JP2014226945A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve rolling resistance performance and noise suppression performance in good balance.SOLUTION: There is provided a pneumatic tire which includes a tread reinforcement layer 7 arranged in the tire radial direction outside of a carcass 6 and inside of a tread part 2. The tread reinforcement layer 7 is constituted of a reinforcement ply 9 in which an arrangement body of reinforcement cords 11 is covered with topping rubber. The reinforcement ply 9 includes: a first ply 9A which exists in the most inside in the tire radial direction and has an angle θ1 of the reinforcement cords 11A of 50 to 60°; a second ply 9B which exists outside of the first ply 9A and has an angle θ2 of the reinforcement cords 11B of 20 to 30°; and a third ply 9C which exists in the tire radial direction outside of the second ply 9B and has an angle θ3 of the reinforcement cords 11C of 20 to 30°. The reinforcement cords 11A and the reinforcement cords 11B have a same direction, and the reinforcement cords 11B and the reinforcement cords 11C have opposite directions to each other.

Description

  The present invention relates to a pneumatic tire in which rolling resistance performance and noise performance are improved in a well-balanced manner.

  In recent years, in order to improve the fuel consumption of vehicles, it has been desired to improve the rolling resistance performance of pneumatic tires. In order to reduce the rolling resistance of the tire, it is known to reduce the loss tangent (tan δ) of the tread rubber forming the contact surface of the tread portion.

  However, a tread rubber having a small loss tangent (tan δ) tends to reduce the frictional resistance with the road surface. For this reason, during cornering, the tire generates a sliding sound (sound heard by a shear) due to sliding with the road surface, resulting in a problem that the noise performance deteriorates. As a related technique, there is Patent Document 1 below.

JP 2007-253848 A

  The present invention has been devised in view of the above circumstances, and provides a pneumatic tire in which rolling resistance performance and noise performance are improved in a well-balanced manner based on improving the tread reinforcement layer. The main purpose.

  Of the present invention, the invention described in claim 1 includes a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a tread reinforcing layer disposed on the outer side in the tire radial direction of the carcass and inside the tread portion. The tread reinforcing layer is composed of three reinforcing plies in which an array of a plurality of reinforcing cords made of steel is covered with a topping rubber and overlapped inside and outside in the tire radial direction, The reinforcing ply is disposed on the innermost side in the tire radial direction and the reinforcing cord is disposed on the outer side in the tire radial direction of the first ply, the first ply having an angle θ1 of 50 to 60 ° with respect to the tire equator, The reinforcement cord has an angle θ2 of 20 to 30 ° with respect to the tire equator, and the reinforcement cord of the first ply is in the same direction with respect to the tire equator 2 plies and an outer side of the second ply in the tire radial direction, the reinforcing cord is at an angle θ3 of 20 to 30 ° with respect to the tire equator, and the reinforcing cord of the second ply is on the tire equator And a third ply that is opposite to the third ply.

  According to a second aspect of the present invention, the tread portion includes a tread rubber forming a contact surface, and the loss tangent (tan δ) of the tread rubber is 0.10 to 0.18. This is a tire.

According to a third aspect of the present invention, the reinforcing cord has a cross-sectional area of 0.060 to 0.17 mm ² and a cord diameter of 30 to 60% of the arrangement pitch of the reinforcing cord. This is a tire.

  The pneumatic tire according to the present invention includes a tread reinforcing layer composed of three reinforcing plies that overlap each other in the tire radial direction. Since the reinforcement cord of each reinforcement ply is inclined at a predetermined angle and direction in the tread reinforcement layer, the bending rigidity inside the tread portion can be increased. For this reason, rolling resistance performance improves. Moreover, since such a tread reinforcement layer has high rigidity, its in-plane bending deformation is suppressed, and slip during turning is reduced. For this reason, slip performance is reduced and noise performance is improved. Therefore, the pneumatic tire of the present invention improves rolling resistance performance and noise performance with a good balance.

It is a meridian cross-sectional view of the right half of the pneumatic tire showing an embodiment of the present invention. FIG. 2 is a development view of a reinforcing ply and a carcass ply of FIG. 1. (A) is a figure which shows the orientation of the reinforcement cord of a 2nd ply and a 3rd ply, (b) is a figure which shows the state which the load of the tire axial direction acted on each ply of (a). It is a fragmentary sectional view of a reinforcement cord. It is an expanded view of the reinforcement ply which shows embodiment of a comparative example, and a carcass ply. It is an expanded view of the reinforcement ply and carcass ply which show embodiment of another comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view of a right half including a tire rotation axis (not shown) in a normal state of a pneumatic tire (hereinafter, simply referred to as “tire”) of the present embodiment. In the present specification, the “normal state” is a no-load state in which the tire is assembled on the normal rim and filled with the normal internal pressure. When there is no notice in particular, the dimension of each part of a tire, etc. are values measured in this normal state.

