JP2005075289A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of obtaining high-speed durability and load noise reduction while suppressing an increase of a rolling resistance. <P>SOLUTION: In the pneumatic radial tire, a belt layer 3 is disposed on an outer circumference of a carcass layer 2, and a belt reinforcement layer 4 having a reinforcement cord of the intermediate elongation of ≤ 5.5% under the load of 67N wound substantially in the circumferential direction of the tire is disposed around the belt layer 3. The cord density in an end area of the belt reinforcement layer 4 is set to be lower than that in a tread center area, or the initial tension of the reinforcement cord in the end area is set to be lower than that of the reinforcement cord in the tread center area. Alternatively, the cord angle in relation to the tire circumferential direction of the belt layer 3 is set to be 25-31°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire that achieves high speed durability and road noise reduction based on a belt reinforcement layer using a low intermediate elongation cord while suppressing rolling resistance.

  Generally, pneumatic radial tires designed for high-speed running have a belt reinforcement layer in which a heat-shrinkable nylon cord is spirally wound in the tire circumferential direction on the outer periphery of the belt layer disposed inside the tread. ing. This belt reinforcement layer prevents the both end portions of the belt layer from being lifted by a centrifugal force during high-speed running, and ensures high-speed durability by preventing peeling from the rubber layer.

  In Patent Document 1, in the empty radial tire provided with the belt reinforcing layer as described above, road noise is reduced by using an organic fiber cord having a small intermediate elongation as a reinforcing cord constituting the belt reinforcing layer. I have proposed that. However, according to the results of further studies by the present inventors, the use of a reinforcing cord having a low intermediate elongation for the belt reinforcing layer can provide high-speed durability and road noise reduction effects, but on the other hand, it is low. It has been found that the reinforcing cord of intermediate elongation has a problem that the rolling resistance of the tire increases because tan δ is large.

That is, by using a reinforcement cord with a low intermediate elongation for the belt reinforcement layer, the belt reinforcement layer has a stronger tagging effect on the belt layer than the center of the tread, resulting in a rounded tread radius and ground deformation. The energy loss at the time was increasing.
JP 2001-180220 A

  An object of the present invention is to provide a pneumatic radial tire in which, when a reinforcing cord having a low intermediate elongation is used for the belt reinforcing layer, the effect of reducing high-speed durability and reducing road noise can be obtained while suppressing rolling resistance. There is to do.

  In order to achieve the above object, the present invention provides a pneumatic radial tire comprising the following three inventions.

  A first aspect of the present invention is a pneumatic radial tire in which a belt layer is disposed on the outer periphery of the carcass layer, and a belt reinforcing layer in which a reinforcing cord circulates substantially in the tire circumferential direction is disposed around the belt layer. The belt reinforcing layer has a reinforcing cord having an intermediate elongation at 67N load of 5.5% or less, and a cord density in an end region of the belt reinforcing layer is made sparser than a tread central region. Is.

  According to a second aspect of the present invention, there is provided the pneumatic radial tire in which the belt layer is disposed on the outer periphery of the carcass layer, and the belt reinforcing layer in which the reinforcing cord circulates substantially in the tire circumferential direction is disposed around the belt layer. The intermediate elongation at 67N load of the reinforcing cord of the reinforcing layer is 5.5% or less, and the initial tension of the reinforcing cord in the end region of the belt reinforcing layer is made smaller than the reinforcing cord in the central region of the tread. To do.

  The third aspect of the invention is a pneumatic radial tire in which a belt layer is disposed on the outer periphery of the carcass layer, and a belt reinforcement layer in which a reinforcement cord circulates substantially in the tire circumferential direction is disposed around the belt layer. The intermediate elongation at 67N load of the reinforcing cord of the belt reinforcing layer is set to 5.5% or less, and the cord angle of the belt layer with respect to the tire circumferential direction is set to 25 to 31 degrees.

