (60%)

  As is clear from Table 1, the tire of Example 1 was excellent in lightness, fatigue resistance, and high-speed durability in comparison with Comparative Example 1. In comparison with Comparative Example 2, the tire of Example 2 was superior in lightness, fatigue resistance, and high-speed durability. In comparison with Comparative Example 3, the tires of Examples 3 to 5 were excellent in lightness, fatigue resistance, and high-speed durability. In the tire of Comparative Example 4, since the aspect ratio a / b was too large, fatigue resistance and high-speed durability were deteriorated.

  Further, as apparent from Table 2, the tires of Examples 6 to 10 are superior in lightness, fatigue resistance, and high-speed durability in comparison with Comparative Example 3, and the effects thereof are remarkable. .

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention. It is sectional drawing which shows an example of a flat piece twisted cord. It is sectional drawing which shows the other example of a flat piece twisted cord. It is a top view which extracts and shows the principal part of the belt part in the pneumatic radial tire which consists of an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer C Flat piece twisted cord

Claims (10)

  At least one carcass layer is mounted between the pair of left and right bead portions, and at least two belt layers including a reinforcing cord inclined to the tire circumferential direction on the outer circumferential side of the carcass layer in the tread portion and the tire circumferential direction In a pneumatic radial tire for a passenger car in which a belt reinforcing layer including a reinforcing cord that circulates is disposed, a fiber bundle having a total fineness in the range of 900 dtex to 5000 dtex as a reinforcing cord of the belt reinforcing layer and including a thermoplastic multifiltrant Is a single twisted cord in which the cross-sectional shape is flat and the ratio a / b of the major axis a to the minor axis b is in the range of 1.1 to 3.5 A pneumatic radial tire for passenger cars, characterized by using a twisted cord. 2. The pneumatic radial tire for a passenger car according to claim 1, wherein the twist coefficient K represented by the following formula (1) of the flat piece twisted cord constituting the belt reinforcing layer is in a range of 800 to 1200. 3.
K = T√D (1)
T: Number of twisted cords (times / 10cm)
D: Total fineness of cord (dtex)   The ratio a / b between the major axis a and the minor axis b of the flat piece twisted cord constituting the belt reinforcing layer is in the range of 1.2 to 3.0. Pneumatic radial tires for passenger cars.   The flat piece twist cord constituting the belt reinforcing layer is treated with an adhesive made of a mixture of resorcin / formaldehyde initial condensate and rubber latex, and the rubber latex is made of vinylpyridine / styrene / butadiene / terpolymer latex. The weight ratio of the solid content of the rubber latex and the solid content of the resorcin / formaldehyde initial condensate is in the range of 100/20 to 100/30. A pneumatic radial tire for passenger cars according to the above.   The twist direction of the flat piece twisted cord constituting the belt reinforcing layer is the same direction as the inclination direction of the reinforcing cord of the belt layer adjacent to the belt reinforcing layer with respect to the tire circumferential direction. A pneumatic radial tire for a passenger car according to any one of the above.   The long diameter a and the short diameter b are formed by casting a single twisted cord in which the total fineness is in the range of 900 dtex to 5000 dtex and the fiber bundle containing the thermoplastic multifiltrate is twisted in one direction so that the cross-sectional shape becomes flat by heating. After processing a flat piece twisted cord having a ratio a / b of 1.1 to 3.5, a strip material covered with rubber is formed using the flat piece twisted cord as a reinforcing cord. A belt reinforcing layer is formed, and at least one carcass layer is mounted between the pair of left and right bead portions, and a reinforcing cord that is inclined with respect to the tire circumferential direction is provided on the outer peripheral side of the carcass layer in the tread portion. A pneumatic tire for a passenger car, characterized by forming a green tire having at least two belt layers and the belt reinforcing layer, and vulcanizing the green tire. Method of manufacturing a Rutaiya. The pneumatic radial tire for a passenger car according to claim 6, wherein the twist coefficient K expressed by the following formula (1) of the flat piece twisted cord constituting the belt reinforcing layer is in a range of 800 to 1200. Production method.
K = T√D (1)
T: Number of twisted cords (times / 10cm)
D: Total fineness of cord (dtex)   8. The ratio a / b between the major axis “a” and the minor axis “b” of the flat piece twisted cord constituting the belt reinforcing layer is in a range of 1.2 to 3.0. Of manufacturing pneumatic radial tires for passenger cars.   A flat piece twisted cord constituting the belt reinforcing layer is treated with an adhesive composed of a mixture of resorcin / formaldehyde initial condensate and rubber latex, and the rubber latex is made of vinylpyridine / styrene / butadiene / terpolymer latex. The weight ratio of the solid content of the rubber latex and the solid content of the resorcin / formaldehyde precondensate is in the range of 100/20 to 100/30. A method for producing a pneumatic radial tire for a passenger car according to claim 1.   The twist direction of the flat piece twisted cord constituting the belt reinforcing layer is the same direction as the inclination direction of the reinforcing cord of the belt layer adjacent to the belt reinforcing layer with respect to the tire circumferential direction. The manufacturing method of the pneumatic radial tire for passenger cars in any one.

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