  “Regular rim” is a rim that is defined for each tire in the standard system including the standard on which the tire is based. “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, it is “Measuring Rim”. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA, table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  The tire according to the present embodiment includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends in the tire axial direction, and bead portions 4 provided inward in the tire radial direction of the respective sidewall portions 3. With. The tread portion 2 is appropriately provided with a draining groove G.

  The tire includes a tread rubber 2G that forms a contact surface, a carcass 6 that extends from the tread portion 2 through the side wall portions 3 on both sides to the bead core 5 of the bead portion 4, and the outer side in the tire radial direction of the carcass 6 and the tread portion 2 And a tread reinforcing layer 7 disposed inwardly.

  In the present embodiment, the tread rubber 2G is formed of a single rubber layer disposed on the outer sides of the grounding ends Te on both sides and between the grounding surface and the tread reinforcing layer 7. The tread rubber 2G may be composed of a plurality of rubber layers (not shown) such as cap rubber and base rubber having different rubber hardness.

  The loss tangent (tan δ) of the tread rubber 2G is preferably 0.10 to 0.18 in order to improve the rolling resistance performance. “Loss tangent (tan δ)” is a value measured using a viscoelastic spectrometer at a temperature of 30 ° C. under conditions of an initial strain of 10%, a dynamic strain of ± 2%, and a frequency of 10 Hz.

  The carcass 6 is formed by one or more carcass plies 6A in the present embodiment in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire equator C. The carcass cord 6c (shown in FIG. 2) of the present embodiment is arranged at an angle α1 of 90 ° with respect to the tire equator C. As the carcass cord, for example, an organic fiber cord or a steel cord is adopted.

  The carcass ply 6A includes a main body portion 6a and a folded portion 6b. The main body portion 6 a reaches, for example, the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3. The folded portion 6b is, for example, connected to the main body portion 6a and folded around the bead core 5 from the inner side to the outer side in the tire axial direction. A bead apex rubber 8 extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A.

  The tread reinforcement layer 7 is formed of a sheet-like reinforcement ply 9 in which an array of a plurality of reinforcement cords 11 made of steel is covered with a topping rubber. The reinforcing ply 9 is formed in an annular shape by overlapping and joining both ends in the tire circumferential direction.

  The reinforcing ply 9 of the present embodiment includes a first ply 9A disposed on the innermost side in the tire radial direction, a second ply 9B disposed on the outer side in the tire radial direction of the first ply 9A, and the second ply. 9B is composed of three pieces of third plies 9C arranged on the outer side in the tire radial direction.

  FIG. 2 shows a developed view of the carcass ply 6A and the reinforcing ply 9. As shown in FIG. 2, the reinforcing cords 11A of the first ply 9A are arranged at an angle θ1 with respect to the tire equator C of 50 to 60 °. The reinforcement cord 11B of the second ply 9B is arranged at an angle θ2 with respect to the tire equator C of 20 to 30 °, and the reinforcement cord 11A of the first ply 9A is inclined in the same direction with respect to the tire equator C. The reinforcement cord 11C of the third ply 9C is arranged at an angle θ3 with respect to the tire equator C of 20 to 30 °, and is inclined in the opposite direction to the reinforcement cord 11B of the second ply 9B.

  Since the reinforcement cord 11B of the second ply 9B and the reinforcement cord 11C of the third ply 9C intersect with the tire equator C in the opposite direction and at 20 to 30 °, a large tagging effect is exerted in a well-balanced manner, and rolling resistance performance is achieved. improves. When the angle θ2 of the reinforcing cord 11B of the second ply 9B and the angle θ3 of the reinforcing cord 11C of the third ply 9C are less than 20 °, the lateral rigidity cannot be sufficiently exhibited. When the angle θ2 of the reinforcing cord 11B of the second ply 9B and the angle θ3 of the reinforcing cord 11C of the third ply 9C exceed 30 °, the circumferential rigidity is lowered and the hoop effect on the carcass 6 cannot be sufficiently exhibited. For this reason, rolling resistance performance deteriorates.