  In the first invention, since the belt reinforcement layer is composed of a reinforcing cord having an intermediate elongation at 67N load (hereinafter simply referred to as intermediate elongation) of 5.5% or less, high speed durability and road noise are achieved. A reduction effect can be obtained. In addition, since the cord density of the belt reinforcing layer is made sparser in the end region of the belt reinforcing layer than the central region of the tread, the tagging action of the belt reinforcing layer becomes weaker in the shoulder portion than in the central portion of the tread, and as a result, the tread radius The rolling resistance can be reduced by approaching a flat shape and reducing the energy loss during ground deformation.

  In the second aspect of the invention, the belt reinforcing layer is similarly formed of a reinforcing cord having an intermediate elongation of 5.5% or less, so that high speed durability and road noise reduction effects can be obtained. In addition, since the initial tension of the reinforcing cords in the end region of the belt reinforcing layer is made smaller than that in the central region of the tread, the belt reinforcing layer's tagging action is weaker in the shoulder than in the central portion of the tread, and the tread radius is flattened. Since it is close to the shape, rolling resistance can be reduced.

  In the third aspect of the invention, the belt reinforcing layer is similarly formed of a reinforcing cord having an intermediate elongation of 5.5% or less, so that high speed durability and road noise reduction effects can be obtained. In addition, by making the cord angle of the belt layer with respect to the tire circumferential direction more than 25 degrees, which is larger than that of a normal radial tire, the tread radius is made closer to a flat shape and the rolling resistance is reduced because the action of the belt layer is relaxed. Can be reduced.

  The tire applied to the present invention is a pneumatic radial tire in which a belt layer is arranged on the inner side of the tread, and the tire is substantially provided with a reinforcing cord around the belt layer in order to enhance high-speed durability. It is intended for the one in which a belt reinforcing layer that is circulated in the circumferential direction is arranged, and particularly for a pneumatic radial tire for a passenger car. In the belt layer, the belt cord is a steel cord, but a high elastic modulus organic fiber cord such as an aramid cord may be used for part or all of the belt layer.

  FIG. 1 is a half sectional view showing an essential part of an example of a pneumatic radial tire of the present invention.

  Reference numeral 1 denotes a tread portion, and reference numeral 2 denotes a carcass layer disposed inside the tire. Two upper and lower belt layers 3 are disposed on the outer circumferential side of the carcass layer 2, and a belt reinforcing layer 4 is disposed on the outer circumferential side of the belt layer 3. The reinforcing cord of the belt reinforcing layer 4 is configured to circulate substantially in the tire circumferential direction. Further, the belt reinforcing layer 4 extends over the entire width of the belt layer 3 in the tire width direction, and a part of each end portion protrudes to the outside of the belt layer 3.

  As the reinforcing cord constituting the belt reinforcing layer 4, an organic fiber cord having a low intermediate elongation of 5.5% or less, preferably in a range of 1.5 to 5.5% is used. Since the belt reinforcing layer 4 is composed of a cord having a low intermediate elongation in this way, the belt reinforcing layer 4 exerts a high tagging action on the end of the belt layer 3 and only improves high-speed durability. In addition, a high road noise reduction effect is generated.

  In the present invention, the belt reinforcing layer is arranged on the outer peripheral side of a plurality of belt layers as in the illustrated example, or may be arranged between the layers, or arranged between the belt layer and the carcass layer. May be. Therefore, in the present invention, the belt reinforcing layer is arranged around the belt layer in addition to the case where the belt reinforcing layer is arranged on the outer peripheral side of the plurality of belt layers. The case where it arrange | positions between the inner peripheral side of this and a carcass layer is included. A plurality of belt reinforcing layers may be arranged by combining a plurality of the above arrangements.

  The belt reinforcing layer is formed by winding reinforcing cords so as to be arranged substantially in the tire circumferential direction. The tire circumferential direction substantially means that the reinforcing cord has a relationship of 0 ° with respect to the tire circumferential direction, but if it is within 15 °, it is regarded as equivalent to the tire circumferential direction. used.

