JP2009166726A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having superior high-speed stability, riding comfort and steering stability, and capable of reducing rolling resistance. <P>SOLUTION: The pneumatic tire 1 has a circumferential belt layer 3b with a strip-like layer having a plurality of rubber-covered cords being spirally wound in the tire circumferential direction on the outer side in the tire radial direction of a carcass 2 extending toroidally across a pair of bead parts and on the outer side in the tire radial direction of two or more belt layers 3a arranged in an inclined manner to the equatorial plane of the tire, and a tread 4 on the outer side in the tire radial direction of the belt 3b. At least a side area of the tread 4 has layered structures 4a, 4b having at least two layers of different rubber. When the tire is assembled to an applicable rim, and the specified internal pressure is given, the inequalities 0.003≤d/TW≤0.04 are satisfied, where TW denotes the width of the tread 4, and d denotes the difference between the radius of a maximum outside diameter part of the tire and the radius of a tread end. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that is excellent in high-speed durability, ride comfort, and handling stability, and has reduced rolling resistance.

  Conventionally, various measures have been taken to improve the high-speed durability of pneumatic tires, and it is known that improvement of the belt structure of the tire is particularly advantageous. In other words, the direction in which the cords cross each other between two or more rubberized layers of rubber coated with a plurality of cords inclined at a relatively small angle with respect to the equator plane of the tire, for example, 15 to 35 ° And a rubberized layer coated with rubber on an organic fiber cord inclined at a very small angle with respect to the equator plane of the tire on the outer side in the tire radial direction of the belt layer. A pneumatic tire having a belt structure provided with a belt reinforcing layer is generally used.

  Since the inclined belt layer and the belt reinforcing layer are provided in this manner, the tire is prevented from being stretched or compressed in the circumferential direction, so that the tire diameter growth due to the centrifugal force during high-speed running can be suppressed. As a result, since heat generation and distortion at the belt end can be reduced, high-speed durability of the tire is improved.

  However, in such a pneumatic tire, the out-of-plane bending rigidity in the circumferential direction of the tread is increased, and the longitudinal spring constant of the pneumatic tire is a large value, so that riding comfort is reduced. Furthermore, since the contact length is shortened and the contact area is reduced, there is a problem that the steering stability is lowered.

As a measure for solving such problems, Patent Document 1 proposes improving the belt inclination angle and the belt reinforcing layer.
JP 2006-193032 A

  That is, the inclination angle of the cord used for belt reinforcement is increased in the inner belt layer than the outer side in the tire radial direction, and the longitudinal spring constant is reduced by reducing the out-of-plane bending rigidity of the tread, thereby improving the riding comfort. It has improved. In addition, the ground contact length is increased to increase the ground contact area, and the steering stability is improved by increasing the cornering power.

  Furthermore, the belt reinforcement layer is a belt reinforcement layer formed by spirally winding a belt-like rubberized layer coated with a plurality of cords in the tire circumferential direction, thereby suppressing radial growth and improving high-speed durability. It has improved.

However, in recent years, efforts to reduce CO ₂ emissions for the prevention of global warming have been directed to reducing the fuel consumption of automobiles, and there is a demand for reducing the rolling resistance of tires that contribute to reducing fuel consumption. .

  Accordingly, an object of the present invention is to reduce rolling resistance in a pneumatic tire excellent in high speed stability, riding comfort, and steering stability.

  Now, it is known that the energy loss (strain energy loss) of rubber resulting from repeated deformation during tire rolling is 90% or more of the cause of deteriorating the rolling resistance of the tire. Therefore, reducing the strain energy loss that accompanies repeated deformation is effective in reducing the rolling resistance.

  On the other hand, when the tread rubber is bent greatly in the out-of-plane direction before and after the grounding surface during rolling of the tire, the tread rubber is greatly distorted and the strain energy loss increases, resulting in high rolling resistance. It becomes a problem.