  FIG. 3A is a diagram in which the orientations of the reinforcement cord 11B of the second ply 9B and the reinforcement cord 11C of the third ply 9C are superimposed, and FIG. 3B is a diagram illustrating each ply of FIG. The figure of the state which the load of the tire axial direction acted is shown. As shown in FIG. 3A, by defining the angles θ2 and θ3 of the reinforcement cords 11B and 11C of the second ply 9B and the third ply 9C to 20 to 30 ° and opposite to the tire equator C, A rhombus whose length in the tire circumferential direction is larger than the length in the tire axial direction is formed by the reinforcing cord 11B of the second ply 9B and the reinforcing cord 11C of the third ply 9C. For this reason, as shown in FIG. 3 (b), when the load R in the tire axial direction is applied, the tread reinforcement layer 7 in which only the second ply 9B and the third ply 9C are disposed has both reinforcement cords 11B, A so-called pantograph effect occurs in which both 11C are greatly deformed in the tire axial direction. Thereby, in the two reinforcing plies of the second ply 9B and the third ply 9C, in-plane bending deformation in the tire axial direction by the tread reinforcing layer 7 occurs due to the lateral force at the time of turning, so the tread rubber 2G and A slip with the road surface occurs and a slip noise is generated.

  As shown in FIG. 2, the tread reinforcement layer 7 includes the reinforcement cord 11A of the first ply 9A, whereby the rigidity of the tread reinforcement layer 7 in the tire axial direction is increased. For this reason, the pantograph effect is suppressed and in-plane bending deformation of the tread reinforcing layer 7 during turning is reduced. Therefore, the above-mentioned sliding noise is suppressed. When the angle θ1 of the reinforcing cord 11A of the first ply 9A is less than 50 °, the angle θ1 of the reinforcing cord 11A and the angle θ2 of the reinforcing cord 11B of the second ply 9B are close to each other, and the rigidity of the tread reinforcing layer 7 is different. The directionality increases and the rolling resistance performance decreases. When the angle θ1 of the reinforcing cord 11A of the first ply 9A exceeds 60 °, the circumferential rigidity of the tread reinforcing layer 7 cannot be increased, and the in-plane bending deformation of the tread reinforcing layer 7 cannot be suppressed. For this reason, the angle θ1 of the reinforcing cord 11A is preferably 52 to 58 °.

  Such first ply 9A is provided on the innermost side in the tire radial direction. That is, the third ply 9C having a small angle θ3 of the reinforcing cord 11C is provided on the outermost side in the tire radial direction on the road surface side. As a result, the relatively small rigidity anisotropy of the reinforcing cord 11C of the third ply 9C acts on the road surface rather than the relatively large rigidity anisotropy of the reinforcing cord 11A of the first ply 9A. The tear gets smaller. Accordingly, the rolling resistance performance is improved.

  The reinforcement cord 11A of the first ply 9A and the reinforcement cord 11B of the second ply 9B are inclined with respect to the tire equator C in the same direction. That is, the reinforcing cord 11A of the first ply 9A and the reinforcing cord 11C of the third ply 9C are arranged in the opposite directions with respect to the tire equator C. Thereby, a relatively large rigidity anisotropy due to the reinforcing cord 11A of the first ply 9A far from the road surface and a relatively small rigidity anisotropy due to the reinforcing cord 11C of the third ply 9C close to the road surface It is offset in a balanced manner. Accordingly, the price tear is reduced and the rolling resistance performance is further improved.

  As shown in FIG. 1, the reinforcing plies 9 of the present embodiment have the width centers aligned with the tire equator C. The reinforcing ply 9 extends substantially continuously from the ground contact Te on one side in the tire axial direction to the ground contact end (not shown) on the other side. Thereby, the in-plane bending deformation of the tread reinforcing layer 7 is greatly suppressed, and the slip between the tread rubber 2G and the road surface is effectively reduced. From such a viewpoint, it is desirable that the width Wa of the reinforcing ply 9 in the tire axial direction is formed to be 90 to 115% of the ground contact width TW that is the distance in the tire axial direction between the ground contact ends Te and Te. In the present embodiment, the width of the first ply 9A and the width of the third ply 9C are smaller than the width of the second ply 9B. However, it is not limited to such an aspect.

  “Grounding end” Te is a grounding position on the outermost side in the tire axial direction of a grounding surface where a regular load is loaded on a normal tire and grounded to a plane with a camber angle of 0 °. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “maximum load capacity”, TRA is “TIRE LOAD” The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO, is a load corresponding to 88% of the load when the tire is for a passenger car.