  Any conventionally known method can be used as a method for forming the belt reinforcing layer. Preferably, a method of forming a strip material in which a plurality of reinforcing cords (about 2 to 30) of reinforcement cords are gathered and rubberized is substantially spirally wound in the tire circumferential direction is preferable from the viewpoint of productivity. It is. The width of the strip material is not particularly limited, but is preferably about 3 to 20 mm.

  As a method for forming the belt reinforcing layer used in the present invention, although the productivity is slightly low, a sheet material that is rubberized by aligning a large number of reinforcing cords in the extending direction of the reinforcing cords for one round of the tire is used. It is also possible to cut the bias only and wrap this in the tire circumferential direction to splice both ends.

  An organic fiber cord is preferably used for the reinforcing cord of the belt reinforcing layer. The type of the organic fiber cord is not particularly limited as long as the intermediate elongation is 1.5 to 5.5% in the tire after vulcanization. For example, polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), aromatic polyamide, poly-p-phenylenebenzobisoxazole, polyvinyl alcohol, nylon and the like can be exemplified. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferable.

  This organic fiber cord may be composed of only a single polymer, or may be composed of two or more types of polymers. The fiber cord in the case of being composed of two or more types of polymers is preferably one in which two or more types of fiber cords made of each polymer are aligned or twisted together. Further, it may be a fiber cord using a composite yarn obtained by spinning two or more kinds of liquid polymers from the same spinning hole into a core-sheath shape or a bimetallic shape. Examples of the composite yarn include a core-sheath type composite yarn in which a polyester such as polyethylene terephthalate or polyethylene-2,6-naphthalate is used as a core and nylon is used as a sheath.

  In the present invention, rolling resistance generated when the above-described reinforcing cord having a low intermediate elongation is used for the belt reinforcing layer is suppressed as follows.

  As a configuration according to the first invention, the cord density in the end region of the belt reinforcing layer is made sparser than the tread central region. With this configuration, the hoop effect of the belt reinforcing layer is weaker at the shoulder than at the center of the tread, so that the tread radius approaches a flat shape and energy loss during ground deformation is reduced. Therefore, rolling resistance is reduced and the fuel consumption rate of the vehicle is reduced.

  Here, the cord density in the end region of the belt reinforcing layer means the average cord density (number of cords driven per 10 mm width) in the end region having a width corresponding to 20% of the maximum width belt layer. The cord density in the central region of the tread of the reinforcing layer refers to an average cord density (number of cords driven per 10 mm width) in a region centered on the center of the tread having a width corresponding to 20% of the belt layer having the maximum width. The cord density in the end region of the belt reinforcing layer is preferably in the range of 5 to 10 cords / 10 mm, and the cord density in the central region of the tread is preferably in the range of 7 to 14 cords / 10 mm. The difference in cord density between the end region of the belt reinforcing layer and the central region of the tread is preferably in the range of 2 to 5 pieces / 10 mm.

  As a configuration according to the second aspect of the invention, the initial tension of the reinforcing cord in the end region of the belt reinforcing layer is made smaller than that in the tread central region. With this configuration, the tagging effect of the belt reinforcement layer is weaker at the shoulder portion than at the tread central portion, as in the second aspect of the invention, so that the tread radius increases as the tread radius approaches a flat shape. . Therefore, the power loss of the vehicle is reduced and the rolling resistance is reduced.

  As described above, as a method of changing the initial tension of the reinforcing cord, when vulcanizing an unvulcanized tire, the lift rate when pushing up to the inner surface of the mold with a bladder is lower at the end than at the center of the belt reinforcing layer. The green tire shape and / or the mold shape may be used. As another method, when forming the belt reinforcing layer by spirally winding the reinforcing cord, the pretension in the end region is made lower than the pretension when the tread central region of the belt reinforcing layer is formed. It may be. Alternatively, the diameter of the forming drum for forming the belt layer and the belt reinforcing layer is made larger than the central area in the axial end areas, or the reinforcing cords are wound around both ends to reinforced the belt. You may make it the diameter when forming a layer become large in an edge part area | region rather than a center part.