  Thus, as a result of earnestly examining the measures for solving the above-mentioned problems, the inventors have found that by laminating tread rubber, strain energy loss is reduced and rolling resistance is reduced, thereby completing the present invention. It came to.

That is, the gist of the present invention is as follows.
(1) A carcass extending in a toroidal shape across a pair of bead portions is used as a skeleton, and a plurality of tires arranged at an inclination angle of 45 ° to 80 ° with respect to the equator plane of the tire on the outer side in the tire radial direction of the carcass. An inclined belt layer in which two or more rubberized layers coated with rubber are arranged in a direction in which the cords cross each other between the layers, and a plurality of cords are covered with rubber on the outer side in the tire radial direction of the inclined belt layer A pneumatic tire having a tread on the outer side in the tire radial direction of the belt, comprising a belt made of a circumferential belt layer formed by spirally winding the belt-shaped rubberized layer in the tire circumferential direction,
At least a side region of the tread has a laminated structure having at least two layers of different rubbers, and when the tire is incorporated in an applicable rim and a prescribed internal pressure is applied, the tread width is TW and the tire has a maximum outer radius. A pneumatic tire characterized by satisfying a relationship of 0.003 ≦ d / TW ≦ 0.04, where d is the difference between the radius of the tread end and the radius of the tread end.

(2) The pneumatic tire according to (1), wherein the tread includes two layers, a tread side rubber layer and a belt side rubber layer.

(3) The pneumatic tire according to (2), wherein the belt side rubber layer has a smaller tan δ than the tread side rubber layer.

(4) The pneumatic tire according to (3), wherein the belt-side rubber layer has a loss tangent tan δ of 0.12 or less.

(5) The pneumatic tire according to (2), wherein the belt-side rubber layer has a thickness of 0.5 to 5 mm.

(6) The pneumatic tire according to (2), wherein the rubber layer on the belt side is made of different rubber in the central region and the side region of the tread in the width direction.

(7) The pneumatic tire according to (6), wherein a side region of the belt-side rubber layer is softer than a central region of the belt-side rubber layer.

(8) The pneumatic tire according to (3), wherein the belt-side rubber layer is disposed in the side region.

(9) The pneumatic tire according to any one of (8), wherein the width of the rubber layer on the belt side in the central region is 30 to 80% of the width TW of the tread.

(10) When the inner side in the width direction is the central region and the outer side in the width direction is the side region from the position of 45% of the tread width TW from the center of the tread, the thickness t1 of the belt-side rubber layer in the central region and the belt side of the measuring region The pneumatic tire according to (3), wherein the rubber layer has a thickness t2 satisfying a relationship of t1 <t2.

(11) The _{t 2} is the pneumatic tire according to the above (10), which is a 1.2 to 10 times the _{t 1.}

(12) The pneumatic tire according to any one of (1) to (10), wherein the cord of the circumferential belt layer is made of an aromatic polyamide.

(13) The pneumatic tire according to any one of (1) to (10), wherein the cord of the circumferential belt layer is a steel cord.

(14) The pneumatic tire as described in (12) above, wherein the elongation at break of the steel cord is 4.5% or more.

  According to the present invention, in a pneumatic tire excellent in high-speed durability, ride comfort, and steering stability, distortion generated in the tread rubber is suppressed and rolling resistance is reduced by reducing strain energy loss. be able to. Therefore, the pneumatic tire has excellent high-speed durability, ride comfort, and handling stability, and low rolling resistance.

The present invention will be specifically described below.
FIG. 1 shows a cross-sectional view in the width direction of a pneumatic tire according to the present invention.
1, a tire 1 has a carcass 2 extending in a toroidal shape across a pair of bead portions (not shown) as a skeleton, and an inclined belt layer 3a and a circumferential belt layer 3b on the outer side in the tire radial direction of the carcass 2. The belt 3 has a tread 4 on the outer side in the tire radial direction of the belt 3. In FIG. 1, half of the equator plane O is omitted, but the structure is symmetrical with O sandwiched.