  FIG. 4 shows an enlarged cross-sectional view of the reinforcing ply 9. As shown in FIG. 4, the reinforcing cord 11 of the present embodiment is a stranded wire in which a plurality (four in the present embodiment) of steel filaments f are twisted together. The reinforcing cord 11 is not limited to a stranded wire, and includes, for example, a single steel wire.

  The cord diameter d of the reinforcing cord 11 is preferably 30 to 60% of the arrangement pitch P of the reinforcing cord 11. When the cord diameter d of the reinforcing cord 11 exceeds 60%, the mass of the tire becomes large, and the rolling resistance performance may be deteriorated. When the cord diameter d is less than 30%, the hoop effect cannot be increased and the rolling resistance performance may be deteriorated. From such a viewpoint, the cord diameter d of the reinforcing cord 11 is more preferably 35 to 55% of the arrangement pitch P of the reinforcing cord 11. The cord diameter d is the diameter of the circumscribed circle of the aggregate of steel filaments f that form a stranded wire. The arrangement pitch P of the reinforcing cords 11 is desirably 0.75 to 2.0 mm, for example.

From the viewpoint of effectively exhibiting the above action, the cross-sectional area A of the reinforcing cord 11 is preferably 0.06 to 0.17 mm ² .

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, it cannot be overemphasized that this invention can be changed into various aspects, without being limited to said specific embodiment.

In order to confirm the effect of the present invention, a 175 / 65R15 pneumatic tire having the basic configuration shown in FIG. 1 and based on the specifications shown in Table 1 was tested. The main common specifications and test methods for each tire are as follows.
Grounding width TW: 126mm
Width Wa / TW in the tire axial direction of the first ply: 102%
Width Wa / TW in the tire axial direction of the second ply: 113%
Width Wa / TW in the tire axial direction of the third ply: 102%
Reinforcement cord arrangement pitch: 1.32 mm
The test method is as follows.

<Rolling resistance performance>
Using a drum type tire rolling resistance tester, the rolling resistance of each test tire was measured under the following conditions. The results are displayed as an index with the rolling resistance value of Comparative Example 1 as 100. The smaller the value, the better.
Rim: 5J
Internal pressure: 230 kpa
Load: 4.41kN
Speed: 80km / h

<Noise performance>
Each test tire was mounted on all wheels of a 1800cc passenger car under the following conditions. The in-vehicle noise was measured when the test driver drove a straight course on the asphalt road surface and a turning course with a radius of 110 m at a speed of 70 km / h. Noise data is evaluated by 1/3 octave analysis and evaluated by the rate of change in maximum noise in the 1000-1600Hz range during straight running and turning (maximum noise during turning-maximum noise during straight running) / maximum noise during turning) It was done. The results are displayed as a change rate (%). The smaller the value, the better.

<Tire mass>
The mass per tire was measured. The results are displayed as an index with the mass of Comparative Example 1 as 100. Smaller numbers are better.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that each performance of the tire of the example is improved in a balanced manner as compared with the comparative example. In addition, tests were performed using pneumatic tires of other sizes, and the same tendency as the test results was shown.

2 Tread portion 6 Carcass 7 Tread reinforcement layer 9 Reinforcement ply 9A First ply 9B Second ply 9C Third ply 11 Reinforcement cord

Claims (3)

A pneumatic tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a tread reinforcing layer disposed on the outer side in the tire radial direction of the carcass and inward of the tread portion,
The tread reinforcing layer is composed of three reinforcing plies in which an array of a plurality of reinforcing cords made of steel is covered with a topping rubber and overlapped inside and outside in the tire radial direction,
The reinforcing ply is arranged on the innermost side in the tire radial direction, and the reinforcing cord is an angle θ1 of 50-60 ° with respect to the tire equator;
The reinforcing cord is disposed on the outer side in the tire radial direction of the first ply, the reinforcing cord has an angle θ2 of 20 to 30 ° with respect to the tire equator, and the reinforcing cord of the first ply is in the same direction with respect to the tire equator A second ply,
The second ply is disposed on the outer side in the tire radial direction, and the reinforcing cord has an angle θ3 of 20 to 30 ° with respect to the tire equator, and is opposite to the tire equator with respect to the reinforcing cord of the second ply. And a third ply. The tread portion includes a tread rubber that forms a ground plane,
The pneumatic tire according to claim 1, wherein the loss tangent (tan δ) of the tread rubber is 0.10 to 0.18. 3. The pneumatic tire according to claim 1, wherein the reinforcing cord has a cross-sectional area of 0.060 to 0.17 mm ² and a cord diameter of 30 to 60% of an arrangement pitch of the reinforcing cord.

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