  When an unvulcanized tire having a belt reinforcing layer formed in this manner is placed in a mold and vulcanized, the initial tension of the reinforcing cord in the end region of the belt reinforcing layer is made smaller than that in the central region of the tread. Can do.

  Moreover, as a structure which concerns on 3rd invention, it is making the cord angle with respect to the tire circumferential direction of a belt layer into 25-31 degree | times. Thus, if the cord angle of the belt layer with respect to the tire circumferential direction is set to 25 degrees or more, which is larger than that of a normal radial tire, the tag layer effect of the belt layer is relaxed, and the degree of relaxation becomes greater at the end of the belt layer The tread radius approaches a flat shape and the rolling resistance can be reduced. A cord angle of 31 degrees or more is not preferable because cornering characteristics are deteriorated and steering stability is deteriorated.

  Each of the first to third configurations described above may be used as a single configuration, or two or more configurations may be used in combination. These combinations can further improve the rolling resistance reduction effect.

Examples 1 and 2
The tire size is 225 / 50R17, the tire structure of FIG. 1, the belt layer is made of steel cord (cord angle 21 ° with respect to the tire circumferential direction), and the polyethylene tererate fiber cord is used as the reinforcement cord of the belt reinforcement layer. Under common conditions of use, the median elongation E (%) at 67N load of the reinforcement cord of the belt reinforcement layer and the cord density (core / 10mm) between the center area and the end area of the belt reinforcement layer As shown in Table 1, five types of pneumatic radial tires were produced.

  For these five types of pneumatic radial tires, road noise, high-speed durability, and rolling resistance were measured by the following measurement methods, and the evaluation results are shown in Table 1 as indices. From the results in Table 1, it can be seen that the tires of Examples 1 and 2 are both excellent in reducing rolling resistance while maintaining road noise reducing effect and high-speed durability.

[Road noise]
The test tire is mounted on a standard rim stipulated by JATMA, the air pressure is 200 kPa, it is mounted on a passenger car with a displacement of 3000 cc, a microphone is installed at the position corresponding to the driver's ear on the driver's seat window side in the passenger compartment, and the rough road surface The sound pressure level [dB (A)] of road noise in the 250 to 400 Hz band when traveling at a speed of 50 km / h was measured.

  The evaluation was performed by the reciprocal of the measured value, and the index was shown with the tire of Conventional Example 1 as 100. The larger the index, the better.

[High-speed durability]
Using a rotating drum with a drum diameter of 1707 mm, after finishing the high-speed endurance test method specified in JIS D4230, the test tire was continuously increased by 10 km / h every 10 minutes until the tire broke down. Evaluation was made based on the magnitude of the speed at the time.

  Evaluation was shown by the index | index which makes the measured value of the tire of the prior art example 1 100. FIG. The larger the index, the better.

(Rolling resistance)
Using a drum-type tire rolling resistance tester equipped with a rotating drum having a drum diameter of 1707 mm, rolling resistance was measured when the test tire was run at a load of 4.5 kN, an internal pressure of 200 kPa, and a speed of 80 km / h.

  The evaluation was performed by the reciprocal of the measured value, and the index was shown with the tire of Conventional Example 1 as 100. The larger the index, the better.