  The inclined belt layer 3a is composed of two or more rubberized layers in which a plurality of cords arranged at an inclination angle of 45 to 80 ° with respect to the equator plane O of the tire are covered with rubber. It is arranged in the direction where they cross each other. The circumferential belt layer 3b is formed by spirally winding a belt-like rubberized layer in which a plurality of cords are covered with rubber in the tire circumferential direction.

  Here, it is important that the cords of the inclined belt layer 3a are arranged at an inclination angle of 45 to 80 ° with respect to the equator plane O. This is because if the inclination angle is less than 45 °, the out-of-plane bending rigidity of the belt 3 increases, and the ground contact area decreases, so that the steering stability deteriorates. On the other hand, if the inclination angle exceeds 80 °, the in-plane bending rigidity of the belt 3 becomes small, and the deformation of the belt becomes large during cornering, so that the steering stability is deteriorated.

  And it is important that at least the side region of the tread 4 has a laminated structure (two layers in the illustrated example) having at least two layers of different rubbers. That is, by forming a laminated structure having at least two layers of different rubbers in at least the side region of the tread 4, even if a large strain occurs, strain energy loss can be reduced, so that rolling resistance can be reduced. it can.

  In addition, when arrange | positioning a different rubber | gum to the laminated structure of the tread 4, it can also arrange | position not only to the side area of the tread 4, but to the whole area of the tread 4, for example. Further, the laminated structure may be three or more layers as long as at least two layers are different rubbers.

  Next, in a state where the tire is incorporated into the applicable rim and the specified internal pressure is applied, when the width of the tread is TW and the difference between the radius of the maximum outer diameter portion of the tire and the radius of the tread edge is d, 0.003 ≦ It is important to satisfy the relationship of d / TW ≦ 0.04.

  Here, the application rim and the prescribed internal pressure mean the application rim and the air pressure defined in JATMA YEAR BOOK.

  In addition, the tread width TW means a linear distance in the width direction between both ends of the tread in a no-load state in the tire width direction cross section shown in FIG.

Moreover, the radius of the largest outer diameter of the tire in the width direction cross-section shown in FIG. 1, the length l ₁ of the perpendicular dropped from the maximum outer diameter of the tire in the rotational axis L of the tire, the radius of the tread edge Is the length l _{2 of the} perpendicular drawn from the tread end to the tire rotation axis L, and d is the difference between l ₁ and l ₂ .

  That is, when d / TW is less than 0.003, the contact length in the region serving as the contact end becomes too long, and the wear on the side region of the tread is promoted. On the other hand, when d / TW exceeds 0.04, the difference in diameter between the central region and the side region of the tread 4 becomes large, and when the tire comes into contact with the road surface, compression deformation of the tread central region in the tire circumferential direction and the tread side Since the tensile deformation of the region increases, the rolling resistance increases.

  Next, the tread 4 is preferably two layers of a tread side rubber layer 4a and a belt side rubber layer 4b. This is because, when a tire is manufactured, it is easier to manufacture the tread 4 by laminating rubber in two layers than to produce the tread 4 by laminating rubber in three or more layers.

  The belt-side rubber layer 4b preferably has a smaller tan δ than the ground-contact side rubber layer 4a. That is, since the strain energy loss can be reduced by making the tan δ of the rubber layer 4b smaller than the tan δ of the rubber layer 4a, the rolling resistance can be reduced. If the tan δ of the rubber layer 4a is larger than the tan δ of the rubber layer 4b, the grip of the tire can be sufficiently exerted, and the steering stability is improved.

  Here, the tan δ of the rubber layer 4b is preferably 0.12 or less. This is because the strain energy loss can be sufficiently reduced by setting the tan δ of the rubber layer 4b to 0.12 or less. In order to suppress the deterioration of the fracture characteristics of the rubber layer 4b and ensure sufficient fracture characteristics, tan δ is preferably set to 0.03 or more.

  Next, the thickness of the rubber layer 4b on the belt side is preferably 0.5 to 5 mm. That is, if the thickness is less than 0.5 mm, the rubber thickness is too thin and the effect of suppressing strain energy loss is reduced. On the other hand, if the thickness exceeds 5 mm, the volume of the entire tread becomes too large and the weight of the entire tire is reduced. Will increase.

  Now, the tread 4 has a rounded shape in the width direction for reasons such as suppressing side wear. Therefore, when the tire 1 comes into contact with the road surface, the tread 4 generates a force (wiping force) for flattening the rounded shape. Along with this, in the tread side region, a larger strain is generated than in the tread central region, and the rolling resistance is further increased. In order to further reduce the rolling resistance of the entire tire, it is effective to suppress a large distortion caused by the wiping force.

  Therefore, the belt-side rubber layer 4b is preferably made of different rubber in the central region and the side region in the tread width direction. That is, by making the rubber layer in the central region and the side region different, a structure capable of suppressing a large strain generated in the side region can be obtained, so that the rolling resistance can be further reduced. More preferably, a rubber having a small tan δ is applied to the belt-side rubber layer 4b so that the rubber in the side region is softer than the rubber in the central region in terms of reducing rolling resistance.

  Further, since distortion caused by the wiping force is generated particularly in the side region of the tread 4, it is also effective to further reduce the rolling resistance by arranging rubber having a small tan δ only in the side region.

Further, the wiping force starts to increase from the center of the tread toward the outside in the width direction from the position of 15% of the tread width TW, and becomes maximum at a position of 40% to 50% of the tread width TW. Therefore, the width TW ₁ of the belt-side rubber layer in the central region is preferably 30 to 80% of the tread width TW.

Next, as shown in FIG. 4, the thickness of the belt-side rubber layer in the central region when the inner side in the width direction from the position P of 45% of the tread width TW from the center of the tread is the central region and the outer side in the width direction is the side region it is preferable that the thickness of t ₁ and the side area of the belt side rubber layer t ₂ satisfies the relation of t _{1 <t 2.} Here, the thickness t ₁ of the rubber layer is the average thickness of the central region, while the thickness t _{2 of the} rubber layer means the average thickness of the side region.

That is, since the wiping force is particularly large in the side region, it is preferable to increase the t ₂ and absorb the deformation with a rubber having a small tan δ. Furthermore, since a large lateral force is generated during cornering in the central region, it is preferable to reduce t ₁ and increase rigidity.

The thickness _{t 2} of the rubber layer is preferably 1.2 to 10 times the _{t 1.} At below 1.2 times t ₂ is t _1, by increasing the thickness of the belt-side rubber layer 4b of the tread side region, the effect of reducing the wiping force is reduced, whereas, more than 10 times t ₁ And the thickness of the belt side rubber layer 4b in the tread side region is too thick, and the weight of the tire increases.

  Now, the cord of the circumferential belt layer is preferably made of an aromatic polyamide. That is, when the cord is made of an aromatic polyamide, the compression rigidity of the circumferential belt layer can be reduced, the out-of-plane bending rigidity can be reduced, and the steering stability and riding comfort can be improved.

  Further, the cord of the circumferential belt layer may be a steel cord. That is, by applying the steel cord to the circumferential belt layer, it is possible to ensure the tensile strength in the circumferential direction of the belt, so that the tensile strength in the circumferential direction of the belt decreases and the tire diameter grows at high speeds. Can be suppressed, and a reduction in high-speed durability can be suppressed.

  Furthermore, when a steel cord is applied to the circumferential belt layer, the cord preferably has an elongation at break of 4.5% or more. Here, the elongation at break means a value calculated based on a result obtained by performing a tensile test based on JIS Z 2241. That is, by applying a steel cord having an elongation at break of 4.5% or more to the circumferential belt layer, a pneumatic tire having high-speed durability and excellent shock absorption can be obtained.