Examples 3 and 4
The tire size is 225 / 50R17, the tire structure shown in Fig. 1, the belt layer is made of steel cord (cord angle 21 ° with respect to the tire circumferential direction), and polyethylene tererate fiber cord is used as the reinforcement cord of the belt reinforcement layer. In addition, with the common condition that the cord density of the belt reinforcing layer is 10 (10/10 mm), the intermediate elongation E (%) at 67 N load of the reinforcing cord of the belt reinforcing layer, respectively, during vulcanization operation Five types of pneumatic radial tires with different differences between the lift rate of the tread center and the lift rate of the shoulder [= (lift rate of the tread center) − (lift rate of the shoulder)] as shown in Table 2 Produced.

  For these five types of pneumatic radial tires, road noise, high-speed durability, and rolling resistance were measured by the same measurement method as described above, and the evaluation results are shown as indexes in Table 2 (however, the indexes are those of Conventional Example 2). Tires are shown as 100). From the results of Table 2, it can be seen that the tires of Examples 3 and 4 are all excellent in the rolling resistance reduction effect while maintaining the road noise reduction effect and the high speed durability.

Examples 5 and 6
The tire size is 225 / 50R17, the tire structure of FIG. 1 is used, the belt layer is made of steel cord, polyethylene terephthalate fiber cord is used as the reinforcement cord of the belt reinforcement layer, and the cord density of the belt reinforcement layer is 10 (3 / 10mm) under the common conditions, the intermediate elongation E (%) of the reinforcing cord of the belt reinforcing layer at 67N load and the cord angle of the belt layer with respect to the tire circumferential direction are varied as shown in Table 3. Four types of pneumatic radial tires were produced.

  For these four types of pneumatic radial tires, road noise, high-speed durability, and rolling resistance were measured by the same measurement method as described above, and the evaluation results are shown as indexes in Table 3 (however, the indexes are those of Conventional Example 2). Tires are shown as 100). From the results of Table 3, it can be seen that the tires of Examples 5 and 6 are all excellent in the rolling resistance reduction effect while maintaining the road noise reduction effect and the high speed durability.

1 is a half cross-sectional view showing a main part of a tread region of a pneumatic radial tire according to an embodiment of the present invention.

Explanation of symbols

1 Tread part 2 Carcass layer 3 Belt layer 4 Belt reinforcement layer

Claims (6)

  In a pneumatic radial tire in which a belt layer is disposed on the outer periphery of the carcass layer, and a belt reinforcement layer in which the reinforcement cord circulates substantially in the tire circumferential direction is disposed around the belt layer, 67N of the reinforcement cord of the belt reinforcement layer A pneumatic radial tire in which the intermediate elongation under load is 5.5% or less and the cord density in the end region of the belt reinforcing layer is sparser than in the tread central region.   The pneumatic radial tire according to claim 1, wherein a cord density in an end region of the belt reinforcing layer is 10 to 50% lower than a cord density in the tread central region.   In a pneumatic radial tire in which a belt layer is disposed on the outer periphery of the carcass layer, and a belt reinforcement layer in which the reinforcement cord circulates substantially in the tire circumferential direction is disposed around the belt layer, 67N of the reinforcement cord of the belt reinforcement layer A pneumatic radial tire in which the intermediate elongation under load is 5.5% or less and the initial tension of the reinforcing cord in the end region of the belt reinforcing layer is smaller than that in the central region of the tread.   In a pneumatic radial tire in which a belt layer is disposed on the outer periphery of the carcass layer, and a belt reinforcement layer in which the reinforcement cord circulates substantially in the tire circumferential direction is disposed around the belt layer, 67N of the reinforcement cord of the belt reinforcement layer A pneumatic radial tire having an intermediate elongation under load of 5.5% or less and a cord angle of the belt layer with respect to a tire circumferential direction of 25 to 31 degrees.   The pneumatic radial tire according to claim 1, 2, or 4, wherein an initial tension of a reinforcing cord in an end region of the belt reinforcing layer is made smaller than that of a reinforcing cord in a tread central region. The pneumatic radial tire according to claim 1 or 2, wherein a cord angle of the belt layer with respect to a tire circumferential direction is set to 25 to 31 degrees.

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