  Under various specifications shown in Table 1 and Table 2, a polyethylene cord is applied to the carcass ply, the belt has two inclined belt layers and a circumferential belt layer, the tread width is 146 mm, the rubber layer A pneumatic radial tire having a tire size of 195 / 65R15 having a tread having two layers was manufactured. The obtained tire was incorporated into a rim of size 6.0J × 15, the internal pressure was adjusted to 210 kPa, and tests were conducted to evaluate high-speed durability, ride comfort, handling stability, rolling resistance and wear resistance. It was. The results are shown in Tables 1 and 2.

  The thickness of the belt-side rubber layer in the tread central region was measured by cutting the tire into a cross section in the width direction and measuring the thickness of the belt-side rubber layer at the center position of the tread.

  The thickness of the rubber layer on the belt side in the tread region was measured by measuring the thickness outside the position of 60 mm in the width direction from the center of the tread after cutting the tire into a cross section in the width direction.

  M100 was measured by performing a test based on JIS K 6301 (1997).

  Tan δ was measured by performing a drum test on a sample having a width of 4.7 mm, a length of 20 mm, and a thickness of 2 mm under the conditions of an amplitude of 2%, a frequency of 52 Hz, and a measurement temperature of 25 ± 3 ° C.

  High-speed durability was evaluated by running the drum at a speed of 150 km / h for 30 minutes, increasing the speed by 6 km if there was no failure, and measuring the speed when the failure occurred. The speed at which the failure occurred in the conventional example was indexed as 100.

  Steering stability is achieved by mounting the pneumatic tires described above on a 2500cc domestic FR vehicle, and a trained test driver, including 150km / h lane change, 80km / h limit driving and acceleration from 50km / h. The test was measured by performing on a test course. And the test result was evaluated with a full score of 10 points.

  Riding comfort is achieved by attaching the pneumatic tires described above to a 2500cc domestic FR vehicle and having a trained test driver run on a test course that reproduces the crossings of highway joints, cobblestone roads and railroad crossings. It was measured. And the test result was evaluated with a full score of 10 points.

  The rolling resistance was measured by applying a load of 450 kgf to the pneumatic tire described above and conducting a test based on SAE J 1269 under the condition of 80 km / h. Each index was indexed with the conventional example as 100. Note that the smaller the index value in the table, the smaller the rolling resistance and the better the tire performance.

  Uneven wear is determined by attaching a pneumatic tire to the vehicle described above and running 5000 km, and then the tire center part (the center position in the width direction of the tire) and shoulder part (the ground contact width at a point 40 mm from the center). As a result, the wear amount ratio from the boundary to the outer side in the width direction was measured and evaluated. And it is preferable that the measured value is closer to 1 because uniform wear is obtained. On the other hand, the larger the numerical value, the greater the wear of the shoulder portion.

  As shown in Invention Examples 1 to 8, it can be seen that the rolling resistance is smaller than that of the conventional example by using a tread having a two-layer structure. Further, as shown in Invention Example 2 and Invention Example 3, an example in which a belt-side rubber layer is disposed only in the tread side region, and the thickness of the belt-side rubber layer in the tread side region is set to the belt side rubber in the tread central region. By making it thicker than the thickness of the layer, steering stability and rolling resistance are superior to the conventional example.

  Invention Example 4 and Invention Example 5 are examples in which the rubber of the rubber layer on the belt side in the central region of the tread is hardened and the rubber layer of the side region is softened, and the rolling resistance is superior to the conventional example. Invention Examples 6 and 7 are an example in which a steel cord having a breaking elongation of 3.5% or more is applied to the cord of the circumferential belt layer and an example in which the d / TW value is reduced, and the steering stability and rolling are lower than in the conventional example. The resistance is excellent.

  Here, under the specifications of Invention Examples 1 to 7 described in Table 1, d / TW was changed as shown in Table 3, and the relationship between rolling resistance (RR) and uneven wear was arranged. The results are shown in FIGS. 6 (a) and (b). 6 (a) and 6 (b), it can be seen that rolling resistance and uneven wear are significantly improved by setting 0.003 ≦ d / TW ≦ 0.04. That is, it can be seen that d / TW is very important in reducing the rolling resistance.

It is a figure which shows the cross section of the width direction of the pneumatic tire according to this invention. It is a figure which shows the cross section of the width direction of the pneumatic tire according to this invention. It is a figure which shows the cross section of the width direction of the pneumatic tire according to this invention. It is a figure which shows the cross section of the width direction of the pneumatic tire according to this invention. It is a figure which shows the cross section of the width direction of the conventional pneumatic tire. It is the figure shown about the relationship of rolling resistance, partial wear, and ratio d / TW.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Carcass 3a Inclined belt layer 3b Circumferential belt layer 3 Belt 4a Grounding surface side rubber layer 4b Belt side rubber layer 4 Tread

Claims (14)

A carcass extending in a toroidal shape across a pair of bead portions is used as a skeleton, and a plurality of cords arranged on the outer side in the tire radial direction of the carcass with an inclination angle of 45 to 80 ° with respect to the equator plane of the tire is made of rubber. An inclined belt layer formed by arranging two or more coated rubberized layers in a direction in which the cords cross each other between the layers, and a belt-like rubber in which a plurality of cords are rubber-coated on the outer side in the tire radial direction of the inclined belt layer A pneumatic tire having a belt comprising a circumferential belt layer formed by spirally winding a pulling layer in the tire circumferential direction and having a tread on the outer side in the tire radial direction of the belt,
At least a side region of the tread has a laminated structure having at least two layers of different rubbers, and in a state where the tire is incorporated in an applicable rim and a specified internal pressure is applied, the tread width is TW and the maximum outer diameter portion of the tire is A pneumatic tire characterized by satisfying a relationship of 0.003 ≦ d / TW ≦ 0.04, where d is a difference between the radius and the radius of the tread edge.   2. The pneumatic tire according to claim 1, wherein the tread includes two layers of a tread side rubber layer and a belt side rubber layer.   The pneumatic tire according to claim 2, wherein the belt side rubber layer has a tan δ smaller than that of the tread side rubber layer.   The pneumatic tire according to claim 3, wherein the belt-side rubber layer has a tan δ of 0.12 or less.   The pneumatic tire according to claim 2, wherein the belt-side rubber layer has a thickness of 0.5 to 5 mm.   The pneumatic tire according to claim 2, wherein the rubber layer on the belt side is made of different rubber in a central region and a side region in the tread width direction.   The pneumatic tire according to claim 6, wherein a side region of the belt-side rubber layer is softer than a central region of the belt-side rubber layer.   The pneumatic tire according to claim 3, wherein the rubber layer on the belt side is disposed in the side region.   The pneumatic tire according to claim 8, wherein the width of the rubber layer on the belt side in the central region is 30 to 80% of the width TW of the tread. When the inner side in the width direction is a central region and the outer side in the width direction is a side region from the position of 45% of the tread width TW from the center of the tread, the thickness t ₁ of the belt side rubber layer in the central region and the belt side rubber in the side region The pneumatic tire according to claim 3, wherein the layer thickness t ₂ satisfies a relationship of t ₁ <t ₂ . The pneumatic tire according to claim 10, wherein t ₂ is 1.2 to 10 times t ₁ .   The pneumatic tire according to any one of claims 1 to 11, wherein the cord of the circumferential belt layer is made of an aromatic polyamide.   The pneumatic tire according to any one of claims 1 to 11, wherein the cord of the circumferential belt layer is a steel cord.   The pneumatic tire according to claim 13, wherein the breaking elongation of the steel cord is 4.5% or more.

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